Abstract 2349: Cryoablation for Atrioventricular Nodal Reentrant Tachycardia (AVNRT) in 154 Young Patients: 4mm vs. 6mm Catheter Tip Sizes
Introduction: Cryoablation of AVNRT has a high initial success rate and an excellent safety profile; however, there is a risk of recurrence. We hypothesized that the transition from a 4mm to a 6mm cryoablation catheter tip size would decrease recurrences without compromising safety.
Methods/Results: We retrospectively reviewed all patients (n=154) who underwent cryoablation for AVNRT at the UCSF/Stanford Pediatric Arrhythmia Center from 1/04 –2/07. Initially, we used the 4mm tip, and then transitioned to a 6mm tip except for younger and smaller children. The majority of the patients had a structurally normal heart. 10 patients had congenital heart disease (3 ASDs, 3 aortic valve abnormalities, 1 Ebstein’s, 1 PDA, 1 unbalanced AV canal defect, 1 L-TGA). Typical AVNRT was inducible in 123 patients (80%), atypical in 13 (9%), and both typical and atypical in 1 patient. 17 (11%) had presumed AVNRT. Additional arrhythmias were documented in 18 patients (7 WPW, 6 AET, 4 atrial fibrillation, 1 JET). There was no difference in initial outcomes between the 4mm and 6mm tips. There was no permanent AV block. Recurrence rates were lower with the 6mm tip, but this did not reach statistical significance. The median time to recurrence was 2 (0.25–20) months. Follow-up time was longer in the 4mm group but did not significantly impact recurrence rate (p=0.61). Recurrences were not associated with any patient variable (age, size, heart disease, AVNRT inducibility, additional arrhythmias) or any procedural variable (fluoroscopy time, duration of cryoablation, transient AV block, presence of residual slow AV nodal pathway or echo beats).
Conclusions: Initial outcomes of the 6mm cryoablation catheter tip for AVNRT are excellent and early recurrence rates are promising. However, we have yet to demonstrate a convincing advantage for the 6mm tip. Further improvements in cryoablation technique are necessary to reduce recurrences without sacrificing the safety profile.