Principal Findings:

Ischemia rates were similar among the heparin and enoxaparin groups during the first 48 hours (27.2% vs. 22.6%, p = 0.44); however, the time to first ischemic episode was earlier among heparin-treated patients (11 ± 11 vs. 25 ± 18 min, p = 0.001). Rebound ischemic episodes occurred more frequently (44.6% vs. 25.6%, P = 0.009), and the total ischemic duration was greater among heparin than in enoxiparin treated patients (18 ± 39 vs. 5 ± 12 min/24 h, P = 0.005). In patients that had both pre- and post drug ST segment monitoring, recurrent ischemia occurred more frequently after discontinuation in the heparin (46% vs. 31%, p = 0.043), but not the enoxaparin, group (18.4% vs. 25%, p = 0.33). Mortality and reinfarction at 1 year were frequent in patients with recurrent ischemia in both treatment groups (18.4% vs. 8.3%, P = 0.023).

ST segment shift occurs frequently in unstable coronary syndromes despite antithrombotic therapy and is associated with worse one-year outcomes. Enoxaparin is a more effective antithrombotic treatment than unfractionated heparin and leads to greater reduction in the frequency of rebound ischemia.