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 ventricular arrhythmias. Bigeminal rhythm or premature ventricular contractions are frequently noted with the induction of anesthesia, with tracheal intubation, during dissection and manipulation of the heart and great vessels, 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 accompanying an acquired valvular lesion, premature contractions may persist or progress to sustained ventricular tachyeardia even after the precipitating hypoxia has been corrected. Under these circumstances, the administration of an effective antiarrhythmic agent is indicated, not only to restore a normal rhythm, but, more importantly, to prevent progression of the abnormality to ventricular 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 systemic hypotension3-5 and this side effect frequently 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 output and systemic arterial pressure.3' 4, 6 In 1950