Shortening of ventriculoatrial conduction in patients with left-sided Kent bundles

In six patients with electrophysiologic evidence of ventriculoatrial conduction through a left Kent bundle, we documented that programmed right ventricular stimuli falling within an interval of 60 to 160 msec from the end of the T wave propagated to the left atrium (distal coronary sinus unipolar lead) 10 to 20 msec earlier than the basic paced beats. This phenomenon could be reproduced 24 hours later in two patients, and it was abolished by procainamide and amiodarone in one instance. During this interval we were unable to induce reciprocating tachycardia. Our observations outline a new pattern in ventriculoatrial conduction in patients with left-sided Kent bundles. The findings suggest in addition, that (1) supernormal conduction may be responsible for the observed shortening in retrograde conduction and (2) this phenomenon does not facilitate induction of reciprocating tachycardia.