Abstract 10638: The Time to Reach the Minimum Freezing Temperature During Cryoablation is a Predictor of First-Pass Conductional Block of Cavotricuspid Isthmus

Abstract

Background: Ablation using cryothermal energy has several potential advantages over radiofrequency (RF) ablation including a greater catheter stability due to adherence to the myocardial tissue during applications, reduced risk of thrombus formation, less pain, and etc. Several studies have reported the effects of cryoablation for the treatment of the cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) with similar efficacy and safety rates as reported for RF ablation. However, the details of freezing profile during CTI cryoablation still remain unknown. Methods: This study included 40 consecutive patients (32 men; 65±10 years) who underwent CTI cryoablation for common AFL. Patients were divided into 2 groups: one pass group who achieved first-pass conductional block of the CTI (n=30) and non-one pass group who did not (n=10). CTI ablation was performed with 2.5-min freezing cycle and 8-mm tip cryocatheters. A multidetector computed tomography scan with contrast injection which was performed before ablation in all the patients. We examined temperature changes at the catheter tip during first pass in CTI cryoablation and anatomical features of CTI in three regions: anterior, middle, and posterior. Results: There was no significant difference in the minimum freezing temperature between the one pass group and the non-one pass group (-82.6±1.6 vs. -83.2±1.2°C, P=0.245) in all the three regions. However, only in the anterior CTI, the time to reach the minimum freezing temperature was significantly shorter in the one pass group than in the non-one pass group (31.4±5.9 vs. 38.7±8.6 sec, P=0.012). The thickness of the anterior CTI was significantly thinner in the one pass group than in the non-one pass group (4.1±1.2 vs. 5.5±1.3 mm, P=0.021). On the other hand, there was no significant difference in the thickness of the middle and posterior CTI between the two groups. The time to reach the minimum freezing temperature showed a significant positive correlation with the thickness of the CTI (R=0.415, P<0.001). Conclusions: The time to reach the minimum freezing temperature in the anterior CTI may predict a first-pass conductional block of CTI cryoablation. The thickness of the anterior CTI may relate to this mechanism.