Small aortic annulus: the hydrodynamic performances of 5 commercially available tissue valves

In vivo comparison of the performance of heart valve prostheses is confounded by several factors, such as different nominal size, patients' characteristics and hemodynamics, surgical techniques, and study design. The aim of this study was to compare the in vitro hydrodynamic performances of 5 different tissue valves that would fit a 21-mm-diameter valve holder of the Sheffield pulse duplicator.

Three samples of 5 supra-annular production-quality tissue valves, including the sewing ring cuffs, were tested in the aortic chamber of the Sheffield pulse duplicator. The prostheses fitting a 21-mm valve holder, which is comparable with a 21-mm aortic annulus, were as follows: 20-mm Sorin Soprano, 21-mm Carpentier-Edwards Magna, 21-mm SJM-Biocor-Epic-Supra, 21-mm Medtronic Mosaic, and 23-mm Mitroflow. The tests were carried out at a fixed pulse rate (70 beats/min) and at increasing cardiac outputs of 2, 4, 5, and 7 L/min. Each valve was tested 10 times for each different cardiac output. This resulted in a total of 40 tests for each valve and 120 tests for each valve model. Forward flow pressure decrease, effective orifice area, stroke work loss, and total regurgitant, closing, and leakage volumes were recorded while the valve operated under each cardiac output.

Pericardial valves showed significantly lower transvalvular gradients than porcine valves, unlike the SJM-Biocor-Epic-Supra valve at 2 L/min of cardiac output. Although the Carpentier-Edwards Magna valve provided the best performance at 2 and 4 L/min, the Mitroflow valve exhibited the lowest mean and peak gradients at 5 to 7 L/min. Total regurgitant and leakage volumes were higher for the Carpentier-Edwards Magna valve and lower for the SJM-Biocor-Epic-Supra and Mitroflow valves. Between 2 and 4 L/min, the calculated effective orifice area and stroke work loss were better for the Carpentier-Edwards Magna valve, whereas between 5 and 7 L/min, they were significantly superior with the Mitroflow prosthesis. Among the porcine bioprostheses, the SJM-Biocor-Epic-Supra valve showed significantly better results when compared with the Medtronic Mosaic valve at each cardiac output.

Assuming that the valve holder is comparable with a defined aortic annulus of 21 mm in which a spread of supra-annular tissue valves could be fitted, this hydrodynamic evaluation model allows comparison of the efficiency of currently available bioprostheses with a definite tissue annulus diameter. Pericardial valves exhibited the best performances, and the Mitroflow valve showed the lowest gradients and stroke work loss at increasing cardiac output.