Low-molecular-weight heparins in coronary stenting (the ENTICES trial). ENoxaparin and TIClopidine after Elective Stenting

Low molecular weight heparins for arterial thrombosis

The use of low molecular weight heparin (LMWH) for the prevention and treatment of venous thromboembolism has been validated by numerous clinical trials and meta-analyses over the past 25 years. More recently, the possibility of extending treatment with LMWH to the arterial disease where thrombosis is a prominent feature has led to the planning of many clinical trials, several of which have been already published. LMWH has been tested in settings such as acute coronary syndromes, including myocardial infarction, surgery or percutaneous revascularization for coronary and peripheral arteries, and stroke. In most indications, LMWH has proved to be superior to or at least as effective as unfractionated heparin and it is also easier to administer.

Unfractionated and Low-Molecular-Weight Heparins, Basic Mechanism of Action and Pharmacology

Unfractionated heparin has enjoyed sole anticoagulant status for nearly 50 years. Despite a dramatic growth in the development and the introduction of many newer anticoagulant and antithrombotic drugs and polytherapeutic approaches during the past decade, unfractionated and low-molecular-weight heparins remain the drugs of choice for many indications, including surgical anticoagulation, interventional cardiology, and in several additional considerations. Unfractionated heparin has a major role in the areas of vascular medicine and surgery, and it is the only parenteral anticoagulant drug that can be empirically neutralized by such agents as protamine sulfate. The development of low and ultra low-molecularweight heparins, which are a class of depolymerized heparin derivatives with distinct pharmacologic profiles that are largely determined by their composition, represents a refinement for the use of heparin. These drugs produce their major effects by combining with antithrombin Ill and exerting antithrombin and anti-Xa inhibition. The low-molecular-weight heparins also increase non-antithrombin III-dependent effects, such as tissue factor pathway inhibitor release, modulation of adhesion molecules, and the release of profibrinolytic and antithrombotic mediators from the blood vessels. Each of the low-molecular-weight heparins has different cumulative effects, and each product exhibits a distinct profile. Initially developed for the prophylaxis of postsurgical deep vein thrombosis, these drugs are now also used for the treatment of both venous and arterial thrombotic disorders. To a large extent, the low-molecular-weight heparins have replaced unfractionated heparin in most of the subcutaneous indications. This has resulted in a dramatic evolution in anticoagulant management that allows patients with thrombotic disorders to be treated in an outpatient setting. Thus, the introduction of low-molecular-weight heparins represents a major advance in improving the use of heparin. Generic versions of these drugs are likely to be developed as their patents expire. Currently, there are no clear guidelines for the acceptance of the generic versions of branded products. To avoid safety and efficacy-related problems, a generic drug must meet both the chemical and biologic equivalence criterion. Synthetically and biosynthetically derived agents such, as pentasaccharide, will also be introduced for clinical use; however, these drugs will have a narrower therapeutic spectrum due to their monotherapeutic nature. Heparin and its derivatives will continue to have a crucial role in the management of thrombotic and cardiovascular disorders in years to come.

Enoxaparin: a pharmacologic and clinical review

INTRODUCTION

Both arterial and venous thromboembolism constitute a significant disease burden worldwide, leading to major use of healthcare resources. As anticoagulants play a pivotal role in the treatment of these disorders, it is vital for healthcare providers to have sufficient knowledge of their biochemical and clinical attributes.

AREAS COVERED

Enoxaparin is one of the most commonly used low-molecular-weight heparins in a wide variety of thromboembolic disorders and has several advantages over unfractionated heparin. An analysis of its biophysical profile, with special emphasis on pharmacokinetic and pharmacodynamic properties, is undertaken in this article. In addition, most recent major clinical studies elucidating its role in common thromboembolic conditions are discussed, while keeping the historical perspective at hand. Readers will be able to understand the pharmacologic properties of enoxaparin with their clinical relevance for day-to-day use and critically analyze the amount and weight of scientific evidence behind its use in various disorders.

EXPERT OPINION

In summary, enoxaparin has been shown, by a vast amount of scientific data, to be a safe and effective agent in the treatment of a whole spectrum of acute coronary syndromes, with similar efficacy and safety in the prevention and treatment of venous thromboembolism.

A novel strategy for managing clopidogrel-induced adverse skin reactions

AIMS

We conducted a prospective observational study using a course of steroids and antihistamines to treat a cohort of patients who developed skin reactions to clopidogrel, to assess whether dual antiplatelet therapy could be continued in an outpatient setting.

METHODS AND RESULTS

This study included 2,701 patients who underwent percutaneous coronary intervention (PCI) at our centre over a 23 month period. Patients with skin reactions to clopidogrel were identified and then commenced on five days oral prednisolone (30 mg/od) and chlorpheniramine (4 mg/tds) for seven days. A subsequent telephone survey was performed to evaluate a number of variables. The probability of the adverse reaction being secondary to clopidogrel was assessed using the Naranjo adverse drug reaction probability scale. Twenty (0.7%) patients were identified who developed adverse skin reactions to clopidogrel. There was complete resolution seen in the majority (89%) of patients within an average of 3.2 days following treatment. One patient had partial resolution, and one had no response to treatment, but both were able to continue clopidogrel.

CONCLUSIONS

We propose a novel, safe and effective way of managing clopidogrel-induced skin reactions using a short course of prednisolone and chlorpheniramine, without stopping or substituting clopidogrel.

Antithrombotic therapy for percutaneous coronary intervention

This article outlines the antiplatelet and antithrombotic therapy used in contemporary percutaneous coronary interventions. It is a comprehensive review of past and present pharmacologic agents and includes a discussion of the more promising potential future therapies. The clinical trials that provide the basis for the current standard of care are provided, as are ongoing trials that will likely shape the future standard. This article is not intended to provide a detailed discussion of precise mechanistic or structural features of each agent but to serve as a practical clinical guide to the interventionalist when choosing specific pharmacotherapies for specific patients in the catheterization laboratory.

Antithrombotic controversies in off-pump coronary bypass

The purpose of this article is to evaluate the use of perioperative antithrombotics in patients undergoing surgical revascularization of the coronary vessels. Although there is a general agreement about the use of anticoagulation during off-pump coronary revascularization (OPCAB), the degree of the required anticoagulation varies from one center to another. The review is divided into four major sections. The first section describes the pathophysiology of the coagulation system in cardiac surgery with and without the use of cardiopulmonary bypass. In this section, we also discuss the interactions between the coagulation system and the inflammatory response to cardiac surgery. The second section examines the role of prophylactic antithrombosis in patients referred to surgical revascularization, and their role in bleeding complications associated with surgery. Heparinization and neutralizing its anticoagulative effects during coronary surgery are discussed in the third section. The fourth section examines the evidence that the inflammatory response contributes to adverse peri-operative events, in particular organ dysfunction, and potential therapeutic strategies to control this response. The review concludes with a summary of potential future research directions and key deficiencies in our knowledge regarding the use of anticoagulants in cardiac surgery.

Modulating thrombotic potential in catheter-based percutaneous coronary and peripheral vascular interventions

Thrombosis is an obligatory consequence of all percutaneous vascular interventions. Balloon angioplasty, intravascular stents and other devices routinely used to facilitate dilatation of critical vascular stenoses result in fracture of the intima and exposure of the thrombogenic subendothelium with initiation and perpetuation of platelet activation and aggregation. This not uncommonly results in thrombus formation that may lead to abrupt vessel closure, distal ischemia and tissue infarction, and target organ dysfunction. Fortunately, advances in our understanding of the mechanisms that underlie vascular thrombosis have led to advances in the use of adjunctive pharmacological agents that modulate this pathophysiological response and have led to important reductions in the incidence and severity of thrombotic complications of percutaneous transluminal interventions.

Pharmacodynamic and pharmacokinetic properties of enoxaparin : implications for clinical practice

Enoxaparin is a low-molecular-weight heparin (LMWH) that differs substantially from unfractionated heparin (UFH) in its pharmacodynamic and pharmacokinetic properties. Some of the pharmacodynamic features of enoxaparin that distinguish it from UFH are a higher ratio of anti-Xa to anti-IIa activity, more consistent release of tissue factor pathway inhibitor, weaker interactions with platelets and less inhibition of bone formation. Enoxaparin has a higher and more consistent bioavailability after subcutaneous administration than UFH, a longer plasma half-life and is less strongly bound to plasma proteins. These properties mean that enoxaparin provides a more reliable anticoagulant effect without the need for laboratory monitoring, and also offers the convenience of once-daily administration. Clinical studies have confirmed that these pharmacological advantages translate into improved outcomes. There are important pharmacokinetic and pharmacodynamic differences between enoxaparin, other LMWHs and UFH, and therefore these molecules cannot be regarded as interchangeable.

Clopidogrel induced urticarial rash in a patient with left main stem percutaneous coronary intervention: management issues

Clopidogrel, an ideal treatment for prevention of subacute stent thrombosis, may not be feasible to use in every patient. Ticlopidine (plus aspirin) is a very good alternative, although the risks of life threatening neutropenia should mandate regular monitoring of blood counts. It is proposed that patients undergoing angioplasty and stenting should carry a warning card in an effort to make the public and general practitioners aware that antiplatelet treatment after angioplasty plays an important part in ensuring successful outcome.

Periprocedural thromboprophylaxis in patients receiving chronic anticoagulation therapy

Patients receiving chronic anticoagulation therapy pose a clinical challenge when therapy needs to be interrupted for surgical or invasive procedures. Maintaining anticoagulation places them at risk for serious bleeding complications, whereas discontinuing anticoagulation puts them at risk of thromboembolic complications. Most patients can undergo dental procedures, cataract surgery, and diagnostic endoscopy without discontinuing anticoagulation. The main patient groups that may require a periprocedural alternative to oral anticoagulation (periprocedural thromboprophylaxis or bridging) include patients with prosthetic heart valves, atrial fibrillation, and hypercoagulable states and patients with chronic venous thrombosis who are undergoing surgery. Currently, there is little consensus on the appropriate perioperative treatment of patients on long-term warfarin therapy. There are an increasing number of studies that evaluate the benefits of periprocedural bridging with low-molecular-weight heparin (LMWH) in place of unfractionated heparin (UFH). An advantage of LMWH over UFH is that perioperative conversion from warfarin therapy with LMWH can be carried out in the outpatient setting, which is more convenient for patients and is cost effective. As with the use of UFH, there are reports of maternal thromboembolic complications with LMWHs in pregnant women with mechanical heart valves. This review brings together the available data on periprocedural bridging to assess the available options for patients on long-term warfarin therapy who are undergoing surgical procedures. It provides a rationale for using LMWHs while individualizing the risks versus benefits in a given patient population.

Postprocedural low molecular weight heparin in patients at high risk of subacute stent thrombosis

BACKGROUND

Subacute stent thrombosis (SAT) is a dramatic complication of percutaneous coronary stenting occurring in 0.4-20% of cases depending on several angiographic and clinical variables. The role of postprocedural low molecular weight heparin (LMWH) in preventing early events after high-risk PCI is not well established. In this study we describe our experience with postprocedural LMWH in patients deemed to be at high risk of SAT.

METHODS

Thirty-six patients who were treated with subcutaneous LMWH for at least 7 days after the intervention were identified from our database. All cineangiograms and charts were retrospectively reviewed to confirm the high-risk intervention properties. Thirty-day and long-term major adverse coronary events (MACEs) were documented in all patients.

RESULTS

The most common indications for LMWH were the deployment of > or =3 consecutive stents, the presence of intracoronary thrombus or ulceration, poststenting residual stenosis, contraindication to aspirin or thienopyrideines, and persistent dissection. The majority of patients (61%) had > or =2 risk factors. Mean postprocedural treatment period was 12+/-3 days. At 30 days, none of the patients experienced a MACE including death, myocardial infarction, and repeat revascularization. No major bleeding occurred and one patient (2.7%) had a minor bleeding. At a mean follow-up of 31 months, MACE occurred in 17% of patients.

CONCLUSIONS

Postprocedural LMWH is safe and effective in preventing SAT in patients undergoing high-risk coronary intervention.

Ambulatory use of ticlopidine and clopidogrel in association with percutaneous coronary revascularization procedures in a national managed care organization

The aim of this study was to quantify ambulatory use of ticlopidine and clopidogrel in association with percutaneous coronary revascularization procedures (PTCA, atherectomy, stent) in a national managed care organization. Retrospective administrative claims data over a 3-year period (1996-1998) from 12 UnitedHealth Group-affiliated health plans in four geographic regions were collected. Pharmacy and medical claims data were used to determine the patients exposed to ticlopidine and clopidogrel between January 1, 1996 and December 31, 1998, the duration of use, prescriptions within 2 weeks of a coronary procedure, and stent patients prescribed either drug within 2 weeks of stent placement in 1998. Substantial short-term use of ticlopidine and clopidogrel was found. The percentage of members with duration of use < or = 30 days ranged from 50.4% in 1996 to 56.9% in 1998 for ticlopidine and was 52.7% for clopidogrel. In 1998, 46% and 33% of ticlopidine and clopidogrel users, respectively, had a medical claim for a coronary procedure that fell within 2 weeks of a prescription. The rate was lower for Medicare beneficiaries. In 1998, 78% of stent patients filled a prescription for either drug within 2 weeks of stent implantation. Although little difference was found overall in the use of these agents across geographic regions, a higher proportion of stent patients in the Southeast were prescribed ticlopidine within this time frame. The findings suggest that during the study time period ticlopidine and clopidogrel are frequently used off-label in association with percutaneous coronary revascularization procedures. These results were important in considering the overall benefit-risk profile.

Safety and efficacy of only 2 weeks of ticlopidine therapy in patients at increased risk of coronary stent thrombosis: results from the Antiplatelet Therapy alone versus Lovenox plus Antiplatelet therapy in patients at increased risk of Stent Thrombosis (ATLAST) trial

BACKGROUND

Controversy exists regarding the frequency of late stent thrombosis among patients treated with intracoronary stents and the most appropriate duration of treatment with a thienopyridine that is required to prevent this complication.

METHODS

We analyzed the frequency of stent thrombosis and other ischemic events in the Antiplatelet Therapy alone versus Lovenox plus Antiplatelet therapy in patients at increased risk of Stent Thrombosis (ATLAST) trial. In the ATLAST trial, 1102 patients at increased risk of stent thrombosis (ST-elevation myocardial infarction within 48 hours, diffuse distal disease, a large amount of thrombus, acute closure, residual dissection, etc) were randomly assigned to receive either enoxaparin (40 or 60 mg given every 12 hours for 14 days) or placebo; all patients received aspirin (325 mg daily) and ticlopidine (250 mg twice daily) for only 14 days.

RESULTS

The primary end point, the 30-day combined incidence of death, nonfatal myocardial infarction, and urgent revascularization, was reached in 2.3% of patients (1.8% of patients taking enoxaparin vs 2.7% of patients taking placebo; P =.295). However, during the 15th through 30th days, the frequency of ischemic events was only 0.73%, and only 0.27% (3/1102) of patients had possible stent thrombosis (95% CI 0.06, 0.77).

CONCLUSION

The frequency of stent thrombosis and other adverse ischemic events in the 15th through 30th days after stent placement in even high-risk stent patients treated with ticlopidine for only 2 weeks is low whether or not enoxaparin is administered.

A randomized, placebo-controlled trial of enoxaparin after high-risk coronary stenting: the ATLAST trial

OBJECTIVES

We performed a multicenter, double-blind placebo-controlled trial to examine the efficacy and safety of enoxaparin in patients at high risk for stent thrombosis (ST).

BACKGROUND

The optimal antithrombotic regimen for such patients is unknown.

METHODS

We randomized 1,102 patients with clinical, angiographic or ultrasonographic features associated with an increased risk of ST to receive either twice-daily injections of weight-adjusted enoxaparin or placebo for 14 days after stenting. All patients received aspirin and ticlopidine. The primary end point was a 30-day composite end point of death, myocardial infarction (MI) or urgent revascularization.

RESULTS

The target enrollment for the study was 2,000 patients. However, the trial was terminated prematurely at 1,102 patients after interim analysis revealed an unexpectedly low event rate. The primary outcome occurred in 1.8% enoxaparin-treated patients versus 2.7% treated with placebo (odds ratio [OR] 0.66; 95% confidence interval [CI] 0.29 to 1.5, p = 0.30); for death or MI the rates were 0.9% vs. 2.2%, respectively (OR 0.41, 95% CI 0.14 to 1.2, p =0.13); and for MI, 0.4% vs. 1.6%, respectively (OR 0.22, 95% CI 0.05 to 0.99, p = 0.04). The groups had comparable rates of major bleeding (3.3% for enoxaparin, 1.6% for placebo, p =0.08), but minor nuisance bleeding was increased with enoxaparin (25% vs. 5.1%, p < 0.001).

CONCLUSIONS

The clinical outcomes of patients at increased risk of ST are more favorable than previously reported, rendering routine oral antiplatelet therapy adequate for most. However, given its relative safety and potential to reduce the risk of subsequent infarction, a 14-day course of enoxaparin may be considered for carefully selected patients.

Developing a novel antithrombotic in the academic environment

In recent years, academic research institutions have increasingly sought to commercialize their discoveries, providing the opportunity to raise venture capital and benefit financially from their developments. In the last 6 years, Hamilton Civic Hospitals Research Center, affiliated with McMaster University, Ontario, Canada, has set up two companies, Vascular Therapeutics and Osteokine, to commercialize its discoveries in thrombosis and osteoporosis. Epidemiological evidence shows a continuing socioeconomic burden of both of these disorders, thereby offering opportunities for new drug development. Key areas in the field of thrombosis include novel parenteral anticoagulants to replace heparin as adjunctive therapy in acute coronary syndromes, safer and more practical oral anticoagulants that do not require monitoring to replace coumarins, and oral antiplatelet drugs for use in combination with aspirin. Since their creation, Vascular Therapeutics and Osteokine have attracted major funding and developed several patentable compounds that show clinical and commercial promise.

Ticlopidine versus oral anticoagulation for coronary stenting

BACKGROUND

A 2-4 week course of ticlopidine plus aspirin following coronary stenting is considered effective in preventing thrombotic occlusion of the stented vessel and safe in regards to bleeding and peripheral vascular complications. However, rare, although potentially life-threatening haematological complications have been reported with this drug regimen.

OBJECTIVES

To evaluate the efficacy and safety of ticlopidine plus aspirin versus oral anticoagulants after coronary stenting

SEARCH STRATEGY

Electronic search of the Cochrane Library, Medline, Embase from 1991 to June 1999; references from trials and experts.

SELECTION CRITERIA

Randomised controlled trials comparing ticlopidine plus aspirin versus oral anticoagulants (either with or without aspirin) after elective or bail out coronary stenting.

DATA COLLECTION AND ANALYSIS

Three reviewers assessed trial quality and compiled data on outcomes including: total mortality, non fatal myocardial infarction and revascularization occurring within the first 30 days after hospitalization, stent thrombosis on angiography, major and minor bleeding, neutropenia, thrombocytopenia, thrombotic thrombocytopenic purpura.

MAIN RESULTS

Four trials (n=2436 patients) were included. Ticlopidine plus aspirin compared to oral anticoagulants significantly reduced the risk of non-fatal acute myocardial infarction and revascularization at 30 days, combined negative events (mortality, myocardial infarction, revascularization at 30 days) (RR: 0.41; 95% CI: 0.25-0.69; NNT for 30 days: 22; 95% CI: 14-45), and major bleeding (RR in high quality studies: 0.24; 95% CI: 0.07-0.79). Ticlopidine plus aspirin compared to oral anticoagulants significantly increased the risk of eutropenia, thrombocytopenia and neutropenia (RR 5; 95% CI: 1.08-13.07; NNT for 30 days: 142; 95% CI: 76-1000). Ticlopidine plus aspirin vs oral anticoagulation did not affect all cause mortality. Ticlopidine plus aspirin significantly reduced the risk of stent thrombosis (angiography) which was seen only on studies with blinded outcome assessment (RR: 0.14; 95% CI: 0.03-0.60; NNT for 30 days: 33; 95% CI:16-166). Minor bleeding was reported only in one study and no studies recorded thrombotic thrombocytopenic purpura (TTP).

REVIEWER'S CONCLUSIONS

Ticlopidine plus aspirin after coronary stenting is effective in reducing the risk of the revascularization, non fatal myocardial infarction and bleeding complications when compared with oral anticoagulants. No effect is observed on total mortality. However, the haematological side effects of ticlopidine are still a matter of concern, and strict monitoring of blood-cell counts is recommended. Physicians should also be aware of the possibility of rare although potentially life-threatening complications such as TTP

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.

Low-molecular-weight heparin in patients with non-ST-segment elevation acute coronary syndrome: role in the emergency department

Intravenous unfractionated heparin (UFH) has been shown to be an effective therapy in reducing the risk of death or myocardial infarction in patients with unstable angina. Low molecular weight heparins demonstrate improved pharmacologic and pharmacokinetic properties relative to standard heparin, and these advantages have been translated into similar or even greater clinical efficacy in several large-scale clinical trials evaluating their use. The simple mode of administration and lack of dependency on anticoagulation monitoring make low-molecular-weight heparins an extremely attractive option in the treatment of patients with acute ischemic coronary syndromes presenting without persistent ST-segment elevation.

Antithrombotic Therapy during and after Intracoronary Stenting

Objective:

To evaluate the impact on patient outcomes of antithrombotic therapy during and after intracoronary stenting.

Data Sources:

A MEDLINE search (1966-July 2000) for English-language clinical trials and review articles using the search terms stent and coronary with one or more of the following search terms: abciximab, tirofiban, orofiban, xemilofiban, eptifibatide, aspirin, heparin, enoxaparin, tinzaparin, dalteparin, hirudin, danaparoid, dipyridamole, cilostazol, dextran, warfarin, anticoagulant, ticlopidine, and Clopidogrel. References from these articles were reviewed for additional articles. Pharmaceutical companies were contacted to identify unpublished studies. A total of 177 sources were initially identified.

Study Selection:

Studies were selected through an unblinded individual review for prospective, randomized clinical trials evaluating patient outcomes related to antithrombotic therapy during or after intracoronary stent placement. Additional human and animal studies were included for background and introductory information.

Data Extraction:

Patient characteristics in each study were compared with those of the overall stent population. The primary end point measurements were defined. The completeness of follow-up and power analysis was assessed.

Data Synthesis:

Intracoronary stenting is now a common modality for maintaining patency of occluded arteries. Antithrombotic therapy during coronary artery stent placement is changing as knowledge about the pathophysiology of thrombus formation expands and new medications become available. Development of new stent placement techniques, new stent designs, and methods of restenosis irradiation or prevention have coincided with evolving antithrombotic regimens.

Conclusions:

The current antithrombotic regimen used in coronary artery stenting is complex, but has a lower incidence of hemorrhagic complications and thrombosis compared with previous anticoagulant regimens. Antithrombotic therapy may need to be tailored to individual patient contraindications.

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 syndrome: evidence for superior or equivalent efficacy compared with unfractionated heparin?

This article will review the results of recent clinical trials evaluating low molecular weight heparins (LMWHs) in the management of patients with acute coronary syndromes of unstable angina and non-ST segment elevation MI. Low molecular weight heparins are a new class of anticoagulants that have a number of advantages over unfractionated heparin (UFH) leading to their increasing use for thrombotic vascular disorders. There is convincing evidence that LMWH is more effective than placebo and at least as effective as UFH in reducing the hard end points of death and recurrent myocardial infarction. Convincing evidence for a superior efficacy is mostly limited to the least robust but most prevalent end point of recurrent angina, and benefits appear to be confined predominantly to high-risk patients. The benefits are sustained long-term, but there appears to be no incremental benefit with prolonged treatment. The risk for major bleeding is approximately equivalent to UFH, but minor hemorrhage is clearly increased, especially with vascular instrumentation. The increased bleeding risk together with its long half-life and absence of specific antidote warrants exercising caution when using LMWH with coronary intervention. Low molecular weight heparins have the potential of being cost-neutral or even cost-saving by reducing resource utilization, especially in the setting of aggressive interventional practice pattern. Last, the issue of whether one LMWH preparation is more effective and cost-effective than others remains an open question that can be answered only by direct head-to-head comparison of different LMWH preparations in randomized trials. In conclusion, subcutaneous weight-adjusted LMWH is as effective and safe as intravenous UFH in the management of patients with acute coronary syndromes. The logistic ease of administration without the need for monitoring anticoagulation appears to be the major advantage over UFH.