Sandeep Prabhu, Ben T Costello, Andrew J Taylor, Sarah J Gutman, Aleksandr Voskoboinik, Alex J A McLellan, Kah Y Peck, Hariharan Sugumar, Leah Iles, Bhupesh Pathik, Chrishan J Nalliah, Geoff R Wong, Sonia M Azzopardi, Geoffrey Lee, Justin Mariani, David M Kaye, Liang-Han Ling, Jonathan M Kalman, Peter M Kistler

This study sought to determine if diffuse ventricular fibrosis improves in patients with atrial fibrillation (AF)-mediated cardiomyopathy following the restoration of sinus rhythm. AF coexists in 30% of heart failure (HF) patients and may be an underrecognized reversible cause of left ventricular systolic dysfunction. Myocardial fibrosis is the hallmark of adverse cardiac remodeling in HF, yet its reversibility is unclear. Patients with persistent AF and an idiopathic cardiomyopathy (left ventricular ejection fraction [LVEF] ≤45%) were randomized to catheter ablation (CA) or ongoing medical rate control as a pre-specified substudy of the CAMERA-MRI (Catheter Ablation versus Medical Rate Control in Atrial Fibrillation and Systolic Dysfunction-an MRI-Guided Multi-centre Randomised Controlled Trial) trial. All patients had cardiac magnetic resonance imaging scans (including myocardial T1 time), serum B-type natriuretic peptide, 6-min walk tests, and Short Form-36 questionnaires performed at baseline and 6 months. Sixteen patients with no history of AF or left ventricular systolic dysfunction were enrolled as normal controls for T1 time. Thirty-six patients (18 in each treatment arm) were included in this substudy. Demographics, comorbidities, and myocardial T1 times were well matched at baseline. At 6 months, patients in the CA group had a significant reduction in myocardial T1 time from baseline compared with the medical rate control group (-124 ms; 95% confidence interval [CI]: -23 to -225 ms; p = 0.0176), although it remained higher than that of normal controls at 6 months (p = 0.0017). Improvements in myocardial T1 time with CA were associated with significant improvements in absolute LVEF (+12.5%; 95% CI: 5.9% to 19.0%; p = 0.0004), left ventricular end-systolic volume (p = 0.0019), and serum B-type natriuretic peptide (-216 ng/l; 95% CI: -23 to -225 ng/l; p = 0.0125). The improvement in LVEF and reverse ventricular remodeling following successful CA of AF-mediated cardiomyopathy is accompanied by a regression of diffuse fibrosis. This suggests timely treatment of arrhythmia-mediated cardiomyopathy may minimize irreversible ventricular remodeling.