Tricuspid regurgitation (insufficiency) is the failure of the tricuspid valve to close properly during systole, leading to the leaking of blood from the right ventricle into the right atrium .
Causes and morphological features in 2-D Echocardiography
The standard echocardiographic views for tricuspid valve evaluation are:
- Apical four-chamber view
- Parasternal right ventricular inflow view
- Parasternal short-axis view at the great vessel level
- Subcostal four-chamber view
Tricuspid regurgitation (TR) is a common echocardiographic finding.
Trivial tricuspid regurgitation can be seen found during echocardiographic exam in 65-75% of normal individuals. It is a small central jet <1cm, in the first part of the systole, with peak velocity less than 2.3 m/s, normal valve leaflets and right ventricle. It has no pathological significance, but facilitates pulmonary artery systolic pressure evaluation.
Tricuspid regurgitation (TR) can be organic („primary”) or functional („secondary”) due to tricuspid annulus /right ventricular dilatation. Functional TR is more common.
Rheumatic tricuspid regurgitation
In rheumatic tricuspid regurgitation, there is thickening, shortening and retraction of the leaflets and subvalvular apparatus. Leaflet thickening and restrictive movement are visible in 2D echo. There is usually co-existent rheumatic involvement of left heart valves.
Degenerative tricuspid regurgitation
Degenerative tricuspid regurgitation include the billowing valve, prolapsing valve and flail tricuspid valve. Tricuspid prolapse alone is rare and it is ussually associated with mitral valve myxomatous disease. Flail tricuspid valve due to ruptured chordae can be the consequence of endocarditis, trauma, or spontaneous rupture.
Carcinoid tricuspid regurgitation
Carcinoid involvement of the tricuspid valve is characterized by thickening of the leaflet on the entire length, rigid appearance and motion restriction. Pulmonary hypertension is usually not present and tricupid regurgitant jet has low velocity.
Other organic causes of tricuspid regurgitation are:
- right-heart endocarditis
- Ebstein anomaly,
- endocardial fibroelastosis
- anorexigen medication
- radiation therapy
- trauma (including repeated endomyocardial biopsies)
- pacing and ICD leads.
Functional tricuspid regurgitation
Functional TR is the result of tricuspid annulus dilatation, caused by right ventricular adverse remodeling in pulmonary hypertension of any cause. The echographic appearance of the leaflets is normal. Tethering of the leaflets and papillary muscle displacement is frequently present. Evaluation of the tethering may be performed by measuring systolic tenting area in apical four-chamber view. Tenting area >1cm2 is associated with severe TR.
Normal tricuspid annulus diameter is 28±5 mm in apical four chamber view. A diastolic diameter > 35mm (> 21mm/m2) defines significant tricuspid annulus diameter dilatation.
Assessment of severity
Colour flow Doppler
Colour flow imaging
- Colour flow imaging is first step in TR diagnosis by visualization of retrograde systolic flow from right ventricle to right atrium
- It is useful for rapid estimation of TR severity. The principle is that the larger the jet, the more significant TR is. During the years TR severity was assessed according to the regurgitant jet area with mild TR area < 5 cm2, moderate TR 5-10 cm2 and severe >10 cm2  or based on jet area over right atrium area. These methods of TR quantification are influenced by hemodynamic (right atrial pressure, volemia) and technical factors (gain) and underestimate the severity of eccentrical jets, therefore they are no longer recommended as sole methods for TR severity grading. Except for small jets, further semiquantitative or quantitative evaluation are recommended for TR grading by the EAE recommendations for the assessment of valvular regurgitation.
- TR jet should be visualised in at least two different echocardiographic views
- Elements to be assessed by colour flow imaging:
- Jet dimension and direction
- Jet base width at the valve level
- Intra atrial jet area if it is a central jet
- Vena contracta width is a semicantitative method for TR severity estimation
- It is the narrowest region of regurgitant jet (usually just below the valve in right atrium)
- Vena contracta is measured in apical four chamber view, after color Doppler flow optimization. The three components of the regurgitant jet (proximal convergence area, vena contracta and regurgitant jet in the right atrium) should be clearly individualized.
- Vena contracta width ≥ 7 mm has a 90% sensitivity and 93-95% specificity for severe TR
- Vena contracta width < 6 mm is an argument for mild or moderate TR, but no clear cut-off between mild and moderate TR has been proposed
PISA (Proximal isovelocity surface area)
- The radius of proximal isovelocity surface area or flow convergence zone can be used to calculate the severity of tricuspid regurgitation.
- It provides a quantitative assessment of TR severity, but it is seldom used in clinical settings 
- PISA radius is usually measured in apical four chamber view, parasternal long or short axis view in midsystole using the first aliasing
- PISA radius > 9 mm at a Nyquist limit of 28 cm/s suggests significant TR, while a radius < 5 mm supports the diagnosis of mild TR 
- Effective regurgitant orifice area (EROA) ≥ 40 mm2 and regurgitant volume ≥ 45 ml characterize severe TR
Continuous wave Doppler (CW)
- Continuous wave Doppler interogation should be performed in views where parallel alignment with the regurgitant jet is possible and should be color Doppler-guided
- Allows a qualitative estimation of TR severity based on shape and density of the signal. The denser the envelope compared to the forward flow, the more severe the TR is.
- Allows a qualitative estimation of TR severity based on the shape of Doppler envelope. In severe TR a rapid equalization of right atrial and right ventricular pressure appears and the envelope is triangular, with an early systolic peak.
- Allows estimation of pulmonary artery systolic pressure based on Bernoulli equation (P=4v2 + right atrial pressure, where v is maximal systolic velocity of the regurgitant jet)
- There is no relationship between maximal jet velocity and tricuspid regurgitation severity. Massive TR are usually associated with reduced velocities, < 2m/s, due to small pressure differences between right atrium and ventricle 
- May provide indirect information on right ventricular function based on dp/dt measurement. Values < 400mmHg/s suggest right ventricular systolic dysfunction
Pulsed wave Doppler(PW)
- Pulsed wave Doppler examination is performed in apical four-chamber view
- Similar with mitral regurgitation, a severe regurgitation will increase the protodiastolic flow 
- An E wave more than 1m/s is an indirect marker of severe TR2
- Pulsed wave Doppler is also useful for the assessment of hepatic venous flow
- In subcostal view the Doppler sample is placed in the right superior hepatic vein 1-2 cm proximal to the junction with the inferior vena cava
- systolic flow in the hepatic vein is directed towards the right atrium and is registered as a negative component on PW Doppler curve
- systolic flow reversal in the hepatic vein is a specific marker of severe TR; its sensitivity is 80%.
Consequences of tricuspid regurgitation
- severe chronic TR is associated with right ventricular, right atrial, inferior vena cava dilatation.While these changes can be seen in other circumstences, right heart dilatation is an important supportive sign for significant chronic tricuspid regurgitation
- Normal RV/RA/inferior vena cava size can virtually exclude significant chronic TR.4 However, they may be normal in acute significant TR
- Paradoxical ventricular septal motion can occur due to right ventricular volume overload, but it is not a specific sign for significant TR.
|Parameters of severe tricuspid regurgitation|
|Jet area||>10 cm2 or ≥30% of right atrial area|
|PISA radius||>9 mm|
|Hepatic venous flow||systolic flow reversal|
|Continuous wave Doppler||Triangular dense envelope with early systolic peak|
|Right ventricle and right atrium||Right ventricle and right atrium dilatation|
- ↑ 1.0 1.1 Anwar AM, ten Cate FJ. Tricuspid and pulmonary valve. In Galiuto L, Badano L, Fox K, Sicari R, Zamorano JL. The EAE Textbook of Echocardiography. 1st edition. Oxford, Oxford University Press. 2011; 255-264.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Lancellotti P, Moura L, Pierard LA, et al. European Association of Echocardiography recommendations for the assessment of valvular regurgitation. Part 2: mitral and tricuspid regurgitation (native valve disease). Eur J Echocardiogr 2010;11:307-332.
- ↑ 3.0 3.1 Feigenbaum H, Armstrong WF, Ryan T. Tricuspid valve. In: Feigenbaum H, Armstrong WF, Ryan T. Feigenbaum’s Echocardiography. 6th ed. Lippincott Williams&Wilkins. 2005;364-369.
- ↑ 4.0 4.1 Zoghbi WA, Enriques-Sarano M, Foster E, et al. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and doppler echocardiography. J Am Soc Echocardiogr. 2003;16:777-802.
- ↑ Tribouilloy C, Enriquez-Sarano M, Bailey KR, et al. Quantification of tricuspid regurgitation by measuring the width of the vena contracta with Doppler color flow imaging: a clinical study. J Am Soc Echocardiogr. 2000;36:472-478.
- ↑ Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the Echocardiographic Assessment of the Right Heart in Adults: A report from the American Society of Echocardiography. J Am Soc Echocardiogr. 2010;23:685-713.
- ↑ Danicek V, Sagie A, Vaturi M. Relation of tricuspid inflow E-wave peak velocity to severity of tricuspid regurgitation. Am J Cardiol 2006;98:399-401.
- ↑ Gonzalez-Vilchez F, Zarauza J, Vazquez de Prada JA, et al. Assessment of tricuspid regurgitation by Doppler color flow imaging: angiographic correlation. Int J Cardiol. 1994 ;44:275-83.