'Time to effect' during cryomapping: a parameter related to the long-term success of accessory pathways cryoablation in children

AIMS: Cryoablation is an effective treatment for children with an accessory pathway (AP). Nevertheless, AP may recur after a successful procedure. The aim of this study was to identify the factors predictive of AP recurrence. METHODS AND RESULTS: Thirty patients (mean age 12.6 +/- 2.9 years) with acutely successful cryoablation of supraventricular tachycardia caused by a right-sided AP were studied. In 20 patients, a lengthier cryoablation and a single 'bonus' cryoapplication to consolidate a permanent lesion were delivered. During the follow-up (mean duration 20 months, range 4-25), no permanent cryo-related complications occurred. Accessory pathway recurrence was observed in six patients (20%) overall, specifically in 30% of patients who did not undergo a bonus cryoapplication and in 15% of the others. The likelihood of AP recurrence was correlated with the 'time to effect' (TTE), i.e. the time interval between the onset of cryomapping at -30 degrees C and the disappearance of AP conduction. The mean TTE in the patients without AP recurrence was 8.2 +/- 8.4 s, in contrast with 16.7 +/- 9.8 s in the others (P = 0.04). The receiver-operating characteristic (ROC) curve of TTE values demonstrates that if the pathway does not lose its conduction capacity until 10 s after reaching -30 degrees C, the probability of arrhythmia recurrence is higher (area under curve = 0.767, sensitivity 83.3%, and specificity 66.7%). CONCLUSION: The long-term success of cryoablation of right-sided AP is closely correlated to the TTE during cryomapping.