The antiarrhythmic properties of lidocaine and procaine amide

THE operative management of patients with congenital or acquired heart disease is often complicated by the occurrence of ven-tricular arrhythmias. Bigeminal rhythm or premature ventricular contractions are fre-quently noted with the induction of anesthe-sia, with tracheal intubation, during dissection and manipulation of the heart and great ves-sels, and with nasotracheal aspiration in the postoperative period. Their initial occurrence is most often related to a temporary period of hypoxia, but in many patients, particularly those with advanced myocardial disease ac-companying an acquired valvular lesion, pre-mature contractions may persist or progress to sustained ventricular tachyeardia even after the precipitating hypoxia has been cor-rected. Under these circumstances, the ad-ministration of an effective antiarrhythmic agent is indicated, not only to restore a nor-mal rhythm, but, more importantly, to pre-vent progression of the abnormality to ven-tricular fibrillation. In the past, procaine and the longer-acting related compound, procaine amide, have been most widely employed for the treatment of the various ventricular arrhythmias occurring in the course of cardiac operations.1-3 These compounds, however, cause significant sys-temic hypotension3-5 and this side effect fre-quently preeludes the administration of a therapeutically effective dose. In addition, both procaine and procaine amide have been shown experimentally to impair myocardial contractile force and to lower cardiac outpu