SCANNING ELECTRON-MICROSCOPY STUDIES OF THE PREVENTION OF BIOPROSTHETIC HEART-VALVE CALCIFICATION WITH CONTROLLED RELEASE POLYMERIC MATRICES

Pathologic calcification is the principal failure mode of bioprosthetic heart valves fabricated from glutaraldehyde pretreated porcine aortic valves. Bovine pericardial bioprosthetic valves also fail frequently by calcification. This review covers the novel uses of the scanning electron microscope (SEM) for investigating the pathology and prevention of bioprosthetic heart valve calcification. The progression and growth of calcific lesions in the bioprosthetic heart valve tissues has been documented using SEM with elemental localization by energy dispersive X-ray analysis (EDX). Controlled release polymeric matrices consisting of either ethanehydroxydiphosphonate, FeCl3 or Al(NO3)3 coimplanted with bioprosthetic tissue prevent experimental bioprosthetic calcification. SEM has also been used to study the drug particle distribution in the controlled release matrices. Furthermore, matrix drug release in vitro and in vivo has also been characterized and quantified using SEM techniques.