BACKGROUND: METHODS: RESULTS: Acute ischemic stroke patients had shorter R (4·8 ± 1·5 vs. 6·0 ± 1·7 min, P = 0·0004), greater α Angle (65·0 ± 7·6 vs. 61·5 ± 5·9°, P = 0·01), and shorter K (1·7 ± 0·7 vs. 2·1 ± 0·7 min, P = 0·002) indicating faster clotting. Additionally, a subset formed clots with stronger platelet-fibrin matrices. Treatment with tissue plasminogen activator resulted in reduction in all indices of clot strength (LY30 = 0 (0–0·4) vs. 94·4 (15·2–95·3) P < 0·0001); however, there was considerable variability in response. CONCLUSIONS