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Doppler Echocardiography of Normal Starr-Edwards Mitral Prostheses: A Comprehensive Function Assessment Including Continuity Equation and Time-velocity Integral Ratio
Doppler Echocardiography of Normal Starr-Edwards Mitral Prostheses: A Comprehensive Function Assessment Including Continuity Equation and Time-velocity Integral Ratio Joseph F. Malouf, MD, Manfredi Ballo, MD, David O. Hodge, Regina M. Herges, Thomas A. Orszulak, MD, and Fletcher A. Miller Jr, MD, Rochester, Minnesota
The purpose of this study was to provide comprehensive Doppler echocardiographic assessment of the function of the normal Starr-Edwards mitral valve prosthesis using all the Doppler hemodynamic variables described to date, including the mitral valve prosthesis time-velocity integral (TVI)/ left ventricular outflow tract TVI ratio and the prosthesis performance index. All patients had a peak early mitral diastolic velocity of no more than 2 m/s or a pressure half-time that was less than 130 milli-
There are few data on the normal Doppler-derived
hemodynamic profile of the Starr-Edwards prosthesis in the mitral position. The collective experience consists of a few predominantly small series,1-5 in which Doppler measurements were limited to the peak early mitral diastolic (E) velocity, peak and mean gradients, and the effective orifice area (EOA) derived from the pressure half-time (PHT) method. Therefore, we sought to define the normal hemodynamic profile of the Starr-Edwards mitral prosthesis using all the important Doppler hemodynamic variables described to date for other mitral prostheses, including the EOA as derived from the continuity (CON) method. We also studied the correlation between in vivo Doppler-derived EOA and in vitro geometric orifice area as provided by the manufacturer.
seconds. All but one patient had either a peak early mitral diastolic velocity of no more than 2 m/s or a mitral valve prosthesis TVI/left ventricular outflow tract TVI ratio of less than 2.2, regardless of prosthesis size or left ventricular systolic function. There was a trend of decreasing prosthesis performance index with increasing prosthesis valve size that was not statistically significant, however. (J Am Soc Echocardiogr 2005;18:1399-1403.)
years or older, underwent isolated mitral valve replacement with a Starr-Edwards prosthesis between 1993 and 2002, and had a 2-dimensional (2D) Doppler echocardiographic study within 4 weeks after operation. The physical examination findings and the appearance of the prosthesis by both intraoperative transesophageal echocardiography (TEE) and follow-up transthoracic echocardiography (TTE) were normal in each patient. Routine intraoperative TEE and postoperative TTE evaluation of prosthesis function included 2D imaging of the sewing ring and the ball occluder to assess morphologic abnormalities, color flow Doppler imaging to detect flow alteration, and spectral Doppler assessment of prosthesis hemodynamics. This study was approved by the institutional review board, and all patients consented to have their medical records accessed. Doppler Echocardiographic Data
METHODS Patient Selection From the cardiac surgical database at Mayo Clinic, Rochester, Minn, we identified 47 patients who were 18 From the Divisions of Cardiovascular Diseases, Biostatistics (D.O.H., R.M.H.), and Cardiovascular Surgery (T.A.O.), Mayo Clinic. Correspondence: Joseph F. Malouf, MD, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905. 0894-7317/$30.00 Copyright 2005 by the American Society of Echocardiography. doi:10.1016/j.echo.2005.03.031
Doppler echocardiographic data were obtained from review of the postoperative TTE reports. The prosthesis EOA was measured using both the PHT method (EOA ⫽ 220/PHT) and the CON method (EOA ⫽ stroke volume/ mitral valve prosthesis [MVP] time-velocity integral [TVI]). Three sizes of Starr-Edwards valves were used: 3M, 4M, and 5M, which correspond to sewing-ring diameters of 30, 32, and 34 mm, respectively. The prosthesis performance index (PPI) was calculated as the ratio of the EOA derived from the CON method to the geometric orifice area as provided by the manufacturer6 (2.86, 3.24, and 3.66 cm2 for the 30-, 32-, and 34-mm prostheses, respectively). Other calculated variables included EOA indexed to the
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Table Overall baseline characteristics (N ⫽ 47) Characteristic
Finding*
Range
Age, y Female, No. (%) Heart rate, beats/min BSA, m2 LVEF, % LVEF ⬍ 50%, No. (%) SV LVOT, mL PHT, ms MG, mm Hg EVLCTY, m/s TVIMVP, cm EVLCTY/TVILVOT TVIMVP/TVILVOT EOA CON, cm2 EOA PHT, cm2 IEOA CON, cm2/m2 IEOA PHT, cm2/m2 EOA CON/prosth size ratio EOA PHT/prosth size ratio PPI CON
59 ⫾ 13 23 (49) 85 ⫾ 14 1.87 ⫾ 0.23 52 ⫾ 13 15 (32) 67 ⫾ 16 79 ⫾ 17 5.25 ⫾ 1.88 1.65 ⫾ 0.31 35 ⫾ 7 0.09 ⫾ 0.02 1.86 ⫾ 0.38 1.95 ⫾ 0.46 2.91 ⫾ 0.63 1.05 ⫾ 0.25 1.58 ⫾ 0.39 0.06 ⫾ 0.02 0.09 ⫾ 0.02 0.57 ⫾ 0.14
30-78 ... 59-117 1.36-2.49 20-73 ... 32-117 46-142 2-9 1.0-2.3 21-54 0.05-0.14 1.21-2.85 1.16-3.08 1.55-4.78 0.56-1.78 0.83-2.70 0.03-0.10 0.05-0.14 0.32-0.95
Figure 1 Mean mitral valve prosthesis gradient versus valve size. Error bars, Mean ⫾ 2 SD.
BSA, Body surface area; CON, continuity method; EOA, effective orifice area; EVLCTY, peak early mitral diastolic velocity; IEOA, indexed effective orifice area; LVEF, left ventricular ejection fraction; LVOT, left ventricular outflow tract; MG, mean gradient; MVP, mitral valve prosthesis; PHT, pressure half-time; PPI, prosthesis performance index; prosth, prosthesis; SV, stroke volume; TVI, time-velocity integral. *Values are mean ⫾ SD unless indicated otherwise.
body surface area, EOA/prosthesis size ratio, MVP TVI (TVIMVP)/left ventricular (LV) outflow tract (LVOT) TVI (TVILVOT) ratio, and E velocity/TVILVOT ratio. LV ejection fraction was determined by visual estimate in 42 patients (89%),7-11 by M-mode measurements in 4 patients (9%), and by 2D measurements in one patient (2%). In our laboratory we average the Doppler measurements from 3 cycles if a patient is in sinus rhythm and from 5 cycles or more if a patient is in atrial fibrillation or other irregular rhythm. Statistical Methods EOA measurements were compared between the CON and PHT methods using a paired t test. Continuous variables were compared among the 3 valve size groups using analysis of variance. Significant differences were investigated by adjusting for multiple comparisons using the Student-Newman-Keuls test.
RESULTS Baseline Clinical Characteristics
Patient characteristics are listed in the Table. The rhythm was sinus in 26 patients (55%), atrial fibrillation in 18 patients (38%), and paced or junctional in 3 patients (6%). The indications for mitral valve replacement were mitral regurgitation in 35 patients
Figure 2 Peak early mitral diastolic (E) velocity versus valve size. Error bars, Mean ⫾ 2 SD.
(74%), mitral stenosis in 3 patients (6%), and mixed stenosis and regurgitation in 9 patients (19%). Complete Doppler hemodynamic data were available for all patients. A total of 25 patients (53%) had either trivial or mild aortic regurgitation and 9 patients (19%) had trivial to mild mitral prosthesis regurgitation. Hemodynamic data, grouped by valve size, are detailed in Figures 1 through 6. The EOA and indexed EOA were significantly less (P ⬍ .001) by the CON method than by the PHT method. E velocity did not exceed 2 m/s in 45 patients (96%) and in all but one of the 15 patients with an LV ejection fraction less than 50%. PHT was less than 130 milliseconds in 46 patients (98%) and the TVIMVP/TVILVOT ratio was less than 2.2 for 37 patients (79%). In all, 46 patients (98%) had either an E velocity of no more than 2 m/s or a TVIMVP/TVILVOT ratio of less than 2.2, and all patients had an E velocity of no more than 2 m/s or a PHT of less than 130 milliseconds. A total of 25 patients (53%) had the combination of E velocity of less than 1.9 m/s,
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Figure 3 Mitral valve prosthesis (MVP) time-velocity integral (TVI)/left ventricular outflow tract (LVOT) TVI ratio versus valve size. Error bars, Mean ⫾ 2 SD.
Figure 5 Mitral valve prosthesis effective orifice area (EOA) by continuity method indexed to body surface area versus valve size. Error bars, Mean ⫾ 2 SD.
Figure 4 Mitral valve prosthesis effective orifice area (EOA) by continuity method versus valve size. Error bars, Mean ⫾ 2 SD.
Figure 6 Mitral valve prosthesis performance index versus valve size. Error bars, Mean ⫾ 2 SD.
TVIMVP/TVILVOT ratio of less than 2.2, and a PHT of less than 130 milliseconds.12 The mean mitral gradient exceeded 5 mm Hg in 21 patients (6 mm Hg in 7 patients, 7 mm Hg in 8 patients, 8 mm Hg in 4 patients, and 9 mm Hg in 2 patients). Among these patients, E velocity did not exceed 2 m/s in 19 patients (90%), the heart rate was 90/min or more in 9 patients (43%), and 18 patients (86%) had a TVIMVP/TVILVOT ratio of less than 2.2 (15 patients), an LV ejection fraction of less than 50% (9 patients), or both. Effect of Prosthesis Size
Valve size was 30 mm (3M) in 5 patients, 32 mm (4M) in 20 patients, and 34 mm (5M) in 22 patients. Among the 3 valve size groups, after adjusting for multiple comparisons, there was no significant difference in the mean measurements of the mitral gradient, PHT, TVIMVP/TVILVOT ratio, E velocity/
TVILVOT ratio, EOA, indexed EOA, and EOA/prosthesis size ratio by either the CON or the PHT methods. The mean PPI decreased with increasing valve size, but the difference was not significant among the 3 valve sizes (0.62 ⫾ 0.19, 0.60 ⫾ 0.16, and 0.54 ⫾ 0.1 for the 30-, 32-, and 34-mm valves, respectively).
DISCUSSION The purpose of this study was to provide comprehensive Doppler echocardiographic assessment of the function of the normal Starr-Edwards prosthesis in the mitral position. All patients had an E velocity of no more than 2 m/s or a PHT of less than 130 milliseconds, and all but one patient had either an E velocity of no more than 2 m/s or a TVIMVP/TVILVOT ratio of less than 2.2 regardless of prosthesis size or LV systolic function. EOA measurements for Starr-Edwards mitral prostheses were significantly larger with the PHT
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method than with the CON method, which is analogous to reports on normal St Jude Medical mitral prosthesis function.13,14 The observed discrepancy between these two methods of measurement of the EOA is, therefore, most likely a limitation of the PHT method and not caused by the flow dynamics of a specific type of prosthesis. Dumesnil et al15 showed that EOA as determined by the CON method–not by the PHT method– correlates better with the in vitro EOA of normal mitral bioprostheses and that determination of EOA by the PHT method tends to grossly overestimate the in vitro EOA. The largest single-center study on normal StarrEdwards mitral prosthesis function, by Nihoyannopoulos et al,4 included 130 prostheses (valve size range, 28-34 mm) but was limited to measurements of E velocity, peak pressure gradient, and PHT. The EOA was not calculated and the number of patients with each valve size was not specified. In that study the mean of the E velocities was 1.6 ⫾ 0.34 m/s (range, 0.85-2.5 m/s) and was not significantly different among the 30-, 32-, and 34-mm valves. Lefebvre et al5 studied the Doppler profile of 25 normal Starr-Edwards mitral prostheses at a mean of 52 months after implantation. The valve sizes ranged from 30 to 34 mm, but only two patients had a 34-mm valve. The E velocity ranged from 0.9 to 2.8 m/s and the mean gradient ranged from 0.9 to 9.7 mm Hg. For the 25 patients, the mean E velocity was 1.7 ⫾ 0.3 m/s, the mean of the mean gradients was 5.3 ⫾ 2.2 mm Hg, the mean PHT was 120 ⫾ 30 milliseconds, and the mean EOA by the PHT method was 1.96 ⫾ 0.45 cm2. There were no significant differences in the mean measurements of these Doppler-derived variables between the 30- and 32-mm valves. The TVIMVP can be increased by obstruction, regurgitation, or increased cardiac output. With increased cardiac output, the TVILVOT is also increased. Fernandes et al12 were first to propose the TVIMVP/TVILVOT ratio as an important clue to mechanical prosthesis obstruction or regurgitation. They found the combination of E velocity of less than 1.9 m/s, TVIMVP/TVILVOT ratio of less than 2.2, and PHT of less than 130 milliseconds to be highly predictive of normal prosthesis function, verified by TEE, with less than 2% probability of valve dysfunction. The majority of prostheses studied were bileaflet prostheses and only 8% were caged-ball valves. In contrast, only half of the patients in our study had all 3 of these characteristics. The PPI is a measure of how much of the primary orifice area of the prosthesis is used for flow. This serves to compare the performance of valves of different sizes. In our study, the mean PPI was higher than previously reported with in vitro and catheter-based in vivo measurements in a small number of cases.6 There also was a trend of decreas-
Journal of the American Society of Echocardiography December 2005
ing mean PPI with increasing prosthesis size that did not reach statistical significance, however. A possible explanation for this observed trend is that higher flow rates across smaller Starr-Edwards prostheses may have contributed to a more sustained opening of the ball occluder, thus resulting in a higher PPI than with larger prostheses, as postulated for St Jude Medical mitral prostheses. More data are needed, however. Study Limitations This was a retrospective study of normal functioning prostheses based on normal physical examination findings, the short interval between implantation and TTE, and the normal 2D and color flow Doppler appearance of the prostheses by both intraoperative and postoperative TTE. Although we think it is unlikely, hemodynamically significant mitral regurgitation may have been overlooked in a few of these patients by use of these screening criteria. It was impossible to be certain that the lengths of the cardiac cycle that were used for LVOT and mitral flow measurements were matched for patients with atrial fibrillation. However, with measurement of multiple cycles in such patients, errors from varying R-R intervals are unlikely. Conclusions Ascertaining normal heart prosthesis function is a challenge. Our data provide an in vivo reference for the normal performance expected of the Starr-Edwards mitral prosthesis, which includes all the important Doppler hemodynamic variables described to date. Outlier data should prompt further evaluation, including TEE, for possible prosthesis dysfunction. In particular, PHT of 130 milliseconds or more warrants TEE to evaluate occluder motion and to check for thrombus or pannus. Either an E velocity greater than 2 m/s or a TVIMVP/TVILVOT ratio of 2.2 or more in the presence of a PHT of less than 130 milliseconds warrants consideration of TEE to evaluate for significant prosthetic or periprosthetic regurgitation.
REFERENCES 1. Williams GA, Labovitz AJ. Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Bjork-Shiley) and bioprosthetic (Hancock and Carpentier-Edwards) cardiac valves. Am J Cardiol 1985;56:325-32. 2. Pandidis IP, Ross J, Mitz GS. Normal and abnormal prosthetic valve function as assessed by Doppler echocardiography. J Am Coll Cardiol 1986;8:317-26. 3. Chambers J, Jackson G, Jewitt D. Limitations of Doppler ultrasound in the assessment of the function of prosthetic mitral valves. Br Heart J 1990;63:189-94. 4. Nihoyannopoulos P, Kambouroglou D, Athanassopoulos G, Nadazdin A, Smith P, Oakley CM. Doppler hemodynamic
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5.
6.
7.
8.
9.
10.
profiles of clinically and echocardiographically normal mitral and aortic valve prostheses. Eur Heart J 1992;13:348-55. Lefebvre E, Isorni C, Rey JL, Lesbre JP. Echo-Doppler evaluation of normal Starr-Edwards prostheses in mitral and aortic position [in French]. Arch Mal Coeur Vaiss 1987;80:1105-14. Rashtian MY, Stevenson DM, Allen DT, Yoganathan AP, Harrison EC, Edmiston WA, et al. Flow characteristics of four commonly used mechanical heart valves. Am J Cardiol 1986; 58:743-52. Stamm RB, Carabello BA, Mayers DL, Martin RP. Twodimensional echocardiographic measurement of left ventricular ejection fraction: prospective analysis of what constitutes an adequate determination. Am Heart J 1982;104:136-44. Rich S, Sheikh A, Gallastegui J, Kondos GT, Mason T, Lam W. Determination of left ventricular ejection fraction by visual estimation during real-time two-dimensional echocardiography. Am Heart J 1982;104:603-6. Amico AF, Lichtenberg GS, Reisner SA, Stone CK, Schwartz RG, Meltzer RS. Superiority of visual versus computerized echocardiographic estimation of radionuclide left ventricular ejection fraction. Am Heart J 1989;118:1259-65. Mueller X, Stauffer JC, Jaussi A, Goy JJ, Kappenberger L. Subjective visual echocardiographic estimate of left ventricular ejection fraction as an alternative to conventional echocardio-
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11.
12.
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15.
graphic methods: comparison with contrast angiography. Clin Cardiol 1991;14:898-902. Enriquez-Sarano M, Tajik AJ, Schaff HV, Orszulak TA, Bailey KR, Frye RL. Echocardiographic prediction of survival after surgical correction of organic mitral regurgitation. Circulation 1994;90:830-7. Fernandes V, Olmos L, Nagueh SF, Quinones MA, Zoghbi WA. Peak early diastolic velocity rather than pressure half-time is the best index of mechanical prosthetic mitral valve function. Am J Cardiol 2002;89:704-10. Bitar JN, Lechin ME, Salazar G, Zoghbi WA. Doppler echocardiographic assessment with the continuity equation of St Jude Medical mechanical prostheses in mitral valve position [published correction appears in Am J Cardiol 1995;76:642]. Am J Cardiol 1995;76:287-93. Malouf JF, Ballo M, Connolly HM, Hodge DO, Herges RM, Mullany CJ, et al. Doppler echocardiography of 119 normalfunctioning St Jude medical mitral valve prostheses: a comprehensive assessment including time-velocity integral ratio and prosthesis performance index. J Am Soc Echocardiogr 2005; 18:252-6. Dumesnil JG, Honos GN, Lemieux M, Beauchemin J. Validation and applications of mitral prosthetic valvular areas calculated by Doppler echocardiography. Am J Cardiol 1990; 65:1443-8.
The purpose of this study was to provide comprehensive Doppler echocardiographic assessment of the function of the normal Starr-Edwards mitral valve prosthesis using all the Doppler hemodynamic variables described to date, including the mitral valve prosthesis time-velocity integral (TVI)/ left ventricular outflow tract TVI ratio and the prosthesis performance index. All patients had a peak early mitral diastolic velocity of no more than 2 m/s or a pressure half-time that was less than 130 milli-
There are few data on the normal Doppler-derived
hemodynamic profile of the Starr-Edwards prosthesis in the mitral position. The collective experience consists of a few predominantly small series,1-5 in which Doppler measurements were limited to the peak early mitral diastolic (E) velocity, peak and mean gradients, and the effective orifice area (EOA) derived from the pressure half-time (PHT) method. Therefore, we sought to define the normal hemodynamic profile of the Starr-Edwards mitral prosthesis using all the important Doppler hemodynamic variables described to date for other mitral prostheses, including the EOA as derived from the continuity (CON) method. We also studied the correlation between in vivo Doppler-derived EOA and in vitro geometric orifice area as provided by the manufacturer.
seconds. All but one patient had either a peak early mitral diastolic velocity of no more than 2 m/s or a mitral valve prosthesis TVI/left ventricular outflow tract TVI ratio of less than 2.2, regardless of prosthesis size or left ventricular systolic function. There was a trend of decreasing prosthesis performance index with increasing prosthesis valve size that was not statistically significant, however. (J Am Soc Echocardiogr 2005;18:1399-1403.)
years or older, underwent isolated mitral valve replacement with a Starr-Edwards prosthesis between 1993 and 2002, and had a 2-dimensional (2D) Doppler echocardiographic study within 4 weeks after operation. The physical examination findings and the appearance of the prosthesis by both intraoperative transesophageal echocardiography (TEE) and follow-up transthoracic echocardiography (TTE) were normal in each patient. Routine intraoperative TEE and postoperative TTE evaluation of prosthesis function included 2D imaging of the sewing ring and the ball occluder to assess morphologic abnormalities, color flow Doppler imaging to detect flow alteration, and spectral Doppler assessment of prosthesis hemodynamics. This study was approved by the institutional review board, and all patients consented to have their medical records accessed. Doppler Echocardiographic Data
METHODS Patient Selection From the cardiac surgical database at Mayo Clinic, Rochester, Minn, we identified 47 patients who were 18 From the Divisions of Cardiovascular Diseases, Biostatistics (D.O.H., R.M.H.), and Cardiovascular Surgery (T.A.O.), Mayo Clinic. Correspondence: Joseph F. Malouf, MD, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St SW, Rochester, MN 55905. 0894-7317/$30.00 Copyright 2005 by the American Society of Echocardiography. doi:10.1016/j.echo.2005.03.031
Doppler echocardiographic data were obtained from review of the postoperative TTE reports. The prosthesis EOA was measured using both the PHT method (EOA ⫽ 220/PHT) and the CON method (EOA ⫽ stroke volume/ mitral valve prosthesis [MVP] time-velocity integral [TVI]). Three sizes of Starr-Edwards valves were used: 3M, 4M, and 5M, which correspond to sewing-ring diameters of 30, 32, and 34 mm, respectively. The prosthesis performance index (PPI) was calculated as the ratio of the EOA derived from the CON method to the geometric orifice area as provided by the manufacturer6 (2.86, 3.24, and 3.66 cm2 for the 30-, 32-, and 34-mm prostheses, respectively). Other calculated variables included EOA indexed to the
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Table Overall baseline characteristics (N ⫽ 47) Characteristic
Finding*
Range
Age, y Female, No. (%) Heart rate, beats/min BSA, m2 LVEF, % LVEF ⬍ 50%, No. (%) SV LVOT, mL PHT, ms MG, mm Hg EVLCTY, m/s TVIMVP, cm EVLCTY/TVILVOT TVIMVP/TVILVOT EOA CON, cm2 EOA PHT, cm2 IEOA CON, cm2/m2 IEOA PHT, cm2/m2 EOA CON/prosth size ratio EOA PHT/prosth size ratio PPI CON
59 ⫾ 13 23 (49) 85 ⫾ 14 1.87 ⫾ 0.23 52 ⫾ 13 15 (32) 67 ⫾ 16 79 ⫾ 17 5.25 ⫾ 1.88 1.65 ⫾ 0.31 35 ⫾ 7 0.09 ⫾ 0.02 1.86 ⫾ 0.38 1.95 ⫾ 0.46 2.91 ⫾ 0.63 1.05 ⫾ 0.25 1.58 ⫾ 0.39 0.06 ⫾ 0.02 0.09 ⫾ 0.02 0.57 ⫾ 0.14
30-78 ... 59-117 1.36-2.49 20-73 ... 32-117 46-142 2-9 1.0-2.3 21-54 0.05-0.14 1.21-2.85 1.16-3.08 1.55-4.78 0.56-1.78 0.83-2.70 0.03-0.10 0.05-0.14 0.32-0.95
Figure 1 Mean mitral valve prosthesis gradient versus valve size. Error bars, Mean ⫾ 2 SD.
BSA, Body surface area; CON, continuity method; EOA, effective orifice area; EVLCTY, peak early mitral diastolic velocity; IEOA, indexed effective orifice area; LVEF, left ventricular ejection fraction; LVOT, left ventricular outflow tract; MG, mean gradient; MVP, mitral valve prosthesis; PHT, pressure half-time; PPI, prosthesis performance index; prosth, prosthesis; SV, stroke volume; TVI, time-velocity integral. *Values are mean ⫾ SD unless indicated otherwise.
body surface area, EOA/prosthesis size ratio, MVP TVI (TVIMVP)/left ventricular (LV) outflow tract (LVOT) TVI (TVILVOT) ratio, and E velocity/TVILVOT ratio. LV ejection fraction was determined by visual estimate in 42 patients (89%),7-11 by M-mode measurements in 4 patients (9%), and by 2D measurements in one patient (2%). In our laboratory we average the Doppler measurements from 3 cycles if a patient is in sinus rhythm and from 5 cycles or more if a patient is in atrial fibrillation or other irregular rhythm. Statistical Methods EOA measurements were compared between the CON and PHT methods using a paired t test. Continuous variables were compared among the 3 valve size groups using analysis of variance. Significant differences were investigated by adjusting for multiple comparisons using the Student-Newman-Keuls test.
RESULTS Baseline Clinical Characteristics
Patient characteristics are listed in the Table. The rhythm was sinus in 26 patients (55%), atrial fibrillation in 18 patients (38%), and paced or junctional in 3 patients (6%). The indications for mitral valve replacement were mitral regurgitation in 35 patients
Figure 2 Peak early mitral diastolic (E) velocity versus valve size. Error bars, Mean ⫾ 2 SD.
(74%), mitral stenosis in 3 patients (6%), and mixed stenosis and regurgitation in 9 patients (19%). Complete Doppler hemodynamic data were available for all patients. A total of 25 patients (53%) had either trivial or mild aortic regurgitation and 9 patients (19%) had trivial to mild mitral prosthesis regurgitation. Hemodynamic data, grouped by valve size, are detailed in Figures 1 through 6. The EOA and indexed EOA were significantly less (P ⬍ .001) by the CON method than by the PHT method. E velocity did not exceed 2 m/s in 45 patients (96%) and in all but one of the 15 patients with an LV ejection fraction less than 50%. PHT was less than 130 milliseconds in 46 patients (98%) and the TVIMVP/TVILVOT ratio was less than 2.2 for 37 patients (79%). In all, 46 patients (98%) had either an E velocity of no more than 2 m/s or a TVIMVP/TVILVOT ratio of less than 2.2, and all patients had an E velocity of no more than 2 m/s or a PHT of less than 130 milliseconds. A total of 25 patients (53%) had the combination of E velocity of less than 1.9 m/s,
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Figure 3 Mitral valve prosthesis (MVP) time-velocity integral (TVI)/left ventricular outflow tract (LVOT) TVI ratio versus valve size. Error bars, Mean ⫾ 2 SD.
Figure 5 Mitral valve prosthesis effective orifice area (EOA) by continuity method indexed to body surface area versus valve size. Error bars, Mean ⫾ 2 SD.
Figure 4 Mitral valve prosthesis effective orifice area (EOA) by continuity method versus valve size. Error bars, Mean ⫾ 2 SD.
Figure 6 Mitral valve prosthesis performance index versus valve size. Error bars, Mean ⫾ 2 SD.
TVIMVP/TVILVOT ratio of less than 2.2, and a PHT of less than 130 milliseconds.12 The mean mitral gradient exceeded 5 mm Hg in 21 patients (6 mm Hg in 7 patients, 7 mm Hg in 8 patients, 8 mm Hg in 4 patients, and 9 mm Hg in 2 patients). Among these patients, E velocity did not exceed 2 m/s in 19 patients (90%), the heart rate was 90/min or more in 9 patients (43%), and 18 patients (86%) had a TVIMVP/TVILVOT ratio of less than 2.2 (15 patients), an LV ejection fraction of less than 50% (9 patients), or both. Effect of Prosthesis Size
Valve size was 30 mm (3M) in 5 patients, 32 mm (4M) in 20 patients, and 34 mm (5M) in 22 patients. Among the 3 valve size groups, after adjusting for multiple comparisons, there was no significant difference in the mean measurements of the mitral gradient, PHT, TVIMVP/TVILVOT ratio, E velocity/
TVILVOT ratio, EOA, indexed EOA, and EOA/prosthesis size ratio by either the CON or the PHT methods. The mean PPI decreased with increasing valve size, but the difference was not significant among the 3 valve sizes (0.62 ⫾ 0.19, 0.60 ⫾ 0.16, and 0.54 ⫾ 0.1 for the 30-, 32-, and 34-mm valves, respectively).
DISCUSSION The purpose of this study was to provide comprehensive Doppler echocardiographic assessment of the function of the normal Starr-Edwards prosthesis in the mitral position. All patients had an E velocity of no more than 2 m/s or a PHT of less than 130 milliseconds, and all but one patient had either an E velocity of no more than 2 m/s or a TVIMVP/TVILVOT ratio of less than 2.2 regardless of prosthesis size or LV systolic function. EOA measurements for Starr-Edwards mitral prostheses were significantly larger with the PHT
1402 Malouf et al
method than with the CON method, which is analogous to reports on normal St Jude Medical mitral prosthesis function.13,14 The observed discrepancy between these two methods of measurement of the EOA is, therefore, most likely a limitation of the PHT method and not caused by the flow dynamics of a specific type of prosthesis. Dumesnil et al15 showed that EOA as determined by the CON method–not by the PHT method– correlates better with the in vitro EOA of normal mitral bioprostheses and that determination of EOA by the PHT method tends to grossly overestimate the in vitro EOA. The largest single-center study on normal StarrEdwards mitral prosthesis function, by Nihoyannopoulos et al,4 included 130 prostheses (valve size range, 28-34 mm) but was limited to measurements of E velocity, peak pressure gradient, and PHT. The EOA was not calculated and the number of patients with each valve size was not specified. In that study the mean of the E velocities was 1.6 ⫾ 0.34 m/s (range, 0.85-2.5 m/s) and was not significantly different among the 30-, 32-, and 34-mm valves. Lefebvre et al5 studied the Doppler profile of 25 normal Starr-Edwards mitral prostheses at a mean of 52 months after implantation. The valve sizes ranged from 30 to 34 mm, but only two patients had a 34-mm valve. The E velocity ranged from 0.9 to 2.8 m/s and the mean gradient ranged from 0.9 to 9.7 mm Hg. For the 25 patients, the mean E velocity was 1.7 ⫾ 0.3 m/s, the mean of the mean gradients was 5.3 ⫾ 2.2 mm Hg, the mean PHT was 120 ⫾ 30 milliseconds, and the mean EOA by the PHT method was 1.96 ⫾ 0.45 cm2. There were no significant differences in the mean measurements of these Doppler-derived variables between the 30- and 32-mm valves. The TVIMVP can be increased by obstruction, regurgitation, or increased cardiac output. With increased cardiac output, the TVILVOT is also increased. Fernandes et al12 were first to propose the TVIMVP/TVILVOT ratio as an important clue to mechanical prosthesis obstruction or regurgitation. They found the combination of E velocity of less than 1.9 m/s, TVIMVP/TVILVOT ratio of less than 2.2, and PHT of less than 130 milliseconds to be highly predictive of normal prosthesis function, verified by TEE, with less than 2% probability of valve dysfunction. The majority of prostheses studied were bileaflet prostheses and only 8% were caged-ball valves. In contrast, only half of the patients in our study had all 3 of these characteristics. The PPI is a measure of how much of the primary orifice area of the prosthesis is used for flow. This serves to compare the performance of valves of different sizes. In our study, the mean PPI was higher than previously reported with in vitro and catheter-based in vivo measurements in a small number of cases.6 There also was a trend of decreas-
Journal of the American Society of Echocardiography December 2005
ing mean PPI with increasing prosthesis size that did not reach statistical significance, however. A possible explanation for this observed trend is that higher flow rates across smaller Starr-Edwards prostheses may have contributed to a more sustained opening of the ball occluder, thus resulting in a higher PPI than with larger prostheses, as postulated for St Jude Medical mitral prostheses. More data are needed, however. Study Limitations This was a retrospective study of normal functioning prostheses based on normal physical examination findings, the short interval between implantation and TTE, and the normal 2D and color flow Doppler appearance of the prostheses by both intraoperative and postoperative TTE. Although we think it is unlikely, hemodynamically significant mitral regurgitation may have been overlooked in a few of these patients by use of these screening criteria. It was impossible to be certain that the lengths of the cardiac cycle that were used for LVOT and mitral flow measurements were matched for patients with atrial fibrillation. However, with measurement of multiple cycles in such patients, errors from varying R-R intervals are unlikely. Conclusions Ascertaining normal heart prosthesis function is a challenge. Our data provide an in vivo reference for the normal performance expected of the Starr-Edwards mitral prosthesis, which includes all the important Doppler hemodynamic variables described to date. Outlier data should prompt further evaluation, including TEE, for possible prosthesis dysfunction. In particular, PHT of 130 milliseconds or more warrants TEE to evaluate occluder motion and to check for thrombus or pannus. Either an E velocity greater than 2 m/s or a TVIMVP/TVILVOT ratio of 2.2 or more in the presence of a PHT of less than 130 milliseconds warrants consideration of TEE to evaluate for significant prosthetic or periprosthetic regurgitation.
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