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Description
Left Ventricular Assist Devices (LVADs) are mechanical pumps aimed to improve substandard heart function due to congestive heart failure (CHF). By design, the device alters cardiac biomechanics and hemodynamics, resulting in intended and unintended remodeling. Studies in the past decade have noted LVAD-acquired dysfunctions affecting the aortic valve (AoV), though the exact mechanisms are unknown. We hypothesize that LVADs alter mechanical stresses and strains experienced in the AoV, resulting in soft tissue remodeling. Previous studies have linked LVAD-acquired aortic commissural fusion with aortic insufficiency (AI) and aortic stenosis (AS). To investigate, the AoV and proximal ascending aorta were obtained from fifteen explanted hearts. Detailed geometrical measurements and histological analyses were made and correlated with partial patient medical records. The results revealed that eleven of fifteen LVAD patients possessed some degree of commissural fusion. In addition to some measurements of AoV anatomy being higher than those previously reported for normal human valves, there were a number of observed abnormalities in their structure, including: calcification, leaflet fenestrations, verrucae and folding; their presence suggests exposure to excess mechanical stress and tissue damage. The valves also showed evidence of annular dilatation and leaflet lengthening. Histological examination of the available valves revealed areas of superficial deposition of collagen proximal to the aortic walls, as well as the unilateral deposition of collagen and elastin band dissolution at the AoV ventricular surface. The extensiveness of fusion seemed to be loosely related to the duration of LVAD support. Previous studies of LVAD-induced commissural fusion provided general, gross observations of fused leaflet tissue. Previous research conducted by our lab provided an extensive characterization and analysis of abnormal tissue geometry, morphology, and histology in patients implanted with older generation, pulsatile-flow LVADs (PF-LVAD). Recently, the greater success and widespread use of smaller, continuous-flow LVADs (CFLVAD) inspired the investigation of its affect on cardiac biomechanics, and found that the condition of induced commissural fusion not only persists, but has worsened in scope. Our results corroborate conclusions from our previous studies that immediate changes occur in the AoV post-LVAD implantation, which may negatively affect patients' long term health. Though a direct relationship between acquired commissural fusion and AI could not be analyzed due to scarce medical record information, our results have refined avenues for future analysis towards leaflet damage, annular dilatation, and leaflet lengthening. This research provides a description of AoV fusion that contributes to the continued understanding of AoV disease and its relationship to abnormal biomechanics induced by LVAD support.