Optical methods for the nondestructive evaluation of collagen morphology in bioprosthetic heart valves

The aim of the present study was to assess the suitability of nondestructive optical methods as a means of evaluating collagen morphology in bioprosthetic heart valve leaflets. The results of this study demonstrate that transmitted polarized light and incident polarized light optics facilitate the imaging of the inherent birefringence of valvular collagen fibers. Polarized light optics readily document the different patterns of collagen orientation and configuration in porcine aortic valvular (PAV) and bovine pericardial valvular (BPV) bioprostheses. Incident polarized light optics also provide information on leaflet surface morphology. Verification that the birefringence observed by polarized ligh optics represents leaflet collagen was provided by conventional histologic and transmission electron microscopic methods. Quantitative determinations of the spacing of collagen bundle waves gave similar values in intact and in sectioned BPV leaflets. Potential applications of polarized light optics in the assessment of bioprosthetic valve collagen are as follows: the selection of the desired orientation of collagen bundles within pericardium intended to be configured into bioprosthetic leaflets; evaluation of the effects of mechanical stresses and leaflet motion on collagen morphology in bioprosthetic valve leaflets; and initial screening of leaflet specimens and selection of the desired collagen orientation for embedding and sectioning of samples for conventional morphologic studies.