What the Tricuspid Valve Does
The tricuspid valve is located between the right atrium and right ventricle and functions to prevent blood backflow from the right ventricle into the right atrium during ventricular contraction. 1
Anatomical Structure
The tricuspid valve complex consists of several integrated components that work together to ensure unidirectional blood flow:
- Annulus: A saddle-shaped fibrous ring that anchors the valve leaflets, normally measuring 28 ± 5 mm in diameter in adults 1, 2
- Three leaflets of unequal size: The anterior leaflet (largest), septal leaflet, and posterior leaflet 1
- Subvalvular apparatus: Including papillary muscles and chordae tendineae that attach to and support the leaflets 1, 2
- Right ventricular myocardium: The valve function is intimately connected to right ventricular geometry and loading conditions 2
Leaflet Characteristics
The three leaflets have distinct anatomical features:
- Anterior leaflet: Extends from the infundibular region anteriorly to the inferolateral wall posteriorly and is typically the largest 1
- Septal leaflet: Extends from the interventricular septum to the posterior ventricular border, with characteristically apical insertion relative to the mitral valve 1
- Posterior leaflet: Attaches along the posterior margin of the annulus from the septum to the inferolateral wall 1
Functional Mechanics
The valve operates within a dynamic mechanical environment:
- Cyclic loading: The leaflets experience shear, bending, tensile, and compressive forces repeated nearly three billion times over a lifetime 3
- Anisotropic mechanical properties: All three leaflets are stiffer in the circumferential direction compared to the radial direction, with the posterior leaflet being the most anisotropic 4
- Annular contraction: The normal tricuspid annulus contracts by 25% during systole, reducing its area to facilitate leaflet coaptation 1
- Saddle-shaped geometry: The annulus maintains a non-planar, elliptical saddle shape with two high points oriented toward the right atrium and two low points toward the right ventricle 1
Clinical Significance
Understanding tricuspid valve function is essential because:
- Mild tricuspid regurgitation is common and benign, but moderate and severe tricuspid regurgitation are associated with poor prognosis 1
- Functional (secondary) tricuspid regurgitation accounts for approximately 80% of significant tricuspid regurgitation cases and results from right ventricular dilation and/or annular dilatation rather than primary valve pathology 5
- Ventricular interdependence: Severe right ventricular dilation from tricuspid regurgitation can shift the interventricular septum toward the left ventricle, restricting left ventricular filling and causing biventricular diastolic dysfunction 1, 5
Key Pathophysiologic Thresholds
- Annular dilatation: A diastolic diameter >21 mm/m² (>35 mm absolute) indicates significant dilatation that predisposes to functional tricuspid regurgitation 1, 5
- Tenting area: A systolic tenting area >1 cm² (measured between the annular plane and leaflet bodies) indicates severe functional tricuspid regurgitation 1, 5
- Coaptation distance: A distance >0.76 cm from the annular plane to the coaptation point predicts persistent tricuspid regurgitation 5
Common Clinical Pitfall
**Do not assume that tricuspid regurgitation with pulmonary artery systolic pressure <40 mmHg indicates primary valve pathology**—functional tricuspid regurgitation can occur at lower pressures when significant annular dilatation is present (>35 mm or >21 mm/m²). 5