Additional Low Voltage Area Ablation in Older Patients With Paroxysmal Atrial Fibrillation: a Randomized Control Trial of STABLE-SR-III

BACKGROUND: Atrial fibrillation (AF) is the most common cardiac rhythm disorder. Catheter ablation to the pulmonary veins isolation (PVI) electrically from the left atrium (LA) has been shown to be an effective treatment for paroxysmal AF (PAF). The consensus is that PVI alone is the main strategy for PAF ablation. Based on the results from our pilot study and STABLE-SR trial, that low-voltage modification beyond CPVI is very promising for persistent AF ablation. Whether the low voltage area modification combined with PVI improves outcomes is unclear in older patients with PAF.

AIM OF THE STUDY: The primary objective of this investigation is to compare the efficacy of two different AF ablation strategies in older patients with PAF: PVI alone versus additional low-voltage substrate modification during sinus rhythm. The primary endpoint is freedom from AF and/or ATs with or without antiarrhythmic drugs (AADs) at 12 months after a single-ablation procedure. AF and/or AT occurring in the first 3 months after the ablation (blanking period) was censored. Each atrial tachyarrhythmia episode lasts > 30 seconds monitored by ECG, 24-Holter or 7 days-Holter was defined as recurrence. The secondary endpoint are incidence of periprocedural complications, including stroke, PV stenosis, cardiac perforation, esophageal injury and death; procedure time; fluoroscopy time (including the total fluoroscopy time, during CPVI and after CPVI); the occurrence of the conversion from AF to AT, and its relationship with long-term outcome; the scar distribution and the relationship of success rate in older PAF patients.

STUDY DESIGN: This is a randomized, prospective, parallel, single-blind multicenter design. The expected freedom from atrial fibrillation in older patients after one ablation procedure was 75% for PVI. Previous study did not include a group assigned to isolation plus additional low-voltage substrate modification during sinus rhythm, so freedom form AF for this procedure was estimated from the literature at 85%. A log-rank test was used for sample-size calculation. To test whether the isolation plus low-voltage substrate modification was superior to isolation only. Then the 369 patients were needed, with a randomization ratio of 1:1, for the study to have a power of 90% at a two-sided alpha level of 0.05. Assuming a dropout rate of 15%, we need 434 patients. Patients are randomized in a 1:1 fashion into one of the investigation arms: CPVI plus low-voltage substrate modification in the left atrium during SR and CPVI alone. Follow-up for these patients includes visits at 3 m, 6 m, 9 m, 12 m.