Background: Both radiofrequency (RF) and cryo ablation are currently clinically used treatment modalities for several types of cardiac arrhythmia. The size of the created lesion is dependent on convective cooling which changes according to location of treatment site.

Methods: Fresh porcine hearts were sectioned and placed in a temperature-controlled saline bath (37 ºC) with varying directed flow rates (0, 1, 2 and 3 L/min) across the myocardial surface. Either RF or cryo ablation were performed using commercial catheters and clinical treatment parameters (RF: 65ºC target temperature for 1 min; Cryo: -80ºC target temperature for 4 min), with four ablations at each flow rate. The ablation site was marked on each tissue sample and the samples were placed in culture media for 24hrs. The pieces were then sectioned along the direction of flow and stained with nitro blue tetrazoleum. Lesion depth and width were measured, and lesion volume calculated as a partial oblate ellipsoid.

Results: Both RF and cryo lesions were significantly dependent on flow rate (p < 0.001). For cryo ablation, lesion volume was 1036 ± 340, 930 ± 249, 805 ± 211 and 379 ± 114 mm³ for 0, 1, 2 and 3 L/min flow rate respectively. For RF ablation, lesion volume was 121±51, 257±98, 393±150 and 549±157 mm³ for 0, 1, 2 and 3 L/min flow rate respectively. At low flow rates, cryo ablation lesions were larger than RF (p < 0.001)

Conclusions: While RF ablation produced larger lesions with increasing flow, cryo ablation lesions exhibited the opposite flow dependence. This may suggest which modality is preferred depending on the location of the target site and local blood flow conditions.