Calcification and Thrombus Formation on Polymer Surfaces of an Artificial Heart

Calcification and thrombus formation are still important problems in artificial heart research. The calcification and thrombus formation generated in artificial heart blood pumps, driven without anticoagulant for 312 days as the left side and 414 days as the right side, were analyzed in this study. A thrombus was observed at the circumference of the sac in the 312-day pump, but it was not associated with calcification. Several phenomena were observed on the polymer membrane valves (jellyfish valves) incorporated into the blood pump: plastic deformation of the valve membrane by creep fatigue; no calcification of stationary parts such as spokes and the center of the membrane; calcification of the particular portion which received repeated stretching stress; and no association of calcification with thrombus. The calcification of the valve area which received repeated stretching force might be explained as follows. Repeated stretching forces extend the polymer membrane, causing some loosening between polymer molecules and generating microgaps. Blood proteins and phospholipids invade these microgaps, which then attract Ca2+ ions followed by phosphate ions(PO4 2-) leading to the formation of calcium phosphate complexes.