Focal Transcatheter Cryoablation: Is a Four‐Minute Application Still Required?
Cryoablation procedures are commonly performed to treat supraventricular arrhythmias, particularly atrioventricular nodal reentrant tachycardia and other perinodal substrates, with good efficacy outcomes and an attractive safety profile.1 The technology has evolved considerably since initial preclinical studies and the first human application in 1998. Early steerable cryocatheter systems with integrated recording and pacing electrodes used chlorofluorocarbon refrigerants, first Halocarbon 502‐Freon® followed by Genetron®‐AZ‐2067. Optimal freezing parameters were defined on the basis of histopathological analyses and visualization of iceball formation by ultrasonic means.3 These studies led to the recommendation to perform 4‐minute cryothermal applications,3 the currently used default setting. However, chlorofluorocarbon agents have since been replaced by more potent refrigerants, currently nitrous oxide (N2O), which produces a faster drop in temperatures and lower absolute values. Nevertheless, optimal lesion duration has not been challenged since. We hypothesized that the more efficient N2O system requires a shorter application time to produce similar ablation lesions. To test this hypothesis, we performed a randomized preclinical study to compare focal ablation lesion dimensions with 2‐minute versus 4‐minute application times.