Changes in platelet activation associated with left ventricular assist system placement

Background: Thromboembolic and hemorrhagic complications are common in patients after left ventricular assist system (LVAS) placement. Platelet physiology may be involved in these complications. Methods: Using flow cytometry, expression of CD62P and CD63 were analyzed as markers of platelet activation. Binding of annexin V was analyzed to determine platelet membrane asymmetry. Results from two patients who received a Novacor LVAS as a bridge to transplantation are reported. Results: Patients' platelets showed increased CD62P and CD63 expression, yet annexin V binding was not increased. They also revealed suppression of thrombin activation following LVAS placement, which approached normal after transplantation. Heparin suppressed thrombin activation, whereas aspirin or dipyridamole did not. Suppression was attenuated by protamine sulfate and heparinase. Conclusions: Following LVAS placement, resting platelets demonstrate increased expression of activation markers.