Very little is known about tricuspid valve when compared to other valvular disorders, and tricuspid stenosis (TS) is even more rarely described. It most often co-exists with mitral valve pathology especially in patients with rheumatic heart disease
Rheumatic heart disease is one of the most common causes of TS and almost always occurs in conjunction with mitral stenosis . Large vegetations in infective endocarditis can cause relative stenosis . Carcinoid syndrome may cause isolated TS or mixed with the regurgitant lesion . Systemic diseases like systemic lupus erythematosus (SLE), antiphospholipid antibody (APLA) syndrome and the presence of permanent pacing and fusion of implantable cardioverter defibrillator leads to sub-valvular structures can cause tricuspid stenosis. Benign tumors like atrial myxomas can cause functional TS . Blunt trauma has also been described as a risk factor. Renal and ovarian tumors can grow into the tricuspid orifice causing stenosis .
Other less common causes of TS include congenital abnormalities (Ebstein’s anomaly), metabolic or enzymatic abnormalities (Fabry’s disease, Whipple’s disease). Sometimes described are intravenous leiomyomatosis, ventriculoatrial shunts  causing TS. Valvulopathy associated with drugs like fenfluramine/phentermine and methysergide is characterized by thickened fibrotic and hypomobile tricuspid leaflets, with various degrees of valve stenosis and regurgitation.
The circumference of the normal tricuspid valve is 12 to 14 cm, and most pathologists consider a circumference of less than 10 to 11 cm (i.e., diameter less than 3 cm or valve area of less than 7 cm^2) as an indication of TS. Normal Area of the tricuspid valve is 4.0 cm2 and area less than 1.0 cm^2 is deemed as severe TS 
The rheumatic tricuspid disease is characterized by diffuse fibrous thickening of the leaflets and fusion of 2 or 3 commissures. Leaflet thickening usually occurs in the absence of calcific deposits, and the anteroseptal commissure is most commonly involved. Incompletely developed leaflets, shortened or malformed chordae, a small annulus, or an abnormal number or size of papillary muscles may result in TS.
The valves consist of an outer layer of valve endothelial cells (VECs) surrounding three layers of the extracellular matrix each with specialized function and interspersed with interstitial valve cells (VICs). Genetic or acquired/environmental causes that disrupt the normal organization and composition of the extracellular matrix and communication between VECs and VICs alter valve mechanics and interfere with the valve leaflet function, culminating in heart failure.
The primary result of TS is right atrial pressure elevation and consequent right-sided congestion.
Presenting symptoms are generally related to right-sided valve disease such as reduced exertional capacity, fatigue, or, exertional syncope. Patients with severe TS will eventually have hepatic congestion, leg edema, ascites, and deterioration of liver function tests and anasarca.
"Giant a waves" classically greater in height than usually perceived in the jugular venous pulse, are seen in TS. A "slow y descent" due to delayed emptying of the right atrium into the right ventricle can also be seen.
The lungs are clear in patients with isolated TS. A low frequency presystolic mid-diastolic murmur is heard at the lower left sternal border in the fourth intercostal space. The intensity of the murmur and opening snap in TS increase with maneuvers that increase blood flow across the tricuspid valve, especially with inspiration and also with leg raising, inhalation of amyl nitrate, squatting, or exercise.
Electrocardiogram: In patients with TS in sinus rhythm, the electrocardiogram may show tall, peaked P waves in leads II, III, and avF consistent with right atrial enlargement.
Echocardiography: Tricuspid peak inflow velocity during inspiration of > 1 m/s, Inflow time-velocity integral greater than 60 cm, valve area by the continuity of less than or equal to 1 cm^2 indicates hemodynamically significant TS.
The mean transvalvular pressure gradient derived using the Bernoulli equation is usually lower in tricuspid stenosis than in mitral stenosis, ranging between 2 and 10 mm Hg, and averaging around 5 mmHg. A mean gradient greater than or equal to 5 mm Hg at normal heart rate is considered indicative of clinically significant TS . Higher gradients may be seen with combined stenosis and regurgitation. A longer T 1/2 (pressure halftime by continuous wave Doppler) implies a greater TS severity with values of greater than or equal to 190 ms being frequently associated with significant (or critical) stenosis. Other parameters that are seen include- reduced TAPSE, dilated IVC, and increased right atrial size.
Cardiac Catheterization: In TS, there is a large right atrial "a" wave of 12 to 20 mm Hg and a diastolic, mean gradient of 4 to 8 mm Hg across the tricuspid valve. The mean gradient across the tricuspid valve is more significant in tricuspid stenosis because an end-diastolic gradient may be absent with significant obstruction. This is because of the lower filling pressures on the right side of the heart. Elevated RA pressure with a slow fall in early diastole and a diastolic pressure gradient across the tricuspid valve is characteristic of TS.
Cardiac MRI: Cardiac MRI is now the preferred method to evaluate RV size and function.
Loop diuretics may be useful to relieve systemic and hepatic congestion in patients with severe, symptomatic TS . Caution is advised since diuretics may decrease the preload further in patients who have low output state.
Not every TS needs invasive intervention. Treatment of SLE and APLA syndrome may reduce the “coating” over the valves and chordae and reduce stenosis and regurgitation. Cessation of fenfluramine or methysergide has been associated with valve normalization. Less often, surgical therapy may be needed in addition to medical management.
A decision should be made to treat the patient with a valvotomy or valve surgery.
Valvotomy: Valvotomy is performed using 1, 2, or 3 balloons. While some stenosis may persist, the change in valve area causes a significant reduction in the transvalvular pressure gradient and a decrease in right atrial pressure.
Valve surgery: Tricuspid valve surgery includes repair vs. replacement. Repair should be attempted when reasonable. When repair is not an option, valve replacement can be done by open versus transcatheter replacement. While replacing the valve, no differences in outcomes have been established between bioprosthetic vs. mechanical valves. However, in carcinoid syndrome, a mechanical valve is preferred over bioprosthetic to avoid degeneration.
Surgery for severe TS is most often performed at the time of operation for left-sided valve disease, chiefly rheumatic mitral stenosis/mitral replacement. Tricuspid valve surgery is preferred over percutaneous balloon tricuspid commissurotomy for treatment of symptomatic severe TS because most cases of severe TS are accompanied with tricuspid regurgitation (TR) (rheumatic, carcinoid), and percutaneous balloon tricuspid commissurotomy may either create or worsen regurgitation.
Isolated, symptomatic severe TS without accompanying TR is an extremely rare condition for which percutaneous balloon tricuspid commissurotomy might be considered. Valve areas generally increase from less than 1 to almost 2 cm. It is also an option for patients considered to be at high surgical risk. Percutaneous balloon valvuloplasty may be done in non-surgical cases.
There is very limited information comparing percutaneous balloon valvotomy with tricuspid valve surgery.
Bioprosthetic valve stenosis can be treated with balloon valvotomy or valve-in-valve replacement.
TS staging sections into categories A, B, C, D. Stages C (without symptoms) and D (with symptoms). When valve and/or chordal thickening and calcification are evident, there are additional findings indicative of severe TS, for example, pressure gradient greater than or equal to 5 mm Hg, pressure half-time greater than or equal to 190 milliseconds, valve area less than or equal to 1.0 cm^2, associated moderate right atrial enlargement, and inferior vena cava dilatation.
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