Long QT Syndrome
Long QT syndrome (LQTS) is a heart electrical disorder that is inherited. This heart rhythm disorder can potentially cause very fast heartbeats called Torsades de Pointes (ventricular fibrillation). This genetic disorder produces alteration in the exchange of ions at the cardiac cellular level. The electrocardiogram usually shows prolongation of the QT interval (relaxation phase in the cardiac cycle).
Patients with LQTS are prone to rapid heartbeats which may lead to fainting and, in some cases, the heart may beat so erratically that it can cause sudden death.
Long QT syndrome is considered a congenital heart electrical disorder with an incidence of 1:200,000. Almost half of the patients have a positive family history for the same disorder. About 75% of patients with LQTS will show a genetic mutation.
About half of the patients with LQTS do not have any symptoms. They may be aware of their condition because of a positive genetic test, abnormal electrocardiogram or family history of LQTS. The most common symptoms are:
Fainting. This is the most common symptom of LQTS. In LQTS, syncope is caused by the heart beating in a very erratic way. The fainting spells may occur abruptly or when the child is excited, scared, angry, during exertion or after hearing a loud noise. Fainting usually occurs without warning., such as losing consciousness after being scared by a friend.
Palpitations (irregular heartbeats). You may feel a fluttering sensation in your left chest. This may be accompanied by lightheadedness, dizziness or fainting.
Seizures. Some patients are misdiagnosed with epilepsy while the real reason for their seizure is an arrhythmia such as Torsades de Pointes or sinus arrest. If the heart continues to beat erratically the brain becomes deprived of oxygen and this may produce generalized seizures.
Sudden Death. This is usually preceded by syncope. The heart rate is usually fast and very erratic. In Long QT the heart usually returns back to a normal rhythm. If this does not happen spontaneously and help is not granted sudden death is likely to occur. Most deaths occur in people ages 11-30.
Symptoms may start during infancy, menarche, young adulthood or middle age. Rarely, symptoms of LQTS occur during sleep or arousal from sleep.
Most patients with the Long QT syndrome will have prolongation of the QT interval in the electrocardiogram. There are other EKG abnormalities that help in risk stratification such as T wave alternans, 2:1 AV block, sinus bradycardia, sinus arrest and others. The electrocardiogram may also help in determining the sub-type of Long QT syndrome but genetic testing is the “gold standard” test. A 24-hour Holter is performed to check for the above EKG findings as well as other arrhythmias including premature ventricular contractions, ventricular tachycardia, Torsades de Pointe (ventricular fibrillation) and others. Stress testing is performed on the older child as part of the electrophysiology work-up.
This electrical disorder is not correctable. Most patients will require cardiac medications such as beta-blockers. The medication reduces the risk of sudden death by over 50%. Mortality rate is between 0.4 to 1% per year; but it may be higher depending on the sub-type of Long QT syndrome.
Many patients with LQTS may benefit of a high potassium diet. In some patients potassium may be given by Dr. Villafañe. It depends on the sub-type of LQTS. A left-sided sympathetic ganglionectomy is performed in the rare cases in which the patient is refractory to medical treatment, in those who develop symptoms or those with electrical storms. This is a surgery where specific nerves in your chest are surgically cut. This surgery is usually reserved for patients considered at high risk of sudden death.
Some patients may require implantation of a pacemaker while others may need an internal automatic cardiac defibrillator. Dr. Villafañe usually recommends to have an external cardiac defibrillator available in case there is an emergency requiring CPR. Availability of an external cardiac defibrillator may be life-saving.
Most patients with Long QT syndrome may lead a relatively normal life. Patients with LQTS are restricted from competitive sports or strenuous exercise (with very few exceptions). There are some activities such as swimming and aerobic sports which may trigger an arrhythmia. Patients with LQTS should avoid auditory stimuli such as an alarm going off, loud telephone ring, emotional outbursts or being scared (such as going to a haunted house).
Over 10% of infants who suffer Sudden Infant Death syndrome (SIDS) may have a gene mutation for LQTS. Patients who are not compliant with their medical treatment are at a much higher risk of developing symptoms arrhythmia and, unfortunately, sudden death.
There are many medications that need to be avoided in patients with LQTS as they may trigger a serious arrhythmia such as ventricular fibrillation/Torsades de Pointes. For a comprehensive listing please go to www.qtdrugs.org. Some patients with a cardiac defibrillator may have recurrent electrical shocks by the defibrillator (if they go into Torsades de Pointes). This is called an electrical storm and is a serious problem; sometimes very hard to treat. Psychological counseling should be strongly considered in patients with LQTS.
Prolonged fasting should be avoided in patients with beta-blockers as this may mask hypoglycemia (low blood sugar) and result in significant symptoms including seizures. You should call 911 in case of syncope, seizures or sudden cardiac arrest. Dr. Villafañe recommends CPR training in all the immediate family members.
Patients with LQTS may be followed by a pediatric cardiologist who is familiar with this syndrome. Many of the LQTS patients are followed by a cardiac electrophysiologist such as Dr. Villafañe. Electrical disorders have been an area of clinical research for Dr. Villafañe. Most of our patients are on cardiac medications and only a few have a pacemaker or defibrillator.
You should make your friends and family members aware of your condition. Emergency bracelets and necklaces are available from many sources, a few of them appear in our website.
For more information please go to www.qtsyndrome.ch or www.qtdrugs.org.