<prompt> The MOST common cause of tricuspid regurgitation is secondary to:Rheumatic hea diseaseDilatation of right ventricleCoronary aery diseaseEndocarditis due to intravenous drug abuse  <response>: 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. 