In a multicenter, double-blind, double-dummy, parallel group study, patients with acute ST-segment elevation myocardial infarction (STEMI) who were to be hospitalized within 6 hours of onset and were eligible to receive fibrinolytic therapy were randomized in a 1:1 ratio to receive either Lovenox or unfractionated heparin.
Study medication was initiated between 15 minutes before and 30 minutes after the initiation of fibrinolytic therapy. Unfractionated heparin was administered beginning with an IV bolus of 60 U/kg (maximum 4000 U) and followed with an infusion of 12 U/kg per hour (initial maximum 1000 U per hour) that was adjusted to maintain an aPTT of 1.5 to 2 times the control value. The IV infusion was to be given for at least 48 hours. The enoxaparin dosing strategy was adjusted according to the patient's age and renal function. For patients younger than 75 years of age, enoxaparin was given as a single 30 mg intravenous bolus plus a 1 mg/kg SC dose followed by an SC injection of 1 mg/kg every 12 hours. For patients at least 75 years of age, the IV bolus was not given and the SC dose was reduced to 0.75 mg/kg every 12 hours. For patients with severe renal insufficiency (estimated creatinine clearance of less than 30 mL per minute), the dose was to be modified to 1 mg/kg every 24 hours. The SC injections of enoxaparin were given until hospital discharge or for a maximum of eight days (whichever came first). The mean treatment duration for enoxaparin was 6.6 days. The mean treatment duration of unfractionated heparin was 54 hours.
When percutaneous coronary intervention was performed during study medication period, patients received antithrombotic support with blinded study drug. For patients on enoxaparin, the PCI was to be performed on enoxaparin (no switch) using the regimen established in previous studies, i.e. no additional dosing, if the last SC administration was less than 8 hours before balloon inflation, IV bolus of 0.3 mg/kg enoxaparin if the last SC administration was more than 8 hours before balloon inflation.
All patients were treated with aspirin for a minimum of 30 days. Eighty percent of patients received a fibrin-specific agent (19% tenecteplase, 5% reteplase and 55% alteplase) and 20% received streptokinase.
Among 20,479 patients in the ITT population, the mean age was 60 years, and 76% were male. Racial distribution was: 87% Caucasian, 9.8% Asian, 0.2% Black, and 2.8% other. Medical history included previous MI (13%), hypertension (44%), diabetes (15%) and angiographic evidence of CAD (5%). Concomitant medication included aspirin (95%), beta-blockers (86%), ACE inhibitors (78%), statins (70%) and clopidogrel (27%). The MI at entry was anterior in 43%, non-anterior in 56%, and both in 1%.
The primary efficacy end point was the composite of death from any cause or myocardial re-infarction in the first 30 days after randomization. Total follow-up was one year.
The rate of the primary efficacy end point (death or myocardial re-infarction) was 9.9% in the enoxaparin group, and 12.0% in the unfractionated heparin group, a 17% reduction in the relative risk, (P=0.000003) [see Table 25].
Table 25 Efficacy of Lovenox in the Treatment of Acute ST-Segment Elevation Myocardial Infarction | Enoxaparin (N=10,256) | UFH (N=10,223) | Relative Risk (95% CI) | P Value |
|---|
| Note: Urgent revascularization denotes episodes of recurrent myocardial ischemia (without infarction) leading to the clinical decision to perform coronary revascularization during the same hospitalization. CI denotes confidence intervals. |
| Outcome at 48 hours | n (%) | n (%) | | |
| Death or Myocardial Re-infarction | 478 (4.7) | 531 (5.2) | 0.90 (0.80 to 1.01) | 0.08 |
| Death | 383 (3.7) | 390 (3.8) | 0.98 (0.85 to 1.12) | 0.76 |
| Myocardial Re-infarction | 102 (1.0) | 156 (1.5) | 0.65 (0.51 to 0.84) | <0.001 |
| Urgent Revascularization | 74 (0.7) | 96 (0.9) | 0.77 (0.57 to 1.04) | 0.09 |
| Death or Myocardial Re-infarction or Urgent Revascularization | 548 (5.3) | 622 (6.1) | 0.88 (0.79 to 0.98) | 0.02 |
| Outcome at 8 Days | | | | |
| Death or Myocardial Re-infarction | 740 (7.2) | 954 (9.3) | 0.77 (0.71 to 0.85) | <0.001 |
| Death | 559 (5.5) | 605 (5.9) | 0.92 (0.82 to 1.03) | 0.15 |
| Myocardial Re-infarction | 204 (2.0) | 379 (3.7) | 0.54 (0.45 to 0.63) | <0.001 |
| Urgent Revascularization | 145 (1.4) | 247 (2.4) | 0.59 (0.48 to 0.72) | <0.001 |
| Death or Myocardial Re-infarction or Urgent Revascularization | 874 (8.5) | 1181 (11.6) | 0.74 (0.68 to 0.80) | <0.001 |
| Outcome at 30 Days | | | | |
| Primary efficacy endpoint | | | | |
| (Death or Myocardial Re-infarction) | 1017 (9.9) | 1223 (12.0) | 0.83 (0.77 to 0.90) | 0.000003 |
| Death | 708 (6.9) | 765 (7.5) | 0.92 (0.84 to 1.02) | 0.11 |
| Myocardial Re-infarction | 352 (3.4) | 508 (5.0) | 0.69 (0.60 to 0.79) | <0.001 |
| Urgent Revascularization | 213 (2.1) | 286 (2.8) | 0.74 (0.62 to 0.88) | <0.001 |
| Death or Myocardial Re-infarction or Urgent Revascularization | 1199 (11.7) | 1479 (14.5) | 0.81 (0.75 to 0.87) | <0.001 |