Bileaflet, tilting disc and porcine aortic valve substitutes: In vivo hydrodynamic characteristics

The St. Jude valve is a new bileaflet disc cardiac valve prosthesis designed to avoid some of the hemodynamic drawbacks of other prostheses. The in vivo flow characteristics of the St. Jude aortic valve (42 patients) were studied and compared with those of three other commonly used aortic prostheses. Björk-Shiley (12 patients), Hancock (27 patients) and Carpentier-Edwards (15 patients). The studies, performed 24 to 48 hours after surgery, included measurements at rest and during augmentation of valve flow by infusion of isoproterenol. The mean performance index for valves of all sizes is higher for the St. Jude than for either porcine valve, both at rest and during isoproterenol infusion (p < 0.05). Utilizing data both at rest and with isoproterenol, the relation of valve flow and mean systolic gradient for each size of St. Jude valve (19 to 25 mm) indicates the occurrence of small increases in gradient (5.3 to 8.2 mm Hg) as valve flow increases, ranging from 161 to 436 ml/systolic .min. A direct comparison of valve flow and gradient data for all size 25 and 23 mm prostheses at rest indicates a tendency for a lower mean systolic gradient in both mechanical valves than in either porcine valve (p = 0.07). With isoproterenol augmentation of valve flow in 25 mm valves, the gradient is less (p < 0.05), and the effective orifice area and performance index are larger (p < 0.05) for the St. Jude than for either porcine valve. The performance of the 25 mm Björk-Shiley valve follows a trend similar to that of the St. Jude valve, but does not reach statistical significance because fewer valves of this type were available for testing. In size 23 valves with isoproterenol, only the St. Jude valve has a lower gradient, larger effective orifice area and performance index than the Carpentier-Edwards valve, there being too few Björk-Shiley and Hancock valves in this category to provide a comprehensive analysis. Thus, hydrodynamic function of the St. Jude prosthesis is similar to that of the Björk-Shiley valve for flow rates at rest. At a higher valve flow (with isoproterenol), in size 25 mm valves, function of both mechanical prostheses is superior to that of both porcine valves; in size 23 mm, our data suggest that function of the St. Jude valve may also be superior to that of the Björk-Shiley valve. However, this comparison is limited by the small number of Björk-Shiley prostheses tested with isoproterenol.