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Success of transcatheter valve replacement (TVR) relies heavily on the expansive forces the device imposes on the surrounding tissue, and the quality of the tissue that the device attaches to. To determine the cause of device failure, it is important to distinguish device fractures/faults from the poor quality of the tissue. Non-destructive examination methods that integrate the device structural defects and the histopathological attributes of the tissue could provide useful information about device failures. In this study, we report a new technique to integrate in situ μCT imaging with histopathological evaluation to provide an improved assessment technique.
Transapical mitral TVR was performed in five swine with fluoroscopy and ultrasound image guidance. Valve function and optimal location of the prosthesis was confirmed with echocardiography. Animals were followed for 18, 35 and 41 days. At termination, the whole heart was extracted and the mitral valve was excised. To ensure proper characterization of pathological features, three valves with evidence of endocarditis were subject to μCT imaging and subsequent histopathological evaluation.
All three valves macroscopically exhibited tan-yellow and dark deposits on the mitral implant (mainly at the anterior and posterior cusps). Histologically, these findings were associated to vegetative endocarditis with thrombosis and dystrophic calcification. The μCT evaluation clearly demonstrated a lack of metallic frame fractures or structural deformations. The soft tissue displayed easily identifiable radio-opacities in affected cusps, which accurately correlated with the macroscopic observations. μCT analysis by calcium segmentation demonstrated a range of areas of calcium deposits (between 8 and 189 mm3) occupying from 0.5 to 10.2% of the cusp/thrombus volume ratio.
μCT provides an entire valve evaluation platform that allows for non-destructive, 3-dimensional assessment with accurate segmentation of specific histopathological features for volumetric analysis, which facilitates advanced grading schemes. μCT serves as an ideal complementary technique to standard histopathology for mitral TVR preclinical studies.
OTHER: Pre-Clinical/First In-Human Studies