Role of low-molecular-weight heparins in the management of patients with unstable angina pectoris and non-Q-wave acute myocardial infarction

Antithrombotic therapy in the early phase of non-ST-elevation acute coronary syndromes: a systematic review and meta-analysis

Aims

Despite the increasing use of early invasive strategies in non-ST-elevation acute coronary syndromes (NSTE-ACS), optimal initial antithrombotic therapy (ATT) based on the safety/efficacy profile of all guideline-recommended combinations remains crucial for the early management of both medically and invasively treated NSTE-ACS patients.

Methods and results

Randomized controlled trials on ATT in NSTE-ACS/unstable angina reporting early (within 14 days) major adverse cardiovascular events (MACE) and major bleeding were selected. Overall, 3799 studies were screened, 117 clinical trials were assessed as potentially eligible, 20 trials were included in the study. According to treatment and type of intervention, nine different meta-analyses were performed including a total of 88 748 patients. A significant reduction of trial-defined MACE was found for aspirin vs. placebo [odds ratio (OR), 0.57; 95% confidence interval (CI), 0.34–0.96], heparin vs. placebo (OR, 0.38; 95% CI, 0.15–0.97), aspirin + heparin vs. placebo (OR, 0.32; 95% CI, 0.18–0.59), aspirin + heparin vs. aspirin (OR, 0.57; 95% CI, 0.42–0.79), aspirin + low molecular weight heparin (LMWH) vs. aspirin + unfractionated heparin (UFH; OR, 0.81; 95% CI, 0.69–0.95) and aspirin + ticagrelor/prasugrel + heparins vs. aspirin + clopidogrel + heparins (OR, 0.76; 95% CI, 0.62–0.94). A significant decrease in major bleeding was found only for fondaparinux vs. LMWH on the background of aspirin + clopidogrel (OR, 0.52; 95% CI, 0.44–0.62) despite a clear trend towards increased bleeding for heparin compared to aspirin, aspirin + heparin compared to placebo, aspirin + heparin compared to aspirin, aspirin + P2Y12inhibitors + UFH/LMWH compared to aspirin + UFH/LMWH, and aspirin + ticagrelor/prasugrel + heparins compared to aspirin + clopidogrel + heparins.

Conclusion

To our knowledge, these findings are the first to report the safety and efficacy of all the various combinations of currently recommended ATT for the early management of NSTE-ACS, providing a comprehensive evidence-base to guide decisions depending on the patients’ bleeding risk and treatment strategy.

The role of low-molecular-weight heparins in cardiovascular medicine

Low-molecular-weight heparins (LMWHs) have been shown to be as effective and safe as unfractionated heparin (UFH) for acute phase treatment of acute coronary syndrome in the absence of ST-elevation [unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI)]. LMWHs have practical advantages over UFH, including usual lack of requirement for laboratory monitoring of the anticoagulant response because of their favourable pharmacokinetic properties, and thus represent a simpler and more cost-effective option in clinical practice. The LMWH dalteparin has been shown to provide extended therapy benefit to high-risk UA/NSTEMI patients and can provide a protective bridge until revascularization. While revascularization procedures are now an established intervention for patients with UA/NSTEMI, a new approach for patients who cannot undergo immediate catheter intervention is to continue with medical treatment until revascularization is possible. LMWHs are currently being investigated for use in the catheterization laboratory, in patients undergoing percutaneous coronary intervention procedures, and in conjunction with thrombolytics for treatment of acute myocardial infarction.

The effect of subcutaneously administered low-molecular-weight heparin on microarterial thrombosis in the rat

OBJECTIVE

To examine the effect of administration of a low-molecular-weight heparin derivative, enoxaparin, on the rate of arterial thrombosis in a rat model.

STUDY DESIGN

Prospective, randomized, blinded study.

METHODS

A standard microarterial anastomosis tuck injury was created in both femoral arteries of 25 Long Evans retired breeder rats. Thirteen animals received a subcutaneous injection of 50 IU/kg of enoxaparin 2 hours before the procedure, while 12 control animals received vehicle (isotonic sodium chloride solution) alone. Sites of injury/repair were assessed 2 hours after the procedure for anastomotic patency or thrombosis.

RESULTS

Six (23%) of 26 vessels in the drug-treated group developed an arterial thrombosis at the site of repair, while 6 (25%) of 24 vessels in the control group developed thrombosis. There was no statistically significant difference at the 95% confidence limit between the 2 groups based on a comparison-of-proportions test.

CONCLUSION

The preoperative subcutaneous administration of 50 IU/kg of enoxaparin did not alter the rate of arterial thrombosis following the creation of a thrombogenic tuck injury/repair of the rat femoral artery.

Applying scientific criteria to therapeutic interchange: a balanced analysis of low-molecular-weight heparins

Under pressure to provide cost-effective healthcare, many healthcare systems have adopted Therapeutic Interchange (TI) programs-the interchange of therapeutically equivalent but chemically unique drugs-to reduce the total cost of therapy without compromising patient care. To be appropriate and feasible, a TI program for any class of drugs must meet certain rigorous criteria and undergo medical, financial, tactical, and legal reviews. Moreover, once a TI program is implemented, a process to monitor its success should be established. Application of the TI criteria to low-molecular-weight heparins (LMWHs) reveals that a blanket TI program for LMWHs does not appear advisable at this time.