Although coronary artery disease is the most frequent cause of sudden cardiac death, it may be caused by a heterogeneous group of disorders. Acute ischaemia is responsible for about half the cases of sudden death after acute myocardial infarction, and is manifested through ventricular fibrillation or polymorphic ventricular tachycardia. Several factors affect the haemodynamic consequences of a ventricular arrhythmia. Re-entry is the mechanism involved in patients with a history of myocardial infarction and therapy should be individualised and directed to the arrhythmia. Simple decision trees are available that can help to find the most appropriate therapy; implantable defibrillators are the most effective modality in certain very high risk subsets.