Anti-arrhythmic agents in ischemic heart disease: supraventricular arrhythmias, digitalis toxicity and chronic stable ventricular ectopic beats.

Digoxin remains a very useful agent for chronic atrial fibrillation or for the ectopic beats associated with heart failure. But when rapid control of the ventricular rate is required to arrhythmias such as atrial fibrillation, atrial flutter, or paroxysmal atrial tachycardia, a slow infusion of verapamil is the agent of choice. In general, verapamil may be added to digoxin or given intravenously while a digoxin effect is awaited, unless there is digitalis toxicity. In digitalis toxicity, lignocaine remains the agent of choice for ventricular arrhythmias, and is given in the same doses as for acute myocardial infarction; phenytoin is used for digitalis-arrhythmias with A-V block. Verapamil may be infused very cautiously for digitalis-induced supraventricular tachyarrhythmias. The use of oral agents such as quinidine, disopyramide and mexilitene for chronic prophylaxis of ventricular ectopic beats is of doubtful effectiveness, unless the ectopic activity is symptomatic. Serious ventricular arrhythmias may be induced by quinidine and disopyramide. Beta-blockade is especially useful for ectopic beats associated with anxiety, or when arrhythmias are associated with angina of effort or hypertension. As always, major contraindications to the use of beta-blockade include cardiomegaly, heart failure or asthma.