ExTRACT-TIMI 25 ECG Study - ExTRACT-TIMI 25 ECG Study

Description:

The goal of the study was to evaluate the effect of treatment with enoxaparin compared with unfractionated heparin (UFH) on ST-segment resolution (STRes) among patients with or without STRes following ST-segment elevation myocardial infarction (STEMI).

Study Design

Patients Enrolled: 2,304
Mean Follow Up: 30 days
Mean Patient Age: Median age 57 years
Female: 22

Patient Populations:

Patients who met inclusion criteria for the ExTRACT TIMI-25 trial and who had ECGs performed at baseline and at 180 minutes

Exclusions:

Revascularization before the 180-minute ECG (n = 30) or if ECG at baseline had insufficient ST deviation, revealed a left bundle branch block, accelerated idioventricular rhythm, paced rhythm, or were determined to be unreadable due to poor quality

Drug/Procedures Used:

Patients were randomized in a double-blind, double-dummy manner to enoxaparin (n = 1,167) or UFH (n = 1,137). UFH or placebo was given as an intravenous (IV) bolus of 60 U/kg followed by a continuous infusion at 12 U/kg/h, adjusting the rate to maintain an activated partial thromboplastin time of 1.5-2.0 times normal. Enoxaparin was administered as a 30 mg IV bolus followed by 1 mg/kg subcutaneous (SC) injections every 12 hours. For patients 75 years and older or with impaired renal function (creatinine clearance <30 ml/min), IV bolus was omitted and 0.75 mg/kg SC injections were used. The SC enoxaparin regimen was continued until hospital discharge or for a maximum of 8 days.

Principal Findings:

Patients randomized to enoxaparin or UFH treatment arms were similar in all reported baseline characteristics, index presentation and treatment, in time to study drug administration, and in concurrent cardiac medicine use.

Patients were classified as no STRes (<30%, n = 368), partial STRes (30%-70%, n = 830), or complete STRes (>70%, n = 1,100). There was no difference in median STRes (69.4% enoxaparin vs. 67.2% UFH, p = 0.14) or degree of STRes at 180 minutes between the treatment arms. Among patients with complete STRes at 180 minutes, treatment with enoxaparin was associated with a significant reduction in death or nonfatal recurrent MI at 30 days compared with UFH (4.4 vs. 9.9%, p < 0.001).

Rates of death or nonfatal MI in patients with partial STRes (14.2% vs. 12.5%, p = 0.98) and no STRes (16.2% vs. 15.9%, p = 0.97) were similar between treatment enoxaparin and UFH arms, respectively. The rate of nonfatal recurrent MI in patients who achieved complete STRes increased substantially after day 2 in patients in the UFH group, but increased more gradually in the enoxaparin group. The degree of STRes was strongly associated with 30-day mortality (p < 0.001).

Interpretation:

Among STEMI patients who achieve complete STRes, treatment with enoxaparin was associated with a reduction in the primary endpoint of death or nonfatal recurrent MI compared with UFH in patients. Among patients who achieve less STRes, enoxaparin was not associated with a benefit compared with UFH.

These data suggest that the treatment benefit of enoxaparin may be through preventing reocclusion of culprit lesions in patients who achieve initial reperfusion with thrombolysis. The data support the use of anticoagulation with enoxaparin for patients without contraindications who receive fibrinolytic therapy. Moreover, the data reinforce the monitoring for STRes after fibrinolysis, as the degree of STRes has predictive value. Failure to achieve STRes should prompt referral for revascularization. Conversely, patients who achieve early complete STRes and are treated with enoxaparin and antiplatelet therapy can be safely monitored until they are electively referred for catheterization or risk-stratified for medical management, as they are at very low risk for recurrent ischemic complications.

References:

Presented by Dr. Benjamin Scirica at the American Heart Association Annual Scientific Sessions, Chicago, IL, November 2006.

Scirica BM, Morrow DA, Sadowski Z, et al. A strategy of using enoxaparin as adjunctive antithrombin therapy reduces death and recurrent myocardial infarction in patients who achieve early ST-segment resolution after fibrinolytic therapy: the ExTRACT-TIMI 25 ECG study. Eur Heart J. 2007 Sep;28(17):2070-6

Clinical Topics: Anticoagulation Management

Keywords: Thrombolytic Therapy, Myocardial Infarction, Enoxaparin, Fibrinolysis, Referral and Consultation, Partial Thromboplastin Time, Catheterization, Heparin, Electrocardiography, Creatinine


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