A Sudden Cardiac Death (SCD) attack is when there is an abrupt loss of heart function and can be due to a variety of heart conditions. However, the most common cause of SCD 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 SCD 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 SCD 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 SCD attack is not the same as a heart attack. SCD 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 an SCD attack.

What makes sudden cardiac death a silent killer is that unlike a heart attack, which has the typical symptoms of chest pains and breathlessness, sudden cardiac death however, has no warning signs and symptoms. The only way to treat a SCD attack and to set the rapid heartbeat back to its normal pace is to deliver an electrical shock to the heart using a device called a defibrillator. For individuals who are identified as patients at a higher risk of suffering from a SCD attack, an implantable cardioverter defibrillator (ICD), a pocket-sized device which sends an electric current to the heart when the heart beat becomes abnormal, could be implanted in the body.

Collaborating with the Health Sciences Authority, the National Heart Centre Singapore conducted a study on 229 sudden unexpected deaths in people aged 18 - 60 years old for the year 2003. Despite the fact that the study was only based on the results from an isolated year, the findings were astounding.

The study found that about 0.6 Singaporeans below 60 years old fall victim to SCD every day and that 91% of the people who died from sudden cardiac death were males. In addition, the study found that although Chinese people made up more than half of the sudden cardiac deaths in 2003 (53.2%), a significant percentage of people who had died were Malay (16.4%) and Indian (14%) as well. The study also found that the mean age for males dying from SCD in 2003 was 46 ±9 years and 49 ±9 years for females. An important finding of the study was that 81% of all SCD deaths were caused by coronary artery disease (which is the occlusion of blood arteries), with almost half of all patients irrespective of age having triple vessel disease prior to dying of SCD.