IMMUNOCHEMICAL IDENTIFICATION OF HUMAN ENDOTHELIAL-CELLS ON THE LINING OF A VENTRICULAR ASSIST DEVICE

We are studying the biologic (pseudointimal) lining that forms in the HeartMate(R) (Thermo Cardiosystems, Inc.; Woburn, Massachusetts, USA), a left ventricular assist device with a pusher-plate blood pump, hous ed in solid titanium with uniquely textured blood-contacting surfaces. Sintered titanium microspheres cover the rigid surface, and integrall y textured polyurethane lines the flexing diaphragm. The texture of th e blood-contacting surfaces is designed to encourage formation of a bi ologic pseudointimal lining, which greatly reduces the risk of thrombo embolic complications. We performed immunochemical analyses to charact erize precisely the pseudointimal lining. Samples were taken from 2 ex planted pumps; 1 had supported a patient for 132 days and the other 18 9 days. The samples were cultured to detect factor-VIII-related antige n (von Willebrand factor), acetyl low-density lipoprotein receptors, s mooth-muscle-cell actin, and surface adhesion molecules specific for m onocytes/macrophages. Macrophage cells were predominant in both pumps, but in the 2nd pump, cultures from the center of the diaphragm were p ositive for acetyl low-density lipoprotein receptor and von Willebrand factor indicating the presence of endothelial cells. We believe that blood-borne endothelial cells or endothelial cell precursors were depo sited on the blood-contacting surfaces, which is an important clinical finding with regard to lowering the risk of thromboembolic complicati ons and reducing the need for systemic anticoagulation in long-term le ft ventricular assist device patients.