Increase in ventricular fibrillation threshold following blockade of atrioventricular conduction

The threshold for electrically induced ventricular fibrillation was determined in anesthetized open-chest dogs, before and after blockade of atrioventricular (A-V) conduction. Without exception, the threshold was significantly elevated after creation of the block. The precise mechanism of this effect is not known at this time. However, it is apparent that when ventricular fibrillation thresholds are being determined, the functional status of A-V conduction should be established and maintained throughout the study.