Definition of Tricuspid regurgitation:

Tricuspid regurgitation is a disorder in which the heart's tricuspid valve does not close properly, causing blood to flow backward (leak) into the right upper heart chamber (atrium) when the right lower heart chamber (ventricle) contracts.

Causes, incidence, and risk factors:

The tricuspid valve separates the right lower heart chamber (the right ventricle) from the right upper heart chamber (right atrium).

The most common cause of tricuspid regurgitation is swelling of the right ventricle. Such swelling may be a complication of any disorder that causes failure of the right ventricle.

Other diseases can directly affect the tricuspid valve. The most common of these is rheumatic fever, which is a complication of untreated strep throat infections.

Tricuspid regurgitation affects about 4 out of 100,000 people. It may be found in those with a type of congenital heart disease called Ebstein's anomaly.

Other infrequent causes of tricuspid regurgitation include:

• Carcinoid tumors, which release a hormone which damages the valve
• Marfan syndrome
• Injury
• Rheumatoid arthritis
• Radiation therapy

Another important risk factor for tricuspid regurgitation is use of the diet medications called "Fen-Phen" (phentermine and fenfluramine) or dexfenfluramine.