Abstract
Echocardiography plays a unique role in the assessment of tricuspid and pulmonic valve disease. Although the tricuspid and pulmonic valves are structurally similar to the mitral and aortic valves, they rarely undergo the chronic degenerative changes that affect their left-sided counterparts. Newer and less invasive therapeutic options for treating tricuspid and pulmonic valve disease, including percutaneous valve replacement, balloon valvuloplasty, valve-in-valve replacement procedures, and, in the near future, percutaneous right-sided valve repair procedures, have increased the demand for more accurate and precise echocardiographic assessment of tricuspid and pulmonic valve disease. Three-dimensional (3D) echocardiography with concomitant 3D printing of the tricuspid and pulmonic valves, in particular, shows great promise in advancing the field of diagnostic and therapeutic options for treating right-sided valve disease, which should grow as the population ages.
Keywords
acquired abnormality, anatomy, congenital abnormality, pulmonic valve, tricuspid valve, 2D echo, 3D echo
Introduction
Echocardiography plays a unique role in the assessment of the tricuspid and pulmonic valves. However, their evaluation is often suboptimal because typical imaging protocols may overlook the views that best display pulmonic and tricuspid anatomy and function. Recent advances in percutaneous valve procedures for pulmonic and tricuspid disease have created a demand for detailed images and precise echocardiographic measurements of both the tricuspid and pulmonic valves. At the same time, advances in three-dimensional (3D) echocardiography have expanded the tools that are available.
Although the tricuspid and pulmonic valves are structurally similar to the mitral and aortic valves, they rarely undergo the chronic degenerative changes that affect their left-sided counterparts. Moreover, they are less likely to be affected directly by acquired diseases, such as rheumatic disease, endocarditis, and other inflammatory processes. This is generally attributed to the relative protection afforded by the lower right-sided pressures. Congenital abnormalities, such as Ebstein anomaly and pulmonary stenosis, are often encountered in the adult, and when the accompanying physiologic disturbance is mild, these conditions may have gone undetected in childhood. The most common form of tricuspid dysfunction is functional (i.e., when leaflet architecture is normal, but right ventricular [RV] dysfunction and remodeling prevent normal valve closure). This condition accounts for most surgical procedures performed on the tricuspid valve. RV abnormalities may be primary or secondary to pulmonary hypertension and/or left-sided abnormalities. Functional tricuspid regurgitation may also occur due to annular dilatation without ventricular abnormalities, such as that which may occur with atrial fibrillation. Myxomatous disease of the tricuspid valve and tricuspid valve prolapse may be seen in association with mitral valve myxomatous disease and prolapse, although the diagnostic criteria for tricuspid prolapse have not been clearly established. Spontaneous tricuspid flail is virtually unheard of. Although tricuspid valve endocarditis is often seen in patients with a history of intravenous drug abuse, pulmonic valve endocarditis occurs rarely, although it is possible that it is underreported. This chapter will review the echocardiographic features of these and other disorders that most commonly affect the tricuspid and pulmonic valves, and illustrate the two-dimensional (2D) and 3D echocardiographic views that can be used to image these valves most effectively. The reader is also referred to Chapter 40 for additional discussion of right-sided endocarditis.
Normal Tricuspid Valve Anatomy
The tricuspid valve is anatomically complex, with anterior, posterior, and septal leaflets extending from the tricuspid annulus to chords and papillary muscles. The tricuspid valve annulus is normally larger than that of the mitral valve, and it is more apically positioned. The anterior leaflet is largest, with an attachment that extends from the infundibulum to the inferoposterior wall of the right ventricle. The posterior leaflet is the smallest, extending along the diaphragmatic surface of the right ventricle, and the septal leaflet attaches to the muscular and membranous interventricular septum with an irregular array of chordae. The papillary muscles that attach the RV myocardium to the tricuspid valve leaflets are variable in number, size, and position ( Fig. 30.1 ).
Two-Dimensional Echo Views for Assessing the Tricuspid Valve
The standard 2D echocardiographic views for imaging the tricuspid valve are shown in Fig. 30.2A–E and 
and in composite Fig. 30.3 . The initial view recorded is typically the RV inflow tract. When obtained properly, this view displays the diaphragmatic and anterior walls of the RV, and the anterior and posterior leaflets of the tricuspid valve. This is a key view for visualizing the posterior leaflet. A nonstandard but common variant of this view is recognizable by the visualization of the interventricular septum and adjacent left ventricle (LV) cavity. This view displays the anterior and septal leaflets. In the apical four-chamber view, the anterior and septal leaflets of the tricuspid valve are typically visualized. A similar view may be obtained from the transthoracic subcostal four-chamber window and from the midesophageal four-chamber transesophageal view. The subcostal short-axis view at the level of the great vessels displays the anterior and septal leaflets. A similar view may be obtained from the parasternal short-axis view. The short-axis transesophageal echocardiographic transgastric view allows visualization of all three tricuspid leaflets simultaneously. In some patients, it may be possible to obtain a comparable view using the parasternal short-axis view, particularly if the RV is dilated.
While these descriptions apply to the standard application of these views, slight changes in transducer angulation may bring different leaflets into view, as has been elucidated with 3D-derived 2D imaging. Thus, when the transducer is angulated posteriorly from the standard four-chamber view, the posterior rather than the anterior leaflet can be seen opposing the septal leaflet, and, in the parasternal short-axis view, superior and inferior angulation permits imaging of all three leaflets.
Three-Dimensional Echo of the Tricuspid Valve
To acquire optimal transthoracic 3D echo images of the tricuspid valve, images are best obtained from the apical four-chamber view and/or the parasternal RV inflow view, with and without color ( Fig. 30.4 and 
). The protocol for acquiring transesophageal echo images of the tricuspid valve involves 0- to 30-degree midesophageal four-chamber zoomed acquisitions both with and without color, as well as 40-degree transgastric views with ante-flexion with and without color. A 3D echo of the tricuspid valve has demonstrated that the tricuspid valve is saddle shaped, becoming more planar and circular with functional tricuspid insufficiency.
. TV , Tricuspid valve. Abnormalities of the Tricuspid Valve
Carcinoid Valve Disease
The typical echocardiographic features of carcinoid heart disease ( Fig. 30.5A–D and 
) include tricuspid leaflets that are thickened, retracted, and immobilized, creating a large regurgitant orifice and the classic “drum stick” appearance. As a result, there is unrestricted tricuspid regurgitation, and the color Doppler regurgitant jet may appear relatively monochromic. Under these conditions, the regurgitant jet could be laminar and of relatively low velocity because of the almost complete equalization of pressures between the right atrium and right ventricle. This can lead to underestimation of the severity of tricuspid regurgitation. Similarly, estimation of pulmonary artery (PA) systolic pressure from the tricuspid regurgitation jet velocity will be inaccurate in this situation. A 3D transesophageal echo of the tricuspid valve allows high resolution and detailed visualization of the three thickened and retracted tricuspid leaflets from the right atrial or surgeon’s perspective (see Fig. 30.5D , right panel ). The valvopathy of carcinoid disease occurs when both serotonin and its metabolite 5-hydroxytryptophan are secreted by the carcinoid tumor causing an inflammatory reaction in the valves. Because the active metabolite is inactivated in the lungs, left-sided involvement occurs only when there is an intracardiac shunt or pulmonary metastases. Carcinoid heart disease is discussed in greater detail in Chapter 41 , and additional images are provided there.
Rheumatic Valve Disease
Rheumatic tricuspid involvement occurs in approximately 11% of patients with rheumatic mitral valve disease. A pathognomonic echocardiographic finding in rheumatic tricuspid valve disease is diastolic leaflet doming, which is best visualized in the apical four-chamber transthoracic echocardiography (TTE) and midesophageal four-chamber transesophageal echocardiography (TEE) views ( Fig. 30.6A–C and 
). This occurs because the belly of the leaflet may remain mobile as the tip is restricted. Rheumatic tricuspid disease is generally accompanied by rheumatic mitral disease. It may be distinguished from carcinoid disease (where mitral involvement is rare) by the presence of commissural fusion and chordal thickening, whereas carcinoid is primarily a disease of the leaflets. In diastole, color flow Doppler may demonstrate proximal flow convergence, which is a marker of stenosis. Spectral Doppler in the four-chamber views can be used to derive transvalvular tricuspid gradients. In general, the severity of tricuspid stenosis is best assessed by Doppler-derived mean gradients, noting that normal mean tricuspid gradients are under 3 mm Hg. Methods for calculating valve area, including the pressure half-time method, have not been validated for tricuspid stenosis. Mixed involvement with stenosis and regurgitation may occur.
Tricuspid Valve Endocarditis
Tricuspid endocarditis is typically a disease of intravenous drug abusers or the immunocompromised, although it may also occur due to contiguous spread from an aortic root abscess. In approximately 50% of primary cases, the causative organism is Staphylococcus aureus . S. aureus endocarditis may be very aggressive, significantly destroying valves within hours, and causing septic emboli to the lungs if not appropriately treated. Thus the echocardiographic appearance of valves affected by this organism can change quickly. Although TTE is often sufficient to establish the diagnosis of endocarditis in these cases, TEE offers incremental value in diagnosing disruption of the tricuspid leaflets and chordal structures, and in diagnosing annular abscess. Fig. 30.7 and 
demonstrate a large irregular vegetation attached to the anterior leaflet of the tricuspid valve. In this case, the chordal attachments have been disrupted, and there is severe tricuspid insufficiency.
