In-vitro and clinical evaluation of cardiac valve substitutes

One of the major causes of postoperative morbidity and mortality after valve replacement surgery is the prosthetic valve substitute itself. In this discussion, therefore, we make a fundamental evaluation of hydrodynamic valve function and present our clinical results following valve replacement with the Björk-Shiley valve prosthesis, the Hancock porcine xenograft and the Ionescu-Shiley bovine pericardial xenograft. In an experimental study using a mechanical simulator system, the pericardial xenograft displayed superior hydrodynamic characteristics compared to other two valve substitutes. Postoperative hemodynamic evaluation further indicated that the pericardial xenograft performed significantly better than the porcine xenograft regarding transvalvular pressure gradient, effective valve area and cusp opening. In addition, data from 387 patients with aortic, mitral or both types of valve replacement who had received one of the three kinds of valve substitute were analyzed. Systemic thromboembolic complications occurred in one patient with an aortic Björk-Shiley valve (0.6% per patient-year), six with mitral Hancock xenografts (2.8% per patient-year) and one with an aortic and mitral Hancock xenograft (2.2% per patient-year). The incidence of prosthetic valve endocarditis was 0.84% per patient-year for the Hancock xenograft and 1.84% per patient-year for the Ionescu-Shiley xenograft. It was concluded that the hemodynamic and antithrombogenic advantages of the pericardial xenograft proven by our mid-term follow-up study make it the valve substitute of choice. However, careful attention is required regarding prosthetic valve endocarditis tissue heart valves, which are more susceptible to infection than mechanical ones, and the long-term durability of the pericardial xenograft remains to be confirmed.