The tricuspid valve separates the right ventricle and the right atrium. It normally consists of three leaflets (anterior, posterior and septal leaflet). The leaflets are attached to the subvalvular apparatus, consisting of the chordae tendineae and the papillary muscles. As compared to the mitral valve, the tricuspid valve is located slightly more apically (<0.8 mm / m2 BSA [body surface area]).
Approximately 85%-90% of healthy individuals in the general population exhibit a small tricuspid regurgitation, which is considered a normal finding. Pathological tricuspid regurgitation is more pronounced. Echocardiography is the preferred method for diagnosing tricuspid regurgitation.
Causes of tricuspid regurgitation
The most common causes of tricuspid regurgitation are as follows:
- Right ventricular dysfunction due to pressure/volume overload.
- Right ventricular infarction.
- Ebstein's anomaly (Figure 1).
- Carcinoid heart disease.
- Endocarditis (common in intravenous drug addicts).
- Myxomatous degeneration.
- Rheumatic heart disease.
- Dilatation of the right ventricle.
- Dilatation of the right atrium.
- Pulmonary hypertension.
- Left-to-right shunt.
Right ventricular dysfunction due to pressure/volume overload is the most common cause.
The prevalence of Ebstein's anomaly is approximately 1 case per 200.000 live births (Atthenhofer et al).
Ebstein's anomaly is characterized by the following malformations:
- The septal and posterior leaflets of the tricuspid valve adhere to the ventricular myocardium (failure of embryological delamination).
- The tricuspid valve annulus is displaced apically >0.8 mm/m2 BSA.
- Basal segments of the right ventricle (i.e parts on the atrial side of the tricuspid annulus) function as atrium and becomes dilated.
- The anterior leaflet is usually larger. It may be fenestrated and swing into the RVOT, obstructing the outflow.
Reumatic heart disease
- Thickened chordae tendineae.
- Thickened leaflet tips.
- Reduced leaflet mobility.
- Left-sided rheumatic valvular disease is virtually always present.
Carcinoid heart disease
- Short, thick and rigid leaflets.
Two-dimensional echocardiography is used to evaluate valve anatomy and the subvalvular apparatus. Thickness, mobility and coaptation of the leaflets are assessed visually in multiple views. It should be noted that imaging of the right ventricle requires an experienced echocardiographer. Three-dimensional (3D) echocardiography should be considered in laboratories with expertise; 3D imaging is superior to 2D for estimating right ventricular volumes. Cardiac MRI is, however, the gold standard for assessing right ventricular anatomy and function.
Right ventricular dimensions and function must always be assessed. Left ventricular function, which may be the origin of right ventricular dysfunction, must also be evaluated. The pulmonary, aortic and mitral valve must also be evaluated, particularly in the setting of rheumatic valvular disease.
The regurgitation is considered severe if the tricuspid annulus diameter is >4 cm. Severe tricuspid regurgitation results in right ventricular and atrial dilation.
Tricuspid regurgitation leads to pressure and volume overload in the right ventricle. This results in the septum bulging into the left ventricle, which gives the left ventricle a D-shaped appearance in short-axis views. The increased pressure may also propagate back to the right atrium and venous system, resulting in dilation of vena cava inferior (>2.1 cm). Severe tricuspid regurgitation may lead to systolic reversal in the hepatic veins. This is visualized using pulsed Doppler in the hepatic veins during systole.
The regurgitant jet area (in the right atrium) should be measured and compared to the area of the right atrium. If the jet area is ≥40% of the atrial area, then the regurgitation is severe.
Vena contracta should also be measured; ≥ 0.7 cm is indicative of severe regurgitation.
Continuous Doppler, placed in the tricuspid valve orifice, is used to investigate the appearance of the spectral curve. A dense spectral curve with an early peak indicates a rapid pressure equalization between the atrium and the ventricle.
PASP: Pulmonary Artery Systolic Pressure
PASP (pulmonary artery systolic pressure) is estimated by adding the pressure gradient between the atrium and the ventricle (estimated using continuous Doppler through the tricuspid valve) and the right atrial pressure (RAP), according to the following formula:
PASP = 4v2 + RAPmean
where 4v2 equals the pressure gradient between atrium and ventricle
Mean RAP is difficult to estimate if the regurgitation is pronounced.
Attenhofer et al. Ebstein's anomaly. Circulation (2007).