Low molecular weight heparin (dalteparin) as adjuvant treatment of thrombolysis in acute myocardial infarction--a pilot study: biochemical markers in acute coronary syndromes (BIOMACS II)

The role of low-molecular-weight heparins in arterial diseases: optimizing antithrombotic therapy

On the basis of current evidence, all patients with acute coronary syndromes should receive optimized medical therapy, whether or not they ultimately undergo an invasive revascularization procedure, to improve both clinical outcomes and cost effectiveness. While standard aspirin and unfractionated heparin (UFH) have improved short-term outcomes, they do not eliminate the risk of recurrent ischemic episodes. The recent introduction of platelet fibrinogen receptor antagonists and low-molecular-weight heparins (LMWHs) has offered an opportunity to develop more aggressive antithrombotic regimens. The LMWHs have been thoroughly evaluated in unstable angina and non-Q wave myocardial infarction (UA/NQMI), and have demonstrated improved efficacy compared to standard UFH, without an increase in major complications caused by bleeding. Experience has also been gathered using LMWHs in other arterial diseases (such as pregnant patients with prosthetic heart valves) and as an adjunctive therapy with thrombolytics for acute myocardial infarction. Lastly, studies are currently underway evaluating LMWHs in patients with atrial fibrillation.

Impact of enoxaparin low molecular weight heparin in patients with Q-wave myocardial infarction

A subgroup meta-analysis from the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-Wave Coronary Events (ESSENCE) and the Thrombolysis in Myocardial Infarction (TIMI) 11B studies has shown that enoxaparin is superior to unfractionated heparin in reducing the composite end points of death, myocardial infarction, and emergency revascularization in patients with Q-wave myocardial infarction. The beneficial treatment effect was significant at 43 days.

Assessment of low-molecular-weight heparin trials in cardiology

This review assesses the trial data for low-molecular-weight heparin (LMWH) use in cardiology. LMWHs have been shown to be more convenient to use compared with unfractionated heparin. The use of LMWHs in prevention and treatment of deep vein thrombosis is now established. Use of LMWHs in cardiology is gathering momentum. The most compelling published data are in unstable angina and non-Q-wave myocardial infarction (MI). LMWHs are at least as effective as unfractionated heparin in terms of the composite endpoint of death and MI. Conclusive benefits of LMWH use to prevent restenosis after stent insertion or percutaneous transluminal coronary angioplasty have not been established. The data in MI and atrial fibrillation are still preliminary, but encouraging.

Low molecular weight heparin in acute coronary syndromes

Traditionally, unfractionated heparin has played an important role in the treatment of acute coronary syndromes. Low molecular weight heparin (LMWH), is a promising new type of heparin, which is fractionated to include only heparin molecules of lower molecular weight. LMWHs are administered subcutaneously and do not require monitoring of the activated partial thromboplastin time, making them much easier to use. LMWHs are combined inhibitors of both thrombin and Factor Xa inhibitors. Several recent large trials in unstable angina and non-Q wave myocardial infarction have shown that LMWH is effective, and one agent has been shown to be superior to unfractionated heparin in reducing death, myocardial infarction, or recurrent angina. They also are very low cost (approximately $50 per day) and appear to be very cost effective in the treatment of unstable angina. Thus, LMWHs appear to be the new anticoagulant agent in acute coronary syndromes.

Clinical trials in acute myocardial infarction

Long-term follow-up of placebo-controlled thrombolysis trials has proven that the survival benefit from thrombolysis in acute myocardial infarction (AMI) is maintained for up to 10 years. Ongoing research is being conducted with the aim to further improve early restoration of blood flow in the infarct vessel and, thus, reperfusion of the infarcted myocardium in patients with AMI, with the ultimate goal to improve survival. In two recent mega-trials, two new single-bolus fibrinolytics (lanoteplase and TNK-tissue plasminogen activator) were shown to be equivalent to front-loaded alteplase in reducing infarct mortality. The ease of application of these agents might help reduce the time from symptom onset to start of therapy. More potent thrombin inhibitors such as hirudin and hirulog seem to speed up thrombolysis with streptokinase and reduce the rate of reinfarctions. Very promising results are derived from angiographic trials combining reduced doses of thrombolytics with glycoprotein IIb/IIIa inhibitors. Advances in mechanical revascularization can be achieved with the use of stents and better conjunctive therapies. All of these developments are expected to further improve clinical outcome of patients with AMI in the near future.