Low molecular weight heparin decreases rebound ischemia in unstable anginaor non-Q-wave myocardial infarction: The Canadian ESSENCE ST segment monitoring substudy

OBJECTIVES The goal of this study was to determine whether enoxaparin was m ore effective than heparin in reducing recurrent ischemic episodes. BACKGROUND Continuous ST segment monitoring is a simple tool for assessment of ischemia and identifies patients with a worse prognosis. Little is know n about the impact of low molecular weight heparin on ST segment shift. METHODS Patients were randomized to receive enoxaparin or heparin (mean 3.4 days). Three-lead ST segment monitoring was performed for the first 48 h ( n = 220) and an additional 38 h (n = 174) after intravenous study drug disc ontinuation (mean 1.9 days later). RESULTS During initial monitoring, ischemia rates were similar among the he parin and enoxaparin groups (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). After drug: discontinuation, ischemic e pisodes occurred more frequently (44.6% vs. 25.6%, p = 0.009), and the tota l ischemic duration was greater among heparin patients (18 +/- 39 vs. 5 +/- 12 min/24 h, p = 0.005). Recurrent ischemia occurred more frequently after discontinuation in the heparin (46% vs. 31%, p = 0.043), but not the enoxa parin, group (18.4%, vs. 25%, p = 0.33). Regardless of treatment, patients with ischemia were more likely to die or experience (re)infarction at one y ear (18.4% vs. 8.3%, p = 0.023). CONCLUSIONS ST segment shift occurs frequently in unstable angina/non-Q-wav e myocardial infarction despite antithrombotic therapy and is associated wi th worse one-year prognosis. Enoxaparin is a more effective antithrombotic treatment than unfractionated heparin and leads to greater prevention of re bound ischemia. (C) 2000 by the American College of Cardiology.