In vitro investigation of thrombogenesis in rotary blood pumps

Thrombus formation at sealing and stagnation areas remains a major problem in the development of rotary blood pumps. Until now, the complex phenomena could only be studied in vivo. In this study, an in vitro mock circulation previously used for hemolysis studies was adapted for thrombosis evaluation. Blood was collected in the slaughterhouse with strict avoidance of air contact and was heparinized (1.5 U heparin/ml blood; activated coagulation time [ACT]: initially, 140-180 s; after collection, 400-600 s). During the test, the ACT decreased gradually. The tests were stopped after 90 to 180 min at an ACT of 1.5 times the initial value. Thrombus formation was observed at the same locations as observed in left-heart assist devices (sealing area, connecting bolts, and stagnant water areas at connectors). The thrombi were similar in shape, color, and histology to those found after 2 to 4 days in vivo. This test provides a valuable tool for evaluating thrombus formation in prototypes and screening tests of different rotary pump designs.