Impact of atrial fibrillation on improvement of functional mitral regurgitation in cardiac resynchronization therapy

Functional mitral regurgitation (FMR) and atrial fibrillation (AF) are frequent heart failure (HF) complications. Cardiac resynchronization therapy (CRT) can improve FMR; however, little is known about the influence of AF on FMR improvement.The purpose of this study was to investigate the mechanisms and impact of baseline AF on FMR improvement after CRT.CRT recipients with HF, AF, or sinus rhythm (SR) at baseline with moderate or severe FMR, were included from an ongoing registry. Left atrial (LA), mitral annular (MA), and left ventricular (LV) dimensions were evaluated echocardiographically. FMR improvement was defined as ≥1 grade decrease from baseline to 6-month follow-up. Clinical and echocardiographic measurements were performed at baseline and 6-month follow-up.A total of 419 patients (age 66 ± 8 years; 73% male) were analyzed. At 6-month follow-up, FMR improved in 145 patients (45.6%) with SR vs 31 of AF patients (30.7%) (P = .011). Despite similar LV reverse remodeling at 6 months after CRT (LV end-systolic volume decreased by 32.1 ± 43.2 mL in the SR group and by 27.7 ± 6.3 mL in those with AF; P = .353), patients with SR exhibited smaller LA volumes (63.0 ± 26.5 mL vs 103.1 ± 41.0 mL; P <.001) and MA diameters (42.3 ± 5.6 mm vs 46.1 ± 5.8 mm; P <.001) compared to AF patients.FMR improvement is more common in CRT recipients in SR vs AF, despite a similar degree of LV remodeling. LA volume and MA diameter are greater in the AF group, causing the negative impact of AF on FMR improvement in CRT, as well as indicating a potential therapeutic target (ie, AF rhythm control).