PPXbd inhibits fibrin generation at low [TF]wall under venous conditions. Anticoagulated whole blood (CTI, 4 μg/mL) was treated with PPXbd (250 μg/mL) and was perfused over collagen or collagen/TF surface at 100 s−1 (constant Q). (A-C) Platelet deposition on collagen was unaffected by PPXbd despite the difference in [TF]wall. (D-F) Fibrin generation was inhibited by PPXbd only on collagen/low [TF]wall surface but not on collagen or collagen/high [TF]wall surface. *P < .05; **P < .01.