Thrombin-specific anticoagulation with bivalirudin versus heparin in patients receiving fibrinolytic therapy for acute myocardial infarction: the HERO-2 randomised trial

New trials and therapies for acute myocardial infarction

Acute coronary syndromes (ACSs), which include the clinical entities of unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI), account for more than 1.5 million hospital admissions annually in the United States alone. Approximately 1 million of these admissions are classified as UA/NSTEMI and approximately 500,000 are STEMI. Because of the overwhelming number of studies on ACSs over the past several years, this article focuses on new trials and therapies for treating patients diagnosed with STEMI.

Thrombolysis in acute myocardial infarction: current status

ST-segment elevation myocardial infarction (STEMI) is still a major public health problem in the modern world. Therapeutic options have changed much over the last 20 years, with a shift in favor of mechanical reperfusion over pharmacologic reperfusion. Thrombolytic therapy still has much to offer in the management of STEMI, however, because many patients do not have timely access to a facility with the required expertise for establishing mechanical reperfusion. This review highlights the history of thrombolytic therapy, adjunctive therapies, the relationship with mechanical reperfusion, and potential roles for thrombolysis in the future.

Managing acute coronary syndrome: Evidence-based approaches

PURPOSE

To describe data and insights from a national quality improvement initiative known as Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology (ACC)/American Heart Association (AHA) Guidelines (CRUSADE), for managing non-ST-segment elevation acute coronary syndrome (ACS), as well as the findings and implications of Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY), a study of bivalirudin with or without a glycoprotein (GP) IIb/IIIa inhibitor in patients with non-ST-segment elevation ACS who were undergoing an invasive intervention, and the results of two recent studies of clopidogrel in patients with ST-segment elevation myocardial infarction (MI) that are not reflected in current ACC/AHA guidelines for managing ST-segment elevation MI.

SUMMARY

Data from the CRUSADE registry suggest that there is room for improvement in the use of GP IIb/IIIa inhibitors and clopidogrel during the first 24 hours of hospitalization in patients with non-ST-segment elevation ACS who undergo early invasive cardiac procedures, and in the prescribing of angiotensin converting-enzyme (ACE) inhibitors at the time of discharge. Adherence to ACC/AHA guidelines for non-ST-segment elevation ACS has improved over time but further improvement is needed. Failure to reduce the dose of a GP IIb/IIIa for patients with renal insufficiency resulting in excessive dosing of GP IIb/IIIa inhibitors increases the risk of major bleeding and is particularly common among the elderly, women, and patients with renal insufficiency. The ACUITY study suggests that bivalirudin plus a GP IIb/IIIa inhibitor is a suitable alternative to standard therapy for moderate- to high-risk patients with non-ST-segment elevation ACS who are undergoing early invasive intervention, and bivalirudin alone may be preferred because of a lower risk of major bleeding. However, interpretation of the ACUITY results is complicated by numerous methodologic concerns, so the role of bivalirudin in managing non-ST-segment elevation ACS is still evolving. In patients with ST-segment elevation, clopidogrel provides an early benefit in reopening occluded coronary arteries and a late benefit in reducing cardiovascular mortality and morbidity without increasing the risk of bleeding. Clopidogrel treatment is warranted before as well as after percutaneous coronary intervention in patients with ST-segment elevation MI who receive fibrinolytic therapy. Adding clopidogrel to fibrinolytic therapy and other standard therapy reduces mortality without increasing the risk of bleeding.

CONCLUSION

Evidence-based guidelines provide recommendations for the management of ACS, but the pace of clinical research is rapid and current guidelines do not reflect the latest research findings. Pharmacists need to stay abreast of new developments and ensure that clinical practice reflects these developments.

Acute Coronary Care in the Elderly, Part II

Background— Age is an important determinant of outcomes for patients with acute coronary syndromes. However, community practice reveals a disproportionately lower use of cardiovascular medications and invasive treatment even among elderly patients who would stand to benefit. Limited trial data are available to guide care of older adults, which results in uncertainty about benefits and risks, particularly with newer medications or invasive treatments and in the setting of advanced age and complex health status.

Methods and Results— Part II of this American Heart Association scientific statement summarizes evidence on presentation and treatment of ST-segment–elevation myocardial infarction in relation to age (<65, 65 to 74, 75 to 84, and ≥85 years). The purpose of this statement is to identify areas in which the evidence is sufficient to guide practice in the elderly and to highlight areas that warrant further study. Treatment-related benefits should rise in an elderly population, yet data to confirm these benefits are limited, and the heterogeneity of older populations increases treatment-associated risks. Elderly patients with ST-segment–elevation myocardial infarction more often have relative and absolute contraindications to reperfusion, so eligibility for reperfusion declines with age, and yet elderly patients are less likely to receive reperfusion even if eligible. Data support a benefit from reperfusion in elderly subgroups up to age 85 years. The selection of reperfusion strategy is determined more by availability, time from presentation, shock, and comorbidity than by age. Additional data are needed on selection and dosing of adjunctive therapies and on complications in the elderly. A “one-size-fits-all” approach to care in the oldest old is not feasible, and ethical issues will remain even in the presence of adequate evidence. Nevertheless, if the contributors to treatment benefits and risks are understood, guideline-recommended care may be applied in a patient-centered manner in the oldest subset of patients.

Conclusions— Few trials have adequately described treatment effects in older patients with ST-segment–elevation myocardial infarction. In the future, absolute and relative risks for efficacy and safety in age subgroups should be reported, and trials should make efforts to enroll the elderly in proportion to their prevalence among the treated population. Outcomes of particular relevance to the older adult, such as quality of life, physical function, and independence, should also be evaluated, and geriatric conditions unique to this age group, such as frailty and cognitive impairment, should be considered for their influence on care and outcomes. With these efforts, treatment risks can be minimized, and benefits can be placed within the health context of the elderly patient.

Bivalirudin in percutaneous coronary intervention

Bivalirudin is a member of the direct thrombin inhibitor group of anticoagulants. It has been evaluated as an alternative to unfractionated and low-molecular-weight heparins in the settings of percutaneous coronary intervention (PCI) and acute coronary syndrome (ACS). Results of clinical trials to date suggest bivalirudin is a viable alternative to the use of a heparin combined with a glycoprotein (GP) IIb/IIIa inhibitor in these settings. Thrombin has a central role in coagulation and platelet activation in ACS and during PCI. Its direct inhibition is an attractive target for therapy in these settings. Bivalirudin is a 20 amino acid polypeptide hirudin analog. It displays bivalent and reversible binding to the thrombin molecule, inhibiting its action. Direct inhibition of thrombin with bivalirudin has theoretical pharmacokinetic and pharmacodynamic advantages over the indirect anticoagulants. A reduction in rates of bleeding without loss of anti-thrombotic efficacy has been a consistent finding across multiple clinical trials. There may be economic benefits to the use of bivalirudin if it permits a lower rate of use of the GP IIb/IIIa inhibitors. This article reviews the pharmacology of bivalirudin and clinical trial evidence to date. There are now data from multiple clinical trials and meta-analyses in the setting of ACS and PCI. Early results from the acute catheterization and urgent intervention strategy (ACUITY) trial are discussed.

Fondaparinux in the management of patients with ST-elevation acute myocardial infarction

The death rate of patients with ST-segment elevation myocardial infarction (STEMI) remains substantial. Fondaparinux is a synthetic selective Factor Xa inhibitor with a high efficacy and good safety, in terms of bleeding risk, in the prevention and treatment of venous thromboembolism, and in the treatment of non-ST elevation acute coronary syndromes (OASIS-5). The OASIS-6 trial was a randomized, double-blind trial comparing fondaparinux 2.5 mg once daily with standard therapy, either placebo or unfractionated heparin according to the indication, in 12092 patients with STEMI. At day 30, fondaparinux significantly reduced the occurrence of the primary efficacy outcome (death or recurrent myocardial infarction) by 14% (p=0.008). Consistent reductions in both death and recurrent MI were observed at 6-month follow-up. The benefits were significant in patients who received no reperfusion therapy or a thrombolytic agent, but not in patients undergoing primary percutaneous coronary interventions. There was a trend (p=0.13) towards fewer severe bleeds in the fondaparinux group (1.0% vs 1.3% in the control group). In conclusion, fondaparinux significantly reduced mortality without increasing severe bleeding in patients with STEMI. Overall, the data from the OASIS studies showed that fondaparinux 2.5 mg may represent a new anticoagulant standard in patients with acute coronary syndromes.

Evidence-based medical therapy of patients with acute coronary syndromes

Acute coronary syndromes (ACS) present a major health challenge in modern medicine. With new clinical trials being conducted, our knowledge of latest therapies for ACS continually evolves. In this article, we review currently available medical therapies and provide evidence-based rationale for current pharmacologic therapies. Among the antiplatelet therapies, aspirin, clopidogrel, and glycoprotein IIb/IIIa inhibitors demonstrate significant efficacy in reducing morbidity and mortality. Among the anticoagulants, unfractionated heparin and low molecular weight heparin, particularly enoxaparin sodium, remain the hallmarks of therapy against which newer anticoagulants are often compared. Bivalirudin has recently showed significant efficacy in decreasing cardiovascular events and mortality, but with potentially less risk of bleeding than heparin. Results of trials evaluating warfarin remain inconsistent regarding potential benefits. Finally, fondaparinux sodium, recently tested, shows promise as a powerful yet safe anticoagulant. Fibrinolysis is an acceptable modality for reperfusion if facilities equipped for primary percutaneous revascularization are not available. Regarding anti-ischemic therapy, beta-adrenoceptor antagonists and nitrates remain critical in the early management of ACS. Inhibitors of the renin-angiotensin-aldosterone system have also shown significant reductions in the morbidity and mortality of patients presenting with ACS, particularly in patients with left ventricular dysfunction and clinical heart failure, with ACE inhibitors being first-line agents and angiotensin receptor antagonists being a reasonable substitute if ACE inhibitors are not tolerated. Among the lipid-lowering therapies, statins (HMG-CoA reductase inhibitors) have been documented as being the most well tolerated and most efficacious therapies for ACS patients and data exist that they should be administered early in ACS management. Studies evaluating combination therapy (antiplatelet drugs, beta-adrenoceptor antagonists, ACE inhibitors, and lipid-lowering agents) show a clear benefit in mortality in patients with known coronary artery disease. Efforts to improve these key evidence-based medical therapies are numerous and include such programs as the American College of Cardiology's Guidelines Applied in Practice, international patient registries such as the Global Registry of Acute Coronary Events, and studies such as CRUSADE. Finally, patients with diabetes mellitus pose a challenge to clinicians both in terms of their glycemic control and in their apparent relative resistance to antiplatelet therapy. Studies involving ACS patients suggest that stringent glycemic control may result in benefits in both morbidity and mortality.

Direct antithrombins: mechanisms, trials, and role in contemporary interventional medicine

Direct thrombin inhibitors have several potential advantages over indirect thrombin inhibitors such as heparin. Bivalirudin, a bivalent direct thrombin inhibitor, is most commonly used in clinical practice and has a proven role in contemporary interventional medicine with elective percutaneous coronary intervention (PCI) as well as in patients with non-ST-elevation acute coronary syndrome (NSTEACS). Results from well-controlled clinical trials have shown that bivalirudin is associated with an approximate 50% reduction in major bleeding while having similar effects on incidence of death and myocardial infarction (MI) compared with herapin or enoxaparin and glycoprotein IIb/IIIa inhibitors. Bivalirudin has been successfully used in off- and on-pump cardiac surgery. Argatroban is the most evaluated among the univalent direct thrombin inhibitors inhibiting only the catalytic site of thrombin. It has been associated with similar rates of major bleeding compared with heparin in patients with acute MI receiving either streptokinase or alteplase with no effects on clinical endpoints. In a meta-analysis of 11 randomised trials where direct thrombin inhibitors (hirudin, bivalirudin, argatroban, efegatan or inogatran) were compared with unfractionated heparin in >35,000 patients with ST-elevation MI (STEMI) or NSTEACS there was no mortality difference between treatment groups but the incidence of MI at 30 days was significantly reduced in patients treated with direct thrombin inhibitors compared with heparin (4.7% vs 5.3%; p < 0.004). The role of direct thrombin inhibitors in both primary angioplasty for STEMI and angioplasty after fibrinolytic therapy needs to be established. Overall, the efficacy and improved safety profile make bivalirudin an attractive first-line anticoagulant for elective PCI and in patients with NSTEACS undergoing an invasive strategy.

[Acute myocardial infarction: what is new?]

Current recommendations on the management of acute myocardial infarction and the use of thrombolysis are reviewed.

Risk Stratification of Patients With Acute Anterior Myocardial Infarction and Right Bundle-Branch Block

BACKGROUND

Patients with an acute anterior ST-segment elevation myocardial infarction and right bundle-branch block (RBBB) have a high mortality risk, which may be stratified by early ECG changes.

METHODS AND RESULTS

In the Hirulog Early Reperfusion Occlusion (HERO-2) trial, 17 073 patients with acute myocardial infarction (AMI) within 6 hours of symptom onset were treated with streptokinase and randomized to receive bivalirudin or heparin. There was no difference in the primary end point of 30-day mortality. ECGs were recorded at randomization and 60 minutes after fibrinolytic therapy was begun. The 30-day mortality rate was 31.6% in the 415 patients with RBBB and anterior AMI at randomization and 33% in the 100 patients who developed new RBBB at 60 minutes from normal baseline conduction accompanying an anterior AMI. An increase in QRS duration by 20-ms increments was associated with increasing 30-day mortality rate in both RBBB groups on multivariable analyses with covariates of age, Killip class, systolic blood pressure, pulse, and prior infarction. Patients with QRS duration > or = 160 ms had higher 30-day mortality rate than those with QRS duration < 160 ms (37.2% versus 27.2%, P = 0.03, and 46.2% versus 24.5%, P = 0.025, in the 2 groups, respectively). For the patients with RBBB and anterior MI at randomization, RBBB resolved at 60 minutes in 40 patients, but 30-day mortality rate was unchanged. For those with persisting RBBB at 60 minutes, 30-day mortality rate was lower if ST-segment elevation had resolved by > or = 50% (20.4% versus 35.3%, P = 0.006).

CONCLUSIONS

In patients with anterior AMI and RBBB, increasing QRS duration is associated with increasing 30-day mortality. Early ST-segment resolution after fibrinolytic therapy despite persisting RBBB is associated with lower mortality rate.

Initial Q waves accompanying ST-segment elevation at presentation of acute myocardial infarction and 30-day mortality in patients given streptokinase therapy: an analysis from HERO-2

BACKGROUND

The presence of pathological Q waves in the infarct leads on the surface electrocardiogram in an ST-elevation acute myocardial infarction indicates myocardial necrosis. Clinically it might be difficult to ascertain the onset of acute myocardial infarction. Our aim was to assess whether the presence or absence of Q waves at presentation could be used as an indicator of the duration of acute myocardial infarction and predict mortality.

METHODS

15,222 patients with ST-elevation acute myocardial infarction and normal intraventricular conduction were randomly assigned streptokinase and aspirin plus bivalirudin or unfractionated heparin in the HERO-2 trial; randomisation did not alter 30-day mortality. 10,244 patients (67%) had Q waves in the infarct territory at the time of randomisation, and 4978 (33%) did not. The primary endpoint was 30-day mortality.

FINDINGS

There were more deaths at 30 days in patients with initial Q waves than in those without (1044 [10%] vs 344 [7%], p<0.0001). These findings were similar in patients with a first acute myocardial infarction and when stratified by time to randomisation (0-2, >2-4, >4 h) and by acute myocardial infarction location (anterior or inferior). Both the presence of initial Q waves and time to randomisation were positive univariate predictors, but only the presence of initial Q waves independently predicted 30-day mortality on multivariate analysis (adjusted OR 1.44, 95% CI 1.25-1.65 with clinical indices, and 1.31, 1.12-1.54 with clinical plus ST indices included as predictors).

INTERPRETATION

The presence of Q waves in the infarct leads at presentation of ST-elevation acute myocardial infarction independently predicts higher 30-day mortality in patients treated with fibrinolytic therapy. Therefore, a more aggressive approach to reperfusion might be warranted in these patients.

Poor outcomes after fibrinolytic therapy for ST-segment elevation myocardial infarction: impact of age (a meta-analysis of a decade of trials)

BACKGROUND

Fibrinolysis for ST-segment elevation myocardial infarction (STEMI) reduces mortality, but its relative efficacy and risks are age-dependent. We aimed to quantify the outcomes of fibrinolysis and adjunctive antithrombin therapy for STEMI stratified by age.

METHODS

We performed a meta-analysis of 11 published (1992-2001) randomized clinical trials of fibrinolysis in STEMI (sample size >or=3,000, no age limit, no placebo-controlled arms) identified by MEDLINE through June 2005. Event rates and odds ratios (OR) in elderly vs. younger patients were calculated for mortality, intracranial hemorrhage (ICH) and total stroke (CVA). Elderly patients were defined as >or=75 years (GUSTO I, TIMI 9B, GUSTO III, COBALT, ASSENT-2, InTIME-II TIMI-17, ASSENT-3, GUSTO V, and HERO-2), except when defined as >65 or >or=70 years by the study (INJECT and ISIS-3).

RESULTS

Elderly (n = 24,531) vs. younger (n = 123,568) patients had increased rates of mortality (19.7% vs. 5.5%), ICH (1.4% vs. 0.5%) and CVA (3.5 vs. 1.2%) by 30-35 days; the excess risk for these events was substantial (OR mortality 4.37, 95% CI 4.16-4.58; ICH 2.83, 2.47-3.24; CVA 2.92, 2.62-3.25; p < 0.001 for all).

CONCLUSIONS

Despite established mortality reductions with fibrinolysis for STEMI, elderly compared with younger patients, still have a three to four fold increased risk of mortality and adverse events when treated with fibrinolysis and antithrombin therapy in the modern era. These robust estimates of the anticipated rates for mortality, ICH, and CVA can be used as benchmarks to monitor the efficacy and safety of therapies in ongoing and newly completed clinical trials. We aimed to quantify the outcomes of death, intracranial hemorrhage (ICH), and total cerebrovascular accidents (CVA) in elderly compared with younger patients treated with fibrinolysis for STEMI based on a meta-analysis of 11 randomized clinical trials (1992-2001) of more than 3,000 patients. Elderly (n = 24,531) vs. younger (n = 123 568) patients had increased rates of mortality, ICH and CVA by 30-35 days; the excess risk was substantial (OR 4.37, 2.83, and 2.92 respectively, p < 0.001 for all). These robust estimates can be used as benchmarks to monitor the efficacy and safety of therapies in ongoing and newly completed clinical trials.

Bivalirudin: Pharmacology and Clinical Applications

Bivalirudin (Hirulog, Angiomax) is a specific, reversible and direct thrombin inhibitor with a predictable anticoagulant effect. It is cleared by both proteolytic cleavage and renal mechanisms, predominantly glomerular filtration. Bivalirudin inhibits both circulating thrombin and fibrin bound thrombin directly by binding to thrombin catalytic site and anion-binding exosite I in a concentration-dependent manner. Bivalirudin prolongs activated partial thromboplastin time, prothrombin time, thrombin time and activated clotting time (ACT). ACT levels with bivalirudin do not correlate with its clinical efficacy. Bivalirudin with a provisional GpIIb/IIIa inhibitor is indicated in elective contemporary percutaneous coronary intervention (PCI). In respect to combined ischemic and hemorrhagic endpoints of death, myocardial infarction, unplanned urgent revascularization and major bleeding during PCI (including subgroups of patients with renal impairment and diabetes) bivalirudin is not inferior to unfractioned heparin and planned GpIIb/IIIa inhibitors. In addition, bivalirudin has been consistently shown to have significantly less in-hospital major bleeding than heparin alone or heparin in combination with a GpIIb/IIIa inhibitor. Bivalirudin appears to be also safe and effective during PCI in patients with heparin-induced thrombocytopenia. Finally, data from PCI studies support the safety and efficacy of bivalirudin, although its direct randomized comparison with unfractionated heparin is lacking.

Update and rationale for ongoing acute myocardial infarction trials: combination therapy, facilitation, and myocardial preservation

Advancements in the treatment of myocardial infarction such as coronary care units, patient education, improved emergency response systems, and reperfusion therapy have reduced mortality. However, in an effort to further reduce the present rate by improving patency rates and microcirculatory perfusion, by better preserving myocardium, and/or treating shock more effectively, more research is under way to improve strategies now in place and to develop new, more effective ways to treat these patients.

Frequency of recurrent ST-elevation myocardial infarction after fibrinolytic therapy in a different territory as a manifestation of multiple unstable coronary arterial plaques

Multiple unstable plaques have been demonstrated by various imaging techniques in culprit and nonculprit arteries in patients with acute coronary syndromes, but the frequency with which clinical manifestations of multiple unstable plaques occur is unclear. To estimate this frequency in patients who present within 6 hours with ST-elevation myocardial infarction, we studied electrocardiograms and cardiac marker levels of 722 patients with suspected reinfarction in the HERO-2 trial of 17,073 patients; this trial compared intravenous bivalirudin with unfractionated heparin before administration of streptokinase. Twenty-six patients (3.6%) developed recurrent ST elevation in a different territory. Of all the patients who developed ST elevation in a different territory, 50% (13 of 26) did so during the 48 hours of randomized antithrombin therapy compared with 29% (140 of 487) of those who developed recurrent ST elevation in the index territory (p = 0.046). Recurrent index territory ST elevation occurred in 392 of 552 patients (71%) with confirmed reinfarction, and ST elevation in a new territory occurred in 21 patients (3.8%) with confirmed reinfarction (2.3% and 0.12% of all HERO-2 enrollees, respectively). These data suggest that clinical manifestation of multiple unstable plaques of recurrent ST elevation and reinfarction in a territory different from that of the index ST elevation myocardial infarction after intravenous fibrinolytic and antithrombin therapies is rare.

Cardiac tamponade in the fibrinolytic era: analysis of >100,000 patients with ST-segment elevation myocardial infarction

BACKGROUND

Cardiac tamponade is a life-threatening complication of acute myocardial infarction (MI). Data on the incidence, risk factors, and outcome of tamponade in patients with acute MI in the fibrinolytic era are limited.

METHODS

Data from a combined clinical trials database of ST-segment elevation MI were used to evaluate the incidence of cardiac tamponade, baseline characteristics, and outcomes in patients with and without tamponade. Univariable and multivariable analyses assessed the relationship between patient characteristics and tamponade development, and the influence of tamponade on mortality.

RESULTS

Of 102,060 patients, 865 (0.85%) developed isolated cardiac tamponade during initial hospitalization. Patients with tamponade were older (median 71.9 vs 61.6 years, P < .001), were more likely to be female (54.0% vs 25.1%, P < .001), were more likely to have an anterior MI (61.9% vs 41.5%, P < .001), and had a longer time from symptom onset to reperfusion (median 3.5 vs 2.8 hours, P < .001) than those without tamponade. Multivariable analyses identified increasing age, anterior MI location, female sex, and increased time from symptom onset to treatment as significant independent predictors of tamponade. Patients with tamponade had an increased death rate at 30 days (hazard ratio 7.9, 95% CI 4.7-13.5).

CONCLUSION

Cardiac tamponade occurs in < 1% of patients with fibrinolytic-treated acute MI and is associated with increased 30-day mortality. Time from symptom onset to treatment strongly predicted the development of tamponade, underscoring the need for continued efforts to increase speed to treatment in acute MI.

New Anticoagulant Agents: Direct Thrombin Inhibitors

Decades of research have been devoted to developing effective, safe, and convenient anticoagulant agents. In recent years, much emphasis has been placed on the development of direct thrombin inhibitors (DTIs) that offer benefits over agents like heparin and warfarin including the inhibition of both circulating and clot-bound thrombin; a more predictable anticoagulant response, because they do not bind to plasma proteins and are not neutralized by platelet factor 4; lack of required cofactors, such as antithrombin or heparin cofactor II; inhibiting thrombin-induced platelet aggregation; and absence of induction of immune-mediated thrombocytopenia. Various injectable DTIs are currently available and used for many indications. In addition, research is now focusing on oral DTIs that seem promising and offer various advantages, such as oral administration, predictable pharmacokinetics and pharmacodynamics, a broad therapeutic window, no routine monitoring, no significant drug interactions, and fixed-dose administration.

Treatment of heparin-induced thrombocytopenia in cardiovascular patients

Heparin-induced thrombocytopenia (HIT) is an antibody-mediated syndrome associated with heparin exposure, a falling platelet count and a high risk of thrombosis. Cardiovascular patients are at increased risk of HIT due to wide use of heparin in this population. Should HIT be suspected, heparin must be avoided in most situations, and anticoagulation with an alternative anticoagulant should be instituted. Preferred agents include the direct thrombin inhibitors argatroban and lepirudin, whilst bivalirudin or desirudin (other direct thrombin inhibitors) can be used in some situations. The indirect thrombin inhibitors, danaparoid and fondaparinux, can also be considered at times. These agents and their use in cardiac patients, including patients with acute coronary syndrome, percutaneous coronary interventions, acute ST elevation myocardial infarction or cardiac surgery, will be reviewed.

Outcomes of patients in clinical trials with ST-segment elevation myocardial infarction among countries with different gross national incomes

AIMS

To evaluate whether there is an association between 30-day mortality in patients with ST-segment elevation myocardial infarction (STEMI) included in clinical trials and country gross national income (GNI).

METHODS AND RESULTS

A retrospective analysis of the databases of five randomized trials including 50 310 patients with STEMI (COBALT 7169, GIK-2 2931, HERO-2 17,089, ASSENT-2 17,005, and ASSENT-3 6116 patients) from 53 countries was performed. Countries were divided into three groups according to their GNI based on the World Bank data: low (less than 2900 US dollars), medium (between 2900 US dollars and 9000 US dollars), and high GNI (more than 9000 US dollars per capita). Baseline characteristics, in-hospital management variables, and 30-day outcomes were evaluated. A previously defined logistic regression model was used to adjust for differences in baseline characteristics and to predict mortality. The observed mortality was higher than the predicted mortality in the low (12.1 vs. 11.8%) and in the medium income groups (9.4 vs. 7.9%), whereas it was lower in the high income group (4.9 vs. 5.6%).

CONCLUSION

An inverse relationship between mortality and GNI was observed in STEMI clinical trials. Most of the variability in mortality can be explained by differences in baseline characteristics; however, after adjustment, lower income countries have higher mortality than the expected.

New Anti-thrombotic Agents: Emphasis on Hemorrhagic Complications and Their Management

Our advanced knowledge of coagulation has led to the synthesis of novel procoagulant substances, such as recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark). Similarly, in-depth understanding of the interaction between anticoagulant proteins and their natural inhibitors has led to the synthesis of various novel anticoagulants. Novel anticoagulants are characterized by highly specific coagulation-inhibiting activities and, frequently, a complete lack of effective antidotes. This lack of antidotes is particularly important in the case of novel inhibitors with extended half-lives; for example, idraparinux may produce effective anticoagulation for as long as one week after subcutaneous administration. As novel anticoagulants complete licensing evaluations and are used in clinical practice, the likelihood of anticoagulant-associated hemorrhage will increase. This will require physicians to have an understanding of the mechanism of action of these anticoagulants, and to have an advanced degree of knowledge of the potential specific and nonspecific inhibitors of these anticoagulant agents. This paper will briefly review the biochemistry of coagulation, focusing on the complexes inhibited by currently available and novel anticoagulants. Specific and nonspecific prohemostatic agents will be reviewed and discussed. The ability of nonspecific procoagulant agents (particularly rFVIIa) to reverse the effects of novel anticoagulants will also be reviewed.

Appropriate invasive and conservative treatment approaches for patients with ST-Elevation MI

The combination of aspirin, heparin, and fibrinolytics was established in the late 1980s and early 1990s as the foundation for pharmacologic reperfusion therapy for ST-elevation myocardial infarction (STEMI). Since that time, many attempts have been made to improve on this regimen with limited success. In the late 1990s, primary percutaneous coronary intervention emerged as an invasive approach for reperfusion that offered superior outcomes to fibrinolytic therapy. However, timely access to experienced cardiac catheterization laboratories remains problematic for the majority of patients with STEMI. Meanwhile, recent advances in adjunctive antiplatelet and anticoagulation therapies have improved outcomes in patients undergoing pharmacologic reperfusion.

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

BACKGROUND

There is uncertainty about the role of intravenous unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) in patients with ST-elevation myocardial infarction (STEMI) treated with aspirin and thrombolysis.

METHODS AND RESULTS

We performed a meta-analysis of the randomized trials to assess the effect of UFH and LMWH on reinfarction, death, stroke, and bleeding. Fourteen trials involving a total of 25,280 patients were included (1239 comparing intravenous UFH versus placebo or no heparin; 16,943 comparing LMWH versus placebo; and 7098 comparing LMWH versus intravenous UFH). Intravenous UFH during hospitalization did not reduce reinfarction (3.5% versus 3.3%; odds ratio [OR], 1.08; 95% CI, 0.58 to 1.99) or death (4.8% versus 4.6%; OR, 1.04; 95% CI, 0.62 to 1.78) and did not increase major bleeding (4.2% versus 3.4%; OR, 1.21; 95% CI, 0.67 to 2.18) but increased minor bleeding (19.6% versus 12.5%; OR, 1.72; 95% CI, 1.22 to 2.43). During hospitalization/at 7 days, LMWH compared with placebo reduced the risk of reinfarction by approximately one quarter (1.6% versus 2.2%; OR, 0.72; 95% CI, 0.58 to 0.90; number needed to treat [NNT]=167) and death by &10% (7.8% versus 8.7%; OR, 0.90; 95% CI, 0.80 to 0.99; NNT=111) but increased major bleeding (1.1% versus 0.4%; OR, 2.70; 95% CI, 1.83 to 3.99; number needed to harm [NNH]=143) and intracranial bleeding (0.3% versus 0.1%; OR, 2.18; 95% CI, 1.07 to 4.52; NNH=500). The reduction in death with LMWH remained evident at 30 days. LMWH compared with UFH during hospitalization/at 7 days reduced reinfarction by &45% (3.0% versus 5.2%; OR, 0.57; 95% CI, 0.45 to 0.73; NNT=45), did not reduce death (4.8% versus 5.3%; OR, 0.92; 95% CI, 0.74 to 1.13) or increase major bleeding (3.3% versus 2.5%; OR, 1.30; 95% CI, 0.98 to 1.72), but increased minor bleeding (22.8% vs 19.4%; OR, 1.26; 95% CI, 1.12 to 1.43). The reduction in reinfarction remained evident at 30 days.

CONCLUSIONS

In aspirin-treated patients with STEMI who are treated with thrombolysis, intravenous UFH has not been shown to prevent reinfarction or death. LMWH given for 4 to 8 days compared with placebo reduces reinfarction by approximately one quarter and death by &10% and when directly compared with UFH reduces reinfarction by almost one half. These data suggest that LMWH should be the preferred antithrombin in this setting.

Safety of bivalirudin during percutaneous coronary interventions in patients with abnormal renal function

BACKGROUND

Chronic kidney disease is associated with an increased risk of ischemic and bleeding complications after percutaneous coronary intervention (PCI). Bivalirudin, a direct thrombin inhibitor, has been shown to reduce adverse bleeding events compared to unfractionated heparin in patients undergoing PCI. However, the effect of diminished renal function on the safety and efficacy of bivalirudin for PCI is unknown. We aimed to test the safety of bivalirudin in routine practice and to assess whether this benefit was influenced by renal function.

METHODS AND RESULTS

The interaction between renal impairment and benefit from bivalirudin was assessed in 115 consecutive patients (age 68.5+/-12.1, 45% female) undergoing PCI. Bivalirudin dosing was adjusted based on renal function. Creatinine clearance (CrCl) was calculated using the Cockroft-Gault formula. The composite endpoints of in-hospital death, myocardial infarction or revascularization and bleeding events were assessed. Overall, these events occurred in 10 (8.7%) patients. Patients with a CrCl<60 ml/min had a significantly increased risk for in-hospital complications (18.6 versus 2.78%, P = 0.011). Univariate analysis for MACE and bleeding were significant for CrCl<60 ml/min OR: 2.54 (95% CI: 1.61-39.7, P = 0.011), age OR: 3.29 (95% CI: 1.07-1.39, P<0.001) and female gender OR: 2.1 (95% CI: 0.036-0.89, P = 0.036). Risk of complications increased with decreasing renal function: 2.7, 14.2, and 37.5% for CrCl of >60, 30-60 or <30 ml/min, respectively, P = 0.002).

CONCLUSION

Advanced age, renal dysfunction, and female gender remain important risk factors for ischemic and bleeding complications in patients undergoing PCI with bivalirudin.

Prognostic differences between different types of bundle branch block during the early phase of acute myocardial infarction: insights from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial

AIMS

Bundle branch block (BBB) early during acute myocardial infarction (AMI) is often considered high risk for mortality. Little is known about how different BBB types influence prognosis.

METHODS AND RESULTS

The HERO-2 trial recruited 17 073 patients with ischaemic symptoms lasting >30 min and either ST elevation with or without right bundle branch block (RBBB) or presumed-new left bundle branch block (LBBB). Electrocardiograms were performed before and 60 min after the start of fibrinolytic therapy. Using patients with normal intraventricular conduction as a reference, odds ratios (ORs) for 30-day mortality were calculated for different BBB types (LBBB, RBBB with anterior AMI, and RBBB with inferior AMI) present at randomization and/or 60 min, with adjustment for recruitment region, pre-infarction characteristics, time to randomization, hemodynamics, and Killip class. At randomization, the 873 patients (5.11%) with BBB had worse baseline characteristics than patients without BBB. In patients presenting with LBBB (n=300), the ORs for 30-day mortality were 1.90 (95% CI 1.39-2.59) before and 0.68 (0.48-0.99) after adjustment for other prognosticators. In patients presenting with RBBB (n=415) and anterior AMI, the ORs were 3.52 (2.82-4.38) before and 2.48 (1.93-3.19) after adjustment. In patients presenting with RBBB and inferior AMI (n=158), the ORs were 1.74 (1.06-2.86) before and 1.22 (0.71-2.08) after adjustment. Within 60 min, 143 patients (0.92%) developed new BBB. The adjusted ORs for 30-day mortality were 2.97 (1.16-7.57) in the 25 patients with new LBBB, 3.84 (2.38-6.22) in the 100 with new RBBB and anterior AMI, and 2.23 (0.54-9.21) in the 18 with new RBBB and inferior AMI.

CONCLUSION

RBBB accompanying anterior AMI at presentation and new BBB (including LBBB) early after fibrinolytic therapy are independent predictors of high 30-day mortality. These electrocardiographic features should be considered in risk stratification to identify high-risk patients.

New anticoagulants in ischemic heart disease

Fibrinolysis is the reference treatment for most myocardial infarctions with ST-segment elevation; alternatives are angioplasty, with or without stent. The earlier fibrinolysis is performed (preferably before hospitalization), the more effective it is. It can be optimized by adjuvant antiplatelet therapy, such as aspirin, and probably by anticoagulant treatment as well. Because fibrinolytic therapy is accompanied by intensive thrombin generation and activation, immediate and continuous adjunctive simultaneous heparin therapy is recommended. The efficacy of subcutaneous low-molecular-weight heparin (LMWH) HBPM) is at least equivalent to that of intravenous unfractionated heparin (UFH), but its risk of severe (but not cerebral) hemorrhage is greater. Bolus LMWH on the other hand is associated with an increased risk of cerebral hemorrhage. Antithrombotic treatment thus appears optimal with bolus UFH at fibrinolysis and for at least 48 hours afterwards. An alternative after this bolus might be subcutaneous enoxaparin until discharge. Because the major drawback of both types of heparin is their rebound activation of thrombosis, oral anticoagulants are recommended thereafter. The combination of anticoagulant treatment + (low-dose) aspirin is not superior to aspirin alone when the target INR is below 2. Adequate anticoagulation with INRs greater than 2.0 consistently improves angiographic and clinical outcome. Bleeding (except intracerebral) is significantly increased whether the INR is greater than or less than 2.0. Other treatments are being investigated. Pentasaccharide (anti-Xa) combined with fibrinolysis seems to reduce reocclusion more effectively than UFH. Oral postinfarction treatment with ximelagatran (a thrombin inhibitor), combined with aspirin, is associated with fewer cardiovascular events than aspirin alone. More studies are needed.

Patients With Prolonged Ischemic Chest Pain and Presumed-New Left Bundle Branch Block Have Heterogeneous Outcomes Depending on the Presence of ST-Segment Changes

OBJECTIVES

The purpose of this research was to examine the prognostic value of ST-segment changes (concordant ST-segment elevation and/or precordial V1 to V3 ST-segment depression) during presumed-new left bundle branch block (LBBB) in patients receiving fibrinolytic therapy.

BACKGROUND

These patients are often considered high-risk, but their outcome is not well-defined.

METHODS

The Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial compared bivalirudin with heparin in patients receiving streptokinase for ST-segment elevation or presumed-new LBBB. Each patient with LBBB was matched with a control (with normal intraventricular conduction) for age, gender, pulse rate, systolic blood pressure, Killip class, and region.

RESULTS

A total of 300 patients had LBBB (92 with and 208 without ST-segment changes) and 15,340 had normal conduction. Acute myocardial infarction (AMI) occurred in 80.7% of LBBB patients and 88.7% of controls (p = 0.006). ST-segment changes were specific (96.6%) but not sensitive (37.8%) for enzymatic diagnosis of AMI. Mortality at 30 days was similar in LBBB patients with ST-segment changes (21.7%) and controls (25.0%, p = 0.563), but lower in LBBB patients without ST-segment changes than in controls (13.5% vs. 21.6%, p = 0.022). In the whole HERO-2 cohort, the LBBB patients with ST-segment changes had higher mortality than patients with normal conduction (odds ratio [OR] 1.37, 95% confidence interval [CI] 0.78 to 2.42). The LBBB patients without ST-segment changes had lower mortality than patients with normal conduction (OR 0.52, 95% CI 0.33 to 0.80).

CONCLUSIONS

ST-segment changes during LBBB are specific for the diagnosis of AMI and predict 30-day mortality; LBBB patients without ST-segment changes have lower adjusted 30-day mortality than those with normal conduction. Trials are required to determine the best treatment for high-risk and low-risk patients with LBBB.

Bleeding in Cardiac Surgery: Its Prevention and Treatment—an Evidence-Based Review

Expected and unexpected bleeding occur frequently in patients undergoing cardiac surgery. Bleeding after cardiac surgery can be broadly divided into two groups: surgical (unrecognized bleeding vessel, anastomosis, or other suture line) or nonsurgical bleeding (caused by coagulopathy). Factors influencing both surgical and nonsurgical bleeding can be further broken down into those occurring preoperatively and those that occur intraoperatively and postoperatively. A thorough understanding of these factors is necessary to reduce bleeding. This is a desirable clinical goal, because excessive bleeding is associated with adverse outcomes.

Facilitated percutaneous coronary intervention: is this strategy ready for implementation?

Reperfusion therapy with pharmacologic fibrinolysis has provided striking reductions in mortality following acute ST-elevation myocardial infarction (STEMI). Nevertheless, the limitations of fibrinolysis are well recognized. Attempts to improve reperfusion with bolus-only fibrinolysis, and combination regimens including enoxaparin and glycoprotein IIb/IIIa inhibition have not led to improvements in mortality. Although both prehospital fibrinolysis and primary percutaneous coronary intervention (PCI) have reduced mortality, these strategies are associated with considerable logistic constraints, hampering widespread implementation. Potentially, a hybrid strategy combining the speed and simplicity of pharmacologic reperfusion with the ability to ensure epicardial vessel patency, and providing definitive management of the culprit lesion remains an attractive option. Facilitated PCI for STEMI may extend the benefit of myocardial reperfusion to a greater number of patients. The true benefit of this strategy will be defined by ongoing large-scale clinical trials. If results are positive, the clinical practice determinants required for the effective application of this strategy to the wider clinical community will need careful consideration.

Heart failure on admission and the risk of stroke following acute myocardial infarction: the VALIANT registry

AIMS

We sought to assess the relative contribution of heart failure (HF) on admission for an acute myocardial infarction (MI) to the subsequent in-hospital stroke risk.

METHODS AND RESULTS

The VALsartan In Acute myocardial iNfarcTion (VALIANT) registry enrolled 5573 consecutive MI patients at 84 international sites from 1999 to 2001. We calculated odds ratios (ORs) for stroke and adjusted for baseline characteristics, Killip Class, and risk factors for stroke, such as diabetes and prior HF. In-hospital stroke occurred in 81 (1.5%) patients. HF was present on admission in 38% of patients who developed a stroke and in 24% who did not (P=0.001). Older age (OR 1.03 increase/year, 95% confidence interval (CI) 1.01-1.04), Killip Class III (OR 1.66, CI 0.86-3.19) or IV (OR 4.85, CI 1.69-13.93), history of hypertension (OR 1.73, CI 1.06-2.82), and history of stroke (OR 1.89, CI 1.06-3.37) were more common in patients who had in-hospital stroke. In-hospital mortality in patients with and without stroke was 27.2 and 6.5%, respectively (P<0.001).

CONCLUSION

Patients with stroke after MI have a dismal prognosis. The presence of HF on admission for an acute MI increases in-hospital stroke risk. HF treatments may modify the risk of stroke.

Treatment of acute coronary syndromes in patients who have chronic kidney disease

Patients with CKD and CAD have traditionally been a difficult population to diagnose and treat in the setting of ACS. In addition to having poorer outcomes post-ACS, data are lacking regarding best treatments available. Aggressive interventional and medical treatments in this group with already poor outcomes are not necessarily contraindicated and should always be considered. The appalling outcome for CKD patients post-ACS is improved by many therapies shown to benefit in the non-CKD patients. Data suggest that troponins are useful markers in CKD patients, that major bleeding is not increased with the use of GP IIb-IIIa antagonists, that thrombolytics have been used successfully in CKD patients, and that PCI electively and as a primary treatment for ACS is successful and probably more beneficial to treatment.

Novel uses for current and future direct thrombin inhibitors: focus on ximelagatran and bivalirudin

Ximelagatran and bivalirudin are direct thrombin inhibitors that have been studied for the prevention and treatment of thrombosis and have potential advantages over the traditional indirect thrombin inhibitors (i.e., warfarin, unfractionated heparin and low molecular-weight heparin). They are both reversible inhibitors of thrombin and block both circulating and fibrin-bound thrombin. Ximelagatran and bivalirudin possess favourable pharmacokinetic and pharmacodynamic profiles including wider therapeutic indices, faster onsets of action and less interpatient variability compared to indirect thrombin inhibitors. Ximelagatran has shown favourable clinical trial results in venous thromboembolism prophylaxis and atrial fibrillation. Similarly, bivalirudin has shown positive results in patients with acute coronary syndromes, however, further investigation is needed. Ximelagatran and bivalirudin have shown promising results in the management of thrombosis and the results of future studies confirming their use for the aforementioned indications are anticipated.

Cardiac surgery in patients on antiplatelet and antithrombotic agents

The widespread application of antithrombotic agents carries significant potential for inducing excessive peri-operative hemorrhage during cardiac surgery. Specific surgical and medical strategies can be employed to attenuate this bleeding. These antithrombotic agents and anti-hemorrhagic measures will be reviewed in depth.

Thrombolytic Therapy: Current Clinical Practice

Thrombolytic therapy is an essential tool in the array of therapies designed to reopen arteries and veins occluded with thrombus. As the use of thrombolytic agents has entered mainstream practice, their application has expanded to include a wide variety of indications and settings. Thrombolytic agents are used in patients who have thrombosis of coronary arteries, precerebral and cerebral arteries, the aorta, iliac and mesenteric arteries, and peripheral arteries. The use of thrombolysis in venous thrombosis has included deep venous thrombosis of the upper and lower extremities and vena cava, mesenteric veins, cerebral veins, and central access catheters. Guidelines are available from the American College of Cardiology/American Heart Association regarding thrombolysis in myocardial infarction and from the American Stroke Association regarding thrombolysis in acute ischemic stroke.

Reperfusion strategies for acute myocardial infarction in the elderly

The optimal reperfusion strategy in elderly patients with ST-segment elevation myocardial infarction (STEMI) remains a topic of debate. This lack of consensus stems from the exclusion or under-representation of the elderly in clinical trials. This review evaluates the available literature pertaining to reperfusion therapy for the treatment of STEMI in the elderly. We identified all published studies evaluating the effectiveness of thrombolytic therapy, primary percutaneous coronary intervention (PCI), or adjunctive therapies to reperfusion by conducting an electronic search of MEDLINE through December 2003. Meta-analysis of clinical trials suggests a survival benefit of thrombolytic therapy in the elderly with STEMI, whereas some observational studies have raised concerns about the lack of short-term benefit or possibility of harm with thrombolysis. However, most observational studies demonstrate improved intermediate-term survival with thrombolysis. In contrast, multiple clinical trials and observational studies indicate improved survival and low risk of stroke with primary PCI compared with thrombolysis in elderly patients with STEMI. Information on the efficacy of newer antithrombotic agents as adjunct to thrombolysis or primary PCI is scarce. Available data suggest an increased risk of intracerebral bleeding with the combination of a fibrin-specific agent and a glycoprotein IIb/IIIa receptor antagonist in patients >75 years of age. Clearly targeted large-scale clinical trials are needed to evaluate the relative merits of available reperfusion strategies as well as newer antithrombotic adjunctive therapies in the elderly with STEMI.

Challenges in the conduct of large simple trials of important generic questions in resource-poor settings: the CREATE and ECLA trial program evaluating GIK (glucose, insulin and potassium) and low-molecular-weight heparin in acute myocardial infarction

Background

Approximately 15.5 million deaths from cardiovascular diseases occur every year. About half are due to acute myocardial infarction (AMI), and 80% occur in low- and middle-income countries. Therefore, low-cost therapies would be invaluable. Although glucose-insulin-potassium (GIK) infusion and low-molecular-weight heparin (LMWH) appear to be promising in AMI, the available trials are inconclusive and these treatments require rigorous evaluation.

Methods

The Clinical Trial of Reviparin and Metabolic Modulation in Acute Myocardial Infarction Treatment and Evaluation-Estudios Clínicos Latino America (CREATE-ECLA) study is a randomized controlled trial in ST-elevation AMI patients evaluating a 24-hour infusion of Glucose-Insulin-Potassium (GIK) intravenous vs usual care (control) on 30-day mortality in 20 000 patients from 21 countries. Patients from India and China (n = 15 000) are also randomized using a factorial design to receive low-molecular-weight heparin (Reviparin) or placebo injection twice daily for 7 days to assess the impact on the composite outcomes of death, reinfarction or stroke (first co-primary outcome) or the composite + refractory ischemia (second co-primary outcome).

Results

Twenty thousand two hundred and one (20,201) GIK/control patients and 15,570 Reviparin/placebo patients have been included, with results expected in November 2004.

Conclusions

The CREATE-ECLA trial will provide definitive answers to the role of 2 practical, promising and low-cost therapies, LMWH and GIK, in AMI patients. If effective, these therapies could be used in small medical centers in low- and middle- income countries. The experiences in this trial indicate that large trials of important questions can be successfully conducted in resource-poor settings, by academic groups without industry involvement.

Acute coronary syndromes in women: is treatment different? Should it be?

The vast majority of acute coronary syndrome (ACS) trials conducted over the past two decades support the view that women have persistently higher mortality and morbidity despite the introduction of new medical therapies and devices. Even after adjustment for older age, higher prevalence of diabetes, hypertension, heart failure, smaller vessel size, and late presentation, some studies still point to a persistent sex disadvantage. Even in contemporary practice, women continue to have longer delays in presentation and treatment. Selection bias in unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI) trials allows inclusion of large numbers of women with clinically insignificant coronary disease and may mistakenly shift results toward apparent benefit of a less aggressive approach. This bias causes further difficulty in determining efficacy and safety of new antithrombotic agents such as direct thrombin inhibitors and glycoprotein IIb/IIa inhibitors across the spectrum of ACS. In trials of UA/NSTEMI, use of objective evidence of ischemia such as elevated troponin levels, would greatly assist the determination of efficacy and benefit in women. Enrollment of more women in clinical trials and timely sex-specific analysis would promote a better understanding of the role of female gender in ACS and would facilitate better care of all patients.