Pathophysiology of recurrent atrial fibrillation after initial cryoballoon ablation and clinical outcome of the second ablation

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: There are limited clinical studies on recurrent atrial fibrillation (AF) mechanisms after initial cryoballoon ablation (CBA). PURPOSE: We aimed to elucidate the mechanisms of AF recurrence after CBA based on electrophysiological findings obtained during the second ablation and the response to treatment. METHODS: Of 885 patients who underwent CBA at our hospital between 2016 and 2022, 50 (5.7%) patients (age 68 ± 9.2 years, 62% male, 52 % paroxysmal AF, body mass index (BMI) 25 ± 3.8 kg/m2, left atrial diameter (LAD) 44 ± 5.9mm, left ventricular ejection fraction (LVEF) 66 ± 11%, CHADS2 score 1.9 ± 1.4) were included. All the patients were treated with an Arctic Front Advance™ in the initial CBA. Each pulmonary vein (PV) was treated with a target time of 180 sec. Routine left atrial roof line and posterior wall isolation was not created. However, tricuspid valve isthmus isolation (CTI) and superior vena cava (SVC) isolation were added as required. The findings obtained with the 3D-mapping system during the second ablation were analyzed. Furthermore, the contents of the second ablation and the clinical outcomes were investigated. RESULTS: The first ablation successfully isolated PVs in all patients, and additional radiofrequency ablations were CTI ablation in 28 patients and superior vena cava (SVC) isolation in 6 patients. The second ablation was done after 24±16 months. At recurrence, persistent AF was 24%. Furthermore, atrial flutter was recorded in 16% of the 50 cases. The 3D-mapping systems used for guidance were RHYTHMIA HDx™ in 42 cases, CART-XP™ in 5 cases and EnSite NavX™ in 3 cases. Electrical reconnection of PV was detected in 14 patients. They included seven left-superior PVs, two left-inferior PVs, two left-common PVs, four right-superior PVs and five right-inferior PVs. There were 11 cases of conduction only in the carina area, five with left-sided and six with right-sided. All second ablations were treated with high-frequency irrigation catheters. The treatments were PV re-isolation in 14 patients, isolation area expanding in 43 patients, SVC isolation in 24 patients, CTI ablation in 3 patients, and mitral isthmus ablation in 2 patients. After 24.8 ± 14.9 months, treatment outcomes were as follows; AF was completely cured in 23 patients, anti-arrhythmic drugs were required in 23 patients, and no effects in 4 patients. Comparing the completely cured patients’ group (23 patients) with the other (27 patients), age (65.1 ± 9.3 years vs 70.5 ± 8.6 years, p < 0.05) and CHADS2 score (1.5 ± 1.3 vs 2.3 ± 1.3, p < 0.05) have significant differences. There were no differences in the presence of PV reconnection, BMI, LAD, LVEF and second ablation contents. CONCLUSION: In patients with recurrent AF after CBA, less than 30% had PV-reconnection, and its disappearance was not associated with AF disappearance. Non-PV foci, except SVC origin, might cause recurrent AF after CBA.