Biomembrane mimicry provides improved thromboresistance for total artificial hearts

Thromboembolic events remain a significant issue in mechanical circulatory support. The aim of this study was to evaluate the potential benefit of sur face modification in total artificial hearts (TAHs) using polymeric phospho lipids (biomembrane mimicry). For this purpose, pneumatic TAHs (vacuum form ed pellethane housing, hard double flap hinged inflow valves, soft trileafl et polyurethane outflow valves) had their blood-exposed surfaces either mod ified with polymeric phospholipids or unmodified before evaluation in bovin e experiments. Orthotopic implantation of the TAHs was performed with cardi opulmonary bypass (CPB) using tip-to-tip heparin surface coated perfusion e quipment and very low systemic heparinization (50 IU/kg bodyweight). After weaning from CPB and stabilizing hemodynamics, circulating heparin was neut ralized with protamine (1:1). All animals were totally supported for 24 hou rs before elective sacrifice. No heparin was added at any time during suppo rt. Mean activated coagulation time (ACT) was 167 +/- 24 s at baseline befo re heparinization for CPB, 330 +/- 45 s at the end of CPB, 181 +/- 25 s aft er 1 hour of support, 180 +/- 31 s after 6 hours, and 185 +/- 28 s after 18 hours. After explantation, the TAHs perfused without anticoagulation were carefully analyzed. Atrial cuff coverage with red clot was 30 +/- 21% for a rtificial surfaces modified by biomembrane mimicry versus 100 +/- 0% for st andard control surfaces (p < 0.01). The number of macroscopic deposits foun d on the inflow valves was 1.33 +/- 0.47 far surfaces modified by biomembra ne mimicry versus 3.83 +/- 1.86 for standard control surfaces (p < 0.05). L ikewise, on the outflow valves the number of macroscopic deposits was 0.00 +/- 0.00 for surfaces modified by biomembrane mimicry versus 1.00 +/- 0.81 for standard control surfaces (p < 0.05). We conclude that presence and dis tribution of red clots and other macroscopic deposits are significantly dif ferent for artificial surfaces with biomembrane mimicry versus standard con trol surfaces. Application of the biomembrane mimicry concept has the poten tial to provide improved TAHs.