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Atrioventricular (AV) Valves: Structure, Function, and Clinical Significance

The AV valves ensure unidirectional blood flow from atria to ventricles. There are two:

1. Mitral (Bicuspid) Valve

  • Left atrium → left ventricle
  • Two leaflets (anterior, posterior)
  • Chordae tendineae → papillary muscles (anterolateral, posteromedial)

2. Tricuspid Valve

  • Right atrium → right ventricle
  • Three leaflets (anterior, posterior, septal)
  • Chordae → papillary muscles (anterior, posterior, septal)

Primary Functions

  1. Prevent Regurgitation: Close during ventricular systole (S₁ = closure sound).
  2. Allow Diastolic Filling: Open during ventricular diastole (passive + atrial kick).
  3. Prevent Ventricular Overfilling: Limit end-diastolic volume.
  4. Contribute to Heart Sounds: S₁ (mitral + tricuspid closure); S₂ (aortic + pulmonic closure).

Common Pathologies

ConditionMechanismKey Features
Mitral Regurgitation (MR)Leaflet prolapse, chordae rupture, annular dilation, ischemic papillary dysfunctionHolysystolic murmur at apex, LV dilation, AF risk
Mitral Stenosis (MS)Rheumatic fusion/commissural calcificationDiastolic rumble, LA enlargement, AF, pulmonary HTN
Tricuspid Regurgitation (TR)RV dilation (pulm HTN), infective endocarditis (IVDU), carcinoidSystolic murmur LLSB, JVD, hepatic pulsation
Tricuspid Stenosis (TS)Rare; rheumatic, carcinoidDiastolic murmur LLSB, RA enlargement

Clinical Importance

AV valve dysfunction → volume/pressure overload → chamber remodeling → heart failure, arrhythmias. Echocardiography is primary diagnostic tool. Intervention (repair/replacement) guided by symptoms, ventricular function, and severity.

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