Relation between size of prosthesis and valve gradient: comparison of two aortic bioprosthesis.

Objectives: The outcome of patients undergoing aortic valve replacement (AVR) may be affected by the influence of prosthesis-patient mismatch on left ventricular mass regression. However, due to the discrepancies in labeled valve size, size of sizer and actual valve dimension, it is difficult to compare different valve types. In order to perform an objective comparison, this study was designed to compare the hemodynamics of the Edwards Lifescience pericardial (ELP) and the Medtronic Mosaic porcine (MM) bioprosthesis between patients receiving the same valve size and between patients with the same aortic annulus diameter.

Methods: This prospective, randomized study was performed on 81 hospital survivors out of 86 patients undergoing AVR with either the ELP (n=39) or the MM (n=42) bioprosthesis. Intra-operative randomization was performed after the surgeon had excised the aortic valve, measured the size of the aortic annulus with three different sizers (ELP, MM and a set of metric sizers), and decided which size he would implant for either of the valve types. All valves were implanted in supra-annular position with the same implantation technique. Echocardiographic follow-up was performed early postoperatively and 6 months thereafter.

Results: In 12 (31%) of the patients receiving the ELP-valve, as compared to 3 (7.1%) of the patients receiving the MM-valve, the labeled valve size was smaller than the aortic annulus diameter (P<0.05). Early postoperatively, mean (17.4+/-3.1 vs 20.3+/-3.6 mmHg) and peak gradients (30.1+/-4.8 vs 37.6+/-9.6 mmHg) for the 21 mm ELP-valve were lower than for the 21 mm MM-valve (P<0.05). All other hemodynamic parameters did not show significant differences at any time point. When the same aortic annulus diameter was taken as a reference, there were no significant hemodynamic differences between either valve type at any time point, regardless of the valve size implanted.

Conclusions: This study demonstrates that the hemodynamic performance of the ELP and the MM bioprosthesis are comparable when the same aortic annulus diameter is taken as a reference. The significant variabilities between different valve types with regard to labeled valve size, valve-sizer size and actual valve size have to be taken into account, when hemodynamic comparisons are performed.