Mitral valve anatomy

🔬 1. Functional Anatomy of the Mitral Valve Apparatus

The mitral valve (MV) is a dynamic, integrated structure composed of:

✨ Leaflets
✨ Annulus
✨ Chordae tendineae
✨ Papillary muscles

Together, they ensure unidirectional blood flow from the left atrium → left ventricle while preventing systolic regurgitation.

📏 Normal mitral valve area: 4–6 cm² → allows low-resistance LV filling.

🍃 2. Leaflet Morphology & Dynamics

🧩 Structure

• Anterior leaflet (AML) → larger, more mobile

• Posterior leaflet (PML) → smaller, more segmented

📌 Features:

• Thickness ≈ 1 mm

• Funnel-shaped geometry

• Coaptation zone ≈ 5 mm (critical for competence)

🔍 Scallop Anatomy (Echo-Critical)

• Segments:

  • AML → A1, A2, A3

  • PML → P1, P2, P3

• Posterior leaflet contains 2 clefts

⚠️ Clinical Insight

• ↓ Coaptation → Functional MR

• ↑ Motion → Prolapse / Degenerative MR

💡 AML continuity with aortic valve explains:

• LVOT obstruction

• SAM in hypertrophic cardiomyopathy

🧱 3. Mitral Annulus: Dynamic Ring

⚙️ Structure

• Anterior annulus → fibrous 🧵

• Posterior annulus → muscular 💪 (more flexible)

🔄 Function

• Saddle-shaped 🎯

• Contracts in systole → improves coaptation

• Dilates in pathology

⚠️ Clinical Relevance

• Posterior annulus → prone to:

  • Dilation → Functional MR

  • Calcification → MAC

📌 LA enlargement → annular dilation → Atrial MR

🪢 4. Chordae Tendineae: Load Distribution System

📚 Types

• Primary chords
  ➤ Prevent prolapse (low load)

• Secondary chords
  ➤ Bear main systolic load

• Tertiary chords
  ➤ Maintain LV–valve continuity

⚠️ Clinical Insights

• Chord rupture → Acute MR ⚡

• Tethering → Ischemic MR

• Load imbalance → progressive dysfunction

🫀 5. Papillary Muscles: Ventricular Control System

🧩 Anatomy

• Anterolateral PM (AL)
  ➤ Larger | dual blood supply 🩸🩸

• Posteromedial PM (PM)
  ➤ Smaller | single blood supply ⚠️

⚠️ Clinical Insight

🚨 Posteromedial PM = ischemic weak point
→ Infarction → Acute severe MR

📌 LV remodeling → PM displacement → leaflet tethering

🔗 6. Commissures

• Anterolateral

• Posteromedial

🎯 Role:

• Ensure symmetric opening

• Determine MR jet origin

🖥️ 7. Echocardiographic Correlation

📡 Standard Views

• PLAX → leaflet motion & coaptation

• PSAX → commissures & valve orifice

• A4C / A2C / A3C → scallop localization

💡 Expert Tip

🎯 Segmental anatomy (A1–P1, A2–P2, A3–P3) is essential for:

• Surgical repair planning

• TEER (MitraClip targeting)

⚖️ 8. Pathophysiology Integration

🧬 Primary MR

• Leaflet disease

• Chordal rupture

🔄 Secondary MR

• LV remodeling → tethering

• LA dilation → annular dilation

💎 9. Advanced Clinical Pearls

✨ The MV is a ventricular-driven valve
✨ Geometry > structure in many cases
✨ Posteromedial PM = Achilles’ heel
✨ Coaptation length = key echo marker

🧠 Take-Home Message

The mitral valve is a highly coordinated biomechanical system where failure of any component leads to dysfunction.

👉 True mastery comes from understanding:

• Structure 🧩

• Dynamics 🔄

• Ventricular interaction 🫀