Notes on Mitral Valve Function and Pathology

Function of the Mitral Valve

• Ensures one-way blood flow from the left atrium to the left ventricle.
• Diastole:
  • Valve opens when left atrial pressure > left ventricular pressure.
  • Allows blood to fill the left ventricle.
• Systole:
  • Valve closes when pressure gradient reverses.
  • Prevents backflow to the atrium during ventricular contraction.

Structure of the Mitral Valve

• Composed of two flaps:
  • Anterior Mitral Leaflet
  • Posterior Mitral Leaflet
• Supported by a fibrous ring known as the mitral annulus.
• Papillary Muscles:
  • Keep leaflets from opening in the wrong direction during contraction.
  • Attach to leaflets via chordae tendiniae (tendinous cords).

Mitral Valve Prolapse (MVP)

• Most common heart valve disease.
• Characterized by leaflets bulging into the left atrium during ventricular contraction.
• Causes:
  • Often unclear; potentially linked to connective tissue disorders (e.g., Ehlers-Danlos, Marfan syndrome).
  • Weakening of leaflets, increased leaflet area, and elongation of chordae tendiniae.
• Symptoms and Risks:
  • Most cases are asymptomatic and do not require treatment.
  • Increases risk of other heart diseases:
    • Arrhythmias
    • Endocarditis
    • Mitral Valve Regurgitation (MVR)
      • MVP is the most common cause of MVR.
      • Billowing leaflets may not fit together properly, causing leakage.
      • Elongated cords may rupture, leading to backflow during contraction.

Complications of Mitral Valve Regurgitation

• Volume overload on the left side of the heart.
• Can lead to heart failure and pulmonary congestion.
• Characteristic abnormal heart sounds:
  • Clicks
  • Murmurs (can be detected during auscultation).

Diagnosis

• Confirmed by echocardiography (ultrasound visualization of heart valves and blood flow).

Treatment Options

• Leaky Valve:
  • Requires surgical repair or replacement.
• Valve Repair Surgery:
  • Floppy portions of the valve are removed; remaining parts are reconnected.
  • May include annuloplasty (tightening/replacing the mitral annulus).
• Valve Replacement:
  • Considered when repair is not possible.
  • Types of artificial valves:
    • Mechanical Valves:
      • Last longer but require lifelong anticoagulant medications.
    • Bioprosthetic Valves:
      • Typically less durable than mechanical valves.