Cardioversion of Supraventricular Tachycardias

Cardioversion was employed in 33 episodes of supraventricular tachycardia in 25 patients. Of these, 18 were episodes of paroxysmal atrial tachycardia with block and the remainder were atrial, junctional, and undefined supraventricular tachycardias. Cardioversion was successful in restoring sinus rhythm in 23 (70%). A major problem was to identify when digitalis intoxication was the cause of the supraventricular mechanism. By progressive titration of the shock energy, it was possible to determine the presence of digitalis intoxication. This was manifested by emergence of ventricular ectopic beats and acceleration in atrial rate. The use of lidocaine abolished the ventricular extrasystoles. Of the 10 patients failing to revert, seven had digitalis toxic arrhythmias. No complications were encountered.