IN-VITRO RECIRCULATION OF HUMAN BLOOD THROUGH THE TCI HEARTMATE®

Abstract

Purpose: Our understanding of blood-surface interactions in the TCI HeartMate® assist device is largely derived from late observations made at the time of device removal. In particular, formation of a non-thrombogenic neo-intima within the device has been well described. The purpose of our study was to assess the contribution of surface and flow characteristics to early blood-surface interactions. Methods: A novel in-vitro model was designed to permit either non-pulsatile (N=3) or pulsatile (N=3) recirculation of human heparinized blood (3U/mL) through the TCI HeartMate®. Results: After 1 hr of non-pulsatile flow, the platelet count had declined to 80±4% (mean±SD) of initial levels compared to 60±7% (p < 0.05) with pulsatile flow. Compared to pulsatile flow at 3 hrs, non-pulsatile flow was associated with greater hemolysis, platelet fragmentation, decreased platelet responsiveness and decline in white blood cell count Experiments recirculating blood without a device (N=3) showed no alterations to blood components. Cell count after trypsin-EDTA washes showed that with both non-pulsatile and pulsatile flow the majority of the adherent platelets was observed on the titanium surface (40±8* 108 and 51±9* 108, p>0.05) as compared to the polyurethane membrane (5±4* 108 and 6±3* 108, p>0.05). White blood cells demonstrated a similar affinity for the titanium surface. Conclusions: In the TCI HeartMate®, in-vitro non-pulsatile recirculation is associated with more cell trauma than is pulsatile recirculation. Both types of flow are associated with significant adherence of platelets and white blood cells within the device, particularly to the titanium surface. Acute adhesion of platelets and white blood cells may represent a necessary precursor step for the later formation of the non-thrombogenic neo-intima.