Unfractionated and low-molecular-weight heparin as adjuncts to thrombolysis in aspirin-treated patients with ST-elevation acute myocardial infarction: a meta-analysis of the randomized trials

Safety and efficacy of intracoronary thrombolytic agents during primary percutaneous coronary intervention for STEMI

INTRODUCTION

Large thrombus burden in patients with ST elevation myocardial infarction (STEMI) is associated with higher rates of distal embolization, no-reflow phenomenon, abrupt closure, stent thrombosis, major adverse cardiovascular events (MACE), and mortality. Intracoronary (IC) thrombolytic agents are theoretically attractive as an adjunct to primary percutaneous coronary intervention (PPCI) as they activate endogenous fibrinolysis which results in degradation of the cross-linked fibrin matrix in coronary thrombus.

AREAS COVERED

We reviewed published studies reporting on intraprocedural anti-thrombus strategies used during PPCI including randomized controlled trials and observational studies.

EXPERT OPINION

Published studies are limited by small sample size and heterogeneity due to variation in indication, inclusion criteria, thrombolytic agent, dose, delivery mechanisms, antiplatelet and anticoagulant regimen, timing in regard to reperfusion, PCI techniques, and endpoints. Despite these limitations, data are consistent that IC administration of thrombolytic agents at low doses is associated with low rates of bleeding and vascular complications. While there is currently no compelling data demonstrating a benefit to the routine use of IC thrombolytic therapy in patients with STEMI, there is suggestive data that IC thrombolysis may have benefit in selected patients.

[The new Epoch of Antithrombotic Therapy in the Long-Term Prevention of a non-Cardioembolic Stroke]

This article presents current opinions on the role of antithrombotic therapy in secondary prevention of cardiovascular diseases (CVD) in patients after noncardioembolic stroke or a transient ischemic attack on the background of sinus rhythm. This review analytically analyses evidence-based data on antithrombotic drugs used for this secondary prevention. Despite the fact that acetylsalicylic acid (ASA) is still a "gold standard" for prevention of noncardioembolic stroke, the search for rational combinations of antithrombotic drugs to increase the effectiveness of preventive treatment is relevant. The question whether the rivaroxaban treatment as monotherapy or in combination with ASA is more effective than the ASA monotherapy for secondary prevention of cardiovascular complications (CVC) was addressed in the COMPASS study. In that study, three regimens of antithrombotic therapy were compared in patients with stable atherosclerotic CVD: rivaroxaban (2.5 mg twice a day) in combination with ASA (100 mg/day); rivaroxaban (5 mg twice a day); and ASA (100 mg/day). Risk for development of major CVC (death, stroke, myocardial infarction (IM)) was lower (p<0.001) in the rivaroxaban+ASA combination treatment group than in the ASA monotherapy group; however, the risk of major bleedings was somewhat higher. Total risk based on the definition of "pure clinical benefit" was lower for the rivaroxaban+ASA combination treatment than for the ASA monotherapy. The rivaroxaban monotherapy did not result in a significant decrease in the risk of major CVC compared to the ASA monotherapy but significantly increased the risk of major bleedings. Incidence of repeated ischemic stroke for a year was 1.1% for the combination therapy, 2.6% for the rivaroxaban therapy, and 3.4% for the ASA monotherapy with significant differences between the combination treatment group and the ASA monotherapy group (p<0.01). Relative risk of repeated stroke was 67% lower for the combination therapy group compared to the ASA monotherapy group. The combination of rivaroxaban (2.5 mg twice a day) and ASA (100 mg) opens a new epoch of antithrombotic treatment for primary and secondary prevention of stroke in patients with a stable atherosclerotic CVD and sinus rhythm.

The Novel Coronavirus Disease (COVID-19) and Its Impact on Cardiovascular Disease

The coronavirus disease 2019 (COVID-19) pandemic has placed a significant strain on healthcare providers. As the number of patients continue to surge, healthcare workers are now forced to find different approaches to practicing medicine that may affect patient care. In addition, COVID-19 has many cardiovascular complications that affect the clinical course of patients. In this article, we summarize the cardiovascular impact of COVID-19 and some of the challenges that patients and the healthcare system will face during this pandemic.

Stroke Outcomes in the COMPASS Trial

BACKGROUND

Strokes were significantly reduced by the combination of rivaroxaban plus aspirin in comparison with aspirin in the COMPASS trial (Cardiovascular Outcomes for People Using Anticoagulation Strategies). We present detailed analyses of stroke by type, predictors, and antithrombotic effects in key subgroups.

METHODS

Participants had stable coronary artery or peripheral artery disease and were randomly assigned to receive aspirin 100 mg once daily (n=9126), rivaroxaban 5 mg twice daily (n=9117), or rivaroxaban 2.5 mg twice daily plus aspirin (n=9152). Patients who required anticoagulation or had a stroke within 1 month, previous lacunar stroke, or intracerebral hemorrhage were excluded.

RESULTS

During a mean follow-up of 23 months, fewer patients had strokes in the rivaroxaban plus aspirin group than in the aspirin group (83 [0.9% per year] versus 142 [1.6% per year]; hazard ratio [HR], 0.58; 95% CI, 0.44-0.76; P<0.0001). Ischemic/uncertain strokes were reduced by nearly half (68 [0.7% per year] versus 132 [1.4% per year]; HR, 0.51; 95% CI, 0.38-0.68; P<0.0001) by the combination in comparison with aspirin. No significant difference was noted in the occurrence of stroke in the rivaroxaban alone group in comparison with aspirin: annualized rate of 0.7% (HR, 0.82; 95% CI, 0.65-1.05). The occurrence of fatal and disabling stroke (modified Rankin Scale, 3-6) was decreased by the combination (32 [0.3% per year] versus 55 [0.6% per year]; HR, 0.58; 95% CI, 0.37-0.89; P=0.01). Independent predictors of stroke were prior stroke, hypertension, systolic blood pressure at baseline, age, diabetes mellitus, and Asian ethnicity. Prior stroke was the strongest predictor of incident stroke (HR, 3.63; 95% CI, 2.65-4.97; P<0.0001) and was associated with a 3.4% per year rate of stroke recurrence on aspirin. The effect of the combination in comparison with aspirin was consistent across subgroups with high stroke risk, including those with prior stroke.

CONCLUSIONS

Low-dose rivaroxaban plus aspirin is an important new antithrombotic option for primary and secondary stroke prevention in patients with clinical atherosclerosis.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01776424.

Modern Management of ST-Segment Elevation Myocardial Infarction

Disruption of intracoronary plaque with thrombus formation resulting in severe or total occlusion of the culprit coronary artery provides the pathophysiologic foundation for ST-segment elevation myocardial infarction (STEMI). Management of STEMI focuses on timely restoration of coronary blood flow along with antithrombotic therapies and secondary prevention strategies. The purpose of this review is to discuss the epidemiology, pathophysiology, and diagnosis of STEMI. In addition, the review will focus on guideline-directed therapy for these patients and review potential associated complications.

Parenteral anticoagulants in heart disease: Current status and perspectives (Section II)

Anticoagulants are a mainstay of cardiovascular therapy, and parenteral anticoagulants have widespread use in cardiology, especially in acute situations. Parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins, the synthetic pentasaccharides fondaparinux, idraparinux and idrabiotaparinux, and parenteral direct thrombin inhibitors. The several shortcomings of unfractionated heparin and of low-molecular-weight heparins have prompted the development of the other newer agents. Here we review the mechanisms of action, pharmacological properties and side effects of parenteral anticoagulants used in the management of coronary heart disease treated with or without percutaneous coronary interventions, cardioversion for atrial fibrillation, and prosthetic heart valves and valve repair. Using an evidence-based approach, we describe the results of completed clinical trials, highlight ongoing research with currently available agents, and recommend therapeutic options for specific heart diseases.

ExTRACT-TIMI 25 trial: clarifying the role of enoxaparin in patients with ST-elevation myocardial infarction receiving fibrinolysis

Pharmacologic reperfusion remains the most common treatment strategy for ST-elevation myocardial infarction (STEMI) worldwide. Unfractionated heparin (UFH) is the established adjunctive antithrombotic agent used with fibrinolytic agents. Low-molecular-weight heparins (LMWHs) are a potential alternative to UFH, but have not been evaluated in large cohorts of patients. The Enoxaparin and Thrombolysis Reperfusion for Acute Myocardial Infarction Treatment (ExTRACT)-Thrombolysis in Myocardial Infarction (TIMI) 25 was a double-blind, double-dummy randomized controlled trial, of 20,479 patients, which demonstrated the superiority of enoxaparin over UFH in reducing death or nonfatal myocardial infarction (MI) at 30 days, with an increase in major bleeding. The composite of death, nonfatal MI and nonfatal intracranial hemorrhage, was reduced with enoxaparin. Elderly patients (> or = 75 years of age) received a novel enoxaparin dosing regimen and when compared with UFH, benefited from a lower relative bleeding risk than younger patients without compromising efficacy in preventing death or MI. Intracranial hemorrhage rates were similar. The net clinical benefit of enoxaparin over UFH was maintained regardless of whether patients were on clopidogrel or not, or whether percutaneous coronary intervention was performed. Enoxaparin is an appropriate choice for adjunctive therapy with fibrinolysis in patients with STEMI.

Modern management of acute myocardial infarction

Disruption of intracoronary plaque with thrombus formation provides the pathophysiologic foundation for acute coronary syndromes, which comprise ST-segment myocardial infarction, non-ST-segment myocardial infarction, and unstable angina. Management differs depending on whether ST-segment elevation is present, but the general principles of timely restoration of coronary blood flow and initiation of secondary prevention strategies are applicable to all patients. The purpose of this review is to discuss first the epidemiology, pathophysiology, and diagnosis of acute myocardial infarction. Risk stratification and therapy for patients with ST-segment elevation myocardial infarction and non-ST-segment elevation acute coronary syndromes are then reviewed along with diagnosis and management of the complications of myocardial infarction.

Contemporary management of ST-segment elevation myocardial infarction

Coronary heart disease is the leading cause of death worldwide. In the United States, approximately 1 of every 6 deaths in 2007 was caused by coronary heart disease. Clinical presentation in the acute setting is mostly due to atherosclerotic plaque rupture leading to flow limitation in the affected vessel, and myocardial ischemia and infarction. ST-segment elevation myocardial infarction is usually associated with complete occlusion of the coronary artery and carries the worst prognosis in terms of in-hospital mortality. Despite various advances in treatment options, including percutaneous coronary intervention, ischemic heart disease still carries a significant morbidity and mortality. In this article, we aim to provide a summary of a few key advances in the management of ST-segment elevation myocardial infarction.

Current antithrombotic agents for acute coronary syndromes: focus on bleeding risk

The formation of an intravascular thrombus underlies the clinical symptoms associated with acute coronary syndromes (ACS). Plaque rupture signals the recruitment and activation of platelets, initiation of the coagulation cascade, and generation of thrombin, resulting in the formation of a platelet-rich thrombus. Use of antithrombotic therapy, including antiplatelet and anticoagulant agents, is a crucial element in reducing the overall morbidity and mortality in patients with ACS. Current antiplatelet and anticoagulant therapies act on distinct sites in platelet activation pathways and the coagulation cascade, but because these agents target pathways necessary for protective hemostasis, their use increases the risk for bleeding complications. Previously, bleeding was considered an unavoidable side effect of ACS management with few clinical implications; however, bleeding has since been shown to be an independent predictor of short- and long-term mortality in patients with ACS. Therefore, the prevention of bleeding has become equally as important as the prevention of further ischemic events. Strategies to limit bleeding include bleeding risk stratification, appropriate dosing of antithrombotic drugs, use of the lowest dose of aspirin with proven efficacy, avoidance of combinations of antithrombotic agents unless for a proven indication, use of drugs proven to reduce the risk of bleeding, and choice of radial access over femoral access in case of invasive strategy. In this context, several novel therapeutic approaches are currently under clinical evaluation, including new antiplatelet agents, such as protease-activated receptor 1 antagonists, and new anticoagulants, such as direct-acting antagonists of factor Xa and factor IIa (thrombin). This review discusses antiplatelet and anticoagulant treatment strategies for the management of ACS, with a particular focus on their associated bleeding risks.

Efficacy and Safety of Low-Molecular-Weight Heparins As An Adjunct to Thrombolysis in Acute ST-Elevation Myocardial Infarction

A 48-hour course of intravenous unfractionated heparin (UFH) is the standard of treatment in conjunction with fibrin-specific thrombolysis in ST-elevation myocardial infarction (STEMI). In recent trials, the efficacy and safety of in-hospital administration of subcutaneous low-molecular-weight heparins (LMWH), previously proven effective in non-ST-elevation acute coronary syndromes, have been investigated in the setting of STEMI. The aim of this review was to evaluate the available evidence supporting the use of LMWH in STEMI.

Overall, about 27,000 patients treated with various thrombolytic regimens, were included in 12 open-label randomized clinical trials, where dalteparin, reviparin or enoxaparin were administered. While acknowledging the wide variability in study dimensions, designs and end-points, a higher efficacy of LMWH was observed overall as compared to placebo, and also to UFH (mainly as regards the occurrence of reinfarction). As regards safety, bleedings were more frequent than placebo and comparable to UFH in LMWH groups, with the exception of the pre-hospital ASSENT-3 PLUS trial, where in elderly patients, enoxaparin had an incidence of intracranial hemorrhage twice higher than UFH. In a recent double-blind, randomized, mega-trial including over 20,000 patients, the superior efficacy on in-hospital and 30-day adverse cardiac events (namely reinfarction), and comparable safety on intracranial bleedings, of enoxaparin compared to UFH, was shown.

In conclusion, in-hospital subcutaneous administration of dalteparin, reviparin and enoxaparin, as an adjunct to various thrombolytics in STEMI, appears feasible and at least as effective and safe as 48-hour intravenous treatment with UFH. In accordance with the available strongest evidence, an initial intravenous bolus of enoxaparin followed by twice daily subcutaneous administration for about 1 week should be the preferred regimen, and should be strongly considered instead of intravenous UFH. Along with its easiness of use, not requiring laboratory monitoring, subcutaneous administration of LMWH following STEMI treated with thrombolysis allows extended antithrombotic treatment, while permitting early mobilization (and rehabilitation) of patients.

Effectiveness and safety of combined antiplatelet and anticoagulant therapy: a critical review of the evidence from randomized controlled trials

Antiplatelet and anticoagulant drugs are effective for the prevention of arterial and venous thrombosis but patients continue to experience major cardiovascular events despite their use. Strategies to improve the effectiveness of antithrombotic therapies include selecting the optimal drug and dosing regimen, the use of combinations of antiplatelet and anticoagulant drugs and the development of new more effective drugs to replace existing therapies. Evidence from randomized controlled trials indicates that the combination of aspirin and an anticoagulant is more effective than aspirin alone for the prevention of recurrent cardiovascular events in patients with acute coronary syndrome and is more effective than anticoagulation alone for the prevention of thromboembolic events in patients with mechanical heart valves, but at a cost of increased bleeding. Randomized controlled trials provide no evidence for improved effectiveness of combination therapy compared with antiplatelet therapy alone for the prevention of recurrent cardiovascular events in patients with non-cardioembolic stroke or peripheral artery disease, or compared with anticoagulant therapy alone for the prevention of stroke in patients with atrial fibrillation. Despite lack of evaluation in randomized controlled trials, combination therapy is commonly used in patients with separate indications for antiplatelet therapy (e.g., acute coronary syndrome, recent coronary artery stent) and anticoagulant therapy (e.g., atrial fibrillation with at least one additional risk factor for stroke). Randomized trials are urgently required to evaluate the effectiveness and safety of combining antiplatelet and anticoagulant therapy in these settings.

Systematic review and meta-analysis of the efficacy of appropriate empiric antibiotic therapy for sepsis

Quantifying the benefit of early antibiotic treatment is crucial for decision making and can be assessed only in observational studies. We performed a systematic review of prospective studies reporting the effect of appropriate empirical antibiotic treatment on all-cause mortality among adult inpatients with sepsis. Two reviewers independently extracted data. Risk of bias was assessed using the Newcastle-Ottawa score. We calculated unadjusted odds ratios (ORs) with 95% confidence intervals for each study and extracted adjusted ORs, with variance, methods, and covariates being used for adjustment. ORs were pooled using random-effects meta-analysis. We examined the effects of methodological and clinical confounders on results through subgroup analysis or mixed-effect meta-regression. Seventy studies were included, of which 48 provided an adjusted OR for inappropriate empirical antibiotic treatment. Inappropriate empirical antibiotic treatment was associated with significantly higher mortality in the unadjusted and adjusted comparisons, with considerable heterogeneity occurring in both analyses (I(2) > 70%). Study design, time of mortality assessment, the reporting methods of the multivariable models, and the covariates used for adjustment were significantly associated with effect size. Septic shock was the only clinical variable significantly affecting results (it was associated with higher ORs). Studies adjusting for background conditions and sepsis severity reported a pooled adjusted OR of 1.60 (95% confidence interval = 1.37 to 1.86; 26 studies; number needed to treat to prevent one fatal outcome, 10 patients [95% confidence interval = 8 to 15]; I(2) = 46.3%) given 34% mortality with inappropriate empirical treatment. Appropriate empirical antibiotic treatment is associated with a significant reduction in all-cause mortality. However, the methods used in the observational studies significantly affect the effect size reported. Methods of observational studies assessing the effects of antibiotic treatment should be improved and standardized.

Antithrombotic therapy in patients with coronary artery disease and with type 2 diabetes mellitus

Diabetes mellitus (DM) is a life-threatening disease. Patients with DM have a 2- to 4-fold higher risk of developing cardiovascular disease compared to their non-diabetic counterparts. Several drugs are available for the treatment of stable coronary artery disease (CAD) and acute coronary syndrome (ACS). Among oral antiplatelet agents (acetylsalicylic acid, ticlopidine, clopidogrel, and prasugrel), prasugrel has shown the highest efficacy in patients with DM and ACS. The use of glycoprotein IIb-IIIa receptor inhibitors in diabetic subjects with ACS undergoing percutaneous coronary intervention (PCI) reduces adverse clinical events in a greater extent than in non-diabetics. Several direct and indirect antithrombins are recommended for the treatment of ACS such as unfractionated heparin (UFH), enoxaparin, fondaparinux, and bivalirudin. Enoxaparin and bivalirudin have been shown to be superior to UFH among patients with ST-elevation MI (STEMI) and non-ST elevation MI (NSTEMI) also in diabetic subgroup analyses.

Antithrombotic drugs in coronary artery disease: risk benefit ratio and bleeding

The antithrombotic treatment of coronary artery disease is becoming increasingly complex. Aspirin is often combined with more potent antiplatelet agents such as thienopyridines and glycoprotein IIb/IIIa inhibitors. The classic anticoagulant unfractionated heparin is giving way to low-molecular-weight heparin, the pentasaccharide fondaparinux and the direct thrombin inhibitor bivalirudin. Warfarin (or another vitamin K antagonist) and antiplatelet agents are often required in combination for several months. Patients and physicians who have experienced major bleeding complications sometimes question the benefit of these treatment strategies. It is therefore crucial to try and weigh the impact on efficacy against safety. In this review the net benefit is discussed both numerically, comparing absolute reductions vs. increases in risks, and also by addressing the qualitative importance of each component in reaching the net benefit. Except for primary prophylaxis in patients at low-moderate risk for coronary events, there is a net benefit of antithrombotic therapy. With increasing severity of the coronary condition the net benefit generally prevails even with an increasing number of antithrombotic drugs combined. However, as the patient slowly stabilizes after appropriate interventions, it is necessary to de-escalate the treatment in accordance with decreasing net benefit of prolonged combination therapy.

Enoxaparin is a cost-effective adjunct to fibrinolytic therapy for ST-elevation myocardial infarction in contemporary practice

INTRODUCTION

In patients receiving fibrinolytic therapy for ST-elevation myocardial infarction (STEMI), adjunct treatment with enoxaparin has been shown to provide superior net clinical benefit compared with unfractionated heparin (UFH) in the Enoxaparin and Thrombolysis Reperfusion for Acute Myocardial Infarction Treatment - Thrombolysis in Myocardial Infarction (ExTRACT-TIMI) 25 study. The objective of this study was to compare the cost effectiveness of enoxaparin and UFH strategies.

METHODS

A cost-utility analysis was conducted using a two-stage model: (1) A 30-day decision tree analytical model for the acute treatment phase, and (2) a lifetime Markov model (from 30 days post-STEMI until death) populated using patient survival data.

RESULTS

Assuming treatment continuation for 7 days, the mean day 1-30 incremental cost associated with enoxaparin was pound 49 per patient, and mean lifetime incremental cost was pound 592 per patient ( pound 91,091 vs. pound 90,499, respectively). Given an additional 0.048 life years gained per patient with enoxaparin, the cost per life year saved was pound 12,353, and given an additional 0.038 quality-adjusted life years (QALY) per patient with enoxaparin, the cost per QALY was pound 15,413. In an alternative scenario, reflecting contemporary practice assuming early treatment discontinuation at 48 hours, for example following urgent revascularization, the incremental cost per QALY was pound 13,556.

CONCLUSION

The use of an enoxaparin versus UFH strategy in patients receiving fibrinolytic therapy for STEMI, whether continued for 7 days or discontinued early, for example following urgent revascularization, is cost effective at a pound 20,000 willingness-to-pay threshold.

Adjunctive low molecular weight heparin during fibrinolytic therapy in acute ST-segment elevation myocardial infarction: a meta-analysis of randomized control trials

BACKGROUND

Recent data suggests that low molecular weight heparins (LMWHs) may be superior to unfractionated heparin (UFH) as an adjunct to fibrinolytic therapy in patients with acute ST-segment elevation myocardial infarction (STEMI).

HYPOTHESIS

We evaluated cardiac outcomes and the risk of major bleeding with LMWHs vs UFH in the management of STEMI.

METHODS

Seven randomized trials of patients with acute STEMI treated with fibrinolytic therapy and adjunctive LMWHs through the index hospitalization or weight-based UFH for at least 48 hours were identified. We analyzed both primary endpoints (death and nonfatal recurrent myocardial infarction through 30 days), and secondary endpoints (death, recurrent myocardial infarction, and major bleeding during index hospitalization at 7 days). Outcomes were computed using the Mantel-Haenszel fixed-effect model. A 2-sided alpha error of < 0.05 was considered significant.

RESULTS

Compared to UFH, LMWH significantly reduced reinfarction (p < 0.001) during hospitalization at 7 days and the effect remained consistent at 30 d (p < 0.001). When analyzed for mortality at 7 days and 30 days follow-up, there were no statistically significant differences observed between the 2 groups. Additionally the LMWH group had higher risk of major bleeding (p < 0.001).

CONCLUSIONS

The present meta-analysis suggests in patients receiving fibrinolytic therapy for STEMI, LMWHs as an adjunctive therapy is superior to UFH in reducing reinfarction during hospitalization at 7 days and at 30 days. The mortality was not significant between the 2 groups during hospitalization at 7 days and at 30 days. However, UFH is superior to LMWHs in the reduction of major bleeding at 7 days index hospitalization.

Fondaparinux in acute coronary syndromes

Antithrombotic therapies form the cornerstone of management of acute coronary syndromes (ACS). An ideal antithrombotic agent should reduce ischemic complications while keeping bleeding events to a minimum. Heparins, both unfractionated and low molecular weight, reduce ischemic outcomes but also significantly increase the risk of major and minor bleeding. Moreover, they do not reduce mortality. Therefore, there is a need for newer agents that preserve the benefits of ischemia reduction while decreasing mortality and bleeding risk. Fondaparinux is a synthetic pentasaccharide which specifically targets factor Xa of the coagulation cascade. It has been effectively used in the prevention of and treatment of venous thromboembolic disease. Two large randomized controlled trials of fondaparinux compared to unfractionated and low molecular weight heparins, among patients with ACS have recently been completed. These studies have shown a significantly lower risk of bleeding with fondaparinux compared to heparins, with equivalent or greater reductions in ischemic outcomes. A small but definite increase in the risk of catheter-related thrombosis has been found among patients undergoing coronary interventions, which is ameliorated by the administration of unfractionated heparin. This review outlines the pharmacological properties of fondaparinux and critically examines the available clinical trial data for fondaparinux in ACS.

Acute coronary syndromes: Diagnosis and management, part II

At the most severe end of the spectrum of acute coronary syndromes is ST-segment elevation myocardial infarction (STEMI), which usually occurs when a fibrin-rich thrombus completely occludes an epicardial coronary artery. The diagnosis of STEMI is based on clinical characteristics and persistent ST-segment elevation as demonstrated by 12-lead electrocardiography. Patients with STEMI should undergo rapid assessment for reperfusion therapy, and a reperfusion strategy should be implemented promptly after the patient's contact with the health care system. Two methods are currently available for establishing timely coronary reperfusion: primary percutaneous coronary intervention and fibrinolytic therapy. Percutaneous coronary intervention is the preferred method but is not always available. Antiplatelet agents and anticoagulants are critical adjuncts to reperfusion. This article summarizes the current evidence-based guidelines for the diagnosis and management of STEMI. This summary is followed by a brief discussion of the role of noninvasive stress testing in the assessment of patients with acute coronary syndrome and their selection for coronary revascularization.

Pharmacological and clinical profile of bivalirudin in the treatment of patients with acute coronary syndrome

BACKGROUND

Bivalirudin is a direct thrombin inhibitor with several pharmacological advantages over heparin. It has been studied extensively in non-ST elevation acute 60 coronary syndromes (NSTE-ACS) and in percutaneous coronary intervention. Bivalirudin has also recently been investigated in patients with ST-elevation myocardial infarction (STEMI) treated with primary angioplasty and stenting. More than 27,000 patients were randomized in these trials.

OBJECTIVE

To provide an overview of the pharmacological properties of bivalirudin and its efficacy and safety profile in patients across the spectrum of acute coronary syndromes (ACS).

METHODS

All published, peer-reviewed clinical trials were reviewed and as relevant were included.

RESULTS AND CONCLUSIONS

Bivalirudin with provisional IIb/IIIa antagonists provides consistent results across the full spectrum of ACS, with similar or non-inferior protection from ischemic events and significantly reduces bleeding complications compared with heparin and IIb/IIIa antagonists. In STEMI, mortality at 30 days and 1 year is significantly reduced. The unique pharmacokinetic profile of bivalirudin allows for simultaneous reductions in both ischemic and hemorrhagic events and makes it an appropriate alternative to heparin.

Enoxaparin in patients with primary percutaneous coronary intervention for acute ST segment elevation myocardial infarction

The inhibition of thrombin plays a key role as adjunct therapy in the management of patients with primary percutaneous coronary intervention for ST elevation myocardial infarction. Enoxaparin provides a more predictable and constant level of anticoagulation compared with the current standard unfractionated heparin. The available data from smaller studies and prospective registries suggest that enoxaparin is associated with a reduction in the rate of death and nonfatal reinfarction after primary percutaneous coronary intervention without an increase in bleeding complications. Thus, a large randomized trial is warranted to further evaluate the role of enoxaparin in these patients.

Anticoagulants in coronary artery disease

Anticoagulant therapy for acute coronary syndromes is becoming more complex as newer agents are added to unfractionated heparin and warfarin. The anticoagulants used in current clinical practice are low molecular weight heparins, direct thrombin inhibitors, and heparinoids. Properties of and recent clinical trial data regarding these newer anticoagulants are reviewed in reference to current American College of Cardiology/American Heart Association guidelines.

Antithrombotic Therapy With Fondaparinux in Relation to Interventional Management Strategy in Patients With ST- and Non–ST-Segment Elevation Acute Coronary Syndromes

Background— The Fifth and Sixth Organization to Assess Strategies in Ischemic Syndromes (OASIS 5 and 6) trials evaluated fondaparinux, a synthetic factor Xa inhibitor, in patients with non–ST- and ST-segment elevation acute coronary syndromes, respectively. Combined results for these 2 trials on major efficacy and safety outcomes and data on the effects of fondaparinux in relation to interventional management strategy have not been previously reported.

Methods and Results— We performed an individual patient–level combined analysis of 26 512 patients from the OASIS 5 and 6 trials who were randomized in a double-blind fashion to fondaparinux 2.5 mg daily or a heparin-based strategy (dose-adjusted unfractionated heparin or enoxaparin). Results were stratified according to whether an early invasive, a delayed invasive, or an initial conservative management strategy was performed. Fondaparinux was superior to heparin in reducing the composite of death, myocardial infarction, or stroke (8.0% versus 7.2%; hazard ratio [HR], 0.91; P =0.03) and death alone (4.3% versus 3.8%; HR, 0.89; P =0.05). Fondaparinux reduced major bleeding by 41% (3.4% versus 2.1%; HR, 0.59; P <0.00001) and had a more favorable net clinical outcome than heparin (11.1% versus 9.3%; HR, 0.83; P <0.0001). In 19 085 patients treated with an invasive strategy, fondaparinux suppressed ischemic events to an extent similar to heparin and reduced major bleeding by more than one-half, resulting in a superior net clinical outcome (10.8% versus 9.4%; HR, 0.87; P =0.008). A similar benefit also was observed in those treated with a conservative strategy (HR, 0.74; 95% confidence interval, 0.64 to 0.85; P <0.001).

Conclusion— Compared with a heparin-based strategy, fondaparinux reduced mortality, ischemic events, and major bleeding across the full spectrum of acute coronary syndromes and was associated with a more favorable net clinical outcome in patients undergoing either an invasive or a conservative management strategy.

Clopidogrel use and bleeding after coronary artery bypass graft surgery

BACKGROUND

Short-term use of clopidogrel plus aspirin among patients with acute coronary syndrome reduces ischemic events, but concerns about coronary artery bypass graft (CABG) surgery-related bleeding limit its early use.

METHODS

Using data from 4,794 consecutive CABG procedures in the Duke Databank for Cardiovascular Disease (January 1999 to December 2003), we developed multivariable models for associations with CABG-related bleeding defined as reoperation for bleeding, red cell transfusion, and a composite of reoperation/transfusion/hematocrit drop>or=15%. We examined clopidogrel use<or=5 days versus no clopidogrel<or=5 days before CABG in each model. Models were adjusted for propensity for clopidogrel use<or=5 days.

RESULTS

Of 4,794 CABG patients, 332 (6.9%) received clopidogrel<or=5 days before CABG, 127 (2.6%) had reoperation for bleeding, 3,277 (68.4%) received red cell transfusion, and 4,387 (91.5%) had the composite outcome. After adjustment, clopidogrel use<or=5 days was not significantly associated with reoperation (odds ratio [OR] 1.24, 95% CI 0.63-2.41) or the composite end point (OR 1.23, 95% CI 0.72-2.10). Clopidogrel<or=5 days was modestly associated with red cell transfusion (OR 1.40, 95% CI 1.04-1.89) but more weakly than other factors, including which surgeon performed the procedure.

CONCLUSION

Clopidogrel administration<or=5 days before CABG was not significantly associated with reoperation for bleeding or a bleeding composite, and only weakly with red cell transfusion after surgery. The impact of withholding clopidogrel acutely in those for whom clopidogrel has proven benefits and the impact of delaying CABG to prevent bleeding among patients treated with clopidogrel should be viewed in the context of other stronger determinants of bleeding.

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.

Venous thromboembolism, thrombophilia, antithrombotic therapy, and pregnancy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article discusses the management of venous thromboembolism (VTE) and thrombophilia, as well as the use of antithrombotic agents, during pregnancy and is part of the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that benefits do, or do not, outweigh risks, burden, and costs. Grade 2 recommendations are weaker and imply that the magnitude of the benefits and risks, burden, and costs are less certain. Support for recommendations may come from high-quality, moderate-quality or low-quality studies; labeled, respectively, A, B, and C. Among the key recommendations in this chapter are the following: for pregnant women, in general, we recommend that vitamin K antagonists should be substituted with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1A], except perhaps in women with mechanical heart valves. For pregnant patients, we suggest LMWH over UFH for the prevention and treatment of VTE (Grade 2C). For pregnant women with acute VTE, we recommend that subcutaneous LMWH or UFH should be continued throughout pregnancy (Grade 1B) and suggest that anticoagulants should be continued for at least 6 weeks postpartum (for a total minimum duration of therapy of 6 months) [Grade 2C]. For pregnant patients with a single prior episode of VTE associated with a transient risk factor that is no longer present and no thrombophilia, we recommend clinical surveillance antepartum and anticoagulant prophylaxis postpartum (Grade 1C). For other pregnant women with a history of a single prior episode of VTE who are not receiving long-term anticoagulant therapy, we recommend one of the following, rather than routine care or full-dose anticoagulation: antepartum prophylactic LMWH/UFH or intermediate-dose LMWH/UFH or clinical surveillance throughout pregnancy plus postpartum anticoagulants (Grade 1C). For such patients with a higher risk thrombophilia, in addition to postpartum prophylaxis, we suggest antepartum prophylactic or intermediate-dose LMWH or prophylactic or intermediate-dose UFH, rather than clinical surveillance (Grade 2C). We suggest that pregnant women with multiple episodes of VTE who are not receiving long-term anticoagulants receive antepartum prophylactic, intermediate-dose, or adjusted-dose LMWH or intermediate or adjusted-dose UFH, followed by postpartum anticoagulants (Grade 2C). For those pregnant women with prior VTE who are receiving long-term anticoagulants, we recommend LMWH or UFH throughout pregnancy (either adjusted-dose LMWH or UFH, 75% of adjusted-dose LMWH, or intermediate-dose LMWH) followed by resumption of long-term anticoagulants postpartum (Grade 1C). We suggest both antepartum and postpartum prophylaxis for pregnant women with no prior history of VTE but antithrombin deficiency (Grade 2C). For all other pregnant women with thrombophilia but no prior VTE, we suggest antepartum clinical surveillance or prophylactic LMWH or UFH, plus postpartum anticoagulants, rather than routine care (Grade 2C). For women with recurrent early pregnancy loss or unexplained late pregnancy loss, we recommend screening for antiphospholipid antibodies (APLAs) [Grade 1A]. For women with these pregnancy complications who test positive for APLAs and have no history of venous or arterial thrombosis, we recommend antepartum administration of prophylactic or intermediate-dose UFH or prophylactic LMWH combined with aspirin (Grade 1B). We recommend that the decision about anticoagulant management during pregnancy for pregnant women with mechanical heart valves include an assessment of additional risk factors for thromboembolism including valve type, position, and history of thromboembolism (Grade 1C). While patient values and preferences are important for all decisions regarding antithrombotic therapy in pregnancy, this is particularly so for women with mechanical heart valves. For these women, we recommend either adjusted-dose bid LMWH throughout pregnancy (Grade 1C), adjusted-dose UFH throughout pregnancy (Grade 1C), or one of these two regimens until the thirteenth week with warfarin substitution until close to delivery before restarting LMWH or UFH) [Grade 1C]. However, if a pregnant woman with a mechanical heart valve is judged to be at very high risk of thromboembolism and there are concerns about the efficacy and safety of LMWH or UFH as dosed above, we suggest vitamin K antagonists throughout pregnancy with replacement by UFH or LMWH close to delivery, after a thorough discussion of the potential risks and benefits of this approach (Grade 2C).

New anticoagulant strategies in ST elevation myocardial infarction: trials and clinical implications

New data have re-established the importance of anticoagulation of patients with ST segment elevation myocardial infarction (STEMI), both as an adjuvant to reperfusion therapy or in patients ineligible for reperfusion. Recent randomized trials have found newer agents to be superior to conventional unfractionated heparin. This article summarizes current understanding of the underlying pathophysiology of STEMI and provides a comprehensive review of emerging trial data for low molecular weight heparins, anti-factor Xa agents and direct thrombin inhibitors in this setting.

Avoiding and Managing Bleeding Complications in Patients with Non-ST-Segment Elevation Acute Coronary Syndromes

Antithrombotic therapy coupled with early use of cardiac catheterization and revascularization have decreased morbidity and mortality rates in patients who have acute ischemic heart disease but who carry a risk for bleeding. Bleeding complications in patients with acute coronary syndromes are associated with worse clinical outcomes, including recurrent ischemic events and death. Determining the appropriate balance between preventing ischemic events and causing bleeding in patients with acute coronary syndromes present a challenging problem for clinicians. Antithrombotics studied in recent clinical trials that have focused on bleeding reduction include bivalirudin and fondaparinux. In this review, the incidence, predictors, and clinical outcomes associated with bleeding are discussed. Furthermore, the association between antithrombotic agents and bleeding and propose strategies to prevent bleeding complications are also discussed.

Reperfusion strategies in ST-elevation myocardial infarction--current status and perspectives for early and pre-hospital treatment

The latest guidelines on the emergency care of acute ST-elevation myocardial infarction were published by the European Resuscitation Council at the end of 2005. Since then, numerous studies have been presented, which have led to important conclusions. Among pharmacological interventions, the opinion on adjuncts to anticoagulant treatment in the area of thrombolysis as well as in primary coronary intervention seems to be moving away from unfractionated heparin towards low molecular weight heparin, and possibly even factor Xa-specific pentasaccharide or the direct antithrombin bivalirudin. Clopidogrel has developed to become an accepted standard alongside aspirin in thrombolytic therapy of ST-elevation myocardial infarction, even if some questions still remain open. The promising idea of "facilitated percutaneous coronary intervention" has shown itself to at least be problematic if performed immediately and routinely after thrombolysis; "rescue" intervention in the event of ineffective thrombolysis is, on the other hand, useful and effective. Apparently, a more individualistic approach is required, which combines new therapeutic options and patients' conditions on the one side with regional resources on the other, to produce an optimal and timely strategy, remembering that one size does not fit all.

Use of anticoagulants in ST-segment elevation myocardial infarction patients; a focus on low-molecular-weight heparin

INTRODUCTION

Primary percutaneous coronary intervention (PCI) is the treatment of choice for patients with ST-segment elevation myocardial infarction (STEMI), but given logistics, many patients are still managed with thrombolytics. Unfractionated heparin (UFH) is recommended for routine use in STEMI patients treated with thrombolytics. However, other anticoagulants have been evaluated for use in STEMI patients treated with thrombolysis, including the low-molecular-weight heparins (LMWHs, enoxaparin, dalteparin, and reviparin), fondaparinux and bivalirudin.

METHODS AND RESULTS

A review of the available randomized controlled study data shows that most evidence, in terms of number of trials and number of patients treated with anticoagulants in STEMI has accumulated for LMWHs. The use of enoxaparin and reviparin improves hard clinical efficacy endpoints although there is an excess of bleeding events. Trials with dalteparin have failed to demonstrate improvement in hard clinical efficacy endpoints compared with UFH.

SUMMARY

Enoxaparin is currently the only LMWH with FDA approval for use in STEMI patients and should be considered as a preferable alternative to UFH in STEMI patients treated with fibrinolysis.