Long QT syndrome

Long QT syndrome is not one of the conditions included on newborn screening tests. The purpose of newborn screening programs are to identify newborns at risk of a potentially fatal or disabling condition as early as possible, ideally prior to any signs or symptoms. The goal is to diagnose early and treat as soon as possible to mitigate effects of the condition. Long QT syndrome presents in adolescence and/or adulthood, there is no need to include this on any newborn screening tests. Furthermore, it is not an easy or straightforward diagnosis to make. Therefore, unless there is a personal or family history of long QT syndrome, individuals are not routinely screened for long QT syndrome.

The Sudden Arrhythmia Death Syndromes (SADS) Foundation has a section on their website where you can find information on how to find a specialist cardiologist in your area who has experience treating people with long QT syndrome and other arrhythmia syndromes. To access that page, click here: Find a Physician

The best place to find information on clinical trials on long QT syndrome is on the Clinicaltrials.gov website.

Individuals with Long QT syndrome (LQTS) can start having symptoms at any time from infancy to adulthood. However, depending on the type of LQTS and the gene(s) involved, the risk for onset of cardiac events is often higher from preteen years to the 20s. Even in family members with the same gene change, they may have a range of symptoms from no issues to severe and frequent cardiac events. This means that genetic testing in someone before they have symptoms may not be able to predict when they will start having symptoms, how serious they will be, or how fast they might worsen. It will however, allow them to avoid medications, substances, and events that lengthen the QT interval (link to that list) and work closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information so if and when symptoms occur they will be prepared and reduce the chance of sudden death.

Individuals who present with syncope (fainting/passing out) and arrhythmia (heart beat abnormalities) will be evaluated for the cause of this through:

The signs and symptoms of long QT syndrome include:

When an individual is diagnosed with long QT syndrome (LQTS) it is most important for them to be evaluated and followed by a cardiologist (heart specialist) experienced with LQTS to learn more about the symptoms and guide medical management and prevention. Depending on the type of LQTS, it can also be important to be evaluated for other related health issues. If the diagnosis was not made by a genetics team, then the individual should also have a genetics consultation to help identify family members at risk and help facilitate testing for them.

The best place to find the most up-to-date research for long QT syndrome is on the Clinicaltrials.gov website.

Different types of Long QT syndrome (LQTS) have different overall treatment, monitoring, and prevention recommendations that can be discussed with a heart doctor familiar with and expertise in LQTS and a full understanding of an individual’s specific health issues. In general though, individuals with LQTS should avoid any medication that is know to increase the QT interval or increases the risk for abnormal heart rhythms like torsades de pointes (TdP). There is a detailed list of these medications on the website CredibleMeds® (free registration required) which can be used to check medications before use.

Since the underlying abnormality in long QT syndrome is the abnormal conduction of electrical impulses in the heart, it is ideal to be followed by a specialist cardiologist called an electrophysiologist. If an electrophysiologist is not available, a cardiologist who is experienced in treating individuals with long QT syndrome would also be helpful to treat and manage your condition. To find a doctor who specializes in treating patients with long QT syndrome, visit the Sudden Arrhythmia Death Syndromes webpage, or click this link: Find a Physician.

The penetrance of long QT syndrome, or the chance that a person with a pathogenic variant in one of the genes associated with long QT syndrome will experience symptoms depends on the genetic etiology or underlying cause of the condition.

With regard to the three most common types of long QT syndrome, the penetrance for each of them is as follows:

Individuals with long QT syndrome (LQTS) can live a standard lifespan with good quality of life, particularly if they are identified prior to their first cardiac event and have worked closely with healthcare providers to develop a detailed monitoring, prevention, and treatment plan. However, depending on the type of LQTS and the gene involved, the risk for life threatening cardiac events is higher than in the general population, particularly from preteen years to the 20s. In about 10-15% of undiagnosed individuals living with LQTS, sudden cardiac death is the first sign of the disease. In diagnosed individuals living with treated LQTS and their relatives (who may or may not be treated), the cumulative mortality is 6-8% for LQTS type 1, 2, and 3. Different types of LQTS can be broken out of that estimate by type. For example, one study found that the cumulative mortality rates were:
2% in children ages 0-18 and 5% in adults aged 19-40 years in people living with LQTS type 1
3% in children ages 0-18 and 7% in adults aged 19-40 years in people living with LQTS type 2
7% in children ages 0-18 and 5% in adults aged 19-40 years in people living with LQTS type 3
In individuals living with LQTS over 40 years, cardiac events are rarely and often associated with low potassium levels (hypokalemia) or taking medications that make the QT interval longer or cause hypokalemia. Having said this, individuals with type 3 LQTS do have an increased risk for cardiac events through adulthood.
The best chance of decreasing the mortality rate in an individual with LQTS is to avoid medications, substances, and events that lengthen the QT interval and work closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information. For many individuals this may include taking medications such as a beta blocker or sodium channel blocker, possibly surgery to place an implantable cardioverter-defibrillator (ICD) and/or left cardiac sympathetic denervation (LCSD). It is also important to have regular appointments checking on the effectiveness of the existing treatment plan and watching for other health issues, particularly during childhood when children may need frequent changes in medication dose as they grow. Having automatic external defibrillators available at home, at school, and activities or sports restrictions may be recommended by a doctor for some individuals with LQTS.

Individuals with long QT syndrome (LQTS) can live a normal lifespan with great quality of life, particularly if they are identified prior to their first cardiac event and have worked closely with healthcare providers to develop a detailed monitoring, prevention, and treatment plan. However, depending on the type of LQTS and the gene involved, the risk for life threatening cardiac events is higher than in the general population, particularly from preteen year to the 20s. In about 10-15% of undiagnosed individuals living with LQTS, sudden cardiac death is the first sign of the disease. In diagnosed individuals living with treated LQTS and their relatives (who may or may not be treated), the cumulative mortality is 6-8% for LQTS type 1, 2, and 3. Different types of LQTS can be broken out of that estimate by type. For example, one study found that the cumulative mortality rates were:
2% in children ages 0-18 and 5% in adults aged 19-40 years in people living with LQTS type 1
3% in children ages 0-18 and 7% in adults aged 19-40 years in people living with LQTS type 2
7% in children ages 0-18 and 5% in adults aged 19-40 years in people living with LQTS type 3
In individuals living with LQTS over 40 years, cardiac events are rare and often associated with low potassium levels (hypokalemia) or taking medications that make the QT interval longer or cause hypokalemia. Having said this, individuals with type 3 LQTS do have an increased risk for cardiac events through adulthood.
The best chance of increasing life expectancy in an individual with LQTS is to avoid medications, substances, and events that lengthen the QT interval (link to that list) and work closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information. For many individuals this may include taking medications such as a beta blocker or sodium channel blocker, possibly surgery to place an implantable cardioverter-defibrillator (ICD) and/or left cardiac sympathetic denervation (LCSD). It is also important to have regular appointments checking on the effectiveness of the existing treatment plan and watching for other health issues, particularly during childhood when children may need frequent changes in medication dose as they grow. Having automatic external defibrillators available at home, at school, and activities or sports restrictions may be recommended by a doctor for some individuals with LQTS.

Long QT syndrome (LQTS) is inherited in an autosomal dominant manner through families. This means that that the condition occurs in the presence of one genetic change (called a mutation or pathogenic variant) in one of the LQTS related genes. It also means that the inheritance pattern doesn’t change if a person is male or female.

Humans have two copies of the LQTS related genes, one from their mother and one from their father. A person has LQTS when they inherit one normal copy of an LQTS gene and one copy of an LQTS gene with a mutation. Just having one copy of the gene with a mutation is enough to cause LQTS in a person. A person with LQTS has a 50% chance of passing the copy of the gene with the causative gene mutation to each of their children and 50% to pass down the normal copy of the gene to each of their children.

Long QT syndrome path to disease (pathogenesis) is associated with the way ions (small particles) flow into and out of the cell through channels. This passage way or channel is called a voltage-gated channel. The type of channel is based on the charged ion it allows into or out of the cell. . In total, there are 15 subtypes of long QT syndrome which differ based on the gene involved and the specific features of disease. The most common subtypes of long QT syndrome account for approximately 75% of cases of long QT syndrome, as of 2019. There are three genes associated with long QT syndrome types 1 through 3:

Long QT syndrome is an inherited condition affecting the heart’s rhythm. Specifically, it delays the time it takes for the heart to recharge. This results in a longer than average "QT interval" on a heart test called an electrocardiogram (also called ECG or EKG).

The heart is a muscle and is stimulated to beat in specific rhythms by its electrical system. This electrical system governs how fast or slow the heart beats and accordingly, how much oxygen containing blood is pumped into the body.

The heart’s electrical system is measured with a test: electrocardiogram or ECG. The ECG traces this electrical system and creates a waveform. It is comprised of parts represented by letters: P, Q, R, S, and T. The P wave, which measures pushing of blood from the top two heart chambers (atrial depolarization) into the bottom two chambers (ventricles). B) The QRS complex, which represents the blood being pushed out of the bottom two chambers (ventricles) into the lungs and the body. And lastly, C) The T wave, which is the filling of the atria (repolarization). The length of time from when the ventricles contract to the filling of the atria is the QT interval.

The sinoatrial node (SA node) is the body’s natural pacemaker and sets the rhythm and pace of the heartbeat. It is located in the upper right part of the heart (right atrium) and travels across and down to the lower part of the heart (ventricles). The electrical system of the heart muscle opens and closes ion channels of the cell, which allows particles (ions) to flow through into and out of the muscle cells. The ion flow makes the heart muscle contract and relax; thus controlling the flow of blood into and out of the heart. Long QT syndrome is a type of condition called a "channelopathy". In a channelopathy, the ion channels of the heart muscle are not functioning properly, which causes the heart rhythm to be abnormal. Specifically, the time it takes the heart to recharge is delayed. Therefore, the QT interval is longer than normal.

The elongation of the QT interval can cause a fast heartbeat (tachycardia), which typically occurs in the ventricles (ventricular tachycardia). Ventricular tachycardia is associated with a finding on ECG called "Torsade de Pointes" which are self-terminating and causes fainting (syncope) and sometimes a disorganized heart rhythm in the ventricles (ventricular fibrillation). Ventricular fibrillation prevents blood flow (cardiac arrest) and may result in sudden death.

Long QT syndrome is a rare condition that can be genetic, or brought on (induced) by medications, drugs, or a result of a different heart condition. There are approximately 15 different types of inherited long QT syndrome. The majority of individuals affected by long QT syndrome with have types 1 through 3. The differences include genetic etiology; likelihood an affected individual will have symptoms; triggers for cardiac arrest; and treatment options. Notably, there are two types of long QT syndromes that are inherited in an autosomal recessive manner and are also associated with congenital sensorineural deafness. These types involve the KCNE1 gene and the KCNQ1 gene and are also known as Jervell and Lange-Nielsen syndrome.

The heart’s electrical system is measured with a test: electrocardiogram or ECG. The ECG traces this electrical system and creates a waveform. It is comprised of parts represented by letters: P, Q, R, S, and T. A) The P wave, which measures pushing of blood from the top two heart chambers (atrial depolarization) into the bottom two chambers (ventricles). B) The QRS complex, which represents the blood being pushed out of the bottom two chambers (ventricles) into the lungs and the body. And lastly, C) The T wave, which is the filling of the atria (repolarization). The length of time from when the ventricles contract to the filling of the atria is the QT interval.

The sinoatrial node (SA node) is the body’s natural pacemaker and sets the rhythm and pace of the heartbeat. It is located in the upper right part of the heart (right atrium) and travels across and down to the lower part of the heart (ventricles). The electrical system of the heart muscle opens and closes ion channels of the cell, which allows particles (ions) to flow through into and out of the muscle cells. The ion flow makes the heart muscle contract and relax; thus controlling the flow of blood into and out of the heart. Long QT syndrome is a type of channelopathy; the ion channels of the heart muscle are not functioning properly, which causes the heart rhythm to be abnormal. Specifically, the time it takes the heart to recharge is delayed. Therefore, the QT interval is longer than normal.

Long QT syndrome is caused by a change in a gene that causes the passage way of charged ions (atoms that are positive or negative) into and out of cells to not work properly. This passage way is called a voltage-gated channel. The type of channel is based on the charged ion it allows into or out of the cell. This causes the heart rhythm to be delayed, which can cause sudden death, fainting, and an arrhythmia. There are various different genes that are associated with the ion channels. The different types of long QT syndrome differ based on the gene that is affected.

Long QT syndrome type 1 is associated with pathogenic variants in the KCNQ1 gene which codes for one of the subunits that produces the potassium voltage-gated channel. Specifically, it affects the subfamily KQT member 1, which is part of the alpha subunit forming the ion channel. This ion channel moves positively charged atoms of potassium out of the cells. The movement of the positive potassium ions out of the cell plays a role in the heart’s ability to create its rhythm.

Long QT syndrome type 2 is associated with pathogenic variants in the KCNH2 gene, which codes for one of the subunits that produces the potassium voltage-gated channel. Specifically, it affects the subfamily H member 2, which is part of the alpha subunit forming the ion channel. The movement of the positive potassium ions out of the cell plays a role in the heart’s ability to create its rhythm.

Long QT syndrome type 3 is associated with pathogenic variants in the SCN5A gene, which codes for one of the subunits that produces the sodium channel. Specifically, it affects the protein type V alpha subunit of the sodium channel. This channel helps control the flow of positively charged sodium ions into cells. The movement of the positive sodium ions into cells plays a role in the heart’s ability to create its rhythm.

Long QT syndrome (LQTS) is an inherited condition that affects the heart’s rhythm and delays the time it takes for the heart to recharge between beats. These rhythm changes lead to the main symptoms seen in LQTS. The elongation of the QT interval can cause a fast heartbeat (tachycardia), which typically occurs in the ventricles (ventricular tachycardia). Ventricular tachycardia is associated with a finding on ECG called "Torsade de Pointes" which are self-terminating and causes fainting (syncope) and sometimes a disorganized heart rhythm in the ventricles (ventricular fibrillation). Ventricular fibrillation prevents blood flow (cardiac arrest) and may result in sudden death.

An individual living with long QT syndrome (LQTS) that has disease causing changes (pathogenic variants) in two different genes can be diagnosed with two types of LQTS. Since this means that there is then two different ways the heart rhythm is being affected, it often leads to more severe LQTS with a longer QT level and increased chance of cardiac events.

In one specific case, when an individual has both LQTS type 1 caused by a mutation in the KCNQ1 gene and type 5 long QT syndrome caused by a mutation in the KCNE1 gene. When disease causing mutations are found in at least one copy of these genes at the same time in the same person (compound heterozygote state) it causes autosomal recessive LQTS with profound sensorineural deafness. If an individual inherits just one of these gene mutations in a single gene, they would have autosomal dominant LQTS, but if they have both mutations it adds the hearing loss symptom. This is a condition called Jervell and Lange-Nielsen syndrome.

Individuals with long QT syndrome who have had genetic testing where a disease-causing variant in one of the genes associated with long QT syndrome has been identified, the option for prenatal testing is available. Prenatal testing, or prenatal diagnosis, allows for the diagnosis of long QT syndrome in the developing baby. The genetic testing will test DNA from the developing baby for the specific disease-causing variant identified as a the cause of long QT syndrome in the family member (i.e. the mother or father of the developing baby).

Prenatal diagnosis during pregnancy can be done by two different procedures, depending on how far along the pregnancy is (the gestational age of the pregnancy). The results obtained from either procedure are the same, but the earlier the procedure, the earlier the results are available.

During the first trimester, between 11 and 13 weeks of pregnancy, pregnant women can decide to pursue the prenatal diagnostic procedure called chorionic villus sampling (CVS). The chorionic villi is a part of the placenta. Since the placenta and the developing baby start from the same genetic material, being able to test part of the placenta will give us information about the genetic material of the developing baby. Therefore, CVS is a procedure that is ultrasound guided and a specially trained doctor, usually an obstetrician, will first identify the location of the placenta to determine from where to sample the placenta. The procedure can be done either through the abdomen "transabdominally" or through the cervix "transcervically", depending on the location of the placenta. CVS is an invasive procedure and has a risk of miscarriage. This risk of miscarriage varies on the hospital where the procedure is being performed, but typically a risk of 1% – 2% is given (1 in 50 – 1 in 100) to patients.

During the second trimester, after 16 weeks of pregnancy, pregnant women can decide to do a diagnostic procedure called amniocentesis. The amniotic fluid is fluid that surrounds the developing baby. It is made by the developing baby’s kidneys and the volume increases throughout the pregnancy. Floating within the amniotic fluid are the developing baby’s cells, which have the developing baby’s DNA. Therefore, the ability to obtain amniotic fluid allows us to test the baby’s DNA. Amniocentesis is also an ultrasound-guided procedure, where ultrasound identifies where the developing baby lies and a pocket of amniotic fluid. The obstetrician uses a needle to obtain approximately 2-3 tablespoons of amniotic fluid for genetic testing. It is also an invasive procedure and a risk of miscarriage is quoted, again dependent on the hospital where the procedure is being performed, but anywhere from 1 in 200 to 1 in 1000 (0.5% to 0.1%).

Once a sample from the developing baby (either chorionic villi or amniotic fluid), genetic testing can be initiated. Prenatal diagnosis for the familial disease causing variant in the gene associated with long QT syndrome will be done. There may be other genetic testing initiated at the same time. It is important to speak with your genetic counselor to ask what routine genetic testing is performed on the developing baby’s DNA. Some places may initiate chromosome testing for chromosome numbers 21, 18, 13, and the sex chromosomes (X and Y), in addition for familial gene variant testing for long QT syndrome. Abnormal chromosome number conditions (such as Down syndrome) are one of the more common sporadic genetic conditions that can happen in a pregnancy.

The results of the genetic testing of the developing baby could help families make decisions with regard to their pregnancy management. In other words, some families may decide to stop a pregnancy following a prenatal diagnosis [of long QT syndrome]. Some families may alter where they deliver their baby or seek out consultations with pediatric cardiologists to learn more about what to expect with newborns diagnosed with long QT syndrome.

Individuals suspected of having long QT syndrome will be required to complete multiple tests for a diagnosis of the condition, in addition to meeting with a cardiologists. The tests include imaging of the heart, measuring the heart’s electrical activity through an electrocardiogram (EKG/ECG), and genetic testing (typically a blood draw).

There are other names for long QT syndrome. Other names include:

There are many support and advocacy groups for Long QT syndrome. Some of them include:

Sudden Arrhythmia Death Syndromes Foundation
4527 South 2300 East, Suite 104
Salt Lake City, UT 84117-4448
https://www.sads.org/
Patient Support Line: 1-801-948-0654

Postal Address:

Arrhythmia Alliance (UK Based, International Group)
Unit 6B, Essex House, Cromwell Business Park
Chipping Norton
OX7 5SR
http://www.heartrhythmalliance.org
Email: info@heartrhythmalliance.org

Treatment for long QT syndrome (LQTS) is focused on treated and preventing life-threatening heart rhythms. An individual with LQTS should work closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information. For many individuals this may include taking medications such as a beta blocker or sodium channel blocker and possibly surgery to place an implantable cardioverter-defibrillator (ICD) and/or left cardiac sympathetic denervation (LCSD). It also includes avoiding medications, substances, and situations that lengthen the QT interval. It is extra important to have regular appointments checking on the effectiveness of the existing treatment plan and watching for other health issues, particularly during childhood when children may need frequent changes in medication dose as they grow. Having automatic external defibrillators available at home, at school, and activities or sports restrictions may be recommended by a doctor for some individuals with LQTS. For individuals who have types of LQTS that include other health issues such as developmental delays or hearing loss, experts in the symptom focused treatment should be sought in addition to heart focused treatments.

There is a process called risk stratification, which is a critical aspect of management in long QT syndrome in the prevention of sudden death. Accurate risk stratification can be challenging since LQTS is a very variable condition even within the same family; however, there are certain clinical and genetic markers that can facilitate risk assessment. Those are:

Pre-implantation genetic diagnosis or pre-implantation genetic testing – monogenic (also known as single gene) disorders "PGT-M" for long QT syndrome is theoretically available to individuals who have had genetic testing for long QT syndrome and a disease-causing change has been identified. The ability to offer this option to couples is dependent on several factors, such as: the type of disease-causing change, the other individuals in the family affected, and the number of embryos produced. There may be other factors that the genetic testing company uses to determine whether or not they could be successful in offering this test to patients.

In order to pursue pre-implantation genetic diagnosis, the process of in vitro fertilization (IVF) is required. IVF requires the woman to undergo stimulation of her ovaries to produce many eggs. This process is highly regulated by the fertility clinic the couple decides to work with. When there are many eggs, the woman has a procedure done to retrieve the eggs. In the lab, embryos are made by combining one sperm with one egg (fertilization). After day 5 of fertilization, the embryo is ready to be tested. At this stage, the embryo is called a blastocyst. There are approximately 100-200 cells in the embryo and the embryo is growing into a part that becomes the placenta (trophectoderm) and the developing baby (inner cell mass). Cells from the trophectoderm are biopsied at this stage. Approximately 5-10 cells are retrieved from the embryo at this time. Genetic testing can be performed on the DNA from the cells retrieved. Since the amount of DNA retrieved is much less than we would obtain from a blood sample or a prenatal diagnostic test (chorionic villus sampling or amniocentesis), the testing for long QT syndrome or other genetic testing is much more difficult. Therefore, the lab that does PGT-M creates a special platform (technique) to test the embryo for each family they work with.

Once the embryos are tested, the embryos that do not have the long QT familial variant can be transferred to the patient and if implantation is successful, the patient becomes pregnant. The embryos that do have the long QT familial variant are then discarded (destroyed).

Couples who are interested in learning more about their options for family planning can request an appointment with a genetic counselor who specializes in preconception genetic counseling or prenatal genetic counseling by either being referred by a health care provider or by searching for one through the National Society of Genetic Counselors’ website: find a genetic counselor.

In cases where long QT syndrome is being referred to as acquired, what is typically meant by that, is a person may be taking a medication that prolongs the QTc interval on an electrocardiogram. Having "acquired" long QT syndrome does not necessarily mean that a person has a gene change that is passed on in the family that predisposes them to having a longer QT interval. There are many medications that cause a person to have a longer QTc interval and can cause problems with repolarization.
The major classes of drugs that prolong the QT interval include:

Individuals living with long QT syndrome (LQTS) should work closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information. For some individuals, their doctors will recommend surgery to place an implantable cardioverter-defibrillator (ICD). Although every patient is different, the main recommendation is that ICDs be placed in people with LQTS who have been resuscitated after a cardiac event, people who can’t take beta blocker medications, or individuals whose symptoms aren’t being helped enough by beta-blocker medications.

Long QT syndrome is a rare genetic condition. The incidence is approximately 1 in 2500. This number may not be accurate as not all individuals with a pathogenic variant in one of the genes associated with long QT syndrome will have signs or symptoms.

The standard QT or QTc interval on electrocardiogram (ECG) is less than 440 msec for an average person. People with long QT syndrome (LQTS) have a QTc range from around 400 to 600+ msec. The QTc length is a little longer on average for LQTS type 3 at 490 msec as compared to LQTS types 1 and 2 at 480 msec. When treating an individual for LQTS, the goal is to bring the QTc length back into the normal range, often using beta-blockers in order to reduce the overall risk of fainting, cardiac events, or other symptoms.

The Sudden Arrhythmia Death Syndromes (SADS) Foundation website has a lot of good information for individuals preparing for their appointment with the doctor and good questions to ask especially if it is their first appointment. Click this link to see the list of very helpful suggestions.

There are multiple ways to meet and talk with other living with long QT syndrome (LQTS) including:

Different types of long QT syndrome (LQTS) have different overall treatment, monitoring, and prevention recommendations. For example, individuals with LQTS type 3 most often have cardiac events during sleep which requires a different type of monitoring and preventive measures than those with LQTS type 1 in which cardiac events are mostly triggered by exercise. In addition, treatment plans for individuals who have types of LQTS that include other health issues such as developmental delays or hearing loss, should include healthcare experts who can recommend symptom focused treatment in addition to heart focused treatments.
In all forms of LQTS, treatment is focused on treated and preventing life-threatening heart rhythms. For many individuals this may include taking medications such as a beta blocker or sodium channel blocker and possibly surgery to place an implantable cardioverter-defibrillator (ICD) and/or left cardiac sympathetic denervation (LCSD). It also includes avoiding medications, substances, and situations that lengthen the QT interval. It is extra important to have regular appointments checking on the effectiveness of the existing treatment plan and watching for other health issues, particularly during childhood when children may need frequent changes in medication dose as they grow. Having automatic external defibrillators available at home, at school, and activities or sports restrictions may be recommended by a doctor for some individuals with LQTS.
Having said this, LQTS treatment and management is very personalized and designed for the individual living with LQTS by working closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information.

While people living with Long QT syndrome (LQTS) can be different and/or have differing geneotypes of LQTS which can affect the outcomes and triggers of cardiac events, it is generally recommended by physicians that patients with LQTS be allowed the opportunity to participate in sports activities as long as they are compliant with therapy, maintain proper hydration and electrolyte status, and have access to an automated external defibrillator (AED). Furthermore, it is stressed that people with LQTS who choose to participate in sports be properly screened prior to initial participation and then monitored regularly thereafter especially in symptomatic patients. Avoidance of QT-prolonging drugs is also important for LQTS patients participating in sports activities.

Women with long QT syndrome have a reduced risk for cardiac events during pregnancy, but an increased risk during the 9-month postpartum period, especially among women with the LQT2 genotype. Beta-blockers were associated with a reduction in cardiac events during the high-risk postpartum time period.

Not all people who have a gene change (pathogenic variant) in a Long QT syndrome (LQTS) disease causing gene will have a longer QT interval or even have symptoms. This explains why it may appear that there is no family history of LQTS when someone is diagnosed unexpectedly through a cardiac event. Studies have shown that the rate of people with a pathogenic variant who have normal QT intervals (a QTc level of <440 msec) on ECG and/or have cardiac events are different depending on LQTS type. Specifically:

Adult men have shorter QTc intervals than women. This gender difference is absent at birth and in young children. Throughout puberty, the QTc interval in males shortens by 20 msec, whereas the QTc of females remains unchanged, resulting in a 6% shorter QTc in males compared to females. With aging, the QTc in men gradually lengthens and approximates that of women by the age of 50. This suggests that gender differences exist in the QTc interval.

Studies of normalization of the QT interval with testosterone therapy in hypogonadal men support a QT shortening effect of testosterone replacement therapy.

To date, there are no studies on oral contraception (OC) and long QT syndrome and how OC affects the QT interval. Future research is needed.

Studies of menopausal hormone therapy (MHT) in the form of estrogen-alone therapy (ET) and estrogen plus progesterone therapy (EPT) have suggested a counterbalancing effect of exogenous estrogen and progesterone on QT intervals. Specifically, ET lengthens the QT, whereas EPT has no effect.

Individuals with long QT syndrome (LQTS) can reduce risks to themselves and their baby by having children under the careful monitoring of their cardiologist and high risk OB/Gyn during pregnancy and in the months after the baby is born. Studies have found that women with LQTS have a reduced risk for cardiac events during pregnancy, but an increased risk for events during the time after the baby is born (the postpartum period). This risk is higher in women living with the LQTS type 2. Women treated with beta-blockers by their doctor did have less cardiac events during the high-risk postpartum time period. Individuals with LQTS should also consider genetic counseling prior to pregnancy so that they can discuss the chance of passing on LQTS to the children and any testing options for learning if the baby is affected before or after birth.

Registries are a form of long term research in which information on individuals living with long QT syndrome (LQTS) provide information about specific types of LQTS, medical symptoms, and health changes over many years to help doctors and researchers learn more about LQTS and the impact of specific treatments. The main LQTS registry designed to under better understand LQTS is run by the University of Rochester Heart Research Follow-up program. To learn about participating they can be contacted at:

International Long QT Syndrome Registry
Heart Research Follow-Up Program
Box 653
Rochester NY 14642-8653
Phone: 585-276-0016
Fax: 585-273-5283
Email: heartajm@heart.rochester.edu

Considering the substances of abuse, to our knowledge, at least methadone, cocaine, 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and alcohol can induce changes in the QT/QTc interval and could enhance the risk of ventricular arrhytmia in people with long QT syndrome. Many reports have described atrial fibrillation, ventricular tachycardia, acute coronary syndromes, and cardiac arrest related to marijuana use. The cardiac arrhythmogenicity of various opioids is different. Methadone has a higher capability to induce long QT interval and dangerous arrhythmias in conventional doses than others. To reduce of arrhythmogenic risk, high doses of opioids must be used cautiously with periodic monitoring of ECG in high-risk consumers such as patients under opioid maintenance treatment. There is increasing evidence that cannabinoids can alleviate chronic pain and, in one study performed in healthy volunteers, an oral mucosal spray containing delta-9-tetrahydrocannabinol/cannabidiol had no significant effect on ECG parameters, either in recommended or in supra-therapeutic doses. However, in vivo experiments for JWH-030, a new synthetic cannabinoid, demonstrated blocking of the hERG channel and therefore the potential for QT interval prolongation.

The exception to autosomal dominant inheritance in long QT syndrome can be found in a unique situation when an individual has both LQTS type 1 caused by a mutation in the KCNQ1 gene and type 5 long QT syndrome caused by a mutation in the KCNE1 gene. When disease causing mutations are found in at least one copy of these genes at the same time in the same person (compound heterozygote state) it causes autosomal recessive LQTS with profound sensorineural deafness. If an individual inherits just one of these gene mutations in a single gene, they would have autosomal dominant LQTS, but if they mutations in both genes it adds the hearing loss symptom.

Long QT syndrome (LQTS) is an inherited condition that affects the heart’s rhythm and delays the time it takes for the heart to recharge between beats. These rhythm changes lead to the main symptoms seen in LQTS. When looking at other conditions that may look like LQTS it can be divided out by symptoms and features of LQTS. For example, there are several non genetic causes of long QT interval in people who do not have LQTS. These can include:

A prolonged long QT interval can be associated with genetic and non-genetic causes. Non-genetic causes of a prolonged QT interval or acquired long QT syndrome can be caused by sensitivity to medications, which include several drug classes – antiarrhythmics, antimicrobials, antidepressants, phenothiazines, opiates, prokinetics of digestive tract to name a few).

Different types of Long QT syndrome (LQTS) have different overall treatment, monitoring, and prevention recommendations. That means that the lifestyle modifications recommended may vary by the type and symptoms of LQTS you currently have impacting your health. For example, many individuals with LQTS type 1 will be told to avoid unsupervised swimming or strenuous exercise while for those living with LQTS type 2, the recommendation would be to reduce exposure to loud, sudden noises like alarm clocks or fire alarms. Individuals of any type of LQTS who have had a cardiac arrest may have restrictions on competitive sports like football, but not everyone with LQTS will require those restrictions. In some cases, having automatic external defibrillators available at home, at school, and activities or sports restrictions may be recommended by a doctor. It is important to discuss recommended limitations and precautions with a heart doctor familiar with LQTS and the individual’s specific health issues. Regular appointments with the doctor checking on the effectiveness of the existing treatment plan and watching for other health issues may also help your medical team modify or change lifestyle restrictions. LQTS lifestyle changes are very personalized and designed for the individual living with LQTS and working closely with a heart doctor who is experienced with LQTS and able to advise, monitor, and treat the condition with the most up-to-date information is important.

Family members of individuals who have been diagnosed with long QT syndrome, specifically your first degree relatives (children, parents, siblings), are at a 50% chance of also having Long QT syndrome. Individuals or family members who are concerned about their family history of long QT syndrome and its implications for their health, can speak with a genetic counselor by either being referred by a health care provider or by searching for one through the National Society of Genetic Counselors’ website: find a genetic counselor.