Impact of Freezing Time and Balloon Size on the Thermodynamics and Isolation Efficacy During Pulmonary Vein Isolation Using the Second Generation Cryoballoon

Abstract

BackgroundRecently, pulmonary vein isolation (PVI) using the second generation cryoballoon, introduced as a therapy for patients with drug-refractory atrial fibrillation, has shown better outcomes than with the first generation cryoballoon. [1][2][3][4][5] However, some questions about the second generation cryoballoon remain. Several studies in cryobiology have shown that prolongation of freeze duration produces a greater destructive effect in noncardiac tissue. 6,7 However, ablation duration to achieve acute and long-term PVI is still debatable. It is also unclear how different sized balloons (23 and 28 mm) should be used, as the impact of the balloon size on tissue and balloon temperature profiles and ablative lesion size have not been studied. Information on the effects of ablation duration and balloon size is required to achieve high PVI success rates without severe complications using the second generation cryoballoon.The purpose of this study was to investigate the impact of ablation duration and balloon size on tissue and balloon thermodynamics, acute and chronic PVI success rates, complications, and chronic histological changes of the PV and left atrium (LA). Methods GeneralThis study was designed to compare the ablation effect and safety of different ablation durations (3 versus 4 minutes) and different balloon sizes (23 versus 28 mm) in an in vivo model. Twenty-six dogs underwent PVI using second generation cryoballoon. Animal PreparationThe protocol was approved by Mayo Foundation Institutional Animal Care and Use Committee. Dogs (30.3±2.5 kg) were anesthetized with intravenous ketamine and diazepam, intubated, and maintained on 1% to 3% isoflurane. The surface ECG, body temperature, and blood pressure were monitored. Tissue Temperature MonitoringTissue temperatures were monitored by implanted thermocouples, as reported previously. 8,9 All dogs underwent left/right thoracotomy for access to the superior/inferior PVs. The pericardium was opened to © 2015 American Heart Association, Inc. Original Article Circ Arrhythm ElectrophysiolBackground-The differences in ablation characteristics of freezing time and balloon size using second generation cryoballoon are still unknown. Methods and Results-Twenty-six dogs underwent pulmonary vein (PV) isolation. Balloon and tissue temperatures (left atrial-PV junction, phrenic nerve, and internal esophagus) were monitored. The ablation duration was randomized to either 3 or 4 minutes, which did not show significant differences in temperature profiles, PV isolation success rate, complications, or histological changes. Twenty dogs underwent cryoablation using 28-mm cryoballoon, 6 dogs were done using the 23-mm cryoballoon. Positioning of the 23-mm cryoballoon was more distal in the PV, which resulted in better PV occlusion. Temperature profiles showed lower temperatures in the 23-mm cryoballoon than in the 28-mm cryoballoon

Pulmonary Vein Isolation Using a Second‐Generation Cryoballoon in Patients With Paroxysmal Atrial Fibrillation: One‐Year Outcome Using a Single Big‐Balloon 3‐Minute Freeze Technique

“…The recommended freeze dose was 4 minutes with a bonus application based on the preclinical study data. However, recent clinical and experimental studies have shown that even a short freeze cycle, such as a single 3‐minute freeze technique without bonus applications, is effective in achieving an acute PVI and AF freedom. Therefore, a single 3‐minute freeze hypothetically might be sufficient with this new technology.…”

Single 3‐Minute versus Double 4‐Minute Freeze Strategy for Second‐Generation Cryoballoon Ablation: A Single‐Center Experience

“…During 4‐minute ablations, additional mean temperature drop from 3 to 4 minutes is roughly –1/–2 °C. These findings might be explained by previous experimental observations, reporting that cryoablation lesion size measured by ICE grows progressively during the first 3 minutes of freezing in atrial myocardium, and additional 1‐minute ablation duration (from 3 to 4 minutes) does not determine further benefit since adequate and transmural tissue damage is already achieved . Therefore, although optimal ablation duration remains to be defined, a single 3‐minute freeze might be sufficient with this novel technology.…”

“…However, the ideal freezing duration and the adequate number of cycles using the novel CB‐Adv remain to be determined. Although current recommendations suggest 4‐minute freeze duration using a bonus application, preclinical experiences showed that a shorter freeze cycle time is highly effective in terms of acute pulmonary vein isolation (PVI) . Moreover, recent clinical studies demonstrated that this novel catheter achieves durable PVI with significantly shorter freeze cycles duration with a promising rate of arrhythmia freedom in the mid‐term clinical follow‐up, questioning the need of an “insurance” freeze when isolation is already achieved .…”

Relationship between time‐to‐isolation and freeze duration: Computational modeling of dosing for Arctic Front Advance and Arctic Front Advance Pro cryoballoons

“…Similar in vivo experiments have been conducted that measure the cryoballoon freeze characteristics under different study design parameters . Specifically, direct surgical attachment of thermocouples into cardiac and surrounding tissues in canine models have measured time, temperature, and distance relationships during a cryoballoon freeze .…”