Failure of the tricuspid valve of the heart to close tightly, causing it to regurgitate (leak); also known as tricuspid regurgitation. The tricuspid valve connects the right atrium (upper chamber) of the heart with the right ventricle (lower chamber). Leakage from the right ventricle back into the right atrium reduces the flow of blood to the lungs. The tricuspid valve usually leaks because of enlargement of the right ventricle, a condition that can result from a number of diseases, including pulmonary hypertension (abnormally high blood pressure in the blood vessels in the lungs). In addition, the tricuspid valve can be damaged by rheumatic fever.