Hemodynamic evaluation of the Hancock-modified orifice bioprosthesis in the aortic position.

Porcine xenografts have had marginal hemodynamic function in the aortic position, particularly in the smaller sized valves. A new modified orifice heterograft prosthesis (MO) has been designed with the muscular leaflet of the porcine valve excised and replaced with the nonmuscular leaflet of a second valve, thus allowing 25 to 35% improvement in effective internal orifice area. In vitro studies on MO show clear hydraulic improvement over standard porcine prostheses and function comparable to that of low-profile metal prostheses. The MO has been implanted in 26 patients followed from 1 to 10 months with no prosthetic dysfunction or thromboemboli. There has been one perioperative and no late deaths. Intraoperative peak systolic gradients averaged 6.6 mm (0 to 18 mm) for 21 mm prostheses and 1.8 mm (0 to 10 mm) for 23 mm prostheses. These compare favorably with average gradients of 14.0 mm (5 to 27 mm) for standard 23 mm prostheses, 10.1 mm (0 to 30 mm) for 25 mm, and 4.0 mm (0 to 14 mm) for 27 mm prostheses. The MO valve combines the advantages of a bioprosthesis with the excellent hemodynamic performance necessary for the patient with a small aortic anulus.