Atrioventricular (AV) Valves: Chordae Tendineae & Papillary Muscles in Valve Function

AV Valve Anatomy

• Mitral (Bicuspid) Valve: Left atrium → left ventricle. 2 leaflets (anterior, posterior).
• Tricuspid Valve: Right atrium → right ventricle. 3 leaflets (anterior, posterior, septal).

Each leaflet edge attaches to chordae tendineae (fibrous cords) → papillary muscles (anterolateral & posteromedial in LV; anterior, posterior, septal in RV).

Why This Apparatus Is Essential

1. Prevents Prolapse/Regurgitation During Systole: When ventricles contract, pressure forces valves shut. Papillary muscles contract simultaneously, tensing chordae → prevent leaflets from billowing back into atria.
2. Maintains Coaptation: Chordae distribute tension evenly across leaflet free edges → tight seal.
3. Allows Passive Opening in Diastole: When ventricles relax, pressure drops; chordae go slack; leaflets open passively like trapdoors.
4. Adapts to Volume/Pressure Changes: Papillary muscle contraction modulates chordal tension beat-to-beat.
5. Structural Integrity: Prevents leaflet flail/rupture under high pressure.

Pathology When Apparatus Fails

• Papillary Muscle Rupture (Post-MI): Acute severe MR → flash pulmonary edema.
• Chordal Rupture: Flail leaflet → chronic severe MR.
• Ischemic/Functional MR: Papillary displacement (LV dilation) → tethering → incomplete closure.
• Myxomatous Degeneration (Mitral Valve Prolapse): Redundant leaflets + elongated chordae → prolapse.

Clinical Pearl

The AV valve apparatus is a tension-based suspension system, not a rigid hinge. Its dynamic coordination with ventricular systole ensures unidirectional flow without imposing significant resistance.