ARRHYTHMIAS AND MYOCARDIAL-INFARCTION

Ventricular arrhythmias are a frequent complication of myocardial infarction. In either the acute or the late stage, ventricular tachycardia and ventricular fibrillation represent the most common cause of cardiac death. About 15 % of the patients with acute myocardial infarction die before entering the hospital, the majority due to ventricular fibrillation. Another 10 to 15 % of the survivors of an acute myocardial infarction die suddenly within the subsequent year, again mostly due to ventricular arrhythmias. Independant risk factors for sudden cardiac death consist of depressed left ventricular function, persistent electrical instability (e.g. repetitive and complex VPB's, documented 'late potentials', inducibility of arrhythmias at programmed electrical stimulation), new onset complete-bundle branch block and large aneurysm of the left anterior ventricular wall. Bradyarrhythmias (i.e. high-degree AV-Block, asystole) are a far less common etiology of sudden cardiac death caused by an ischemic lesion to the conduction system. Betablockers have a well-known benefit in secondary prevention, whereas antiarrhythmic agents (with the exception of amiodarone) are ineffective in asymptomatic patients or may even increase the risk for sudden death due to a proarrhythmic effect (class IC); therefore, the latter are not recommended in asymptomatic patients with documented VPB's and preserved left ventricular function. The prognosis of patients with sustained VT and VF is poor. Their outcome is improved in responders to an individual antiarrhythmic therapy with serial drug testing or with subendocardial resection of localized areas and by implantation of a cardioverter defibrillator.