A sudden cardiac arrest (SCA) occurs when there is an abrupt loss of heart function and can be due to a variety of heart conditions. The most common cause of SCA is a sudden onset of abnormal heart rhythm. This is usually due to a fast but chaotic heart rhythm called ventricular fibrillation (VF) or tachycardia (VT).
Occasionally, SCA can be due to a pause in heart rhythm due to abnormality of the heart pacemaker cells or during a heart attack. It is estimated that 1000 Singaporeans die from sudden cardiac death every year, about half of whom are below 60 years old.
When a patient suffers from VF (a form of cardiac arrest), the heart beats 400 to 500 beats per minute, causing the normal rhythmic contractions of the lower chambers of the heart to stop. When the heart contraction stops, blood and oxygen are not pumped to the rest of the body and within seconds, the brain becomes starved of oxygen and the person loses consciousness. Without immediate treatment, the brain will cease to function and the person will die within minutes.
A cardiac arrest is not the same as a heart attack. SCA is caused by an abnormal heart rhythm due to abnormal 'electrical circuitry' of the heart. A heart attack is caused by blockage or occlusion of the arteries supplying blood to the heart, causing a portion of the heart muscle to be damaged. This may or may not lead to a cardiac arrest.
