Cryolesion Characteristics.
Introduction: Despite widespread clinical use, ablation lesions produced by cryocatheters with 6 and 8 mm electrode-tips have not been fully characterized. We, therefore, sought to quantify and compare lesion dimensions and thrombus formation with 4, 6, and 8 mm electrode-tip cryocatheters.
Methods and results: By means of a randomized factorial design, 72 ablation lesions were created in atrial and ventricular chambers of adult miniature swine at a mean temperature of 79.9 +/- 4.0 degrees C. By histological morphometric analysis, the overall lesion depth was 4.3 +/- 2.1 mm, surface area 61.3 (28.7, 116.0) mm(2), and volume 130.2 (62.7, 231.3) mm(3). Cryolesions produced by all electrode-tip sizes were well circumscribed, with intact endothelial cell layers, and absence of thrombus. Colder temperatures generated lesions of greater surface area (P = 0.0061) and volume (P = 0.0080), but not depth. Depths were similar between the three electrode-tips. However, surface areas produced by 8 mm catheters were 91.7 mm(2) larger on average (176.7% increase, P = 0.0003) than 4 mm and 72.3 mm(2) greater (101.3% increase, P = 0.0144) than 6 mm catheters. The 8 and 6 mm catheters yielded mean lesion volumes 252.6 mm(3) (248.3% increase, P = 0.0041) and 115.9 mm(3) (113.9% increase, P = 0.0670) larger than 4 mm catheters. Greater variability in surface area and volume were observed with 8 mm catheters.
Conclusion: Longer electrode-tip cryocatheters produce larger lesions of similar depth, with intact endothelial layers and absence of thrombosis. Surface areas and volumes may be particularly sensitive to catheter tip-to-tissue contact angles with larger electrodes, as reflected by greater variability with 8 mm tips.