Key result
Unfractionated heparin is inferior to newer agents like low-molecular-weight heparins for acute coronary syndromes and will largely be replaced by better antithrombins.
Unfractionated heparin is increasingly being replaced by newer, more predictable antithrombin agents like enoxaparin and bivalirudin in the management of acute coronary syndromes and percutaneous procedures.
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May support preferring newer antithrombins over unfractionated heparin in ACS; leaves open need for updated randomized confirmation.
Acute coronary syndromes (ACS) consist of unstable angina (UA), non-ST-segment myocardial infarction (NSTEMI) and ST-segment myocardial infarction (STEMI). Timely intervention with effective, predictable antithrombin therapy is critically important in the early management of these conditions. Platelet aggregation is also an important component of thrombus formation in arterial thrombosis. Historically, unfractionated heparin (UFH) has been combined with aspirin to suppress thrombin propagation and fibrin formation; however, its effectiveness has been questioned in this setting. Unlike newer anticoagulant alternatives, UFH paradoxically stimulates platelet aggregation, which may further promote clot formation. In addition, obtaining a valid therapeutic activated partial thromboplastin time (aPTT) in cardiology patients is a major challenge, and dosing is complex. Due to substantial variation in reagents and instruments, target aPTT ranges for UFH in ACS clinical trials cannot be extrapolated to individual institutions. Further, the risk of ischemic events is greater shortly after abrupt discontinuation of UFH compared with alternative agents with longer half-lives and less stimulation of platelet aggregation. Key UA-NSTEMI clinical trials have demonstrated that UFH is inferior to newer agents, such as the low-molecular-weight heparins (LMWHs). Consistent with this evidence, the most recent practice guidelines of the American College of Cardiology and the American Heart Association in UA-NSTEMI identify the LMWH enoxaparin as the agent of choice. In patients with STEMI receiving the fibrinolytic tenecteplase as reperfusion therapy, enoxaparin has also been superior to UFH in combination. In percutaneous procedures, newer indirect (enoxaparin) and direct (bivalirudin) antithrombins have demonstrated safety and efficacy. There is little doubt that as we move forward in optimizing adjunctive anticoagulation in the cardiology setting, UFH will largely be replaced by better antithrombin agents.
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Rihn et al. (2004) conducted a review in Acute coronary syndromes (ACS). Unfractionated heparin (UFH) vs. Newer antithrombin agents (e.g., LMWHs, bivalirudin) was evaluated. Unfractionated heparin is inferior to newer agents like low-molecular-weight heparins for acute coronary syndromes and will largely be replaced by better antithrombins.
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