Endothelial cell rounding associated with long-term implantations of left ventricular assist devices

Culture endothelial cells have been utilized experimentally to inhibit thrombosis on cardiovascular prostheses. Grown on the internal surfaces of selected synthetic materials and implanted into autologous calves, prelinings have also proven to be a useful means to examine the influence of the in vivo environment on the endothelium. Initial short-term (less than 7 days) studies with left ventricular assist devices (LVADs) have demonstrated severe cell loss in endothelial prelinings as a result of continuous substrate flexure. These observations now have been extended to two chronic LVAD implantations of 28 and 125 days. By 28 days substantial regeneration of the endothelial layer had occurred to overlay the thrombus deposited as a result of prelining denudation. The morphologic characteristics of the endothelial linings in these two specimens have been studied. The most striking feature of the LVAD linings was the rounded appearance of the endothelial cells. These observations have led to the speculation that endothelial cells exposed to continuous mechanical strain assume an altered appearance. In addition, preliminary results utilizing a specially-built in vitro apparatus have demonstrated that endothelial rounding accompanied by intercellular separations may result from periodic stretching of the substrate material supporting the cells.