Chapter 10. Tricuspid and Pulmonic Valves

A detailed transesophageal echocardiographic (TEE) examination of the right-sided heart valves can provide accurate diagnosis of valvular diseases; define anatomic, functional, and perivalvular abnormalities; and guide appropriate management. Integration of this information with the evaluation of the cardiac chambers is necessary to assess the degree of the pathology and determine its impact on cardiac function. In a review of 1918 cases undergoing intraoperative TEE prior to cardiac surgery, discrepant findings at the time of surgical inspection were present in only 48 patients, of which five involved the tricuspid and pulmonic valves.1 Therefore, this modality should yield adequate diagnostic accuracy when the exam is conducted appropriately. This chapter discusses the main pathologies involving the tricuspid and pulmonic valves leading to regurgitation and/or stenosis, and their assessment by two-dimensional TEE (Table 10–1). Even with the advent of three-dimensional matrix array probes allowing the acquisition of real-time images, optimal visualization of the tricuspid and pulmonary valves is seldom feasible2; therefore, their three-dimensional evaluation will depend on future improvements of this technology.

Relevant Anatomical Landmarks

The tricuspid valve, the largest of the four cardiac valves, lies slightly below the plane of the mitral valve, and is in close proximity to the aortic valve. The three leaflets of the tricuspid valve are named anterior, posterior (inferior), and septal (medial) based on their relative positions (Figure 10–1). The septal leaflet's insertion point at the septum is more apically displaced than that of the anterior mitral leaflet. The two major papillary muscles, the anterior and posterior, are located on the corresponding walls of the right ventricle. Through their chordae tendineae, they attach to the anterior and posterior cusps, and the posterior and septal cusps, respectively. When present, a smaller septal papillary muscle attaches to the septal and anterior cusps.3 The three leaflets of the valve can be imaged using different angulations of the imaging plane together with flexion of the probe tip (see Figure 10–1).

Tomographic Views

Midesophageal Four-Chamber View

From the midesophageal four-chamber view, rightward rotation of the probe can help position the tricuspid valve in the center of the image. This view will show the septal leaflet to the right of the display and the nonseptal (anterior or posterior) leaflet to the left of the display, depending on the amount of anteflexion or retroflexion of the probe (Figure 10–2).

Midesophageal Right Ventricular Inflow-Outflow View

Starting from the midesophageal four-chamber view, rotating the angle forward to approximately 60° will yield a cross-sectional view of the aortic valve, with a transverse section of the right ventricular inflow and outflow tracts. Slight turning of the probe to the right might be needed for better visualization of the structures. In this view, the anterior leaflet of the tricuspid valve is seen next to the aortic valve. The posterior leaflet of the tricuspid valve is seen to the left of the display attached to the right ventricular wall (Figure 10–3).

Transgastric Right Ventricular Inflow View

Turning the probe to the right in the transgastric short-axis view of the left ventricle will bring the right ventricle to the center of the display. A long-axis view of the right ventricle is then obtained by rotating the multiplane angle to about 120°. The chordae tendineae and papillary muscles are well seen, since they are perpendicular to the ultrasound beam. In this view, the posterior leaflet of the tricuspid valve is visualized in the near field, attached to the inferior wall, while the anterior leaflet is located in the far field, attached to the anterior wall of the right ventricle (Figure 10–4).

Transgastric Tricuspid Short‐axis View

Starting from the transgastric right ventricular inflow view, the tricuspid annulus is centered in the image by slightly withdrawing the probe. Rotating the angle back to about 30° will generate a short-axis view of the tricuspid valve. The septal leaflet is visualized to the right of the display. The anterior and posterior leaflets are seen in the left-sided far and near fields, respectively (Figure 10–5).

Common Causes

Trivial or very mild degrees of tricuspid regurgitation can frequently be present in normal individuals, and in the absence of abnormalities of the valvular structures or cardiac chambers, it should be regarded as a normal variant. Pathologic tricuspid regurgitation can be either congenital or acquired. Ebstein's anomaly is one of the important causes of congenital tricuspid regurgitation, and echocardiography plays a major role in the diagnosis and surgical planning. More commonly, however, tricuspid regurgitation is the result of right ventricular dilatation and/or dysfunction secondary to pulmonary hypertension or right ventricular infarction. Rheumatic heart disease (less frequently encountered in developed countries) and carcinoid heart disease result in thickening, restricted mobility, and/or malcoaptation of the leaflets, leading to incompetence of the valve. In patients with endocarditis, vegetations that tend to form on the atrial surface of the leaflets can lead to destruction of the leaflets and/or chordae, causing significant degrees of regurgitation in advanced cases. Annular dilatation can be seen in some cases of Marfan's syndrome, and tricuspid valve prolapse with or without associated mitral valve prolapse is another cause of tricuspid regurgitation. Occasionally, tumors such as right atrial myxomas can interfere with the normal coaptation of the leaflets, therefore causing regurgitation.

Two-Dimensional Evaluation

Two-dimensional examination of the tricuspid valve apparatus provides significant information regarding the underlying cause and mechanism of tricuspid regurgitation. The identification of anatomic abnormalities (eg, Ebstein's anomaly), abnormal masses, annular dilatation, and noncoaptation (see Figure 10–3) are all essential to make a correct diagnosis. Pacemaker wires or catheters passing through the tricuspid orifice are readily visualized (Figure 10–6), and although uncommonly encountered with the right-sided valves,4 TEE is highly sensitive for the detection of vegetations.5 Movement of any of the leaflets beyond the plane of the tricuspid annulus inside the right atrium indicates the presence of tricuspid prolapse (Figure 10–7).6 Additionally, in patients with tricuspid valve prolapse, the leaflets and chordae are usually redundant and myxomatous. Features characteristic of Ebstein's anomaly include apical displacement or “off-setting” of the hinge point attachment of the septal leaflet relative to that of the anterior mitral leaflet. A displacement index is easily produced by measuring the distance between the two hinge points and indexing to body surface area. This can be done in the midesophageal four-chamber view, and different angulations of the probe will help obtain the maximal difference. An indexed value greater than 8 mm/m squared7,8 or a nonindexed value of greater than 15 mm in children and 20 mm in adults,9 together with elongation of the anterior leaflet (the so-called “sail-like” or “curtain-like” appearance),10,11 tethering, and restricted leaflet motion,7 distinguish this congenital anomaly from other causes of tricuspid regurgitation. Additional echocardiographic features of Ebstein's anomaly include apical displacement of the other leaflets, absence or fenestration of any of the leaflets, and “atrialization” of a part of the right ventricle.

Carcinoid heart disease in patients with carcinoid syndrome results from fibrous deposits on the endocardium of the right-sided valves and chambers. This leads to thickening and rigidity of the leaflets, with the valves fixed in an open position, and associated stenosis is common. Involvement of the left-sided valves should prompt a careful evaluation for right-to-left shunting.12 Thickening, shortening, and restricted mobility of the leaflets are all characteristics of rheumatic involvement of the valve. The presence of malcoaptation of the leaflets usually indicates severe regurgitation, as does a large tricuspid annulus (>2.1 cm/m2 of body surface area).13 Although measurement of the tricuspid annulus should be performed in multiple views during diastole, using the frame that shows maximal distance between the insertion points of the leaflets, the measurement from the transgastric right ventricular (RV) inflow view correlates best with surgical measures.14 Moreover, the dimensions of the right-sided chambers can provide clues to the severity of regurgitation. In contrast to mild regurgitation, chronic moderate and severe tricuspid regurgitation are usually associated with a dilated right atrium and ventricle. This is, however, not true in cases of acute moderate or severe tricuspid regurgitation where the chambers do not have time to remodel.

Doppler Evaluation

Color Doppler mapping can detect and provide a degree of quantification of the severity of tricuspid regurgitation. When applied, the multiplane angle should be changed and the probe tip manipulated in order to demonstrate the largest possible jet of regurgitation (Figure 10–8). Doppler principles similar to those used in the assessment of mitral regurgitation can be used to assess tricuspid regurgitation (Table 10–2). Measuring the vena contracta, which is the narrowest portion of the jet at the orifice of the valve, is easy to perform in the midesophageal four-chamber view; the cutoff for severe regurgitation is considered to be7 mm.15,16 In centrally directed regurgitation, measurement of the jet area can be helpful; an area of greater than 10 cm2 is indicative of severe insufficiency.16 Doppler parameters that indicate increased severity of tricuspid regurgitation include a tricuspid inflow velocity higher than 1 m/s, and a dense, triangular, and early-peaking continuous-wave (CW) Doppler signal of the tricuspid valve. The proximal isovelocity surface area (PISA) method can be applied for more quantitative assessment (Figure 10–9). A simplified approach has been suggested, whereby measuring the PISA radius at a Nyquist limit of about 28 cm/s can provide an estimate of the severity of the regurgitation; a radius of 5 mm or less usually identifies mild degrees, and a radius greater than 9 mm is found in severe cases.16

In addition, severe tricuspid regurgitation is associated with systolic flow reversal in the hepatic veins and/or the coronary sinus, similar to what is seen in the pulmonary veins in the case of severe mitral regurgitation.

Hepatic Venous Flow Patterns

Imaging of the hepatic veins can be performed from the stomach by withdrawing the probe and rotating it to the right to visualize liver parenchyma in the transverse plane. The hepatic veins can be identified with the help of color Doppler (Figure 10–10) at a reduced Nyquist limit (<40 cm/s). Pulsed-wave (PW) Doppler is used to assess flow patterns in the largest hepatic vein identified. A normal flow pattern consists of larger systolic and smaller diastolic forward-flow waves. In addition, two flow-reversal waves may be noted: one in late diastole (which is the result of atrial contraction) and another in late systole. A blunted or reversed systolic wave is seen in patients with severe tricuspid regurgitation.17 Patients with elevated right atrial pressures or atrial fibrillation can exhibit blunting of the systolic wave.

COronary SInus FLow PAtterns

PW Doppler sampling of the coronary sinus flow is best performed in the transverse view of the coronary sinus, obtained from the midesophageal four-chamber view by advancing the probe slightly and retroflexing it. This will visualize the coronary sinus in its long axis in the atrioventricular groove (Figure 10–11). In normal individuals with absent or mild degrees of tricuspid regurgitation, two negative waves are noted: a late systolic wave and a diastolic wave with higher velocity and longer duration. When severe tricuspid regurgitation is present, reversal of the systolic wave is seen. This finding has a high sensitivity and a good specificity for the detection of severe tricuspid regurgitation.18

Estimation of Systolic Pulmonary artery Pressure

Using CW Doppler, measurement of the peak tricuspid regurgitation jet velocity can be performed. Usually, the midesophageal right ventricular inflow-outflow view provides good alignment of the regurgitation jet with the Doppler signal. Localization of the jet is assisted by color Doppler flow mapping, and angulation of the probe with adjustment of the multiplane angle should be performed in order to identify the maximal velocity jet (Figure 10–12). Based on the simplified Bernoulli equation, the pressure gradient between the right ventricle and atrium is given by:

Pressure Gradient (mm Hg) = 4 × [Peak Regurgitant Velocity (m/s)]2

When added to an estimate of the right atrial pressure, this gradient provides an approximation of the right ventricular systolic pressure, which in the absence of right ventricular outflow obstruction is equivalent to the systolic pulmonary artery pressure. Right atrial pressure is commonly assessed by examining the respirophasic changes in the diameter of the inferior vena cava (IVC) (Figure 10–13). A greater than 50% change in the diameter of the IVC with inspiration indicates a right atrial pressure of less than 10 mm Hg, while a less marked change is associated with a pressure that is above 10 mm Hg.19 This, however, is not reliable in patients on mechanical ventilation, or in those who do not mount a good inspiratory effort. In these patients, right atrial pressure can be assessed by examining the PW Doppler pattern of the hepatic veins, based on the following formula20:

Mean Right Atrial Pressure (mm Hg) = 21.6 − (24 × SFF)

where SFF is systolic filling fraction of the hepatic venous flow, which is obtained by dividing the hepatic vein systolic velocity-time integral (VTI) by the sum of systolic and diastolic VTIs. For the purpose of simplification, peak velocities can be used in lieu of VTIs.20 This method, however, has not been validated in patients with severe tricuspid regurgitation; instead, the right atrial pressure can be estimated in these patients at a constant of 20 mm Hg, especially in the presence of other indicators of elevated right atrial pressure (eg, significantly distended jugular veins).21

More recently, Arthur et al22 found that measurement of the IVC diameter by TEE can provide an estimate of the central venous pressure (CVP) in mechanically ventilated patients. In their study, the IVC diameter was measured in the bicaval view (at 110°) at the level of the cavo-atrial junction and at the end of the T-wave of the electrocardiogram. The ventilator was turned off at time of the measurement to eliminate the effect of intrathoracic pressure changes. The linear regression–derived equation to calculate the CVP based on the IVC diameter [CVP = (IVC diameter − 4.004)/0.751] showed a good correlation with catheter-measured CVP. Based on their findings, we propose the following simplified formula for estimating the CVP based on the IVC diameter:

CVP (mm Hg) = 4/3 × [IVC diameter (mm) − 4]

Common Pathophysiology

Tricuspid stenosis is less frequently found in the community given the low incidence of rheumatic heart disease, the most common cause of this valvular lesion. In areas where rheumatic heart disease is still prevalent, tricuspid stenosis is usually associated with involvement of other valves, namely the mitral valve. In addition, it is frequently coupled with tricuspid regurgitation. Rheumatic disease leads to thickening of the leaflets and commissural fusion as well as involvement of the subvalvular apparatus.23 Other causes of tricuspid stenosis include endomyocardial fibrosis and carcinoid heart disease, in which fibrous deposits on the endocardium lead to thickening of the valve and leaflets that are fixed in a semi-open position. This is invariably associated with regurgitation. When present, the increased flow from the regurgitation will lead to higher gradients across the valve. Patients with tricuspid stenosis usually have a significantly dilated right atrium. Dilatation of the right ventricle is a function of the severity of the associated tricuspid regurgitation.

Two-Dimensional Evaluation

Careful examination of the tricuspid leaflets is needed to assess for thickening and/or calcifications, and for the presence of restricted mobility with or without doming in diastole (Figure 10–14). Planimetry of the valvular orifice in the transgastric short-axis view can be attempted, but is difficult and unlikely to yield accurate results. Lesions (tumors, large vegetations, etc) causing mass obstruction of the valvular inlet can be identified. Information from the assessment of the other valves and chambers can help in the determination of the underlying etiology of stenosis, such as involvement of the mitral valve in patients with rheumatic heart disease or the pulmonic valve in patients with carcinoid disease. The presence of left ventricular dysfunction and apical thrombus raises the possibility of endomyocardial fibrosis as a cause for tricuspid stenosis. In general, the right atrium and inferior vena cava are dilated, especially in chronic and more severe cases.

Doppler Evaluation

Color Doppler usually reveals evidence of turbulent, high-velocity flow. Using PW Doppler with the sample volume placed at the tip of the leaflets, the RV inflow velocities can be shown to be increased (>0.7 m/s).24 This is typically performed in the midesophageal right ventricular inflow-outflow view where the Doppler beam can be aligned with the blood flow. Assessment of the diastolic pressure gradients using CW Doppler can be performed while increasing the sweep speed (100 mm/s) for better accuracy of measurements (Figure 10–15). Also, it is recommended to average at least five cycles to account for respiratory variations, or changing cycle length in patients with atrial fibrillation. As with the other valves, the pressure gradient across the tricuspid depends on both the valvular orifice area and the flow across it, which is increased in the presence of concomitant regurgitation. However, current assessment of severity of tricuspid stenosis is mainly based on the gradient alone, with a mean gradient of more than 5 mm Hg considered reflective of severe stenosis.24 The pressure half-time (PHT) method using a constant of 190 (i.e. 190/PHT) can be used to estimate the orifice area,25 but is not as well validated as for mitral stenosis, and is of limited usefulness in clinical practice. Finally, in the absence of regurgitation, dividing the stroke volume measured at either the left or right ventricular outflow tract by the tricuspid inflow VTI from the CW Doppler recording (continuity equation) can be used to calculate the stenotic orifice area.26 An area of 1 cm2 or less is consistent with significant tricuspid stenosis (Table 10–3).24

Relevant Anatomical Landmarks

The three cusps of the pulmonic valve are labeled as the anterior, right, and left cusps. The names of the cusps are derived from their developmental origin from the truncus arteriosus.3 The plane of the opening of the pulmonic valve faces superiorly and to the left (see Figure 10–1).27 Due to its anatomical position away from the esophagus, the pulmonic valve is frequently difficult to image by TEE.

Tomographic Views

Midesophageal Short‐Axis View

The short-axis view of the aortic valve is first obtained from the midesophageal position with the multiplane angle set between 35° and 50°. Withdrawing the probe slightly along with minor rotation will bring up a long-axis view of the pulmonic valve (Figure 10–16). In this view, the pulmonary valve and the proximal segment of the main pulmonary artery are located to the right of the display. The anterior pulmonary cusp is seen in the far field and the right cusp is seen in the proximity of the aortic valve.28

Midesophageal Right Ventricular Inflow-Outflow View

In this view, the pulmonic valve can be visualized along its long axis to the right of the display (see Figure 10–3). Color-flow Doppler can be used to assess for the presence of pulmonary insufficiency (Figure 10–17). In some patients with heavy aortic valve calcifications or a prosthetic aortic valve, acoustic shadowing can prohibit adequate visualization of the pulmonic valve. In addition, the direction of the pulmonary blood flow is almost perpendicular to the Doppler beam, making assessment of velocities and gradients unreliable in this view.

Upper Esophageal Aortic Arch Short‐Axis View

This imaging plane provides a long-axis view of the pulmonic valve and pulmonary artery with the ultrasound beam being almost parallel to the direction of blood flow. It is obtained from the upper esophageal window with the multiplane angle at approximately 90°, along with rotation of the probe to the left. The pulmonic valve and pulmonary artery are seen to the left of the display (Figure 10–18). Slight retroflexion of the probe and an increased imaging depth are often needed to better visualize the pulmonic valve.

Transgastric Right Ventricular Inflow-Outflow View

This view is obtained from the transgastric position at the midpapillary muscle level, by turning the probe to the patient's left and forward rotation of the multiplane angle to 110° to 140°. The right ventricular outflow tract (RVOT) and pulmonic valve (PV) will appear in the mid-far field, parallel to the beam, often in optimal position for color and spectral Doppler analysis (see Chapter 13).

Deep Transgastric Right Ventricularoutflow View

This image is obtained by advancing the probe to the deep transgastric position, flexing the tip to identify the deep-transgastric images of the left ventricle (LV), and turning the probe slightly towards the patient's right side (see Chapter 13).

Common Causes

In the adult population, pulmonary hypertension leading to pulmonary artery and annular dilatation is the most common cause of pulmonary regurgitation. Connective tissue disorders, such as Marfan's syndrome, can also lead to dilatation and insufficiency. Carcinoid and rheumatic heart disease cause restricted leaflet mobility and malcoaptation. Additional etiologies include endocarditis, trauma, congenital malformations, and complications of surgical interventions (repair of pulmonary stenosis or tetralogy of Fallot).

Two-Dimensional Evaluation

Two-dimensional echocardiography is essential in defining the anatomy of the pulmonic valve. Lesions such as annular dilatation, valve prolapse, vegetations, congenital malformations, and rheumatic involvement are frequently easily identified. Thickening and restricted mobility, malcoaptation (Figure 10–19), along with narrowing of the annulus can be seen in patients with carcinoid heart disease.12 The presence of right ventricular dilatation in the absence of other etiologies is usually indicative of severe chronic pulmonary insufficiency.

Doppler Evaluation

There is no validated quantitative grading of pulmonary regurgitation using TEE. Assessment of pulmonary regurgitation is commonly performed qualitatively (Table 10–4).29 Transthoracic echocardiography has relied on jet width and jet length. A ratio of the jet width to the right ventricular outflow tract diameter of no greater than 38% indicates mild to moderate pulmonary regurgitation; a ratio of 39% to 74% indicates moderate to severe regurgitation; and a ratio of at least 75% indicates severe regurgitation.30 A jet length shorter than 10 mm has been found in normal subjects with no cardiopulmonary disease, whereas a jet length longer than 20 mm has been associated with pulmonic insufficiency murmur.31 As with aortic regurgitation, it should be remembered that jet length is dependent on loading conditions and ventricular compliance. Figure 10–20 displays the color Doppler signal of moderate to severe regurgitation in a patient with carcinoid syndrome.

CW Doppler interrogation of the pulmonic regurgitation jet in the upper esophageal aortic arch short-axis view, the transgastric right ventricular inflow-outflow view, or the deep transgastric right ventricular outflow view allows estimation of the end-diastolic flow velocity, and therefore the end-diastolic gradient (using the simplified Bernoulli equation) between the pulmonary artery and the right ventricle. This gradient can be used to estimate the pulmonary artery diastolic pressure by adding an estimate of the right atrial pressure,32 and is equal to that of the right ventricle at end-diastole, if there is no pulmonic valve stenosis (see Chapter 4). Furthermore, the slope of the Doppler envelope can provide information about the severity of the pulmonic regurgitation, with steeper slopes being associated with significant degrees of regurgitation.33 Recently, a pressure half-time of the pulmonary insufficiency jet of less than 100 milliseconds was found to reliably identify patients with adult congenital heart disease who had angiographically confirmed severe regurgitation.34

Common Pathophysiology

Pulmonic stenosis is mostly a congenital lesion, with the abnormal valve having abnormal leaflet number or morphology. Sometimes, associated abnormalities of the right ventricular outflow tract are noted. In the adult population, pulmonic stenosis can result from rheumatic heart disease or carcinoid syndrome wherein involvement of other valves is usually evident.23 Right ventricular outflow tract obstruction can result from hypertrophy of the infundibular septum, protrusion of the right sinus of Valsalva of the aortic valve into the right ventricular outflow tract, aneurysm of membranous ventricular septum, and the presence of mass lesions such as sarcoma. Congenital conditions such as tetralogy of Fallot can be recognized from the presence of associated malformations (Figure 10–21; see Chapter 18). The presence of pulmonic stenosis and/or right ventricular outflow tract obstruction leads to increased afterload and consequently hypertrophy of the right ventricle. In advanced cases, right ventricular failure and dilatation may ensue, leading to the development of tricuspid regurgitation.

Two-Dimensional Evaluation

Examination of the leaflets and their mobility in the long axis can be performed in most of the views defined above. The presence of thickening, calcifications, and doming in systole should be noted. Abnormalities of the outflow tract can be detected in the midesophageal views, whereas the upper esophageal aortic short-axis view provides good imaging of the proximal part of the pulmonary artery. Direct planimetry of the pulmonic valve cannot be performed since the valve is not imaged well in cross section by TEE. Examination of the right ventricular chamber size and function is helpful for the assessment of the severity of the stenosis.

Doppler Evaluation

Using color-flow Doppler, the pattern of flow across the valve can be assessed; the presence of aliasing indicating turbulent flow should alert the examiner to the possibility of outflow obstruction. Also, color-flow Doppler can help guide the appropriate positioning of the CW Doppler cursor for optimal measurement of mean and peak gradients. This is readily performed in the upper esophageal aortic arch short-axis view (Figure 10–22), or occasionally in the transgastric right ventricular inflow-outflow or deep transgastric right ventricular outflow views, where the blood flow across the valve is almost parallel to the Doppler signal. Assessment of the VTI of the right ventricular outflow tract and measurement of the diameter of the right ventricular outflow tract during early systole can be used to assess flow through the right ventricular outflow tract.35,36 Combined with VTI of the pulmonic valve, the area of the valve can potentially be calculated using the continuity equation. A late-peaking, “dagger-shaped” Doppler envelope should alert the operator to the presence of dynamic outflow tract obstruction. Since there is lack of validated methods to accurately assess valvular area, grading of pulmonic stenosis relies largely on the gradients across the valve, with cutoffs for moderate and severe stenosis being a velocity of 3 m/s (gradient of 36 mm Hg) and 4 m/s (gradient of 64 mm Hg), respectively (Table 10–5).15,24

TEE can provide accurate evaluation of the right-side cardiac valves. Details of the anatomy of the leaflets, subvalvular apparatus, and associated lesions can be readily appreciated. Complete assessment requires combining two-dimensional and Doppler data together with information about the cardiac chambers. This will provide the necessary information to make accurate diagnoses and guide appropriate management. Further technological advances are needed before three-dimensional evaluation of the tricuspid and pulmonic valves becomes a routine part of a comprehensive TEE examination.