A Randomized Controlled Trial of the Size-adjustable Cryoballoon vs. Conventional Cryoballoon for Paroxysmal Atrial Fibrillation: The CONTRAST CRYO II trial Rationale and Design

Background Pulmonary vein isolation (PVI) with cryoballoon technology is a well-established therapy for atrial fibrillation (AF) patients. Most recently, a size-adjustable cryoballoon (POLARx FIT) that enables delivery as a standard 28mm or expanded 31mm size was introduced. Objective The study sought to perform a randomized clinical trial to evaluate the safety and efficacy of this novel cryoballoon as compared to the conventional cryoballoon. Methods The CONTRAST-CRYO II trial is a multicenter, prospective, open-label, randomized controlled trial in which 214 patients with paroxysmal AF will be randomized 1:1 to receive cryoballoon ablation with either a conventional cryoballoon (Arctic Front AdvanceTM Pro) or size-adjustable cryoballoon. This study was approved by the Institutional Review Boards at all investigational sites and has been registered in the UMIN Clinical Trials Registry (UMIN000052500). Results The primary endpoint of this study will be the incidence of phrenic nerve injury. The secondary endpoints include the procedure success, chronic success through 12 months, procedure-related adverse events, biophysiological parameters during applications for each PV, total procedure and fluoroscopy time, level of the PVI and isolation area, and probability of non-PV foci initiating AF. Conclusion The CONTRAST-CRYO II trial is a multicenter, prospective, randomized controlled trial designed to assess the safety and efficacy of the POLARxTM FIT by comparing the AFA-Pro. The findings from this trial will provide additional utility data on the efficacy of the size-adjustable cryoballoon for isolating pulmonary veins in patients with paroxysmal AF.