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J Thorac Cardiovasc Surg 2007;133:846-847
© 2007 The American Association for Thoracic Surgery
Letter to the Editor |
Cardiac Surgery Division, Morriston Hospital, Swansea, United Kingdom
To the Editor:
We read with extreme interest the article, "Small Aortic Annulus: The Hydrodynamic Performances of 5 Commercially Available Tissue Valves," published in the May 2006 issue of the Journal.1
We would like to congratulate Gerosa and coauthors for the well-designed study, but we would also add some brief comments. The authors evaluated in vitro performances of 5 bioprosthesis designed for supra-annular implantation and showed improved performances of the Mitroflow valve compared with the CE Perimount Magna (for cardiac output 
5 L/min). Inasmuch as the nominal size is not uniform for different prosthesis, they compared the size of each type fitting a 21-mm mounting ring (mimicking a 21-mm aortic annulus). The concept of supra-annular design is, however, different for the different prosthesis used in the study. As we2 recently showed, the CE Perimount Magna, the new generation of CE Perimount characterized by a new sewing cuff, allows the implantation of a bigger size prosthesis than does the standard CE Perimount valve in almost 50% of patients. This is due to the improved interaction between the new sewing cuff and the aortic surgical annulus, which is not a flat plane. This improved annulus-prosthesis interaction could also explain the improved in vivo performance of the CE Perimount Magna when compared with the standard CE Perimount valve of the same size, even though the valve itself (housing and leaflets) is not changed.
The supra-annular concept of the Mitroflow valve is different inasmuch as the sewing ring is on a flat plane. The mounting ring used in the study from Gerosa and coauthors is also on a flat plane, and this may have influenced the results of the study. In vitro hemodynamic performances of the CE Perimount Magna valve reported in this study, in fact, do not reflect in vivo hemodynamic performances that we reported in our study and that were also confirmed by other authors.3 This is quite unusual because, as the authors also state in their article, the in vitro effective orifice areas usually tend to overestimate the in vivo effective orifice areas. Furthermore, hemodynamic performances reported by Gerosa and coauthors do not reflect the in vitro hemodynamic performances reported for the CE Perimount standard valve by Marquez, Hon, and Yoganathan,4 even though, as we already stressed, the valve itself is not changed.
In conclusion we agree with the authors that in vivo hemodynamic behavior of a valve might differ from our idealized assumption. However, we do believe that in the case of prostheses with a supra-annular design, such as the CE Perimount Magna, in vivo performances could be improved owing to the improved annulus-prosthesis interaction. In vitro tests, like those reported in this study, are extremely useful in evaluating opening mechanism as well as descriptive parameters for each prosthesis. However, a real comparison of hemodynamic performances of two valves with such a different design as the Mitroflow and CE Perimount Magna can be made only in a randomized study evaluating cumulative mean postoperative effective orifice areas for two groups.
References
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