Atrial Functional MR Mechanism — EECC MCQ

Correct answer: A — Atrial functional MR (AFMR) results from LA dilatation and mitral annular dilatation caused by long-standing AF — the valve leaflets are structurally normal but fail to coapt due to annular stretching; successful AF ablation with LA reverse remodelling can reduce MR severity

Atrial functional MR (AFMR) is an increasingly recognised mechanism of secondary MR distinct from ventricular functional MR: (1) mechanism: long-standing AF → LA dilatation → mitral annular dilatation (annulus loses its saddle shape, becomes flat/circular) → incomplete leaflet coaptation → MR; (2) the valve leaflets are structurally normal (no prolapse, no restriction); (3) LV function is typically preserved (no LV wall motion abnormality contributing to MR); (4) treatment: AF management (ablation for rhythm control) may reverse LA remodelling and reduce annular dilatation, improving MR — this is why early rhythm control is preferred in AF patients with significant AFMR. The 2025 ESC VHD Guidelines recognise AFMR as a distinct entity. If AFMR persists despite AF treatment, transcatheter annuloplasty or surgical ring annuloplasty may be considered.

Reference: ESC/EACTS (2025): VHD Guidelines; ESC (2024): AF Guidelines