Optimization of a trileaflet valve design

This study investigates the fundamental principles that should govern the basic design of an optimal trileaflet valve. The geometry of the leaflets is described in terms of radius of the base (Rb), radius of the commissures (Rc), height of the valve (H), height of the commissures (Hs), and angle of the open leaflet to vertical (beta). Using computer-aided design software and these design parameters, a computer model of the valve was constructed. Choosing the parameters empirically did not produce an optimal valve. The four criteria for optimal performance were defined as: (1) a certain minimum coaptation height, (2) no folds in the leaflet, (3) minimum valve height, and (4) minimum leaflet flexion. Mathematical relationships were established between the design parameters and the performance parameters. These relationships indicated that the parameters Rc, Hs, and beta could be used to minimize valve height; however, a reduction in valve height must be balanced against the accompanying increase in leaflet flexion. For an optimal valve, the design parameters were Rb = 10 mm, then Rc = 8 to 10 mm, H = 11.5 mm, Hs = 2.4 to 2.6 mm, and beta = 4 degrees to 11 degrees . The optimal valve of any radius can be designed by scaling Rc, H, and Hs with respect to Rb. These design parameters were similar to those of the natural aortic valve. Trileaflet bioprosthetic valves designed on these principles are expected to have enhanced efficiency and longevity.