Implications of Atrial Fibrillation on the Mechanisms of Mitral Regurgitation and Response to MitraClip in the COAPT Trial

Background: Atrial fibrillation (AF), mitral regurgitation (MR), and left ventricular (LV) ejection fraction have a complex interplay. We evaluated the role of AF in patients with heart failure and moderate-to-severe or severe secondary MR enrolled in the randomized COAPT trial (Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients With Functional Mitral Regurgitation) and its impact on mechanisms and outcomes with the MitraClip.

Methods: Patients in the COAPT trial were stratified by the presence (n=327) or absence (n=287) of a history of AF and by assignment to treatment group. Clinical, echocardiographic, and outcome measures were assessed. The primary outcome was the composite rate of death or heart failure hospitalization at 24 months.

Results: Patients with history of AF were older and more often male. They had a higher LV ejection fraction, larger left atrial volumes and mitral valve orifice areas, smaller LV volumes, and similar MR severity. Patients with AF compared with those without a history of AF had a higher unadjusted (hazard ratio [HR], 1.32 [95% CI, 1.06–1.64], P=0.01) and adjusted (HR, 1.30 [1.03–1.64], P=0.03) 2-year rate of the primary outcome. Treatment with the MitraClip compared with guideline-directed medical therapy alone reduced death or heart failure hospitalization in both those with (HR, 0.61 [0.46–0.82]) and without (HR, 0.46 [0.33–0.66]) a history of AF (Pint=0.18). Treatment with the MitraClip was associated with a lower risk of stroke in patients with a history of AF (HR, 0.18 [0.04–0.86]) but not in those without a history of AF (HR, 1.64 [0.58–4.62]; Pint=0.02).

Conclusions: In the COAPT trial, patients with a history of AF had larger left atrial and mitral valve orifice areas with higher LV ejection fraction and smaller LV volumes, suggesting an atrial mechanism contribution to functional MR. Despite the worse prognosis of heart failure patients with a history of AF, MR reduction with the MitraClip still afforded substantial clinical benefits. Treatment with MitraClip was associated with a lower risk of stroke in patients with a history of AF.

Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01626079.