Treatment-Related Changes in Left Atrial Structure in Atrial Fibrillation: Findings From the CABANA Imaging Substudy

Abstract

Background: The CABANA trial (Catheter Ablation Versus Antiarrhythmic Drug Therapy for Atrial Fibrillation) was a randomized, prospective trial of left atrial catheter ablation versus drug therapy for treatment of atrial fibrillation (AF). As part of CABANA, a prospective imaging substudy was conducted. The main objectives were to describe the patterns of changes in the dimensions of the left atrium and pulmonary veins (PVs), and the relationship between these changes with treatment assignment and clinical outcomes. Methods: Computed tomography or magnetic resonance imaging was acquired at baseline and follow-up in 121 ablation (median follow-up 101 days) and 85 drug patients (median follow-up 97 days). Left atrial volume index, mean PV ostial diameter, and ostial diameters of each PV separately were computed. We examined the relationship between the change from baseline to follow-up with subsequent clinical outcomes (composite of death, disabling stroke, serious bleeding, or cardiac arrest [CABANA primary end point], total mortality or cardiovascular hospitalization, first AF recurrence after the 90-day blanking period, first AF/atrial flutter/atrial tachycardia after the 90-day blanking period) using Cox proportional-hazards models. Results: The median (25th to 75th) change from baseline for left atrial volume index was-7.8 mL/m2(-16.4 to 0.2), ablation arm and-3.5 mL/m2(-11.4 to 2.6), drug therapy arm. The left atrial volume index decreased in 52.9% of ablation patients versus 40.0% of drug therapy patients. Change for mean PV was-2.7 mm (-4.2 to-1.3) in the ablation arm versus-0.1 mm (-1.5 to 0.8) in the drug therapy arm. Changes in left atrium and PV dimensions had no consistent relationship with the risk of developing the study primary end point. Reductions in left atrial volume index, and in mean PV diameter were associated with decreased risk of AF recurrence. Conclusions: Ablation patients demonstrated more frequent and larger atrial structural changes compared with drug patients. These changes suggest a critical relationship between structural features and AF generation.