The Journal of Thoracic and Cardiovascular Surgery, Vol 91, 826-834, Copyright © 1986 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Cryosurgical modification of retrograde atrioventricular conduction. Implications for the surgical treatment of atrioventricular nodal reentry tachycardia
WL Holman, M Ikeshita, JG Lease, PK Smith, GK Lofland and JL Cox
Paroxysmal supraventricular tachycardia resulting from atrioventricular
nodal reentry is a common arrhythmia that usually responds to medical
therapy. When atrioventricular nodal reentry tachycardia is refractory to
medical therapy, cryoablation or endocardial catheter ablation of the His
bundle has been employed to protect the ventricles from the tachycardia.
However, these techniques necessitate implantation of a permanent
ventricular pacemaker. A cryosurgical procedure that ablates the
anatomic-electrophysiologic substrate for atrioventricular nodal reentry
tachycardia while preserving antegrade atrioventricular conduction has been
described. The purpose of the present study was to determine the effects of
this procedure on retrograde atrioventricular conduction and on the
ventricular echo phenomenon in particular. Thirty adult mongrel dogs
underwent either the cryosurgical procedure (n = 20) or a sham operation (n
= 10). The animals were studied either immediately postoperatively (acute
cryosurgery group and control group, n = 10 for each group) or 14 weeks
postoperatively (chronic cryosurgery group, n = 10). Decremental
ventricular pacing and programmed premature ventricular pacing protocols
were used to determine the retrograde atrioventricular nodal conduction
time, Wenckebach point, atrioventricular nodal refractory periods, and
ventricular echo reflection time. No electrophysiologic alterations were
noted in the sham-operated group. In the acute cryosurgery group, the
retrograde Wenckebach point, atrioventricular nodal conduction time,
functional refractory period of the atrioventricular node, effective
refractory period of the atrioventricular node, and ventricular echo
reflection time were all significantly prolonged. In the chronic
cryosurgery group, no significant change in ventriculoatrial conduction was
noted, but the ventricular echo phenomenon was eliminated in all but one
animal. These data further document that this cryosurgical procedure is
capable of ablating the anatomic-electrophysiologic substrate necessary for
atrioventricular nodal reentry tachycardia while preserving
atrioventricular conduction.
