Safety and Feasibility of Cryothermal Ablation Within the Mid‐ and Distal Coronary Sinus

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Abstract
The aim of this study was to assess the safety and feasibility of catheter-based cryothermal ablation lesions in the mid- and distal coronary sinus. Cryothermal ablation lesions were delivered using a 7-French catheter at the mid- (n = 13) and distal (n = 12) coronary sinus in 14 swine under general anesthesia. Lesions were delivered for 2 or 4 minutes in a 1:2 randomized ratio such that seven 2-minute lesions and eighteen 4-minute lesions were delivered to a maximum negative temperature of -70 degrees C. Integrity of the circumflex artery was assessed by angiography before and after each lesion application. In five animals, arterial Doppler flow velocity was continuously monitored and coronary flow reserve assessed. Histologic assessment of the left AV ring was made after a 48-hour survival period and lesions graded for depth and transmurality. Eighteen of 25 lesions were >3 mm deep: five of seven 2-minute lesions and thirteen of eighteen 4-minute lesions. Lesions were transmural in 18 of 25 cases. Two transmural lesions were limited in depth due to their epicardial position. One 2-minute mid-coronary sinus lesion was not found. Adherent thrombus was seen grossly in the coronary sinus at one site and only on microscopic examination in three other lesions. Angiography demonstrated no arterial spasm or thrombosis. Continuous-flow Doppler remained unchanged throughout lesion production. Coronary flow reserve was unchanged (1.7 +/- 0.8 preablation vs 1.7 +/- 1.0 postablation, P = 0.6). The media and intima were preserved in all cases. Necrosis of the adventitia was seen in one arterial segment. Catheter-based cryoablation can produce lesions in the musculature of the adjacent atrium and ventricle when accessed from the coronary sinus without significant injury to the coronary sinus or adjacent artery. This method has potential application as the ablation method of choice when such lesions are required.