Background and aim of the study: In-vitro studies on the ATS heart valve have indicated that valve opening is less in an expanding conduit than in a straight conduit.
Methods: Bileaflet valve behavior was studied using a new computational fluid-structure interaction model. A three-dimensional model of the ATS valve was studied in two geometries, simulating the valve in a geometry with sudden expansion downstream of the valve, and in a straight conduit. Mitral and aortic flow patterns were simulated.
Results: The ATS valve in the expanding geometry showed opening to a maximum angle of 77.5°; this was confirmed in previous clinical and in-vitro studies. The mean and maximum transvalvular Doppler pressure gradients were 1.1 and 4.3 mmHg, respectively. The maximum shear stress calculated on the leaflet was 25 Pa.

Maximum opening of the valve was achieved in the straight conduit; with mean and maximum pressure gradients of 2.1 and 4.6 mmHg, respectively. The maximum shear stress calculated on the leaflet was 35 Pa.
Conclusion: The results of this numerical study confirmed that valve hemodynamics and leaflet motion were dependent on the geometrical conditions of the valve: the presence of a diverging flow influenced the maximum opening angle of the valve leaflets. This model could be used to predict pressure gradients, effective orifice area, performance index and shear stress loading of mechanical heart valves, and in future will serve as a major research tool to characterize the hemodynamics of existing and new mechanical heart valves.
The Journal of Heart Valve Disease 2005;14:393-399