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Echocardiographic Assessment of Prosthetic Heart Valves Lori A. Blauwet, Fletcher A. Miller Jr. Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA
A R T I C LE I N FO
AB S T R A C T
Keywords:
Valvular heart disease is a global health problem. It is estimated that more than 280,000
Echocardiography
prosthetic heart valves are implanted worldwide each year. As the world's population is
Doppler
aging, the incidence of prosthetic heart valve implantation and the prevalence of prosthetic
Prosthesis
heart valves continue to increase. Assessing heart valve prosthesis function remains
Heart valves
challenging, as prosthesis malfunction is unpredictable but not uncommon. Transthoracic two-dimensional and Doppler echocardiography is the preferred method for assessing prosthetic valve function. Clinically useful Doppler-derived measures for assessing prosthetic valve hemodynamic profiles have been reported for aortic, mitral, and tricuspid valve prostheses, but echocardiographic data regarding pulmonary valve prostheses remain limited. Complete prosthetic valve evaluation by transthoracic echocardiography (TTE) is sometimes challenging due to acoustic shadowing and artifacts. In these cases, further imaging with transesophageal echocardiography, fluoroscopy and/or gated CT may be warranted, particularly if prosthetic valve dysfunction is suspected. Being able to differentiate pathologic versus functional obstruction of an individual prosthesis is extremely important, as this distinction affects management decisions. Transprosthetic and periprosthetic regurgitation may be difficult to visualize on TTE, so careful review of Doppler-derived data combined with a high index of suspicion is warranted, particularly in symptomatic patients. A baseline TTE soon after valve implantation is indicated in order to “fingerprint” the prosthesis hemodynamic profile. It remains unclear how frequently serial imaging should be performed in order to assess prosthetic valve function, as this issue has not been systematically studied. © 2014 Elsevier Inc. All rights reserved.
Echocardiography has become the primary tool for assessment of patients with prosthetic heart valves. Comprehensive guidelines for evaluation of prosthetic heart valves by echocardiography have been published by the American
Society of Echocardiography (ASE) and the European Association of Echocardiography (EAE).1 Readers are strongly encouraged to familiarize themselves with these guidelines. This manuscript will primarily focus on transthoracic
Statement of Conflict of Interest: see page 109. Address reprint requests to Lori A. Blauwet, MD, and Fletcher A. Miller Jr, MD, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. E-mail addresses: [email protected] (L.A. Blauwet), [email protected] (F.A. Miller). http://dx.doi.org/10.1016/j.pcad.2014.05.001 0033-0620/© 2014 Elsevier Inc. All rights reserved.
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Abbreviations and Acronyms 2D = 2-dimensional AHA/ACC = American Heart Association/American College of Cardiology
echocardiography (TTE) assessment of prosthetic heart valves that have been implanted by standard surgical techniques.
AT = acceleration time ASE = American Society of Echocardiography AVP = aortic valve prosthesis
General considerations Clinical data
BSA = body surface area CW = continuous wave E velocity = peak early mitral diastolic velocity EAE = European Association of Echocardiography EOA = effective orifice area ERO = effective regurgitant orifice iEOA = indexed effective orifice area LV = left ventricular LVEF = left ventricular ejection fraction MG = mean gradient MVP = mitral valve prosthesis PHT = pressure half-time PPM = prosthesis–patient mismatch PVP = pulmonary valve prosthesis SV = stroke volume SVI = stroke volume index TEE = transesophageal echocardiography TTE = transthoracic echocardiography TVI = time velocity integral TVIAVP = time velocity integral of the aortic valve prosthesis TVILVOT = time velocity integral of the left ventricular outflow tract TVIMVP = time velocity integral of the mitral valve prosthesis TVITVP = time velocity integral of the mitral valve prosthesis TVI ratio = ratio of the time velocity integral of the prosthesis to the time velocity integral of the left ventricular outflow tract TVP = tricuspid valve prosthesis
Assessment and documentation of clinical data including patient height, weight, body surface area, blood pressure and heart rate are essential. Knowing patient size is particularly important for determining whether prosthesis– patient mismatch (PPM) is present, while knowing a patient's blood pressure at the time of the echocardiographic examination is important due to the effect of blood pressure on determining the severity of certain prosthetic valve lesions, particularly mitral valve transprosthetic/ periprosthetic regurgitation. Recording the heart rate at the time of Doppler assessment is particularly important when assessing mitral and tricuspid valve prostheses because mean gradient (MG) depends on the diastolic filling time. Noting operative data including prosthesis type, prosthesis size, date of implantation and any associated operative procedures such aortic root enlargement, is crucial for accurate interpretation of 2-dimensional (2-D) and Doppler
findings, as hemodynamic profiles differ among various prosthesis types and sizes.
2-Dimensional echocardiography Prostheses should be imaged from multiple views with particular attention paid to the motion of the occluders/ leaflets, the presence or absence of echo densities attached to the sewing ring, cage, struts and/or occluders/leaflets, and the integrity of the sewing ring/annular interface. Observing abnormal rocking motion of the prosthesis suggests dehiscence. Magnification of real-time 2-D images is often necessary for optimal visualization.
Doppler echocardiography Prosthetic valve assessment with color flow, pulsed wave (PW), and continuous wave (CW) Doppler imaging should be performed using similar principles and techniques used for assessment of native valves, including interrogation of the prosthesis from multiple windows and proper alignment of the Doppler beam with flow direction. Hemodynamic parameters of aortic, mitral, tricuspid and pulmonary valve prostheses that should be assessed during TTE are listed in Table 1. One key factor to consider during interrogation of prosthetic valves is that Doppler-derived parameters vary with cycle length. For aortic, mitral and pulmonary valve prostheses, Doppler measurements from three consecutive cardiac cycles should be averaged if the patient is in sinus rhythm and a minimum of five cardiac cycles averaged if the patient is in atrial fibrillation or another irregular rhythm. For patients with irregular rhythms, attempts should be made to use periods of physiologic heart rate and to match five cardiac cycle lengths for each Doppler parameter assessed. For patients with tricuspid valve prostheses (TVPs), it is important to remember that Doppler-derived hemodynamic Table 1 – Complete Doppler assessment of prosthetic valves. Aortic Valve Prostheses
Mitral Valve Prostheses
Tricuspid Valve Prostheses
Pulmonary Valve Prostheses
Peak velocity Mean gradient Acceleration time Dimensionless index Effective orifice area Indexed effective orifice area Regurgitation: presence, location, severity
E velocity Mean gradient Pressure halftime TVI ratio
E velocity Mean gradient Pressure halftime TVI ratio
Peak velocity Peak gradient Mean gradient
Effective orifice area Indexed effective orifice area Regurgitation: presence, location, severity
Effective orifice area Indexed effective orifice area Regurgitation: presence, location, severity
Regurgitation: presence, location, severity
Abbreviations: TVI ratio, ratio of the time velocity integral of the mitral valve prosthesis to the time velocity integral of the left ventricular outflow tract.
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parameters vary not only with cycle length, but also with respiration. Averaging a minimum of 3–5 consecutive cardiac cycles or obtaining measurements in midexpiratory apnea is recommended for all patients with TVPs.1–3
Transprosthetic/periprosthetic regurgitation Regurgitant jets may travel through the prosthesis (transprosthetic regurgitation) or around the sewing ring (periprosthetic regurgitation). Central jets are most often transprosthetic. Jets that originate anteriorly, posteriorly, medially or laterally may be either transprosthetic or periprosthetic. If the regurgitant color flow jet can be clearly identified outside the ring, then the diagnosis of periprosthetic regurgitation can be made with confidence. On occasion, particularly with tissue prostheses, transprosthetic jets may occur very close to the inner edge of the sewing ring and may be difficult to distinguish from periprosthetic regurgitation. Some transprosthetic jets are normal. For instance, it is relatively common to see a trivial central regurgitant jet with normal tissue prostheses. Mechanical prostheses are designed such that a small amount of transprosthetic regurgitation occurs during normal prosthesis function. Currently, the most commonly encountered mechanical valve prostheses are designed with a bileaflet occluding mechanism. For these valves, two small “washing jets” travel between the inner edge of the sewing ring and the outer edge of the leaflets. One jet originates near the inner border of the anterior sewing ring and the second jet originates near the inner border of the posterior sewing ring. Theoretically, these jets help to prevent thrombus formation in the bileaflet pivot slots, which are on the inner part of the circular housing. It is important that physicians interpreting echocardiography studies of prosthetic valves are familiar with the appearance of these jets so that the presence of these normal regurgitant jets does not lead to an erroneous interpretation of pathologic regurgitation.
Flow affects on Doppler-derived hemodynamic parameters Not all dysfunctional prostheses have a high MG, so MG should not be the sole parameter considered when assessing prosthetic valves. In low output states, many of the Dopplerderived hemodynamic parameters may be normal or only mildly abnormal even when a prosthesis is severely dysfunctional. In these cases, a high degree of suspicion and careful evaluation are warranted in order to accurately ascertain whether or not a particular prosthesis is dysfunctional. As a corollary, a high MG does not necessary indicate prosthetic valve dysfunction. Aortic valve prosthesis (AVP) peak velocity and mean gradient may be elevated due to pathologic obstruction or regurgitation, but may also be elevated due to “functional obstruction,” i.e., prosthesis– patient mismatch (PPM) or pressure recovery phenomenon, or a high flow state. Elevated mitral valve prosthesis (MVP) and tricuspid valve prosthesis (TVP) E velocity and MG may be due to pathological obstruction or regurgitation, but may also be due to PPM or a high flow state secondary to tachycardia, anemia, hyperthyroidism, arteriovenous fistula or malformations, or severe renal or hepatic disease.
Timing of echocardiographic examinations Patients with newly implanted valves should have a full TTE study, including comprehensive Doppler assessment, to “fingerprint” the prosthesis as a baseline for future followup. According to the recent American Heart Association/ American College of Cardiology (AHA/ACC) guidelines on the management of patients with valvular heart disease, obtaining a baseline TTE is a class I recommendation (Level of Evidence: C).4 The AHA/ACC guidelines recommend that the initial TTE be obtained 6 weeks to 3 months after valve implantation. The practice at our institution is to “fingerprint” the prosthesis by performing postoperative TTE on patients who have undergone valve replacement prior to hospital discharge. We have shown that there are no significant differences between bileaflet mechanical MVP Dopplerderived hemodynamic profiles obtained in the early postoperative period and profiles obtained up to 13 months after implantation,5,6 so performing a postoperative TTE at any time between several days to several weeks after surgical implantation when the patient is hemodynamically stable should be acceptable, at least for these types of prostheses. Echocardiography is an essential component of the assessment of any patient when prosthetic valve dysfunction is a clinical concern. Current AHA/ACC guidelines state that repeat TTE is recommended in patients with prosthetic heart valves if there is a change in clinical signs or symptoms suggesting valve dysfunction (class I; Level of Evidence: C) and that TEE is recommended when clinical signs or symptoms suggest prosthetic valve dysfunction (class I; Level of Evidence: C).4 There is lack of consensus regarding timing of echocardiographic follow-up for asymptomatic patients with prosthetic heart valves, largely due to lack of evidence. Current ACC/AHA guidelines on the management of patients with valvular heart disease state that “No further echocardiographic testing is required after the initial postoperative evaluation in patients with mechanical valves who are stable and who have no symptoms or clinical evidence of prosthetic valve or ventricular dysfunction or dysfunction of other heart valves.”4 This statement is given neither a classification of recommendation nor a level of evidence to support the statement. Regarding bioprosthetic valves, the current ACC/AHA guidelines recommend that an “annual TTE is reasonable in patients with a bioprosthetic valve after the first 10 years, even in the absence of a change in clinical status” (class IIa; Level of Evidence: C).4 Knowledge of prosthesis type and size and baseline echocardiographic parameters, as well as comparison with serial echocardiographic studies, is tremendously helpful in determining whether a particular prosthesis has normal versus abnormal function. During follow-up TTE examinations, observing changes in any of the pertinent Doppler-derived prosthetic parameters compared to previous echocardiographic examinations may indicate possible prosthetic valve dysfunction.
Indications for use of additional imaging modalities Occluder motion of mechanical valve prostheses may be difficult to visualize by 2-D imaging during TTE due to artifact and/or acoustic shadowing; in these cases, transesophageal
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echocardiography (TEE), fluoroscopy or gated CT imaging may be warranted, particularly when prosthetic valve dysfunction is suspected. Three-dimensional (3-D) assessment of the prosthesis during TEE examination and/or 3-D reconstruction of the prosthesis on CT imaging may be especially helpful. Clinically significant transprosthetic or periprosthetic regurgitation may be difficult to visualize on TTE imaging due to acoustic shadowing, particularly in patients with mechanical MVPs. If the Doppler-derived hemodynamic profile obtained by TTE imaging suggests moderate or more severe regurgitation despite little to no regurgitation visualized by Doppler color flow imaging, TEE imaging is warranted, particularly if the patient is symptomatic. Real time 3-D color flow imaging may be particularly helpful for determining the exact location and size of regurgitant orifices and may also facilitate the quantitation of regurgitation.
Evaluation of aortic valve prostheses 2-D echocardiography Every attempt should be made to image all portions of the AVP in both short and long axis views during TTE imaging. For tissue AVPs, this involves imaging of the sewing ring, cusps and stents (if present). For mechanical AVPs, the sewing ring can almost always be imaged, while it is more difficult to image the occluder(s), particularly when dealing with small AVPs. For larger bileaflet mechanical AVPs, it is often possible to image the occluders in long axis and/or short axis to verify that they are opening fully.
Doppler echocardiography The major potential pitfall for Doppler echocardiography is improper alignment of the Doppler beam with the jet being interrogated. For this reason, Doppler evaluation for AVPs must be performed from multiple transducer positions, including apical and para-apical, right parasternal (with the patient in right lateral decubitus position), right supraclavicular and suprasternal. The largest CW Doppler profiles are traced to obtain the prosthetic valve MG, peak velocity, and the time velocity integral (TVI). The position yielding the highest peak velocity and MG should be recorded in the report in order to facilitate future studies for the same patient. The continuity method is used to calculate the AVP effective orifice area (EOA): AVP EOA equals left ventricular (LV) stroke volume (SV) divided by the AVP TVI (TVIAVP). The LV SV is calculated as the product of the LVOT area and the TVI of flow in the LVOT (TVILVOT). For the vast majority of patients with AVPs, the LVOT diameter can be measured, and it is this measurement that should be used for SV calculation. In a minority of cases, in which landmarks for LVOT diameter measurement may be uncertain, AVP size can be used as a surrogate for the LVOT diameter. The LVOT diameter measurement is made from a parasternal long axis zoom view of the LVOT and aortic root. The image is frozen in peak systole and the LVOT diameter is measured by placing one caliper anteriorly at the junction of
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the ventricular septum and the anterior portion of the sewing ring and the second caliper at the junction of the posterior sewing ring and the base of the anterior mitral leaflet. The velocity profile for the LVOT is obtained from an apical long axis view. As for patients with native aortic valve stenosis, it important to recognize that there is a zone of flow convergence in the LVOT just proximal to the AVP. The continuity method requires that the velocity utilized for the SV calculation is the spatial mean velocity, which is obtained by moving the sample volume 0.5 to 1.0 cm away from the prosthesis sewing ring toward the LV apex. Assuming circular geometry of the LVOT at the level of the ventricular surface of the AVP sewing ring, the LVOT area is calculated as LVOT diameter squared times 0.785. Since measurement of the LVOT diameter and TVILVOT both have potential pitfalls, it is important to verify that the calculated SV makes clinical sense. Calculation of the LV stroke volume index (SVI) and checking it against LV size and left ventricular ejection fraction (LVEF) are recommended. Using the SVI instead of the SV facilitates this comparison, since body surface area (BSA) is taken into account. In most cases, patients with normal LV size and LVEF will have a normal SVI. If the measured SVI seems too large or too small for a particular patient, additional imaging should be obtained to reassess the LVOT diameter and/ or TVILVOT. The TVIAVP that is used to calculate AVP EOA is determined at the same time that the AVP peak velocity and MG are measured. Once a reasonable SVI has been obtained, the unindexed SV can be divided by the TVIAVP to determine the AVP EOA. Effective orifice area should be compared to the AVP MG for concordance. For instance, if the AVP EOA is ≤ 0.6 cm2, the MG will usually be ≥ 50 mmHg. If the AVP EOA is ≤ 0.6 cm2 and the MG is significantly < 50 mmHg, a reason for this discordance must be determined. Possible explanations for such a discordance include small left ventricular cavity, decreased LVEF, altered myocardial systolic function (decreased global longitudinal systolic strain), increased global hemodynamic load (valvuloarterial impedence), severe mitral and/or tricuspid regurgitation and inaccurate measurement of LVOT diameter and/or TVILVOT. If there is no pathophysiologic explanation, it is likely that either the LVOT diameter measurement was too small or the sample volume position for obtaining the LVOT velocity profile was too far from the AVP sewing ring. In this case, repeat imaging and Doppler evaluation should occur prior to generation of the final report. If an unexplained discrepancy persists, this should be highlighted in the final report.
Pressure recovery When blood accelerates through an AVP, the lowest pressure and highest velocity beyond the prosthesis occur at the vena contracta. This is typically located within a few millimeters of the prosthesis outflow orifice. As blood moves further into the aorta, the pressure recovers with a corresponding decrease in velocity. This means that the pressure gradient, determined by subtracting the aortic pressure from the LV pressure, may differ depending on the distance of the aortic pressure measurement from the vena contracta. The potential importance of this phenomenon for hemodynamic assessment of AVPs was first elucidated via in vitro
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experiments carried out by Baumgartner et al.7 Different types and sizes of mechanical and tissue prostheses were placed in position between an artificial LV and an artificial aorta. For each experiment, LV pressure was measured by a catheter that was positioned in the artificial LV. A second catheter was pulled from the LV through the prosthesis into the artificial aorta. Aortic pressure was measured immediately adjacent to the aortic side of the prosthesis and at multiple distances beyond this. For tissue AVPs and for larger mechanical AVPs, the pressure measured closest to the aortic side of the prosthesis was not significantly different from the pressures measured with the tip of the aortic catheter moved more distally into the aorta. For 19and 21-mm bileaflet mechanical AVPs, however, the pressure measured 3 to 5 mm beyond the aortic side of the prosthesis AVP was significantly lower than the pressure measured 10 mm and more beyond the prosthesis. Therefore, MG was significantly higher when aortic pressure was measured closer to the prosthesis than when it was measured more distally in the aorta. During the in vitro experiments with mechanical bileaflet AVPs, Baumgartner and colleagues compared the pressure gradient measured by pulling the aortic catheter through the central orifice of the prosthesis to the gradient measured by pulling the catheter through the larger side orifices of the prostheses. They found that the pressure recovery phenomenon led to a significantly higher MG closer to the prosthesis than more distally when the catheter was pulled through the central orifice of the valve, but not when the catheter was pulled through the side orifices. When assessing AVPs, proper CW Doppler interrogation of the prosthesis will result in measurement of the highest velocity (corresponding with the lowest aortic pressure). For 19- and 21-mm mechanical bileaflet AVPs, the velocity measured is therefore likely located either within or just beyond the central orifice of the prosthesis. Therefore, a relatively high MG may be normal for 19- and 21-mm bileaflet mechanical AVPs. In cases where these patients undergo invasive catheterization, it is important to realize that the pressure recovery phenomenon will likely lead to discrepancy between the higher MG measured by echocardiography and the lower MG measured invasively. It is equally important to recognize that the pressure recovery phenomenon is an unlikely explanation for a high MG for a bileaflet mechanical AVP that is 23- mm or larger or for a bioprosthesis of any size.
avoid significant PPM is particularly important for younger patients with normal body habitus, and is of utmost importance for patients whose LVEF is significantly decreased.10–12 When a patient with an AVP is found to have a larger than expected MG and smaller than expected EOA, it is necessary to attempt to distinguish between functional prosthesis obstruction (PPM) and pathologic obstruction (such as thrombus or pannus). In this situation, measuring the AVP acceleration time (AT) is essential. Acceleration time is measured by positioning one time caliper at the onset of aortic flow, at the right side of the opening click, and the second time caliper at the peak of the aortic velocity profile. For patients with functional obstruction (i.e., PPM), the AT is usually ≤ 100 ms, while the AT is usually > 100 ms in patients with pathologic AVP obstruction.1
Transprosthetic/periprosthetic regurgitation Since regurgitant jets occur close to the transducer in left parasternal positions and there is no sewing ring between the ultrasound beam and the regurgitant jet in the LVOT, transprosthetic AVP regurgitation can be semi-quantitated using the same methods that have been elucidated for native aortic valve regurgitation13 (Table 2). If color flow imaging and spectral Doppler evaluations lead to the conclusion that regurgitation is moderate or more severe, attempts should be made to quantitate the amount of regurgitation using the PISA and/or continuity methods. With severe acute prosthetic aortic regurgitation, such as often occurs with Staphylococcus aureus endocarditis, the size of the color jet in the LVOT is often unimpressive due to rapid pressure build up in the left ventricle. In these cases, severe aortic regurgitation is suspected when the aortic regurgitation CW Doppler profile is dense and has a short pressure half time (PHT) (≤ 200 ms). If the diastolic pressure in the ventricle is high enough, the mitral valve will close prematurely and diastolic mitral regurgitation may occur. In addition, the mitral inflow pattern will have a restrictive appearance. When quantitation is performed for these patients, the degree of regurgitation is determined according to the effective regurgitant orifice (ERO) area. In these cases, the left ventricle will often only accommodate a small regurgitant volume even though the ERO area is very large due to the rapid rise in LV diastolic pressure.
Evaluation of mitral valve prostheses Diagnosing prosthetic aortic valve dysfunction 2-D echocardiography Fig 1 proposes an algorithmic approach to the evaluation of AVPs with high peak velocity and MG.
Prosthesis–patient mismatch The entity of PPM was first brought to attention by Rahimtoola who stated, “Mismatch can be considered to be present when the effective prosthetic valve area, after insertion into the patient, is less than that of a normal human valve.”8 Mismatch classification is based on EOA indexed to BSA (iEOA). By current definition,9 there is no significant aortic PPM if iEOA is >0.85 cm2/m2, there is moderate mismatch if iEOA is between 0.66 and 0.85 cm2/m2, and there is severe mismatch if iEOA is ≤ 0.65 cm2/m2. Selection of a prosthesis that is large enough to
In addition to obtaining Doppler parameters of the MVP, 2-D imaging of the prosthesis itself is essential. Acoustic shadowing effects may result in inability to adequately image MVPs, particularly mechanical MVPs. Overall cardiac structure and function assessment by 2-D and/or M-mode imaging, including left and right ventricular chamber size and systolic function and left atrial size, is essential in patients with MVPs.
Doppler echocardiography Doppler-derived hemodynamic parameters suggestive of normal MVP function are listed in Table 3.
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Fig 1 – Algorithm for evaluating aortic valve prostheses with high mean gradient. Abbreviations: AT, acceleration time; Bio, bioprosthesis; iEOA, indexed effective orifice area; Mech, mechanical prosthesis; PPM, prosthesis–patient mismatch.
Peak early mitral diastolic velocity (E velocity) Current ASE and EAE recommendations note that the mitral inflow peak early diastolic velocity (E velocity) in most normally functioning bileaflet mechanical MVPs is < 1.9 m/s but can be as high as 2.4 m/s.1 In a series from our institution, E velocity in normally functioning bileaflet mechanical, pericardial and porcine MVPs is < 2.4, < 2.3, and < 2.8 m/s, respectively.5,6,14–16 Various factors, including small prosthesis size, tachycardia, hyperdynamic state, prosthetic stenosis, and transprosthetic or periprosthetic regurgitation, can result in increased E velocity and must be considered when E velocity is higher than the cut-off value for a particular prosthesis type, particularly if E velocity has increased compared to previous studies.
Mean gradient According to recent ASE and EAE recommendations, normal MVPs have an MG < 5 mmHg.1 The recommendations are based on expert opinion and the results of 2 studies that included only 84 prostheses, all St Jude Medical (SJM) mechanical MVPs.17,18 On the basis of a large series evaluated at our institution, normal functioning porcine and pericardial Table 2 – Parameters for assessment of aortic valve transprosthetic/periprosthetic regurgitation. Qualitative or Semiquantitative
Quantitative
Color flow Doppler • Jet width (% LVOT diameter) a CW Doppler • Regurgitant jet density • Regurgitant jet PHT PW Doppler: • Holodiastolic flow reversal in the descending thoracic aorta • Holodiastolic flow reversal in the abdominal aorta
Color flow Doppler • Vena contracta PW Doppler • LVOT flow versus pulmonary flow PISA • Effective regurgitant orifice area • Regurgitant volume • Regurgitant fraction
Abbreviations: CW, continuous wave, LVOT, left ventricular outflow tract; PHT, pressure halftime; PISA, proximal isovelocity surface area; PW, pulsed wave. a Central jets only.
MVPs may have an MG as high as 10 and 8 mmHg, respectively,14,15 while normal functioning bileaflet mechanical MVPs may have an MG as high as 7 mmHg.5,6,16
TIV ratio (TVIMVP/TVILVOT) The ratio of the of the mitral valve prosthesis TVI (TVIMVP) to the TVILVOT (TVIMVP/TVILVOT) is an important parameter to consider when evaluating the function of MVPs, particularly when E velocity and MG are elevated. In high-output states, increased E velocity, MG, and TVIMVP are accompanied by increased SV through the LVOT, resulting in a stable TVI ratio. However, with clinically significant MVP stenosis or regurgitation, increased E velocity, MG, and the TVIMVP are accompanied by normal to reduced SV through the LVOT, which results in increased TVI ratio. According to the current ASE and EAE guidelines, MVPs with TVI ratio < 2.6 are normal,1 whereas in our series, TVIMVP/TVILVOT < 2.2, < 2.2 or < 2.8 suggests normal function in bileaflet mechanical, pericardial, and pericardial MVPs, respectively.5,6,14–16 Table 3 – Doppler parameters suggestive of normal prosthetic mitral valve function. All Prostheses Bileaflet (ASE Mechanical Pericardial Porcine Parameter guidelines) Prostheses Prostheses Prostheses E velocity, m/s Mean gradient, mmHg TVI ratio PHT, ms EOA, cm2
< 1.9
< 2.4
< 2.3
< 2.8
≤5
0.90 and < 1.2 cm2 m2, and absent if iEOA is ≥ 1.2 cm2 m2. Some studies have shown that mitral PPM is associated with decreased survival,21–24 while others studies have found no such association.25–27 Given the variance of study results, the clinical significance of mitral PPM remains unclear. What is clear, however, is that echocardiographers must be able to distinguish functional obstruction (PPM) from pathologic obstruction, as mitral PPM is becoming increasingly more common due to the increasing incidence of obesity. Assessment of PHT is essential in these cases, as PHT is normal in MVPs with PPM but prolonged in MVPs with pathologic obstruction (Fig 2).
Transprosthetic/periprosthetic regurgitation Transprosthetic and periprosthetic mitral valve regurgitation is frequently unable to be accurately assessed by 2D and color Doppler imaging due to acoustic shadowing, so other parameters must be considered. Zoghbi and colleagues have shown that E velocity ≥ 1.9 m/s in association with TVI ratio > 2.2 and normal PHT is predictive of clinically significant mechanical mitral valve prosthesis regurgitation.17 E velocity and TVI ratio cut-off values predictive of bioprosthetic mitral valve regurgitation have not yet been validated. On the basis of a series from our institution, we propose that pathologic regurgitation is present when PHT < 120 ms and TVI ratio ≥ 2.6, ≥ 2.8 and ≥ 3.9 for mitral bileaflet mechanical, pericardial and porcine prostheses, respectively.5,6,14–16 If regurgitant jets are able to be adequately visualized, transprosthetic and periprosthetic mitral valve regurgitation can be semiquantitated using the same methods that have been elucidated for native mitral valve regurgitation13 (Table 4). If regurgitant jets are unable to be adequately appreciated on TTE, TEE imaging is indicated. Cut-off values for the parameters listed may be similar to those for native mitral valve regurgitation, but have not been validated.
Pulmonary artery pressure should be estimated in all patients with MVPs using one of the validated methods.20
Evaluation of tricuspid valve prostheses Diagnosing prosthetic mitral valve dysfunction 2-D echocardiography Fig 2 proposes an approach to the evaluation of MVPs with high MG.
Obstruction/stenosis Diagnosing clinically significant MVP obstruction by 2-D imaging may be challenging due to acoustic shadowing, so assessment of pertinent Doppler parameters is essential. The hallmark Doppler-derived finding in obstructed MVP's is prolonged PHT (> 120–130 ms). Other findings supportive of obstruction include elevated E velocity, MG and TVI ratio and small EOA and iEOA. If TTE findings are suspicious for clinically significant prosthetic MVP obstruction, further imaging is indicated to confirm the findings.
Prosthesis–patient mismatch Although less extensively studied than aortic PPM, mitral PPM has been observed and categories of severity outlined in the literature. Currently, mitral PPM is considered severe if the mitral
Because of the anterior position of the tricuspid valve prosthesis (TVP), assessment of TVPs by TTE is generally superior to imaging by TEE. Multiple imaging windows including parasternal, low parasternal, apical, and subcostal should all be utilized in order to achieve optimal visualization of prosthesis structure and function. In addition to evaluating the TVP, assessment of right ventricular size and function, right atrial size, and size of the inferior vena cava and its response to respiration is necessary.
Doppler echocardiography Although essential Doppler-derived hemodynamic parameters have not been validated, complete evaluation of a TVP should include assessment of E velocity, MG, PHT, TVI of the tricuspid valve prosthesis (TVITVP), TVITVP/TVILVOT (TVI ratio), EOA, and iEOA. Pressure half-time is not infrequently unable
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Table 4 – Parameters for assessment of mitral valve transprosthetic/periprosthetic regurgitation. Indirect Signs Hyperdynamic left ventricle with low cardiac output Elevated E velocity
Elevated TVI ratio
Qualitative or Semiquantitative a Color flow Doppler • Jet area • Flow convergence CW Doppler • Jet density • Jet contour
Table 5 – Doppler parameters suggestive of normal prosthetic tricuspid valve function.
Quantitative a Color flow Doppler • Vena contracta PISA • Effective regurgitant orifice area • Regurgitant volume • Regurgitant fraction
PW Doppler • Pulmonary venous flow pattern
Maximal tricuspid regurgitation jet velocity > 3 m/s Rise in pulmonary artery pressure compared to previous studies Abbreviations: CW, continuous wave, PISA, proximal isovelocity surface area; PW, pulsed wave; TVI ratio, ratio of the time velocity integral of the mitral valve prosthesis to the time velocity integral of the left ventricular outflow tract. a Cut-off values for each of these parameters may be similar to those for native mitral valve regurgitation, but have not been validated.
to be measured due to rounded tricuspid valve prosthesis inflow spectral Doppler envelopes. Unlike MVPs, cut-off values to define normal TVP function have not been validated. On the basis of a large series from our institution, however, we have proposed that normal mechanical TVPs have E velocity < 1.9 m/s, MG < 6 mmHg, TVITVP/TVILVOT < 2.0 and PHT < 130 ms, while normal porcine TVPs have E velocity < 2.0 m/s, MG < 9 mmHg, TVITVP/TVILVOT < 3.2, and PHT < 200 ms2,3 (Table 5). Pericardial TVPs currently are rarely implanted due to reports of increased risk for thrombosis compared with mechanical and porcine TVPs.
Effective orifice area Adequate in vitro EOA data are not available for TVPs to validate use of either the continuity equation or the PHT method to calculate in vivo EOA. Use of the equation 190/PHT has been proposed,28 but has not been validated in a large echocardiography-invasive catheterization cohort. Studies from our institution have shown that calculating tricuspid EOA by using either 190/PHT or 200/PHT tends to significantly overestimate the EOA, while using the continuity equation yields results much close to the in vitro EOA for both mechanical and tissue TVPs.2,3
Other pertinent parameters Pulmonary artery pressure and the hepatic vein flow pattern should be assessed in all patients with TVPs using validated methods. 20
Parameter E velocity, m/s Mean gradient, mmHg TVI ratio PHT, ms EOA, cm2
All Prostheses (ASE Guidelines)
Bileaflet Mechanical Prostheses
Porcine Prostheses
< 1.7
< 1.9
< 2.0
≤6
200 ms for tissue prostheses). Other findings supportive of obstruction include elevated E velocity, MG and TVI ratio and small EOA and iEOA. If TTE findings are suspicious for clinically significant prosthetic TVP obstruction, further imaging is warranted.
Prosthesis–patient mismatch It seems reasonable to propose that as for aortic and mitral valve prostheses, certain patients will have a TVP that is too small for their body habitus, resulting in functional obstruction (PPM). There have been no studies published to date defining cut-off values for tricuspid PPM. We propose that similar to MVPs, tricuspid PPM is defined as iEOA < 1.2 cm 2/m 2, with severe tricuspid PPM defined as iEOA ≤ 0.9 cm 2/m 2. Whether tricuspid PPM is of any clinical significance has yet to be investigated. Similar to MVPs, TVP functional obstruction can be distinguished from pathologic obstruction by PHT. If PHT is ≥ 200 ms, pathologic obstruction is likely, whereas functional obstruction is more likely when PHT is < 200 ms.
Transprosthetic/periprosthetic regurgitation No clinical studies have determined echocardiographic parameters indicative of clinically significant tricuspid transprosthetic or periprosthetic regurgitation. Analogous to MVPs, an elevated MG, E velocity, and TVITVP/TVILVOT in the setting of normal PHT likely indicate pathologic regurgitation. On the basis of a series from our institution, proposed TVI ratio cut-off values are 2.3 and 3.2 for bileaflet mechanical and porcine TVPs, respectively.2,3 Other supportive signs of severe regurgitation include valve dehiscence, large jet area by color Doppler, large vena contracta, dense CW tricuspid regurgitant jet with early peaking velocity,
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velocity, peak gradient, and mean gradient. On the basis of limited studies published to date, recommended cut-off values for normal pulmonary valve homograft conduits are peak velocity < 2.5 m/s and MG < 15 mmHg,29 while cut-off values for normal pulmonary heterografts are peak velocity < 3.2 m/s and MG < 20 mmHg.30 Doppler-derived hemodynamic data for mechanical PVPs are limited, as are data regarding calculated EOA for any type of PVP.
Diagnosing prosthetic pulmonary valve dysfunction The best method for determining PVP function is to complete a thorough 2-D examination for assessment of leaflet mobility and obtain peak velocity, peak gradient, and mean gradient in order to compare findings with values obtained on previous studies. Comparing serial estimations of right ventricular systolic pressure may also be useful for identifying PVP dysfunction. Findings suggestive of clinically significant pulmonary valve prosthetic or periprosthetic regurgitation are similar to findings consistent with severe native pulmonary valve regurgitation, including right ventricular enlargement with flattening of the interventricular septum during diastole, large regurgitant jet width, large vena contracta and depth of regurgitant jet penetration into the right ventricle. In eccentric prosthetic or periprosthetic regurgitant jets, however, Doppler-derived parameters are more challenging to assess and may be unreliable. Important indirect signs suggestive of severe regurgitation include dense CW regurgitant jet with rapid deceleration rate and diastolic flow reversal in the main pulmonary artery. Fig 3 – Algorithm for evaluating tricuspid valve prostheses with high mean gradient. Abbreviations: iEOA, indexed effective orifice area; PHT, pressure halftime; PPM, prosthesis–patient mismatch; TVI ratio, ratio of the time velocity integral of the mitral valve prosthesis to the time velocity integral of the left ventricular outflow tract.
right ventricular and right atrial dilatation, and holosystolic flow reversals in the hepatic veins. If TTE findings suggest clinically significant TVP regurgitation, TEE imaging may be necessary to confirm the TTE findings.
Conclusions Two-dimensional and Doppler echocardiography is the imaging modality of choice for evaluating prosthetic heart valve structure and function. Serial comparison of 2-D images and Doppler findings with a baseline postoperative examination is crucial for accurate assessment of prostheses. Threedimensional imaging is emerging as a technique that may provide incremental value for baseline and serial examinations.
Statement of Conflict of Interest Evaluation of pulmonary valve prostheses 2-D echocardiography Two-dimensional imaging of pulmonary valve prostheses (PVPs) can be challenging by both TTE and TEE due to their anterior–superior position in the heart. Because limited acoustic windows may limit 2-D imaging of pulmonary valve prostheses, Doppler assessment is essential.
Doppler echocardiography Suggested Doppler echocardiographic parameters for assessment of a pulmonary valve prosthesis (PVP) include peak
None.
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15. Blauwet LA, Malouf JF, Connolly HM, Hodge DO, Evans KN, Herges RM, et al. Comprehensive echocardiographic assessment of normal mitral Medtronic Hancock II, Medtronic Mosaic, and Carpentier-Edwards Perimount bioprostheses early after implantation. J Am Soc Echocardiogr. 2010;23:656-666. 16. Blauwet LA, Malouf JF, Connolly HM, Hodge DO, Herges RM, Sundt TM, et al. Doppler echocardiography of 79 normal CarboMedics mitral prostheses: a comprehensive assessment including time–velocity integral ratio and prosthesis performance index. J Am Soc Echocardiogr. 2007;20:1125-1130. 17. Bitar JN, Lechin ME, Salazar G, Zoghbi WA. Doppler echocardiographic assessment with the continuity equation of St Jude Medical mechanical prostheses in the mitral valve position. Am J Cardiol. 1995;76:287-293. [Erratum in: Am J Cardiol 76:642, 1995]. 18. Panidis IP, Ross J, Mintz GS. Normal and abnormal prosthetic valve function as assessed by Doppler echocardiography. J Am Coll Cardiol. 1986;8:317-326. 19. Hatle L, Angelsen B, Tromsdal A. Noninvasive assessment of atrioventricular pressure half-time by Doppler ultrasound. Circulation. 1979;60:1096-1104. 20. Rudski LG, Lai WW, Afilalo J, Hua L, Handschumacher MD, Chandrasekaran K, et al. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. J Am Soc Echocardiogr. 2010;23:685-713. [quiz 786-8]. 21. Bouchard D, Vanden Eynden F, Demers P, Perrault LP, Carrier M, Cartier R, et al. Patient–prosthesis mismatch in the mitral position affects midterm survival and functional status. Can J Cardiol. 2010;26:532-536. 22. Aziz A, Lawton JS, Maniar HS, Pasque MK, Damiano RJ Jr, Moon MR. Factors affecting survival after mitral valve replacement in patients with prosthesis–patient mismatch. Ann Thorac Surg. 2010;90:1202-1210. 23. Lam BK, Chan V, Hendry P, Ruel M, Masters R, Bedard P, et al. The impact of patient–prosthesis mismatch on late outcomes after mitral valve replacement. J Thorac Cardiovasc Surg. 2007;133:1464-1473. 24. Magne J, Mathieu P, Dumesnil JG, Tanné D, Dagenais F, Doyle D, et al. Impact of prosthesis–patient mismatch on survival after mitral valve replacement. Circulation. 2007;115:14171425. 25. Shi WY, Yap CH, Hayward PA, Dinh DT, Reid CM, Shardey GC, et al. Impact of prosthesis–patient mismatch after mitral valve replacement: a multicentre analysis of early outcomes and mid-term survival. Heart. 2011;97:1074-1081. 26. Sakamento H, Watanabe Y. Does patient–prosthesis mismatch affect long-term results after mitral valve replacement? Ann Thorac Cardiovasc Surg. 2010;16:163-167. 27. Jamieson WR, Germann E, Ye J, Chan F, Cheung A, MacNab JS, et al. Effect of prosthesis–patient mismatch on long-term survival with mitral valve replacement: assessment to 15 years. Ann Thorac Surg. 2009;87:1135-1141. 28. Fawzy ME, Mercer EN, Dunn B, al-Amri M, Andaya W. Doppler echocardiography in the evaluation of tricuspid stenosis. Eur Heart J. 1989;10:985-990. 29. Meliones JN, Snider Ar, Bove EL, Serwer GA, Peters J, Lacina SJ, et al. Doppler evaluation of homograft valved conduits in children. Am J Cardiol. 1989;64:354-358. 30. Novaro GM, Connolly HM, Miller FA. Doppler hemodynamics of 51 clinically and echocardiographically normal pulmonary valve prostheses. Mayo Clin Proc. 2001;76:155-160.
Available online at www.sciencedirect.com
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Echocardiographic Assessment of Prosthetic Heart Valves Lori A. Blauwet, Fletcher A. Miller Jr. Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA
A R T I C LE I N FO
AB S T R A C T
Keywords:
Valvular heart disease is a global health problem. It is estimated that more than 280,000
Echocardiography
prosthetic heart valves are implanted worldwide each year. As the world's population is
Doppler
aging, the incidence of prosthetic heart valve implantation and the prevalence of prosthetic
Prosthesis
heart valves continue to increase. Assessing heart valve prosthesis function remains
Heart valves
challenging, as prosthesis malfunction is unpredictable but not uncommon. Transthoracic two-dimensional and Doppler echocardiography is the preferred method for assessing prosthetic valve function. Clinically useful Doppler-derived measures for assessing prosthetic valve hemodynamic profiles have been reported for aortic, mitral, and tricuspid valve prostheses, but echocardiographic data regarding pulmonary valve prostheses remain limited. Complete prosthetic valve evaluation by transthoracic echocardiography (TTE) is sometimes challenging due to acoustic shadowing and artifacts. In these cases, further imaging with transesophageal echocardiography, fluoroscopy and/or gated CT may be warranted, particularly if prosthetic valve dysfunction is suspected. Being able to differentiate pathologic versus functional obstruction of an individual prosthesis is extremely important, as this distinction affects management decisions. Transprosthetic and periprosthetic regurgitation may be difficult to visualize on TTE, so careful review of Doppler-derived data combined with a high index of suspicion is warranted, particularly in symptomatic patients. A baseline TTE soon after valve implantation is indicated in order to “fingerprint” the prosthesis hemodynamic profile. It remains unclear how frequently serial imaging should be performed in order to assess prosthetic valve function, as this issue has not been systematically studied. © 2014 Elsevier Inc. All rights reserved.
Echocardiography has become the primary tool for assessment of patients with prosthetic heart valves. Comprehensive guidelines for evaluation of prosthetic heart valves by echocardiography have been published by the American
Society of Echocardiography (ASE) and the European Association of Echocardiography (EAE).1 Readers are strongly encouraged to familiarize themselves with these guidelines. This manuscript will primarily focus on transthoracic
Statement of Conflict of Interest: see page 109. Address reprint requests to Lori A. Blauwet, MD, and Fletcher A. Miller Jr, MD, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. E-mail addresses: [email protected] (L.A. Blauwet), [email protected] (F.A. Miller). http://dx.doi.org/10.1016/j.pcad.2014.05.001 0033-0620/© 2014 Elsevier Inc. All rights reserved.
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Abbreviations and Acronyms 2D = 2-dimensional AHA/ACC = American Heart Association/American College of Cardiology
echocardiography (TTE) assessment of prosthetic heart valves that have been implanted by standard surgical techniques.
AT = acceleration time ASE = American Society of Echocardiography AVP = aortic valve prosthesis
General considerations Clinical data
BSA = body surface area CW = continuous wave E velocity = peak early mitral diastolic velocity EAE = European Association of Echocardiography EOA = effective orifice area ERO = effective regurgitant orifice iEOA = indexed effective orifice area LV = left ventricular LVEF = left ventricular ejection fraction MG = mean gradient MVP = mitral valve prosthesis PHT = pressure half-time PPM = prosthesis–patient mismatch PVP = pulmonary valve prosthesis SV = stroke volume SVI = stroke volume index TEE = transesophageal echocardiography TTE = transthoracic echocardiography TVI = time velocity integral TVIAVP = time velocity integral of the aortic valve prosthesis TVILVOT = time velocity integral of the left ventricular outflow tract TVIMVP = time velocity integral of the mitral valve prosthesis TVITVP = time velocity integral of the mitral valve prosthesis TVI ratio = ratio of the time velocity integral of the prosthesis to the time velocity integral of the left ventricular outflow tract TVP = tricuspid valve prosthesis
Assessment and documentation of clinical data including patient height, weight, body surface area, blood pressure and heart rate are essential. Knowing patient size is particularly important for determining whether prosthesis– patient mismatch (PPM) is present, while knowing a patient's blood pressure at the time of the echocardiographic examination is important due to the effect of blood pressure on determining the severity of certain prosthetic valve lesions, particularly mitral valve transprosthetic/ periprosthetic regurgitation. Recording the heart rate at the time of Doppler assessment is particularly important when assessing mitral and tricuspid valve prostheses because mean gradient (MG) depends on the diastolic filling time. Noting operative data including prosthesis type, prosthesis size, date of implantation and any associated operative procedures such aortic root enlargement, is crucial for accurate interpretation of 2-dimensional (2-D) and Doppler
findings, as hemodynamic profiles differ among various prosthesis types and sizes.
2-Dimensional echocardiography Prostheses should be imaged from multiple views with particular attention paid to the motion of the occluders/ leaflets, the presence or absence of echo densities attached to the sewing ring, cage, struts and/or occluders/leaflets, and the integrity of the sewing ring/annular interface. Observing abnormal rocking motion of the prosthesis suggests dehiscence. Magnification of real-time 2-D images is often necessary for optimal visualization.
Doppler echocardiography Prosthetic valve assessment with color flow, pulsed wave (PW), and continuous wave (CW) Doppler imaging should be performed using similar principles and techniques used for assessment of native valves, including interrogation of the prosthesis from multiple windows and proper alignment of the Doppler beam with flow direction. Hemodynamic parameters of aortic, mitral, tricuspid and pulmonary valve prostheses that should be assessed during TTE are listed in Table 1. One key factor to consider during interrogation of prosthetic valves is that Doppler-derived parameters vary with cycle length. For aortic, mitral and pulmonary valve prostheses, Doppler measurements from three consecutive cardiac cycles should be averaged if the patient is in sinus rhythm and a minimum of five cardiac cycles averaged if the patient is in atrial fibrillation or another irregular rhythm. For patients with irregular rhythms, attempts should be made to use periods of physiologic heart rate and to match five cardiac cycle lengths for each Doppler parameter assessed. For patients with tricuspid valve prostheses (TVPs), it is important to remember that Doppler-derived hemodynamic Table 1 – Complete Doppler assessment of prosthetic valves. Aortic Valve Prostheses
Mitral Valve Prostheses
Tricuspid Valve Prostheses
Pulmonary Valve Prostheses
Peak velocity Mean gradient Acceleration time Dimensionless index Effective orifice area Indexed effective orifice area Regurgitation: presence, location, severity
E velocity Mean gradient Pressure halftime TVI ratio
E velocity Mean gradient Pressure halftime TVI ratio
Peak velocity Peak gradient Mean gradient
Effective orifice area Indexed effective orifice area Regurgitation: presence, location, severity
Effective orifice area Indexed effective orifice area Regurgitation: presence, location, severity
Regurgitation: presence, location, severity
Abbreviations: TVI ratio, ratio of the time velocity integral of the mitral valve prosthesis to the time velocity integral of the left ventricular outflow tract.
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parameters vary not only with cycle length, but also with respiration. Averaging a minimum of 3–5 consecutive cardiac cycles or obtaining measurements in midexpiratory apnea is recommended for all patients with TVPs.1–3
Transprosthetic/periprosthetic regurgitation Regurgitant jets may travel through the prosthesis (transprosthetic regurgitation) or around the sewing ring (periprosthetic regurgitation). Central jets are most often transprosthetic. Jets that originate anteriorly, posteriorly, medially or laterally may be either transprosthetic or periprosthetic. If the regurgitant color flow jet can be clearly identified outside the ring, then the diagnosis of periprosthetic regurgitation can be made with confidence. On occasion, particularly with tissue prostheses, transprosthetic jets may occur very close to the inner edge of the sewing ring and may be difficult to distinguish from periprosthetic regurgitation. Some transprosthetic jets are normal. For instance, it is relatively common to see a trivial central regurgitant jet with normal tissue prostheses. Mechanical prostheses are designed such that a small amount of transprosthetic regurgitation occurs during normal prosthesis function. Currently, the most commonly encountered mechanical valve prostheses are designed with a bileaflet occluding mechanism. For these valves, two small “washing jets” travel between the inner edge of the sewing ring and the outer edge of the leaflets. One jet originates near the inner border of the anterior sewing ring and the second jet originates near the inner border of the posterior sewing ring. Theoretically, these jets help to prevent thrombus formation in the bileaflet pivot slots, which are on the inner part of the circular housing. It is important that physicians interpreting echocardiography studies of prosthetic valves are familiar with the appearance of these jets so that the presence of these normal regurgitant jets does not lead to an erroneous interpretation of pathologic regurgitation.
Flow affects on Doppler-derived hemodynamic parameters Not all dysfunctional prostheses have a high MG, so MG should not be the sole parameter considered when assessing prosthetic valves. In low output states, many of the Dopplerderived hemodynamic parameters may be normal or only mildly abnormal even when a prosthesis is severely dysfunctional. In these cases, a high degree of suspicion and careful evaluation are warranted in order to accurately ascertain whether or not a particular prosthesis is dysfunctional. As a corollary, a high MG does not necessary indicate prosthetic valve dysfunction. Aortic valve prosthesis (AVP) peak velocity and mean gradient may be elevated due to pathologic obstruction or regurgitation, but may also be elevated due to “functional obstruction,” i.e., prosthesis– patient mismatch (PPM) or pressure recovery phenomenon, or a high flow state. Elevated mitral valve prosthesis (MVP) and tricuspid valve prosthesis (TVP) E velocity and MG may be due to pathological obstruction or regurgitation, but may also be due to PPM or a high flow state secondary to tachycardia, anemia, hyperthyroidism, arteriovenous fistula or malformations, or severe renal or hepatic disease.
Timing of echocardiographic examinations Patients with newly implanted valves should have a full TTE study, including comprehensive Doppler assessment, to “fingerprint” the prosthesis as a baseline for future followup. According to the recent American Heart Association/ American College of Cardiology (AHA/ACC) guidelines on the management of patients with valvular heart disease, obtaining a baseline TTE is a class I recommendation (Level of Evidence: C).4 The AHA/ACC guidelines recommend that the initial TTE be obtained 6 weeks to 3 months after valve implantation. The practice at our institution is to “fingerprint” the prosthesis by performing postoperative TTE on patients who have undergone valve replacement prior to hospital discharge. We have shown that there are no significant differences between bileaflet mechanical MVP Dopplerderived hemodynamic profiles obtained in the early postoperative period and profiles obtained up to 13 months after implantation,5,6 so performing a postoperative TTE at any time between several days to several weeks after surgical implantation when the patient is hemodynamically stable should be acceptable, at least for these types of prostheses. Echocardiography is an essential component of the assessment of any patient when prosthetic valve dysfunction is a clinical concern. Current AHA/ACC guidelines state that repeat TTE is recommended in patients with prosthetic heart valves if there is a change in clinical signs or symptoms suggesting valve dysfunction (class I; Level of Evidence: C) and that TEE is recommended when clinical signs or symptoms suggest prosthetic valve dysfunction (class I; Level of Evidence: C).4 There is lack of consensus regarding timing of echocardiographic follow-up for asymptomatic patients with prosthetic heart valves, largely due to lack of evidence. Current ACC/AHA guidelines on the management of patients with valvular heart disease state that “No further echocardiographic testing is required after the initial postoperative evaluation in patients with mechanical valves who are stable and who have no symptoms or clinical evidence of prosthetic valve or ventricular dysfunction or dysfunction of other heart valves.”4 This statement is given neither a classification of recommendation nor a level of evidence to support the statement. Regarding bioprosthetic valves, the current ACC/AHA guidelines recommend that an “annual TTE is reasonable in patients with a bioprosthetic valve after the first 10 years, even in the absence of a change in clinical status” (class IIa; Level of Evidence: C).4 Knowledge of prosthesis type and size and baseline echocardiographic parameters, as well as comparison with serial echocardiographic studies, is tremendously helpful in determining whether a particular prosthesis has normal versus abnormal function. During follow-up TTE examinations, observing changes in any of the pertinent Doppler-derived prosthetic parameters compared to previous echocardiographic examinations may indicate possible prosthetic valve dysfunction.
Indications for use of additional imaging modalities Occluder motion of mechanical valve prostheses may be difficult to visualize by 2-D imaging during TTE due to artifact and/or acoustic shadowing; in these cases, transesophageal
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echocardiography (TEE), fluoroscopy or gated CT imaging may be warranted, particularly when prosthetic valve dysfunction is suspected. Three-dimensional (3-D) assessment of the prosthesis during TEE examination and/or 3-D reconstruction of the prosthesis on CT imaging may be especially helpful. Clinically significant transprosthetic or periprosthetic regurgitation may be difficult to visualize on TTE imaging due to acoustic shadowing, particularly in patients with mechanical MVPs. If the Doppler-derived hemodynamic profile obtained by TTE imaging suggests moderate or more severe regurgitation despite little to no regurgitation visualized by Doppler color flow imaging, TEE imaging is warranted, particularly if the patient is symptomatic. Real time 3-D color flow imaging may be particularly helpful for determining the exact location and size of regurgitant orifices and may also facilitate the quantitation of regurgitation.
Evaluation of aortic valve prostheses 2-D echocardiography Every attempt should be made to image all portions of the AVP in both short and long axis views during TTE imaging. For tissue AVPs, this involves imaging of the sewing ring, cusps and stents (if present). For mechanical AVPs, the sewing ring can almost always be imaged, while it is more difficult to image the occluder(s), particularly when dealing with small AVPs. For larger bileaflet mechanical AVPs, it is often possible to image the occluders in long axis and/or short axis to verify that they are opening fully.
Doppler echocardiography The major potential pitfall for Doppler echocardiography is improper alignment of the Doppler beam with the jet being interrogated. For this reason, Doppler evaluation for AVPs must be performed from multiple transducer positions, including apical and para-apical, right parasternal (with the patient in right lateral decubitus position), right supraclavicular and suprasternal. The largest CW Doppler profiles are traced to obtain the prosthetic valve MG, peak velocity, and the time velocity integral (TVI). The position yielding the highest peak velocity and MG should be recorded in the report in order to facilitate future studies for the same patient. The continuity method is used to calculate the AVP effective orifice area (EOA): AVP EOA equals left ventricular (LV) stroke volume (SV) divided by the AVP TVI (TVIAVP). The LV SV is calculated as the product of the LVOT area and the TVI of flow in the LVOT (TVILVOT). For the vast majority of patients with AVPs, the LVOT diameter can be measured, and it is this measurement that should be used for SV calculation. In a minority of cases, in which landmarks for LVOT diameter measurement may be uncertain, AVP size can be used as a surrogate for the LVOT diameter. The LVOT diameter measurement is made from a parasternal long axis zoom view of the LVOT and aortic root. The image is frozen in peak systole and the LVOT diameter is measured by placing one caliper anteriorly at the junction of
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the ventricular septum and the anterior portion of the sewing ring and the second caliper at the junction of the posterior sewing ring and the base of the anterior mitral leaflet. The velocity profile for the LVOT is obtained from an apical long axis view. As for patients with native aortic valve stenosis, it important to recognize that there is a zone of flow convergence in the LVOT just proximal to the AVP. The continuity method requires that the velocity utilized for the SV calculation is the spatial mean velocity, which is obtained by moving the sample volume 0.5 to 1.0 cm away from the prosthesis sewing ring toward the LV apex. Assuming circular geometry of the LVOT at the level of the ventricular surface of the AVP sewing ring, the LVOT area is calculated as LVOT diameter squared times 0.785. Since measurement of the LVOT diameter and TVILVOT both have potential pitfalls, it is important to verify that the calculated SV makes clinical sense. Calculation of the LV stroke volume index (SVI) and checking it against LV size and left ventricular ejection fraction (LVEF) are recommended. Using the SVI instead of the SV facilitates this comparison, since body surface area (BSA) is taken into account. In most cases, patients with normal LV size and LVEF will have a normal SVI. If the measured SVI seems too large or too small for a particular patient, additional imaging should be obtained to reassess the LVOT diameter and/ or TVILVOT. The TVIAVP that is used to calculate AVP EOA is determined at the same time that the AVP peak velocity and MG are measured. Once a reasonable SVI has been obtained, the unindexed SV can be divided by the TVIAVP to determine the AVP EOA. Effective orifice area should be compared to the AVP MG for concordance. For instance, if the AVP EOA is ≤ 0.6 cm2, the MG will usually be ≥ 50 mmHg. If the AVP EOA is ≤ 0.6 cm2 and the MG is significantly < 50 mmHg, a reason for this discordance must be determined. Possible explanations for such a discordance include small left ventricular cavity, decreased LVEF, altered myocardial systolic function (decreased global longitudinal systolic strain), increased global hemodynamic load (valvuloarterial impedence), severe mitral and/or tricuspid regurgitation and inaccurate measurement of LVOT diameter and/or TVILVOT. If there is no pathophysiologic explanation, it is likely that either the LVOT diameter measurement was too small or the sample volume position for obtaining the LVOT velocity profile was too far from the AVP sewing ring. In this case, repeat imaging and Doppler evaluation should occur prior to generation of the final report. If an unexplained discrepancy persists, this should be highlighted in the final report.
Pressure recovery When blood accelerates through an AVP, the lowest pressure and highest velocity beyond the prosthesis occur at the vena contracta. This is typically located within a few millimeters of the prosthesis outflow orifice. As blood moves further into the aorta, the pressure recovers with a corresponding decrease in velocity. This means that the pressure gradient, determined by subtracting the aortic pressure from the LV pressure, may differ depending on the distance of the aortic pressure measurement from the vena contracta. The potential importance of this phenomenon for hemodynamic assessment of AVPs was first elucidated via in vitro
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experiments carried out by Baumgartner et al.7 Different types and sizes of mechanical and tissue prostheses were placed in position between an artificial LV and an artificial aorta. For each experiment, LV pressure was measured by a catheter that was positioned in the artificial LV. A second catheter was pulled from the LV through the prosthesis into the artificial aorta. Aortic pressure was measured immediately adjacent to the aortic side of the prosthesis and at multiple distances beyond this. For tissue AVPs and for larger mechanical AVPs, the pressure measured closest to the aortic side of the prosthesis was not significantly different from the pressures measured with the tip of the aortic catheter moved more distally into the aorta. For 19and 21-mm bileaflet mechanical AVPs, however, the pressure measured 3 to 5 mm beyond the aortic side of the prosthesis AVP was significantly lower than the pressure measured 10 mm and more beyond the prosthesis. Therefore, MG was significantly higher when aortic pressure was measured closer to the prosthesis than when it was measured more distally in the aorta. During the in vitro experiments with mechanical bileaflet AVPs, Baumgartner and colleagues compared the pressure gradient measured by pulling the aortic catheter through the central orifice of the prosthesis to the gradient measured by pulling the catheter through the larger side orifices of the prostheses. They found that the pressure recovery phenomenon led to a significantly higher MG closer to the prosthesis than more distally when the catheter was pulled through the central orifice of the valve, but not when the catheter was pulled through the side orifices. When assessing AVPs, proper CW Doppler interrogation of the prosthesis will result in measurement of the highest velocity (corresponding with the lowest aortic pressure). For 19- and 21-mm mechanical bileaflet AVPs, the velocity measured is therefore likely located either within or just beyond the central orifice of the prosthesis. Therefore, a relatively high MG may be normal for 19- and 21-mm bileaflet mechanical AVPs. In cases where these patients undergo invasive catheterization, it is important to realize that the pressure recovery phenomenon will likely lead to discrepancy between the higher MG measured by echocardiography and the lower MG measured invasively. It is equally important to recognize that the pressure recovery phenomenon is an unlikely explanation for a high MG for a bileaflet mechanical AVP that is 23- mm or larger or for a bioprosthesis of any size.
avoid significant PPM is particularly important for younger patients with normal body habitus, and is of utmost importance for patients whose LVEF is significantly decreased.10–12 When a patient with an AVP is found to have a larger than expected MG and smaller than expected EOA, it is necessary to attempt to distinguish between functional prosthesis obstruction (PPM) and pathologic obstruction (such as thrombus or pannus). In this situation, measuring the AVP acceleration time (AT) is essential. Acceleration time is measured by positioning one time caliper at the onset of aortic flow, at the right side of the opening click, and the second time caliper at the peak of the aortic velocity profile. For patients with functional obstruction (i.e., PPM), the AT is usually ≤ 100 ms, while the AT is usually > 100 ms in patients with pathologic AVP obstruction.1
Transprosthetic/periprosthetic regurgitation Since regurgitant jets occur close to the transducer in left parasternal positions and there is no sewing ring between the ultrasound beam and the regurgitant jet in the LVOT, transprosthetic AVP regurgitation can be semi-quantitated using the same methods that have been elucidated for native aortic valve regurgitation13 (Table 2). If color flow imaging and spectral Doppler evaluations lead to the conclusion that regurgitation is moderate or more severe, attempts should be made to quantitate the amount of regurgitation using the PISA and/or continuity methods. With severe acute prosthetic aortic regurgitation, such as often occurs with Staphylococcus aureus endocarditis, the size of the color jet in the LVOT is often unimpressive due to rapid pressure build up in the left ventricle. In these cases, severe aortic regurgitation is suspected when the aortic regurgitation CW Doppler profile is dense and has a short pressure half time (PHT) (≤ 200 ms). If the diastolic pressure in the ventricle is high enough, the mitral valve will close prematurely and diastolic mitral regurgitation may occur. In addition, the mitral inflow pattern will have a restrictive appearance. When quantitation is performed for these patients, the degree of regurgitation is determined according to the effective regurgitant orifice (ERO) area. In these cases, the left ventricle will often only accommodate a small regurgitant volume even though the ERO area is very large due to the rapid rise in LV diastolic pressure.
Evaluation of mitral valve prostheses Diagnosing prosthetic aortic valve dysfunction 2-D echocardiography Fig 1 proposes an algorithmic approach to the evaluation of AVPs with high peak velocity and MG.
Prosthesis–patient mismatch The entity of PPM was first brought to attention by Rahimtoola who stated, “Mismatch can be considered to be present when the effective prosthetic valve area, after insertion into the patient, is less than that of a normal human valve.”8 Mismatch classification is based on EOA indexed to BSA (iEOA). By current definition,9 there is no significant aortic PPM if iEOA is >0.85 cm2/m2, there is moderate mismatch if iEOA is between 0.66 and 0.85 cm2/m2, and there is severe mismatch if iEOA is ≤ 0.65 cm2/m2. Selection of a prosthesis that is large enough to
In addition to obtaining Doppler parameters of the MVP, 2-D imaging of the prosthesis itself is essential. Acoustic shadowing effects may result in inability to adequately image MVPs, particularly mechanical MVPs. Overall cardiac structure and function assessment by 2-D and/or M-mode imaging, including left and right ventricular chamber size and systolic function and left atrial size, is essential in patients with MVPs.
Doppler echocardiography Doppler-derived hemodynamic parameters suggestive of normal MVP function are listed in Table 3.
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Fig 1 – Algorithm for evaluating aortic valve prostheses with high mean gradient. Abbreviations: AT, acceleration time; Bio, bioprosthesis; iEOA, indexed effective orifice area; Mech, mechanical prosthesis; PPM, prosthesis–patient mismatch.
Peak early mitral diastolic velocity (E velocity) Current ASE and EAE recommendations note that the mitral inflow peak early diastolic velocity (E velocity) in most normally functioning bileaflet mechanical MVPs is < 1.9 m/s but can be as high as 2.4 m/s.1 In a series from our institution, E velocity in normally functioning bileaflet mechanical, pericardial and porcine MVPs is < 2.4, < 2.3, and < 2.8 m/s, respectively.5,6,14–16 Various factors, including small prosthesis size, tachycardia, hyperdynamic state, prosthetic stenosis, and transprosthetic or periprosthetic regurgitation, can result in increased E velocity and must be considered when E velocity is higher than the cut-off value for a particular prosthesis type, particularly if E velocity has increased compared to previous studies.
Mean gradient According to recent ASE and EAE recommendations, normal MVPs have an MG < 5 mmHg.1 The recommendations are based on expert opinion and the results of 2 studies that included only 84 prostheses, all St Jude Medical (SJM) mechanical MVPs.17,18 On the basis of a large series evaluated at our institution, normal functioning porcine and pericardial Table 2 – Parameters for assessment of aortic valve transprosthetic/periprosthetic regurgitation. Qualitative or Semiquantitative
Quantitative
Color flow Doppler • Jet width (% LVOT diameter) a CW Doppler • Regurgitant jet density • Regurgitant jet PHT PW Doppler: • Holodiastolic flow reversal in the descending thoracic aorta • Holodiastolic flow reversal in the abdominal aorta
Color flow Doppler • Vena contracta PW Doppler • LVOT flow versus pulmonary flow PISA • Effective regurgitant orifice area • Regurgitant volume • Regurgitant fraction
Abbreviations: CW, continuous wave, LVOT, left ventricular outflow tract; PHT, pressure halftime; PISA, proximal isovelocity surface area; PW, pulsed wave. a Central jets only.
MVPs may have an MG as high as 10 and 8 mmHg, respectively,14,15 while normal functioning bileaflet mechanical MVPs may have an MG as high as 7 mmHg.5,6,16
TIV ratio (TVIMVP/TVILVOT) The ratio of the of the mitral valve prosthesis TVI (TVIMVP) to the TVILVOT (TVIMVP/TVILVOT) is an important parameter to consider when evaluating the function of MVPs, particularly when E velocity and MG are elevated. In high-output states, increased E velocity, MG, and TVIMVP are accompanied by increased SV through the LVOT, resulting in a stable TVI ratio. However, with clinically significant MVP stenosis or regurgitation, increased E velocity, MG, and the TVIMVP are accompanied by normal to reduced SV through the LVOT, which results in increased TVI ratio. According to the current ASE and EAE guidelines, MVPs with TVI ratio < 2.6 are normal,1 whereas in our series, TVIMVP/TVILVOT < 2.2, < 2.2 or < 2.8 suggests normal function in bileaflet mechanical, pericardial, and pericardial MVPs, respectively.5,6,14–16 Table 3 – Doppler parameters suggestive of normal prosthetic mitral valve function. All Prostheses Bileaflet (ASE Mechanical Pericardial Porcine Parameter guidelines) Prostheses Prostheses Prostheses E velocity, m/s Mean gradient, mmHg TVI ratio PHT, ms EOA, cm2
< 1.9
< 2.4
< 2.3
< 2.8
≤5
0.90 and < 1.2 cm2 m2, and absent if iEOA is ≥ 1.2 cm2 m2. Some studies have shown that mitral PPM is associated with decreased survival,21–24 while others studies have found no such association.25–27 Given the variance of study results, the clinical significance of mitral PPM remains unclear. What is clear, however, is that echocardiographers must be able to distinguish functional obstruction (PPM) from pathologic obstruction, as mitral PPM is becoming increasingly more common due to the increasing incidence of obesity. Assessment of PHT is essential in these cases, as PHT is normal in MVPs with PPM but prolonged in MVPs with pathologic obstruction (Fig 2).
Transprosthetic/periprosthetic regurgitation Transprosthetic and periprosthetic mitral valve regurgitation is frequently unable to be accurately assessed by 2D and color Doppler imaging due to acoustic shadowing, so other parameters must be considered. Zoghbi and colleagues have shown that E velocity ≥ 1.9 m/s in association with TVI ratio > 2.2 and normal PHT is predictive of clinically significant mechanical mitral valve prosthesis regurgitation.17 E velocity and TVI ratio cut-off values predictive of bioprosthetic mitral valve regurgitation have not yet been validated. On the basis of a series from our institution, we propose that pathologic regurgitation is present when PHT < 120 ms and TVI ratio ≥ 2.6, ≥ 2.8 and ≥ 3.9 for mitral bileaflet mechanical, pericardial and porcine prostheses, respectively.5,6,14–16 If regurgitant jets are able to be adequately visualized, transprosthetic and periprosthetic mitral valve regurgitation can be semiquantitated using the same methods that have been elucidated for native mitral valve regurgitation13 (Table 4). If regurgitant jets are unable to be adequately appreciated on TTE, TEE imaging is indicated. Cut-off values for the parameters listed may be similar to those for native mitral valve regurgitation, but have not been validated.
Pulmonary artery pressure should be estimated in all patients with MVPs using one of the validated methods.20
Evaluation of tricuspid valve prostheses Diagnosing prosthetic mitral valve dysfunction 2-D echocardiography Fig 2 proposes an approach to the evaluation of MVPs with high MG.
Obstruction/stenosis Diagnosing clinically significant MVP obstruction by 2-D imaging may be challenging due to acoustic shadowing, so assessment of pertinent Doppler parameters is essential. The hallmark Doppler-derived finding in obstructed MVP's is prolonged PHT (> 120–130 ms). Other findings supportive of obstruction include elevated E velocity, MG and TVI ratio and small EOA and iEOA. If TTE findings are suspicious for clinically significant prosthetic MVP obstruction, further imaging is indicated to confirm the findings.
Prosthesis–patient mismatch Although less extensively studied than aortic PPM, mitral PPM has been observed and categories of severity outlined in the literature. Currently, mitral PPM is considered severe if the mitral
Because of the anterior position of the tricuspid valve prosthesis (TVP), assessment of TVPs by TTE is generally superior to imaging by TEE. Multiple imaging windows including parasternal, low parasternal, apical, and subcostal should all be utilized in order to achieve optimal visualization of prosthesis structure and function. In addition to evaluating the TVP, assessment of right ventricular size and function, right atrial size, and size of the inferior vena cava and its response to respiration is necessary.
Doppler echocardiography Although essential Doppler-derived hemodynamic parameters have not been validated, complete evaluation of a TVP should include assessment of E velocity, MG, PHT, TVI of the tricuspid valve prosthesis (TVITVP), TVITVP/TVILVOT (TVI ratio), EOA, and iEOA. Pressure half-time is not infrequently unable
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Table 4 – Parameters for assessment of mitral valve transprosthetic/periprosthetic regurgitation. Indirect Signs Hyperdynamic left ventricle with low cardiac output Elevated E velocity
Elevated TVI ratio
Qualitative or Semiquantitative a Color flow Doppler • Jet area • Flow convergence CW Doppler • Jet density • Jet contour
Table 5 – Doppler parameters suggestive of normal prosthetic tricuspid valve function.
Quantitative a Color flow Doppler • Vena contracta PISA • Effective regurgitant orifice area • Regurgitant volume • Regurgitant fraction
PW Doppler • Pulmonary venous flow pattern
Maximal tricuspid regurgitation jet velocity > 3 m/s Rise in pulmonary artery pressure compared to previous studies Abbreviations: CW, continuous wave, PISA, proximal isovelocity surface area; PW, pulsed wave; TVI ratio, ratio of the time velocity integral of the mitral valve prosthesis to the time velocity integral of the left ventricular outflow tract. a Cut-off values for each of these parameters may be similar to those for native mitral valve regurgitation, but have not been validated.
to be measured due to rounded tricuspid valve prosthesis inflow spectral Doppler envelopes. Unlike MVPs, cut-off values to define normal TVP function have not been validated. On the basis of a large series from our institution, however, we have proposed that normal mechanical TVPs have E velocity < 1.9 m/s, MG < 6 mmHg, TVITVP/TVILVOT < 2.0 and PHT < 130 ms, while normal porcine TVPs have E velocity < 2.0 m/s, MG < 9 mmHg, TVITVP/TVILVOT < 3.2, and PHT < 200 ms2,3 (Table 5). Pericardial TVPs currently are rarely implanted due to reports of increased risk for thrombosis compared with mechanical and porcine TVPs.
Effective orifice area Adequate in vitro EOA data are not available for TVPs to validate use of either the continuity equation or the PHT method to calculate in vivo EOA. Use of the equation 190/PHT has been proposed,28 but has not been validated in a large echocardiography-invasive catheterization cohort. Studies from our institution have shown that calculating tricuspid EOA by using either 190/PHT or 200/PHT tends to significantly overestimate the EOA, while using the continuity equation yields results much close to the in vitro EOA for both mechanical and tissue TVPs.2,3
Other pertinent parameters Pulmonary artery pressure and the hepatic vein flow pattern should be assessed in all patients with TVPs using validated methods. 20
Parameter E velocity, m/s Mean gradient, mmHg TVI ratio PHT, ms EOA, cm2
All Prostheses (ASE Guidelines)
Bileaflet Mechanical Prostheses
Porcine Prostheses
< 1.7
< 1.9
< 2.0
≤6
200 ms for tissue prostheses). Other findings supportive of obstruction include elevated E velocity, MG and TVI ratio and small EOA and iEOA. If TTE findings are suspicious for clinically significant prosthetic TVP obstruction, further imaging is warranted.
Prosthesis–patient mismatch It seems reasonable to propose that as for aortic and mitral valve prostheses, certain patients will have a TVP that is too small for their body habitus, resulting in functional obstruction (PPM). There have been no studies published to date defining cut-off values for tricuspid PPM. We propose that similar to MVPs, tricuspid PPM is defined as iEOA < 1.2 cm 2/m 2, with severe tricuspid PPM defined as iEOA ≤ 0.9 cm 2/m 2. Whether tricuspid PPM is of any clinical significance has yet to be investigated. Similar to MVPs, TVP functional obstruction can be distinguished from pathologic obstruction by PHT. If PHT is ≥ 200 ms, pathologic obstruction is likely, whereas functional obstruction is more likely when PHT is < 200 ms.
Transprosthetic/periprosthetic regurgitation No clinical studies have determined echocardiographic parameters indicative of clinically significant tricuspid transprosthetic or periprosthetic regurgitation. Analogous to MVPs, an elevated MG, E velocity, and TVITVP/TVILVOT in the setting of normal PHT likely indicate pathologic regurgitation. On the basis of a series from our institution, proposed TVI ratio cut-off values are 2.3 and 3.2 for bileaflet mechanical and porcine TVPs, respectively.2,3 Other supportive signs of severe regurgitation include valve dehiscence, large jet area by color Doppler, large vena contracta, dense CW tricuspid regurgitant jet with early peaking velocity,
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velocity, peak gradient, and mean gradient. On the basis of limited studies published to date, recommended cut-off values for normal pulmonary valve homograft conduits are peak velocity < 2.5 m/s and MG < 15 mmHg,29 while cut-off values for normal pulmonary heterografts are peak velocity < 3.2 m/s and MG < 20 mmHg.30 Doppler-derived hemodynamic data for mechanical PVPs are limited, as are data regarding calculated EOA for any type of PVP.
Diagnosing prosthetic pulmonary valve dysfunction The best method for determining PVP function is to complete a thorough 2-D examination for assessment of leaflet mobility and obtain peak velocity, peak gradient, and mean gradient in order to compare findings with values obtained on previous studies. Comparing serial estimations of right ventricular systolic pressure may also be useful for identifying PVP dysfunction. Findings suggestive of clinically significant pulmonary valve prosthetic or periprosthetic regurgitation are similar to findings consistent with severe native pulmonary valve regurgitation, including right ventricular enlargement with flattening of the interventricular septum during diastole, large regurgitant jet width, large vena contracta and depth of regurgitant jet penetration into the right ventricle. In eccentric prosthetic or periprosthetic regurgitant jets, however, Doppler-derived parameters are more challenging to assess and may be unreliable. Important indirect signs suggestive of severe regurgitation include dense CW regurgitant jet with rapid deceleration rate and diastolic flow reversal in the main pulmonary artery. Fig 3 – Algorithm for evaluating tricuspid valve prostheses with high mean gradient. Abbreviations: iEOA, indexed effective orifice area; PHT, pressure halftime; PPM, prosthesis–patient mismatch; TVI ratio, ratio of the time velocity integral of the mitral valve prosthesis to the time velocity integral of the left ventricular outflow tract.
right ventricular and right atrial dilatation, and holosystolic flow reversals in the hepatic veins. If TTE findings suggest clinically significant TVP regurgitation, TEE imaging may be necessary to confirm the TTE findings.
Conclusions Two-dimensional and Doppler echocardiography is the imaging modality of choice for evaluating prosthetic heart valve structure and function. Serial comparison of 2-D images and Doppler findings with a baseline postoperative examination is crucial for accurate assessment of prostheses. Threedimensional imaging is emerging as a technique that may provide incremental value for baseline and serial examinations.
Statement of Conflict of Interest Evaluation of pulmonary valve prostheses 2-D echocardiography Two-dimensional imaging of pulmonary valve prostheses (PVPs) can be challenging by both TTE and TEE due to their anterior–superior position in the heart. Because limited acoustic windows may limit 2-D imaging of pulmonary valve prostheses, Doppler assessment is essential.
Doppler echocardiography Suggested Doppler echocardiographic parameters for assessment of a pulmonary valve prosthesis (PVP) include peak
None.
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