INTRODUCTION	Section 2 of 11
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Background: Tricuspid valve dysfunction can result from morphological alterations in the valve or from functional aberrations of the myocardium. Tricuspid stenosis is almost always rheumatic in origin and is generally accompanied by mitral stenosis.

Most stenotic tricuspid valves are associated with clinical evidence of regurgitation that can be documented by performing a physical examination (murmur), echocardiography, or angiography. Stenotic tricuspid valves are always anatomically abnormal, and the cause is limited to a few conditions. With the exceptions of congenital causes or active infective endocarditis, tricuspid stenosis takes years to develop.

Pathophysiology: Tricuspid stenosis results from alterations in the structure of the tricuspid valve that precipitate inadequate excursion of the valve leaflets. The most common etiology is rheumatic fever, and tricuspid valve involvement occurs universally with mitral and aortic valve involvement. In this case, the valve leaflets become thickened and sclerotic as the chordae tendineae become shortened. This restrictive process hampers blood flow into the right ventricle and, subsequently, to the pulmonary vasculature. The obstructed venous return results in hepatic enlargement, decreased pulmonary blood flow, and peripheral edema. Right atrial enlargement is observed as a consequence. Other rare causes include carcinoid syndrome, endocarditis, endomyocardial fibrosis, lupus, and congenital tricuspid atresia.

In the rare instances of congenital tricuspid stenosis, the valve leaflets may manifest various forms of deformity, which can include deformed leaflets, deformed chordae, and displacement of the entire valve apparatus. In the congenital form of the disease, other cardiac anomalies are usually present.

Frequency:

• In the US: Tricuspid stenosis is rare, occurring in less than 1% of the population. While found in approximately 15% of patients with rheumatic heart disease at autopsy, it is estimated to be clinically significant in only 5% of these patients. The incidence of the congenital form of the disease is less than 1%.

• Internationally: Tricuspid stenosis is found in approximately 3% of the international population. It is more prevalent in areas with a high incidence of rheumatic fever. The congenital form of the disease is rare and true incidence is not available.

Mortality/Morbidity: The mortality associated with tricuspid stenosis depends on the precipitating cause. The general mortality rate is approximately 5%.

Race: No racial predisposition is apparent.

Sex: Tricuspid stenosis is observed more commonly in women than in men, similar to mitral stenosis of rheumatic origin. The congenital form of the disease has a slightly higher male predominance.

Age: Tricuspid stenosis can present as a congenital lesion or later in life, precipitated by some other condition. The congenital frequency rate of the lesion is approximately 0.3% of all congenital heart disease cases. The frequency rate in the older population, due to secondary causes, ranges from 0.3-3.2%.

	CLINICAL	Section 3 of 11
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History: Fatigue, due to limited cardiac output through the stenosis, may be present. Systemic venous congestion leads to abdominal complaints of discomfort and swelling. Onset is usually gradual, but it can be rapidly increased by the development of atrial fibrillation or flutter. Dyspnea may be present, but it is not severe except with concomitant mitral disease. Patients may complain about prominent pulsations in the neck.

• When tricuspid stenosis becomes significant in the presence of mitral stenosis, the decrement of cardiac output to the pulmonary bed may paradoxically diminish dyspnea, hemoptysis, and orthopnea.

• Obtain information regarding streptococcal infections, symptoms of the carcinoid syndrome, and possible congenital abnormalities.

Physical: With sinus rhythm (more common with tricuspid stenosis than with mitral stenosis), the jugular venous pulse increases and the a wave is prominent (may be confused with arterial pulse). If atrial fibrillation occurs, the a wave is lost. Peripheral edema and ascites are frequent. Without significant mitral pathology, the patient should not be dyspneic and can probably lie flat.

• A prominent right atrium may be palpable to the right of the sternum. If not obscured by mitral stenosis sounds, a tricuspid opening snap may be heard. A diastolic murmur along the left sternal border or at the xiphoid will increase with inspiration. Often, tricuspid regurgitation is also present, represented by a systolic murmur in a similar location.

• The first heart sound may be split widely. The second heart sound may be single. This single sound is due to the inaudible closure of the pulmonary valve from the decrease in blood flow through the stenotic tricuspid valve.

Causes: At least 4 conditions can cause obstruction of the native tricuspid valve. These include (1) rheumatic heart disease, (2) congenital abnormalities, (3) metabolic or enzymatic abnormalities, and (4) active infective endocarditis.

• Rheumatic tricuspid stenosis: In this entity, diffuse and fibrous thickening of the leaflets occurs, with fusion of 2 and usually 3 commissures. The chordae tendineae may be thickened and shortened. Calcification of the valve rarely occurs. The leaflet tissue is composed of dense collagen and elastic fibers that produce a major distortion of the normal leaflet layers.

• Carcinoid heart disease: Carcinoid valve lesions characteristically manifest as fibrous white plaques located on the valvular and mural endocardium. The valve leaflets are thickened, rigid, and reduced in area. Fibrous tissue proliferation is present on the atrial and ventricular surfaces of the valve structure.

• Congenital tricuspid stenosis: These lesions are observed more commonly in infants. They may manifest as incompletely developed leaflets, shortened or malformed chordae, small annuli, abnormal size and number of the papillary muscles, or any combination of these defects.

• Infective endocarditis: Large infected vegetations obstructing the orifice of the tricuspid valve may produce stenosis. This condition is relatively uncommon, even in those who abuse intravenous drugs.

• Unusual causes: Rare causes of tricuspid stenosis include Fabry disease and giant blood cysts.

• Mimickers of tricuspid stenosis: Several conditions may mimic tricuspid stenosis by obstructing flow through the valve, including supravalvular obstruction from congenital diaphragms, intracardiac or extracardiac tumors, thrombosis or emboli, or large endocarditis vegetations. In addition, conditions that impair right-sided filling can reproduce historical and physical findings such as constrictive pericarditis and restrictive cardiomyopathy.