The commonest cause for cardiac arrest is a myocardial infection (heart attack). Other probable causes include electrical injury, respiratory arrest, loss of blood, drug overdose, hypothermia and anaphylactic shock (an enormously fierce type of allergic reaction).
Diagnosis and treatment
The survival of the patient depends on prompt restoration of the heartbeat and oxygen supply to the brain. Cardiopulmonary resuscitation can be used to maintain circulation until the heartbeat returns.
A diagnosis of cardiac arrest is only confirmed after monitoring the electrical activity of the heart using ECG. This assists the medical personal to distinguish between ventricular fibrillation (the rapid, uncoordinated contraction of individual heart muscle fibres) and asystole (the total absence of the heart muscle activity), which are two abnormalities of heart rhythm that can lead to cardiac arrest.
Ventricular fibrillation can be put right by defibrillation (application of an electric shock to the heart). Asystole is harder to reverse but can respond to injection of adrenaline ( epinephrine) or electrical pacemaker.
In general recuperation after ventricular fibrillation is more expected than after a cardiac arrest triggered by asystole.