Long QT syndrome (LQTS) is a disease that you can inherit or acquire. It affects the bottom pumping chambers of the heart (ventricles). It can cause a dangerous rapid heart rate and abnormal rhythm.
The heart has both muscular and electrical components. When electricity flows through the heart muscle, it is triggered to squeeze or beat. Heart muscle cells use highly coordinated ion channels to regulate the flow of electricity to generate normal heartbeats. Ion channels are what the electrolytes potassium, sodium, and calcium flow through within the heart's cells. In LQTS, a problem in the ion channels leads to electrical instability. This can cause a very rapid and dangerous heart rhythm that can lead to fainting or sudden death. The arrhythmias are called ventricular tachycardia or ventricular fibrillation.
The name long QT stems from a reading on the electrocardiogram (ECG) machine. Healthcare providers use this to evaluate your heartbeat. The ECG machine records and measures each of your heartbeats as 5 “waves.” Each wave has a different letter designation: P, Q, R, S, and T. The relationship between the Q and T waves is important and is known as the QT interval. When the interval lasts longer than it normally should, it disrupts the timing of your heartbeat and can cause dangerous arrhythmias, or irregular heart rates.