The greatest benefit of enoxaparin over unfractionated heparin in acute coronary syndromes is achieved in patients presenting with ST-segment changes: the Enoxaparin in Non-Q-Wave Coronary Events (ESSENCE) Electrocardiogram Core Laboratory Substudy.

Background: We undertook a prospective electrocardiogram (ECG) substudy in the ESSENCE trial and hypothesized that patient subgroups with ST-segment deviation would experience greater benefit from enoxaparin, as compared with unfractionated heparin (UFH).

Methods: Of the 3171 patients in the trial, 3087 had a qualifying ECG available for analysis by the core laboratory. Patients were divided into 4 mutually exclusive groups based upon the qualifying ECG: (1) ST-segment elevation, (2) ST-segment depression, (3) T-wave inversions, or (4) others.

Results: The 30-day and 1-year primary outcomes (death, myocardial infarction, or recurrent angina) were significantly lower among patients with ST elevation or ST depression who received enoxaparin, as compared with UFH (20.8% vs 28.0%, P = .0019 and 32% vs 40.4%, P = .0011, respectively). The greatest absolute benefit of enoxaparin over UFH was seen in patients with ST depression (primary end point at 30 days, 24.6% vs 32.4%, P = .018; at 1 year, 35.5% vs 44.5%, P = .012).

Conclusion: Specific recognition of patients with ST-segment depression appears to identify those not only at high risk for adverse outcome, but also patients most likely to derive the greatest benefit from enoxaparin, as compared with UFH therapy.