Long QT syndrome (LQTS) is a heart rhythm disorder due to problems with the heart’s electrical system that can cause sudden, fast uncontrollable, and irregular heartbeats (arrhythmia), which may lead to sudden death ¹, ², ³, ⁴, ⁵, ⁶, ⁷, ⁸, ⁹. However, not everyone who has long QT syndrome has dangerous heart rhythms. When they do occur, though, they can be fatal. Long QT syndrome (LQTS) affects the heart’s electrical process called repolarization, which is the recharging of the heart after each heartbeat. When your heart contracts, it sends out an electrical signal. The signal is produced by the flow of ions (potassium, sodium, and calcium) within your heart’s cells. The ions flow in and out of the heart’s cells through ion channels. Long QT syndrome occurs as the result of a defect in the ion channels, causing a delay in the time it takes for the electrical system to recharge (repolarize) after each heartbeat ¹. The prolonged QT interval can results from delayed inactivation of inward sodium (INa) or calcium (ICa) currents or a loss of function in outward potassium (slow delayed rectifier potassium channel [IKs], rapid delayed rectifier potassium channel [IKr], or inward rectifier potassium current [IK1]) currents, leading to an extended action potential duration in heart muscle cells ¹⁰, ¹¹. This prolonged repolarization (prolonged Q-T interval) can increase your risk for a type of ventricular arrhythmia called Torsades de Pointes, a polymorphic ventricular tachycardia. When Torsade de Pointes occurs, your heart cannot pump enough oxygen-rich blood to the rest of your body, especially your brain. Torsade de Pointes can also lead to ventricular fibrillation, a dangerous form of arrhythmia that causes rapid, uncoordinated contractions in the muscle fibers of the ventricles. With ventricular fibrillation, the heart cannot pump oxygen-rich blood to the rest of the body, which can lead to sudden cardiac death ¹².

If you have long QT syndrome, your heart takes longer than usual to recharge between beats. In long QT syndrome, the lower chambers of the heart (ventricles) take too long to contract and release. The gap of time needed to complete a cycle can be measured and compared to normal averages. When seen on an electrocardiogram (EKG or ECG), which records the electrical activity of your heart, this delay is called a prolonged (long) QT interval. Long QT syndrome is characterized by QT prolongation and T-wave abnormalities on the ECG that are associated with fast chaotic heartbeats, typically the ventricular tachycardia Torsades de Pointes ¹³. The Q-T interval is the section on the electrocardiogram (ECG) – that represents the time it takes for the electrical system to fire an impulse through the ventricles and then recharge. It is translated to the time it takes for the heart muscle to contract and then recover (see Figures 1 and 2).

There are 2 types of Long QT syndrome ¹⁴, ¹⁵, ¹⁶, ¹:

Congenital long QT syndrome. You’re born with this type of long QT syndrome. It’s estimated to affect about 1 in 2,000 people ¹⁷, ¹⁸. It’s caused by changes in DNA that are passed down through families. That means it is inherited. Congenital long QT syndrome has been shown to be caused by mutations in one of at least 15 different ion-channel genes ¹⁹: the KCNQ1 gene causing long QT syndrome type 1 (LQTS1); KCNH2 causing long QT syndrome type 2 (LQTS2); SCN5A causing long QT syndrome type 3 (LQTS3); ANK2 causing LQTS4; KCNE1 causing LQTS5; KCNE2 causing LQT6; KCNJ2 causing LQTS7; CACNA1c causing LQTS8; CAV3 causing LQTS9; SCN4B causing LQTS10; AKAB9 causing LQTS11; SNTA1 causing LQTS12; KCNJ5 causing LQTS13; CALM1 causing LQTS14; and CALM2 causing LQTS15. Mutations in KCNQ1, KCNH2, and SCN5A correlate to Long QT types 1-3 and account for the majority (80-90%) of genetically identifiable cases ²⁰, ²¹.
- There are 2 types of congenital long QT syndrome:
  - Romano-Ward syndrome. This more common type happens in people who get only a single gene change from one parent. Receiving a changed gene from one parent is known as an autosomal dominant inheritance pattern.
  - Jervell and Lange-Nielsen syndrome. This rare form of long QT syndrome usually happens very early in life and is severe. Children with this type of long QT syndrome also are deaf. In Jervell and Lange-Nielsen syndrome, children get the gene change from both parents. This is called an autosomal recessive inheritance pattern.
  - Congenital Long QT syndrome is autosomal in genetic transmission but shows a greater frequency of expression and a greater lengthening of the QT interval in women than in men. You should avoid competitive sports if you have congenital long QT syndrome ²². If you inherited Long QT syndrome from a parent, you should talk to a heart rhythm specialist before your start exercising. In congenital long QT syndrome, the mortality rate for untreated patients is 50% in 10 years, which can be reduced to 3-4% with therapeutic intervention. A systematic review of babies born with long QT syndrome from 83 studies comprising 265 newborns with postnatal confirmation of long QT syndrome found that a longer fetal QTc was more predictive of death than any other antenatal factor, and the mortality risk was significantly raised when the fetal QTc was longer than 600 ms ²³. Other factors that were highly predictive of death included the combination of ventricular tachycardia/Torsade de Pointes or functional 2:1 heart block and lack of a family history of long QT syndrome ²³. However, fetal heart rate and heart z-score did not predict death ²³.
Acquired long QT syndrome. Acquired long QT syndrome is caused by another health condition or medicine ²⁴, ²⁵. It usually can be reversed when the specific cause is found and treated.
- If a medicine causes acquired long QT syndrome, the disorder may be called drug-induced long QT syndrome. More than 100 medicines can cause prolonged QT intervals in otherwise healthy people. Medicines that can cause long QT syndrome include ²⁶:
  - Some antibiotics, such as erythromycin (Eryc, Erythrocin, others), azithromycin (Zithromax) and others.
  - Some antifungal medicines used to treat yeast infections.
  - Water pills, also called diuretics, that cause the body to remove too much potassium or other minerals.
  - Heart rhythm medicines called anti-arrhythmics, which can make the QT interval longer.
  - Some medicines used to treat mental health conditions such as anxiety and depression.
  - Some medicines used to treat upset stomach.
- Always tell your doctor about all the medicines you take, including those you buy without a prescription.
- Health conditions that can cause acquired long QT syndrome include ²⁶:
  - Body temperature below 95 degrees Fahrenheit (35 degrees Celsius), a condition called hypothermia.
  - Low calcium, also called hypocalcemia.
  - Low magnesium, also called hypomagnesemia.
  - Low potassium, also called hypokalemia.
  - A tumor of the adrenal gland that usually is not cancer, called pheochromocytoma.
  - Stroke or brain bleed.
  - Underactive thyroid, also called hypothyroidism.

Normally your heart circulates blood throughout your body during each heartbeat. Your heart’s chambers contract and relax to pump blood. These actions are controlled by electrical impulses that travel through your heart and cause it to beat. After each heartbeat, your heart’s electrical system recharges itself in preparation for the next heartbeat.

In long QT syndrome, your heart muscle takes longer than normal to recharge between beats. This electrical disturbance, which often can be seen on an electrocardiogram (ECG), is called a prolonged QT interval.

The electrical activity of the heart is produced by the flow of ions (electrically charged particles of sodium, calcium, potassium, and chloride) in and out of the cells of the heart. Tiny ion channels control this flow. In most cases, long QT syndrome delays the flow of potassium ions out of heart muscle cells. However, for a small number of people, the sodium channels are affected and too many sodium ions are allowed into the cells. This causes a delay in the electrical impulse known as ‘prolonged repolarization’. This shows up on an ECG as a lengthened QT interval, which is part of the heartbeat cycle.

The electrical activity that occurs between the Q and T waves is called the QT interval. This interval shows electrical activity in the heart’s lower chambers, the ventricles. The timing of the heart’s electrical activity is complex, and your body carefully controls it. Normally the QT interval is about a third of each heartbeat cycle. However, in people who have long QT syndrome, the QT interval lasts longer than normal.

A long QT interval can upset the careful timing of the heartbeat and trigger dangerous heart rhythms.

Long QT syndrome is a rare disorder. Experts think that about 1 in 7,000 people in the United States has long QT syndrome. But no one knows for sure, because long QT syndrome often goes undiagnosed ²⁷.

Long QT syndrome causes about 3,000 to 4,000 sudden deaths in children and young adults each year in the United States ²⁸. Unexplained sudden deaths in children are rare. When they do occur, long QT syndrome often is the cause.

Inherited long QT syndrome usually is first detected during childhood or young adulthood. Half of all people who have long QT syndrome have their first abnormal heart rhythm by the time they’re 12 years old, and 90 percent by the time they’re 40 years old. The condition rarely is diagnosed after age 40.

In boys who have long QT syndrome, the QT interval (which can be seen on an EKG test) often returns toward normal after puberty. If this happens, the risk of long QT syndrome symptoms and complications goes down.

Long QT syndrome is more common in women than men. Women who have long QT syndrome are more likely to faint or die suddenly from the disorder during menstruation and shortly after giving birth.

Children who are born deaf also are at increased risk for long QT syndrome. This is because the same genetic problem that affects hearing also affects the function of ion channels in the heart.

The following techniques are commonly used to diagnose long QT syndrome:

A standard electrocardiogram (EKG or ECG) is the best test for diagnosing LQTS. The EKG machine records your heart’s electrical activity in waveforms, which can show a prolonged Q-T interval.
An exercise ECG, also known as a stress test, can show an abnormal Q-T interval that may otherwise be normal during a resting EKG.
Holter monitoring gets a continuous reading of your heart rate and rhythm over a 24-hour period (or longer). Doctors can then look at the recording to see if it shows a prolonged Q-T interval.

Some people with long QT syndrome may not have a prolonged Q-T interval all the time, so the disorder is sometimes overlooked during a routine physical exam. This is why it is important to know your family’s medical history. In any family where there are repeated episodes of fainting or a history of sudden death, long QT syndrome may be the cause.

As Long QT syndrome is sometimes inherited, you may also be referred for genetic testing to test for any faulty genes that are linked with the condition. Your immediate family members (such as your parents, siblings and your children) may also be invited for an assessment.

Treatment for long QT syndrome includes lifestyle changes and medicines to prevent dangerous heartbeats or surgery. Beta blocker medication is the primary treatment for long QT syndrome. Beta blockers do not cure long QT syndrome, but they have been shown to reduce or prevent the symptoms. Beta blockers, such as Propranolol or Nadolol, help control irregular heartbeats and slow your heart rate to make the prolonged QT interval less likely.

Sodium channel blockers can be useful as additional drug therapy for patients with a QTc interval >500 ms (normal QTc interval is 440 ms).

If you’re at risk of a life-threatening arrhythmia and you need more than just medicine to manage this risk, you may need a pacemaker or an implantable cardioverter defibrillator (ICD) fitted.Pacemaker or an implantable cardioverter defibrillator (ICD) are fitted to help control the rhythm and rate of your heart or help correct life-threatening heart rhythms.Implantable cardioverter-defibrillators (ICDs) and/or left cardiac sympathetic denervation (LCSD) surgery are for those with beta-blocker-resistant symptoms, inability to take beta blockers, and/or history of cardiac arrest.

Others with long QT syndrome may need to be prescribed potassium supplements from their doctor. They might also suggest you increase your uptake of potassium-rich foods like bananas, vegetables and pulses. If you’re taking any new medicine or supplements, always check with your pharmacist that what you’re taking is okay with long QT syndrome.

If you are active in competitive sports, talk to your heart doctor about how this may affect your long QT syndrome. Often, once treatment in started, patients with long QT syndrome can participate in recreational sports or other activities in moderation. If you have episodes of fainting while you exercise, you may want to think about exercising with a friend or a family member who can call for help if you need it.

Do You Need to be Screened for Long QT Syndrome?

Long QT Syndrome is a medical condition that can be passed on from generation to generation. It is important for you to be screened for this condition if you have a first-degree relative with long QT Syndrome. First-degree relatives are your parents, siblings and children. All first-line relatives (brothers, sisters, parents and children) should have electrocardiogram (EKG) testing. Any other family members who have a history of seizures or fainting should also undergo testing.

The first step is to tell your doctor that you have a family history of Long QT Syndrome. He or she may want to do diagnostic tests to check your heart. If these tests are positive, you should be seen by a cardiologist who is familiar with Long QT Syndrome.

Can I live a normal life with long QT syndrome?

There are very few things you need to change if you have long QT syndrome. However, you should be aware that:

Competitive sports are prohibited in patients with congenital long QT syndrome ²².
Prolonged (longer than a day) or severe episodes of vomiting or diarrhea can affect your sodium and potassium levels. You should discuss this situation with your doctor who may wish to prescribe oral rehydration supplements. These supplements can help to replenish sodium and potassium levels but should be used under medical supervision.
Over-the-counter medicines and supplements should also first be discussed with your doctor. Some of these may induce symptoms or react with medicines you may be taking to help reduce your risk of abnormal heart rhythms.
You should always inform medical staff that you have long QT syndrome when you speak to them.

What is the QT interval?

An ECG measures electrical impulses as five distinct waves (Figure 1). Doctors label these five waves using the letters P, Q, R, S and T. The waves labeled Q through T show electrical activity in your heart’s lower chambers (ventricles). The QT interval is a time interval on the ECG.

A typical ECG tracing is shown in Figure 1 below. The different waves that comprise the ECG represent the sequence of depolarization and repolarization of the atria and ventricles. The ECG is recorded at a speed of 25 mm/second (5 large squares/second or 5 dark red boxes), and the voltages are calibrated so that 1 mV = 10 mm (2 large squares) in the vertical axis. Therefore, each large dark red 5 mm square represents 0.2 sec (20 msec [millisecond]) and each small 1 mm square represents 0.04 sec (40 msec [millisecond]) in time and 0.10 mV in voltage. Because the recording speed is standardized, you can calculate the heart rate from the intervals between different waves. One method is to divide 1500 by the number of small squares between two R waves. For example, the rate between beats 1 and 2 in Figure 4 below is 1500/22, which equals 68 beats/min. Alternatively, you can divide 300 by the number of large squares, which is 300/4.4 (68 beats/min). Another method, which gives a rough approximation, is the “count off” method. Count the number of large squares between R waves with the following rates: 300 – 150 – 100 – 75 – 60. For example, if there are three large boxes between R waves, then the rate is 100 beats/min. You must extrapolate, however, between boxes. Atrial rate can be determined like the ventricular rate, but using the P waves. Remember, if the heart is in sinus rhythm and there is a one-to-one correspondence between P waves and QRS completes, then the atrial rate will be the same as the ventricular rate. The rate is normal if the interval lies between 5 and 3 large squares (60 – 100 beats/min). Intervals less than 3 large squares or greater than 5 large squares represent tachycardia or bradycardia, respectively.

The space between the start of the Q wave and the end of the T wave (QT interval) corresponds to the time it takes for your heart to contract and then refill with blood before beginning the next contraction. The QT interval represents the time from the electrical stimulation (depolarization) of the heart’s pumping chambers (ventricles), to the end of the recharging of the electrical system (repolarization) and therefore roughly estimates the duration of an average ventricular action potential ²⁹. The interval between the letters Q and T defines the action of the ventricles. The QT interval is measured in milliseconds (msec) and closely approximates the time from the beginning of the heart ventricles’ contraction until the end of relaxation.

The QT interval interval can range from 0.20 to 0.40 seconds (200 to 400 msec), depending upon your heart rate. At high heart rates, ventricular action potentials shorten in duration, which decreases the QT interval ²⁹. Long QT syndrome means that time period is too long, even if by fractions of a second. Because prolonged QT intervals can be diagnostic for susceptibility to certain types of heart arrhythmias, it is important to determine if a QT interval is excessively long. The QT interval is often expressed as a corrected QT (QTc) by taking the QT interval and dividing it by the square root of the R-R interval (interval between ventricular depolarizations) using Bazett formula: QTc = QT / √ RR ⁷. Corrected QT (QTc) allows an assessment of the QT interval that is independent of the heart rate. Normal corrected QTc intervals are 0.44 seconds or less (<440 msec). QTc is prolonged if it is greater than 440 ms in men or greater than 460 ms in women ³⁰. A QTc greater than 500 is associated with an increased risk of Torsade de Pointes. While several equations exist to help correct heart rate variation, the Bazett formula (QTC = QT / √ RR) is the most commonly used. Though the Bazett formula seems relatively accurate in heart rates between 60 to 100 beats/min, it tends to overcorrect with higher heart rates and undercorrect with lower heart rates.

An occasional prolonged QT interval can be precipitated by everyday circumstances, including:

When startled by a noise
Physical activity or exercise
Intense emotion (such as fright, anger or pain)

In these instances, the heartbeat usually regains its normal contraction rhythm quickly.

Long QT syndrome results from abnormalities in the heart’s electrical recharging system. However, the heart’s structure is normal. Abnormalities in your heart’s electrical system might be inherited. Or, they may be acquired due to an underlying medical condition or a medication.

Figure 1. Normal ECG pattern

Footnotes:

P wave represents the wave of depolarization that spreads from the SA node throughout the atria and is usually 0.08 to 0.10 seconds (80-100 ms) in duration. There is no distinctly visible wave representing atrial repolarization in the ECG because it occurs during ventricular depolarization. Because the wave of atrial repolarization is relatively small in amplitude (i.e., has low voltage), it is masked by the much larger ventricular-generated QRS complex.
QRS complex represents ventricular depolarization. Ventricular rate can be calculated by determining the time interval between QRS complexes. The duration of the QRS complex is normally 0.06 to 0.10 seconds.
ST segment is the isoelectric period following the QRS and ending at the beginning of the T wave. This represents the period at which both ventricles are completely depolarized. This segment roughly corresponds to the plateau phase of the ventricular action potentials. The ST segment is crucial in the diagnosis of ventricular ischemia or hypoxia because under those conditions, the ST segment can become either depressed or elevated.
T wave represents ventricular repolarization. The T wave exhibits a positive deflection. This is because the last cells to depolarize in the ventricles are the first to repolarize. This occurs because the last cells to depolarize are in the subepicardial region of the ventricles, and these cells have shorter action potentials than found in the subendocardial regions of the ventricular wall. Therefore, although the depolarization of the subepicardial cells occurs after subendocardial depolarization, the subepicardial cells undergo phase 3 repolarization before the subendocardial cells. Therefore, repolarization waves generally are oriented opposite of depolarization waves and repolarization waves moving away from a positive recording electrode produce a positive voltage.
QT interval represents the time for both ventricular depolarization and repolarization to occur, and therefore roughly estimates the duration of an average ventricular action potential. This interval can range from 0.20 to 0.40 seconds, depending upon heart rate. At high heart rates, ventricular action potentials shorten in duration, which decreases the QT interval.

Figure 2. Long QT syndrome

Figure 3. The heart’s electrical system

Figure 4. Normal ECG

Long QT syndrome causes

Long Q-T syndrome can be acquired or congenital ¹:

Acquired long QT syndrome is caused by another health condition or medicine ²⁴, ²⁵. Sensitivity to these medications may be related to genetic causes. It usually can be reversed when the specific cause is found and treated.
Congenital long QT syndrome is usually inherited caused by changes in DNA that are passed down through families. Congenital long QT syndrome is estimated to affect about 1 in 2,000 people ¹⁷, ¹⁸. Congenital long QT syndrome is caused by an abnormality in the gene code for the ion channels. The abnormality of the ion channels slows the recovery phase of the heartbeat. Congenital long QT syndrome has been shown to be caused by mutations in one of at least 15 different ion-channel genes: the KCNQ1 gene causing long QT syndrome type 1 (LQTS1); KCNH2 causing long QT syndrome type 2 (LQTS2); SCN5A causing long QT syndrome type 3 (LQTS3); ANK2 causing LQTS4; KCNE1 causing LQTS5; KCNE2 causing LQT6; KCNJ2 causing LQTS7; CACNA1c causing LQTS8; CAV3 causing LQTS9; SCN4B causing LQTS10; AKAB9 causing LQTS11; SNTA1 causing LQTS12; KCNJ5 causing LQTS13; CALM1 causing LQTS14; and CALM2 causing LQTS15 ¹⁹. Mutations in KCNQ1, KCNH2, and SCN5A correlate to Long QT types 1-3 and account for the majority (80-90%) of genetically identifiable cases ²⁰, ²¹. Forms of inherited long QT syndrome include:
- Recent Classifications – Multiple ion channel abnormalities have been discovered. The most common ones include LQTS1, LQTS2, LQTS3, LQTS4, LQTS5; these are classified by the type of channel which causes the long QT syndrome. The type of long QT syndrome classification is related to the risk of future cardiac events, those with LQTS3 having the highest risk of life-threatening arrhythmias.
- Jervell and Lange-Nielsen Syndrome (autosomal recessive inheritance pattern) – Both parents are carriers of the abnormal gene, but they may not manifest long QT syndrome. Each child has a 25-percent chance of inheriting long QT syndrome. This syndrome is associated with deafness at birth and is extremely rare, as there is a small chance that both parents would carry the long QT syndrome gene.
- Romano-Ward Syndrome (autosomal dominant inheritance pattern) – In 1963 and 1964, Romano ³¹ and Ward ³² independently described families with a prolonged QT interval and syncope without deafness, which became known as Romano-Ward syndrome. Romano-Ward syndrome is an autosomal dominant form of long QT syndrome and is more common than Jervell and Lange-Nielsen Syndrome. Studies in the 1970s and 1980s further characterized the clinical features and familial nature of LQTS, leading to the recognition of its genetic heterogeneity ³³. One parent has long QT syndrome and the other parent usually does not. Each child has a 50-percent chance of inheriting the abnormal gene. In this syndrome, hearing is normal; however the likelihood that children in this family would have long QT syndrome is greater. The gene may be present in all the couple’s children, some of them or none at all.
- Timothy Syndrome. Timothy syndrome is a rare, autosomal dominant disorder caused by mutations in the CACNA1C gene that affects other parts of your body as well as your heart including prolonged QT interval (QT prolongation), heart arrhythmias, structural heart defects, syndactyly (webbed fingers or toes), and neurological problems like autism spectrum disorders ³⁴. Mutations in the CACNA1C gene that cause Timothy syndrome change the structure of CaV1.2 channels that transports positively charged calcium atoms (calcium ions) into cardiac cells (cardiomyocytes) and nerve cells (neurons) in the brain. Calcium ions are important for many cellular functions, including regulating the electrical activity of cells, cell-to-cell communication, the tensing of muscle fibers (muscle contraction), and the regulation of certain genes, particularly those involved in the development of the brain and bones before birth. The CACNA1C gene changes lead to altered CaV1.2 channels that stay open much longer than usual, which allows calcium ions to continue flowing into cells abnormally. The resulting overload of calcium ions within heart muscle cells changes the way the heart beats and can cause abnormal heart muscle contractions and arrhythmia. It is thought that the altered channels and flow of calcium ions also impair regulation of certain genes, resulting in the facial, dental, and neurological abnormalities in Timothy syndrome. Other variants in the CACNA1C gene can cause isolated features of Timothy syndrome without the other associated health problems of the condition. For example, some people with CACNA1C gene variants may have only long QT syndrome or only neurodevelopmental disorders.

Those at risk for long QT syndrome include:

Children who are deaf at birth
Children and young adults who have unexplained sudden death or syncope in family members
Blood relatives of family members with long QT syndrome
Those with long QT syndrome taking medications that can further prolong the QT intervals.

Congenital long QT syndrome

At least 17 genes associated with long QT syndrome have been found so far, and hundreds of mutations within these genes have been identified. Mutations in three of these genes account for about 75 percent of long QT syndrome cases, while mutations in the other minor genes contribute a small percent of long QT syndrome cases.

About 20 to 25 percent of people who definitely have congenital long QT syndrome have a negative genetic test result. On the other hand, among families with genetically established long QT syndrome, between 10 percent and 37 percent of the relatives with a positive long QT syndrome genetic test have a normal QT interval.

Doctors have described two forms of inherited long QT syndrome:

Romano-Ward syndrome. This more common form occurs in people who inherit only a single genetic variant from one parent.
Jervell and Lange-Nielsen syndrome. This rare form usually occurs earlier and is more severe. In this syndrome, children inherit genetic variants from both parents. They have long QT syndrome and also are born deaf.

Additionally, scientists have been investigating a possible link between sudden infant death syndrome (SIDS) and long QT syndrome and have discovered that approximately five to 10 percent of babies affected by SIDS (sudden infant death syndrome) had a genetic defect or mutation for long QT syndrome.

Acquired long QT syndrome

Acquired long QT syndrome can be caused by certain medications, electrolyte abnormalities such as low body potassium (hypokalemia), low blood calcium (hypocalcemia), low blood magnesium (hypomagnesemia) or medical conditions ²⁴, ²⁵. More than 100 medications — many of them common — can lengthen the QT interval in otherwise healthy people and cause a form of acquired long QT syndrome known as drug-induced long QT syndrome.

Medications

Various medications across multiple therapeutic classes have been linked to QT prolongation and an increased risk of Torsade de Pointes.

Medications that can lengthen the QT interval and upset heart rhythm include:

Certain antibiotics
Certain antidepressant and antipsychotic medications
Some antihistamines
Diuretics
Medications used to maintain normal heart rhythms (antiarrhythmic medications)
Cholesterol-lowering medicines and some diabetes medicines
Some anti-nausea medications

People who develop drug-induced long QT syndrome might also have some subtle genetic defects in their hearts. These defects make them more likely to have disruptions in their heart rhythm from certain medications.

Some people who have medication-induced long QT syndrome also may have an inherited form of the disorder. They may not have symptoms unless they take medicines that lengthen the QT interval or lower potassium levels in the blood. When long QT syndrome doesn’t cause symptoms, it’s called silent long QT syndrome.

Electrolyte imbalances

Severe diarrhea or vomiting that causes a major loss of potassium or sodium ions from the bloodstream may cause acquired long QT syndrome. The long QT syndrome lasts until these ion levels return to normal.

Hypokalemia, defined as serum potassium below 3.5 mEq/L, can lead to prolonged repolarization and increased risk of Torsade de Pointes ³⁵. Low extracellular potassium reduces the conductance of the inward rectifier potassium current [I_K1], essential for maintaining resting membrane potential and terminal repolarization of cardiac myocytes. It also enhances Na+/Ca2+ exchanger activity, increasing intracellular calcium levels and prolonging action potential duration ³⁶. The eating disorders anorexia nervosa and bulimia and some thyroid disorders may cause a drop in potassium ion levels in the blood, causing long QT syndrome.
Hypomagnesemia, defined as serum magnesium below 1.7 mg/dL, is another important risk factor for acquired long QT syndrome ³⁷. Magnesium is a critical cofactor for various ion channels and transporters involved in cardiac repolarization. Low magnesium levels can impair the function of inward rectifier potassium current [I_K1], slow delayed rectifier potassium channel [I_Ks], and Na+/K+-ATPase, leading to prolonged action potential duration and increased arrhythmia risk ³⁸.
Hypocalcemia has also been associated with QT prolongation, although the mechanisms are less well understood ³⁹. Calcium plays a crucial role in cardiac electrophysiology, and low extracellular calcium levels can alter the function of various ion channels and transporters involved in repolarization.

Identifying and correcting electrolyte imbalances is essential in managing patients with acquired long QT syndrome or those at risk. Monitoring serum electrolyte levels, particularly in patients treated with QT-prolonging medications or those with predisposing conditions, can help prevent life-threatening arrhythmias ⁴⁰.

Other medical conditions

Several medical conditions can contribute to the development of acquired long QT syndrome by directly affecting heart repolarization or indirectly influencing the risk of QT prolongation through altered pharmacokinetics or pharmacodynamics of QT-prolonging medications.

Heart conditions
- Bradycardia: Slow heart rates can prolong the QT interval and increase Torsade de Pointes risk ⁴¹, ⁴²
- Heart failure: Associated with an increased risk of QT prolongation and Torsade de Pointes because of altered ion channel expression, neurohumoral activation, and electrolyte disturbances ⁴³
- Myocardial ischemia and infarction: Can lead to QT prolongation by altering ion channel function and increasing repolarization dispersion ⁴⁴
Endocrine disorders
- Hypothyroidism (underactive thyroid): Can prolong the QT interval by altering cardiac ion channel expression and function ⁴⁵
- Pheochromocytoma: Catecholamine excess can lead to QT prolongation and increased ventricular arrhythmia risk ⁴⁶
Neurological conditions
- Subarachnoid hemorrhage (SAH): Increased risk of QT prolongation and Torsade de Pointes because of autonomic dysfunction, electrolyte disturbances, and QT-prolonging medications ⁴⁷
- Stroke: Acute stroke, particularly involving the insular cortex, can lead to QT prolongation and increased ventricular arrhythmia risk ⁴⁸
Liver disease: Hepatic dysfunction can alter QT-prolonging drug metabolism, leading to increased plasma levels and higher acquired long QT syndrome risk ⁴⁹
Kidney disease: Chronic kidney disease and end-stage renal disease are associated with increased QT prolongation and Torsade de Pointes risk ⁵⁰
Eating disorders: Anorexia nervosa and bulimia nervosa can lead to QT prolongation and increased sudden cardiac death risk ⁵¹
Autoimmune disorders: Systemic lupus erythematosus (SLE) and other autoimmune disorders have been associated with QT prolongation ⁵², ⁵³, ⁵⁴

Recognizing and managing these underlying medical conditions is crucial for minimizing acquired long QT syndrome risk. Patients with these conditions should be closely monitored for QT prolongation, especially when treated with QT-prolonging medications, and appropriate interventions should be implemented to correct modifiable risk factors.

Risk factors for long QT syndrome

People who may have a higher risk of inherited or acquired long QT syndrome may include:

Children, teenagers and young adults with unexplained fainting, unexplained near drownings or other accidents, unexplained seizures, or a history of cardiac arrest
Family members of children, teenagers and young adults with unexplained fainting, unexplained near drownings or other accidents, unexplained seizures, or a history of cardiac arrest
First-degree relatives of people with known long QT syndrome
People taking medications known to cause prolonged QT intervals
People with low body potassium (hypokalemia), low blood calcium (hypocalcemia), low blood magnesium (hypomagnesemia) levels — such as those with the eating disorder anorexia nervosa.

Inherited long QT syndrome often goes undiagnosed or is misdiagnosed as a seizure disorder, such as epilepsy. However, long QT syndrome might be responsible for some otherwise unexplained deaths in children and young adults. For example, an unexplained drowning of a young person might be the first clue to inherited long QT syndrome in a family.

You’re at risk of having long QT syndrome if anyone in your family has ever had it. Unexplained fainting or seizures, drowning or near drowning, and unexplained sudden death are all possible signs of long QT syndrome.
You’re also at risk for long QT syndrome if you take medicines that make the QT interval longer. Your doctor can tell you whether your prescription or over-the-counter medicines might do this.
You also may develop long QT syndrome if you have excessive vomiting or diarrhea or other conditions that cause low blood levels of potassium or sodium. These conditions include the eating disorders anorexia nervosa and bulimia, as well as some thyroid disorders.

Long QT syndrome prevention

If you have inherited long QT syndrome, be careful about which medications you take. Some medications — including certain appetite suppressants, decongestants and common antibiotics — might trigger dangerous heart rhythms. Ask your doctor what you can and can’t take safely. Illegal drugs, such as cocaine and amphetamines, pose a serious risk for people with long QT syndrome.

In addition, seek medical treatment right away for illnesses that could result in low blood-potassium levels, especially if you have a lot of vomiting and diarrhea. Such illnesses could trigger an episode of long QT syndrome. Your doctor might advise you not to take some drugs, such as diuretics, that lower blood-potassium levels.

Some people — especially older adults with long QT syndrome who haven’t had signs or symptoms of the condition in decades — may not need any treatment other than preventive measures.

If Long QT syndrome runs in your family, your doctor can test your family members to see if they have it. With proper treatment, you can manage and prevent the dangerous heartbeats that can lead to Long QT syndrome complications.

Regular health checkups and good communication with your doctor also may help prevent causes of some types of acquired long QT syndrome. It’s especially important not to take medicines that can affect the heart rhythm and cause a prolonged QT interval.

Long QT syndrome drugs to avoid

There are many medications that can prolong the QT interval. Those with long QT syndrome may be more prone to the effects of these medications. If you have long QT syndrome, you should:

NOT take over-the-counter medications (except for plain aspirin or acetaminophen) without first talking to your health care provider.
Tell all your health care providers you have long QT syndrome, as there are many drugs you cannot take.
Talk to your doctor before taking any medications prescribed for other medical conditions. The following types of medications may affect you if you have long QT syndrome:
- Antihistamines
- Antidepressants, mental illness medications
- Heart medications
- Antibiotics, antifungals, antivirals
- Intestinal medications
- Anticonvulsants
- Diuretics
- Antihypertensives
- Migraine medications
- Cholesterol lowering medications

Table 1. Long QT syndrome drugs to avoid

Generic Name	Brand Names (Partial List)	Drug Class	Therapeutic Use
Abarelix (Only on Non US Market)	Plenaxis	GnRH Antagonist	Cancer (prostate)
Aclarubicin (Only on Non US Market)	Aclacin, Aclacinomycine, Aclacinon, Aclaplastin, Jaclacin	Anti-cancer	Cancer
Albuterol (salbutamol)	Proventil, Ventolin, Ventolin-HFA, Accuneb, Combivent, Vospire-ER, ProAir HFA, Duoneb	Bronchodilator	Asthma
Alfuzosin	Uroxatral	Alpha-1 adrenergic blocker	Benign prostatic hyperplasia
Amantadine	Symmetrel, Symadine	Antiviral	Viral infection (Influenza), Parkinson’s disease
Amiodarone	Cordarone, Pacerone, Nexterone	Antiarrhythmic	Arrhythmia
Amisulpride (Only on Non US Market)	Solian, Supitac, Soltus, Amitrex, Amazeo	Antipsychotic, atypical	Schizophrenia
Amitriptyline	Elavil (Discontinued 6/13), Tryptomer, Tryptizol, Laroxyl, Saroten, Sarotex Lentizol, Endep	Antidepressant, Tricyclic	Depression
Amphetamine (Amfetamine)	Adderal-XR, Dexedrine, Dextroamp	CNS stimulant	ADHD
Amphotericin B	Fungilin, Fungizone, Abelcet, AmBisome, Fungisome, Amphocil, Amphotec	Antifungal	Fungal infection
Amsacrine (acridinyl anisidide) (Only on Non US Market)	Amsidine	Antineoplastic Agent	Acute Lymphoblastic Leukemia
Anagrelide	Agrylin, Xagrid	Phosphodiesterase 3 inhibitor	Thrombocythemia
Apalutamide	Erleada	Nonsteroidal antiandrogen	Cancer (prostate)
Apomorphine	Apokyn, Ixense, Spontane, Uprima	Dopamine agonist	Parkinson’s disease
Arformoterol	Brovana	Bronchodilator	Asthma, COPD
Aripiprazole	Abilify, Aripiprex	Antipsychotic, atypical	Schizophrenia, depression (adjunct)
Arsenic trioxide	Trisenox	Anti-cancer	Cancer (leukemia)
Artenimol+piperaquine (Only on Non US Market)	Eurartesim	Antimalarial	Malaria
Asenapine	Saphris, Sycrest	Antipsychotic, atypical	Schizophrenia
Astemizole (Removed from Market)	Hismanal	Antihistamine	Allergic rhinitis
Atazanavir	Reyataz, Evotaz	Antiviral	Viral infection (HIV/AIDS)
Atomoxetine	Strattera	CNS stimulant	ADHD
Azithromycin	Zithromax, Zmax	Antibiotic	Bacterial infection
Bedaquiline	Sirturo	Antibiotic	Tuberculosis, Multi-drug resistant
Bendamustine	Treanda, Treakisym, Ribomustin, Levact	Anti-cancer	Cancer (Leukemia, lymphoma)
Bendroflumethiazide or bendrofluazide	Aprinox, Corzide	Diuretic, thiazide	Hypertension, diuresis
Benperidol (Only on Non US Market)	Anquil, Glianimon	Antipsychotic	Schizophrenia
Bepridil (Removed from Market)	Vascor	Antianginal	Angina Pectoris (heart pain)
Betrixaban	Bevyxxa	Anticoagulant	Anticoagulant
Bortezomib	Velcade, Bortecad	Proteasome inhibitor	Cancer (multiple myeloma,lymphoma)
Bosutinib	Bosulif	Anti-cancer	Cancer (leukemia)
Buprenorphine	Butrans, Belbuca, Bunavail, Buprenex, Suboxone, Zubsolv	Opiate	Narcotic addiction and pain
Cabozantinib	Cometriq	Anti-cancer	Cancer (renal cell)
Capecitabine	Xeloda	Anti-cancer	Cancer (GI, Breast)
Ceritinib	Zykadia	Anti-cancer	Cancer (Lung)
Chloral hydrate	Aquachloral, Novo-Chlorhydrate, Somnos, Noctec, Somnote	Sedative	Sedation, insomnia
Chloroquine	Aralen	Antimalarial	Malaria
Chlorpromazine	Thorazine, Largactil, Megaphen	Antipsychotic / Antiemetic	Schizophrenia, nausea, many others
Cilostazol	Pletal	Phosphodiesterase 3 inhibitor	Intermittent claudication
Cimetidine	Tagamet and others	Antacid	Gastric hyperacidity, GERD
Ciprofloxacin	Cipro, Cipro-XR, Neofloxin	Antibiotic	Bacterial infection
Cisapride (Removed from Market)	Propulsid	GI stimulant	Increase GI motility
Citalopram	Celexa, Cipramil	Antidepressant, SSRI	Depression
Clarithromycin	Biaxin, Prevpac	Antibiotic	Bacterial infection
Clofazimine (Only on Non US Market)	Lamprene	Antibiotic	Leprosy
Clomipramine	Anafranil	Antidepressant, Tricyclic	Depression
Clotiapine (Only on Non US Market)	Entumine	Antipsychotic, atypical	Psychosis
Clozapine	Clozaril, Fazaclo, Versacloz	Antipsychotic, atypical	Schizophrenia
Cocaine	Cocaine	Local anesthetic	Anesthesia (topical)
Crizotinib	Xalkori	Anti-cancer	Cancer (Non-small cell lung cancer, metastatic)
Cyamemazine (cyamepromazine) (Only on Non US Market)	Tercian	Antipsychotic	Schizophrenia, sedation
Dabrafenib	Tafinlar	Anti-cancer	Cancer (melanoma)
Dasatinib	Sprycel	Anti-cancer	Cancer (leukemia)
Degarelix	Firmagon, Ferring	Gonadotropin Releasing Hormone Agonist/antagonist	Cancer (prostate)
Delamanid (Only on Non US Market)	Deltyba	Antibiotic	Tuberculosis, Multi-drug resistant
Desipramine	Pertofrane, Norpramine	Antidepressant, Tricyclic	Depression
Deutetrabenazine	Austedo	Vesicular monamine transporter 2 inhibitor	Chorea (Huntington’s disease)
Dexmedetomidine	Precedex, Dexdor, Dexdomitor	Sedative	Sedation
Dexmethylphenidate	Focalin, Focalin-XR, Attenade	CNS stimulant	ADHD
Dextroamphetamine (Dexamfetamine)	Dexedrine, dexamphetamine, dexamfetamine, (S)-(+)-amphetamine, Dextrostat, Dexedrine, Metamina, Attentin, Zenzedi, Procentra, Amfexa	CNS stimulant	ADHD, obesity
Diphenhydramine	Benadryl, Nytol, Unisom, Sominex, Dimedrol, Daedalon	Antihistamine	Allergic rhinitis, insomnia
Disopyramide	Norpace	Antiarrhythmic	Arrhythmia
Dobutamine	Dobutrex	Inotrope	Heart failure, shock (low blood pressure)
Dofetilide	Tikosyn	Antiarrhythmic	Arrhythmia
Dolasetron	Anzemet	Antiemetic	Nausea, vomiting
Domperidone (Only on Non US Market)	Motilium, Motillium, Motinorm Costi, Nomit	Antiemetic	Nausea, vomiting
Donepezil	Aricept	Cholinesterase inhibitor	Dementia (Alzheimer’s Disease)
Dopamine	Intropine	Inotrope	Heart failure, shock (low blood pressure)
Doxepin	Sinequan, Silenor, Aponal, Adapine, Doxal, Deptran, Sinquan	Antidepressant, Tricyclic	Depression
Dronedarone	Multaq	Antiarrhythmic	Arrhythmia
Droperidol	Inapsine, Droleptan, Dridol, Xomolix	Antipsychotic / Antiemetic	Anesthesia (adjunct), nausea
Droxidopa	Northera	Adrenergic pro-drug	Hypotension (Neurogenic orthostatic)
Efavirenz	Sustiva and others	Antiviral	HIV/AIDS
Eliglustat	Cerdelga	Glucosylceramide synthase inhibitor	Gaucher’s disease
Eperisone (Only on Non US Market)	Myonal, Epry	Antispasmodic	Spasticity
Ephedrine	Rynatuss, Broncholate	Bronchodilator, decongestant	Allergic reaction, allergic rhinitis, asthma
Epinephrine (adrenaline)	Primatene, Bronkaid	Catecholamine, vasoconstrictor	Allergic reaction, anaphylaxis, cardiac arrest
Epirubicin	Ellence, Pharmorubicin, Epirubicin Ebewe	Anti-cancer	Cancer
Eribulin mesylate	Halaven	Anti-cancer	Cancer (breast, metastatic)
Erythromycin	E.E.S., Robimycin, EMycin, Erymax, Ery-Tab, Eryc Ranbaxy, Erypar, Eryped, Erythrocin Stearate Filmtab, Erythrocot, E-Base, Erythroped, Ilosone, MY-E, Pediamycin, Abboticin, Abboticin-ES, Erycin, PCE Dispertab, Stiemycine, Acnasol, Tiloryth	Antibiotic	Bacterial infection, increase GI motility
Escitalopram	Cipralex, Lexapro, Nexito, Anxiset-E (India), Exodus (Brazil), Esto (Israel), Seroplex, Elicea, Lexamil, Lexam, Entact (Greece), Losita (Bangladesh), Reposil (Chile), Animaxen (Colombia), Esitalo (Australia), Lexamil (South Africa)	Antidepressant, SSRI	Depression (major), anxiety disorders
Esomeprazole	Nexium, Nexum and others	Proton Pump Inhibitor	Gastric hyperacidity, GERD
Ezogabine (Retigabine)	Potiga, Trobalt	Anticonvulsant	Seizures, Partial
Famotidine	Pepcid, Fluxid, Quamatel	H2-receptor antagonist	Gastric hyperacidity, GERD
Felbamate	Felbatol	Anticonvulsant	Seizures
Fenfluramine (Removed from Market)	Pondimin, Ponderax, Adafax	Appetite suppressant	Obesity
Fingolimod	Gilenya	Sphingosine phospate receptor modulator	Multiple Sclerosis
Flecainide	Tambocor, Almarytm, Apocard, Ecrinal, Flécaine	Antiarrhythmic	Arrhythmia
Fluconazole	Diflucan, Trican	Antifungal	Fungal infection
Fluorouracil (5-FU)	Adrucil, Carac, Efudex, Efudix, others	Anti-cancer	Cancer
Fluoxetine	Prozac, Sarafem, Fontex	Antidepressant, SSRI	Depression
Flupentixol (Only on Non US Market)	Depixol, Fluanxol	Antipsychotic	Schizophrenia
Fluvoxamine	Faverin, Fevarin, Floxyfral, Dumyrox and Luvox	Selective Serotonin Reuptake Inhibitor	Depression, Obsessive Compulsive Disorder
Formoterol	Foradil, Foradile, Oxeze, Oxis, Atock, Atimos, Atimos Modulite, Perforomist, Dulera, Symbicort, Vannair, Quikhale FB	Bronchodilator	Asthma
Furosemide (frusemide)	Lasix, Fusid, Frumex	Diuretic	Hypertension, diuresis
Galantamine	Reminyl, Nivalin, Razadyne-ER, Lycoremine	Cholinesterase inhibitor	Dementia (Alzheimer’s Disease)
Garenoxacin (Only on Non US Market)	Geninax	Antibiotic	Bacterial infection
Gatifloxacin (Removed from Market)	Tequin	Antibiotic	Bacterial infection
Gemifloxacin	Factive	Antibiotic	Bacterial infection
Granisetron	Kytril, Sancuso, Granisol	Antiemetic	Nausea, vomiting
Grepafloxacin (Removed from Market)	Raxar	Antibiotic	Bacterial infection
Halofantrine (Only on Non US Market)	Halfan	Antimalarial	Malaria
Haloperidol	Haldol (US & UK), Aloperidin, Bioperidolo, Brotopon, Dozic, Duraperidol (Germany), Einalon S, Eukystol, Halosten, Keselan, Linton, Peluces, Serenace, Serenase, Sigaperidol	Antipsychotic	Schizophrenia, agitation
Hydrochlorothiazide	Apo-Hydro, Aquazide H, BP Zide, Dichlotride, Hydrodiuril, HydroSaluric, Hydrochlorot, Microzide, Esidrex, Oretic	Diuretic	Hypertension, diuresis
Hydrocodone – ER	Hysingla™ ER, Zohydro ER	Analgesic	Pain, severe
Hydroxychloroquine	Plaquenil, Quineprox	Antimalarial, Anti-inflammatory	Malaria, SLE, rheumatoid arthritis
Hydroxyzine	Atarax, Vistaril, Aterax, Alamon, Durrax, Equipose, Masmoran, Orgatrax, Paxistil Quiess, Tran-Q, Tranquizine	Antihistamine	Allergic reaction, anxiety disorders
Ibogaine (Only on Non US Market)	None	Psychedelic	Narcotic addiction, unproven
Ibutilide	Corvert	Antiarrhythmic	Arrhythmia
Iloperidone	Fanapt, Fanapta, Zomaril	Antipsychotic, atypical	Schizophrenia
Imipramine (melipramine)	Tofranil	Antidepressant, Tricyclic	Depression
Indacaterol	Arcapta Neohaler (US), Onbrez Breezhaler (Canada), Utibron (combo w/ glycopyrrolate)	Bronchodilator	Asthma, COPD
Indapamide	Lozol, Natrilix, Insig	Diuretic	Hypertension, diuresis
Inotuzumab ozogamicin	Besponsa	Anti-cancer	Cancer (acute lymphocytic leukemia}
Isoproterenol	Medihaler-Iso, Isuprel	Bronchodilator	Allergic reaction
Isradipine	Dynacirc	Antihypertensive	Hypertension
Itraconazole	Sporanox, Onmel	Antifungal	Fungal infection
Ivabradine	Procoralan, Coralan, Corlentor, Coraxan, Ivabid, Bradia	Antianginal	Angina Pectoris (heart pain)
Ketanserin (Only on Non US Market)	Sufrexal	Antihypertensive	Hypertension
Ketoconazole	Nizoral, Sebizole, Ketomed, Keton	Antifungal	Fungal infection
Lacidipine (Only on Non US Market)	Lacipil, Motens	Calcium channel blocker	Hypertension
Lansoprazole	Prevacid	Proton Pump Inhibitor	Gastric hyperacidity, GERD
Lapatinib	Tykerb, Tyverb	Anti-cancer	Cancer (breast, metastatic)
Lenvatinib	Lenvima	Anti-cancer	Cancer (Thyroid)
Leuprolide	Lupron, Eligard, Viadur, Carcinil, Enanton, Leuplin, Lucrin, Procren, Prostap and others	Gonadotropin receptor agonist/antogist	Cancer (prostate)
Levalbuterol (levsalbutamol)	Xopenex, Levolin, Axazest	Bronchodilator	Asthma
Levofloxacin	Levaquin, Tavanic	Antibiotic	Bacterial infection
Levomepromazine (methotrimeprazine) (Only on Non US Market)	Nosinan, Nozinan, Levoprome	Antipsychotic	Schizophrenia
Levomethadyl acetate (Removed from Market)	Orlaam	Opiate	Narcotic dependence
Levosulpiride (Only on Non US Market)	Lesuride, Levazeo, Enliva (with rabeprazole)	Antipsychotic	Schizophrenia
Lisdexamfetamine	Vyvanse	CNS stimulant	ADHD
Lithium	Eskalith, Lithobid	Antimanic	Bipolar disorder
Loperamide	Imodium and many other OTC and Rx brands	Opiate	Diarrhea
Lopinavir and ritonavir	Kaletra, Aluvia	Antiviral	HIV/AIDS
Maprotiline	Ludiomil and others	Anti-depressant, Tetracyclic	Depression
Melperone (Only on Non US Market)	Bunil, Buronil, Eunerpan	Antipsychotic, atypical	Schizophrenia
Memantine	Namenda XR and many others	NMDA receptor antagonist	Alzheimer’s disease
Mesoridazine (Removed from Market)	Serentil	Antipsychotic	Schizophrenia
Metaproterenol (orciprenaline)	Metaprel, Alupent	Bronchodilator	Asthma
Methadone	Dolophine, Symoron, Amidone, Methadose, Physeptone, Heptadon	Opiate	Narcotic dependence, pain
Methamphetamine (Metamfetamine)	Desoxyn, Pervitin, Anadrex, Methedrine, Syndrox	CNS stimulant	Obesity, ADHD
Methylphenidate	Ritalin, Concerta, Focalin, Daytrana, Methylin, Metadate CD	CNS stimulant	ADHD
Metoclopramide	Reglan, Afipran, Maxolon, Cerucal, Clopamon, Clopra, Maxeran, Maxolon, Metozolv, Plasil, Pramin, Primperan, Perinorm	Antiemetic	Nausea, vomiting
Metolazone	Zytanix, Zaroxolyn, and Mykrox	Diuretic	Hypertension, diuresis
Metronidazole	Flagyl and many others	Antibiotic	Trichomoniasis, amebiasis, bacterial infection
Midodrine	ProAmatine, Amatine, Gutron	Vasoconstrictor	Hypotension
Midostaurin	Rydapt	Anti-cancer	Cancer (Acute myeloid leukemia)
Mifepristone	Korlym, Mifeprex	Progesterone antagonist	Pregnancy termination
Mirabegron	Myrbetriq	Beta3 adrenergic antagonist	Bladder spasm
Mirtazapine	Remeron	Antidepressant, Tetracyclic	Depression
Moexipril/HCTZ	Uniretic, Univasc	Antihypertensive	Hypertension, diuresis
Moxifloxacin	Avelox, Avalox, Avelon	Antibiotic	Bacterial infection
Necitumumab	Portrazza	Anti-cancer	Cancer (Lung)
Nelfinavir	Viracept	Antiviral	Viral infection (HIV/AIDS)
Nicardipine	Cardene	Antihypertensive	Hypertension
Nilotinib	Tasigna	Anti-cancer	Cancer (leukemia)
Norepinephrine	Levophed	Vasconstrictor, Inotrope	Heart failure, shock (low blood pressure)
Norfloxacin (Removed from Market)	Noroxin, Ambigram	Antibiotic	Bacterial infection
Nortriptyline	Pamelor, Sensoval, Aventyl, Norpress, Allegron, Noritren, Nortrilen	Antidepressant, Tricyclic	Depression
Nusinersen	Spinraza	Antisense oligonucleotide	Spinal Muscular Atrophy
Ofloxacin	Floxin	Antibiotic	Bacterial infection
Olanzapine	Zyprexa, Zydis, Relprevv	Antipsychotic, atypical	Schizophrenia, bipolar disorder
Olodaterol	Striverdi Respimat	Bronchodilator	Asthma
Omeprazole	Losec, Prilosec, Zegerid	Proton Pump Inhibitor	Gastric hyperacidity, GERD
Ondansetron	Zofran, Anset, Ondemet, Zuplenz, Emetron, Ondavell, Emeset, Ondisolv, Setronax	Antiemetic	Nausea, vomiting
Osimertinib	Tagrisso	Anti-cancer	Cancer (EGFR pos. NSC Lung cancer)
Oxaliplatin	Eloxatin	Anti-cancer	Cancer
Oxytocin	Pitocin, Syntocinon	Oxytocic	Labor stimulation
Paliperidone	Invega, Xepilon	Antipsychotic, atypical	Schizophrenia
Palonosetron	Aloxi	Antiemetic	Nausea, vomiting
Panobinostat	Farydak	Histone deacetylase inhibitor	Cancer, Multiple myeloma
Pantoprazole	Protonix and others	Proton Pump Inhibitor	Gastric hyperacidity, GERD
Papaverine HCl (Intra-coronary)	none	Vasodilator, Coronary	Diagnostic adjunct
Paroxetine	Paxil, Aropax, Pexeva, Seroxat, Sereupin, Seroxat	Antidepressant, SSRI	Depression
Pasireotide	Signifor	Somatostatin analog	Cushings Disease
Pazopanib	Votrient	Anti-cancer	Cancer (renal cell, sarcoma)
Pentamidine	Pentam	Antifungal	Fungal infection (Pneumocystis pneumonia)
Perflutren lipid microspheres	Definity, Optison	Imaging contrast agent	Diagnostic adjunct
Perphenazine	Trilafon, Etrafon/Triavil, Decentan	Antipsychotic	Schizophrenia
Phentermine	Adipex P, Adiphene (India), Anoxine-AM, Ionamin, Duromine, Metermine, Miraprontv, Obephen, Obermine, Obestin-30, Phentremine, Phentrol, Phenterex, Phentromin, Pro-Fast SA, Redusa, Panbesy, Obenix, Oby-Trim, Teramine, Zantryl, Sinpet, Supremin, Suprenza, Umine, Weltmine	Appetite suppressant	Obesity
Phenylephrine	Neosynephrine	Vasoconstrictor	Shock (low blood pressure), allergic rhinitis, asthma
Phenylpropanolamine (Removed from Market)	Acutrim, Dexatrim	Appetite suppressant	Obesity
Pilsicainide (Only on Non US Market)	Sunrythm	Anti-arrhythmic	Arrhythmia
Pimavanserin	Nuplazid	Antipsychotic, atypical	Psychosis, Parkinson’s Disease
Pimozide	Orap	Antipsychotic	Tourette’s Disorder
Pipamperone (Only on Non US Market)	Dipiperon (E.U), Propitan (Japan), Dipiperal, Piperonil, Piperonyl	Antipsychotic	Schizophrenia
Piperacillin/Tazobactam	Tazosyn and Zosyn	Antibiotic	Bacterial infection
Posaconazole	Noxafil, Posamol	Antifungal	Fungal infection
Primaquine phosphate		Antimalarial	Malaria
Probucol (Removed from Market)	Lorelco	Antilipemic	Hypercholesterolemia
Procainamide	Pronestyl, Procan	Antiarrhythmic	Arrhythmia
Promethazine	Phenergan	Antipsychotic / Antiemetic	Nausea, vomiting
Propafenone	Rythmol SR, Rytmonorm	Sodium channel blocker	Arrhythmia
Propofol	Diprivan, Propoven	Anesthetic, general	Anesthesia
Prothipendyl (Only on Non US Market)	Dominal, Largophren, Timoval, Timovan, Tumovan	Antipsychotic	Schizophrenia
Pseudoephedrine	PediaCare, Sudafed	Decongestant	Allergic reaction, allergic rhinitis, asthma
Quetiapine	Seroquel	Antipsychotic, atypical	Schizophrenia
Quinidine	Quinaglute, Duraquin, Quinact, Quinidex, Cin-Quin, Quinora	Antiarrhythmic	Arrhythmia
Quinine sulfate	Qualaquin	Antimalarial	Malaria, leg cramps
Ranolazine	Ranexa, Ranozex	Antianginal	Angina Pectoris (heart pain)
Ribociclib	Kisqali	Anti-cancer	Cancer (breast)
Rilpivirine	Edurant, Complera, Eviplera	Antiviral	Viral infection (HIV/AIDS)
Risperidone	Risperdal	Antipsychotic, atypical	Schizophrenia
Ritodrine (Removed from Market)	Yutopar	Muscle relaxant	Premature labor
Romidepsin	Istodax	Histone deacetylase inhibitor	Cancer (lymphoma)
Roxithromycin (Only on Non US Market)	Rulide, Xthrocin, Roxl-150, Roxo, Surlid, Rulide, Biaxsig, Roxar, Roximycinv, Roxomycin, Rulid, Tirabicin, Coroxin	Antibiotic	Bacterial infection
Salmeterol	Serevent, Advair	Bronchodilator	Asthma
Saquinavir	Invirase(combo)	Antiviral	Viral infection (HIV/AIDS)
Sertindole (Only on Non US Market)	Serdolect, Serlect	Antipsychotic, atypical	Schizophrenia, anxiety
Sertraline	Zoloft, Lustral, Daxid, Altruline, Besitran, Deprax, Elrval, Emergen, Gladem, Implicane, Sedoran, Sealdin, SerivoLowfin, Stimuloton, Tresleen, Sertralin Bluefish	Antidepressant, SSRI	Depression
Sevoflurane	Ultane, Sojourn	Anesthetic, general	Anesthesia
Sibutramine (Removed from Market)	Meridia	Appetite suppressant	Obesity
Solifenacin	Vesicare	Muscle relaxant	Bladder spasm
Sorafenib	Nexavar	Anti-cancer	Cancer (liver, renal cell, metastatic thyroid)
Sotalol	Betapace, Sotalex, Sotacor	Antiarrhythmic	Arrhythmia
Sparfloxacin (Removed from Market)	Zagam	Antibiotic	Bacterial infection
Sulpiride (Only on Non US Market)	Dogmatil, Dolmatil, Eglonyl, Espiride, Modal, Sulpor	Antipsychotic, atypical	Schizophrenia
Sultopride (Only on Non US Market)	Barnetil, Barnotil, Topral	Antipsychotic, atypical	Schizophrenia
Sunitinib	Sutent	Anti-cancer	Cancer (GIST, renal cell, pNET)
Tacrolimus	Prograf, Prograf, Advagraf, Protopic	Immunosuppressant	Immune suppression
Tamoxifen	Nolvadex(discontinued 6/13), Istubal, Valodex	Anti-cancer	Cancer (breast)
Telaprevir	Incivo, Incivek	Antiviral	Viral infection (hepatitis C)
Telavancin	Vibativ	Antibiotic	Bacterial infection
Telithromycin	Ketek	Antibiotic	Bacterial infection
Terbutaline	Brethine, Bricanyl, Brethaire, Terbulin	Bronchodilator	Asthma, premature labor
Terfenadine (Removed from Market)	Seldane	Antihistamine	Allergic rhinitis
Terlipressin (Only on Non US Market)	Teripress, Glypressin, Terlipin, Remestyp, Tresil, Teriss and others	Vasoconstrictor	Septic shock
Terodiline (Only on Non US Market)	Micturin, Mictrol (not bethanechol)	Muscle relaxant	Bladder spasm
Tetrabenazine	Nitoman, Xenazine	Vesicular Monoamine Transporter 2 Inhibitor	Chorea (Huntington’s disease)
Thioridazine	Mellaril, Novoridazine, Thioril	Antipsychotic	Schizophrenia
Tiapride (Only on Non US Market)	Tiapridal, Italprid, Sereprile, Tialaread, Tiaryl, Tiaprim, Tiaprizal, Sereprid, Tiapridex	Selective D2, D3 dopamine antagonist	Alcoholism, withdrawal
Tipiracil and Trifluridine	Lonsurf	Anti-cancer	Cancer (Metastatic colorectal cancer)
Tizanidine	Zanaflex, Sirdalud	Muscle relaxant	Muscle spasticity
Tolterodine	Detrol, Detrusitol	Muscle relaxant	Bladder spasm
Toremifene	Fareston	Estrogen agonist/antagonist	Cancer (breast, metastatic)
torsemide (torasemide)	Demadex, Diuver, Examide	Diuretic	Hypertension, diuresis
Tramadol	Crispin, Ralivia ER, Ralivia Flashtab, Tramadolum, Tramal, Tramodol, Tridural, Ultram, Ultram ER, Zydol	Analgesic	Pain
Trazodone	Desyrel (discontinued 6/13), Oleptro, Beneficat, Deprax, Desirel, Molipaxin, Thombran, Trazorel, Trialodine, Trittico, Mesyrel	Antidepressant, SARI	Depression, insomnia
Trimethoprim-Sulfamethoxazole	Septra, Bactrim, Sulfatrim, Biseptol, Co-trimoxazole, Cotrim, Septrin, Trisul	Antibiotic	Bacterial infection
Trimipramine	Surmontil, Rhotrimine, Stangyl	Antidepressant, Tricyclic	Depression
Tropisetron (Only on Non US Market)	Navoban, Setrovel	Antiemetic	Nausea, vomiting
Valbenazine	Ingrezza	Vesicular monamine transporter 2 inhibitor	Tardive Dyskinesia
Vandetanib	Caprelsa	Anti-cancer	Cancer (thyroid)
Vardenafil	Levitra	Phosphodiesterase 5 inhibitor	Erectile dysfunction
Vemurafenib	Zelboraf	Anti-cancer	Cancer (melanoma)
Venlafaxine	Effexor, Efexor	Antidepressant, SNRI	Depression
Vilanterol/fluticasone furoate	Breo Ellipta	Bronchodilator	Asthma
Voriconazole	VFend	Antifungal	Fungal infection
Vorinostat	Zolinza	Histone deacetylase inhibitor	Cancer (lymphoma)
Ziprasidone	Geodon, Zeldox	Antipsychotic, atypical	Schizophrenia
Zotepine (Only on Non US Market)	Losizopilon, Lodopin, Setous and Zoleptil	Antipsychotic, atypical	Schizophrenia
Zuclopenthixol, Zuclopentixol (Only on Non US Market)	Cisordinol, Clopixol, Acuphase	Antipsychotic	Psychosis

[Source ⁵⁵ ]

Long QT syndrome symptoms

Nearly half of patients with long QT syndrome NEVER have any signs or symptoms!

You might be aware of your condition only because of:

Results of an electrocardiogram (ECG) done for an unrelated reason
A family history of long QT syndrome
Genetic testing results

Signs and symptoms of inherited or congenital long QT syndrome might start as a fetus, during the first weeks to months after birth, as late as older age, or never at all. Most people who experience signs or symptoms from long QT syndrome have their first episode by age 40.

Signs and symptoms of long QT syndrome might occur during sleep or arousal from sleep.

The most common symptoms of long QT syndrome include:

Syncope (fainting): This is the most common symptom of long QT syndrome ⁵⁶. Long QT syndrome-triggered fainting spells (syncope) are caused by the heart temporarily beating in an erratic way. These fainting spells might happen when you’re excited, angry, scared or during exercise. You may lose consciousness without warning, for instance from being startled by a ringing telephone. If you have a normal fainting spell, you usually will have a warning sign first, such as lightheadedness, heart palpitations, irregular heartbeat, weakness or blurred vision. However, a fainting spell from long QT syndrome can occur with little to no warning.
Seizures: If the heart continues to beat erratically, the brain will eventually not get enough oxygen, which can cause seizures. Long QT syndrome can be misdiagnosed as epilepsy ⁵⁷, ⁵⁸, ⁵⁹.
Sudden death: Generally, the heart returns to its normal rhythm. If this doesn’t happen by itself, or if an external defibrillator isn’t used in time to convert the rhythm back to normal, sudden death will occur. In about 1 out of 10 people who have long QT syndrome, sudden cardiac arrest or sudden death is the first sign of the disorder.
Unexplained drowning or near drowning. This may be due to fainting while swimming.
Often, people who have LQTS 3 develop an abnormal heart rhythm during sleep. This may cause noisy gasping while sleeping.

The symptoms of long QT syndrome are related to Torsades de Pointes (see Figure 5). During this arrhythmia, the ventricle beats very fast and irregularly. The heart is unable to pump blood effectively to the body. If the brain does not receive an adequate blood supply, syncope (fainting) and seizure-like activity can occur. If the arrhythmia continues, sudden death will occur. If the heart rhythm returns to normal, symptoms will stop.

If you have potassium channel long QT syndrome, you carry the risk of sudden death if you are startled or awoken suddenly.
If you have sodium channel long QT syndrome, you have an increased risk of sudden death whilst sleeping.

Symptoms are most common during:

Exercise (or within a few minutes after)
Emotional excitement, especially being startled
During sleep or upon waking suddenly

Some people with congenital long QT syndrome never have symptoms. The diagnosis is made during a routine ECG or during an evaluation because a family member has it. Symptoms usually first appear during the early teen years.

Your doctor will advise you depending on the type of long QT syndrome you have. You may be advised not to take part in competitive sports, which can be difficult – especially for young people. Your doctor will help you arrive at a balance between being active and reducing your risk of making your condition worse.

The risk of sudden death is greater if you have a history of:

previous cardiac arrest
blackouts
a very long QT interval on your ECG [corrected QT (QTc) interval > 500 ms]
sodium channel mutations.

Strenuous exercise or severe exertion can increase the risk of sudden death for many people with long QT syndrome. Speak to your doctor if you have any questions about the risk of sudden death.

If you are with someone when they collapse suddenly, it is imperative to call your local emergency services number and try to perform CPR until an ambulance or medical help arrives. If you are untrained in CPR, the emergency services operator will be able to talk you through the process.

Silent long QT Syndrome

Sometimes long QT syndrome doesn’t cause any signs or symptoms. This is called silent long QT syndrome. For this reason, doctors often advise family members of people who have long QT syndrome to be tested for the disorder, even if they have no symptoms.

Medical and genetic tests may reveal whether these family members have long QT syndrome and what type of the condition they have.

Long QT syndrome complications

Most of the time, prolonged QT intervals in people with long QT syndrome never cause problems. However, physical or emotional stress might “trip up” a heart that is sensitive to prolonged QT intervals. This can cause the heart’s rhythm to spin out of control, triggering life-threatening, irregular heart rhythms (arrhythmias) including:

Torsades de Pointes — “twisting of the points” in French ⁶⁰. In this arrhythmia, your heart’s two lower chambers (ventricles) beat fast and chaotically, making the waves on an ECG monitor look twisted (Figure 5). Less blood is pumped out from your heart, so less blood reaches your brain, causing you to faint suddenly and, often, without any warning.

If a Torsades de Pointes episode is short — lasting less than one minute — your heart can correct itself and you regain consciousness on your own. However, if a Torsades de Pointes episode lasts longer, it can result in a sudden fainting spell followed by a full-body seizure. If the dangerous rhythm does not correct itself, then a life-threatening arrhythmia called ventricular fibrillation follows.

Ventricular fibrillation. This condition causes the ventricles to beat so fast that your heart quivers and ceases pumping blood. Unless your heart is shocked back into a normal rhythm by a defibrillator, ventricular fibrillation can lead to brain damage and sudden death.

Sudden cardiac death. It’s now known that long QT syndrome might explain some cases of sudden death in young people who otherwise appear healthy. Long QT syndrome might be responsible for some unexplained events in children and young adults, such as unexplained fainting, drownings or seizures.

Key risk factors for sudden cardiac death in patients with long QT syndrome include the following:
- QTc interval: QTc interval ≥ 500 ms is a major risk factor, particularly in inherited long QT syndrome type 1 (LQT1) and inherited long QT syndrome type 2 (LQT2) ⁶¹
- Genetic subtype: Patients with inherited long QT syndrome type 2 (LQT2) have a higher sudden cardiac death risk compared to other subtypes ⁶²
- Sex and age: Males have higher risk in childhood and females after puberty ⁶³, ⁶⁴
- History of syncope (fainting): Particularly if recurrent or without trigger ⁶⁵
- Family history of sudden cardiac death: Especially in young first-degree relatives such as your parents, siblings and your children ⁶⁶

Figure 5. Torsades de Pointes

Footnotes: Torsades de Pointes ECG with prolonged QT interval and the “twisting” or oscillating pattern of the QRS complexes, with the amplitude changing around the baseline. 12-lead ECG of Torsades de Pointes in a 56-year-old white female with low blood potassium (2.4 mmol/L) and low blood magnesium (1.6 mg/dL).

[Source ⁶⁷ ]

Figure 6. Ventricular fibrillation

Risk factors for developing abnormal heart rhythms in patients with long QT syndrome

The risk of abnormal heart rhythms in patients with long QT syndrome is influenced by a complex interplay of genetic, clinical, and environmental factors ⁶⁸.

Major risk factors for abnormal heart rhythms in patients with long QT syndrome include the following:

Genetic subtype:

Inherited long QT syndrome type 2 (LQT2) and inherited long QT syndrome type 3 (LQT3): Higher risk of syncope and sudden cardiac death compared to inherited long QT syndrome type 1 (LQT1) ⁶⁹.
Inherited long QT syndrome type 1 (LQT1): High risk during exercise, especially swimming ⁷⁰
Inherited long QT syndrome type 2 (LQT2): Prone to events during rest or sleep ⁷¹
Inherited long QT syndrome type 3 (LQT3): Higher risk during sleep or at rest ⁷²

QTc interval

QTc interval > 500 ms is associated with a significantly increased risk of sudden cardiac death, particularly in patients with LQT1 and LQT2 ⁷³. In addition, the presence of QTc interval > 500 ms in the first year of life is a major risk factor for sudden cardiac death in infants with congenital long QT syndrome ⁷⁴

Sex

In childhood, males have a higher risk of sudden cardiac than do females, particularly in LQT1 ⁷⁵. However, after puberty, the risk of sudden cardiac is higher in females, especially in LQT2 ⁷⁶, ⁶⁴, ⁷⁷.

History of syncope

A history of syncope is a major risk factor for sudden cardiac death in patients with long QT syndrome, particularly if the syncope is recurrent or occurs in the absence of a trigger ⁷⁸. In patients with a history of syncope, the risk of sudden cardiac death is highest in the first year after the syncopal event and decreases thereafter ⁷⁸. The presence of syncope in the first year of life is also a strong predictor of sudden cardiac death in infants with long QT syndrome ⁷⁹.

Family history of sudden cardiac death

Significant risk factor, especially in young relatives (<40 years) or multiple family members ⁶⁵.

Genotype-specific triggers

The risk of abnormal heart rhythms in patients with long QT syndrome is influenced by genotype-specific triggers, which can precipitate syncope or sudden cardiac death in susceptible individuals ⁸⁰.

Electrolyte imbalances

Electrolyte imbalances, particularly hypokalemia and hypomagnesemia, can prolong the QT interval and increase the risk of arrhythmic events ⁸¹.

Medications

QT-prolonging drugs increase the arrhythmic risk ⁸², ⁸³.

Comorbidities

Hypothyroidism, eating disorders, diabetes, obesity, and obstructive sleep apnea ⁵¹, ⁸⁴.

Genotype-phenotype modifiers

In addition to the primary genetic defect, other genetic factors (such as single nucleotide polymorphisms or modifier genes) can influence the clinical manifestations and arrhythmic risk in patients with Long QT syndrome. For example, the presence of certain polymorphisms in the NOS1AP gene (which encodes a nitric oxide synthase adaptor protein) has been associated with an increased risk of SCD in patients with long QT syndrome, particularly those with LQT1 ⁸⁵, ⁸⁶.

Long QT syndrome diagnosis

If long QT syndrome is suspected, your doctor will want to ask questions about your medical history, as well as your family’s.

Your doctor will also ask you if you have a:

Family history of long QT syndrome
Family history of unexplained fainting, seizures, or cardiac arrest
History of fainting, seizures or cardiac arrest, especially with exercise

For example, studies of otherwise healthy people with long QT syndrome indicate that they had at least one episode of fainting by age 10. The majority also had a family member with long QT syndrome.

Unexplained fainting episodes or a family history of heart-related death may warrant electrocardiogram (EKG or ECG) testing for you and your closes relatives. Your doctor may also recommend an exercise stress test.

If your doctor thinks you may have long QT syndrome, you might need several tests to confirm the diagnosis. These include:

Electrocardiogram (ECG). During an ECG, doctors attach sensors to your chest (electrodes) that can detect the electrical activity of your heart. An ECG measures the timing and duration of each electrical phase in your heartbeat. You might have this test while at rest or during an exercise stress test, in which doctors monitor your heart activity as you exercise on a treadmill or a stationary bicycle. Your doctor may also suggest your family members have ECGs.
- The space between the start of the Q wave and the end of the T wave (QT interval) corresponds to the time it takes for your heart to contract and then refill with blood before beginning the next contraction. The QT interval represents the time from the electrical stimulation (depolarization) of the heart’s pumping chambers (ventricles), to the end of the recharging of the electrical system (repolarization) and therefore roughly estimates the duration of an average ventricular action potential ²⁹. The interval between the letters Q and T defines the action of the ventricles. The QT interval is measured in milliseconds (msec) and closely approximates the time from the beginning of the heart ventricles’ contraction until the end of relaxation.
- The QT interval interval can range from 0.20 to 0.40 seconds (200 to 400 msec), depending upon your heart rate. At high heart rates, ventricular action potentials shorten in duration, which decreases the QT interval ²⁹. Long QT syndrome means that time period is too long, even if by fractions of a second. Because prolonged QT intervals can be diagnostic for susceptibility to certain types of heart arrhythmias, it is important to determine if a QT interval is excessively long. The QT interval is often expressed as a corrected QT (QTc) by taking the QT interval and dividing it by the square root of the R-R interval (interval between ventricular depolarizations) using Bazett formula: QTc = QT / √ RR ⁷. Corrected QT (QTc) allows an assessment of the QT interval that is independent of the heart rate. Normal corrected QTc intervals are 0.44 seconds or less (<440 msec). QTc is prolonged if it is greater than 440 ms in men or greater than 460 ms in women ³⁰. A QTc greater than 500 is associated with an increased risk of Torsade de Pointes. While several equations exist to help correct heart rate variation, the Bazett formula (QTC = QT / √ RR) is the most commonly used. Though the Bazett formula seems relatively accurate in heart rates between 60 to 100 beats/min, it tends to overcorrect with higher heart rates and undercorrect with lower heart rates.
- The hallmark ECG feature of long QT syndrome (LQTS) is a prolonged QT interval, reflecting delayed ventricular repolarization ⁸⁷. QTc interval > 460 ms in females and QTc interval > 450 ms in males are considered prolonged ³⁰. However, up to 25% of patients with genetically confirmed long QT syndrome may have normal QTc intervals ⁸⁸, ⁸⁹.
- Additional ECG findings suggestive of long QT syndrome include T-wave alternans (TWA), T-wave notching, and bradycardia ⁹⁰.
- Once corrected QT (QTc) is identified as prolonged, the next step in a workup is to look for acquired causes. The most common cause of QT prolongation in an ICU setting is usually drug-related. Serum potassium, calcium, and magnesium levels should be checked, as low serum of each can cause QT prolongation. Also, stimulating thyroid hormone (TSH) levels may be checked in patients with suspected hypothyroidism.
- In the absence of reversible or acquired causes of QT prolongation, long QT syndrome is diagnosed ⁷. In these patients, obtaining an electrocardiography of the patient and family members may be very helpful. Genetic testing of the patient and family members is the gold standard; however, this testing is limited by cost ⁷. Drug provocation with epinephrine or isoproterenol is warranted in patients with a borderline presentation ⁷. The concept of this testing is that patients with Long QT syndrome have an abnormal response to sympathetic stimulation. Their ECG shows the failure of the QT interval to shorten with increased heart rates, or it may even show prolongation. In patients with LQT2, there is marked shortening with exercise, however, exaggerated lengthening of the QT interval as the heart rate declines during late recovery ⁷.
Holter monitor. This portable ECG device can be worn for a day or more to record your heart’s activity as you go about your routine.
Event monitor. This portable ECG device is attached to your body to monitor your heart activity over a few weeks to a few months. When you have symptoms, you press a button. This allows your doctor to check your heart rhythm at the time of your symptoms.

Long QT syndrome is usually diagnosed by measuring the Q-T interval on the ECG.

In some people with suspected long QT syndrome, the ECG doesn’t show an abnormally prolonged QT interval. You may need other tests, such as:

Exercise stress test. Some people have a long QT interval only while they exercise. For this reason, your doctor may recommend that you have a stress test. During an exercise stress test, you exercise to make your heart work hard and beat fast. An EKG is done while you exercise. If you can’t exercise, you may be given medicine to increase your heart rate.
A nonexercise (medication) stress test. This is an ECG test done while you’re given a medication such as epinephrine (Adrenalin) that stimulates your heart in a way similar to exercise. Doctors then monitor the effects of the medication on the way your heart recharges. This test can help doctors diagnose people with suspected long QT syndrome and may help determine which genes are associated with the condition. It may also be used to diagnose people with long QT syndrome who have a gene associated with long QT syndrome but who have a normal QT interval (recharging time) at rest.
Genetic testing. A genetic test for long QT syndrome is available and may be covered by some private and governmental insurance plans. Genetic tests for long QT syndrome can generally find the genetic cause for about 3 out of every 4 cases of inherited long QT syndrome. However, genetic tests can’t detect all cases of long QT syndrome. So, even if you have long QT syndrome, the genetic tests may not show it. Also, some people who test positive for long QT syndrome don’t have any signs or symptoms of the disorder. These people may have silent long QT syndrome. Less than 10 percent of these people will faint or suddenly die from an abnormal heart rhythm. Even if you have silent long QT syndrome, you may be at increased risk of having an abnormal heart rhythm while taking medicines that affect potassium ion channels or blood levels of potassium. If your genetic cause of long QT syndrome is discovered through a positive genetic test, your doctor may recommend that your family members also be tested to determine whether they inherited the same genetic mutation.
A second opinion. You might want to seek a second opinion before proceeding with treatment if your doctor diagnoses you with long QT syndrome. People can sometimes be misdiagnosed as having long QT syndrome when it’s not actually present.

Schwartz score

The Schwartz’s score is a clinical scoring system used to diagnose congenital long QT syndrome (LQTS) ⁹¹. The Schwartz score assigns points to clinical and ECG features to estimate long QT syndrome (LQTS) probability ⁹². Schwartz’s scores range from 0 to 9, with Schwartz’s score ≤ 1 low probability; 1.5–3 intermediate probability; ≥ 3.5 high long QT syndrome (LQTS) probability.

The clinical features included in the Schwartz score are syncope (1–2 points), congenital deafness (0.5 points), and a family history of LQTS or unexplained sudden death (0.5–1 points). The ECG features included are QTc interval ≥ 480 ms (3 points), 460–479 ms (2 points), or 450–459 ms (1 point); T wave alternans (TWA) (1 point); notched T waves in 3 leads (1 point); and bradycardia (0.5 points).

Table 2. Schwartz Score for Long QT Syndrome (LQTS)

CRITERIA	POINTS
Patient History
Syncope with stress†	2
Syncope without stress†	1
Congenital deafness	0.5
Family History
Family member with known LQTS‡	1
Family member with unexplained cardiac death before age 30 ‡	0.5
Electrocardiography§
QTc ≥ 480 msec	3
QTc 460-479 msec	2
QTc 450-459 msec (males only)	1
QTc ≥ 480 msec during 4th minute of recovery from an exercise test	1
Torsades de pointe arrhythmia§	2
T wave alternans (TWA)	1
Notched T wave in 3 leads	1
Resting heart rate < 2nd percentile for age (bradycardia)	0.5

Footnotes: * SCORE: ≤ 1 low probability; 1.5–3 intermediate probability; ≥ 3.5 high probability

† Mutually exclusive (ie, if syncope occurs with stress, no points are given for syncope without stress)

‡ Mutually exclusive

§ If torsades de pointe present, do not score syncope

[Source ⁹² ]

Provocative testing

Provocative tests can unmask long QT syndrome in patients with borderline QTc intervals or normal ECGs ⁹³:

Exercise stress testing: Useful for diagnosing congenital long QT syndrome type 1 (LQT1) ⁹⁴, ⁹⁵
Epinephrine infusion: Helps distinguish between LQT1 and LQT2 ⁹⁶
Mental stress testing: Potential method for unmasking concealed long QT syndrome ⁹⁷.

Holter monitoring and event recorders

Ambulatory ECG monitoring can capture transient QT prolongation or T-wave abnormalities ⁹⁸, ⁹⁹. Implantable loop recorders may be used for long-term monitoring or risk stratification ¹⁰⁰.

Genetic testing

Genetic testing is essential for confirming long QT syndrome diagnosis and identifying specific subtypes ¹⁰¹. Commercial panels screen for mutations in up to 17 long QT syndrome-associated genes, with a 50%–80% diagnostic yield ¹⁰², ¹⁰³. KCNQ1 (LQTS1), KCNH2 (LQTS2), and SCN5A (LQTS3) account for 75% of genetically confirmed cases ¹⁰⁴. Genetic testing aids in identifying asymptomatic family members at risk and guiding genotype-specific management ¹⁰⁵.

Family screening

Family screening is essential because of the autosomal dominant inheritance of most long QT syndrome subtypes ¹⁰⁶. First-degree relatives have a 50% chance of carrying the same mutation and should undergo clinical evaluation, ECG screening, and genetic testing ¹⁰⁷. Cascade screening helps identify asymptomatic carriers who may benefit from preventive measures and regular follow-up ¹⁰⁸.

Long QT syndrome treatment

Long QT syndrome treatment is aimed at preventing sudden death and controlling symptoms.

Treatment for inherited long QT syndrome involves some simple preventive measures. It can also involve medications, as well as left cardiac sympathetic denervation surgery or implanting medical devices such as a defibrillator (ICD), or both.

The goal of treatment is either to prevent the long QT heart from ever beating out of control or to prevent sudden death. Your doctor will discuss with you the most appropriate treatment options for your condition based on your symptoms, your type of long QT syndrome, and your risk of fainting or sudden cardiac arrest.

For acquired long QT syndrome, treating the cause of the condition may eliminate it. Doctors will also treat heart rhythm disorders (arrhythmias) as needed.

If you are diagnosed with acquired long QT syndrome due to certain medications, your doctor may recommend that you stop taking the medication causing the condition and switching medications. Some people might need additional treatment. Around 100 drugs have been associated with causing acquired long QT syndrome – many of them common including anti-depressants, antibiotics, and diuretics.

If your long QT syndrome is associated with a mineral imbalance such as being deficient in potassium, calcium or magnesium, the first step is to identify and fix the imbalance. You may require no extra treatment.

Immediate treatment

A hemodynamically unstable patient should receive non-synchronized electrical defibrillation or unsynchronized cardioversion that delivers a high-energy shock at any point during the cardiac cycle. Also, the first-line treatment is magnesium sulfate for suppressing early afterdepolarizations and terminating Torsades de Pointes arrhythmia and the benefit is independent of serum magnesium level ¹⁰⁹, ²², ¹¹⁰, ¹¹¹. Magnesium achieves this by decreasing the influx of calcium, thus lowering the amplitude of early afterdepolarizations ¹¹². Magnesium can be given at 1 to 2 g IV initially in 30-60 seconds, which then can be repeated in 5-15 minutes ²². Alternatively, a continuous magnesium infusion can be started at a rate of 3-10 mg/minute ²². Magnesium is effective even in patients with normal magnesium levels. Because of the danger of hypermagnesemia (depression of neuromuscular function), the patient requires close monitoring ²².

Some authorities recommend supplemental potassium to increase the potassium concentration to high normal, which increases the efflux of potassium from myocardial cells, thus causing rapid repolarization ²².

Temporary transvenous overdrive pacing should be considered for those who do not respond to magnesium sulfate ⁷. Based on the fact that the QT interval shortens with a faster heart rate, pacing can be effective in terminating Torsades de Pointes ²². Pacing is effective in both forms of the long QT syndrome because it facilitates the repolarizing potassium currents and prevents long pauses, suppressing early afterdepolarizations and decreasing the QT interval. Pacing should be instituted at a rate of 90-110 bpm until the QT interval is normalized. Overdrive pacing may be necessary at a rate of up to 140 bpm to control the rhythm ²².

Atrial pacing is the preferred mode because it preserves the atrial contribution to ventricular filling and also results in a narrower QRS complex and hence a shorter QT ²². In patients with AV block, ventricular pacing can be used to suppress Torsades de Pointes ²². This is dependent on intact atrial-to-ventricular conduction at the pacing rate found necessary.

Isoproterenol and Class IB antiarrhythmic drugs, such as lidocaine and phenytoin, may also be used ¹¹³, ¹¹⁴, ¹¹⁵, ¹¹⁶.

Mexiletine also may be helpful in suppressing Torsades de Pointes ²². In one study, mexiletine was used in patients with HIV who had acquired long QT interval and Torsades de Pointes ¹¹⁷. Mexiletine effectively suppressed the torsade on a long-term basis ¹¹⁷. Nakashima et al ¹¹⁸ reported Mexiletine successfully preventing refractory Torsades de Pointes and ventricular fibrillation in a 28-year-old patient with congenital type 2 long QT syndrome.

Medications for long-term management of Congenital Long QT syndrome

Medications used to treat long QT syndrome may include:

Beta-adrenergic antagonists (beta blockers) at maximally tolerated doses are used as a first-line long-term therapy in long QT syndrome ¹¹⁹, ¹²⁰, ²². These heart drugs include nadolol (Corgard) and propranolol (Inderal LA, InnoPran XL). Propranolol is used most extensively, but other agents such as esmolol or nadolol also can be used ²². They slow the heart rate and make the rhythm associated with long QT syndrome less likely. Beta blockers work by blunting the way your heart reacts to adrenaline. Most patients (even those without symptoms) are treated with a beta-blocker.
- However, beta-blockers should be avoided in those congenital long QT syndrome in which bradycardia is a prominent feature ²². Beta-blockers are also contraindicated in acquired long QT syndrome because bradycardia produced by these agents can precipitate Torsades de Pointes ²².
- Patients with congenital long QT syndromes are thought to have an abnormality of sympathetic balance or tone and are treated with beta-blockers ²². If the patient experiences breakthrough Torsades de Pointes, a short-acting beta-blocker, such as esmolol, can be tried ¹²¹.
- Isoproterenol can be used in bradycardia-dependent Torsades de Pointes that usually is associated with acquired long QT syndrome (pause-dependent) ²². Isoproterenol should be administered as a continuous IV infusion to keep the heart rate above 90 bpm ²². Isoproterenol accelerates AV conduction and decreases the QT interval by increasing the heart rate and reducing temporal dispersion of repolarization ²². Beta-adrenergic agonists such as isoproterenol are contraindicated in the congenital form of long QT syndrome (adrenergic-dependent) ²². Because of precautions, contraindications, and adverse effects associated with its use, Isoproterenol is used as an interim agent until overdrive pacing can be started ²².
- One approach to assess the adequacy of beta-blockade is by exercise testing. One investigator recommends aiming for at least a 20% reduction in maximum heart rate compared to that of the baseline (pre-beta blocker therapy). Another approach is to check the blood levels of beta blockers (eg, propranolol) when possible ¹²².
- Other medications may be used to shorten the Q-T interval. Your doctor will discuss what medications are best for you.
Mexiletine. Taking this anti-arrhythmic drug in combination with beta blockers might help shorten the QT interval and decrease the likelihood of a long QT syndrome-triggered faint, seizure or sudden death. This medication is often used for the third-most common subtype of inherited long QT syndrome, LQT3 ¹²³, ⁴², ¹²⁴. However, it may also be used for the two most common subtypes, LQT1 and LQT2.
Ranolazine, a sodium current (I_Na_L) inhibitor, shows benefits in LQT3 and along QT syndrome ¹¹⁹, ¹²⁵, ¹²⁶. These medications are currently off-label and reserved for patients failing first-line therapies ¹²⁷.
Spironolactone and potassium. For certain forms of long QT syndrome, spironolactone (Aldactone), a medication used to help the body hold on to potassium, or potassium supplements, or both, might improve the heart’s recharging system.
Magnesium and potassium supplements are used as adjunctive (add-on) therapies in long QT syndrome, particularly for recurrent arrhythmic events despite beta-blocker therapy ¹²⁸, ¹²⁹. Magnesium does not shorten QT interval but can reduce Torsades de Pointes risk in along QT syndrome ¹³⁰. Potassium supplements help maintain normal serum levels, preventing QT prolongation and arrhythmic events ¹¹⁹, ¹³¹. Routine use is not currently recommended; their use should be individualized on the basis of electrolyte status and clinical response.
Fish oil. In general, current evidence does not support supplementation with heart-healthy fish oil (omega-3 fatty acid) or eating fish high in omega-3 fatty acids to decrease the risk of cardiac events or death from abnormal heart rhythms. However, if you have inherited long QT syndrome, fish oil may be a reasonable complementary alternative medication to take in addition to other therapies. Talk to your doctor before starting fish oil or any other supplements or medications.

Your doctor might suggest treatment for long QT syndrome even if you don’t often experience signs or symptoms.

If you do need treatment, take the medications your doctor prescribes as directed. While medications won’t cure the condition, they provide some protection against possibly fatal disruptions of your heart rhythm. You might need to take a medication such as a beta blocker indefinitely.

Long-term treatment in acquired long QT syndrome usually is not required because the QT interval returns to normal once the inciting factor or predisposing condition has been corrected ²². Pacemaker implantation is effective in cases that are associated with heart block or bradycardia ²². Implantable cardioverter-defibrillators (ICDs) are indicated in cases that cannot be managed by avoidance of the offending agent.

Medical Devices

Patients who have a history of cardiac arrest or symptoms, in spite of beta-blocker therapy, may receive an implantable cardioverter defibrillator (ICD). This device detects life-threatening arrhythmias and automatically shocks the heart to prevent sudden death. Most new implantable cardioverter defibrillators (ICDs) can do the same job as a pacemaker, as well as detect dangerous heart rhythms. Once these are detected, the ICD can deliver a shock to restore your heart back to its normal rhythm. The implantable cardioverter-defibrillator (ICD) device is implanted under the skin of your chest, can stop a potentially fatal arrhythmia. An implantable cardioverter defibrillator (ICD) continuously monitors your heartbeat. If it detects an abnormal heart rhythm, it delivers electrical shocks to reset the heart to a normal rhythm. Implanting an implantable cardioverter defibrillator (ICD) is a major procedure and can result in inappropriate shocks and other complications. Therefore, the decision to implant an implantable cardioverter defibrillator, especially in children, needs to be carefully considered. Most people with inherited long QT syndrome do not need an implantable cardioverter defibrillator. Importantly, an implantable cardioverter defibrillator should not be implanted solely because of the tragic occurrence of a long QT syndrome-triggered sudden death in a relative. But the implantable cardioverter-defibrillator (ICD) device may be suggested for some athletes to help them return to competitive sports. The decision to place an implantable cardioverter-defibrillator (ICD), especially in children, needs to be carefully considered. Sometimes the device may send out shocks that aren’t needed. Talk with your heart specialist about the benefits and risks of an implantable cardioverter-defibrillator (ICD).
Pacemaker. Patients who have an abnormally slow heart rate may receive a pacemaker. A pacemaker delivers electrical impulses to control the rhythm of your heart, but it can’t deliver a shock to correct an arrhythmia. Pacemakers are devices that can be placed in your body, usually by surgery, to support the electrical system in your heart. Pacemaker can stabilize abnormal heart rhythms and prevent problems that can disrupt or endanger your life.

Left cardiac sympathetic denervation surgery

In left cardiac sympathetic denervation (LCSD) or a sympathectomy operation procedure, surgeons cut specific nerves along the left side of your spine in your chest. These nerves are part of the body’s sympathetic nervous system, which helps regulate heart rhythm that prompt your heart to beat faster in response to physical or emotional stress. This type of surgery keeps the heart beating at a steady pace and lowers the risk of dangerous heart rhythms in response to stress or exercise. The surgery also significantly reduces the risk of sudden death.

The left cardiac sympathetic denervation (LCSD) surgery is generally reserved for people who are considered at high risk of sudden death and are experiencing appropriate implantable cardioverter defibrillator (ICD) shocks, people who are continuing to experience fainting or seizures while taking their medications, or people unable to tolerate their medications because of side effects. However, accidental ablation of ocular efferent sympathetic nerves may result in Horner syndrome ²².

Lifestyle changes

In addition to medications or surgery, your doctor might recommend lifestyle changes to reduce your chances of a long QT syndrome-related fainting spell or sudden cardiac arrest. These could include:

Family testing – All first-line relatives (brothers, sisters, parents and children) should have EKG testing. Any other family members who have a history of seizures or fainting should also undergo testing.
Avoiding strenuous exercise or contact sports – If you have congenital long QT syndrome, sometimes, fatal arrhythmias occur with exercise ¹³². The decision to participate in competitive sports should be managed by a heart rhythm expert and certain precautions may be suggested. Or have a safety plan in place if you continue in competitive sports. In general, people with long QT syndrome should never swim alone. Physical activities are likely to be okay if you take someone along who can help if you faint.
- Inherited long QT syndrome type 1 (LQT1): Avoid competitive sports and strenuous exercise, especially swimming ¹³³
- Inherited long QT syndrome type 2 (LQT2) and inherited long QT syndrome type 3 (LQT3): Low-intensity exercise under medical supervision may be allowed ¹³⁴
Buddy system – Your family and friends should be told you have long QT syndrome. They should be told to call for emergency help if you begin to have symptoms or faint.
Avoiding medications that could cause prolonged QT intervals
- Avoid diuretics and medications causing electrolyte disturbances
Getting plenty of liquids during illnesses that are causing vomiting or diarrhea
- Maintain normal potassium and magnesium levels ¹³⁵
Lowering your temperature if a fever occurs
Reducing your exposure to loud or startling noises. Turn down the volume on doorbells and other devices such as phones that may startle you, especially during sleep. Things that startle you can cause you to pass out ⁶⁶.
Staying away from situations that could make you excited or angry. Being very excited, angry or surprised can trigger heartbeat changes in some people with long QT syndrome ¹³⁶, ¹³⁷, ¹³⁸. Getting more exercise, practicing mindfulness and connecting with others in support groups are some ways to reduce stress.

Work with your doctor to balance these lifestyle recommendations against the clear, heart-healthy benefits of an active lifestyle. It may be possible to stay fully active in sports, including competitive sports, after carefully reviewing the risks and benefits with your doctor.

If your symptoms are mild or don’t occur very often, your doctor might recommend only simple preventive measures or lifestyle changes, and he or she might not prescribe any daily medications for you.

Future treatments will be geared toward more gene specific therapies. For example, certain types of long QT syndrome are more likely to initiate events during exercise, while others are more related to startling or emotional distress. Your doctor will be able to give you activity guidelines based on the specific type of long QT syndrome gene you carry. Therapies may be directed to treat the specific gene, rather than prevention of future complications.

Long QT syndrome life expectancy

More than half of the people who have untreated, inherited types of long QT syndrome die within 10 years with up to 21 percent of people with Long QT syndrome may die within a year after they start fainting ²⁸. The prognosis for people with Long QT syndrome that is being treated is good with the risk of suffering cardiac arrest dropping to less than 1% over 20 years. Lifestyle changes and medicines can help people who have long QT syndrome prevent complications and live longer. Women with long QT syndrome can live a full life and give birth to children.

If you have long QT syndrome, talk with your doctor about which lifestyle changes and treatments are best for you.

Once you’ve been diagnosed with long QT syndrome, several steps can help you avoid serious consequences, including:

Avoiding strenuous physical activity or startling noises.
Adding more potassium to your diet (as your doctor advises).
Taking heart medicines called beta blockers. These medicines help prevent sudden cardiac arrest.
Having an implanted medical device, such as a pacemaker or implantable cardioverter defibrillator. These devices help control abnormal heart rhythms.
Don’t overexert yourself. You might not need to give up sports if you have long QT syndrome. Your doctor might permit recreational activities as long as you have a buddy along in case you have a fainting episode. In general, people with long QT syndrome should never swim alone. Strenuous exercise might be dangerous and isn’t recommended for some people with long QT syndrome. However, others might have a lower risk of complications and may be able to continue strenuous exercise and even competitive sports. Discuss this issue with your doctor in detail.
Know your symptoms. Be fully aware of symptoms that can warn you of irregular heart rhythms and decreased blood flow to your brain, such as feeling like you may faint.
Inform other people. Make family, friends, teachers, neighbors and anyone else who has regular contact with you aware of your heart condition. Wear a medical alert identification to notify health care providers of your condition.
Have plans in case of an emergency cardiac event. Family members may want to learn cardiopulmonary resuscitation (CPR) so they can provide immediate resuscitation if you ever need it. In some situations, it might be appropriate to have or be able to rapidly access an automatic external defibrillator. However, if your inherited long QT syndrome has been evaluated and treated carefully, you are generally unlikely to ever need CPR or an automatic external defibrillator.
Control startling events as much as possible. Turn down the volume on doorbells and turn off the telephone ringer or your cellphone at night.
Visit your doctor. Your cardiologist will likely recommend that you have regular follow-up appointments with him or her. Let your doctor know if you have symptoms of long QT syndrome or any changes in your condition. Your doctor may make changes to your treatment plan or suggest additional treatments for you.

Sexual intercourse doesn’t appear to increase the risk of long QT syndrome. Pregnancy and delivery aren’t associated with an increased risk of symptoms in women with long QT syndrome.

Still, if you have inherited long QT syndrome, your doctor will want to monitor you closely both during your pregnancy and after. Women with long QT syndrome, especially a form called LQT2, are at increased risk during the period following delivery and need careful monitoring.

Living With long QT syndrome

Long QT syndrome usually is a lifelong condition. The risk of having an abnormal heart rhythm that leads to fainting or sudden cardiac arrest may lessen as you age. However, the risk never completely goes away.

You’ll need to take certain steps for the rest of your life to prevent abnormal heart rhythms. You can:

Avoid things that trigger abnormal heart rhythms
Let others know you might faint or your heart might stop beating, and tell them what steps they can take
Have a plan in place for how to handle abnormal heart rhythms

If an abnormal heart rhythm does occur, you’ll need to seek treatment right away.

Avoid Triggers

If exercise triggers an abnormal heart rhythm, your doctor may tell you to avoid any strenuous exercise, especially swimming. Ask your doctor what types and amounts of exercise are safe for you.

If you have a pacemaker or implantable cardioverter defibrillator, avoid contact sports that may dislodge these devices. You may want to exercise in public or with a friend who can help you if you faint.

Avoid medicines that can trigger an abnormal heart rhythm. This includes some medicines used to treat allergies, infections, high blood pressure, high blood cholesterol, depression, and arrhythmias. Talk with your doctor before taking any prescription, over-the-counter, or other medicines or drugs.

Seek medical care right away for conditions that lower the sodium or potassium level in your blood. These conditions include the eating disorders anorexia nervosa and bulimia, excessive vomiting or diarrhea, and certain thyroid disorders.

If you have long QT syndrome 2, try to avoid unexpected noises, such as loud or jarring alarm clock buzzers and telephone ringers.

Inform Others

You may want to wear a medical ID necklace or bracelet that states that you have long QT syndrome. This will help alert medical personnel and others about your condition if you have an emergency.

Let your roommates, coworkers, or other people with whom you have regular contact know that you have a condition that might cause you to faint or go into cardiac arrest. Tell them to call your local emergency services number right away if you faint.

Consider asking a family member and/or coworker to learn cardiopulmonary resuscitation (CPR) in case your heart stops beating.

You also may want to keep an automated external defibrillator with you at home or at work. This device uses electric shocks to restore a normal heart rhythm.

Someone at your home and/or workplace should be trained on how to use the automated external defibrillator, just in case your heart stops beating. If a trained person isn’t available, an untrained person also can use the automated external defibrillator to help save your life.

If you have long QT syndrome 3 and you sleep alone, you may want to have an intercom in your bedroom that’s connected to someone else’s bedroom. This will let others detect the noisy gasping that often occurs if you have an abnormal heart rhythm while lying down.

Ongoing Health Care Needs

You should see your cardiologist (heart specialist) regularly. He or she will adjust your treatment as needed. For example, if you still faint often while using less aggressive treatments, your doctor may suggest other treatment options.

Emotional Issues and Support

Living with long QT syndrome may cause fear, anxiety, depression, and stress. Talk about how you feel with your health care team. Talking to a professional counselor also can help. If you’re very depressed, your doctor may recommend medicines or other treatments that can improve your quality of life.

Joining a patient support group may help you adjust to living with long QT syndrome. You can see how other people have coped with the condition. Talk with your doctor about local support groups or check with an area medical center.

Support from family and friends also can help relieve stress and anxiety. Let your loved ones know how you feel and what they can do to help you.

Some people learn they have long QT syndrome because they’re tested after a family member dies suddenly from long QT syndrome. Grief counseling may help you cope if this has happened to you. Talk with your doctor about finding a grief counselor.

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Long QT syndrome

What is Long QT syndrome