Abstract 10279: Three-Dimensional Deep-Tissue Imaging of the Right Ventricle Reveals the Complex Remodeling of the Microvascular Network in Right Heart Failure

Introduction: Right ventricular (RV) failure is the leading cause of death in patients with pulmonary arterial hypertension (PAH). Capillary rarefaction has been proposed as the hallmark of RV failure, yet our understanding of the capillary architecture is limited by 2D image analysis. Three-dimensional (3D) confocal deep tissue imaging offers the unparalleled opportunity to characterize the architectural microvascular changes in relationship to cardiomyocytes in pressure-overloaded RV failure. Methods and Results: 250 μm heart tissue slices from mice with RV failure, 7-weeks after Pulmonary Artery Banding (PAB) were harvested and the microvascular network was assessed for density, segment length, diameter, orientation, as well as microvasculature-cardiomyocyte contact area in regions with and without interstitial fibrosis using confocal 3D imaging. Human heart tissue from end-stage PAH patients was compared to controls with normal RV function. In PAB mice, 3D imaging of the RV free wall revealed tortuous, shorter, thicker and higher-branched microvascular segments as well as development of fibrosis compared to Sham animals (Fig A). When corrected for fibrosis, the microvascular density was preserved even in advanced stages of RV failure. Physical contact between the microvasculature and cardiomyocytes was preserved in areas without fibrosis, yet significantly impaired in areas with interstitial fibrosis (Fig B), accompanied by an overexpression of β-myosin heavy chain suggesting local ischemia (Fig C). 3D imaging of human RV tissue of end-stage PAH patients revealed architectural microvascular remodeling that varied depending on etiologies and length of disease yet showed preserved microvascular density. (Fig. D). Conclusions: 3D deep tissue imaging revealed compensatory changes of the microvascular network to maintain a stable cardiomyocyte coverage in pressure-overloaded RV failure, which was impaired in areas of interstitial fibrosis.