Division of Cardiology, Department of Medicine, The University of Illinois at Chicago (B.A., A.K., G.S.K., K.S.L.); Medtronic Corporation, Montreal, Quebec, Canada (N.C.); and Medtronic, Minneapolis, MN (T.L.).
Circ Arrhythm Electrophysiol. 2018 Apr;11(4):e005949. doi: 10.1161/CIRCEP.117.005949.
The success of cryoablation of the pulmonary vein isolation (PVI) is dependent on transmural and circumferential ice formation. We hypothesize that rising impedance recorded from a ring electrode placed 2 mm from the cryoballoon signifies ice formation covering the balloon surface and indicates ice expansion. The impedance level enables titration of the cryoapplication time to avoid extracardiac damage while ensuring PVI.
In 12 canines, a total of 57 pulmonary veins were targeted for isolation. Two cryoapplications were delivered per vein with a minimum of 90 and maximum of 180-second duration. Cryoapplication was terminated on reaching a 500 Ω change from baseline. Animals recovered 38±6 days post-procedure, and veins were assessed electrically for isolation. Heart tissue was histologically analyzed. Extracardiac structures were examined for damage. PVI was achieved in 100% of the veins if the impedance reached 500 Ω in <90 seconds with freeze time of 90 seconds. When 500 Ω was reached >90 to 180 seconds (142.60±29.3 seconds), 90% PVI was achieved. When the final impedance was between 200 and 500 Ω with 180 seconds of freeze time, PVI was achieved in 86.8%. For impedance of <200 Ω, PVI was achieved in 14%. No extracardiac damage was recorded.
Impedance rise of 500 Ω at <90 seconds with freeze time of 90 seconds resulted in 100% PVI. Impedance measurements from the nose of the balloon is a direct measure of ice formation on the balloon. It provides real-time feedback on the quality of the ablation and defines the cryoapplication termination time based on ice formation, limiting ice expansion to extracardiac tissues.
冷冻球囊肺静脉隔离（PVI）的成功取决于球囊表面的透壁和环形冰形成。我们假设，距离冷冻球囊 2 毫米处的环形电极记录到的阻抗升高表明覆盖在球囊表面的冰形成，并指示冰的膨胀。阻抗水平可用于滴定冷冻球囊的应用时间，以避免心脏外组织损伤，同时确保 PVI。
在 12 只犬中，共有 57 条肺静脉被靶向隔离。每条静脉进行 2 次冷冻球囊应用，冷冻时间最短 90 秒，最长 180 秒。当阻抗从基线变化达到 500 Ω 时，冷冻球囊应用终止。动物在术后 38±6 天恢复，对静脉进行电隔离评估。对心脏组织进行组织学分析。检查心脏外结构是否有损伤。如果阻抗在 <90 秒内达到 500 Ω，冷冻时间为 90 秒，则 100%的静脉可实现 PVI。当阻抗在 90 至 180 秒（142.60±29.3 秒）达到 500 Ω 时，90%的静脉可实现 PVI。当最终阻抗在 200 至 500 Ω 之间，冷冻时间为 180 秒时，86.8%的静脉可实现 PVI。当阻抗 <200 Ω 时，14%的静脉可实现 PVI。未记录到心脏外组织损伤。
冷冻时间为 90 秒时，阻抗在 <90 秒内升高至 500 Ω，可实现 100%的 PVI。球囊头部的阻抗测量是球囊表面冰形成的直接测量。它提供了消融质量的实时反馈，并根据冰的形成定义冷冻球囊的应用终止时间，将冰的扩展限制在心脏外组织。
