New blood‐compatible polymers for artificial heart applications

Flexible and rigid epoxy and urethane polymers containing heparin chemically and uniformly incorporated throughout and/or ionically complexed to quaternized amine grops were prepared and shown to have excellent thromboresistance in vitro and in vivo. These heparin‐modified polymers were implanted into the vena cava of dogs and successfully passed multiple acute (2 hr) and chronic (2 week) exposure periods. It was also demonstrated that the chemically coupled heparinized epoxies had no measurable adverse effects on blood cells, platelets, or plasma proteins, and that the heparin was not extractable. Significantly, epoxies containing polyoxypropylene/polyoxyethylene glycol (an additive which had no thrombus‐inhibiting properties of its own) also exhibited excellent thromboresistance when characterized in vivo in dogs. The applicability of these various materials for the fabrication of circulatory assist device components was demonstrated. The effect of polymer polarity, surface charge, and conductivity were investigated with indeterminate results and unmodified commercial polymers uniformly exhibited poor clotting characteristics. In vitro clot‐inhibiting characteristics were shown to be a sufficient, but not necessary, condition for indicating in vivo thromboresistant activity in polymer systems.