Tricuspid Valve Lesions: Tricuspid Stenosis
Introduction And Etiology
Normal tricuspid orifice is larger than the mitral orifice (7cm2 ). The tricuspid leaflets differ from the mitral leaflets in being thinner, more translucent and less clearly separated into well defined leaflets. The three major leaflets are anterior, septal and posterior. The tricuspid valve may be stenotic, regurgitant or both. Tricuspid stenosis is clinically detecteable in 3-5% ofcases with multivalvular involvement, but tricuspid lesion can be demonstrated in a much higher proportion (up to 30%) during autopsy.
- Rheumatic valvulitis
- Congenital tricuspid stenosis
- Carcinoid syndrome
- Endocardial fibroelastosis
- Endomyocardial fibrosis
- Systemic lupus erythematosus
Rheumatic valvulitis causes fusion of the adjacent free edgers of the leaflets. The valve cusps are also moderately thickened. The involvement of the subvalvular apparatus is less marked compared to the distortion in mitral stenosis. When the valve area falls below 1cm2 it leads to severe tricuspid stenosis. If the valve area is between 1 and 1.5cm2, it is designated as moderate stenosis. In tricuspid stenosis, the flow of blood from the right atrium to the right ventricle is hampered. This results in reduction in cardiac output and elevation of the right atrial pressure. Ultimately, this leads to systemic venous hypertension.
Rheumatic tricuspid stenosis is almost always associated with mitral stenosis. Presence of tricuspid stenosis leads to reduction in pulmonary venous congestion and therefore, the symptoms of mitral stenosis such as paroxysmal nocturnal dyspnea, pulmonary edema and hemoptysis are considerably less. The most common symptoms attributable to tricuspid stenosis are effort intolerance and easy fatigability produced as a result of the low cardiac output. Physical examination reveals small volume pulse. The jugular venous pulse shows elevation of mean pressure, prominent ‘a’-waves with slow ‘y’, descent. In the presence of atrial fibrillation, the characteristic ‘a’-wave is lost, but the slow ‘y’ descent persists. The left parasternal heave seen in mitral stenosis is usually absent. The characteristic auscultatory feature is the presence of a mid-diastolic or pre-systolic murmur which is best heard at the lower left sterna border. Though the murmur is also rumbling in character, its pitch is higher than the murmur of mitral stenosis. It increase in intensity with inspiration (Carvalio’s sign). The first sound is often split as a result of simultaneous delay in both its mitral and tricuspid components.
The ECG shows evidence of right atrial enlargement. Chest X-ray shows right atrial dilatation without significant enlargement of the pulmonary arteries. Echocardiography clearly demonstrates the lesion in the valves. Accurate delineation of the severity of tricuspid lesion is done by cardiac catheterization and angiography.
Course And Prognosis
Course and prognosis: Though the symptoms of pulmonary venous hypertension in patients with mitral stenosis are ameliorated by the coexistence of tricuspid stenosis, the cardiac output is considerably reduced and systemic venous hypertension develops. In such cases, if the tricuspid stenosis is left uncorrected during surgery by mistake, the desired benefit or mitral or aortic valve surgery may not be obtained.
Treatment: Moderate or severe tricuspid stenosis should be corrected by commissurectomy at the time of surgery for the mitral lesion.
© 2014 Funom Theophilus Makama