Low molecular weight heparin decreases rebound ischemia in unstable angina or non-Q-wave myocardial infarction: The Canadian ESSENCE ST segment monitoring substudy. - ESSENCE ST Segment Monitoring Substudy

Description:

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

Hypothesis:

To evaluate the impact of low molecular weight heparin versus unfractionated heparin on ST segment shift and on the reoccurrence of ST segment deviations on discontinuation of the drug (rebound) in patients with unstable angina and non-Q wave infarction.

Study Design

Study Design:

Drug/Procedures Used:

Patients with unstable angina or non Q wave infarction were randomized to receive enoxaparin or heparin (mean 3.4 days) in addition to aspirin and other standard treatments. Three-lead ST segment monitoring was performed for the first 48 h (n = 220) and an additional 48 h (n = 174) after intravenous study drug discontinuation. Transient ST-segment shifts were defined as indicative of ischemia.

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.

Interpretation:

Despite the fact that enoxaparin was more effective than unfractionated heparin in preventing rebound, approximately 1 of 3 patients on such therapy (along with aspirin) had ST segment shifts on continuous ECG monitoring. The addition of IIb/IIIa antagonist to enoxaparin and aspirin along with early invasive strategies in appropriate high-risk patients should help to further decrease the incidence of rebound ischemia.

References:

1. Goodman SG, Barr A, Sobtchouk A, et al. J Am Coll Cardiol 2000;36:1507-13.

Clinical Topics: Anticoagulation Management

Keywords: Myocardial Infarction, Enoxaparin, Heparin, Low-Molecular-Weight, Fibrinolytic Agents, Electrocardiography


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