heart and blood vessel disorders
Long QT Interval Syndromes
Introduction
The long QT interval syndromes are disorders of the heart's electrical activity that predispose people to dangerous heart rhythms and sudden death. People may be born with an abnormality that causes long QT interval or they may develop it as a complication of other disorders. People are at risk for Torsades de Pointes Ventricular Tachycardia , which may stop on its own or degenerate into Diagnosis is by electrocardiography (ECG). Treatment is avoidance of triggers, use of beta-blockers, and sometimes an implantable cardioverter-defibrillator (ICD). (See also Overview of Abnormal Heart Rhythms and The QT interval refers to the time between two events on the electrocardiogram (ECG)—from the beginning of the Q wave to the end of the T wave. Any abnormality that prolongs the QT interval increases the risk of a rapid, dangerous heart rhythm called Torsades de Pointes Ventricular Tachycardia (torsades). Ventricular tachycardia is a heart rhythm that originates in the ventricles (lower chambers of the heart) and produces a rapid heart rate. Torsades often turns into An electrocardiogram (ECG) represents the electrical current moving through the heart during a heartbeat. The current's movement is divided into parts, and each part is given an alphabetic designation in the ECG. Each heartbeat begins with an impulse from the heart's pacemaker (sinus or sinoatrial node). This impulse activates the upper chambers of the heart (atria). The P wave represents activation of the atria. Next, the electrical current flows down to the lower chambers of the heart (ventricles). The QRS complex represents activation of the ventricles. The ventricles must then undergo an electrical change to get ready for the next heart beat. This electrical activity is called the recovery wave, which is represented by the T wave. Many kinds of abnormalities can often be seen on an ECG. They include a previous heart attack (myocardial infarction), an abnormal heart rhythm (arrhythmia), an inadequate supply of blood and oxygen to the heart (ischemia), and excessive thickening (hypertrophy) of the heart's muscular walls. Certain abnormalities seen on an ECG can also suggest bulges (aneurysms) that develop in weaker areas of the heart's walls. Aneurysms may result from a heart attack. If the rhythm is abnormal (too fast, too slow, or irregular), the ECG may also indicate where in the heart the abnormal rhythm starts. Such information helps doctors begin to determine the cause. The term "long QT" refers to an abnormal pattern of electrical activity that is seen on an electrocardiogram (ECG). 