Long QT syndrome

Long QT syndrome (LQTS) is a condition which affects repolarization of the heart after a heartbeat. It results in an increased risk of an irregular heartbeat which can result in palpitations, fainting, drowning, or sudden death. These episodes can be triggered by exercise or stress. Other associated symptoms may include hearing loss.Ankyrin: Long QT syndrome 4 Long QT syndrome (LQTS) is a condition which affects repolarization of the heart after a heartbeat. It results in an increased risk of an irregular heartbeat which can result in palpitations, fainting, drowning, or sudden death. These episodes can be triggered by exercise or stress. Other associated symptoms may include hearing loss. Long QT syndrome may be present at birth or develop later in life. The inherited form may occur by itself or as part of larger genetic disorder. Onset later in life may result from certain medications, low blood potassium, low blood calcium, or heart failure. Medications that are implicated include certain antiarrhythmic, antibiotics, and antipsychotics. Diagnosis is based on an electrocardiogram (EKG) finding a corrected QT interval of greater than 440 to 500 milliseconds together with clinical findings. Management may include avoiding strenuous exercise, getting sufficient potassium in the diet, the use of beta blockers, or an implantable cardiac defibrillator. For people with LQTS who survive cardiac arrest and remain untreated, the risk of death within 15 years is greater than 50%. With proper treatment this decreases to less than 1% over 20 years. Long QT syndrome is estimated to affect 1 in 7,000 people. Females are affected more often than males. Most people with the condition develop symptoms before they are 40 years old. It is a relatively common cause of sudden death along with Brugada syndrome and arrhythmogenic right ventricular dysplasia. In the United States it results in about 3,500 deaths a year. The condition was first clearly described in 1957. Many people with long QT syndrome have no signs or symptoms. Symptoms that do occur are generally caused by abnormal heart rhythms or arrhythmias, most commonly a form of ventricular tachycardia called Torsades de pointes. If the arrhythmia reverts to a normal rhythm by itself then the affected person may experience a faint known as syncope, which may be associated with seizures. However, if the arrhythmia continues, the affected person may experience a cardiac arrest leading to sudden death. The arrhythmias that lead to faints and sudden death are more likely to occur in response to specific circumstances, in part determined by which genetic variant is responsible for the condition. While arrhythmias can occur at any time, in some forms of LQTS arrhythmias are more commonly seen in response to exercise or mental stress (LQT1), in other forms following a sudden loud noise (LQT2) , and in some forms during sleep or immediately upon waking (LQT3). Some rare forms of long QT syndrome are associated with symptoms affecting other parts of the body. These include deafness in the Jervell and Lange-Nielsen form of the condition, and periodic paralysis in the Andersen-Tawil (LQT7) form. While those with long QT syndrome have an increased risk of developing abnormal heart rhythms compared to those without the condition, the absolute risk of arrhythmias is very variable. The strongest predictor of whether someone will develop torsades de pointes (TdP) is whether they have experienced spontaneous TdP or another form of cardiac arrest in the past. Even if an arrhythmia has not been witnessed, a person with LQTS who has experienced syncope is also at higher risk, as syncope in these cases is frequently due to an undocumented self-terminating arrhythmia. In addition to a history of arrhythmias, the QT interval predicts risk. While some with LQTS will have QT intervals that are very prolonged, others will have only slight QT prolongation, or even a normal QT interval at rest (concealed LQTS). Those with the longest QT intervals are more likely to experience TdP, and a corrected QT interval of greater than 500 ms is thought to represent those at higher risk. Despite this, even those with subtle QT prolongation or concealed LQTS still have some risk of arrhythmias. Overall, every 10 ms increase in the corrected QT interval is associated with a 5% increase in arrhythmic risk.