Echocardiographic Evaluation of Prosthetic Valves

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5 Echocardiographic Evaluation of Prosthetic Valves

Andrew D. Maslow, Arthur A. Bert

Introduction

Key Points

• Echocardiography is the definitive technique for the noninvasive evaluation of prosthetic valve function, both bioprosthetic and mechanical.

• On occasion, fluoroscopy is used as an adjunct in the evaluation of mechanical prostheses.

• The echocardiographer should be most familiar with the prosthetic valves used at his or her institution; however, patients will present with different prostheses from other institutions, so that sources of reference (such as the tables in this chapter) must be readily available.

• Acoustic shadowing from the prosthetic ring and leaflets may be critical; alternate windows and off-axis views become vital.

In patients with valvular (native or prosthetic) dysfunction, valve replacement remains a common definitive therapeutic intervention. Echocardiography is the method of choice for the noninvasive evaluation of prosthetic valve function.

Although many of the same principles and techniques utilized in the assessment of native valves are applied, echocardiography of prosthetic heart valves is much more demanding both to image and to interpret owing to imaging artifacts produced by the prosthetic materials. These artifacts vary depending on what type of valve is placed.

Although the evaluation of the prosthetic valve is primarily focused on the valve itself, the examiner must still perform a comprehensive examination of the surrounding cardiac tissues to assess for coexisting disease or secondary abnormalities and dysfunction.

Because there are so many available prosthetic valves, each with very distinctive two-dimensional (2D) and color flow (CF) Doppler acoustic profiles (Table 5-1), the echocardiographer should have access to the type and size of the in situ prosthetic valve and the reason the study has been ordered to focus the study and facilitate image interpretation.

TABLE 5-1 REPORTED RANGES OF HEMODYNAMIC DATA FOR COMMONLY PLACED PROSTHETIC VALVES*

This chapter describes and discusses the heart ultrasound examination using transesophageal (TE) and transgastric (TG) imaging and windows. It is accepted that epicardial and transthoracic examinations are complementary.

General Considerations With Prosthetic Valves (Figure 5-1)

Types of Prosthetic Valves

Prosthetic valves are usually broadly grouped as biologic or mechanical.

Figure 5-1 Flow chart of assessment of prosthetic valves in the operating room (OR). CFD, color flow Doppler; PWD, pulsed wave Doppler.

Basic Principles Of The Echocardiographic Examination

Two-Dimensional

• Prosthetic valves should be imaged from multiple windows and angles to overcome the problem of acoustic shadowing that occurs owing to the highly reflective components inherent in many of these valves.

• Nonstandard windows and angles are often required to avoid imaging artifacts. Transesophageal echocardiography (TEE) becomes especially useful in evaluation of prosthetic valves in atrioventricular positions because it provides acoustic access from the atrial side of the valve.

• Prosthetic mitral valve (MV) assessment:

• TE windows provide 2D and Doppler analyses.

• TG windows offer a limited benefit in assessing the prosthetic MV.

• Prosthetic AV assessment:

• TE windows provide 2D and color Doppler imaging.

• TG windows provide another view of the AV. Although farther from the transducer, these windows could be useful when TE imaging is limited possibly as a result of artifacts. Otherwise, TG imaging provides an opportunity to quantitatively interrogate the valve using pulsed wave (PW) and continuous wave (CW) Doppler.

• Prosthetic tricuspid valve (TV)

• TE windows provide 2D and Doppler analysis, the latter including color, PW, and CW Doppler.

• TG windows may provide imaging for 2D and color Doppler imaging more than PW or CW Doppler.

• Prosthetic PV

• TE imaging is weaker than for other valves. Nonstandard windows may provide a more complete analysis.

• TG windows can visualize the right ventricular outflow tract (RVOT) and PV.

• General points of 2D imaging of prosthetic valves

• The opening and closing of the mechanical valve disks or bioprosthetic cusps must be evaluated.

• Failure of a disk to open will significantly reduce the prosthetic valve’s EOA and thus result in increased pressure gradients across that valve.

• Failure to close properly will result in increased regurgitant flow.

• Mechanisms of prosthetic valve dysfunction are both similar to and different from those of the native valves. Knowledge of these mechanisms is important to guide the echocardiographer during the assessment.

• The presence of cusp thickening is usually an early sign of primary failure of a bioprosthetic valve.

• Increased echo-dense lesions attached to a prosthetic valve sewing ring, stents, disks or occluder, and/or calcifications of bioprosthetic leaflets are signs of possible prosthetic valve pathology and possible failure.

• Incomplete closure of prosthetic valve leaflets can be due to pannus growth, infection, thrombus, or suture materials around the sewing ring or the leaflets.

• Increased distance or separation of the prosthetic valve sewing ring from the native annulus is always pathologic and may appear as an echolucent space, a thickening, or a “rocking” motion of the valve during the cardiac cycle. These abnormal findings suggest a dehiscence of the prosthetic valve.

• “Focused” or magnified views are useful to assess the range of motion of individual disks or cusps as well as image and characterize abnormal perivalvular lesions.

Doppler Echocardiography

• The Doppler examination includes CF, PW, and CW Doppler examinations. Each method contributes toward qualifying and quantifying flow patterns of both normal and abnormally functioning prosthetic valves. The principles and rationale in utilizing Doppler techniques to qualify, measure, and quantify blood flow velocities, pressure gradients, and effective valve orifice areas of prosthetic valves are similar to that of native valves. However, the “normal” flow profiles of prosthetic valve are NOT assumed to be equal to that of normal functioning native valves.

• Given the variety of prosthetic valves available, different systolic and diastolic flow patterns across the valves exist. Although this is the case, assessment of severity of abnormal flows follow similar guidelines. For example, all perivalvular regurgitant leaks are considered abnormal. Those with a vena contracta width of greater than 3 mm have a greater potential to persist and/or worsen regardless of the prosthetic valve type.

Color Flow Doppler

Mechanical Valves

• All mechanical valves display “normal” regurgitant jets, sometimes referred to as “washing jets.” These flows are thought to prevent the formation of thrombi at sites of blood flow stasis. These jets are typically small (vena contracta < 3 mm), have a low velocity and a uniform color pattern (minimal aliasing at most), and do not extend far from the valve plane.

• The “normal” degree of regurgitation of prosthetic valves, detected by CF Doppler, is greater than the trivial amounts seen in normal native valves. The patterns of regurgitation detected by CF Doppler are distinct (“signature patterns”) for each mechanical valve type, corresponding to their fluid dynamics. While casting an identifiable “signature” pattern of regurgitant plumes, the associated regurgitant fraction is less than 10% to 15%.

• Valve types

• Ball-cage valve

• A ball-cage valve in the open position will demonstrate antegrade blood flow around all sides of the ball occluder and across the cage orifice. In the closed position, CF Doppler demonstrates a small regurgitant jet circumferentially around the ball as it seats in the cage orifice.

• Single tilting disk valve

• Antegrade blood flow across a single tilting disk prosthetic valve is characterized by a CF Doppler signal across a major and a minor orifice. CF Doppler will indicate nonlaminar and asymmetrical flow as blood accelerates along the tilted surface of the open disk.

• In the closed position, a single tilting disk normally demonstrates a regurgitation jet directed away from the sewing ring starting at the edge of the major orifice. Surgical preference on implantation determines the open disk position and, hence, the direction of the regurgitant jet normally seen on disk closure.

• Bileaflet valve

• This valve has a complex blood flow profile when interrogated by CF Doppler. In the open position, CF Doppler will demonstrate antegrade flow through two larger lateral orifices and a small central orifice.

• When a bileaflet mechanical valve is imaged in the closed position, multiple “washing” jets of regurgitation are normally seen in the plane parallel to the leaflet-opening plane. All the regurgitant jets are located inside the sewing ring, with two jets originating from where the leaflets meet the housing and a third, central jet originating where the leaflets meet each other.

Bioprosthetic Valves

• Stented bioprosthetic valves display antegrade flow patterns closer to that of a normal native valve through a single orifice.

• “Normal” retrograde or regurgitant jets are centrally directed and do not extend far from the closed valve.

• Stentless valves including homografts and autografts usually demonstrate minor regurgitant jets that are central and limited in jet area and homogeneous in color.

General Points Regarding Color Doppler Assessment

• Pathologic regurgitant jets have higher velocities such that a color-mosaic pattern occurs from aliasing and create significant regurgitant momentum resulting in larger jet areas on CF Doppler imaging.

• The severity of prosthetic valve regurgitation is graded by criteria similar to that used for the native valve. The extent of the regurgitant jet into the receiving chamber as measured by CF Doppler (either the width of the vena contracta or the ratio of the CF Doppler jet area to the area of the atrium or the ratio of the width of the aortic insufficiency [AI] jet to the width of the left ventricular outflow tract [LVOT]) is often utilized.

• CF Doppler-detected regurgitant jets that originate outside of the prosthetic sewing ring (paravalvular) are always pathologic.

• Although paravalvular regurgitation is always abnormal, small jets are often imaged on CF Doppler immediately after valve implantation in the operating room. To be clinically and hemodynamically insignificant, these jets should be small in comparison with the total circumference of the sewing ring they originate from. Many frequently resolve shortly after reversal of heparinization.

• Paravalvular regurgitation is not uncommon and results from a combination of surgical technique and the condition of the native annulus. A heavily calcified annulus complicates the placement of a prosthetic valve and may require extensive surgical débridement and repair before placement. These variables may increase the occurrence and severity of paravalvular regurgitation.

• For prosthetic valves in the mitral and tricuspid positions, it may be very difficult to detect pathologic regurgitation on transthoracic imaging. If suspected, it is an indication for TEE imaging. With TEE, CF Doppler imaging of a prosthetic valve in the mitral position is optimal because the ultrasound beam has access to the chamber receiving the regurgitant flow without intervening acoustic shadowing from crossing the prosthesis.

• For prosthetic valves in the atrioventricular position, a nondiagnostic transthoracic study for regurgitation does not exclude that possibility. Transthoracic echocardiography has a low negative predictive value for prosthetic valve regurgitation.

Pulsed Wave and Continuous Wave Doppler

• PW and CW Doppler modes provide quantitative evaluation of the prosthetic valve. Assessments regularly performed include peak transvalvular velocity (V_max), velocity time integral (VTI), peak and mean transvalvular pressure gradients, calculation of prosthetic valve area, and measurement of a dimensionless index in stenotic valves.

• These assessments are based on basic principles of physics including

• The simplified Bernoulli equation, ΔP = 4 × (V₂ )², forms the basis of much of the quantitative analysis including subvalvular and valvular velocities and gradients.

• For sites in which flow velocity proximal to the site of interest is high (>1.4 m/s), the simplified Bernoulli equation is not applicable and the proximal velocity must be included:

• The angle of interrogation (i.e., the angle between the Doppler beam and blood flow) should be less than 20 degrees to allow acceptable accuracy of blood flow velocities.

• For lower velocity flows (i.e., no aliasing), PW Doppler can be employed. The aliasing velocity is, in part, determined by the distance of the area of interest from the ultrasound probe. For higher velocity flows (i.e., exceeds the aliasing velocity), CW Doppler should be employed to allow assessment of high velocity flows.

• As a general practice, CW Doppler is most commonly used to assess prosthetic valve velocities and pressure gradients to allow measurement of a wide range of velocities and to ensure that the maximal velocities (i.e., vena contracta) is measured.

• Conservation of mass/continuity equation

• This principle states that mass, flow, or volume (or stroke volume) measured at one site is equal to another provided that there are no intervening channels (inputs or outputs).

• The basis of this assumes that volume can be measured by the equation VTI × Area (πr²; r = radius of the site of interest). This equation assumes a circular and non-changing orifice.

• If the volume or mass can be measured at a reference site, and the VTI across the valve can be obtained, then the EOA of the valve can be calculated using the continuity equation:

• The peak velocity (V) may be substituted for the VTI.

• Although the peak velocities of VTI for the reference are typically obtained using PW Doppler to target the same site at which the radius is measured, the respective Doppler values of the prosthetic valve are obtained using CW Doppler in order to measure flows across the vena contracta.

• Once three of the four values are obtained, the fourth can be solved for

General Points

• Compared with a normal native valve, prosthetic valves have a smaller EOA. Antegrade velocities and pressure gradients across a normally functioning prosthetic valve are higher than a normal native valve.

• Smaller prosthetic valves may have hemodynamic profiles similar to that of mild stenosis for the given valve position (e.g., a 19 mm-prosthetic valve has an EOA ranging from 1.0-1.1 cm²).

• Clinical application of Doppler-derived pressure gradients across mechanical valves may not be straightforward because a number of variables contribute to its value

• Patient-prosthesis mismatch (PPM).

• Manufacturers publish data on the flow characteristics of each specific prosthetic valve and its various sizes. Published in vivo data vary more than in vitro data owing to variability in hemodynamic functions. Given the wide range of pressure gradients across any specific prosthetic valve, it may be best to determine the valve EOA or measure a dimensionless index across the valve and its outflow tract (described later).

• Doppler-derived peak and mean pressure gradients across bioprosthetic valves correlate closely with directly measured pressure gradients. For these valves, there is a single orifice.

• Doppler-derived pressure gradients across mechanical valves present a more complex clinical scenario. This has been best studied for the bileaflet valve where two hemicircular disks hinge open to form two larger semicircular lateral orifices and a smaller slitlike central orifice. Within the narrow central flow stream, higher blood velocities occur owing to local acceleration forces. Whether or not CW Doppler overestimates the transvalvular velocities by recording flow across the central smaller orifice is an issue. Theoretically, the pressure gradient across a narrower orifice of this valve will be identical to the peripheral ones because blood flow through the orifices is directly related to the orifice size.

• Utilizing pressure gradients across prosthetic valves as the sole indicator of functionality is limited because transvalvular gradients will vary directly with patient’s cardiac output. Therefore, when valve patency is in question, it is important to determine the EOA of the prosthetic valve.

• PPM refers to an implanted prosthetic valve whose EOA is small relative to the patient’s desired functional level. Implanted prosthetic valves have the unique possibility of functioning normally but still performing in a clinically detrimental manner through “PPM.”

• This has been measured by comparing the EOA with the patient’s body surface area (BSA) to obtain an indexed valve area: iEOA. The undersized valve’s EOA results in

• Excessive high-pressure gradients with the patient’s blood flow requirements.

• Decreased improvement of proximal chamber function or, in the case of aortic stenosis, a reduced regression of ventricular hypertrophy.

• Decreased improvement of functional capacity.

• Increased pressures, over time, in the chambers proximal to the prosthetic valve.

• Although indexing of EOA to a patient’s BSA may not be appropriate in morbidly obese patients, it must still be considered because the patient will still need to function with the same body mass. For similar BSAs, obese patients have lower cardiac output requirements because fat is a vessel-poor tissue.

• A recent study found that PPM did not correlate with adverse clinical outcomes in patients with a body mass index greater than 30 kg/m². PPM may not have clinical importance in the elderly (≥75 years old) or the smaller patient (≤1.7 m²).

• PPM can occur at any site at which prosthetic valves are implanted, but most clinical work has focused on prosthetic valves in the aortic position. Pressure gradients across prosthetic valves in the aortic position increase exponentially when the iEOA is 0.8 to 0.9 cm²/m² or less. Based on these clinical data, PPM is considered to be hemodynamically insignificant if the EOA is 0.85 cm²/m² or greater, moderate if the iEOA is between 0.65 and 0.85 cm²/m², and severe if iEOA is less than 0.65 cm²/m².

• The reported prevalence of moderate and severe PPM in aortic prosthetic valves varies considerably but should be deceasing as the surgical community gains awareness of the impact of PPM on clinical outcomes.

• PPM results in reduced short- and long-term survival, especially when associated with preexisting left ventricular dysfunction. The severity of the PPM also correlates with reduced patient survival.

• PPM is best avoided by the preimplantation calculation of a valve’s functional EOA against the patient’s BSA and the choice of an appropriate sized valve.

• PPM has been reported for prosthetic valves implanted in the mitral position. Limited clinical data suggest that the iEOA on mitral prostheses should be greater than 1.2 to 1.3 cm²/m² to avoid deleterious pressure gradients across the valve. PPM of mitral prosthetic valves has been reported to result in persistent pulmonary hypertension and reduced long-term survival.

Key Points

• The opening and closing of the mechanical valve disks or bioprosthetic cusps must be evaluated before decannulation so that abnormalities (see Cases on companion website) may be corrected before the patient leaves the operating room.

• Color Doppler in bioprosthetic valves often shows a small central jet of regurgitation; with mechanical prostheses, intravalvular washing jets are normally seen (see Cases on companion website).

• A small degree of paravalvular regurgitation, although abnormal, often resolves after the administration of protamine.

• PW and CF Doppler are used to assess transvalvular gradients. Although the accuracy in bioprosthetic valves seems intuitive, the complex flow characteristics of mechanical valves may be problematic.

• Evaluation of the functionality of a patient’s particular valvular prosthesis must be made in light of the manufacturer’s published data on the particular valves characteristics and, of course, on the patient’s clinical context.

• Valve gradients are often higher than expected in the immediate post-bypass period and usually relate to the high flow state that exists; however, extremely high valvular gradients are unusual and should prompt close echocardiographic examination using TEE or alternative techniques such as epicardial echocardiography.

Prosthetic Mitral Valve

Key Points

• The severity of regurgitant flow is quantitated in a fashion similar to that of native valves. Special attention must be paid to the seating of the valve and the presence of pannus, thrombus, calcification or vegetation, and coexistent prosthetic stenosis.

• PPM for mitral prostheses may be considered to exist with iEOA less than 1.25 cm²/m².

• The struts of bioprosthetic valves in the mitral position may rarely obstruct the LVOT. If the anterior mitral leaflet is redundant and preserved, outflow tract obstruction may occur with both mechanical and bioprosthetic valves.

Before evaluating the prosthetic MV, it is important to know what kind of valve was placed and to have some prior knowledge of how the images should appear. For all echocardiographic assessments, recording of the patient’s hemodynamic status improves the perspective at the time of evaluation.

Step-by-Step Examination (Figure 5-4)

• The 2D examination of the prosthetic MV is accomplished from a number of echocardiographic windows with particular emphasis on

• Midesophageal (ME) windows from 0 to 150 degrees including but not limited to the standard ME windows.

• TG views (0-30 degrees) are of limited value owing to its angle of interrogation; however, they may be useful to visualize the LVOT when shadowing artifact occurs during ME imaging (Figures 5-5 and 5-6)

• The CF, PW, and CW Doppler examinations of the prosthetic MV can be performed from the ME windows because the Doppler beam can be aligned with the direction of blood flow.

• Imaging from multiple windows will improve the assessment and ability to differentiate between abnormal forward and regurgitant jets.

Figure 5-4 Normal functioning bioprosthetic valve in the mitral position. Four ME 0-degree images of a bioprosthetic valve in the mitral position. A and C, 2D images of valve opening and closing. B and D, The respective figures with CF Doppler demonstrating normal forward flow and a normal central regurgitation jet during ventricular systole. LA, left atrium; LV, left ventricle; RA, right atrium.

Figure 5-5 Normal functioning bioprosthetic valve in the mitral position using other echocardiographic windows. Three images of a normal functioning bioprosthetic valve in the mitral position. A and B, TE images. C, TG image. Images include both 2D and CF Doppler imaging. B, The arrow points to the LVOT. It is evident from TE imaging that prosthetic valve-related artifacts (e.g., shadowing) affects the ability to image the LVOT. C, This can be avoided by using TG imaging.

Figure 5-6 Bioprosthetic valve in the mitral position using TG imaging. Two images obtained during TG imaging (0-degree plane) of a bioprosthetic valve in the mitral position. The valve image is seen on cross section. The arrows in A point to the struts of the valve and the arrow in B points to the LVOT. Asc Ao, ascending aorta.

The Echocardiographer Should

• Have knowledge of imaging differences between prosthetic valves

• Attempt to identify the sewing ring, the leaflets, disks, or other occluder mechanism (i.e., ball-cage).

Step 1: Two-Dimensional Examination (Figure 5-7; see also Figure 5-4)

The 2D examination involves visualization of the prosthetic valve and its surrounding tissues. The assessment should evaluate valve stability, leaflet motion, and note any extraneous mobile structures, the latter of which may represent suture materials, fractured calcium deposits, native chordae, or leaflet components.

• Imaging includes primarily TE but may also include TG imaging.

• The stability of the valve should be determined and whether or not the prosthesis is rocking. As a rule, the prosthetic valve should sit firmly within its surrounding tissue.

• The valve leaflets should be visualized and their mobility noted.

• For mechanical valves, imaging perpendicular to the leaflets will allow one to see the opening and closing by noting the leaflet edges. Imaging parallel to the valve leaflets is not likely to visualize the leaflet edges opening and closing. If the valve is bileaflet and placed anatomically, optimal imaging is done at or close to a four-chamber orientation; if placed antianatomically, optimal imaging is done at approximately 50 to 80 degrees.

Figure 5-7 Normal functional mechanical valve in the mitral position. Three ME 0-degree images, perpendicular to the valve leaflets, of a normal functioning bileaflet mechanical valve in the mitral position. A, The valve in the closed position as demonstrated by the arrows. B and C, The leaflets in the open position, the latter with CF Doppler imaging. Three orifices each demonstrated by an arrow are seen with the central orifice appearing smaller and characterized by a higher velocity.

Step 2: Doppler Examination (Figures 5-8 and 5-9)

The Doppler examination includes CF, PW, and CW examinations. The former allows both qualitative and quantitative evaluations including presence, direction, and width of normal and abnormal blood flows in and around the prosthetic valve.

• Both qualitative and quantitative imaging and assessments are achieved using TE windows.

Figure 5-8 Normal functional mechanical valve in the mitral position. Three ME images of a normal functional bileaflet mechanical valve in the mitral position. A and B, ME two-chamber images. C, A four-chamber image. A, The valve leaflets (arrows) in the closed position. CF Doppler shows normal regurgitant jets in two nearly orthogonal views (B and C). The regurgitant jets are normal for this valve.

Figure 5-9 Normal functional mechanical valve in the mitral position. The four ME images, with the 2D imaging plane to be parallel to the valve leaflets, displays a normal functioning bileaflet mechanical valve in the mitral position. A and B, The valve in the closed position during ventricular systole demonstrates two regurgitant jets (arrows) directed toward each other. C and D, The valve in the open position during ventricular diastole. D, Three forward moving jets with one central (arrow) and two peripheral ones moving through the three orifices of the bileaflet mechanical valve.

Regurgitant Flow: Normal versus Abnormal (Table 5-2; see also Figures 5-4, 5-8, and 5-9)

Prosthetic valves are association with “normal” or “expected” regurgitant jets. The former requires knowledge of normal regurgitant jets associated with each type of prosthesis. The assessment of abnormal prosthetic mitral regurgitation (MR) is similar to that of native valve assessment.

• Imaging includes both TE and TG windows.

• Abnormal regurgitant jets can either be paravalvular or within the annular ring. Jets greater than 3 mm in width (vena contracta) are more concerning and are less likely to regress. Smaller jets may also be considered abnormal, but in the absence of obvious pathology (e.g., mobile materials; valve instability), these do not tend to progress over time. Abnormal regurgitant flows can result from a number of causes:

• Paravalve (Figures 5-10 and 5-11)

• Endocarditis (Figures 5-12 and 5-13)

• Bioprosthetic valves: leaflet perforation/destruction.

• Mechanical valves: interference with valve opening/closure.

• Leaflet restriction/distortion (Figures 5-14 to 5-16)

• Suture.

• Thrombus.

• Pannus.

• Preserved valve apparatus interfering with closure of mechanical leaflets.

• Assessing severity of regurgitant flow is similar to that for native valve disease and includes both assessments of the prosthetic valve and secondary effects on other cardiac functions, the latter including dilation of the left ventricle and atrium, elevation of the pulmonary artery pressures, right heart dysfunction, and tricuspid regurgitation (TR).

• Valve structure and motion.

• Stable versus rocking.

• Extent or area of the regurgitant jet during CF Doppler.

• Jet area less than 4 cm² is normal; greater than 8 cm² is abnormal.

• Extent: Greater than 50% of the distance between valve and posterior atrial wall is significant.

• Eccentricity/centricity

• Eccentric jets are one grade more severe than centrally directed jets.

• Pulmonary venous flows (PW)

• Systolic dominance is normal; systolic blunting or reversal is abnormal.

• Flow convergence (proximal isovelocity surface area [PISA])

• None is normal; convergence on the left ventricle side is abnormal.

• Jet density and contour

• Faint/incomplete and parabolic are normal.

• Dense/complete and early peaking are abnormal.

TABLE 5-2 ASSESSING SEVERITY OF MITRAL REGURGITATION

Figure 5-10 Post MV replacement with a paravalvular leak. Two images of a bioprosthetic valve with a decreasing paravalvular leak (left to right). A, The jet (arrow) appears to be nonturbulent or of lower velocity. B, After administration of protamine, the resulting image shows a significant reduction in the regurgitant CF Doppler jet area (arrow).

Figure 5-11 Post MV replacement with a significant paravalvular leak (arrow). Large paravalvular turbulent jet directed toward the LA consistent with a paravalvular leak along the anterior aspect of the bioprosthetic valve.

Figure 5-12

Endocarditis of a bioprosthetic valve in the mitral position. The image demonstrates an echodense mobile mass on the bioprosthetic valve (arrow).

Figure 5-13 Endocarditis of a bioprosthetic valve in the mitral position with severe regurgitation. Four images demonstrate a mobile echodense mass attached to the prosthetic valve. A and B, The valve during diastole. C and D, Valve function during ventricular systole with severe MR (arrow). The arrows in A and C point at the vegetation.

Figure 5-14 Stuck/restricted bioprosthetic leaflets due to suture between two of the leaflets. These three figures demonstrate the restriction of the lateral leaflet of a bioprosthetic valve, which on reevaluation, was due to suture. A and B, Restriction in forward motion of the medial leaflet (two thinner arrows) and immobility of the lateral leaflet (thicker arrow). C, Mitral regurgitation during CF Doppler analysis.

Figure 5-15 Distortion and dysfunction of a large mitral prosthesis in a relatively small annulus. These three images were obtained from a patient in whom a relatively large bioprosthetic valve was placed in the mitral position. A, The prosthetic valve appears to sit on top of the annulus (arrow). B and C, Significant MR (arrows).

Figure 5-16 Thrombosis seen along the anterior medial leaflet of a mechanical MV. These four ME images demonstrate an echodense area on the mechanical valve consistent with thrombus. The stuck leaflet (arrow) during ventricular systole (A) and diastole (B). Ventricular systole (C) and ventricular diastole (D) show, with CF Doppler, that flow across the valve occurs only across the mobile mechanical leaflet.

Forward Flow: Normal vs. Abnormal (Table 5-3; see also Figures 5-4, 5-5, and 5-7 to 5-9)

Depending on the type of prosthesis, forward blood flow projects in different ways. Whereas bioprosthetic valves have a single forward flow, mechanical valves will have two (single leaflet) or three (bileaflet) forward projecting jets. The evaluation of forward flow consists of both qualitative (CF Doppler) and quantitative assessments (PW and CW Doppler), the latter consisting of transvalvular pressure gradients and calculation of prosthetic valve area.

• Doppler assessment is performed primarily from the TE windows (see Figures 5-5 and 5-7 to 5-9).

• Normal flows for prosthetic valves have been described and involve transvalvular velocities, pressure gradients, and valve areas. These data are largely determined during follow-up postoperative examination and may not be easily applied to intraoperative data, in which cardiac loading conditions and blood viscosity are significantly altered. Nevertheless, these data are often referred to and applied to the intraoperative examination.

• Normal EOA (or range) for each size and type of prosthesis has been reported. Suffice it to say, there are significant variations compared with that measured by the manufacturer.

• Although pressure gradients are a simpler measure, they are dependent on variables including valve area, cardiac output, blood viscosity, chamber pressures and compliances, and the angle of interrogation.

• PPM has been described for prosthetic MVs. PPM, for the MV, has been categorized as present or not, based on the iEOA (cm²/BSA [m²]). PPM for the MV may be considered present when the iEOA is less than 1.25 cm²/m².

• Degrees of mitral stenosis follow similar charts for native valve assessment. Significant mitral stenosis is considered when the mean transvalvular gradient is greater than 6 mm Hg, a peak gradient 12 mm Hg or greater, and/or a mitral valve area (MVA) less than 1.8 cm².

TABLE 5-3 ASSESSING SEVERITY OF MITRAL STENOSIS

Qualitative Assessment

Initial suspicion of obstruction to forward flow is seen during 2D and CF Doppler examination. Causes may include

• Thrombus (see Figure 5-16).

• Stuck leaflet (Figure 5-17; see also Figure 5-14).

• Distortion.

• Calcification.

Figure 5-17 Stuck mechanical leaflet in the mitral position. These four ME 0-degree images demonstrate a stuck mechanical leaflet (arrow). Images include 2D (A and B) and their respective CF Doppler (C and D) images during both ventricular systole (A and C) and ventricular diastole (B and D). D, During CF Doppler examination, ventricular inflow is seen across the one normally mobile leaflet (arrow).

Left Ventricular Outflow Obstruction after Mitral Surgery

An unusual type of obstruction is obstruction of the LVOT. This can result from attempts to retain native mitral tissues (leaflets or chordae) between the mitral annulus and the prosthetic ring. This is done to preserve ventricular geometry and reduce future negative remodeling. As an unusual consequence, these native tissues may become loose and lie in the LVOT, causing a dynamic and/or fixed obstruction to systolic outflow (Figure 5-18). Another cause of obstruction can result from placement of the struts of the bioprosthetic valve in the LVOT in a relatively small ventricle. Assessment of this complication may be difficult using ME imaging as a result of shadowing; therefore, TG imaging may be necessary (see Figures 5-5 and 5-6).

Figure 5-18 Example of a retained native anterior leaflet after valve replacement. Two TG images of the LVOT after MV replacement. During the prosthetic valve implantation, the anterior mitral leaflet was retained along the prosthetic valve annulus to prevent adverse ventricular remodeling. In both figures, the retained leaflet is identified by an arrow in the LVOT proximal to the aortic valve (AoV).

Quantitative Assessment

Doppler assessment of forward flow across the prosthetic MV is the standard to evaluate valve patency. A host of variables affect the Doppler data. These include changes in cardiac loading conditions and coexisting lesions that affect the forward flow across the MV or the pressure gradient between the left atrium and the left ventricle. These include, but are not limited to, AI (lowers pressure half time [PHT]), the presence of an interatrial septal defect (left to right flow lowers PHT), changes in atrial and/or ventricular compliances, and changes in heart rhythm.

• Peak velocity/gradient (CW). Although the presence of MR can affect the upper limit of normal, the following can be used as a general guide:

• Less than 1.8 m/s or less than 12 mm Hg is considered normal.

• 1.8 to 2.2 or 12 to 18 mm Hg is intermediate.

• 2.2 m/s or greater than 18 mm Hg is considered abnormal.

• Mean transvalvular gradient (CW)

• Less than 6 mm Hg is considered normal.

• 6 to 10 is an intermediate range that deserves further clarification.

• 10 mm Hg is considered abnormal.

• Doppler velocity index (DVI) may also be used for the MV

• VTI_MV/VTI_LVOT.

• Greater than 2.2 is considered abnormal.

• Less affected by changes in loading conditions.

Prosthetic Aortic Valve

Key Points

• Imaging of the AV must also include an assessment of the supra- and subvalvular tissues as well as the prosthetic valve.

• TG imaging may be necessary to detect abnormal pressure gradients, because it is difficult to achieve an adequate angle of insonation from the esophagus. Movement of mechanical leaflets may be best appreciated from this window. Always remember to consider epiaortic scanning.

• PPM may be most clinically relevant with valves in the aortic position. In general, mechanical valves give a larger EOA for a given ring diameter. If necessary, an aortic root enlargement procedure may be necessary.

Before evaluating a prosthetic AV, it is important to know the type of valve implanted and to have knowledge of how the characteristic 2D and CF Doppler images should appear. For all echocardiographic assessments, recording of the patient’s hemodynamic status improves the perspective at the time of evaluation.

Step-by-Step Examination

• Imaging of the prosthetic valve includes assessment of the supra- and subvalvular tissues as well as the prosthetic valve.

• The 2D examination of the prosthetic AV is accomplished from a number of echocardiographic windows with particular emphasis on

• ME four- or five-chamber view (0 degrees).

• ME short axis view (40-60 degrees) (Figures 5-19 and 5-20).

• ME long axis view (110-145 degrees) (Figure 5-21).

• Trans-gastric views (0-155 degrees) (Figures 5-22 and 5-23)

• The CF Doppler examination of the prosthetic aortic can be performed from each of the same windows as the 2D examination (Figure 5-24).

• Imaging from multiple windows will improve the assessment and ability to differentiate between abnormal forward and regurgitant jets.

• The PW and CW Doppler interrogation of the valve should be performed using TG imaging because the Doppler beam can be most easily aligned with the direction of blood flow.

• It is important to examine the LVOT and AV from multiple TG windows to obtain the maximum blood flow velocity. This would reduce the chance of underestimating peak subvalvular and transvalvular velocities.

Figure 5-19 Normal mechanical valve in the aortic position. Two TE images show a short axis image of the bileaflet mechanical valve in the aortic position during ventricular systole and diastole. During systole, the medial edges of each mechanical leaflet are seen. During diastole, the leaflets are closed and not seen because of the angle of interrogation (i.e., the leaflets are not in the imaging plane).

Figure 5-20 Normal mechanical aortic valve prosthesis with coronary flow in the left main coronary artery. Two TE images of the prosthetic AV in cross section show the left main coronary artery (A) with CF Doppler (B) as shown by the arrows.

Figure 5-21 Normal bioprosthetic valve in the aortic position. Three TE images of a normal functioning bioprosthetic valve in diastole (A), and systole (B and C). B, Note the shadowing (arrow) caused by the prosthetic valve.

Figure 5-22 Normal aortic valve prosthesis seen during TG imaging. Two TG images of the LVOT (arrows), LV, and LA. A, The arrows point toward the two closed mechanical leaflets. B, The arrows point toward the two leaflet edges/central orifice and the two lateral orifices in the open valve. These images were obtained with the transducer rotated to 100 degrees.

Figure 5-23 Normal bioprosthetic valve in the aortic position during TG imaging. Two TG images of a normal functioning bioprosthetic valve during diastole (A) and systole (B), the former showing ventricular inflow (arrow) and the latter showing ventricular outflow.

Figure 5-24 Normal aortic valve bioprosthesis with a normal regurgitant jet. Three TE images of the bioprosthetic valve during systole (A), diastole (B), and with CF Doppler demonstrate a small normal central jet of insufficiency in diastole. RA, right atrium.

The Echocardiographer Should

• Have knowledge of differences between prosthetic valves with (stented) or without (stentless) sewing rings. The latter (homografts, stentless valves) may not be distinguishable from native valves.

• Attempt to identify the sewing ring, the leaflets, disks, or other occluder mechanism (i.e., ball-cage).

• Recognize and appreciate the presence of perivalvular edema or hematoma that may be present immediately after valve surgery (Figures 5-25 and 5-26). This typically resolves over the first 24 to 48 hours after separation from cardiopulmonary bypass.

• For patients with stentless valves, this may result in a smaller EOA in the immediate postoperative period. For stentless valves, data show a significant increase in EOA over the first 3 to 6 months after placement.

• Recognize changes in prosthetic valves over time. This is more of an issue with stentless AVs during which the cloth edges are sutured to the native aortic annulus. If the edges are not sutured completely, they may appear in the outflow tract. Over time, these edges will flatten out and any obstruction will resolve or reduce significantly over time.

Figure 5-25 Normal homograft seen in the aortic position. Two TE images show a short axis view of the homograft valve in the aortic position during both ventricular diastole (A) and systole (B). Note the thickness of the paravalvular tissues (double arrow in A). This is the result of either edema or hematoma; it resolves over the following 24 hours to 3 to 6 months.

Figure 5-26 Normal homograft seen in the aortic position. Two TE images of a stentless AV in the short axis view seen during ventricular diastole (A) and systole (B).

Step 1: Two-Dimensional Examination

• Imaging includes both TE and TG imaging (see Figures 5-19 and 5-24).

• The stability of the valve should be determined and whether or not the prosthesis is rocking. As a rule, the prosthetic valve should sit firmly within its surrounding tissue without any qualitative evidence of rocking.

• The valve leaflets should be visualized and the mobility noted.

• Measurement of the LVOT diameter should be performed, from the ME long axis window, to allow assessment of valve area using the continuity equation.

• Supra- and subvalvular areas should also be interrogated.

• This is important for cases in which the LVOT was enlarged and/or when a homograft was placed.

• Subvalvular imaging is needed to assess for evidence of LVOT obstruction.

Step 2: Doppler Examination

• Although qualitative imaging includes both TE and TG windows, most of the quantitative assessment is best achieved from the TG windows where blood flow and the Doppler beam can be best aligned (Figure 5-27).

• Although qualitative assessments may suggest high velocities (i.e., abnormal) based on the presence of aliasing (turbulence) during CF Doppler examination, this may or may not indicate abnormal flow. Further quantitative analysis should be performed to clarify the flow. As a rule, prosthetic valves in the aortic position are associated with higher flow velocities than a normal native valve in the aortic position.

Figure 5-27 Quantitative assessment of the prosthetic aortic valve (AoV). Two ME images (A and B) and one obtained during TG imaging (C). A and B, Short axis views allow 2D planimetry to be performed (B). C, CW Doppler profile during TG imaging. This can be performed on either mechanical or bioprosthetic valves to allow quantitative assessment of flow velocities, pressure gradients, and calculation of the aortic valve area (AVA) using the continuity equation.

Regurgitant Flow: Normal versus Abnormal (Table 5-4)

Prosthetic valves are associated with “normal” or “expected” regurgitant jets. The former requires knowledge of normal regurgitant jets associated with each type of prosthesis. The assessment of abnormal prosthetic AV regurgitation parallels that of native valve assessment.

• Imaging includes both TE and TG windows.

• Normal regurgitant jets, assessed with vena contracta, are less than 3 mm in width.

• Bioprosthetic valves typically display a central regurgitant jet.

• Mechanical leaflets display a variety of regurgitant jets depending on the valve type.

• A bileaflet mechanical valve will usually have two regurgitant jets directed centrally.

• A single leaflet valve (or tilting disk valve) will have a regurgitant jet directed away from the sewing ring from the edge of the major orifice.

• A ball-cage valve will have small circumferential jets around the occluder.

• Homografts should NOT have any regurgitant jets; however, some may be seen depending on the native valve function before excision and preparation.

• Assessing severity of regurgitant flow is similar to that for native valve disease

• Valve structure and motion.

• Left ventricular size (depends on acuity)

• Doppler—qualitative to semiquantitative.

• Jet width (% of LVOT diameter)

• Less than 25% is mild; 25% to 50% is moderate; greater than 50% is severe.

• Jet density

• Faint/incomplete is within normal limits.

• Dense/complete is considered abnormal.

• PHT (ms)

• Greater than 500 ms is mild; 200 to 500 is intermediate; less than 200 is severe.

• Diastolic flow reversal in descending aorta.

• Absent is mild; intermediate is moderate; prominent is severe.

• Doppler—quantitative (continuity equation or PISA)

• Regurgitant volume (mL/beat)

• Less than 30 is mild; 30 to 59 is moderate; greater than 60 is severe.

• Regurgitant fraction (%)

• Less than 30 is mild; 30 to 50 is moderate; greater than 50 is severe.

TABLE 5-4 ASSESSING SEVERITY OF AORTIC VALVE REGURGITATION

Figure 5-28 Paravalvular abscess after AV replacement. Four TE views of a paravalvular abscess surrounding a previously placed bioprosthesis. Short axis (A) and long axis (B) views of the valve and abscess (arrow). C and D, CF Doppler images of the valve apparatus during systole and diastole, the latter demonstrating an eccentric jet of AI (arrow).

Figure 5-29 Endocarditis of a bioprosthetic AV. Two TE images of a bioprosthetic valve in the short axis window during systole and diastole. Left, The arrows point toward a small mass on the noncoronary cusp and a thickening of the left coronary cusp.

Figure 5-30 Dehiscence of an aortic homograft. Two TE long axis 2D views the LVOT and a dehisced homograft (arrows) seen during systole (A) and diastole (B).

Figure 5-31 Thrombosis of a mechanical valve in the aortic position. Two TE images long axis view of the LVOT (A) and AV (B) show a mass along the posterior area of the prosthesis (arrow). This was associated with an immobile leaflet and AV stenosis. The calculated AVA was 0.7 cm² with a mean gradient of approximately 50 mm Hg.

Figure 5-32 Stuck mechanical leaflet in the aortic position. Four images demonstrate restricted motion of one mechanical leaflet of the prosthetic AV. A and B, Short axis images of the mechanical valve. A, The two leaflet edges (arrows) are seen as also noted in Figure 5-19. However, in B, a leaflet edge (arrow) is still seen during diastole. C and D, TG imaging with the transducer rotated to 160 degrees. C, A single leaflet open (single arrow) while the other leaflet (double arrow) is stuck in an intermediate position. D, The mobile leaflet is shown to be closed and the stuck leaflet to be unchanged.

Forward Flow: Normal versus Abnormal (Table 5-5)

Depending on the type of prosthesis, forward blood flow projects in different ways. Whereas bioprosthetic valves have a single forward flow, mechanical valves will have two (single leaflet valve) or three (bileaflet valve) forward projecting jets. The evaluation of forward flow consists of both qualitative (CF Doppler) and quantitative assessments (PW and CW Doppler), the latter consisting of transvalvular flow velocities and gradients, and calculation of the effective orifice area of the prosthetic valve.

• Although Doppler imaging from ME windows could add to the qualitative assessment, quantitative analysis primarily involves TG imaging.

• Normal forward flows for prosthetic valves have been described and the data include transvalvular velocities, pressure gradients, and valve areas.

• The normal contour of the flow velocity profile is an early peaking and triangular shape. With increasing narrowing/stenosis, the contour peaks later and the shape becomes more round. Along with this change in shape is a respective change in the acceleration time from a relatively short period to the peak velocity (≤80 ms) to a more prolonged acceleration phase (>100 ms).

• Normal EOA (or range) for each size and type of prosthesis has been reported. Suffice it to say, there are significant variations compared with that measured by the manufacturer.

• These data are largely determined during follow-up postoperative examination and may not be easily applied to intraoperative data, in which cardiac loading conditions and blood viscosity are significantly altered. Nevertheless, data regarding expected EOA have been applied to the intraoperative examination.

• The DVI is a dimensionless index in which the peak subvalvular velocity (LVOT) is divided by the peak transvalvular velocity. Alternatively VTI may be used instead of peak velocities.

• PPM is a term used to describe the mismatch between the EOA of the prosthetic valve and the patient’s BSA (m²). The EOA is indexed to the patient’s BSA to calculate the iEOA.

• PPM has been categorized as mild, moderate, and severe based on the iEOA (cm²/BSA [m²]). For these divisions, the iEOA is 0.85 to 1.00 cm²/m²; 0.65 to 0.85 cm²/m²; and less than 0.65 cm²/m², respectively.

• PPM is associated with reduced short- and long-term survival, especially when associated with preexisting left ventricular dysfunction.

• The clinical impact is more consistently reported for severe PPM (i.e., <0.65 cm²/m²).

• PPM is best avoided by the pre-implantation calculation of a valve’s functional EOA against the patient’s BSA and the choice of an appropriate sized valve.

• PPM has less clinical impact on the elderly (>75 yr) and/or for smaller BSA (<1.75 m²).

TABLE 5-5 ASSESSING SEVERITY OF AORTIC VALVE STENOSIS

Figure 5-33 Before and after imaging of a stentless valve in the aortic position. Four TE images from the long axis view show a complication of the stentless AV. A and B, The arrows point to the cloth edges, which lay in the outflow tract causing functional stenosis. C and D, Follow-up at 6 months shows the cloth edges (arrows) to have flattened into the LVOT tissues and associated with a reduction in transvalvular pressures and an increase in the calculated EOA. Ao, aorta.

Quantitative Assessment

Doppler assessment of forward flow across the prosthetic AV is the standard to evaluate valve patency. However, a host of variables affect the Doppler data. These include changes in cardiac loading conditions, coexisting lesions that affect forward flow across the valve, or the pressure gradient between the left ventricle and ascending aorta. These include, but are not limited to, left ventricular failure (decreased forward flow), AI (increased forward flow), MR (decrease forward flow), and atrial arrhythmias (reduced LV preload) (Figures 5-34 and 5-35; see also Figure 5-27).

• Peak velocity/gradient

• Greater than 4 m/s is consistent with significant stenosis.

• Less than 2 m/s is consistent with insignificant stenosis in absence of low cardiac output (forward flow across the AV).

• Acceleration time is the time from onset of outflow to peak velocity

• The greater this value the more significant the stenosis

• Normally less than 100 ms.

• DVI

• VTI (or V)_LVOT/VTI (or V)_AV.

• A DVI less than 0.3 is considered significant stenosis.

• EOA—continuity equation

• EOA_AV = cross-sectional area (CSA)_LVOT × VTI_LVOT/VTI_AV.

• Severity of stenosis may follow definitions put forth for native valve stenosis.

• Valve areas may be reported directly (EOA) or after being indexed for BSA (iEOA).

Figure 5-34 Stuck mechanical leaflet. These three TG images allow both qualitative and quantitative assessment of the same patient in Figure 5-32. A, Forward flow (arrow) is seen across the mobile leaflet. B, An abnormal regurgitant jet (arrow) coming from the stuck leaflet in the intermediate position. C, Significant AV stenosis with an AVA of 0.6 cm².

Figure 5-35 Normal bioprosthetic valve in the tricuspid position. Three ME images show a normal-appearing bioprosthetic valve (arrow) in the tricuspid position. A, The ME window. B and C, The right ventricular inflow view.

Prosthetic Tricuspid Valve

Key Points

• Right-sided valve prostheses are less common than left-sided valve prostheses.

• Bioprosthetic valves are more commonly placed.

• Abnormalities of the TV necessitating valve replacement are most commonly the result of left-sided disease.

• Pulmonic valve replacement is most often done in the setting of congenital heart disease.

Before evaluating the prosthetic TV, it is important to know what kind of valve was placed and to have some prior knowledge of how the images should appear.

Step-by-Step Examination

• The CF, PW, and CW Doppler examinations of the prosthetic TV can be performed from primarily the ME windows because the Doppler beam can be most easily aligned with the direction of blood flow.

• Imaging from multiple windows will increase the likelihood of detecting abnormal forward and regurgitant jets.

Figure 5-36 Normal mechanical valve in the tricuspid position. Three ME right ventricular inflow images show a normal-appearing mechanical valve (arrows) in the tricuspid position. A, During systole. B, During diastole. C, A normal CD flow pattern.

Figure 5-37 Normal mechanical valve in the tricuspid position during TG imaging. Two figures show TG imaging of a normal functional mechanical valve in the tricuspid position. A, The arrows show the mechanical leaflets during ventricular systole (i.e., closed). B, The arrows show the valve during ventricular diastole (i.e., open).

The Echocardiographer Should

• Attempt to identify the sewing ring, the leaflets, and disks.

• Have knowledge and imaging differences between prosthetic valves.

Step 1: Two-Dimensional Examination

The 2D examination involves visualization of the prosthetic valve and its surrounding tissues. The assessment should evaluate valve stability, leaflet motion, and any extraneous mobile structures that may represent suture materials.

• Imaging includes TE and TG imaging.

• The stability of the valve should be determined and whether or not the prosthesis is rocking. As a rule, the prosthetic valve should sit firmly within its surrounding tissue.

• Assessments of the right atrium and ventricle should make note of function and size. In considering the impact of the left heart on the right, assessment of the left heart structures should also be done.

Step 2: Doppler Examination

The Doppler examination includes CF, PW, and CW examinations. The former allows both qualitative and quantitative evaluations including occurrence, direction, and width of normal and abnormal blood flows in and around the prosthetic valve.

• Whereas qualitative imaging includes both TE and TG windows, most of the quantitative assessment is best achieved from the TE windows in which blood flow and the Doppler beam can be best aligned.

• Although qualitative assessments may be turbulent based on CF Doppler aliasing, this may or may not indicate abnormal flow. Further quantitative analysis should be performed to clarify the flow.

• Additional quantitative Doppler may include PW analysis of the caval flows looking for systolic blunting and/or reversal of flow. Assessment of the peak velocity of the tricuspid regurgitant jet allows one to estimate the right ventricular systolic pressure using the Bernoulli equation. This can be used to estimate the pulmonary artery systolic pressure.

Regurgitant Flow: Normal versus Abnormal (Table 5-6)

Prosthetic valves are associated with “normal” or “expected” regurgitant jets. Differentiating between normal and abnormal jets includes both echocardiographic and clinical assessments. The former requires knowledge of normal regurgitant jets associated with each type of prosthesis. The assessment of abnormal prosthetic TR parallels that of native valve assessment and should be distinct from normal regurgitant flows. On the whole, eccentric jets are considered abnormal.

• Imaging includes both TE and TG windows.

• Acceptable regurgitant jets are less than 3 mm.

• Bioprosthetic valves typically display a central regurgitant jet.

• Mechanical leaflets display a variety of regurgitant jets depending on the valve type.

• A bileaflet mechanical valve will usually have two regurgitant jets directed centrally.

• A single leaflet mechanical valve (or tilting disk valve) will have normal washing jets moving away from the major axis of the disk.

• Assessing severity of regurgitant flow is similar to that for native valve disease and includes assessments of both the prosthetic valve and secondary effects on other cardiac functions, the latter including the left ventricle, atrium, tricuspid artery pressures, and secondary right heart dysfunctions.

• Valve structure and motion.

• Stable versus rocking.

• Right atrium and ventricle.

• Whereas dilation and dysfunction are consistent with significant TR, it is possible that the chamber adaptations have not yet occurred.

• Inferior (or superior) vena cava size.

• Inferior vena cava (IVC) diameter less than 1.5 cm with respiratory variation is considered normal.

• IVC diameter between 1.5 and 2.5 is intermediate.

• IVC diameter greater than 2.5 cm with and without respiratory variation is abnormal.

• Extent of regurgitant jet

• Jet area less than 4 cm² is normal; greater than 8 cm² is abnormal.

• Hepatic or caval venous flows

• Systolic dominance is normal; systolic blunting or reversal is abnormal.

• Flow convergence (PISA)

• None is normal; convergence on the right ventricle side is abnormal.

• Jet density and contour

• Faint/incomplete and parabolic is normal.

• Dense/complete and early peaking is abnormal.

• Vena contracta (cm)

• Less than 0.3 cm is considered mild.

• 0.3 to 0.7 cm is moderate.

• Greater than 0.7 is severe.

TABLE 5-6 ASSESSING PROSTHETIC TRICUSPID VALVE REGURGITATION

Figure 5-38 Stuck mechanical leaflet in the tricuspid position. These two ME 0-degree images show a stuck mechanical leaflet during both ventricular systole (A) and diastole (B). The mechanical leaflet closer to the septum appears to be moving. The arrows point to each mechanical leaflet. A shows both leaflets in the closed position, and B shows only one leaflet in the open position.

Forward Flow: Normal versus Abnormal (Table 5-7)

Depending on the type of prosthesis, forward blood flow projects in different ways. Whereas bioprosthetic valves have a single forward flow, mechanical valves will have two or three forward projecting jets. The evaluation of forward flow consists of both qualitative (CF Doppler) and quantitative assessments (PW and CW Doppler), the latter consisting of transvalvular pressure gradients and calculation of prosthetic valve area.

• Doppler assessment is performed primarily from the TE windows.

TABLE 5-7 ASSESSING PROSTHETIC TRICUSPID VALVE STENOSIS

Parameter	Normal	Abnormal
Peak velocity (m/s) (CWD)	≤1.7	>1.7
Mean gradient (mm Hg) (CWD)	<5-6	>7
Pressure half time (ms) (CWD)	<200	>230
Size of vena cava (cm)	≤1.5 with respiratory variation	>2.0 without respiratory variation