Long QT Syndrome 

Long QT Syndrome Long QT syndrome is often difficult for patients and their families to understand. This patient/family educational document was created to answer commonly asked questions about this complex and sometimes confusing problem. Please keep in mind that our knowledge of long QT syndrome is constantly changing and interpretation of new information may vary even among cardiologists. Please feel free to contact us for further questions. What is long QT syndrome? Long QT syndrome is a heart disorder that is associated with sudden unexpected fainting (loss of consciousness), seizures (convulsions), or death. The “QT” refers to the QT interval, which is a time found on a standard electrocardiogram (EKG or ECG). An EKG is a recording of the electrical activity of the heart. On the EKG doctors measure several intervals. The QT interval includes the time that the heart muscle relaxes. Because people have different heart rates, the measured interval is corrected for heart rate by a mathematical formula and the result is called the corrected QT interval (often depicted by QTC or QTc). The normal QTc was thought to be 0.44 second or less. It is now thought that a QTc greater than 0.46 in males, 0.47 in females, is prolonged. However, we now know that some individuals can have a normal QTc at times and abnormal at others. To have the “syndrome” other factors such as severe symptoms and family history are used to help make the diagnosis. Many causes of long QT interval exist, such as medications, low potassium, magnesium or calcium in the blood, and abnormal heart muscle, to name a few. Long QT syndrome is different. People who have long QT syndrome usually inherit the condition from relatives and have it from birth. Therefore, long QT syndrome is congenital (present at birth) and usually is hereditary (present in relatives). How is long QT syndrome inherited? During the past several years’ time, genetics research and investigation have shown that gene/chromosome abnormalities are inherited in many but not all families. The investigations have shown new findings. In the past, it was thought that one or two abnormalities caused the long QT syndrome. Now, it has been proven that several different gene abnormalities on different chromosomes can make the QT long. For example, it has been found that one family may have an abnormal gene called the KVLQT1 inherited on chromosome 11, while another family may have a different abnormal gene called SCN5A inherited on chromosome 3. While several different types of abnormal genes have been identified, scientists and physicians are predicting several more may be identified in the future. Because the research involves complicated newly developed molecular genetic techniques and expertise, Long QT Syndrome genetic testing is only done on a research basis, so it is not commercially available. Also, because the research is so new, many questions and details involving inheritance remain unknown. This includes the pattern of inheritance in different families. However, it appears that most people with a family history of long QT syndrome have an inheritance pattern called autosomal dominant. This means that there is a 50 percent chance of inheriting the abnormal gene and it is unrelated to sex/gender. It is known, however, that people with a long QT interval may be affected differently within the same family. Details as to the reasons and what the differences mean to the various family members are not fully known at this time. Therefore, much more genetic research needs to be done. How common is the long QT syndrome? The incidence of long QT syndrome is unknown, but has been estimated to be approximately one in 50,000 people. However, the syndrome is frequently unrecognized, even by physicians. What are the symptoms of long QT Syndrome? Many people with congenital long QT syndrome do not have any symptoms. These people often become aware that they have the problem when an EKG is done as part of an evaluation because a family member is suspected of having the syndrome. In people who have symptoms, the most common ones are fainting (sudden loss of consciousness) and/or seizures (convulsions). Occasionally, the first sign may be a cardiac arrest or sudden death. Symptoms are more common during or after exercise, during recreational swimming and after being startled (for example, by a loud noise). Symptoms also may occur during sleep or upon awakening from sleep. How and why do symptoms occur? Symptoms occur when the heart suddenly is unable to pump blood to the brain and other organs of the body. This is usually due to a condition called ventricular tachycardia or ventricular fibrillation. Ventricular tachycardia is a form of very fast heart rate from an area within one of the two ventricles (ventricles are the lower chambers of the heart). When ventricular tachycardia occurs in people with a long QT interval, it is often referred to by a French term, torsade de pointes. Ventricular fibrillation is an unorganized, chaotic, very fast heart rhythm also from the ventricles. During each of these abnormal heartbeats or rhythms (also called arrhythmias), the heart is unable to effectively pump blood to the body. When the brain does not receive blood, consciousness is lost and/or seizures develop. If the arrhythmia stops and the normal heart rate and rhythm return, then symptoms disappear. If the arrhythmia continues for several minutes or longer, a cardiac arrest or sudden death occurs. The reason for the increased risk of developing ventricular tachycardia and fibrillation is not fully known, but it is related to the presence of the long QT interval. Loss of consciousness also may develop when a very slow heart rate occurs. Some people with Long QT Syndrome have a slow heart rate and therefore occasionally symptoms may develop when the heart rate slows or when the heart stops beating for several seconds. Who is most likely to develop symptoms? People who have long QT Syndrome are more likely to develop symptoms (including sudden death) if they have one or more of the following characteristics: personal history of, fainting, seizures, or cardiac arrest; deafness; a QTc of 0.55 second or longer; associated with other certain syndromes. However, symptoms may develop regardless of whether or not a person has any of these characteristics. What causes the QT interval to be long? The cause of the long QT interval is not fully known. It is known that the heart valves work normally, the heart pumps blood normally, and that autopsies done on people who have died show no abnormalities. The new genetic research has shown that different abnormalities in different people can cause the QT interval to be long. It appears that the problem is caused by abnormal genes on the chromosomes that ultimately make the flow of salts such as potassium or sodium into or out of the heart muscle cells abnormal, so that the resting or repolarization phase (QT) of the electrical impulse of the heart is too long. In one family, it may be a potassium long QT problem, while in another family it may be a sodium long QT problem. Other problems may be discovered with further research. How is the diagnosis of long QT syndrome made? How does a person know if he/she really has long QT syndrome? The diagnosis of long QT Syndrome is made when one or more of the following characteristics are present: QTc on ECG of 0.46 second or longer in males and 0.47 second or longer in females; family history of long QT; all other causes of increased QT interval are excluded; personal history and/or a family history of unexplained fainting, seizures, cardiac arrest or sudden death (including sudden infant death syndrome). When a family history of a measured long QT interval cannot be documented, other findings support the diagnosis of long QT syndrome. These include congenital nerve deafness; a slow heart rate; family history of congenital nerve deafness; and family history of congenital deafness. 2
For a variety of reasons, sometimes the diagnosis is borderline and further tests may be helpful such as a 24‐hour tape recording of the heart rate and rhythm (also called Holter monitor recording), an exercise test (treadmill or bicycle) or epinephrine challenge test. Can the QT interval change with age? In some people, the QT interval does shorten with age and may even become normal. If this occurs, it is most likely after adolescence. Presently, we cannot predict in which individuals the QT interval may shorten or normalize. Also, we do not know if the shortening or normalization of the QT interval results in a lower risk of serious symptoms. When the diagnosis of long QT syndrome is made, which family members/relatives should have an EKG done? In most families, an EKG probably has already been done in brothers, sisters, parents and children because this information is essential in making the diagnosis of congenital long QT syndrome. However, if not already done, these family members should undergo EKG testing. For more distant relatives, anyone who has had symptoms of dizziness, fainting, seizures or cardiac arrest should undergo EKG testing. If distant relatives have no symptoms, EKG testing can be individualized according to the recommendations of their cardiologist and according to the relatives’ desires. Should certain medications be avoided if you have the long QT Syndrome? Many medications can prolong the QT interval and people with long QT Syndrome may be particularly susceptible to the associated serious side effects of these medications. As a general rule, people with long QT Syndrome should ask their doctor about taking any over‐the‐counter medication. In addition, they should inform their physician of their condition whenever medication is prescribed for a medical disorder. In brief, patients with the long QT syndrome should avoid all medications that could prolong the QT interval. A list of drugs that should be avoided is maintained on the website www.QTdrugs.org. This list of drugs changes frequently, so it is a good idea to check the list whenever a medication is considered by someone with a long QTc or sometimes with a borderline long QTc. People with long QT Syndrome should always pay attention to the salt balance in the blood, because low potassium, low calcium, and low magnesium are conditions that prolong the QT interval. Therefore, nutrition is very important and any plans for dieting should be discussed with your doctor. Also diuretics, most of which can lower potassium, should be avoided. What is the treatment for long QT syndrome? The aim of treatment is to prevent symptoms and sudden death. The choice of treatment is based on the presence or absence of symptoms, as well as on the type of symptoms and the degree of sudden death in family members. For patients with minimal or no symptoms, the first choice of medicine usually is a beta blocker. Several beta blocker medicines are acceptable to use. The most commonly used beta blocker for congenital long QT syndrome patients is propranolol. Beta‐blockers or propranolol is effective in preventing symptoms in approximately 80 percent of people with long QT syndrome. Although most people do not have intolerable side effects from propranolol, occasionally severe sleep disturbance, mental depression, poor school performance, or impotence may require changing to a different beta‐blocker medication. Experience is limited with other beta‐blockers. However, experience in the registry suggests that nadolol (Corgard) is an acceptable alternative. atenolol (Tenormin) may not be a good alternative in young people. Sometimes propranolol or nadolol are not effective, or the specific type of problems suggests that another medication should be used. Examples include mexiletine (Mexitil). 3
When a slow heart rate is found, medication may cause further slowing and a pacemaker may be needed. The treatment combination of medication and a pacemaker provides an attempt to protect against the fast heart rate (ventricular tachycardia and ventricular fibrillation) and the slow heart rate. The most aggressive treatment option is to implant a device called an internal automatic cardioverter‐defibrillator (ICD). In the same device, a pacemaker is included. This option is usually considered when the patient has been resuscitated from a cardiac arrest or has had symptoms suggesting a life‐threatening event. The device contains a sophisticated computer. When the life‐threatening fast heart rate ventricular tachycardia fibrillation occurs, the device recognizes it and then responds by shocking the heart. Rarely, people require additional treatment such as surgery. The intent of surgery is to decrease the effect of adrenaline on the heart by cutting nerves in the spine area of the left neck. Do all people with the long QT syndrome need treatment? This question most often arises after EKG screening of relatives has been done and a few people without previously recognized symptoms are found to have a long QT interval. After the person is evaluated and tested, several things related to the severity of the problem are taken into account when considering treatment. For example, if the person has ever had unexpected or unexplained symptoms (fainting, seizures, cardiac arrest), then treatment may be recommended. If the person has never had symptoms but has a close relative (brother, sister, child or parent) who has had a cardiac arrest, then treatment is indicated. If a person without symptoms has a family history of sudden death or cardiac arrest in several distant relatives, treatment is usually recommended. The degree of QT interval length is also considered. Do people with borderline long QT syndrome need treatment? People with borderline long QT syndrome present a difficult problem for cardiologists because little information is available upon which to base treatment recommendations. In general, if a person has a QT interval of 0.43‐0.45 and has all of the other diagnosis criteria, then treatment may be recommended according to the discussion as outlined above. What are the side effects of beta blocker medications? Most people who take propranolol or other beta blockers do not have any side effects. Occasionally, people feel more tired (not sleepy), but usually this feeling improves and disappears after the first few weeks. Sleep disturbances can occur, such as nightmares or intense dreaming. People with asthma cannot take most beta blockers. Beta blockers can cause impotence in older men. Rarely, in school‐age children, school performance has decreased. Mental depression also can occur. In diabetics, beta blockers can mask some symptoms of hypoglycemia (low blood sugar in response to too much insulin). Beta blockers may interfere with interpretation of the glaucoma screen test. Do people with long QT syndrome need to be restricted from exercise? According to a national panel of experts, people with long QT syndrome should be restricted from participating in competitive sports.. Do women with long QT syndrome have special concerns during pregnancy? Limited information is available, but general experience suggests that normal pregnancy is likely. Careful and close follow‐up during pregnancy by the cardiologist and obstetrician is indicated. Beta blocker medications should be continued and careful monitoring of the baby should be carried out during and after birth for arrhythmias as well as for possible low blood sugar (from the beta blocker effect). Also, maternal monitoring should be performed during either normal vaginal or C‐section delivery. 4
What is the national long QT syndrome registry? Several years ago, a group of cardiologists from around the world decided to start a registry of people with the diagnosis of long QT syndrome. The registry, headed by Dr. Arthur Moss in Rochester, New York, has been helpful in providing statistics on many aspects of long QT syndrome. In this manner, treatment has improved and ongoing results continue to provide new information that proves valuable for people with long QT Syndrome. What is SADS? Several years ago, a national patient support group called Sudden Arrhythmia Death Syndromes Foundation was organized. Information is available at www.sads.org 5