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Cardiovascular Institute, University of Padua, Via Giustiniani, 2, Padova 35100, Italy
(Email: tbottio{at}gmail.com).
We read with interest the article by Borger and colleagues [1]. We congratulate the authors for this well-designed study, but we would like to add some brief comments. The authors compared the early (first postoperative month) in-vivo hemodynamic performances of 57 patients who received aortic Carpentier-Edwards Magna valves (Edwards Lifesciences LLC, Irvine, CA) versus 57 patients with Medtronic Hancock-II prostheses (Medtronic Inc, Minneapolis, MN). The patients were matched 1:1 according to age, sex, body surface area, and labeled valve size. The authors conclude that these tissue valves have significantly different hemodynamics.
The supra-annular concept or design refers to placement of a specifically designed prosthesis on top of the aortic annulus. Medtronic's Mosaic (Medtronic Inc), Carpentier-Edwards's Magna (Edwards Lifesciences), Sorin's Soprano (Sorin Group, Saluggia, Italy), and St. Jude's Medical Biocor Epic Supra (St. Jude Medical Inc, St. Paul, MN) and Mitroflow (Sorin Group Inc, Mitroflow Division, Canada), all belong to this category of aortic prostheses, which are third-generation bioprostheses. Unfortunately, the Hancock-II (Medtronic Inc) does not, and it is a second-generation bioprostheses that is completely different in design and hemodynamics.
The effective orifice area (EOA) is a flow-related measurement that is subject to unsteady conditions at low flow rates, which may affect EOA measurements [2]. Furthermore, when different prostheses are compared, in vivo values should be taken at 1-year follow-up, because gradients may change during the first postoperative year [3]. In addition, in vivo studies are limited not only by echocardiographic technical pitfalls, but also by different clinical settings that may confound results [4]. Botzenhardt and colleagues' [5] concluded that the Carpentier-Edwards Magna valve (Edwards Lifesciences) is the gold standard for the current generation of supra-annular tissue valves. Unfortunately, in this non-randomized study [5], patients were not compared by individual stroke volumes, and they were assessed within 10-days after operation, contrary to previous echocardiographic guidelines [6]. On the other hand, Totaro and colleagues [7] referred to the Carpentier-Edwards Perimount Magna as a "stented valve with stentless performance." Such title in our view is misleading as printed by Kon [8] who criticized both the timing of the echocardiographic analysis and the lack of "size by size analysis" among patients. As a matter of fact, a more meaningful in vivo comparison should have further considered diastolic function and prosthesis regurgitation. Unfortunately, these articles [1, 5, 7] did not investigate the diastolic phase of the cardiac cycle by ignoring the prosthesis backflow, missing the point to a greater or lesser degree.
In considering the excessively and surprisingly high regurgitant volumes observed in-vitro with the Carpentier-Edwards-Magna (Edwards Lifesciences) and the minimal tolerability of this model to stent distortion [4], upsizing of the Carpentier-Edwards-Magna should be carefully considered, not only for anatomical reasons, such as the coronary-ostia location.
In conclusion, in vivo studies comparing different prostheses are difficult, and although randomized and well-conducted, they are misleading because several confounding factors are frequently present. This concept is even more true when tissue valves that are extremely different in design and structure are compared. For this reason, it is hard to believe that we can identify a prosthesis model that can be used as a reference by interpreting only one aspect of a complex scenario.
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  M. A. Borger Reply Ann. Thorac. Surg., August 1, 2008; 86(2): 691 - 692. [Full Text] [PDF]
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