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Cryothermal Ablation of the Slow Pathway for the Elimination of Atrioventricular Nodal Reentrant Tachycardia

Background—We report the first successful slow pathway ablation using a novel catheter-based cryothermal technology for the elimination of atrioventricular nodal reentrant tachycardia (AVNRT). Methods and Results—Eighteen patients with typical AVNRT underwent cryoablation. Reversible loss of slow pathway (SP) conduction during cryothermy (ice mapping) was demonstrated in 11 of 12 patients. Because of time constraints, only 2 sites were ice mapped in 1 patient. Seventeen of 18 patients had successful cryoablation of the SP. One patient had successful ice mapping of the SP, but inability to cool beyond −38°C prevented successful cryoablation. A single radiofrequency lesion at this site eliminated SP conduction. No patient has had recurrent AVNRT over 4.9±1.7 months of follow-up. During cryoablation, accelerated junctional tachycardia was not seen and was therefore not available to guide lesion delivery. Adherence of the catheter tip during cryothermy (cryoadherence) allowed atrial pacing to test for SP conduction. Cryoablation in the anterior septum produced inadvertent transient PR prolongation consistent with loss of fast pathway conduction in 1 patient and transient (6.5 seconds) 2:1 AV block in another. On rewarming, the PR interval returned to normal, and the AV nodal effective refractory period was unchanged in both. Accelerated junctional tachycardia was seen on rewarming in both but not during cryothermy. Conclusions—Cryothermal ablation of the SP was achieved in patients with this novel technique. Successful ice mapping of both the SP and fast pathway was demonstrated. The ability to test the functionality of specific ablation sites before production of a permanent lesion may eliminate inadvertent AV block.