Contemporary anticoagulation therapy in patients undergoing percutaneous intervention

The proper use of anticoagulants is crucial for ensuring optimal patient outcomes post percutaneous interventions in the cardiac catheterization laboratory. Anticoagulant agents such as unfractionated heparin, a thrombin inhibitor; low-molecular weight heparins, predominantly Factor Xa inhibitors; fondaparinux, a Factor Xa inhibitor and bivalirudin, a direct thrombin inhibitor have been developed to target various steps in the coagulation cascade to prevent formation of thrombin. Optimal anticoagulation achieves the correct balance between thrombosis and bleeding and is related to optimal outcomes with minimal complications. This review will discuss the mechanisms and appropriate use of current and emerging anticoagulant therapies used during percutaneous interventions.     

Current and future antithrombotic agents in children

Thromboembolic complications are increasing in children, and the use of anticoagulation has seen a dramatic increase despite the lack of randomized clinical trials. The most widely used agents in children are heparin and warfarin, however these agents have limitations that are exaggerated in children. This has led to the use of newer agents with improved pharmacologic properties such as low-molecular-weight heparin, however, the use of novel agents such as direct thrombin inhibitors has been limited to case reports. These agents, however, have potential advantages over heparin, low-molecular-weight heparin and warfarin. Current clinical trials are in progress to define the proper dose of two such agents--argatroban (Argatroban, GlaxoSmithKline) and bivalirudin (Angiomax, The Medicines Company). The selective Factor Xa inhibitor fondaparinux (Arixtra, Sanofi-Synthelabo) has not been used in children; however, there are situations in which this agent may be advantageous. This review will discuss the currently available agents, with an emphasis on those that are novel and their potential uses in children.     

The use of adjunctive anticoagulants in patients with acute coronary syndrome transitioning to percutaneous coronary intervention

Patients presenting to the Emergency Department (ED) need to be quickly diagnosed, risk-stratified, and treated accordingly. Anticoagulants used in the ED should be easy to use and suitable for all patients with acute coronary syndromes, regardless of treatment strategy. In patients with ST-segment myocardial infarction, current guidelines recommend unfractionated heparin regardless of reperfusion strategy or low-molecular-weight heparin (LMWH) as an alternative in patients undergoing percutaneous coronary intervention (PCI). The LMWH enoxaparin is approved for ST-segment elevation myocardial infarction patients managed medically or undergoing PCI. The recently updated American College of Cardiology/American Heart Association guidelines for patients with unstable angina or non-ST-segment elevation myocardial infarction recommend unfractionated heparin or the LMWH enoxaparin (class IA recommendation), or the factor Xa inhibitor fondaparinux or the direct thrombin inhibitor bivalirudin (class IB recommendation) for patients managed invasively. This review discusses each of these anticoagulant options in the context of patients transitioning to PCI.     

Bivalirudin: a direct thrombin inhibitor

BACKGROUND: Studies of the anticoagulant effects of hirudin, which is derived from the saliva of the leech Hirudo medicinalis, led to the development of compounds that can directly inhibit thrombin activity without the need for additional cofactors. One of these is the direct thrombin inhibitor bivalirudin, which has recently been approved by the US Food and Drug Administration for use as an anticoagulant in patients with unstable angina undergoing percutaneous transluminal coronary angioplasty. OBJECTIVE: This is a review of the pharmacologic properties, efficacy, tolerability, and potential cost-effectiveness of bivalirudin in the treatment of ischemic coronary syndromes. METHODS: Articles were identified by searches of MEDLINE (1966-September 2001), International Pharmaceutical Abstracts (1970-September 2001), and the Iowa Drug Information Service (1966-September 2001) using the terms bivalirudin and Hirulog. The reference lists of retrieved articles were also reviewed for relevant articles. RESULTS: Bivalirudin is a synthetic polypeptide that directly inhibits thrombin by binding simultaneously to its active catalytic site and its substrate recognition site. After intravenous administration, peak plasma concentrations occur in 2 minutes. In patients given a 1.0-mg/kg bolus followed by a 2.5-mg/kg per hour infusion, a median activated clotting time of 346 seconds is achieved with little interpatient or intrapatient variability. Clearance of bivalirudin occurs through a combination of renal elimination and proteolytic cleavage, and doses may need to be decreased in the presence of renal dysfunction. In patients undergoing percutaneous coronary interventions, bivalirudin has been associated with equivalent efficacy but lower bleeding rates (P < 0.001) than unfractionated heparin (UFH). Data from the Hirulog Early Reperfusion/Occlusion-2 study suggest no reduction in mortality with bivalirudin compared with heparin when either is added to aspirin and streptokinase in patients with acute myocardial infarction, despite a lower reinfarction rate (P < 0.001). Experience with bivalirudin in patients with unstable angina and heparin-induced thrombocytopenia (HIT), as well as in patients receiving glycoprotein IIb/IIIla inhibitors, is limited. The differences in bleeding rates between bivalirudin and heparin in published clinical trials probably reflect differences in levels of anticoagulation achieved in comparator groups. CONCLUSIONS: Given its high cost, bivalirudin should be reserved for use as an alternative to UFH, primarily in patients with HIT, until clinical trials have more clearly demonstrated its benefits in terms of efficacy or safety.     

Drugs for percutaneous coronary interventions

Many combinations of anticoagulants and antiplatelet drugs have been used to treat patients undergoing a percutaneous coronary intervention (PCI). Among anticoagulants, enoxaparin has some theoretical advantages over unfractionated heparin, but in clinical trials no advantage in outcome has been demonstrated in PCI. Bivalirudin, a direct thrombin inhibitor, has been associated with a lower risk of bleeding than unfractionated heparin. Among antiplatelet drugs, use of clopidogrel plus aspirin has led to a reduction in cardiovascular events; all patients undergoing PCI should receive both. Addition of a GP IIb/IIIa inhibitor may lower mortality rates further, particularly in high-risk patients such as diabetics.     

Comparative cost-effectiveness of anticoagulation with bivalirudin or heparin with and without a glycoprotein IIb/IIIa-receptor inhibitor in patients undergoing percutaneous coronary intervention in Sweden: a decision-analytic model

OBJECTIVE: This study modeled the comparative costs and effectiveness of anticoagulation with bivalirudin alone, heparin alone, and heparin combined with a glycoprotein IIb/IIIa-receptor inhibitor (GPI) in patients undergoing percutaneous coronary intervention (PCI) in Sweden. METHODS: GPIs are prescribed for -40% to 50% of patients undergoing PCI in Sweden. However, because treatment practices vary between hospitals, the model analyzed a cohort in which different proportions of patients (0%-100%) would receive a GPI in addition to heparin and the remaining patients would receive heparin monotherapy. This mixed cohort was compared with a cohort treated with bivalirudin. Abciximab was used as the GPI comparator, as this is the only GPI currently approved in Sweden for patients undergoing PCI. Pooled data from 3 studies (REPLACE-2 [second Randomized Evaluation of PCI Linking Angiomax to Reduced Clinical Events], ESPRIT [European/Australasian Stroke Prevention in Reversible Ischaemia Trial], and EPISTENT [Evaluation of Platelet IIb/IIIa Inhibitor for Stenting]) were used as the source for the probabilities of myocardial infarction (MI), urgent revascularization (UR), major and minor bleeding (Thrombolysis in Myocardial Infarction study definitions), and death. Treatment costs associated with these complications were obtained from 4 Swedish hospitals, and official drug prices were obtained from the Swedish Pharmacopoeia. All costs were presented in 2006 Swedish kronor (SEK). The model was evaluated over a 30-day time frame from the perspective of a Swedish hospital. The modeled patient population was 63 years old, weighed 78 kg, and was 75% male. RESULTS: Compared with a pattern in which heparin plus a GPI was used in 50% of all PCIs and heparin alone was used in the remaining 50%, bivalirudin treatment was associated with a significant reduction in all complications in the model (P < 0.05), including a mean of 18.2 fewer MIs, 1.6 fewer URs, 15.3 fewer bleeding events, and 1.3 fewer deaths per 1000 treated patients. Bivalirudin therapy also was associated with a significant reduction in total drug and health care costs per patient (SEK -1301; 95% Cl, -1367 to -1229). The benefit of bivalirudin was sensitive to the rate of GPI use: additional reductions in rates of MI, UR, and death were seen at lower rates of GPI use, and additional reductions in rates of bleeding and costs of drugs and health care utilization were seen at higher rates of GPI use. CONCLUSIONS: In this model, anticoagulation with bivalirudin in patients undergoing PCI was cost-effective compared with heparin alone and heparin plus a GPI. In a hypothetical Swedish hospital unit using equal proportions of heparin alone and heparin plus a GPI, a switch to bivalirudin would reduce the risk of both ischemic events and bleeding events, resulting in savings in total drug and health care costs.     

Bivalirudin use in carotid endarterectomy in a patient with heparin-induced thrombocytopenia

OBJECTIVE: To describe the successful use of bivalirudin as the primary procedural anticoagulant in a patient with suspected heparin-induced thrombocytopenia (HIT) undergoing carotid endarterectomy (CEA). CASE SUMMARY: A 73-year-old white man presented for an elective CEA 3 weeks after emergent, on-pump coronary artery bypass grafting. Bivalirudin was used for procedural anticoagulation because of seropositivity for heparin-PF4 antibodies and a clinical history consistent with HIT. The dose was administered as a 0.75 mg/kg bolus and 1.75 mg/kg/h infusion as reported in percutaneous coronary intervention, based on review of the available bivalirudin literature. The dosage was adjusted for the patient's renal dysfunction. The outcome was successful, with the patient discharged home in 8 days without significant complications. DISCUSSION: During active HIT, when thrombocytopenia and heparin-PF4 antibodies are present, heparin therapy must be avoided. In patients with subacute HIT, when platelet counts have recovered but HIT antibodies are still present, it is also prudent to avoid heparin administration. In the case of a patient in whom anticoagulation is necessary but heparin use is contraindicated, a direct thrombin inhibitor, such as bivalirudin, may offer a viable alternative. Bivalirudin is not immunogenic and does not cross-react with the heparin-PF4 antibodies associated with HIT. To our knowledge, as of January 20, 2006, this is the first report of the use of bivalirudin for procedural anticoagulation during CEA in a patient with HIT antibodies and recent exposure to heparin. CONCLUSIONS: Further investigation is warranted to clarify the clinical benefits of bivalirudin for patients undergoing vascular surgery of the carotids, including potential advantages for vulnerable patient populations such as those with diagnosed or suspected HIT as well as those with renal dysfunction.     

Bivalirudin,a bivalent,thrombin specific anticoagulant as an alternative to heparin in interventional procedures as an alternative to heparin in interventional procedures

Among the antithrombotic therapies evaluated to date, the synthetic peptide bivalirudin is unique in its ability to reduce both ischemic and bleeding complications associated with percutaneous coronary intervention (PCI). Bivalirudin is a small peptide consisting of 20 amino acid residues that binds thrombin in a direct, reversible, and bivalent fashion. The agent is approved for use in the United States and New Zealand as an anticoagulant in patients with unstable angina undergoing PCI and may also prove beneficial in patients with acute coronary syndromes (ACS), acute myocardial infarction (AMI) and in patients undergoing coronary artery bypass graft (CABG) procedures. This article examines bivalirudin in more detail.     

Enoxaparin in acute coronary syndromes

Enoxaparin is a low-molecular-weight heparin (LMWH) derivative that exerts its anticoagulant activity through antithrombin III, an endogenous inhibitor of factor Xa and thrombin IIa. Unlike its unfractionated heparin (UFH) counterparts, enoxaparin has a greater bioavailability, lower incidence of heparin-induced thrombocytopenia and more stable and predictable anticoagulation, allowing fixed dosing without the need for monitoring. These advantages make it an attractive anticoagulant to be used in acute coronary syndrome management. Indeed, several clinical trials and meta-analyses have consistently demonstrated the efficacy of enoxaparin in reducing cardiovascular events and mortality in this population. Although initial clinical trials with enoxaparin during the early conservative approach suggested superior efficacy without differences in safety compared with UFH, emerging data in the current era of early revascularization approach indicate that superior effects of enoxaparin over heparin in reducing clinical events should be balanced against an increase in major hemorrhagic complications. Enoxaparin is a rational alternative to UFH in patients presenting with either unstable angina/non-ST-elevation myocardial infarction or ST-elevation myocardial infarction, with a clinically modest increase in bleeding complications.     

Direct and indirect antithrombins in acute coronary syndromes

Unfractionated heparin (UFH) as well as low-molecular-weight heparins (LMWH), especially enoxaparin, are recommended by the current international guidelines for routine used in the conservative treatment of patients with acute coronary syndromes (ACS). UFH is still the recommended antithrombin as soon as percutaneous coronary interventions (PCI) are performed, although the results of different trials clearly have demonstrated the benefit of enoxaparin also in interventional cardiology. Bleeding complications along PCI procedures can be minimized by avoiding crossover from enoxaparin to UFH or vice versa and by reducing the dosage of indirect antithrombins, particularly of enoxaparin, in patients with chronic renal dysfunction and/or the elderly. Especially for those patient groups, bivalirudin offers already today an effective alternative. There is increasing expectation concerning the use of bivalirudin in patients undergoing PCI procedures but firm data exist at present only for low- and medium-risk patients with non ST-elevation ACS. Results of still ongoing trials (ACUITY, HORIZONS) will help to further confirm the role of bivalirudin in patients with high-risk acute coronary syndromes. For other direct antithrombins, e.g., fondaparinux (a pentasaccharide) or melagatran, comparably few data are available at present. Whether these agents will make their way into clinical use, future will tell.     

Clinical development of bivalirudin (Angiox): rationale for thrombin-specific anticoagulation in percutaneous coronary intervention and acute coronary syndromes

As the pathophysiology of acute coronary syndromes (ACS) has been clarified in recent years, major advances have been made in the management of the disease. The magnitude of the thrombotic process triggered upon plaque disruption is modulated by different elements that determine plaque and blood thrombogenicity. Thrombin plays a pivotal role in ACS because of its extensive procoagulant and prothrombotic actions. Antithrombotic therapy and powerful antiplatelet therapies, in addition to early percutaneous coronary intervention (PCI), have become central in the management of ACS. A number of options for anticoagulation regimens are available. However, many agents currently used have significant limitations, recognition of which has led to the development, evaluation and clinical introduction of the class of thrombin-specific anticoagulant agents. This paper will discuss the clinical development of the direct thrombin inhibitor bivalirudin as the core anticoagulant in the contemporary PCI setting and the implications for its use in ACS.     

Efficacy and safety of bivalirudin versus heparins in reduction of cardiac outcomes in acute coronary syndrome and percutaneous coronary interventions

Recent data suggest that bivalirudin, a reversible direct thrombin inhibitor, may be noninferior to heparins (unfractionated heparin/low molecular weight heparin) in providing protection against cardiovascular events, with significantly fewer bleeding complications. Whether this advantage is consistent has not been fully defined. We evaluated cardiac outcomes with bivalirudin vs the heparins in management of acute coronary syndromes (ACS), including patients undergoing percutaneous coronary interventions (PCI). Formal computer-aided searches of electronic databases (MEDLINE, PubMed, Cochrane Controlled Trials Registry) were performed by scrutiny of the reference lists of trials and review articles, abstracts, meeting proceedings, and the manufacturers of direct thrombin inhibitors. Five randomized controlled trials (BAT, 1995; CACHET, 2002; REPLACE-2, 2003; REPLACE-1, 2004; and ACUITY, 2006) comparing bivalirudin to the heparins in patients with ACS, including patients undergoing PCI, were identified. The meta-analysis consisted of 25 457 patients (bivalirudin, 15 077; heparins, 10 380). The primary safety end point was major bleeding, defined as intracranial, intraocular, or retroperitoneal hemorrhage; clinically overt blood loss leading to a hemoglobin drop exceeding 3 g/dL (or 10% of hematocrit) and transfusion of 2 or more units of whole blood or packed red blood cells. The combined relative risks (RR) across all of the studies and the 95% confidence intervals of death, myocardial infarction (MI), and revascularization (bivalirudin vs heparins) were computed using the Mantel-Haenszel fixed-effect model, whereas the random-effect model was used for major bleeding. A 2-sided alpha error < .05 was considered to be significant. There were no significant differences in patient characteristics between the 2 groups. Compared to the heparins, the risk of death, MI, revascularization, and composite ischemic end points were similar with bivalirudin monotherapy. However, the risk of major bleeding was significantly lower with bivalirudin use (RR = 0.553; 95% CI = 0.402-0.761; P = .001). The present meta-analysis suggests that bivalirudin may be noninferior to the heparins in reducing the composite of ischemic end points. Additionally, compared to the heparins, bivalirudin monotherapy may lower the rate of major bleeding.     

Bivalirudin: a review of the pharmacology and clinical application

Among the current agents in the class of direct thrombin inhibitors, bivalirudin (Angiomax(?), The Medicines Company, NJ, USA) has seen increased use in cardiovascular medicine over the past decade through its primary indication as an anticoagulant used during percutaneous coronary interventions. Bivalirudin has been further investigated and used as the anticoagulation strategy in the setting of cardiac and endovascular surgical procedures and is frequently utilized in the management of patients with heparin-induced thrombocytopenia. In comparison with heparin, bivalirudin exhibits a low immunogenic profile and provides similar or reduced major bleeding rates as well as a predictable degree of anticoagulation that is dose related. Bivalirudin primarily undergoes dual elimination via proteolytic cleavage and renal elimination, and requires dose adjustment in the setting of severe renal dysfunction. Given the body of supportive data, bivalirudin is likely to continue to figure prominently as a reliable and efficient anticoagulation strategy. Additional agents in the class of direct thrombin inhibitors are under investigation and may find increasing clinical use.     

Bivalirudin: a review of the pharmacology and clinical application

Among the current agents in the class of direct thrombin inhibitors, bivalirudin (Angiomax^®, The Medicines Company, NJ, USA) has seen increased use in cardiovascular medicine over the past decade through its primary indication as an anticoagulant used during percutaneous coronary interventions. Bivalirudin has been further investigated and used as the anticoagulation strategy in the setting of cardiac and endovascular surgical procedures and is frequently utilized in the management of patients with heparin-induced thrombocytopenia. In comparison with heparin, bivalirudin exhibits a low immunogenic profile and provides similar or reduced major bleeding rates as well as a predictable degree of anticoagulation that is dose related. Bivalirudin primarily undergoes dual elimination via proteolytic cleavage and renal elimination, and requires dose adjustment in the setting of severe renal dysfunction. Given the body of supportive data, bivalirudin is likely to continue to figure prominently as a reliable and efficient anticoagulation strategy. Additional agents in the class of direct thrombin inhibitors are under investigation and may find increasing clinical use.     

Bivalirudin in ST-segment-elevation myocardial infarction: for better or worse?

Bivalirudin and heparin are the major available parenteral anticoagulants for percutaneous coronary intervention (PCI) in ST-segment-elevation myocardial infarction. Even though hard clinical outcomes are comparable with both drugs, bivalirudin appears to be safer (less bleeding events) at the expense of lower short-term efficacy (more acute stent thrombosis events). The selection of anticoagulation during PCI in ST-segment-elevation myocardial infarction should be individualized, taking into account the patient’s ischemic and bleeding risk. In patients with increased bleeding risk, bivalirudin might be preferable to heparin, whereas in complex PCI with increased risk for stent thrombosis, heparin is preferable. Further clinical studies are needed to elucidate the role of these drugs in PCI for ST-segment-elevation myocardial infarction in the era of radial approaches, new potent antiplatelet agents and the use of glycoprotein IIb/IIIa inhibitors.     

Primary percutaneous coronary intervention in acute myocardial infarction

Primary percutaneous coronary intervention (PCI) has emerged as the preferred therapy for acute ST-segment elevation myocardial infarction (STEMI), as multiple randomized clinical trials and pooled analyses have shown improved clinical outcomes compared with medical reperfusion. Unfortunately, medical centers with 24-hour PCI capability are concentrated in urban areas, relegating many patients in the United States to inferior medical reperfusion. Ongoing substantial research efforts are directed at optimizing mechanical reperfusion, including refinements in adjuvant medical therapy and the use of drug-eluting stents in the catheterization laboratory. Research efforts are also focusing on the implementation of streamlined transfer systems from community centers to tertiary care centers, akin to systems used in the trauma model. Furthermore, experience with the performance of primary PCI at community centers without onsite surgical backup is growing. This article summarizes data regarding the current state, challenges, and future directions of primary PCI for STEMI, emphasizing adherence to current American College of Cardiology/American Heart Association guidelines.     

Direct thrombin inhibition during percutaneous coronary intervention in patients with heparin-induced thrombocytopenia

Patients with or at risk of heparin-induced thrombocytopenia (HIT) who are undergoing percutaneous coronary intervention (PCI) are at particular risk of thrombosis due to the prothrombotic nature of HIT and the endovascular disruption from PCI. Patients require aggressive anticoagulation during PCI, and alternative, nonheparin anticoagulation is recommended over heparin in patients with acute or previous HIT. Argatroban, bivalirudin, and lepirudin are nonheparin, fast-acting, parenteral direct thrombin inhibitors (DTIs). Multicenter, prospective studies have demonstrated that argatroban and lepirudin each reduce thrombosis in HIT and that argatroban and bivalirudin each provide adequate anticoagulation during PCI in patients with or at risk of HIT. We review current therapeutic practices with direct thrombin inhibitors in patients with or at risk of HIT during PCI, including individuals requiring periprocedural anticoagulation, and the factors influencing the choice of DTI in this setting.     

Anticoagulation with prostaglandins during extracorporeal circulation

This paper reviews pathophysiological processes occurring after contact of blood with artificial surfaces and the predominant role of platelets in the genesis of extracorporeal thrombosis. Bleeding complications are common during conventional heparin anticoagulation, and both clinical and experimental evidence suggests that the efficacy of heparin as an anticoagulant is compromised by its relative ineffectiveness towards platelets. Consequently, drugs that inhibit interaction between platelets and artificial membranes have been introduced as an alternative anticoagulant strategy. This paper reviews studies on the use of short-acting antiplatelet prostaglandins such as prostacyclin and prostaglandin E1 alone or in combination with heparin during various forms of extracorporeal circulation such as cardiopulmonary bypass, haemodialysis, continuous haemofiltration, membrane oxygenation, ventricular assist devices, and haemoperfusion. Temporary paralysis of platelet function with antiplatelet prostaglandins has been effective in controlling platelet-surface interaction and reducing bleeding complications and morbidity during and after extracorporeal circulation. By inhibiting the formation of fibrin, leukocyte and platelet-based microaggregates and cytoprotective actions, prostaglandins have been shown to prevent renal, neurologic, and pulmonary dysfunction after extracorporeal circulation. Prostaglandins were most effective in increasing the biocompatibility of extracorporeal systems when they were administered as a supplement to but not as a substitute for heparin. The use of prostaglandins alone should be reserved for patients who are resistant to heparin or heparin-induced thrombocytopenia.     

Long-term care after percutaneous coronary intervention: focus on the role of antiplatelet therapy

Arterial wall injury caused by percutaneous coronary intervention (PCI) triggers transient platelet activation and mural thrombosis; these effects are superimposed on the preexisting platelet hyperreactivity associated with underlying atherothrombosis. Platelet activation has been implicated in the major complications of PCI: acute and subacute thrombosis and restenosis. Antithrombotic and anticoagulant therapy minimizes thrombotic complications after PCI. Aspirin plus a thienopyridine (ticlopidine or clopidogrel) is more effective than aspirin plus heparin and extended warfarin therapy in preventing periprocedural ischemic events and subsequent stent thrombosis and results in less major and minor bleeding. Dual antiplatelet therapy with aspirin and clopidogrel (the preferred thienopyridine because of its superior hematologic safety) is recommended for at least 4 weeks to prevent subacute stent thrombosis with bare-metal stents and 3 to 6 months to prevent late-stent thrombosis with drug-eluting stents. Coronary atherothrombosis is a diffuse vascular disease, and reduction of the risk of future ischemic events requires strategies that extend beyond the focal treatment of stenotic lesions. Optimal long-term care after PCI requires aggressive systemic pharmacotherapy (antiplatelet agents, statins, beta-blockers, and angiotensin-converting enzyme Inhibitors) in conjunction with therapeutic lifestyle changes (smoking cessation, weight reduction, dietary measures, and exercise). In this context, dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 12 months after PCI for prophylaxis of future atherothrombotic events.     

Clinical application of enoxaparin

Low-molecular-weight heparins have several important advantages over unfractionated heparin (UFH). Due to a longer plasma half life together with high bioavailability and a linear dose-response relationship, the drugs can be safely and effectively administered in the hospital or ambulatory settings without the need to monitor the anticoagulant effect. Enoxaparin (Lovenox), Aventis Pharma) is a low-molecular-weight heparin which has been studied in a variety of clinical situations. In general surgery the efficacy of enoxaparin to prevent venous thromboembolism is similar to UFH but the tolerability is better. In patients undergoing cancer, orthopedic or vascular surgery the efficacy of enoxaparin is significantly higher with similar rates of bleeding complications. The database for enoxaparin in nonsurgical patients is smaller compared with surgical groups. There is evidence that the efficacy of enoxaparin may be superior to UFH in patients with severe cardiac disease. Efficacy and safety of UFH and enoxaparin are similar for the treatment of deep vein thrombosis. However, enoxaparin can be safely administered by the patients at home which is not possible with UFH. In patients with acute coronary syndromes, enoxaparin has been shown to reduce the rate of deaths and serious cardiac events in comparison with UFH. Furthermore, exonaparin treatment has been shown to be cost-effective, and therefore is the therapy of choice in this setting. In addition, enoxaparin has been shown to be a safe and effective alternative to the combination of UFH and phenprocoumone therapy in patients undergoing electrical cardioversion for atrial fibrillation.