Evolution of early TIMI 2 flow after thrombolysis for acute myocardial infarction. GUSTO-1 Angiographic Investigators.

BACKGROUND Patients with early Thrombolysis in Myocardial Infarction (TIMI) grade 2 flow after thrombolysis appear to have outcomes similar to thrombolytic failures. To evaluate the origin and evolution of early TIMI 2 flow, we examined early and late angiographic and ventriculographic data from the Global Utilization of Streptokinase and TPA for Occluded Arteries (GUSTO-1) angiographic study. METHODS AND RESULTS Of the 914 patients with both 90-minute and 5- to 7-day catheterizations, 278 patients had TIMI grade 2 flow at 90 minutes. At follow-up, 188 (67%) had improved to TIMI grade 3 flow. At 90 minutes, patients with TIMI grade 2 flow had greater infarct vessel narrowing and a significantly greater incidence of thrombus than patients with TIMI grade 3 flow. At the 5- to 7-day follow-up, patients whose flow had improved from TIMI grade 2 at 90 minutes to grade 3 flow at follow-up had larger-caliber vessels (minimum luminal diameter, 0.99 +/- 0.47 versus 0.84 +/- 0.48 mm; P = .03) and a lower incidence of visible thrombus (26% versus 38%, P = .04) than those with persistent TIMI grade 2 flow. These patients also had a higher mean ejection fraction (57.5 +/- 14.1% versus 52.8 +/- 12.9%, P = .02) and better infarct zone wall motion (-2.1 +/- 1.5 versus -2.6 +/- 1.3 SD per chord, P = .01) at the 5- to 7-day follow-up. Patients in whom flow improved from TIMI grade 2 at 90 minutes to TIMI grade 3 by 5 to 7 days had significantly better left ventricular function than patients with persistent TIMI grade 0, 1, or 2 flow and constituted a group whose left ventricular function was intermediate between those who had no reperfusion (TIMI grades 0 and 1) and those whose reperfusion was complete (TIMI grade 3). CONCLUSIONS These data suggest that incomplete clot lysis plays a significant role in the pathogenesis of TIMI grade 2 flow. Furthermore, early TIMI grade 2 flow may be sufficient to provide prolonged myocyte viability, which will further recover if flow normalizes.