Tricuspid and Pulmonary Valvular Disease

Published on 24/02/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 1621 times

CHAPTER 61 Tricuspid and Pulmonary Valvular Disease

The right heart functions to receive systemic deoxygenated blood in the atrial chamber and pump it via the ventricular chamber into the pulmonary arterial system for gas exchange. This process is well coordinated. Although the electrical conduction pathways and muscular contraction are fundamental to achieving continuous blood flow through the right heart, equally important are the tricuspid and pulmonary valves that regulate flow between the right atrium and ventricle and right ventricle and pulmonary artery, respectively. These valves ensure appropriate antegrade flow during the cardiac cycle.

The tricuspid and pulmonary valves can fail as a result of disease states, which may lead to stenosis (Figs. 61-1 to 61-3), insufficiency (Figs. 61-4 to 61-6), or a combination of both (Figs. 61-7 to 61-9). Stenosis impedes forward flow, resulting in pressure overload, and insufficiency results in blood flowing backward, leading to volume overload. Tricuspid and pulmonary valvular disease may present in isolation or in conjunction. Clinical presentation, involvement of the cardiac chambers, severity of secondary chamber dysfunction, and impact on systemic and pulmonary vasculature and other viscera depend on which valves are involved, which type of valvular dysfunction predominates, the severity and duration of valvular dysfunction, and the degree of cardiac compensation. Pharmacologic, endovascular, and surgical management for diseased valves relies on accurate and comprehensive noninvasive diagnostic evaluation, using a combination of chest radiography, echocardiography, magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and computed tomography angiography (CTA). Invasive catheterization is no longer used to diagnose primarily tricuspid and pulmonary valvular disease and should be reserved for cases in which flow dynamics require direct assessment. Noninvasive modalities also form the basis for surveillance imaging.

FIGURE 61-1 Tricuspid atresia; 30-year-old patient with tricuspid atresia, now status postcompletion Fontan A, Four-chamber CTA projection shows a continuous atrioventricular groove (arrowheads) with absent communication between the right atrium (RA) and right ventricle (RV). Note the single-ventricle physiology with a single atrial chamber formed by the RA and left atrium (LA) and wide communication between the RV and left ventricle (LV) across a ventricular septal defect (VSD; bulboventricular foramen). B-D, Fontan pathway demonstrates dominant superior vena cava flow (arrow) into the right pulmonary artery (RPA). E, The extracardiac Fontan conduit (FTN) provides preferential flow into the neo- and native left pulmonary artery (LPA).

FIGURE 61-2 Pulmonary atresia. A, Three-dimensional MRA volume rendering (VR) depicts an atretic pulmonary valve (arrowheads). Native pulmonary arteries (short arrows) receive blood flow, reconstituted from a dominant single major arterial pulmonary collateral artery (B, long arrow) off the proximal descending aorta, which then feeds a mediastinal collateral network (A, long arrow) . Blood flows retrograde into the central branch pulmonary arteries.

FIGURE 61-3 Tricuspid valve thrombus (arrows). A, B, Four-chamber steady-state free precession views obtained in diastole and systole, respectively. Thrombus is attached to the septal leaflet by a thin stalk. C, D, Four-chamber dynamic perfusion and 15-minute delayed imaging reveal no enhancement or hyperenhancement, respectively.

FIGURE 61-4 Tricuspid insufficiency. Four-chamber cine steady-state free precession shows right atrial enlargement in both diastole (A) and systole (B). Mild tricuspid regurgitation is present at systole (B, arrowhead).

FIGURE 61-5 A-C, Pulmonary insufficiency. CTA was performed in a 50-year-old patient with pulmonary insufficiency. Note the enlarged main pulmonary artery (MPA) relative to the ascending aorta (AAo) by approximately 30%.

FIGURE 61-6 Pulmonary insufficiency, status post–tetralogy of Fallot repair, determined by MRI and MRA. A, Anteroposterior chest radiograph demonstrates prominent right and left heart borders, corresponding to an enlarged right atrium (RA) and ventricle (RV), respectively, as shown on an MRA coronal reformation (B). The main pulmonary artery is mildly enlarged (A, C, D), whereas the branch pulmonary arteries (RPA, LPA) are normal in caliber. E, RV volume overload, with flattening of the interventricular septum, is also shown in a postgadolinium 15-minute delayed short-axis projection. No RV, septal, or left ventricular hyperenhancement was present.

FIGURE 61-7 Pulmonary dysplasia with stenosis and insufficiency. A, Three-dimensional MRA volume rendering demonstrates enlargement of the main pulmonary artery (MPA) and the right ventricle (RV). B, Short-axis dark blood imaging shows a dysplastic thickened pulmonary valve (arrow).

C, Fibrosis is present in the valve apparatus, evidenced by delayed hyperenhancement (arrow). Cine steady-state free precession in systole (D) and diastole (E) demonstrates both stenosis (turbulent antegrade signal, arrow) and insufficiency (retrograde signal), respectively.

FIGURE 61-8 Pulmonary stenosis and insufficiency. A 35-year-old man previously underwent tetralogy of Fallot repair with a right ventricle (RV) to main pulmonary artery conduit. A, Frontal chest radiograph shows right cardiac chamber and right pulmonary artery (RPA) enlargements. B, Three-dimensional MRA ray sum frontal projection confirms that this is secondary to right atrium (RA) and RV enlargement. C, D, RV enlargement from volume overload is also shown on the three-dimensional MRA volume-rendered images and the 15-minute delayed short-axis projection. Note the mild focal septal hyperenhancement at the RV insertion sites, related to RV strain from both volume and pressure overload. Increased pressure is caused by eccentric conduit stenosis (C, arrow). Stenosis results in turbulent flow across the conduit into the right pulmonary artery (RPA), with enlargement of the RPA.

FIGURE 61-9 Pulmonary stenosis and insufficiency with tricuspid insufficiency—functional analysis. Steady-state free precession short-axis and four-chamber projections from the patient shown in Figure 61-8 are shown in systole (A, C) and diastole (B, D). Turbulent signal (arrows) at the pulmonary valve corresponds to stenosis (A) and insufficiency (B). C, Turbulent signal (arrow) at the tricuspid valve corresponds to insufficiency. E, Quantitative analysis from phase contrast imaging yielded a pulmonary regurgitant fraction of approximately 25%.

TRICUSPID REGURGITATION

Anatomy and Normal Function of the Tricuspid Valve

The tricuspid valve is the right-sided atrioventricular valve, situated anterior and slightly apical in relation to the left sided mitral atrioventricular valve. It is aligned vertically, with anterior-left lateral angulation, in plane with the right ventricle and an orifice that is the largest of the four cardiac valves. The tricuspid valve is further distinguished from the mitral valve in that the mitral valve anteroseptal border is continuous with the aortic valve apparatus, whereas the tricuspid valve does not have any direct continuity to the pulmonary arterioventricular valve. Structurally, the tricuspid valve is composed of an annulus, three leaflets, and three commissures, which together with the right ventricle’s chordae tendinae, corresponding papillary muscles, and adjacent right atrium and right ventricle myocardium, form the tricuspid valve complex.¹ The major function of the complex is to control leaflet aperture and closure. This process is governed by the pressure gradient between the right atrium and right ventricle, which in turn is regulated by preload, afterload, and myocardial contractility. Tricuspid valve opening occurs during ventricular diastole. It is closed during systole, preventing backflow. Physiologic tricuspid regurgitation occurs during systole; however, it may be found in structurally normal hearts of 17% to 65% of adults²^–⁶ and 6.3% to 71% of pediatric patients,⁶^,⁷ with most regurgitation being trivial to mild.

With regard to the components of the tricuspid valve complex, the annulus anchors the tricuspid valve to the right trigone of the cardiac fibrous skeleton, providing firm support for the entire complex. It is oval in shape and slightly larger than the mitral valve annulus, demarcating the boundaries of the tricuspid orifice.⁸ The annulus contracts during systole and reaches maximum size at end-systole.⁹ The mean major diastolic annulus diameter, area, and fractional shortening during three-dimensional echocardiography are reported to be 3.9 to 4.3 mm, 10 to 18.4 cm², and 18.5% to 26%, respectively,^1,^8,¹⁰ whereas MRI values are reported to be 4.4 mm, 18.7 cm², and 27%, respectively.⁸ Two-dimensional echocardiography underestimates annulus diameter and fractional shortening, with reported four-chamber values of 2.9 to 3.3 mm and 13.5% to 19%, respectively.

The three leaflets, labeled as anterior, posterior, and septal, are asymmetric in size, shape, and function.¹ Each is attached to the annulus and separated and supported by the three commissures—anteroposterior, anteroseptal, and posteroseptal. Using three-dimensional echocardiography, Anwar and colleagues¹ have reported the valve area to be 4.8 cm² and each commissure to have an approximate width of 5 mm.

The anterior leaflet is the largest and most mobile, with a semicircular shape and an average width of 3.7cm.¹¹ It is located anteriorly along the right ventricular free wall, extending from the anterolateral to inferolateral margin. The septal leaflet has a semioval shape, paralleling the interventricular septum, from anteroseptal margin to the posterior right ventricle wall. It is typically smaller than anterior leaflet, but is reported to have a width up to 3.6 cm.¹¹ The septal leaflet is the least mobile of the three leaflets. The posterior leaflet extends along the posterior margin of the annulus from the inferolateral margin of the right ventricular free wall to the septum. It is variable in size and morphology, containing one or more (up to four) scallops, with an average width up to 2.8 cm.¹¹

The chordae tendinae and papillary muscles form the subvalvular apparatus. The apparatus generates opposing tension and functions to prevent leaflet prolapse into the right atrium. There are three groups of papillary muscles, labeled as anteroseptal, anteroposterior, and posteroseptal.¹² The anteroseptal and anteroposterior group may have up to four muscles, whereas the posteroseptal group may have up to five.¹² Each muscle is paired with chordae tendineae which insert onto the leaflets. There are five distinct types of tricuspid valve chordae tendineae, each with variable leaflet distribution and insertion.¹¹

Tricuspid regurgitation most commonly is secondary to other diseases such as left heart failure, pulmonary regurgitation or hypertension, or chamber enlargement, which can result in dilation of the valve annulus.¹³ Other causes of tricuspid regurgitation include rheumatic heart disease and endocarditis.¹⁴

Manifestations of Disease

Clinical Presentation

In the setting of tricuspid regurgitation, decreased cardiac output can cause fatigue and decreased exercise tolerance.¹⁵ Right atrial pressure elevation can result in lower extremity edema, hepatic congestion, and abdominal fullness. Chronic severe tricuspid regurgitation can lead to ascites and anasarca.

Patients often have a holosystolic murmur, but this is not common when there is severe regurgitation with equalization of right atrial and ventricular pressures.¹⁶ Jugular venous distention occurs in up to 75% of patients and hepatomegaly in 90%.¹⁵

Imaging Indications and Algorithm

Standard qualitative and quantitative evaluation of the tricuspid valve includes the annulus, leaflets, commissures, valve area, and degree of aperture and coaptation. Direct and indirect assessment should be made for the presence of tricuspid stenosis and regurgitation. Direct assessment includes leaflet thickening, incomplete aperture, and incomplete coaptation. Real-time echocardiography will show a regurgitant color stream and increased velocity measurement. Assessment should also address the morphology and size of the pulmonary arteries, pulmonary valve, right ventricle (including the right ventricular outflow tract), right atrium, right atrial appendage, superior vena cavae, inferior vena cavae, and central hepatic veins.

Imaging Technique and Findings

PULMONARY STENOSIS

Anatomy and Normal Function of the Pulmonary Valve

The pulmonary valve is the right-sided semilunar, ventriculoarterial valve. It is situated anterior and to the left of the aortic semilunar valve, at a 90-degree posteriorly directed plane. The primary function of the pulmonary valve is to regulate blood flow into the pulmonary arterial system and prevent backflow of blood into the right ventricle. This is achieved by the anatomic integration of three pulmonary root sinuses with three fibrous semilunar cusps, leaflets, and supporting commissures. In distinction to the tricuspid valve complex, chordae tendineae and papillary muscles are not present.

The right ventricular infundibulum and fibrous semilunar cusps provide the core structural support for the pulmonary valve. Each semilunar cusp extends from the sinotubular junction to merge with the circumferential infundibulum. The valve leaflets are incorporated into the cusps, terminating inferiorly at the ventriculoarterial junction, to define the annulus margin. Superiorly, at the sinotubular junction, the commissures provide zones of attachment for the leaflets, which are directed and open toward the main pulmonary artery.²¹

Using three-dimensional echocardiography to evaluate adult patients referred for assessment of congenital heart disease, Anwar and associates ¹ have reported the maximum diameters of the right ventricular outflow tract (infundibulum) and pulmonary valve annulus to be 22 and 19.4 mm, respectively. Two-dimensional echocardiography underestimated both regions, with measurements in the long- and short-axis projections to be 19.7 and 16.4 mm and 16.4 and 13.5 mm, respectively.²²

More than 95% of the time, pulmonary stenosis is congenital in cause.¹⁵ A common association with pulmonary stenosis (PS) is Noonan syndrome. Acquired causes of valvular pulmonary stenosis include rheumatic heart disease and carcinoid syndrome, but isolated pulmonary valve involvement is rare.

Manifestations of Disease

Clinical Presentation

PS usually causes symptoms only when severe. Symptoms include fatigue and dyspnea, lightheadedness on exertion, or syncope.¹⁵ Right heart failure can occur with long-standing severe PS. On physical examination, patients have a pulmonary ejection murmur.

Imaging Indications and Algorithm

Standard qualitative and quantitative evaluation of the pulmonary valve includes the right ventricular outflow tract, annulus, leaflets, valve area, degree of aperture, and coaptation. Direct and indirect assessment should be made for the presence of pulmonary stenosis and regurgitation. Direct assessment includes leaflet thickening, incomplete aperture, and incomplete coaptation. Assessment should also address the morphology and size of the pulmonary arteries, right ventricle, right atrium, right atrial appendage, the superior vena cavae, inferior vena cavae, and central hepatic veins.

Imaging Technique and Findings

Radiography

Typically, chest radiographs show enlargement of the main pulmonary artery caused by a poststenotic jet. The left pulmonary artery may also be dilated because the flow jet is typically directed toward the left. Diminished pulmonary vascularity may be appreciated when the stenosis is severe.

Ultrasound

Echocardiography is the primary imaging modality for the evaluation of valvular PS. Characteristic findings include thickened valve leaflets and doming of the valve during systole.²³ Continuous-wave Doppler technique can be used to obtain peak velocity. The pressure gradient is derived using the modified Bernoulli equation (see Chapter 17). PS is considered to be mild if the pressure gradient is less than 36 mm Hg, moderate if between 36 and 60 mm Hg, and severe if greater than 60 mm Hg.²³

Magnetic Resonance Imaging

VEC MRI can be used to interrogate the peak velocity and derive the pressure gradient across the valve. MRI has a limited temporal resolution compared with echocardiography, and measuring the peak velocity may be challenging because of a limited interrogation window and limitations to maximum velocity encoding. Because of the accuracy and reliability of echocardiography, the use of MRI is usually limited to situations in which the echocardiogram is suboptimal or when the pulmonary valve is assessed for another reason, such as coexisting regurgitation.

Moderate PS with a peak gradient of more than 50 mm Hg and severe PS require intervention.²³ Percutaneous balloon valvuloplasty is the usual treatment, but most patients may develop pulmonary regurgitation after valvuloplasty.²⁵ Open or percutaneous prosthetic valve placement are therapeutic options but are less commonly used than balloon valvuloplasty.

PULMONARY REGURGITATION

Pulmonary regurgitation (PR) is most commonly secondary to prior intervention, such as surgery for tetralogy of Fallot or valve repair or valvuloplasty for PS.²⁶^,²⁷ Rheumatic heart disease and endocarditis are rare causes of PR.

Manifestations of Disease

Clinical Presentation

PR results in right ventricular enlargement, and chronic severe regurgitation can lead to right ventricular dysfunction, diminished cardiac output, and ultimately heart failure.¹⁵ Arrhythmias and sudden death can also occur.²⁸ Patients with PR typically have a diastolic murmur.

The diagnosis of PR is usually made by echocardiography, which shows regurgitant color stream, increased velocity measurement. Color Doppler technique can be used to evaluate the severity of PR and to assess right ventricular pressure. The degree of PR can be graded on a 1 to 4 scale.¹⁵ Echocardiography can underestimate the degree of PR if the PR is unrestricted and the pulmonary pressure is low.¹⁹

Magnetic Resonance Imaging

MRI yields accurate quantitative evaluation of regurgitant volumes using the VEC technique. Because echocardiography has the potential to underestimate the severity of PR, MRI has a key role in the quantification of regurgitation, especially after treatment for tetralogy of Fallot.²⁹

VEC MRI can be used to interrogate flow in the main pulmonary artery and to determine the regurgitant volume and fraction.³⁰

As noted, MRI has the capability of generating highly accurate and reproducible volumes of the right ventricle (see Chapter 15), which is especially important in congenital heart disease, such as tetralogy of Fallot.²⁰ Information on the severity of PR and right ventricular volumes are used to determine the necessity for pulmonary valve repair.³⁰^,³¹

Synopsis of Treatment Options

Medical therapy has not been shown to reduce PR or its effect on the right ventricle.¹⁵ Pulmonary valve replacement (Fig. 61-10) is recommended for PR for several indications, most commonly manifestation of symptoms, including arrhythmia, decreased right ventricular function (ejection fraction <40%, as assessed by MRI), and right ventricular enlargement (MRI end-diastolic volume, 160 mL/m²).¹⁵