An In Vivo Experimental Evaluation of Bioprosthetic Valves Using the Ovis Aries Model in the Mitral Position
Zehnder, Brian K.
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Because of the need for anticoagulation in patients with mechanical . prosthetic valvular substitutes, investigations concerning the medical benefit of bioprosthetic valves have been underway since the 1960s. Although a quarter of a century has elapsed, the prototype bioprosthetic valve has not yet evolved, largely due to difficulties with degeneration and calcification. Therefore, an in vivo investigation was developed, using the juvenile Ovis Aries (domestic sheep), to examine these problems in the mitral. position. Using 126 sheep, the valves remained implanted for an average of 15.2 +/- 11.1 weeks. The mean body weight and age of those sheep who survived until the terminal elective study (TES) was 36.3 +/- 7.7 kg. and 34.7 +/- 3.3 weeks, respectively (TES average length = 20.3 +/- 1.4 weeks; Mortality until TES = 53.6%). In this study, five porcine aortic and three bovine pericardial valve models were compared in the mitral position via hemodynamic, pathological, and calcium assessment. Of the various valve types, those valves which had been treated with a T6 or PVII process calcified to a much smaller extent than their standard counterparts. Porcine aortic valves are hemodynamically more advantageous for implantation than bovine pericardial valves.