The MOST common cause of tricuspid regurgitation is secondary to:
Rheumatic hea disease
Dilatation of right ventricle
Coronary aery disease
Endocarditis due to intravenous drug abuse
All mentioned condition are causes of tricuspid regurgitation. Most commonly, TR is secondary to marked dilation of the tricuspid annulus from RV enlargement due to PA hypeension. Ref: Harrisons principles of internal medicine, 18th edition, Page 1948.