What causes tricuspid regurgitation with normal tricuspid valve leaflets?

Causes of Tricuspid Regurgitation with Normal Leaflets

Tricuspid regurgitation with structurally normal leaflets is most commonly secondary (functional) TR, caused by right ventricular dysfunction and/or tricuspid annular dilatation in response to pressure or volume overload, rather than primary valve pathology. 1

Primary Mechanism: Functional (Secondary) TR

The fundamental pathophysiology involves three interconnected processes: 1

• Tricuspid annular dilatation - The annulus loses its normal saddle-shaped configuration, becoming flat, planar, and distorted with diastolic diameter >21 mm/m² (>35 mm absolute) 1
• Leaflet tethering - Progressive RV remodeling causes papillary muscle displacement and apical displacement of leaflets, preventing proper coaptation 1
• Loss of annular contraction - Normal 25% systolic contraction of the annulus is impaired 1

Key Quantitative Markers of Functional TR:

• Tenting area >1 cm² indicates severe functional TR 1
• Coaptation distance (distance from annular plane to coaptation point) >0.76 cm predicts persistent TR 1

Underlying Causes of RV Dysfunction Leading to Functional TR

Pressure Overload Conditions 1

• Pulmonary hypertension (any etiology) - Systolic PA pressures >55 mm Hg commonly cause TR with anatomically normal valves 1
• Left-sided valve disease - Particularly mitral stenosis or mitral regurgitation causing elevated pulmonary pressures 1
• Pulmonic valve stenosis 1
• Pulmonary embolism (acute or chronic thromboembolic) 2

Volume Overload Conditions 1

• RV diastolic hypertension from:
  • Dilated cardiomyopathy 1
  • RV infarction 1
  • RV failure of any cause 1

Atrial Factors 3, 4

• Chronic atrial fibrillation - Causes isolated annular dilatation even without other cardiac abnormalities 3, 4
• Right atrial enlargement - Creates progressive annular dilatation 1

Iatrogenic Causes 1

• Intra-annular RV pacemaker or ICD leads - Can cause functional TR through mechanical interference 1
• Post-cardiac transplant (biopsy-related trauma) 1

The Self-Perpetuating Cycle

Critical concept: TR itself creates a vicious cycle where regurgitation leads to further RV dilation, which causes more annular dilatation and leaflet tethering, worsening the TR 1. This explains why:

• TR may not resolve after correcting the initial cause (e.g., mitral valve surgery) 3
• Late TR can appear years after initial cardiac surgery 3
• Isolated tricuspid surgery has poor outcomes once RV dysfunction is established 3, 4

Ventricular Interdependence Effects

With severe RV dilation, the interventricular septum shifts toward the LV, causing: 1, 2

• Reduced LV cavity size and restricted LV filling 1
• Increased LV diastolic pressure 1
• Biventricular diastolic dysfunction 2

Clinical Pitfall

**The most common error is assuming TR <40 mm Hg PA pressure indicates primary valve pathology** - while this correlation exists, functional TR can occur at lower pressures if significant annular dilatation is present (>35 mm or >21 mm/m²) 1. Always measure annular dimensions directly rather than relying solely on PA pressure estimates.

Approximately 80% of Significant TR Cases

Functional TR accounts for approximately 80% of all significant tricuspid regurgitation cases, with the remaining 20% due to primary valve abnormalities (endocarditis, rheumatic disease, carcinoid, trauma, congenital anomalies, etc.) 1.