Cryoablation as an alternative strategy for bidirectional cavotricuspid isthmus block following multiple failed sessions of radiofrequency ablation due to epicardial-endocardial breakthrough: A case report

Cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) is difficult to manage with antiarrhythmic drugs, with radiofrequency (RF) ablation being the standard treatment. However, achieving a bidirectional CTI block can be challenging due to complex anatomy and epicardial-endocardial breakthrough (EEB). This case report illustrates that cryoablation can serve as an effective bail-out strategy to achieve a permanent CTI block when RF ablation fails, particularly in cases complicated by EEB. We present the case of a 66-year-old woman who underwent multiple catheter ablations for persistent atrial fibrillation (AF) and CTI-dependent AFL. Despite two prior sessions of RF-based CTI ablation, a durable bidirectional block was not achieved. During her fourth ablation, recurrent AFL persisted despite extensive RF applications. Cryothermal ablation, utilizing a Freezor MAX catheter with point-by-point freezing along the CTI line, successfully terminated the AFL and created a durable bidirectional CTI block. While RF ablation remains the primary treatment for CTI-dependent AFL, the formation of a durable bidirectional CTI block can be challenging due to complex CTI anatomy, EEB, and tissue edema. Cryothermal ablation offers a viable alternative in these difficult cases. The enhanced tissue adhesion and improved catheter stability provided by cryoablation, along with the reduced risk of steam pops, allow for more consistent lesion formation. This case underscores the utility of cryoablation as a bail-out strategy when RF ablation alone is insufficient.