What does sudden cardiac death mean?
The term sudden cardiac death refers to the sudden loss of function of the heart. This is often referred to as a cardiac arrest. It can occur in a person with or without heart disease. The problem occurs due to an abrupt disturbance in the heart’s rhythm which results in the heart not beating or beating too little to keep the person alive. The rhythm disturbances are of different types. "Asystole " is where there is no electrical activity and thus no heart beat. A flat-line is seen on the monitor. Ventricular fibrillation (VF) is where there is very erratic electrical activity but the heart does not pump. Complete heart block is where the heart rate is too slow to keep the patient alive for long. In each case, it occurs suddenly or shortly after the onset of symptoms. Without treatment, the outcome is usually fatal.

Underlying Cause
Disease of the coronary arteries is the most common cause of sudden cardiac death. Thus sudden cardiac death may occur after a heart attack or after an episode where there is reduced blood flow to the heart. Heart muscle conditions such as cardiomyopathies may also cause cardiac arrest. In some individuals with normal hearts, cardiac arrest can occur with certain drugs, both legal and illicit, with lack of oxygen, with chemical disturbances in the blood stream or following a chest injury. Between one third and one half of patients who get a heart attack suffer sudden cardiac death.

Can sudden cardiac arrest be reversed?
If one can get to the patient within the first few minutes after a cardiac arrest, it is possible to restore the patient’s circulation by cardiopulmonary resuscitation (CPR) . In addition, CPR alone may restore a normal heart rhythm but often this requires the administration of medicine or the use of direct cardioversion using a defibrillator.

The use of defibrillators and heart monitoring in the CCU has dramatically reduced death from sudden cardiac arrest in hospitalised patients. Delivery of CPR and cardioversion in the community has also been shown to reduce deaths from cardiac arrest but survival is very dependant on the time taken to reach the patient and to restore their circulation to normal. It is therefore very important to have large numbers trained in the community in CPR and in the use of a defibrillator.These external automated defibrillators (AED's) are becoming more readily available, especially where large groups of people congregate such as at sporting venues and have the potential to reduce the risk of sudden death.

What are treatments for survivors?
If CPR and defibrillation are delivered early on, there is a good chance of successfully resuscitating the patient. There are some instances when these life saving measures are delivered too late and although the heart returns to its normal rhythm, the brain may be severely damaged. In individuals who have been successfully resuscitated it is important to investigate the patient thoroughly and provide the necessary treatment to avoid further episodes of sudden cardiac death. Some times the situation is due to a drug overdose and thus avoidance is all that is necessary. In the majority of cases, the problem is related to narrowed coronary arteries. In this situation it is necessary to perform a procedure to either open up the narrowed vessel (angioplasty) or to bypass the narrowings (Bypass surgery). In some patients this is not sufficient to prevent the problem or there is another cause for the sudden cardiac death. In these patients  an implantable cardioverter / defibrillator is inserted with or without background anti-arrhythmic therapy.