Abstract 4143185: Association between Secondary Mitral Regurgitation and Left Atrial Structural Abnormalities in Atrial Fibrillation

Background: Atrial fibrillation (AF) is increasingly recognized as a cause of secondary mitral regurgitation (SMR), exacerbating heart failure symptoms and complicating the management of AF. Hypothesis: SMR quantified using cardiac magnetic resonance (CMR) 4D flow is associated with left atrial (LA) structural derangements in patients with AF. Goals: To demonstrate an association between the atrial volume and fibrosis with mitral regurgitation severity Methods: Patients were recruited from the University of Washington Medical Center AF clinics. CMR was used to quantify LA fibrosis through late gadolinium enhancement, LA emptying fraction (LAEF), left ventricular end-diastolic volume (LVEDV), left ventricular ejection fraction (LVEF) (Panel A). Total mitral valve flow, regurgitant fraction, and peak velocity were quantified using CMR-derived 4D flow and cine images (Panel B). Patients with valvular disease (rheumatic valvular disease and prosthetic valves) were excluded from the analysis. Results: A total of 44 patients were included (71 years (64-76), 39% with persistent AF, BMI 28.8 kg/m 2 ± 6.2, 45% females, 43% hypertensive, and 20% with a history of heart failure). 4D flow quantified MR was at 14% (3.7-45) which represented the median percentage of mitral regurgitant flow (MR flow/Total Mitral Flow), total mitral flow 29.2 mL (14.2-60.8), and peak velocity 194.5 cm/s ± 72.6. Using CMR cine images, median LVEF was 62.4% (56.4-66), heart rate was 65 bpm (49.5-75), left atrial volume was 97.3±39.3 mL, LAEF was 42.4±18.5%, and LVEDV was 146±44.6 mL. Left atrial fibrosis was 14.0% ± 7.9. Using multivariable linear regression, there was a significant association between LA volume and MR fraction (β = 0.35, p=0.04) after adjusting for peak velocity, LAEF, fibrosis, LVEDV, LVEF, and HR. Moreover, there was an association between HR and MR fraction (β = -0.3; p=0.04) and between total mitral flow and MR fraction (β = -0.78; p<0.001). Conclusion: In a cohort of AF patients without primary valvular abnormalities, secondary mitral regurgitation quantified using 4D flow CMR was associated with advanced atrial remodeling manifesting through LA volume increase.