heart and blood vessel disorders
Torsades de Pointes Ventricular Tachycardia
Introduction
Torsades de pointes ventricular tachycardia is a specific type of Ventricular Tachycardia that occurs in people who have a particular disorder of the heart's electrical activity called a long QT interval. 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. (See also Overview of Abnormal Heart Rhythms and 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. Any abnormality that prolongs the QT interval increases the risk of a dangerous heart rhythm called torsades de pointes ventricular tachycardia. Some people are born with a genetic abnormality that causes a long QT interval (called Long QT Interval Syndromes ). In other people, the long QT interval results from low serum levels of potassium ( Ventricular Tachycardia is a heart rhythm that originates in the ventricles (lower chambers of the heart) and produces a rapid heart rate. People with a long QT interval may develop a particular form of ventricular tachycardia called torsades de pointes ventricular tachycardia (torsades). Torsades has a characteristic appearance on the electrocardiogram (ECG) and often turns into Sometimes, exercise brings on the ventricular tachycardia (see Sudden Cardiac Death in Athletes ). Other factors that increase the risk of torsades include female sex, older age, an underactive thyroid gland ( 