What are the causes?

The immediate cause of SCA is an abnormality of the heart beat rhythm, or an arrhythmia. There are three types of arrhythmia that lead to SCA, namely, asystole, pulseless electrical activity (PEA) and ventricular fibrillation (VF). All of them are the result of an abnormality of the heart’s electrical system.

In asystole, the person’s electrocardiogram appears as a straight line. 

In pulseless electrical activity (PEA), the electrocardiogram shows some electrical activity of the heart but mechanically there is no output of blood flow from the heart.

In ventricular fibrillation (VF), the electrical activities of the heart cells is completely disorganised and there is no effective heart beating to generate blood flow.

There are multiple causes of these three arrhythmias. In general, coronary artery disease (CAD) is of particular importance.

Coronary artery disease refers to the condition in which there is insufficient blood supply to the heart muscles because of narrowing of the coronary vessels. If the insufficiency of blood supply is severe, the heart muscle cells may die, an infarct or the commonly called heart attack occurs.