Hemodynamic properties of St. Jude medical and Björk-Shiley valvular prostheses in mitral position in the pulse duplicator.

A general lack of standardization of the pre-clinical testing of artificial valves leads to an actual comparison of different prosthetic models at the time of a first clinical trial, frequently with contradictory results. Therefore, a pulse duplicator was developed in order to compare different valves of comparable size under identical standardized conditions in aortic and mitral positions. Comparison of Björk-Shiley and St. Jude medical prostheses in the duplicator revealed a linear relationship between pump setting and stroke volume delivered (r less than or equal to 0.9) for both valves. Pressure loss across the mitral valves showed a linear relationship to stroke volume (less than or equal to 0.9) and frequency (less than or equal to 0.9). The gradient, expressed per milliliter stroke volume, for identical frequencies appeared as the simplest and most suitable parameter for comparison of the hydraulic function of different valves. Using this parameter, the valves showed individual differences over a wide physiological range of testing. The differences, however, are of a magnitude that can hardly be detected under clinical testing conditions.