Lesion dimension of cryoablation.
Background: Transvenous catheter cryoablation is a novel technique for treating cardiac arrhythmias. However, the relative importance of temporal application parameters on lesion dimension and clinical efficacy has not been studied.
Methods and results: We investigated the effects of (1) application duration: single 2.5 (2.5x1) versus single 5 versus double 2.5 (2.5x2) versus double 5 (5x2) minutes, (2) number of freeze-thaw cycles: single versus double, and (3) electrode contact area: horizontal versus vertical orientation, on the lesion diameter and depth during catheter cryoablation (10F, 6.5-mm tip-electrode, CryoCor, San Diego) in a thigh muscle preparation. A total of 175 lesions (horizontal=90, vertical=85) were created in thigh muscle preparations on 10 swine. The lesion diameter and depth were significantly greater using 2.5x2 and 5x2 application modes as compared with 2.5x1 applications (P<0.05). Horizontal tip-electrode orientation produced larger lesion diameter (P<0.05), but not lesion depth as compared with vertical orientation. Multivariate analysis demonstrated that both tip-electrode orientation and duration of freeze >2.5 minutes were independent predictors for lesion diameter (P<0.001). However, only duration of freeze >2.5 minutes was an independent predictor for lesion depth (P<0.001).
Conclusions: The dimensions of lesions created by catheter cryoablation are affected by mode of cryoablation application and electrode orientation. Increasing the duration of application, employing multiple freeze-thaw cycles at shorter cycle durations, and orienting the catheter to enhance/increase tissue contact can create a larger lesion.