Roberto De Ponti, “Cryothermal Energy Ablation Of Cardiac Arrhythmias 2005:
State Of The Art”
treatment by this energy source is considered the first choice therapy for its safety and efficacy.
The following is a brief analysis of the experience in cryoablation for each of the considered
arrhythmias.
16
Atrioventricular nodal reentrant tachycardia. So far, slow pathway ablation for atrioventricular
nodal reentrant tachycardia by cryothermal energy represents the numerically larger experience
in the clinical application of this new technology. Unlike radiofrequency energy, accelerated
junctional rhythm is not observed during cryothermal energy application on the slow
atrioventricular node pathway. Therefore, the only marker of effective ablation is suppression of
tachycardia inducibility during initial cooling (Figure 2A-B). Accordingly, baseline non
inducibility of the arrhythmia may be a limitation to the application of this technique. From the
early report16, several papers have contributed to accumulating experience in slow pathway
ablation, with a satisfactory success rate and a recurrence rate varying from 6 to 9.7%
17,18,19,20,21,22. In the “Frosty” trial19, a multicentric prospective trial performed in the United
States, 103 patients with atrioventricular nodal reentrant tachycardia were enrolled. On an
intention-to-treat basis, the acute procedural success was 91% with no device-related
complications and a recurrence rate of 6% in a 6 month follow-up. Cryomapping proved useful
to predict the site of successful ablation. Nine patients had inadvertent modifications of the
conduction over normal atrioventricular conduction pathways, including first to third degree
atrioventricular block and right bundle branch block. These all resolved completely, usually
within a minute or less and had no sequelae. A database gathering the worldwide experience and
based on a combination of registry and prospective trial data reports no case of permanent
atrioventricular block following cryothermal ablation of the slow pathway in more than 300
patients with atrioventricular nodal reentrant tachycardia20. Temporary first degree or higher
atrioventricular block, observed in 15 cases (4.3%) during cryomapping at -30°C or during
cryoablation at -75°C, was always reversible. Recently, the results of the first two prospective
randomized trials on transvenous cryoablation versus radiofrequency ablation of the slow
pathway for treatment of atrioventricolar nodal reentrant tachycardia have been published21,22. In
these studies, cryoablation proved as effective and safe for the cure of atrioventricular nodal
reentrant tachycardia as radiofrequency ablation. The higher recurrence rate that may be
observed in the cryoablation group21 suggests that, unlike radiofrequency ablation, prolonged
energy applications and postablation waiting time are necessary when cryothermal ablation is
used to minimize recurrence in the follow-up. In our own experience, we treat atrioventricular
nodal reentrant tachycardia by slow pathway cryoablation in patients with particular anatomic
characteristics, refractory to standard radiofrequency energy ablation or in pediatrics. Especially
in cases with difficult anatomy, such as a small or distorted Koch’s triangle, the characteristics of
cryothermal energy allow test of the ablation effect in particularly risky sites without producing
irreversible damage to atrioventricular conduction, if the application is timely interrupted. In
some complex cases, we found it necessary to resort to longer cryothermal energy applications
(up to 480 s) and to prolong postablation observation up to 60 min. In a patient with
atrioventricular nodal reentrant tachycardia, who underwent multiple unsuccessful ablation of the
slow pathway, we decided to target the fast pathway by cryothermal energy23. In this particular
case, selective and safe ablation of the fast pathway at the apex of the Koch’s triangle was
accomplished and this resulted in permanent cure of the arrhythmia.
According to the presented data, cryothermal energy is a valuable and useful alternative
to radiofrequency energy to treat patients with atrioventricular nodal reentrant tachycardia.
Absence of permanent inadvertent damage of atrioventricular conduction makes this new
technology particularly useful in cases with difficult anatomy, unsuccessful prior standard
ablation procedure, in pediatrics and in all cases, in whom even the lower risk of atrioventricular
block still possible with radiofrequency energy, is considered unacceptable.
Indian Pacing and Electrophysiology Journal (ISSN 0972-6292), 5(1): 12-24 (2005)