Abstract
The effect of ventricular overdriving test (VOD) on the spontaneous heart activity was studied in patients with advanced AV block and SSS. In twenty patients of AV block (stable complete AV block 8, second degree or unstable AV block 12), constant depression of subsidiary pacemaker for more than 4 second was observed in 8 patients (AH block 1, intra-His block 2, HV block 5). In contrast 10 patients (AH block 2, intra-His 2, block 6) showed no depression. In ten patients of SSS (Type I three, Type II five, Type III two), spontaneous heart activity was depressed in 3 patients of Type II which showed retrograde conduction to atrium in ventricular pacing. In the other seven patients, no depression was observed. The prolongation of the escape rhythm recovery time after VOD was depended upon the rate and duration of the pacing. The site of AV block was not correlated with depression of subsidiary pacemaker by VOD. VOD was effective in selecting pacemaker dependent patients, and useful to predict pacemaker induced arrhythmia and possible recovery of AV conduction.
