The Journal of Thoracic and Cardiovascular Surgery, Vol 101, 1004-1015, Copyright © 1991 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Feasibility of closed heart discrete cryomodification of atrioventricular conduction. Electrophysiologic effects in the canine heart
Y Yagi, RB Schuessler, JP Boineau and JL Cox
Department of Surgery, Washington University School of Medicine, St. Louis, Mo 63110.
Discrete cryosurgical modification of atrioventricular conduction abolishes
refractory atrioventricular node reentry tachycardia with preservation of
antegrade atrioventricular nodal conduction. This procedure presently
requires cardiopulmonary bypass. To modify atrioventricular conduction
without cardiac surgery, we evaluated the electrophysiologic effects of
cryolesions applied to the peri-nodal area in the closed heart in 16 dogs
before operation, during cryothermic exposure, and at 1 hour and 3 hours
after operation. The electrophysiologic effects were evaluated in 10 of the
16 dogs at 2 weeks postoperatively. The dogs were given general
anesthetics, and a cryoprobe was introduced into the right atrial cavity
through the right atrial appendage. Cryolesions (-60 degrees C) were placed
at nine to eleven preselected points around the perinodal area guided by
electrodes on the tip of the cryoprobe. Postoperatively, there were
significant prolongations of the atrio-His interval, Wenckebach's point,
effective refractory period, and functional refractory period of the
atrioventricular node. Atrial echo beats were eliminated or decreased in
frequency. There was also a significant increase in retrograde
ventriculoatrial conduction time. In the long-term observation period the
atrio-His intervals remained significantly prolonged in comparison with the
preoperative values, the atrial echoes progressively decreased, and
ventriculoatrial conduction was absent in five of seven animals. A
serendipitous atrioventricular node reentry tachycardia that was inducible
in one animal with dual atrioventricular node conduction pathways was
successfully eliminated and was not inducible at 2 weeks postoperatively.
Complete atrioventricular block occurred during attempts to produce greater
atrio-His prolongation in three of the 16 animals and persisted in two for
the 2-week period of observation. Closed heart intracardiac
cryomodification of atrioventricular conduction is feasible, with the
cryoprobe in normothermic blood, producing changes in atrioventricular
conduction similar to the open cardiac procedure.
