Electrophysiologic and pharmacologic studies in a patient with acute myocardial infarction complicated by intraventricular and atrioventricular block.

A patient with an acute anterior wall myocardial infarction complicated by bilateral bundle branch block and paroxysmal AV block is presented. The following new, uncommon or unreported phenomena were documented: the simultaneous occurrence of phase-3 block in the right bundle branch and phase-4 block in the left bundle branch; the simultaneous occurrence of phase-4 block in both main bundle branches; phase-4 left posterior hemiblock associated with escape beats arising from the injured posterior division of the left bundle branch; supernormal conduction in the right bundle branck and 2:1 right bundle branch block related to supernormality. Most of these changes were, of course, not simultaneous, and their successive appearance was related to day-to-day and sometimes hour-to-hour variations in the degree and quality of the multifascicular injury caused by the infarct. In addition, the actions of several drugs upon automaticity and conduction were tested. The effects of amiodarone, lidocaine and isoproterenol were similar to those previously reported under comparable circumstances. At a moment when the patient had repeated episodes of paroxysmal AV block with severe Adams-Stokes seizures, the administration of a single i.v. dose of 0.25 mg of strophanthin suppressed totally the Adams-Stokes attacks through a significant enhancement of ventricular automaticity. If rapid implantation of an artifical pacemaker is not at hand, strophanthin may be life-saving in patients with acute paroxysmal AV block.