Initial Pre-Clinical Evaluation of the Augmented Ultra-Low Temperature Cryoablation Catheter for Ventricular Ablations

Abstract

Introduction: Ultra-low Temperature Cryoablation (ULTC) using nitrogen cryogen near its boiling temperature of −196°C is a novel cardiac ablation modality capable of producing titratable lesions with depth exceeding 10 mm and has been recently introduced for catheter treatment of drug-refractory ventricular tachycardia (VT). The ablative action of ULTC can be further augmented by the expansion of the cryogen within the ablation element yielding even lower ablation temperatures while optimizing mechanical handling characteristics of the catheter. Methods: The purpose of this report is to assess the feasibility and document the first pre-clinical experience with acute endocardial lesion formation using augmented ultra-low temperature cryoablation in healthy porcine models. Results: A modified commercially available catheter was used to create 35 augmented ULTC lesions in four acute porcine and ovine models with energy applications durations ranging from 15 to 120 s. Lesion depth and morphology were evaluated on gross necropsy and histopathology, using Masson's trichrome staining. Lesion depth ranged from median of 5.0 to median of 12.5 mm, depending on ablation duration (p = 0.003), with frequent transmurality and lesion morphology exhibiting consistent features across the depth range. The post-ablation cardiac electrograms were reduced up to 89.4% in lesions with depth exceeding 10 mm. Conclusions: Augmented ULTC can be implemented using a catheter with physical handling characteristics similar to contemporary RF catheters and may allow significant reduction in ablation time compared to conventional ULTC for the equivalent lesion depth.