Treatment of cardiac arrhythmias with phenytoin.

Phenytoin was given intravenously in 37 patients with cardiac arrhythmias-21 had acute myocardial infarction and 16 had other conditions. There was a favourable response in 18 of the 21 cases with acute myocardial infarction, with a return to sinus rhythm in six of the nine cases with supraventricular arrhythmias, and a return to sinus rhythm in 10 of the 12 cases of ventricular arrhythmias, the remaining two showing a significant reduction in the number of ventricular extra-systoles.In the second group of 16 cases which had various causes there was a satisfactory response in only six. Digitalis played no part in producing any of the arrhythmias. Phenytoin was used orally for suppressing and preventing abnormal rhythm in five patients, and three of these responded favourably. The number of patients treated orally is too small to draw any definite conclusion.