Mitral valve

Function

The mitral valve — named for a bishop's mitre — has but two leaflets mastering the highest pressures in the heart. Its anterior leaflet is the grand curtain of the left ventricular inflow; its posterior leaflet anchors the coaptation line against the annulus.

The chordae-papillary system acts as a self-adjusting suspension: as the ventricle contracts, papillary muscles tense first to keep the leaflets from prolapsing — a mechanical orchestra timed in milliseconds. Its closure is the loudest component of S1.

Blood supply

Leaflets are largely avascular; the anterolateral papillary muscle has a dual supply (LAD diagonals and circumflex), the posteromedial usually only the posterior descending artery — why it ruptures more often after inferior MI.

Nerve supply

Atrial branches of the autonomic plexus.

Clinical relevance

Mitral valve prolapse

Myxomatous degeneration lets leaflets billow into the atrium — a mid-systolic click and late murmur; one of the commonest valve disorders, usually benign.

Mitral regurgitation

Systolic backflow floods the lungs' venous side with a pan-systolic murmur radiating to the axilla.

Related conditions

• Mitral valve regurgitation
• Infective endocarditis
• Rheumatic heart disease