Deposition of fibrin in the Dacron vascular graft segments. Means are shown with SEM. This highly thrombogenic 0.25-mL section of the device was not sensitive for the detection of antithrombotic effects of the lower yet clinically effective doses of the LMWH. Overall, the inhibitory effects were negligible to moderate. The most pronounced decrease in fibrin deposition was observed during treatment with the highest dose of LMWH (2600 μg/kg), followed by comparable inhibition by 8.3 μg/kg PCA and 1300 μg/kg LMWH. The decrease in fibrin deposition by the lower doses of LMWH (325 and 650 μg/kg) and the lower APC dose (28 μg/kg) did not reach statistical significance.