The differential diagnosis of tricuspid regurgitation is:

Annuluar Dilation 

Endocarditis

Carcinoid

Marfan's Syndrome

Injury

Rheumatoid Arthritis

Radiation

Rheumatic Fever

Fen-Phen (Phentermine-Fenfluramine) or Dexfenfluramine

Tricuspid Stenosis

Myxomatous Degeneration

Congenital (Ebstein's Anomaly)

Iatrogenic (Wire, Catheter)

Tricuspid regurgitation from annular dilation is due to right ventricular dilation which is from elevated pulmonary artery pressure (pulmonary hypertension) or pulmonary stenosis. The mechanisms for tricuspid regurgitation are classified into annuluar dilation, normal leaflet motion, leaflet restriction, or excessive leaflet motion. Annular dilation is the most common cause and is usually due to a problem downstream (PS, Pulm HT, MS, MR, etc) where the RV dilates. Normal motion could indicate a perforation or annular dilation. Excessive leaflet motion indicates a papillary or chordae tendinae rupture, prolapse or flail leaflet. Restricted leaflet motion is usually due to right ventricular dilation.

Therapy for severe tricuspid regurgitation depends upon the mechanism. A repair is preferable if the annulus is dilated. A ring or a DeVega procedure can be performed. A ring has been shown to have superior long term freedom from recurrent TR. If the leaflets cannot be repaired or if restriction is present, then replacement may be the best option. Restricted valves do not lend themselves to a mitral valve repair very easily.

The mechanism in this case is restricted leaflet motion from right ventricular dilation. Therefore, a tricuspid valve replacement is indicated.