| Abstract: | Many electrocardiographic criteria have been proposed for the differentiation of ventricular extrasystole and supraventricular conduction with aberrancy in atrial fibrillation but the validity of these have not been confirmed by intracardiac studies. We recorded His bundle electrograms in nineteen patients (eleven men, eight women) referred for diagnosis of abnormal QRS complexes in the context of chronic atrial fibrillation. Of 1,068 wide QRS complexes analyzed, 91% proved to be of ventricular origin. Electrocardiographic criteria which were specific for ventricular extrasystole included: left bundle branch block morphology, right bundle branch block morphology with a monophasic R in lead V1 or an RS or QS pattern in lead V6, presence of a "compensatory pause", i.e., compensatory cycle (V2-V3) longer than the average cycle length of ten normally conducted beats preceding the abnormal complex (927 +/- 317 vs 780 +/- 199, mean +/- SD in msec. p less than 0.005), frontal QRS axis of the abnormal complex directed superiorly or to the right and the presence of a "short-long" cycle sequence. Right bundle branch morphology with a triphasic R in lead V1 or QRS pattern in V6 and concordant initial vector in lead V1 or in more than one ECG leads were very specific for supraventricular conduction with aberrancy. Analysis of coupling interval and Ashman's phenomenon, i.e., the long-short cycle sequence, were not specific for supraventricular conduction with aberrancy. We conclude that in digitalis-treated patients with chronic atrial fibrillation the majority of abnormal QRS complexes are of ventricular origin. The diagnosis of ventricular extrasystole or aberrancy can be made using a single ECG lead (V1) and applying a combination of easily applied criteria. |
