His bundle recordings in double tachycardias not due to digitalis intoxication.

Electrophysiological studies were performed in a patient with chronic chagasic cardiomyopathy, recurrent sustained ventricular tachycardia, and a history (without electrocardiographic documentation) of paroxysmal atrial flutter. Ventriculoauricular conduction occurred during short bursts of ventricular pacing. Moreover, the retrograde P of ectopic ventricular beats which appeared after pacing was stopped precipitated an atrial tachyarrhythmia with an irregular atrial rate. In addition, burst ventricular pacing, performed while this atrial tachyarrhythmia was present, initiated and subsequently terminated a ventricular tachycardia with similar characteristics to the one occurring spontaneously. The double (atrial and ventricular) tachycardias described in this communication were different from those previously reported in that the arrhythmias were not due to digitalis toxicity, but resulted from the modality of ventricular stimulation performed in a patient who had the specific type of cardiomyopathy seen in the chronic stage of Chagas' disease.