CHAPTER 51: TRICUSPID AND PULMONARY VALVE DISEASE

Mild tricuspid valve disease is common, and usually clinically silent.¹ Moderate and severe tricuspid regurgitation, however, are increasingly recognized as an important marker of morbidity and mortality.² By far the commonest etiology is secondary or functional tricuspid regurgitation, where the valve leaflets are structurally normal, and regurgitation is primarily a result of annular dilatation in the setting of right or left heart dysfunction or dilatation, or pulmonary hypertension.³ Secondary tricuspid regurgitation is a very dynamic lesion, commonly seen in patients with left-sided valvular disease, ischemic heart disease, or atrial fibrillation. Primary tricuspid disease is most commonly a result of endocarditis, carcinoid heart disease, or rheumatic valve disease, with lead- and catheter-related pathology from cardiac devices as an increasingly recognized cause. Apart from congenital lesions involving the pulmonary valve or the right ventricular infundibulum and carcinoid heart disease, pulmonary valve disease as an acquired condition in adults is extremely rare. The pulmonary valve is the least commonly involved in infectious processes such as rheumatic fever and bacterial endocarditis.

Tricuspid valve disease is present in 15% of the population.⁴ The tricuspid valve has recently become a more prevalent focus of interest, but used to be described as “the forgotten valve,” reflecting a clinical and research predilection for the left-sided heart valves.⁵ The most common valve lesion is secondary tricuspid regurgitation,⁶ also known as functional regurgitation.⁴ It is characterized by valvular insufficiency in an otherwise structurally normal valve, resulting from annular dilatation caused by right heart dysfunction or dilatation,⁷ pulmonary hypertension,⁸ or left heart dysfunction.

Anatomy

The tricuspid valve is the most apically (or caudally) placed valve with largest orifice among the four valves.⁹ The tricuspid apparatus includes leaflets or cusps, chordae and papillary muscles, and tricuspid annulus in addition to the right atrium and right ventricle (Fig. 51–1).

Annulus

The tricuspid annulus is oval in shape and becomes more circular when dilated. The annulus has a complex nonplanar shape with the posteroseptal portion being the lowest and the anteroseptal being the highest.⁹ It tends to become more planar with moderate or severe “functional” tricuspid regurgitation. The annular orifice area is approximately 20% larger than the mitral annulus area, with a major diameter of 3.0 to 3.5 cm in adults. The larger orifice provides for the inflow to occur at lower velocities and lower pressure decreases. Both early and late diastolic velocities are lower than the mitral inflow. The annulus expands in diastole and constricts in mid-systole, with a nearly 30% reduction in annular area. Structures that are in close proximity to the tricuspid annulus, and that may be compromised by disease processes or tricuspid valve surgery, include the atrioventricular conduction tissue that lies at the apex of the triangle of Koch (formed by the coronary sinus, septal annulus, and tendon of Todaro) (Fig. 51–2), the mid-portion of the right coronary artery, and the noncoronary cusp of the aortic valve (see Fig. 51–1).

Leaflets

The normal tricuspid valve has three distinct leaflets: septal, anterior, and posterior (see Fig. 51–1). The septal and the anterior leaflets are larger. The septal leaflet is in immediate proximity to the membranous ventricular septum (see Fig. 51–2), and its extension provides a basis for spontaneous closure of the perimembranous ventricular septal defect. The larger anterior leaflet is attached to the anterolateral margin of the annulus and is often voluminous and might appear sail-like in abnormal scenarios such as in Ebstein anomaly.

Papillary Muscles and Chordae Tendinae

There are three sets of smaller papillary muscles (when compared to left ventricular papillary muscles); each set is composed of up to three muscles. The chordae tendineae arising from each set are inserted into two adjacent leaflets. Thus, the anterior set chordae insert into half of the septal and half of the anterior leaflets. The medial and posterior sets are similarly related to adjacent valve leaflets.¹⁰

Tricuspid Valve Disease

Diastolic valve opening with expansion of the annular orifice provides for unimpeded inflow. Although systolic narrowing of the orifice is intended to result in effective valve closure, some degree of valvular regurgitation with color Doppler imaging is quite common.¹¹ Nearly 50% to 60% of young adults have trace tricuspid regurgitation. A smaller proportion of normal adults, up to 15%, have mild tricuspid regurgitation.⁴

Tricuspid valve disease or dysfunction may be classified as primary (also known as organic or intrinsic), where pathology (most commonly rheumatic valve disease, endocarditis, carcinoid heart disease, or trauma) results in structural leaflet damage; as opposed to secondary (or functional) tricuspid regurgitation, where the leaflets appear macroscopically normal.¹²

Primary Tricuspid Valve Disease

Primary tricuspid valve disease is relatively uncommon. The most common congenital abnormalities include Ebstein anomaly, tricuspid valve atresia/dysplasia/hypoplasia, cleft valve in conjunction with atrioventricular canal defects and tricuspid valve stenosis, or double-orifice tricuspid valve. Acquired diseases of the tricuspid valve are endocarditis, rheumatic disease, carcinoid heart disease, tricuspid valve prolapse, radiation lesions, trauma, iatrogenic (right ventricular myocardial biopsy), and the presence of indwelling cardiac catheters or cardiac leads (permanent pacemaker, implantable cardioverter defibrillator). The latter is increasingly recognized as a cause of significant tricuspid valve regurgitation.¹³

Rheumatic Tricuspid Valve Disease

Rheumatic involvement of the tricuspid valve is far less common than with the mitral and the aortic valves.¹⁴ Isolated rheumatic tricuspid valve disease is rare. However, clinically significant tricuspid valve disease in association with mitral or aortic valve disease is reported in 10% to 20% of patients with rheumatic heart disease.¹⁵ In addition, other inflammatory disorders like rheumatoid arthritis, systemic lupus erythematosus, and anti-phospholipid syndrome are also associated with primary tricuspid leaflet lesions that may result in significant dysfunction.¹⁶ Rheumatic tricuspid valve disease is often predominantly functional, but is occasionally characterized by leaflet involvement with thickened, fibrosed, and shortened leaflets, and commissural fusion. The resulting clinical syndrome is one of mixed stenosis and regurgitation. The murmur of tricuspid stenosis is heard along the lower left sternal border and is louder with inspiration. The opening snap is not often heard. A systolic murmur of tricuspid regurgitation is often soft, medium pitched, and increases with inspiration. Inspiratory increase in jugular venous pressure is common and simulates the Kussmaul sign in constrictive pericarditis. However, the jugular venous pulse with rheumatic tricuspid valve stenosis and regurgitation fails to show rapid “y” descent. The echocardiographic appearance of a thickened distorted valve establishes a correct diagnosis.

Treatment of rheumatic tricuspid valve disease consists of valve repair with annuloplasty when the valve dysfunction is not severe. However, in the presence of severe disease, valve replacement with a low-profile prosthetic valve is indicated. In terms of prosthetic preference, because of the higher risk of complications such as thrombosis and infection with mechanical valves, bioprostheses are preferred despite a risk of structural failure in younger subjects.¹⁷ Tricuspid valve balloon valvuloplasty has been advocated for predominant stenosis with mixed results. A common consequence is an aggravation of tricuspid regurgitation.

Infective Endocarditis

Tricuspid valve endocarditis is not uncommon among intravenous drug users or patients with long-term intravenous lines associated with dialysis and chemotherapy (Fig. 51–3; see Chap. 67). Multiple vegetations attached to the foreign materials further extending over the atrial and ventricular surfaces of an already abnormally thickened leaflet are often seen. In this context, leaflet perforations or annular abscesses are less frequent.¹⁸

The clinical presentation is one of general systemic symptoms, such as fever, weight loss, anemia, and fatigue, or of pulmonary embolism or right heart failure with hepatic congestion, peripheral edema, and ascites. The diagnostic confirmation is made by echocardiographic lesions suggestive of vegetations and positive blood cultures (Fig. 51–4).

Treatment of drug addicts with infective endocarditis is especially challenging. A prosthetic valve is at a great risk of recurrent infection as the intravenous drug use is resumed. Surgical excision of the infected tricuspid valve has been attempted with some initial success, but poor long-term outcome. Surgical repair is usually possible, and this condition among intravenous drug users continues to be a difficult management problem.

Carcinoid Heart Disease

Carcinoid tumors are rare slow-growing neuroendocrine malignancies most commonly originating from enterochromaffin cells located in the gastrointestinal tract.¹⁹ As a result of these inherent neuroendocrine properties, they have the capacity of synthetizing, storing, and secreting large amounts of vasoactive substances including 5-hydroxytryptamine (serotonin), histamine, tachykinins, prostaglandins, and possibly other growth factors.²⁰ In healthy subjects, serotonin is usually recaptured by a cellular transporter, mostly inactivated by the hepatic monoamine oxidase, and then metabolized to urinary 5-hydroxyindolacetic acid (5-HIAA) for renal clearance.²¹ In the presence of hepatic metastases, metastatic active foci of enterochromaffin cells secrete copious amounts of serotonin that will exceed and bypass the degradation capacity of the liver.²² As a result, a significant concentration of these substances is integrally released into the systemic circulation, leading to a constellation of clinical symptoms known as carcinoid syndrome.²³ The most frequent symptoms that characterize carcinoid syndrome are cutaneous flushing, gastrointestinal hypermobility, and cardiac involvement.²⁴ Cardiac manifestations, also known as carcinoid heart disease, are secondary to a plaque-like endocardial deposition of fibrous tissue that most frequently extends to the right-sided valves (tricuspid > pulmonary) and very often involves the subvalvular apparatus leading to different patterns of valve dysfunction.²⁵ Exceptions to this pathophysiologic pathway are ovarian carcinoids, which drain directly into the systemic circulation, or very rare (< 1%) cases of extensive retroperitoneal lymph node metastases with drainage to the thoracic duct.^26,27 The development of left-sided lesions implies a persistent cardiac shunt or a very severe or poorly controlled tumor activity that may overcome the pulmonary potential to inactivate serotonin.²⁸ Left-sided carcinoid heart disease only occurs in approximately 10% to 15% of patients with carcinoid syndrome (Fig. 51–5).²⁹

Carcinoid heart disease is typically characterized by an evident endocardial deposition of a pearly white fibrotic conglomerate of smooth muscle cells, myofibroblasts, and collagen³⁰, also known as carcinoid “plaque” (Fig. 51–6).³¹ Plaque formation causes annular constriction leading to relative degrees of valvular stenosis, as well as leaflet thickening and retraction, and subvalvular fusion and shortening³². In the early stages, there is mild thickening of the right-sided valves with changes of the normal concave leaflet curvature and altered motion during diastole. As the disease progresses, thickening of the leaflets extends to the subvalvular apparatus, resulting in a greater restricted motion.³³ Chordae are usually fused, and different patterns (from thick and focal to thin and diffuse) of “plaque” deposition might be observed.³⁴ In very advanced stages, the marked degeneration of leaflet architecture leads to a very severe leaflet retraction and non-coaptation of the valve, which remains fixed in a severely regurgitant semiopen position.³⁵

The clinical features are those of the carcinoid tumor and right-heart failure. The echocardiographic appearance of the thickened restricted valve leaflets is quite characteristic. Color-flow Doppler reveals wide-open tricuspid regurgitation often with laminar regurgitant flow into a large right atrium. Spectral Doppler tracing with continuous-wave Doppler shows a characteristic pattern of early peaking profile suggestive of marked elevation of right atrium pressure (Fig. 51–7).

Echocardiography is the primary imaging modality used for diagnosis and assessment of the extent and severity of carcinoid heart disease.³⁶ Tricuspid and pulmonary valves are typically thickened and retracted (type IIIA valve dysfunction). Unpublished data from our institutional ongoing research has revealed a potential role of speckle-tracking echocardiography and strain techniques in surgical referral. Classically, the evaluation of patients with carcinoid heart disease has been exclusively focused on estimations of functional valve disease. However, strain techniques have been recently proposed for the assessment of right ventricular function as an indirect measure of endocardial fibrosis. Recent series have shown a significant reduction in right ventricular function (assess by strain) in those patients with carcinoid heart disease when compared to healthy controls.³⁷ In addition to echocardiography, cardiac magnetic resonance imaging is an alternative imaging modality for the evaluation of carcinoid heart disease that can affect decision making and management because it provides accurate assessment of the volume and function of the right heart and enables quantification of the size of possible myocardial metastases and offers information regarding extension into surrounding structures (Fig. 51–8).³⁸

The gold standard treatment for carcinoid heart disease is usually tricuspid valve replacement and pulmonary valve replacement with patch enlargement of the right ventricular outflow tract.³⁹ Although tricuspid valve replacement has been traditionally accepted by most authors, the need for pulmonary valve replacement (versus isolated valvectomy) has been debatable. It is certainly true that some patients may tolerate pulmonary regurgitation; however, long-standing pulmonary regurgitation after valvectomy may have a negative impact on right ventricular remodeling. Additionally, a more uneventful postoperative recovery has been described among those patients undergoing pulmonary valve replacement and additional patch enlargement of the right ventricular outflow tract.⁴⁰

Traumatic Tricuspid Regurgitation

The traumatic injury might be external, such as blunt chest wall injury with disruption of chordal structures (Fig. 51–9); or internal, generally iatrogenic, resulting from damage from pacemaker leads, a stiff guidewire, or radiofrequency ablation for the treatment of arrhythmias.⁴¹ Tricuspid regurgitation resulting from a pacemaker lead either may be from perforation of a leaflet or its restriction as a result of chronic fibrotic changes of the leaflet and subvalvular apparatus (Fig. 51–10). It is often unrecognized because the functional consequences are slow to develop, and the regurgitation is often progressive.

Treatment is based on recognition of the cause of regurgitation. Transthoracic and transesophageal echocardiography provide important clues. Although the valve pathology is often repairable, the timing of surgery will be determined by clinical evidence of severe regurgitation before deterioration of right ventricular function or elevations in liver enzymes.

Ebstein Anomaly

This congenital lesion may first be detected at an adult age, in individuals with milder cases living up to the sixth decade of life (see Chap. 56). The characteristic features are apical displacement of the septal leaflet of the tricuspid valve and a large, sail-like anterior leaflet that results in atrialization of the right ventricular inflow. Functionally, a variable degree of tricuspid regurgitation is observed.⁴² The right heart chambers are markedly dilated. A right-to-left shunt at the atrial level may be present if atrial septal defect coexists. The clinical presentation is marked by cardiomegaly involving right heart chambers, quiet precordium with a soft systolic murmur, and abnormal electrocardiogram results with a wide QRS complex and a short PR internal. Symptomatic supraventricular arrhythmias are common. The electrocardiogram exhibits a diagnostic apical displacement of the septal and anterior tricuspid leaflets with a large, sail-like anterior leaflet. Moderate low-velocity tricuspid regurgitation may be observed.⁴³ Treatment ranges from medical management in milder forms of the disease to valve repair or valve replacement in more advanced symptomatic patients.^44,45

Tricuspid Valve Prolapse

Degenerative mitral prolapse is associated with tricuspid prolapse (Fig. 51–11).⁴⁶ In most cases, there are no distinctive physical signs (see Chap. 48). Echocardiography reveals billowing of the septal and anterior leaflets. The associated tricuspid regurgitation is generally mild. Rarely, spontaneous chordae rupture may result in severe regurgitation. When moderate or severe tricuspid regurgitation with dilatation of the annulus accompanies severe mitral regurgitation with degenerative mitral valve disease, the management consists of tricuspid annuloplasty in addition to mitral valve repair (Table 51–1).

Secondary Tricuspid Valve Disease

Secondary tricuspid regurgitation might be a consequence of right ventricular and tricuspid annular dilatation (left-sided valve disease, myocardial disease, intrinsic pulmonary hypertension, or ventricular remodeling),⁴⁷ chronic right ventricular pacing (dyssynchrony), or chronic atrial fibrillation. Mechanisms frequently coexist, and contribute to decreased leaflet coaptation. The progression of functional tricuspid regurgitation has been described as occurring in three phases:

1. An initial phase in which right ventricular and annular dilatation are present, either with or without tricuspid regurgitation.

2. An intermediate phase in which significant tricuspid regurgitation is caused by progressive annular and right ventricular dilatation.

3. An advanced phase where papillary muscle displacement as a result of right and/or left ventricular dysfunction causes leaflet tethering and more severe tricuspid regurgitation.⁴⁸

Annular dilatation is an early consequence of right ventricular dilatation or dysfunction, because of the lack of an anatomic fibrous annulus.⁴⁹ The annular circumference may increase from approximately 100 to 170 mm. Annular dilatation does not occur symmetrically; the posterior and anterior annulus are relatively unsupported and tend to dilate more than the septal annulus.⁵⁰

Pathophysiology

The primary mechanism causing regurgitation is transmission of pressure overload from pulmonary hypertension to the tricuspid valve as a raised right ventricular systolic pressure. In the absence of pulmonary hypertension, the main mechanisms underlying tricuspid regurgitation are annular dilatation and leaflet tethering.

Pulmonary Hypertension

Severe left-sided cardiomyopathy and valvular heart disease are commonly associated with elevated left atrial filling pressures directly transmitted to the pulmonary vasculature. Pulmonary hypertension is caused by the resultant increased afterload as well as compensatory pulmonary vasoconstriction, which leads to in chronic vascular remodeling.⁵¹ This causes right ventricular pressure overload, which may directly result in tricuspid regurgitation. Pulmonary hypertension partially determines the degree of secondary tricuspid regurgitation, but the relationship is not a direct one, and functional tricuspid regurgitation may also develop in the absence of demonstrable pulmonary hypertension, suggesting additional underlying mechanisms.

Annular Dilation

Annular dilation results in loss of leaflet coaptation. Annular dilatation is a strong independent predictor of secondary tricuspid regurgitation. In addition to dilating, valves with functional tricuspid regurgitation lose their normal saddle-shaped annular geometry, becoming flattened and circular with asymmetrical loss of annular contraction.⁵²

Leaflet Tethering

Leaflet tethering occurs as a result of shortening or displacement of the subvalvular apparatus (for example, shortening of the papillary muscles and chordae in rheumatic valve disease, or papillary muscle displacement in right ventricular dilatation). Secondary tricuspid regurgitation resulting from septal leaflet tethering may be observed in the context of normal right ventricular function, dimensions, and pulmonary pressure. This suggests that left ventricular pathology can contribute to functional tricuspid regurgitation, possibly caused by a dysfunctional or displaced interventricular septum causing tethering of the septal tricuspid leaflet. In one analysis of 75 patients with dilated right ventricles, eccentricity of the right ventricle and tricuspid valve tethering area were most strongly predictive of the severity of functional tricuspid regurgitation, whereas right ventricular function, dimension, and pulmonary artery pressures were not significant determinants.⁵³

Clinical Presentation

Clinical presentation depends on whether the valve dysfunction is predominantly stenotic, regurgitant, or a mixture; on the grade and chronicity of tricuspid valve dysfunction; and on the severity and nature of the causative etiology, including left-sided heart disease.

Symptoms

Moderate tricuspid regurgitation is well tolerated, and most patients with isolated functional tricuspid regurgitation are asymptomatic. Symptoms of left heart disease predominate in patients with functional tricuspid regurgitation.⁵⁴ Any history of intracardiac wires, catheters, biopsies, or intravenous injections should be elicited. Functional tricuspid regurgitation may occur late after correction of left-sided pathology, including mitral and aortic valve intervention. The symptoms specific to advanced tricuspid valve disease are related to decreased cardiac output (eg, fatigue) and right-sided hypertension (eg, liver congestion resulting in right upper quadrant discomfort, gut congestion with symptoms of dyspepsia and indigestion, and fluid retention with leg edema and ascites). Importantly, significant tricuspid disease may be asymptomatic until a late stage of the disease where symptoms are a result of the sequelae of severe right ventricular dysfunction.⁵³

Physical Examination

Characteristic physical signs may result from etiology causing tricuspid valve disease, including atrial fibrillation, congestive heart failure, pulmonary hypertension, or endocarditis. Clinical examination should include assessment of the chest, neck, arms, and abdomen for sites of previous or current venous access, indwelling catheters, wires, and cardiac devices, and cardiac surgery. Clinical signs of chronic venous congestion include dependent pitting edema, venous stasis, and ascites.

Tricuspid stenosis results in characteristic changes in the jugular venous pulse in the form of a slow V to Y descent and prominent “a” waves. The liver is enlarged with a firm edge and is pulsatile in pre-systole. Auscultation reveals a low- to medium-pitched diastolic rumble with inspiratory accentuation. This is usually localized to the lower sternal border (see Chap. 11).⁵⁵

Tricuspid regurgitation results in the jugular venous pulse exhibiting a prominent C-V wave or systolic wave. There is often a parasternal lift from right ventricular enlargement. The liver shows systolic pulsation, is enlarged, and is often tender. The cardiac auscultation reveals a soft early or holosystolic murmur, which is augmented with inspiratory effort (Carvallo sign). A systolic honk may be present with tricuspid prolapse.⁵⁶ Substantial tricuspid regurgitation may exist without the classic auscultatory findings.

Diagnosis

Electrocardiography

There are no specific markers of tricuspid valve disease, although the following clues may be present: (1) right ventricular hypertrophy and “strain” with right axis duration and (2) right atrial enlargement with prominent P-waves.

Chest Radiography

Cardiomegaly associated with prominent right heart borders may be noted. There are no specific radiographic findings to suggest a diagnosis of tricuspid valve disease.

Echocardiography

Two-dimensional echocardiography with spectral and color-flow Doppler evaluation provides the most accurate and comprehensive laboratory test in the evaluation of tricuspid valve disease (Fig. 51–12).^57,58,59 Valve morphology helps differentiate primary from secondary tricuspid regurgitation. The right heart chamber enlargement is best visualized in apical four-chamber and subcostal views, although accurate quantitation of chamber size and ejection fraction are problematic. An indirect measure of right ventricular ejection fraction is based on systolic displacement of the tricuspid annulus using M-mode recording. Tissue Doppler imaging of the annulus provides similar correlation between annular systolic velocity and right ventricular function. Real-time three-dimensional echocardiography provides additional information on morphology and function of the tricuspid valve.⁶⁰

Tricuspid valve morphology is best assessed using the parasternal tricuspid inflow view, apical and subcostal four-chamber views, and parasternal short-axis view. Abnormal structure and function of the valve provide insights into the likely underlying cause. The functional tricuspid regurgitation is characterized by annular dilatation, the extent of which may determine its severity.

Quantitation of valve lesion is obtained using spectral and color-flow Doppler approaches. Tricuspid stenosis is detected by presence of flow acceleration on the atrial side of the valve and turbulence downstream with the right ventricular inflow. The severity of tricuspid stenosis is based on mean and end-diastolic gradients measured using continuous-wave Doppler recordings. The normal mean gradient is less than 2 mm Hg, and the end-diastolic gradient is nearly zero. Significant stenosis of the tricuspid valve may be present with a mean gradient of 3 to 5 mm Hg and an end-diastolic gradient of 1 to 3 mm Hg. The use of pressure half-time to estimate tricuspid valve area and of two-dimensional echo-based planimetry of the tricuspid orifice has not been documented, and these are rarely, if ever, used.⁵⁸ Tricuspid regurgitation is detected using color Doppler imaging. Its severity may be semi quantitated based on the extent of the regurgitation jet penetration into the right atrium and inferior vena cava. Whereas the jet of the mild tricuspid regurgitation occupies up to 2 cm into the right atrium, the jet of moderate regurgitation extends deeper (3-5 cm) into the atrium but does not exhibit systolic reversal in hepatic or caval flow. However, with severe tricuspid regurgitation, there is consistent systolic flow reversal in the hepatic vein using the pulsed Doppler approach.⁶¹ A more quantitative assessment of tricuspid regurgitation may be obtained by using flow acceleration, proximal isovelocity surface area methods, and width of the vena contracta (see Chap. 15). A simpler approach is based on measuring the proximal isovelocity surface area radius. For the simpler method, the aliasing scale is adjusted at approximately one-twelfth of the peak regurgitation velocity (normally < 3.0 m/s by shifting the color scale baseline to approximately 25-30 cm/s). The proximal isovelocity surface area radius at this adjusted aliasing scale of 1 to 4 mm indicates mild regurgitation, 5 to 8 mm indicates moderate regurgitation, and greater than 9 mm indicates severe regurgitation. The width of vena contracta greater than 7.0 mm is an additional indicator of severe regurgitation.

A spectral display of tricuspid regurgitation velocity is obtained using the continuous-wave Doppler approach generally from right ventricular inflow view, short-axis view, or four-chamber view. The peak velocity used to estimate right ventricular systolic pressure is calculated as follows: right ventricular systolic pressure = 4 × peak tricuspid regurgitation velocity + right atrial pressure (see Chap. 15). The right atrial pressure is assumed to be 7 to 10 mm Hg, but may also be estimated based on the inferior vena cava size and its change with a sniff test.

The estimated right ventricular systolic pressure correlates well with that measured at cardiac catheterization. However, the upper limit of measured peak systolic pressure using the Doppler approach is 40 mm Hg rather than the 30 mm Hg measured directly. This discrepancy is partly a result of respiratory variations and assumed right atrial pressure, which may vary by 3 to 5 mm Hg from the measured mean atrial pressure. It must be emphasized that the magnitude of the velocity does not indicate the severity of regurgitation but rather the height of right ventricular systolic pressure.⁶²

Thus, a peak velocity between 3.0 and 3.9 m/s indicates moderate and in excess of 4.0 m/s severe pulmonary hypertension, even if the tricuspid regurgitation severity is mild and vice versa. The shape of the velocity profile gives considerable hemodynamic information. An early peak with rapid deceleration indicates equalization of right ventricular and right atrial pressures in late systole, generally from a large CV wave. A broadly rounded tricuspid regurgitation velocity profile that occupies 50% more of the R-R interval is indicative of impaired right ventricular function.

Transthoracic echocardiography is often of diagnostic quality because the tricuspid valve and the right ventricle are closer to the anterior chest wall and several parasternal, apical, and subcostal views are used to image these structures. However, transesophageal echocardiography is indicated for better anatomic definitions of the valve lesions or precise measurement of the tricuspid annulus (Fig. 51–12). The assessment of severity of tricuspid stenosis or regurgitation is generally more accurate with transthoracic echocardiography. This is especially true in the intraoperative setting, where severity of tricuspid regurgitation may be underestimated as a result of lowered pulmonary vascular resistance and reduced preload from the anesthetic agents and the fasted state.

In the intraoperative setting, transesophageal echocardiography is especially used for measuring the tricuspid annulus diameter. This is done in the mid-esophageal four-chamber view and a plane perpendicular (90°) to it.

Cardiac Catheterization

Invasive measurement of pulmonary artery and right atrial and ventricular pressures and pulmonary vascular resistance is helpful to guide clinical decision making in patients where physical examination and echocardiographic findings conflict; or when tricuspid jet velocity is inadequate to estimate pulmonary artery pressure. A Fick cardiac output should be measured for calculation of pulmonary vascular resistance, as thermodilution cardiac output is inaccurate in the setting of severe tricuspid regurgitation.

Treatment of Tricuspid Valve Disease

Several large studies have reported on the adverse effects of long-standing tricuspid regurgitation.^2,54,63 If treated medically, moderate-to-severe tricuspid regurgitation carries a mortality of 26% at 5 years. In addition, tricuspid regurgitation has been associated with reduced survival in patients with left ventricular systolic dysfunction.

The management of tricuspid valve disease is guided by the underlying cause and pathology of tricuspid disease. Consensus guidelines for management of tricuspid valve disease are summarized in Table 51–1. The mainstay of medical management of severe secondary tricuspid regurgitation includes loop diuretics and aldosterone antagonists to decrease volume overload in patients with peripheral edema and ascites.¹ Specific pulmonary vasodilators may be helpful to reduce right ventricular afterload in patients with reversible pulmonary hypertension evaluated with cardiac catheterization. Left-sided pathology, including left ventricular failure, and systemic hypertension should be optimized.

Surgical correction of tricuspid valve disease is most commonly performed at the time of mitral valve surgery.¹² It is less commonly performed in conjunction with aortic valve surgery, coronary artery bypass grafting, atrial fibrillation surgery, or as an isolated procedure. The goals of operative management of tricuspid regurgitation are to address abnormal anatomy and pathophysiology. This includes annular reduction and correction of significant left-sided pathology with the aim of improving of pulmonary hypertension and ventricular remodeling.⁶⁴

Isolated Tricuspid Surgery

Patients undergoing isolated tricuspid valve surgery present a unique set of challenges: right-sided valve lesions are tolerated relatively well until very late in the disease process, when severe right ventricular dysfunction and severe pulmonary hypertension become common. Severe tricuspid regurgitation makes accurate assessment of right ventricular dysfunction and pulmonary hypertension very difficult. In this context, preoperative right heart catheterization to quantify pulmonary hypertension, pulmonary vascular resistance, and right ventricular stroke work and cardiac magnetic resonance imaging to identify the etiology of the cardiomyopathy and quantify valvular and ventricular dysfunction are particularly helpful. Careful attention should also be paid to assessment of liver function: although moderate degrees of dysfunction caused by to hepatic congestion often improve after surgery, advanced cirrhosis (which is often present despite relatively mild derangements of liver enzymes and bilirubin) is commonly characterized postoperatively by refractory coagulopathy, vasoplegia, and hepato-renal syndrome.⁶⁵ Current series report perioperative mortality between 4% and 17% in patients undergoing isolated tricuspid surgery, with repair rates around 70%.^66,67 Independent predictors of mortality include age, right ventricular failure, and pulmonary hypertension.

Years after left-sided surgery, patients might present with isolated severe tricuspid regurgitation. The problems inherent in mediastinal reentry⁶⁸ in the setting of advanced cardiomyopathy and pulmonary and hepatic dysfunction are reflected in the high rate of postoperative vasoplegia, cardiogenic shock, and respiratory failure in these patients in whom multiorgan dysfunction and sepsis are among the commonest modes of death.⁶⁹

In particular cases such as carcinoid heart disease, one of the goals of surgery is to facilitate subsequent hepatic resection of metastases, which may be extensive.⁷⁰ Management of these patients is complicated by carcinoid syndrome associated with hepatic metastases, and which requires infusion of octreotide and avoidance of exogenous catecholamines to reduce the incidence of carcinoid crises, residual effects of prior chemotherapy, and hepatic dysfunction.⁷¹

Surgical Treatment of Secondary Tricuspid Regurgitation

Annular dilatation and abnormal geometry is effectively addressed by tricuspid annuloplasty,⁷² the most widely used repair technique. The many annuloplasty options can be divided into either suture or ring annuloplasty; rings may be flexible, semiflexible, or rigid, and most are incomplete. Tricuspid valve replacement is not indicated for repair of moderate functional regurgitation, as it introduces the additional risks of thromboembolic and hemorrhagic complications inherent with mechanical prostheses, or the risk of structural valve degeneration requiring reoperation associated with bioprostheses.⁷³

Tricuspid Valve Repair

The aim of tricuspid annuloplasty is to restore the dilated annulus to its physiological size, either by suturing a rigid or semi-rigid ring to the annulus or using a continuous suture to “purse-string” the annulus, relying on continued integrity of the suture and annular contraction and fibrosis to maintain the new annular dimensions.⁷⁴ Both methods stabilize the anterior and posterior annulus, which is most at risk of dilatation. Depending on the choice of annuloplasty ring, the septal annulus is kept relatively free of sutures, particularly in the anteroseptal commissural area where the conduction tissue is at risk (Fig. 51–13). Methods of plicating the posterior annulus, or sewing the leaflet edges together, have fallen out of favor as long-term results have shown relatively poor freedom from residual and recurrent regurgitation. A remodeling ring may offer the best long-term durability, and observational studies suggest that the ring repairs are more durable than the suture repairs.⁷⁵ Data from the surgical literature suggest that over 85% of patients having a ring annuloplasty for functional tricuspid regurgitation will be free from moderate or severe tricuspid regurgitation 5 to 10 years after surgery.⁶⁵

Although the presence of moderate or greater tricuspid regurgitation in patients undergoing mitral valve repair is an indication for concomitant tricuspid valve annuloplasty,^1,76 the management of secondary tricuspid regurgitation in patients with mild-to-moderate tricuspid regurgitation^77,78 remains debatable, particularly in regard to the best surgical option and whether concomitant “prophylactic” tricuspid annuloplasty is necessary. As tricuspid regurgitation is a dynamic lesion, which is downgraded by general anesthesia, the absence of tricuspid regurgitation in intraoperative transesophageal echocardiography is an unreliable indicator of severity under normal loading conditions, and the presence of tricuspid regurgitation on preoperative echocardiography becomes a more reliable indicator. Tricuspid dilatation > 4.0 cm in the four-chamber view is a measurement that is relatively independent of loading conditions, and predictive of functional tricuspid regurgitation; this may be an indication for concomitant tricuspid annuloplasty at the time of mitral valve repair, in the absence of significant tricuspid regurgitation on echocardiography (Fig. 51–14). In this context, the final decision should be guided not only by the degree of regurgitation (≥ moderate), but also by annular dimensions (diameter ≥ 7 cm from anteroseptal to anteroposterior commissures, or 40 mm when measured by echo), leaflet coaptation or mismatch between leaflet and annulus on direct inspection, presence of atrial fibrillation, pulmonary hypertension, right ventricular dysfunction, and/or left ventricular dysfunction. As for the type of repair, most authors favor the use of a disease-specific open ring with a rigid component located in the region corresponding to the right ventricular free wall aspect of the annulus (remodeling), with flexible open ends for wider accommodation of the conduction system to reduce iatrogenic injury.⁷⁹ Finally, direct intraoperative inspection may be used to compare the size of the annulus to the leaflet surface area, to determine the need for tricuspid annuloplasty (Fig. 51–15).

In tricuspid endocarditis, the tricuspid valve may be repaired after careful debridement of vegetations, repairing small leaflet perforations primarily and larger ones with autologous pericardium, and stabilizing the annulus with a ring. Tricuspid regurgitation caused by long-term pacing wires usually requires resection of the fibrotic mass from the leaflets, which may then require patch repair. Flail leaflets can be resuspended using neochordae or chordal translocation.

Tricuspid Valve Replacement

Tricuspid valve replacement is required for severe tricuspid disease unsuitable for repair. This may be a result of organic tricuspid valve disease or advanced functional tricuspid regurgitation caused by severe right ventricular dilatation and dysfunction, where isolated correction of annular dilatation will be insufficient to achieve a durable repair. Unlike left-sided valve prostheses, the main issue in prosthesis selection is usually the inability of most patients requiring replacement to comply with anticoagulation. In the case of patients with carcinoid valve disease requiring liver resection, with significant baseline hepatic dysfunction, the difficulties inherent in anticoagulation must be weighed against the levels of tumoral activity, which are inversely related to the longevity of bioprostheses in that position—high serotonin or 5-HIAA levels may be associated with severe structural valve degeneration in as little as 2 years.⁸⁰ In patients undergoing tricuspid valve replacement, permanent epicardial pacing wires are often placed, in view of the increased risk of postoperative complete heart block and the contraindication to transvalvular pacing wires.

Percutaneous Techniques

Because of the inherent risk of tricuspid valve surgery, especially in the setting of reoperative sternotomy, there is an exponential interest in the development of transcatheter techniques.⁸¹ However, according to the experts, several anatomical inconveniences must be overcome before achieving success, including: a large nonplanar annulus, absence of minor degrees of calcification or fibrosis to provide anchoring support, the presence of more trabeculations or muscle bands, and the close proximity of crucial structures such as the coronary sinus, vena cavae, or the conduction system.⁸² All these caveats have precluded valve replacement up to date; however, alternative techniques have recently emerged such as heterotopic caval valve implantation, transcatheter annuloplasty devices, coaptation devices, or the application of the Mitraclip.

Outcomes of Tricuspid Surgery

Isolated Tricuspid Surgery

Isolated tricuspid valve surgery has an associated mortality of 10% to 15% in national registries^83,84—much higher than that for isolated surgery of other valves, likely because of the much higher prevalence of advanced right heart failure and end-organ dysfunction in these patients before surgery. A decrease in operative mortality compared to historical series has resulted from incremental changes in patient selection and perioperative management including more liberal use of inhaled pulmonary inodilators such as nitric oxide and epoporostenol; management of right ventricular dysfunction using inotropes and mechanical support; and prevention and more effective treatment of end-organ dysfunction, coagulopathy, and sepsis in the postoperative period. The challenges of renal and hepatic dysfunction, right heart failure, and carcinoid crises mean that valve replacement for carcinoid disease is associated with a mortality of 10% to 20%. Long-term data on event-free survival are limited. In one recent series, the 10-year survival of patients undergoing isolated tricuspid repair was 69%, compared to 50% for those undergoing tricuspid valve replacement; and freedom from reoperation in patients with bioprostheses at 10 years has been reported to be 95%, compared to 80% at 10 years for mechanical valves.^85,86

Concomitant Tricuspid Repair

In contrast to outcomes of tricuspid regurgitation late after left-sided valve surgery, the incremental mortality posed by concomitant tricuspid annuloplasty at the time of mitral valve surgery in contemporary practice appears to be minimal. The incidence of heart block requiring pacemaker insertion is potentially greater with concomitant tricuspid surgery, although this has not been shown to be the case in experienced centers, and it is highly dependent on the choice of annuloplasty technique described above. Similarly, the theoretical incremental risk of postoperative bleeding incurred by the addition of a right atriotomy suture line has not been confirmed by studies available to date. Midterm freedom from significant tricuspid regurgitation appears significantly greater in patients with tricuspid annular dilatation or moderate functional tricuspid regurgitation undergoing concomitant tricuspid annuloplasty compared to those undergoing isolated mitral surgery, with evidence of associated improvement in right ventricular remodeling.

Anatomy

The pulmonary valve is a complex, delicate anatomical structure. The most proximal part of the valve is a continuation of the distal sleeve of the free-standing right ventricular infundibulum. This is muscular over its entire circumference, forming an independent cylindrical sleeve that can be removed from the right ventricle without any contact with the left ventricle. The sleeve of infundibular muscle gives rise to the fibroelastic wall of the pulmonary trunk at the junction between the right ventricle and the pulmonary artery (Fig. 51–16). Like this, the pulmonary valve leaflets are not directly supported by the muscular ventricular septum and lay attached in a semilunar fashion. This line of attachment crosses the anatomic ventriculoarterial junction at six different points. The semilunar line of attachment forms the border of the sinuses, with the sinus wall made up distally by arterial tissue and proximally by right ventricular muscle. Between every base of the sinuses are the fibrous interleaflet triangles. Their borderlines are the line of attachment of the leaflets laterally and the right ventricular infundibulum basally. Distally, the sinuses are confined by the sinutubular junction. Although the pulmonary leaflets are thickened along their semilunar locus of attachment between the sinutubular ridge and the muscular nadirs of the sinuses, as seen in the aortic valve, this anchor zone is considered more delicate and less amenable to manipulation than in the aortic root.

Pulmonary Valve Disease

Apart from congenital lesions involving the pulmonary valve or the right ventricular infundibulum, pulmonary valve disease as an acquired condition in adults is extremely rare (Table 51–2). The pulmonary valve is the least commonly involved in an infectious process such as rheumatic fever and bacterial endocarditis. It may be pathologically affected in carcinoid heart disease with resulting stenosis and regurgitation (Fig. 51–6).

Clinical Presentation

Bedside examination may provide important clues. Pulmonary valve stenosis is associated with characteristic auscultatory findings depending on the severity.^87,88 Mild stenosis is characterized by a systolic ejection click and a short early systolic murmur. With progressive severity, the murmur gets louder, longer, and peaks later in systole. The ejection click is often more prominent in expiration. This seemingly paradoxical behavior of the pulmonary ejection click is explained by an inspiratory increase in right ventricular end-diastolic pressure, which opens the valve in late diastole, and hence the absence of systolic ejection clicks during the inspiratory phase. Thus the ejection click may be absent in the most severe stenosis in which right ventricular end-diastolic pressure is consistently above the pulmonary arterial pressures. The behavior of the second heart sound is also of diagnostic importance. In milder cases, the pulmonary component of the second heart sound (P₂) is delayed but retains further widening with inspiration (see Chap. 11). As stenosis increases in severity, the pulmonary component becomes softer, the murmur in very severe cases spills past the aortic component, and the pulmonary component is inaudible. Clinical assessment of infundibular pulmonary stenosis reveals a systolic murmur peaking in late systole and well-preserved but delayed P₂.

Clinical assessment of pulmonary regurgitation is often more challenging. A high-pitched diastolic murmur after a prominent P₂ may be evident in patients with pulmonary regurgitation secondary to pulmonary hypertension. This murmur is often described as the Graham-Steell murmur and may be erroneously interpreted to indicate aortic regurgitation, because both may be heard best along the left sternal border. Mild or even moderate pulmonary regurgitation may be present without an audible murmur.

Diagnostic Tests

Evidence of right heart chamber enlargement is shown by 12-lead electrocardiogram and chest radiography. The echocardiogram provides diagnostic and quantitative assessment of pulmonary valve stenosis, infundibular pulmonary stenosis, and pulmonary regurgitation (see Chap. 15). The pulmonary valve morphology shows doming and incomplete opening in presence of pulmonary valve stenosis. Although the valve cusps are normal in infundibular stenosis, a characteristic midsystolic closure and prominent presystolic a-wave are often diagnostic clues. The pulmonary artery and branches are dilated in pulmonary hypertension, idiopathic pulmonary artery dilatation, and severe pulmonary regurgitation. In rare cases of pulmonary valve endocarditis, a mobile vegetation may be observed (see Chap. 67). Hypertrophied and dynamic right ventricular infundibulum is characteristic of infundibular stenosis, whether it is congenital or associated with hypertrophic cardiomyopathy. Spectral Doppler and color-flow Doppler reveal high-velocity turbulent flow in the main pulmonary artery in patients with pulmonary valve stenosis, and a late-peaking, high-velocity flow with turbulence in the right ventricular outflow tract are noted in infundibular pulmonary stenosis. Trivial and mild pulmonary regurgitation are normal findings in most children as well as adults. However, moderate and severe regurgitation are associated with right ventricular volume overload and subsequent dilatation and dysfunction. The pulmonary regurgitation velocity waveform provides a unique insight into pressure difference between the pulmonary artery and right ventricle during diastole. Because right ventricular diastole pressure equilibrates with right atrial pressure in the absence of tricuspid stenosis, an estimation of pulmonary arterial diastolic pressure is obtained using the end-diastolic velocity of pulmonary regurgitation and size of the inferior vena cava, which is used to estimate right atrial pressure.

Cardiac Catheterization and Selective Angiography

Diagnostic right heart catheterization is useful to measure pulmonary artery pressures and pulmonary wedge pressure and to calculate pulmonary vascular resistance. These are useful to differentiate and quantify precapillary and postcapillary pulmonary arterial hypertension. Although quantification of pulmonary valve stenosis is generally made using echocardiographic Doppler methods, catheter-based measurements before and after pulmonary balloon valvotomy are used to evaluate successful dilatation of the stenotic pulmonary valve. Selective angiography is less useful for diagnostic and therapeutic interventions.

Treatment

Mild and even moderate pulmonary valve stenosis and regurgitation do not result in right ventricular overload and may require no specific treatment other than prophylaxis for bacterial endocarditis (Table 51–3). Moderately severe and severe pulmonary valve stenosis is currently treated by percutaneous balloon valvotomy. Surgical valvotomy is rarely needed. Similarly, severe pulmonary regurgitation in the absence of pulmonary hypertension may require valve replacement to prevent irreversible right ventricular damage from long-standing volume overload and dilatation. A bioprosthetic valve is generally used. Recent advances in percutaneous valve replacement to treat patients with severe pulmonary regurgitation are noteworthy. The long-term efficacy of this approach remains to be proven.

We would like to thank Dr. Pravin Shah, who contributed to the previous version of this chapter in the 13th edition.