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Ann Thorac Surg 2007;83:2054-2058
© 2007 The Society of Thoracic Surgeons

Original Articles: Cardiovascular

Carpentier-Edwards Perimount Magna Valve Versus Medtronic Hancock II: A Matched Hemodynamic Comparison

Michael A. Borger, MD, PhD*, A. Franka Nette, MD, Manjula Maganti, MS, Christopher M. Feindel, MD

Division of Cardiovascular Surgery, Toronto General Hospital, and Department of Surgery, University of Toronto, Toronto, Ontario, Canada

Accepted for publication February 21, 2007.

* Address correspondence to Dr Borger, Leipzig Heart Center, Struempellstrasse 39, Leipzig, 04289, Germany (Email: michael.borger{at}med.uni-leipzig.de).


   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
Background: The Perimount Magna valve (Edwards Lifesciences, Irvine, CA) was designed to minimize the amount of obstruction to blood flow across the valve. We compared hemodynamic performance of the Perimount Magna valve with the Hancock II valve (Medtronic, Minneapolis, MN), a second-generation porcine bioprosthesis with proven long-term results.

Methods: The 57 patients who received a Magna valve at our institution from 2003 to 2005 were matched 1:1 with 57 patients who received a Hancock II valve on variables known to affect hemodynamic measurements: size of implanted valve, age, sex, and body surface area. Early postoperative transthoracic echocardiography was performed in 100% of patients.

Results: In addition to the matched variables, patients in both groups were similar for all measured preoperative characteristics and perioperative clinical outcomes. One week postoperatively, Magna patients had significantly lower peak (22.1 ± 7.4 mm Hg versus 32.3 ± 15.1 mm Hg) and mean transvalvular gradients (10.4 ± 4.0 mm Hg versus 18.5 ± 15.5 mm Hg, both p < 0.001). The Magna group also had a trend towards a larger effective orifice area (1.40 ± 0.24 cm2 versus 1.29 ± 0.34 cm2, p = 0.07), despite a similar left ventricular outflow tract diameter (2.0 ± 0.2 cm versus 2.0 ± 0.1 cm, p = 0.7). Patient–prosthesis mismatch, as defined by measured effective orifice area of less than 0.65 cm2/m2, was significantly less common in the Magna group (30% versus 52%, p = 0.02).

Conclusions: The Magna valve has more favorable early postoperative hemodynamics than the Hancock II valve. Further studies should be performed comparing the Magna valve to newer-generation, low-profile porcine valves.


   Introduction
Top
 Abstract
 Introduction
Material and Methods
 Results
 Comment
 References
 
The Carpentier-Edwards Perimount Magna valve (Edwards Lifesciences, Irvine, CA) was introduced in 2003 as a modification of the standard Perimount valve. It is a stented bioprosthesis constructed of bovine pericardium and is intended for supraannular positioning. The Magna valve has a smaller sewing ring, which may result in an increased effective orifice area (EOA) and improved hemodynamic performance [1]. In addition, the smaller sewing ring may result in the ability to upsize the selected prosthesis in some patients.

The Hancock II valve (Medtronic Inc, Minneapolis, MN) is a fabricated trileaflet porcine valve that was first introduced to clinical use in 1982. It is a second-generation porcine bioprosthesis with several improvements over its predecessor, the Hancock Standard valve, intended to improve hemodynamic performance and durability. The Perimount standard and Hancock II valves both show excellent long-term durability and freedom from structural valve deterioration, particularly in elderly patients [2, 3].

Relatively little has been published on the Magna valve because of its recent clinical introduction. The goal of the current study was to compare early postoperative hemodynamic performance of the recently launched Perimount Magna pericardial valve with the Hancock II porcine valve.


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 References
 
Ethics approval was granted by the University of Toronto Research Ethics Board, and individual patient consent was waived. An examination of our computerized database found 57 patients who underwent aortic valve replacement (AVR), plus or minus concomitant procedures, with the Perimount Magna valve in 2004 to 2005. We then matched the 57 Magna AVR patients 1:1 with 57 Hancock II AVR patients with respect to variables that are known to affect valvular hemodynamic performance: age, sex, body surface area, and labeled size of the implanted valve [4]. The matched Hancock II patients were operated on between 2000 and 2005 and represented 15% of the total Hancock II AVR patients (n = 384) from this time interval.

Operative Technique
Whether the patient received a Magna or Hancock II valve was determined by surgeon or patient preference, or both. Most of the Magna valves were implanted by a single surgeon (MAB). The AVR procedure was performed with previously described techniques [5, 6]. A transverse aortotomy was performed 1 to 2 cm above the right coronary artery. Myocardial protection was performed with cold antegrade or retrograde blood cardioplegia, or both. The aortic annulus was thoroughly débrided of calcium.

Valve sizing was performed with standard manufacturers’ sizers, with selection of the size that would comfortably fit within the aortic annulus. In patients with a small annulus that would result in marked patient–prosthesis mismatch, we performed annular enlargement with autologous pericardium or a piece of Dacron graft (DuPont, Wilmington, DE) according to previously described techniques [7]. A noneverting suture technique was used in all patients with interrupted horizontal mattress 2-0 braided sutures placed around the aortic annulus, with the pledgets on the ventricular aspect. Care was taken to ensure that the distance within pledgeted sutures was the same on the aortic annulus as on the sewing ring of the valve to prevent plication of the aortic annulus.

Concomitant coronary bypass grafting and mitral valve procedures were performed in the standard fashion before AVR. Patients requiring concomitant replacement of the ascending aorta received a supracoronary Dacron tube graft. Septal myectomy was performed in patients with asymmetric hypertrophy of the septum and an increased gradient across the left ventricular outflow tract [8].

Echocardiography
Transthoracic echocardiography was performed 1 week postoperatively to evaluate the early postoperative hemodynamic performances of the two valves. Standard techniques were used to obtain echocardiographic measurements, in accordance with the American Society of Echocardiography guidelines. Pulsed wave Doppler was used to measure mean and maximum systolic blood flow velocities (Vmean and Vmax) in the left ventricular outflow tract (LVOT), and continuous wave Doppler was used to measure systolic blood flow velocities across the aortic valve (AV).

Peak and mean transvalvular gradients were obtained using the modified Bernoulli equation:


Formula



Formula

The EOA was calculated with the continuity equation:


Formula

where CSALVOT = LVOT cross sectional area ({pi}r2/4) in square centimeters, TVILVOT = LVOT time velocity integral of forward blood flow in centimeters, and TVIAV = transvalvular time velocity integral of blood flow in centimeters. Left ventricular mass was calculated according to previously published guidelines [9].

Statistical Analysis
Categoric variables are expressed as percentages and continuous variables are expressed as mean ± standard deviation. All statistical analyses were performed with SAS 8.2 software (SAS Institute, Inc, Cary, NC). Comparison of categoric variables was performed with {chi}2 or Fisher exact tests, and continuous variables were analyzed with unpaired t tests or Wilcoxon tests. Statistical significance was defined as p < 0.05.


   Results
Top
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 References
 
A total of 57 Magna patients were matched 1:1 with 57 Hancock II patients according to age, sex, body surface area, and labeled valve size. The labeled size of the implanted valve was similar for the two groups (mean valve size, 26 ± 3 versus 27 ± 3 for Magna versus Hancock II, respectively, p = 0.5). Preoperative patient characteristics are summarized in Table 1. The two groups were similar for all the listed characteristics, with the exception of native aortic valve pathology. The prevalence of bicuspid aortic valve disease was higher in the Magna group; however, aortic stenosis was the main indication for surgery in both groups.


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  		Table 1 Preoperative Variables for Patients Undergoing Aortic Valve Replacement With Edwards Perimount Magna Versus Medtronic Hancock II Bioprostheses
 
Intraoperative variables are summarized in Table 2. The Hancock II group had a higher incidence of concomitant mitral valve surgery. Other intraoperative variables were similar for the two groups.


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  		Table 2 Intraoperative Variables for Patients Undergoing Aortic Valve Replacement With Magna Versus Hancock II Valves
 
Early postoperative outcomes are presented in Table 3. Clinical outcomes were good for patients in both groups, with no significant differences. In-hospital mortality was 3% for the entire cohort.


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  		Table 3 Early Postoperative Outcomes for the Two Groups of Patients
 
Transthoracic echocardiograms were performed before discharge in all surviving patients. The early postoperative hemodynamic measurements are listed in Table 4. The Magna prosthesis showed significantly lower peak and mean transvalvular gradients. There was also a trend towards a larger EOA for Magna patients, but the difference failed to reach statistical significance (p = 0.07). Valve EOA, stratified by labeled size, is displayed in Figure 1. Size 23 Magna valves had a significantly larger EOA than size 23 Hancock II valves.


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  		Table 4 Valvular Hemodynamic Performance and Left Ventricular Measurements One Week Postoperatively
 

Figure 1
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  		Fig 1. In vivo effective orifice areas for Perimount Magna (open bars) and Hancock II (filled bars) aortic tissue valves, as measured 1 week postoperatively. The number of patients in each group and standard error bars are shown above each column. The effective orifice area was significantly larger for size 23 Magna valves (*p < 0.05).

 
The EOA measured in vivo was also used to calculate the prevalence of patient–prosthesis mismatch, as defined by a measured EOA of less than 0.65 cm2/m2. Patient–prosthesis mismatch was significantly more common in Hancock II patients (52% versus 30%, p = 0.02).


   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
We compared early postoperative hemodynamic performance of the recently approved Magna pericardial prosthesis with the Hancock II stented porcine valve. We found significantly lower transvalvular gradients and a trend towards larger EOAs in Magna patients. Magna patients also had a significantly lower prevalence of patient–prosthesis mismatch. Although our study was not randomized, we matched patients according to age, sex, body surface area, and labeled valve size, which are variables known to affect valve hemodynamic performance [4]. Other preoperative and intraoperative variables for the two groups were comparable, with the exception of more concomitant mitral valve surgery in the Hancock II group. Hancock II patients also had a nonsignificantly increased left ventricular mass early postoperatively. However, decreased left ventricular size and mass are risk factors for increased postoperative transvalvular gradients; therefore, the difference between the two groups should result in an even more favorable comparison for the Magna valve [10, 11]. We are thus confident that our observations are valid.

The development of a stented aortic tissue valve with improved hemodynamics is an important goal in cardiac surgery. Stented tissue valves have bulky sewing rings and stents and are obstructive to some degree in all patients. Stented valves increase the risk of patient–prosthesis mismatch, particularly in patients with a small aortic root [12]. Patient–prosthesis mismatch has been demonstrated to decrease short-term and long-term survival after AVR [13, 14]. Stentless tissue valves have better hemodynamic performance and lower risk of patient–prosthesis mismatch than stented valves [15, 16] but are more complicated to insert. Thus, an important objective in the development and refinement of stented tissue valves is to improve their hemodynamic performance while maintaining their ease of insertion.

The Perimount Magna valve has a smaller, more scalloped sewing ring compared with the standard Perimount valve. The smaller sewing ring results in a reduction in the external diameter of the valve of 2 to 3 mm—roughly corresponding to a decrease of one full, labeled valve size—with no reduction in the internal diameter. The sewing ring is also more flexible than that of the standard Perimount, which allows the valve to sit in a more supraannular position. Supraannular positioning of stented bioprostheses results in decreased obstruction to blood flow and improved hemodynamic performance [17].

The Magna valve was recently released for clinical use and relatively few studies have been published about its use. Botzenhardt and colleagues [1] compared hemodynamic performances of the Magna valve with other stented bioprostheses in patients with a small aortic annulus (≤23 mm). The Magna valve was superior to other supraannular protheses—the Perimount standard, Mosaic (Medtronic), and Soprano (Sorin Biomedica Cardio, Via Crescentino, Italy) valves—in patients with an aortic annulus diameter of between 21 and 23 mm. Totaro and colleagues [18] randomized 63 elderly patients to receive a Prima Plus (Edwards Lifesciences), Magna, or Perimount standard valve [18]. Although the Prima Plus is a stentless valve, these investigators demonstrated lower transvalvular gradients and larger EOAs for the Magna valve compared with the other two prostheses. Preliminary results have therefore been encouraging for this newly approved valve.

The smaller sewing ring and external diameter of the Magna valve may enable upsizing by one labeled size over a standard Perimount valve. We caution against overly aggressive valve upsizing, however. The sewing ring of the Magna valve is more flexible and is pulled down towards the aortic annulus after implantation, with resultant marked supraannular positioning of the valve frame. As observed with other supraannular valves, supraannular positioning may result in obstruction of coronary artery orifices [19]. Aggressive upsizing should therefore be avoided in patients with coronary ostia that are closely situated to the aortic annulus or in patients with bicuspid aortic pathology, where abnormalities of coronary anatomy are a relatively frequent occurrence [20].

An important issue to consider when comparing hemodynamic performance of valves is their external diameters. It is well known that external and internal valve diameters vary substantially between manufacturers and are not linearly related to labeled valve size [21]. We believe, however, that a direct comparison of the Hancock II and Magna valves is valid. As can be seen in Table 5, the external diameter of the Hancock II valve is 1 to 5 mm larger than the external diameter of the Magna valve, depending on which labeled valve size is examined. It should therefore be possible to insert a larger labeled size Magna valve than a Hancock II valve in some patients. In addition, the mean labeled valve size was slightly (but not significantly) larger for the Hancock II patients, as can be seen in Figure 1. These conditions should have resulted in a hemodynamic advantage for the Hancock II valve, and yet we found the contrary to be true. We are therefore confident that our observations are meaningful.


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  		Table 5 Geometric Dimensions of Perimount Magna Versus Hancock II Valve a
 
We chose to compare the Hancock II with the Magna valve because we have a large clinical experience with the Hancock II and a large number of patients were thus available for matching. In contrast with the recently released Magna, the clinical experience with the Hancock II exceeds 20 years [2]. It should be mentioned, however, that Medtronic has recently released a new version of the Hancock II valve. The Hancock II Ultra valve has a smaller sewing ring, which may result in improved hemodynamic performance. Future studies that compare the Hancock II Ultra with the Perimount Magna valve should be performed.

One limitation of the current study is its relatively small sample size due to the recent regulatory approval of the Magna valve. All consecutive patients receiving a Magna valve during the study period were included. Despite the small sample size, we were able to demonstrate statistically significant differences in peak and mean transvalvular gradients and in the prevalence of patient–prosthesis mismatch, as well as a trend toward larger EOAs in Magna patients. Including more patients might have resulted in even more statistically (but not clinically) significant findings.

Another limitation of our study is its retrospective nature. The study was not a randomized trial, and some of the observed differences may thus be attributable to bias or unmeasured factors. It is important to note, however, that we carefully matched patients on those variables—age, sex, body surface area, and labeled valve size—that are known affect valvular hemodynamic performance. We were unable to match patients according to the size of the aortic annulus as measured intraoperatively because this information was not available. As already noted, however, the Hancock II valve has a larger external diameter than the Magna valve; therefore, it may have been possible to insert larger Magna valves than Hancock II valves in patients with the same size aortic annulus. If intraoperative annular measurements were accounted for in our analysis, we therefore believe that our results would be even more in favor of the Magna prosthesis.

In conclusion, we performed a matched, retrospective comparison of the Magna pericardial prosthesis with the Hancock II porcine valve. We found significantly lower transvalvular gradients, less patient prosthesis mismatch, and a trend toward larger EOAs for the Magna valve after matching for variables that affect valvular hemodynamic performance. Future studies should focus on a comparison between the Magna valve and the more recently approved low-profile porcine valves (ie, Hancock II Ultra and Mosaic Ultra prostheses) to determine if the hemodynamic advantage persists.


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 

  1. Botzenhardt F, Eichinger WB, Bleiziffer S, et al. Hemodynamic comparison of bioprotheses for complete supra-annular position in patients with small aortic annulus JACC 2005;45:2054-2060.[Abstract/Free Full Text]
  2. Borger MA, Ivanov J, Armstrong S, Hrybisnky DC, Feindel CM, David TE. Twenty-year results of the Hancock II-bioprothesis J Heart Valve Dis 2006;15:1-8.[Medline]
  3. Puvimanasinghe JP, Takkenberg JJ, Eijkemans MJ, et al. Comparison of Carpentier-Edwards pericardial and supraannular bioprostheses in aortic valve replacement Eur J Cardiothorac Surg 2006;29:374-379.[Abstract/Free Full Text]
  4. Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention JACC 2000;36:1131-1141.[Abstract/Free Full Text]
  5. Borger MA, Preston M, Ivanov J, et al. Should the ascending aorta be replaced more frequently in patients with bicuspid aortic valve disease? J Thorac Cardiovasc Surg 2004;128:677-683.[Abstract/Free Full Text]
  6. David TE. Surgery of the aortic valve Curr Probl Surg 1999;36:426-501.[Medline]
  7. Sommers KE, David TE. Aortic valve replacement with patch enlargement of the aortic annulus Ann Thorac Surg 1997;63:1608-1612.[Abstract/Free Full Text]
  8. Williams WG, Wigle ED, Rakowski H, Smallhorn J, LeBlanc J, Trusler GA. Results of surgery for hypertrophic obstructive cardiomyopathy Circulation 1987;76(5 Pt 2):V104-V108.[Medline]
  9. Guidelines from the Canadian Cardiovascular Society and the Canadian Hypertension Society on the echocardiographic determination of left ventricular massTask Force of the Echocardiographic Section. Can J Cardiol 1995;11:391-395.[Medline]
  10. Bach DS, Lemire MS, Eberhart D, Armstrong WF, Deeb GM. Impact of high transvalvular velocities early after implantation of Freestyle stentless aortic bioprosthesis J Heart Valve Dis 2000;9:536-543.[Medline]
  11. Bartunek J, Sys SU, Rodrigues AC, van Schuerbeeck E, Mortier L, de Bruyne B. Abnormal systolic intraventricular flow velocities after valve replacement for aortic stenosisMechanisms, predictive factors, and prognostic significance. Circulation 1996;93:712-719.[Abstract/Free Full Text]
  12. Gonzalez-Juanatey JR, Garcia-Acuna JM, Vega Fernandez M, et al. Influence of the size of aortic valve prostheses on hemodynamics and change in left ventricular mass: implications for the surgical management of aortic stenosis J Thorac Cardiovasc Surg 1996;112:273-280.[Abstract/Free Full Text]
  13. Walther T, Rastan A, Falk V, et al. Patient prosthesis mismatch affects short- and long-term outcomes after aortic valve replacement Eur J Cardiothorac Surg 2006;30:15-19.[Abstract/Free Full Text]
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  15. Borger MA, Carson SM, Ivanov J, et al. Stentless aortic valves are hemodynamically superior to stented valves during medium-term follow up: a large retrospective study Ann Thorac Surg 2005;80:2180-2185.[Abstract/Free Full Text]
  16. Yun KL, Jamieson WR, Khonsari S, Burr LH, Munro AI, Sintek CF. Prosthesis-patient mismatch: hemodynamic comparison of stented and stentless aortic valves Sem Thorac Cardiovasc Surg 1999;11:98-102.[Medline]
  17. Badano LP, Pavoni D, Musumeci S, et al. Stented bioprosthetic valve hemodynamics: is the supra-annular implant better than the intra-annular? J Heart Valve Dis 2006;15:238-246.[Medline]
  18. Totaro P, Degno N, Zaidi A, Youhana A, Argano V. Carpentier-Edwards Perimount Magna bioprosthesis: a stented valve with stentless performance J Thorac Cardiovasc Surg 2005;130:1668-1674.[Abstract/Free Full Text]
  19. Matsuzaki K, Unno H, Konishi T, Shigeta O. Left coronary ostial obstruction after aortic valve replacement with a supra-annular aortic valve Jpn J Thorac Cardiovasc Surg 2006;54:199-202.[Medline]
  20. Borger MA, David TE. Management of the valve and ascending aorta in adults with bicuspid aortic valve disease Sem Thorac Cardiovasc Surg 2005;17:143-147.[Medline]
  21. Christakis GT, Buth KJ, Goldman BS, et al. Inaccurate and misleading valve sizing: a proposed standard for valve size nomenclature Ann Thorac Surg 1998;66:1198-1203.[Abstract/Free Full Text]

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This Article
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Christopher M. Feindel
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