LMW Heparin the Preferred Therapy in ST-Elevation MI

June 3, 2007
Jill Stein

Internal Medicine World Report, May 2006, Volume 0, Issue 0

ATLANTA—The low-molecular-weight (LMW) heparin enoxaparin (Lovenox) has the edge over unfractionated heparin as adjunctive therapy with fibrinolysis in patients with ST-elevation myocardial infarction (MI), investigators announced at a late-breaking clinical trials session at the 55th annual scientific session of the American College of Cardiology.

New England Journal of Medicine

The data, from the Enoxaparin versus Unfractionated Heparin with Fibrinolysis for ST-Elevation Myocardial Infarction (ExTRACT-TIMI 25) trial, were also published in the (2006;354: 1477-1488).

Lead investigator Elliott M. Antman, MD, director, Samuel A. Levine Cardiac Unit, Brigham and Women’s Hospital, Boston, and colleagues elsewhere randomized 20,506 patients with MI who received thrombolytic therapy to a strategy involving either enoxaparin throughout the index hospitalization or unfractionated heparin for at least 48 hours.

“Thrombolytic therapy is the most popular method of reperfusion used worldwide for patients with ST-elevation MI, and current guidelines recommend the use of a thrombolytic combined with aspirin plus routine administration of unfractionated heparin,” Dr Antman explained. “Our study provides strong evidence of the superiority of the enoxaparin strategy over the standard unfractionated heparin.”


The primary efficacy end point was death or nonfatal recurrent MI through 30 days. It occurred in 12% of patients randomized to unfractionated heparin and 9.9% of those assigned to enoxaparin, which translates into a 17% reduction in relative risk ( <.001). The benefits of the LMW heparin strategy became apparent within 48 hours.


Recurrent nonfatal MI was significantly reduced by 33% in patients receiving enoxaparin compared with unfractionated heparin. Overall, 7.5% of the unfractionated heparin group died versus 6.9% of the enoxaparin group ( = .11).


Major bleeding occurred in 2.1% of the enoxaparin group versus 1.4% of the unfractionated heparin group ( <.001). However, the net clinical benefit supported the enoxaparin strategy.

These results mean that for every 1000 patients treated with the enoxaparin strategy, there would be 15 fewer nonfatal reinfarctions, 7 fewer episodes of urgent revascularization, as well as 6 fewer deaths.

Although there would also be 4 additional episodes of nonfatal major bleeding, the number of nonfatal intracranial hemorrhages would not increase.