Right-Sided Valve Disease in Adults

Background

TR affects 80% of the population. Moderate-severe or worse TR affects approximately 1.6 million Americans. ^, As shown in Table 28.2 , TR has many causes. Primary TR due to leaflet abnormalities occurs in approximately 10% of patients with TR and is most commonly caused by congenital heart disease, carcinoid syndrome, rheumatic valve disease, infective endocarditis, toxic drug exposure, or flail leaflet after blunt chest trauma.

A growing patient population has primary isolated TR due to endomyocardial biopsy or intracardiac device leads. ^, The true incidence of TR after endomyocardial biopsy is unknown, but moderate or worse TR has been reported for 14% to 33% of orthotopic heart transplant patients undergoing repeated biopsies over long-term follow-up. ^, Device leads are an underappreciated cause of primary isolated TR. In a series of 239 patients undergoing de novo ventricular lead implantation, 38% developed new TR of 2+ or greater.

Ninety percent of severe TR cases are secondary (i.e., functional), meaning that the TR is mediated by RV and/or RA enlargement. The most common cause of secondary TR is pulmonary hypertension (PH) resulting from intrinsic pulmonary vascular disease or elevation of the pulmonary artery wedge pressure due to left-sided heart disease. Over time, chronic pressure overload causes the RV to dilate, resulting in papillary muscle displacement and lateral annular dilation with resultant leaflet malcoaptation ( Fig. 28.2 ). As the annulus dilates, the TV loses its normal tipped-down elliptical shape and assumes a planar orientation with a circular orifice. ^, Recirculation of the regurgitant volume (RVol) creates chronic RV volume overload, causing the RV to further dilate and creating a cycle in which severe TR begets more severe TR.

An emerging population of adult patients has isolated TR in the absence of left-sided heart disease, PH, or congenital abnormalities. Most cases of isolated TR result from direct leaflet displacement or damage from RV pacemaker or defibrillator leads or from TV annular dilation due to RA enlargement caused by long-standing atrial fibrillation. ^, Isolated TR is associated with a poor long-term prognosis, even in the absence of other cardiopulmonary comorbities. ^,

Basic Echocardiographic Imaging Principles

The symptoms and physical examination findings of TR can be nonspecific, and as a result, most cases of TR are diagnosed during echocardiography. When more than mild TR is appreciated on transthoracic echocardiography (TTE), a more thorough assessment of the mechanism and severity of TR is mandatory. Defining the mechanism and severity of TR is essential for determining the appropriate treatment. Patients with primary or isolated TR may benefit from surgical correction, whereas many patients with secondary TR are best served by treating the predisposing disease process ( Table 28.3 ).

Assessing the Mechanism and Severity of Tricuspid Regurgitation

A comprehensive TTE assessment of the TV should be performed in all patients with more than mild TR. TTE has several goals:

• 1.

  Define the mechanism of TR

• 2.

  Quantify the severity of regurgitation

• 3.

  Screen for PH and left-sided heart disease

• 4.

  Assess RV size and function

Echocardiographic assessment of the TV involves a systematic and stepwise interrogation of the TV from four main views; the parasternal short- and long-axis views, the apical 4-chamber view, and the subcostal windows. The RV inflow view from the parasternal long axis ( Fig. 28.3A ) allows visualization of the RA and the base of the RV. Rotating the probe 90 degrees brings in the parasternal short-axis view at the level of the aortic valve (see Fig. 28.3B ), from which the RA, RV outflow tract (RVOT), TV, and PV can be viewed.

The apical 4-chamber view is best for visualization of the RV (see Fig. 28.3C ) and is the view from which quantitative measurements of RV size and strain are performed. When functional TR due to significant aortic or mitral valve disease is suspected, the TV annular diameter should be measured from the apical 4-chamber view (see Fig. 28.3D ). A diastolic diameter of more than 4 cm (or diameter indexed to body surface area of ≥ 21 mm/m ² ) indicates an increased risk for persistent TR after mitral valve surgery if concomitant TV repair is not performed. ^{, ,}

From the parasternal short-axis and apical 4-chamber views, it is possible to visualize the septal and anterior leaflets. The posterior leaflet is best viewed from the apical 4-chamber or subcostal windows by sweeping the probe posteriorly until the coronary sinus is brought into view. However, even with these techniques, correct identification of the individual leaflets is challenging because of anatomic variation. Although it is sometimes forgotten, a short-axis view of the TV on the parasternal short axis should always be attempted because, similar to 3D echocardiography, it provides simultaneous assessment of all three RV leaflets (see Fig. 28.1B ). This can be obtained by tilting the probe inferiorly from the level of the mitral valve; with practice, it can be obtained in a large proportion of patients.

3D echocardiography provides superior visualization of the TV leaflets ( Fig. 28.4 ) by overcoming the challenges of imaging the nonplanar TV annulus. Optimal 3D imaging should include the surrounding anatomic landmarks in the acquisition volume to aid in recognition of the individual leaflets and to define the mechanism of TR. 3D echocardiography is the most accurate method of localizing focal anatomic disease such as infective endocarditis, intracardiac device lead impingement, or flail leaflet. Transthoracic 3D volumes can be obtained in the parasternal, apical, or subcostal window, but the apical window is typically best because of the anterior location of the RV near the chest wall and the perpendicular orientation of the TV relative to the ultrasound probe. Parasternal short- or long-axis views may also provide high-quality 3D images, and they allow improved spatial resolution because the TV lies in the parasternal near field.

Anatomic assessment of the leaflets is essential for identifying the cause of TR ( Fig. 28.5 ) and referring patients for appropriate therapy. Flail leaflet may result from myxomatous degeneration, infective endocarditis, blunt chest trauma, cardiac lead device extraction, or endomyocardial biopsy. Infective endocarditis may also result in leaflet perforation or leaflet destruction, or a large vegetation may interrupt coaptation. Rheumatic heart disease commonly causes combined regurgitation and stenosis due to commissural fusion with shortening and retraction of the leaflets and chordae. Carcinoid syndrome and serotonergic or dopaminergic drugs induce fibroproliferative leaflet thickening and reduce leaflet mobility ( Fig. 28.6 ).

Ebstein anomaly is characterized by in utero failure of leaflet delamination, with subsequent apical displacement of the septal and posterior leaflets into the ventricle ( Fig. 28.7 ). When a congenital cause such as Ebstein anomaly is identified, it is important to screen for associated cardiac defects such as patent foramen ovale, atrial septal defect, and LV noncompaction.

Intracardiac devices can induce TR through leaflet impingement, perforation, or adhesions; however, 2D TTE may be insensitive for lead-induced TR. In a series of 41 patients with surgically confirmed lead-induced TR, only 12% of patients were accurately identified by TTE preoperatively. The use of 3D echocardiography and TEE imaging may substantially improve accurate detection of lead-mediated TR.

When TTE does not reveal a primary anatomic cause of TR, it is necessary to screen for predisposing disease processes such as left-to-right shunt, PH, and left-sided heart disease. Echocardiographic assessment of these disease processes is covered in depth in other chapters.

In approximately 10% of patients with secondary TR, a predisposing cause cannot be identified. ^{, ,} These patients tend to be elderly and female and have a high prevalence of atrial fibrillation. ^{, ,} Echocardiographic assessment of isolated TR in patients with atrial fibrillation and no other cardiopulmonary comorbidities has identified a unique pattern of RA enlargement and annular dilation out of proportion to RV enlargement, suggesting that atrial fibrillation may be a cause rather than a consequence of TR.