Ann Thorac Surg 2001;71:S285-S288
© 2001 The Society of Thoracic Surgeons
Bioprosthetic valves and conduits: new developments
Short-term hemodynamic performance of the mitral Carpentier-Edwards PERIMOUNT pericardial valve
Michael S. Firstenberg, MDa,
Annitta J. Morehead, BAa,b,c,d,
James D. Thomas, MDa,
Nicholas G. Smedira, MDa,b,c,d,
Delos M. Cosgrove, III, MDa,b,c,d,
Michel A. Marchand, MDa,b,c,d,
for the Carpentier-Edwards PERIMOUNT Investigators,1
a Department of Cardiology, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
b Department of Cardiovascular Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
c Department of Cardiology, Hôpital Trousseau, Tours, France
d Department of Cardiovascular Surgery, Hôpital Trousseau, Tours, France
Address reprint requests to Dr Thomas, Department of Cardiology, The Cleveland Clinic Foundation, Desk F15, 9500 Euclid Ave, Cleveland, OH 44195
e-mail: thomasj{at}ccf.org
Presented at the VIII International Symposium on Cardiac Bioprostheses, Cancun, Mexico, Nov 3–5, 2000.
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Abstract
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Background. Although long-term durability data exist, little data are available concerning the hemodynamic performance of the Carpentier-Edwards PERIMOUNT pericardial valve in the mitral position.
Methods. Sixty-nine patients who were implanted with mitral PERIMOUNT valves at seven international centers between January 1996 and February 1997 consented to participate in a short-term echocardiography follow-up. Echocardiographs were collected at a mean of 600 ± 133 days after implantation (range, 110 to 889 days); all underwent blinded core lab analysis.
Results. At follow-up, peak gradients were 9.09 ± 3.43 mm Hg (mean, 4.36 ± 1.79 mm Hg) and varied inversely with valve size (p < 0.05). The effective orifice areas were 2.5 ± 0.6 cm2 and tended to increase with valve size (p = 0.08). Trace mitral regurgitation (MR) was common (n = 48), 9 patients had mild MR, 1 had moderate MR, none had severe MR. All MR was central (n = 55) or indeterminate (n = 3). No paravalvular leaks were observed. Mitral regurgitation flow areas were 3.4 ± 2.8 cm2 and were without significant volumes.
Conclusions. In this multicenter study, these mitral valves are associated with trace, although physiologically insignificant, central MR. Despite known echocardiographic limitations, the PERIMOUNT mitral valves exhibit similar hemodynamics to other prosthetic valves.
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Introduction
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The durability of early pericardial valves was limited by design problems and tissue preparation rather than by complications related to the use of pericardium [1]. These limitations prompted the design of the Carpentier-Edwards (CE) PERIMOUNT pericardial bioprosthesis (Edwards Lifesciences LLC, Irvine, CA). Subsequently, the long-term structural durability, patient survival, and freedom from valve-related complications have been demonstrated for the CE PERIMOUNT in both the aortic and mitral positions. Despite extensive surgical experiences, the hemodynamic profile of this valve has not been documented. As required for approval for use in the United States by the U.S. Food and Drug Administration, we explored the interim hemodynamic profile and incidence of valvular regurgitation in patients undergoing mitral valve replacement with a CE PERIMOUNT pericardial valve, with the additional goal of establishing a reference standard to facilitate long-term follow-up.
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Material and methods
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The CE PERIMOUNT mitral pericardial bioprosthesis, model 6900, has been available in Europe and Canada for implantation since 1984. All patients retrospectively identified as having a mitral PERIMOUNT valve implanted between January 1996 and February 1997 at seven international investigational centers were asked to participate in an elective transthoracic echocardiographic examination of their valve. Of the 157 patients available, 76 patients agreed to participate. Reasons for not participating included death (n = 34), explant (n = 2), inability or unwillingness to return to the study center for assessment (n = 26), and lost to follow-up (n = 19).
There were 17 operative (none valve-related) and 17 late deaths (7 valve-related; thromboembolism in 2 and unknown in 5, which were conservatively classified as valve-related). The two explants were caused by endocarditis (n = 1) and hemolytic anemia (n = 1). Demographic data for nonparticipating patients were similar to those for patients who did participate in the study. Seven echocardiographic tapes were unreadable, possibly having been erased during transit. Of the remaining 69 patients, echocardiographs were collected at a mean follow-up time of 600 ± 133 days after implantation (range, 110 to 889 days). All following results are based on these 69 patients.
Echocardiographic studies
After informed consent, each patient underwent a routine transthoracic two-dimensional and Doppler echocardiographic evaluation at the institution at which the valve was implanted. Studies were stored on super-VHS videotape with the original tapes sent to a centralized core lab at the Cleveland Clinic for review and analysis. All interpretations were performed by an experienced sonographer (A.J.M.) and reviewed by an experienced echo-cardiologist (J.D.T.) with both blinded to patient demographic and implant data.
Core lab analyses included stroke volumes and ejection fraction determined from the apical four-chamber view. Continuous-wave Doppler interrogation of the mitral valve was performed, using either the two-chamber or four-chamber view for measurement of the pressure half-time (t1/2). Peak and mean transmitral pressure gradients were determined by the simplified Bernoulli equation (
p = 4v2, where p = pressure and v = velocity from Doppler echocardiography). The mitral valve area (MVA) was calculated using the t1/2 method (MVA - t1/2 = 220/t1/2), whereas the effective orifice area (EOA) was determined by dividing the stroke volume by the time velocity integral of the transmitral diastolic velocity profile. All measurements were obtained from the average of one to five consecutive representative cardiac cycles.
From the apical four-chamber view, when found, the mitral regurgitant (MR) color jet area was traced along the outer border and its origin was identified. A semiquantitative assessment was determined by an expert reviewer (J.D.T.) by integrating jet size, morphology, and continuous-wave Doppler characteristics. Consistent with our core lab reviewing protocol, trace MR was defined as any evidence of regurgitant flow, even if only a single pixel was identified. This overly sensitive method of defining MR allows for standardization of MR identification and quantification, although this method often results in identification of MR that would otherwise be considered normal or physiologically insignificant. Attempts to quantify the regurgitant orifice size were performed using the proximal isovelocity convergence zone [2].
Statistics
All statistics were performed using Systat 9.0 for Windows (SPSS, Inc, Chicago IL). Continuous variables were compared using Student’s t tests for paired and unpaired data when appropriate. One-way repeated measures analysis of variance was used for grouped data obtained for each valve size. Simple least squared linear regression was used to test the association between continuous variables. A p less than 0.05 was considered statistically significant (All values are mean ± standard deviation).
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Results
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The mean age at implantation was 72.3 ± 5.5 years, and there were 36 men (53%). Preoperatively, 84% of the patients were in New York Heart Association class III or IV. Indications for valve operation included calcification (23%), rheumatic disease (22%), degenerative disease (12%), and other (congenital, remote endocarditis, ischemic; 43%). The most common valve sizes implanted were 27 mm (n = 14), 29 mm (n = 26), and 31 mm (n = 31). Summary hemodynamic results are listed in Table 1.
Valvular gradients
Figure 1 demonstrates the relationship between valve sizes and gradients (peak and mean). For all valves the peak early diastolic gradients were 9.09 ± 3.43 mm Hg (peak velocities were 1.46 ± 0.29 m/s). There was an inverse relationship between valve size and peak gradients (p < 0.05), but the limited number of 25-mm and 33-mm valve sizes (n = 3 and n = 4, respectively) precluded determining a linear correlation. Additionally, the mean gradients were 4.36 ± 1.79 mm Hg, but no relationship was observed between valve size and the mean gradient. Peak gradients were more than 10 mm Hg in 16 patients whereas mean gradients were more than 5 mm Hg in 17 patients.
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Fig 1. Relationship between valve sewing ring size and Doppler-derived peak and mean pressure gradients.
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The EOA was 2.5 ± 0.6 cm2, and overall there was a trend toward larger EOAs with increasing valve size (p = 0.08; Fig 2). For all valves, MVA - t1/2 was 2.5 ± 0.6 cm2 (t1/2 = 110 ± 72 ms). The EOA and MVA - t1/2 were correlated (y = 0.92x + 0.1; r = 0.79; p < 0.001) with both linearly related to valve size (p < 0.05 for both). However, no correlation was observed between the EOA and either the peak (Fig 3) or mean calculated pressure gradient. Furthermore, the EOA for valves with higher peak gradients (> 9 mm Hg; EOA, 2.39 ± 0.58 cm2) was not significantly different from the EOA for valves with lower peak gradients (< 9 mm Hg; EOA, 2.56 ± 0.67 cm2; p = 0.31). Higher gradients tended to be associated with smaller MVA - t1/2 areas (> 9 mm Hg; MVA - t1/2, 2.19 ± 0.71 cm2) than valves with lower gradients (< 9 mm Hg; MVA - t1/2, 2.50 ± 0.75 cm2), but this difference was not statistically significant (p = 0.11). Similarly, valves with small EOAs (< 2 cm2) were not associated with higher gradients (peak, 10.2 ± 2.8 mm Hg; mean, 4.7 ± 1.5 mm Hg) than valves with larger EOA (> 2 cm2; peak, 8.7 ± 3.6 mm Hg; mean, 4.2 ± 1.9 mm Hg; both p = not significant versus valves with EOA < 2 cm2).
Valvular regurgitation
Fifty-eight regurgitant jets were detected in 57 patients (83%) with 48 classified as trace MR (84% of all MR), 9 (16%) as mild, and 1 (1.7%) as moderate. None had severe MR. Mitral regurgitation jet location was central in 55 and indeterminate in 3. (One patient had both a central and indeterminate MR jet.) No paravalvular jets were detected. In the valves that exhibited MR, the color flow area could be measured in 43 patients and ranged from 0.9 to 14.4 cm2 (mean ± standard deviation, 3.39 ± 2.86 cm2). The remaining 15 patients did not have adequate two-dimensional color images for jet area determination; however, these patients all exhibited trace MR. When categorized by valve size, measurable jet areas were obtained in one 25-mm valve (0.9 cm2), in two 33-mm valves (1.0 and 5.1 cm2), in six 27-mm valves (2.4 ± 0.7 cm2), in 16 29-mm valves (3.3 ± 3.4 cm2), and in 17 31-mm valves (4.1 ± 2.8 cm2). No relation was found between MR jet area and valve size (p = 0.45). None of the jets exhibited a proximal isovelocity convergence zone, and all were considered physiologically insignificant.
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Comment
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Our prospective echocardiographic evaluation of 69 patients from seven international centers who underwent mitral valve replacement with a CE PERIMOUNT pericardial valve demonstrates favorable transvalvular pressure gradient hemodynamics. Furthermore, the hemodynamic profiles observed do not differ greatly with valve size—suggesting favorable hemodynamic characteristics regardless of valve size, an issue of particular importance when smaller size valves are required. In addition, the lack of significant incidence of mitral regurgitation also demonstrates a clinical benefit during the follow-up period.
Of further interest is the lack of a correlation between the pressure gradients and the EOA. This discrepancy reflects some of the inherent limitations of noninvasive Doppler echocardiographic techniques. Valvular gradients are typically calculated using the simplified Bernoulli equation. This simplified relationship between blood velocity and pressure gradient across a valve does not take into consideration the inertial and resistive components of transvalvular flow. Although these assumptions may be valid in clinical scenarios of high velocity or low flow, such as in mitral stenosis, in which the inertial forces are assumed to be minimal in comparison with the convective forces, this is not necessarily valid for nonstenotic valves [3]. Despite the importance of the inertial contribution [4] to transmitral pressure gradients, the simplified Bernoulli equation continues to be used as the gold standard for noninvasive transvalvular gradients.
In addition, reliance on the t1/2 technique for estimating valve area can also be misleading. The empirical equation relating the t1/2 to valve area is based on extensive clinical observations—again, typically with mitral stenosis. Despite clinical validation and widespread application [5], in vivo, in vitro, and numerical modeling studies have demonstrated its limitations and inaccuracies in the setting of poor left ventricular compliance and atrial fibrillation, and in elderly patients [6]. Nevertheless, this method is also used extensively for assessing prosthetic valves. It was gratifying that in this series, a correlation was found between t1/2 and continuity EOA techniques (r = 0.79).
Finally, although MR jets were common in our series, most were trivial in magnitude, size, and velocity, and overall were predominantly central in origin. Combined with the lack of a proximal isovelocity convergence zone, this further supports the trivial nature of these MR jets and most likely reflects the typically physiologically insignificant MR associated with all prosthetic valves [7]. This finding also reflects our overly sensitive definition of identifying MR.
Comparison with previous studies of prosthetic valves is difficult as most literature on valve gradients and effective orifice sizes do not always consider the variability in these measurements for different size valves. Previous studies investigating different prosthetic valves have demonstrated similar results. For mechanical valves, there exists a wide range of reported average gradients (mean, 2.7 to 5.0 mm Hg; peak, 8.7 to 15 mm Hg) and areas (range by t1/2, 1.6 to 3.8 cm2). Similarly, for tissue valves, average gradients also ranged widely (mean, 2.6 to 7.5 mm Hg; peak, 9.7 to 17.3 mm Hg) as did valve areas (1.7 to 2.6 cm2). Overall, these studies showed little correlation between valve areas and gradients with sewing ring sizes. Nevertheless, the results obtained in our study demonstrate similar gradients and calculated valve areas to those obtained from other types of prosthetic mitral valves.
After an average of 2 years of follow-up, the hemodynamic profiles of the CE PERIMOUNT pericardial mitral prosthesis, regardless of valve size, are similar to other tissue valves. Furthermore, the freedom from significant MR also demonstrates the lack of early structural or functional concerns. These results can be used as a standard for further studies evaluating the long-term hemodynamic performance and to assist in the routine assessment of patients having undergone implantation with a CE PERIMOUNT mitral valve.
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Acknowledgments
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Edwards Lifesciences LLC provided financial support for this project. Financial support was also provided by Grant-in-aid #NEO-97–225-BGIA from the American Heart Association, North-East Ohio Affiliate, National Aeronautics Space Administration Grant # NCC9–60, Houston, TX, and National Institutes of Health grant # ROI HL56688–01A1, Bethesda, MD.
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Footnotes
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Dr Cosgrove discloses that he has a financial relationship with Edwards Lifesciences LLC.
1 A complete list of the Carpentier-Edwards PERIMOUNT Investigators appears in the appendix. 
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Appendix
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The Carpentier-Edwards PERIMOUNT investigators
Institution
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Investigators
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| The Cleveland Clinic Foundation Cleveland, Ohio (Core Lab) |
Michael S. Firstenberg, MD |
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Annitta J. Morehead, BA |
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James D. Thomas, MD |
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Nicholas G. Smedira, MD |
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Delos M. Cosgrove III, MD |
| Hôpital Trousseau, Tours, France |
Michel A. Marchand, MD
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Michel R. Aupart, MD |
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Agnes L. Sirinelli, MD |
| Thorax-, Herz- und Gefaess Chirurgisches Klinik, Kaiserslautern, Germany |
Walter Seybold-Epting, MD |
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Dorothee Sutor, MD |
| CHU de Liege, Liege, Belgium |
Raymond Limet, MD |
| University Hospital Gasthuisberg, Leuven, Belgium |
Willem J. Daenen, MD |
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Paul Herijgers, MD |
| Institut de Cardiologie, Montreal, Quebec, Canada |
Michel Pellerin, MD |
| University Hospital Uppsala, Uppsala, Sweden |
Thomas Dubiel, MD |
| Walsgrave Hospital, Coventry, England |
Robert Norton, MD |
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Ira R. A. Goldsmith, MD |
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References
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Vandervoort P.M., Rivera J.M., Mele D., et al. Application of color Doppler flow mapping to calculate effective regurgitant orifice area: an in vitro study and initial clinical observations. Circulation 1993;88:1150-1156.[Abstract/Free Full Text]
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Zabalgoitia M., Garcia M. Pitfalls in the echo-Doppler diagnosis of prosthetic valve disorders. Echocardiography 1993;10:203-212.[Medline]
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Flachskampf F.A., Rodriguez L., Chen C., Guerrero J.L., Weyman A.E., Thomas J.D. Analysis of mitral inertance. A factor critical for early transmitral filling. J Am Soc Echocardiogr 1993;6:422-432.[Medline]
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Wranne B., Ask P., Loyd D. Analysis of different methods of assessing the stenotic mitral valve area with emphasis on the pressure gradient half-time concept. Am J Cardiol 1990;66:614-620.[Medline]
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Abstract
Introduction
