CMR Detected Atrial Structural and Functional Remodeling in AF HFrEF: Ablation vs Medical Rate Control

Atrial remodeling is pathological in heart failure with reduced ejection fraction (HFrEF) and atrial fibrillation (AF). The impact of catheter ablation (CA) compared with medical rate control (MRC) for contractile atrial function in AF HFrEF patients, and its effect on exercise capacity has not been explored.

This study aimed to assess cardiac magnetic resonance changes in biatrial parameters and exercise capacity in AF HFrEF patients from the CAMERA-MRI (Catheter Ablation Versus Medical Rate Control of Atrial Fibrillation) and CAMERA-MRI II (Catheter Ablation Versus Medical Rtae Control of Atrial Fibrillation with Systolic Heart Failure and Myocardial Fibrosis) multicenter studies, comparing CA to MRC.

Biatrial parameters (atrial ejection fraction [EF], indexed volumes) were assessed by serial cardiac magnetic resonance (baseline and ≥6 months). Exercise capacity was assessed by serial 6-minute walk test (6MWT).

In total, 123 patients (age 60.7 ± 11.1 years, 17 women, 82 CA, 41 MRC) were included. Baseline atrial measurements and 6MWT distance were similar between groups. CA patients had reverse remodeling of all structural and functional biatrial parameters (P < 0.001), with no change in any parameters for MRC. On multivariable analysis, Δ left atrial emptying fraction (LAEF) (95% CI: 0.23-0.54; P < 0.001) and AF burden (95% CI: -0.16 to -0.01; P = 0.020) remained independently associated with Δ left ventricular (LV) EF, whereas sinus rhythm at follow-up was no longer significant (P = 0.865). 6MWT improved in 20 (48.8%) MRC vs 63 (76.8%) CA patients (P = 0.002). Univariable predictors of Δ6MWT included ΔLAEF (R = 0.27; 95% CI: 0.52-2.47; P = 0.003), ΔLVEF (R = 0.23; 95% CI: 0.33-2.52; P = 0.011), and AF burden (R = 0.27; 95% CI: -1.15 to -0.19; P = 0.007), but none remained significant on multivariable analysis.

Sinus rhythm restoration with CA, along with reduction in biatrial size, led to increases in biatrial EF compared with MRC. AF burden, over the binary endpoint of rhythm at follow-up, better predicted changes in LAEF, functional status, and LVEF. LAEF predicts improvements in LVEF over the endpoint of sinus rhythm at follow-up, suggesting that restoration of atrial contractile function is a key feature of recovery in HFrEF.