Escape rhythm in complete A-V block. The recovery phase after overdrive suppression from artificial ventricular...

In 60 patients with third degree A-V block, recovery of escape rhythm from overdrive suppression after ventricular pacing has been studied. Implanted unipolar VVI pacemakers were inhibited by chest wall stimuli. A total of 165 rhythmograms were studied. In 37, the rate was irregular, in the other 128 the escape rate increased gradually, following an exponential curve until stabilization after 3 minutes. In 29 of these rhythmograms, a possible exit block of the first escape impulse was observed. In 99 rhythmograms without exit block, escape rhythm recovery time was an average 1.45 times basal escape RR intervals. Overdrive suppression was most marked in patients with a slow escape rhythm.