The most common cause of tricuspid regurgitation is not damage to the valve itself, but enlargement of the right ventricle, which 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. The valve fails to close properly, and blood can flow back to the right atrium from the right ventricle, and from there back into the veins. This reduces the flow of blood forward into the lungs. The condition affects about 4 out of 100,000 people. Another important risk factor for tricuspid regurgitation is use of the diet medications called "Phen- fen" (phentermine and fenfluramine) or dexfenfluramine. Rarely tricuspid regurgitation can be caused by an unusual tumor called carcinoid. This tumor secretes a hormone which damages the valve.
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