Ice mapping during cryothermal ablation of accessory pathways in WPW: the role of the temperature time constant

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Abstract
Aim: Cryothermal energy has the ability reversibly to demonstrate loss of function with cooling, ice mapping, at less deep temperatures. The purpose of this study was to investigate the time course of the temperature during ice mapping of accessory pathways. Methods and results: Thirteen patients with the Wolff–Parkinson–White (WPW) syndrome underwent cryoablation. After identification of a prospective ablation site, ice mapping was performed by cooling the tip to a minimum of −30 °C. Successful ice mapping was defined by loss of accessory pathway (AP) conduction. A total of 104 ice maps were analyzed. Successful ice mapping was demonstrated in 17 attempts. There was no significant difference in mapping temperature between successful and unsuccessful ice mapping (−29.4±3.2 °C vs −30.4±1.7 °C). The temperature time constant τ during successful ice mapping was significantly shorter compared with unsuccessful ice mapping (7.0±1.1 s vs 10.1±1.3 s; P<0.0001). The response time (RT) to mapping temperature of −30 °C was significantly prolonged in unsuccessful ice mapping attempts (35.8±4.5 s vs 53.5±11.0 s; P<0.0001). Significant correlations were found between successful ice mapping and the temperature time constant, and between RT and the temperature time constant (P<0.001). Conclusion: The ability to identify prospective ablation sites by ice mapping was demonstrated. Successful ice mapping attempts were characterized by a short temperature time constant and a short response time to mapping temperature with a sudden disappearance of pathway conduction.