Focal Transcatheter Cryoablation: Is a Four‐Minute Application Still Required?

Focal Transcatheter Cryoablation Introduction The standard 4‐minute application time for transcatheter cryoablation was determined in the 1990s when the system employed less potent chlorofluorocarbon refrigerants. The current refrigerant, nitrous oxide, generates substantially colder temperatures, with a faster cooling rate. Methods and Results We conducted a preclinical study on 32 mongrel dogs with stratified randomization of right atrial, right ventricular, and left ventricular chambers to 2‐minute versus 4‐minute application times using 8‐mm electrode tip cryocatheters (Freezor Max, Medtronic CryoCath LP, Montreal, Canada). Animals were sacrificed one month after the procedure. Three‐dimensional morphometric analyses were conducted in a blinded fashion. A total of 193 identified ablation lesions were processed for histological analyses, 102 with 2‐minute applications and 91 with 4‐minute applications. Ablation lesion surface area (167.8 ± 21.6 mm 2 vs. 194.3 ± 22.6 mm 2 , P = 0.40), maximum depth (4.4 ± 0.2 mm vs. 4.5 ± 0.2 mm, P = 0.71), and volume (125.7 ± 69.5 mm 3 vs. 141.0 ± 83.5 mm 3 , P = 0.25) were similar between groups. Overall, 90.2% of ablation lesions in the right atrium were transmural, 45.6% in the right ventricle, and 2.4% in the left ventricle, with no differences between 2‐minute and 4‐minute application times (P = 0.55). Thrombus was detected on the endocardial surface of 0.0% and 3.3% of ablation lesions created with 2‐minute and 4‐minute application times, respectively (P = 0.10). Conclusion Single 2‐minute and 4‐minute application times result in catheter ablation lesions of similar size using the modern cryoablation system with nitrous oxide as a refrigerant. While these findings suggest the potential to reduce the standard 4‐minute application time, further studies are required to compare clinical efficacy.