Unstable angina / non ST elevation myocardial infarction low molecular weight heparin therapy


 * Associate Editors-in-Chief: Varun Kumar, M.B.B.S.; Lakshmi Gopalakrishnan, M.B.B.S.; Smita Kohli, M.D.

Low Molecular Weight Heparin(LMWH)
Mechanism of benefit:
 * LMWH combine factor IIa and factor Xa inhibition and thus inhibit both the action and generation of thrombin.
 * It has a number of advantages over UFH such as its greater anti-factor Xa activity inhibits thrombin generation more effectively, lower rate of thrombocytopenia, high bioavailabiltiy, more consistent anticoagulant effect and no requirement of intensive lab monitoring.

Clinical trial data:
 * Results from TIMI 11B study showed superiority of LMWH over UFH for reducing a composite of death and serious cardiac ischemic events during the acute management of Unstable angina/NQMI patients without causing a significant increase in the rate of major hemorrhage.
 * Results from SYNERGY trial revealed noninferiority of LMWH over UFH for the treatment of high-risk patients with non-ST-segment elevation ACS. However, both trials did show increased risk of major bleeding with LMWH.
 * A prospective analysis of the A to Z trial showed that enoxaparin provided significant benefit over UFH in patients managed conservatively (who are typically on heparin/LMWH for at least 48 hours) but not in those with early invasive approach(who are taken to the catheterization laboratory within 48 hours and have their heparin discontinued thereafter).

Disadvantages of LMWH:
 * LMWH are more affected by renal dysfunction than UFH, and the dose should be reduced in patients with a creatinine clearance <30 mL/min.
 * Also, in the event of bleeding, the anticoagulant effect of UFH can be reversed more effectively with protamine.