EXTERNAL ELECTRIC STIMULATION OF THE HEART *

External electric stimulation of the heart, first applied successfully in man in 1952,' is now widely used in the emergency resuscitation of patients from ventricular standstill. It is a simple and safe way of evoking ventricular beats that is always effective in ventricular standstill unless cardiac responsiveness has been impaired by prolonged anoxia or other depressing factors (FIGURE 1 ) . Its SUCcessful use has been reported in Stokes-Adams disease, in acute myocardial infarction, in reflex vagal standstill, in standstill due to drugs (quinidine, procaine amide, digitalis), and in unexpected standstill during anesthesia, surgery, and other therapeutic and diagnostic procedures.2 The external electric pacemaker is particularly valuable in Stokes-Adams disease because, with frequently recurrent attacks, monitor-pacemakers are often attached to facilitate prompt recognition and res~scitation.~ We have found external electric stimulation very useful not only for spontaneous Stokes-Adams attacks but also for the attacks that are so apt to occur during surgery in these patients. Indeed, during the implantation of direct electric pacemakers we control the heart safely and satisfactorily with an external pacemaker and long subcutaneous precordial needle^,^ rather than with an endocardial catheter electrode, which carries small but significant risks.5 Patients with acute myocardial infarction face a high risk of sudden death from ventricular standstill and fibrillation.e Continuous cardiac monitoring and prompt resuscitation with external electric stimulation as well as with external massage and countershock have been successfully used in these patients.' Indeed, all the conditions listed constitute situations with high risks of cardiac arrest in which continuous cardiac monitoring and external stimulation or countershock have resulted in striking success in resuscitat i ~ n . ~ , * , ~ In addition to its usefulness in resuscitation from ventricular standstill, external electric stimulation has also been found valuable in patients with Stokes-Adam disease to prevent abnormal ventricular irritability, ranging from multifocal beats to tachycardia and fibrillation (FIGURE 2) . We have demonstrated repeatedly that acceleration of the ventricular rate above a critical level, whether by electric stimulation or by sympathomimetic amines,lOJ1 will prevent these manifestations of ventricular irritability and maintain a regular ventricular rhythm. The critical levels above which ventricular irritability is controlled vary somewhat from patient to patient and from time to time in the same patient; they usually range between 40 and 60 beats per minute but are occasionally higher. Electric stimulation, however, will have no effect on paroxysms of ventricular tachycardia or fibrillation that have already begun; other measures, i.e. countershock, may be necessary to terminate them. External stimulation, then, i s indicated for emergency resuscitation from ventricular standstill and for temporary prevention of ventricular tachycardia and