Transient atrioventricular conduction block with cryoablation following normal cryomapping.

OBJECTIVES

The purpose of this study was to demonstrate that adverse but reversible effects on AV conduction may be observed during cryoablation despite no evidence of deleterious effects evident during cryomapping.

BACKGROUND

Transcatheter cryoablation has recently been introduced for treatment of supraventricular tachycardia. Potential advantages compared with radiofrequency ablation include decreased risk of thromboembolism and perforation, less patient discomfort, more sharply demarcated lesions, and decreased risk of inadvertent damage to adjacent structures due to the ability to observe the electrophysiologic effects of lesion generation prior to permanent tissue damage. Occasionally, however, adverse electrophysiologic effects may be observed during cryoablation when prior cryomapping suggests a safe location.

METHODS

We reviewed the experience with our first 32 consecutive patients who underwent cryoablation for supraventricular tachycardia. Patients who experienced transient heart block during cryoablation following uneventful cryomapping were identified.

RESULTS

Five patients in whom cryomapping was performed with no evidence for deleterious effects on AV conduction were identified. However, application of cryoablation at these mapped sites resulted in transient complete heart block. This experience demonstrates that the cryolesion created during cryoablation may expand relative to that suggested by cryomapping.

CONCLUSIONS

It is important to maintain vigilance in monitoring for AV nodal conduction abnormalities during cryoablation, even when cryomapping suggests a safe location for cryoablation.