2. Faculty of Applied Science, University of British Columbia, Vancouver, BC, Canada.
3. Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
St. Jude Medical (SJM) bileaflet mechanical valves were approved by the Food and Drug Administration in 1977. The SJM valve design consists of two semicircular leaflets which pivot on hinges. Compared to other mechanical heart valve prostheses such as ball and cage and tilting disk prosthetic valves, it provides good central flow, the leaflets open completely, and the pressure drop across the valve is trivial. However, non-physiological hemodynamics around these valves may lead to red blood cells lysis and therombigenic complications. Also, the regurgitation-flow inSJM valves is almost twice that of the native valves in the aortic position. In this study, we suggest a new design for the stent (housing) of SJM valves in which 15% ovality is applied to the stent whereas its perimeter remains constant. In a pilot study, the hemodynamic performance of the proposed design is analyzed in the closing phaseand compared to that of conventional SJM models. Results show that while the elliptic SJM model offers a shorter closing phase (9.7% shorter), the regurgitation flow remains almost unchanged. In other words, even though the dynamic response of the valve is improved, the regurgitation flow is not decreased. Thus, a more efficient effective orifice area (EOA) is shown to be provided by the proposed model. The preliminary calculations presented in this study justify an improved hemodynamics of elliptic SJM valves compared to conventional models; the proposed design shows promise and merits further development.
Keywords: Finite strip method, vascular hemodynamics, bileaflet mechanical heart valves, st, jude medical valve, heart valve prostheses, numerical modeling