Bivalirudin as a replacement for unfractionated heparin in unstable angina/non-ST-elevation myocardial infarction: observations from the TIMI 8 trial. The Thrombolysis in Myocardial Infarction

Downstream or upstream administration of P2Y12 receptor blockers in non-ST elevated acute coronary syndromes: study protocol for a randomized controlled trial

BACKGROUND

The optimal timing to administer a P2Y12 inhibitor in patients presenting with a non-ST elevation acute coronary syndrome remains a topic of debate. Pretreatment with ticagrelor before coronary anatomy is known as a widely adopted strategy. However, there is poor evidence on how this compares with administration of a P2Y12 inhibitor after defining coronary anatomy (i.e., downstream administration). Moreover, there are limited head-to-head comparisons of the two P2Y12 inhibitors-ticagrelor and prasugrel-currently recommended by the guidelines.

STUDY DESIGN

DUBIUS is a phase 4, multicenter, parallel-group, double randomized study conducted in NSTE-ACS patients designed to compare a pretreatment strategy (including only ticagrelor) versus a downstream strategy (including prasugrel or ticagrelor) and to compare downstream prasugrel with downstream ticagrelor. A total of 2520 patients will be randomly assigned to pretreatment with ticagrelor or to no pretreatment. The PCI group of the downstream arm will be further randomized to receive prasugrel or ticagrelor. The two primary hypotheses are that the downstream strategy is superior to the upstream strategy and that downstream ticagrelor is non-inferior to downstream prasugrel, both measured by the incidence of a composite efficacy and safety endpoint of death from vascular causes, non-fatal MI, or non-fatal stroke, and Bleeding Academic Research Consortium (BARC) type 3, 4, and 5 bleedings.

CONCLUSIONS

The DUBIUS study will provide important evidence related to the benefits and risks of pretreatment with ticagrelor compared with a strategy of no pretreatment. Moreover, the clinical impact of using downstream ticagrelor compared with downstream prasugrel will be assessed.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02618837 . Registered on 1 December 2015.

Individual Patient Data Pooled Analysis of Randomized Trials of Bivalirudin versus Heparin in Acute Myocardial Infarction: Rationale and Methodology

BACKGROUND

 Individual randomized controlled trials (RCTs) of periprocedural anticoagulation with bivalirudin versus heparin during percutaneous coronary intervention (PCI) have reported conflicting results. Study-level meta-analyses lack granularity to adjust for confounders, explore heterogeneity, or identify subgroups that may particularly benefit or be harmed.

OBJECTIVE

 To overcome these limitations, we sought to develop an individual patient-data pooled database of RCTs comparing bivalirudin versus heparin.

METHODS

 We conducted a systematic review to identify RCTs in which ≥1,000 patients with acute myocardial infarction (AMI) undergoing PCI were randomized to bivalirudin versus heparin.

RESULTS

 From 738 identified studies, 8 RCTs met the prespecified criteria. The principal investigators of each study agreed to provide patient-level data. The data were pooled and checked for accuracy against trial publications, with discrepancies addressed by consulting with the trialists. Consensus-based definitions were created to resolve differing antithrombotic, procedural, and outcome definitions. The project required 3.5 years to complete, and the final database includes 27,409 patients (13,346 randomized to bivalirudin and 14,063 randomized to heparin).

CONCLUSION

 We have created a large individual patient database of bivalirudin versus heparin RCTs in patients with AMI undergoing PCI. This endeavor may help identify the optimal periprocedural anticoagulation regimen for patient groups with different relative risks of adverse ischemic versus bleeding events, including those with ST-segment and non-ST-segment elevation MI, radial versus femoral access, use of a prolonged bivalirudin infusion or glycoprotein inhibitors, and others. Adherence to standardized techniques and rigorous validation processes should increase confidence in the accuracy and robustness of the results.

Critical Appraisal of Bivalirudin versus Heparin for Percutaneous Coronary Intervention: A Meta-Analysis of Randomized Trials

Percutaneous coronary intervention with bivalirudin plus bail-out glycoprotein IIb/IIIa inhibitors has been shown to be as effective as unfractionated heparin plus routine glycoprotein IIb/IIIa inhibitors in preventing cardiac ischemic events, but with a lower bleeding risk. It is unknown whether bivalirudin would have the same beneficial effects if compared with heparin when the use of glycoprotein IIb/IIIa inhibitors was similar between treatment arms. We searched the MEDLINE, Web of Science, and Cochrane databases from inception until March 2015 for randomized trials that compared bivalirudin to heparin in patients undergoing percutaneous coronary intervention. We required that the intended use of glycoprotein IIb/IIIa inhibitors was similar between the study groups. Summary estimates were principally constructed by the Peto method. Fifteen trials met our inclusion criteria, which yielded 25,824 patients. Bivalirudin versus heparin was associated with an increased hazard of stent thrombosis (odds ratio [OR] 1.49, 95% confidence interval [CI] 1.15-1.92, P = .002, I² = 16.9%), with a similar hazard of myocardial infarction (OR 1.09, 95% CI 0.98-1.22, P = .11, I² = 35.8%), all-cause mortality (OR 0.88, 95% CI 0.72-1.08, P = .21, I² = 31.5%) and major adverse cardiac events (OR 1.04, 95% CI 0.94-1.14, P = .46, I² = 53.9%). Bivalirudin was associated with a reduced hazard of major bleeding (OR 0.80, 95% CI 0.70-0.92, P = .001, I² = 63.5%). The dose of heparin in the control arm modified this association; when the dose of unfractionated heparin in the control arm was ≥ 100 units/kg, bivalirudin was associated with a reduction in major bleeding (OR 0.55, 95% CI 0.45-0.68, P < .0001), but when the dose of unfractionated heparin was ≤ 75 units/kg, bivalirudin was not associated with reduction in bleeding (OR 1.09, 95% CI 0.91-1.31, P = .36). Among patients undergoing PCI, bivalirudin was associated with an increased hazard of stent thrombosis. Bivalirudin may be associated with a reduced hazard of major bleeding; however, this benefit was no longer apparent when compared with a dose of unfractionated heparin ≤ 75 units/kg.

Bivalirudin: an anticoagulant option for percutaneous coronary intervention

Coronary artery thrombosis is usually triggered by platelet-rich thrombus superimposed on a spontaneously or mechanically disrupted atherosclerotic plaque. Thrombin and platelets both play a role in this process. Unfractionated heparin and aspirin have served as cornerstones in the prevention and treatment of intracoronary thrombus, but unfractionated heparin has several limitations that necessitate the use of adjunctive therapies, such as glycoprotein IIb/IIIa receptor inhibitors and clopidogrel, in order to reduce the risk of ischemic events. These combination therapies, however, typically increase the risk for bleeding complications, as well as the cost and complexity of treatment. Bivalirudin (Angiomax, The Medicines Company), a thrombin-specific anticoagulant, does not share heparin's limitations. Bivalirudin appears to provide clinical advantages over unfractionated heparin therapy in acute coronary syndrome patients and those undergoing percutaneous coronary intervention, without increasing cost or complexity of treatment for most patients.

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.

Percutaneous coronary intervention in patients with acute coronary syndrome: focus on bivalirudin

Previously, indirect thrombin inhibitors such as unfractionated heparin or low-molecular-weight heparin were used as a standard anticoagulation during percutaneous coronary intervention to prevent procedural thrombotic complications but at a risk of hemorrhagic complications. More recently, bivalirudin, a member of the direct thrombin inhibitor class, has been shown to have 1) predictable pharmacokinetics, 2) ability to inhibit free- and clot-bound thrombin, 3) no properties of platelet activation, 4) avoidance of heparin-induced thrombocytopenia, and 5) a significant reduction of bleeding without a reduction in thrombotic or ischemic endpoints compared to heparin and glycoprotein IIbIIIa inhibitors when used in patients presenting with acute coronary syndrome who are planned for an invasive treatment strategy.

Percutaneous coronary interventions in patients with heparin-induced thrombocytopenia

Accomplishing a successful percutaneous coronary intervention in a patient with a suspected or diagnosed heparin-induced thrombocytopenia (HIT) requires the selection of an appropriate alternative anticoagulant and a thorough assessment of bleeding and thrombotic risks. In this review, we suggest an evidence-based management algorithm that takes into account the clinical phase of HIT (acute, recent, and remote HIT) and the associated risk when patients present with acute coronary syndrome. The algorithm also integrates preventive measures directed at decreasing the bleeding risk associated with the antithrombotic and invasive therapies used for HIT and percutaneous coronary intervention.

Variation in the definitions of bleeding in clinical trials of patients with acute coronary syndromes and undergoing percutaneous coronary interventions and its impact on the apparent safety of antithrombotic drugs

BACKGROUND

This review compares and contrasts the various criteria used to characterize bleeding (particularly major bleeding) during recent studies of antithrombotic therapies in acute coronary syndromes (ACSs) and/or percutaneous coronary intervention (PCI).

METHODS

This review includes an analysis of recent large randomized clinical trials (published between January 2000 and September 2006; n > 3000 patients) evaluating antithrombotic drugs in patients with ACS or patients undergoing PCI who were identified using Medline searches.

RESULTS

Bleeding has been shown to correlate with patient mortality and major cardiovascular events. Different definitions of bleeding, other than Thrombolysis In Myocardial Infarction or Global Utilization of Streptokinase and t-PA for Occluded coronary arteries bleeding criteria, were used in 9 of the 13 randomized trials that were identified and enrolled over 178,000 patients in total. These definitions overlapped to a degree but differed substantially. Bleeding rates according to several bleeding criteria within one trial illustrate that different bleeding definitions can lead to markedly different conclusions about the safety of an antithrombotic regimen. The shift toward identifying therapies that specifically attempt to reduce bleeding while maintaining efficacy at reducing ischemic complications increases the need of standardized bleeding definitions.

CONCLUSIONS

A task force should be initiated to formulate an internationally accepted, meaningful, and standardized approach for reporting bleeding events. A fixed definition may not work for all disease states throughout ACS and PCI. Rather, a predefined scale of bleeding can be proposed, which moves from a more liberal definition of bleeding for elective PCI to a more conservative definition in other settings such as rescue angioplasty.

New anticoagulant options for ST-elevation myocardial infarction and unstable angina pectoris/non-ST-elevation myocardial infarction

In addition to antiplatelet therapy with aspirin, anticoagulation therapy with unfractionated heparin decreases the risk of myocardial infarction and death in patients with acute coronary syndromes. However, unfractionated heparin has pharmacologic limitations that limit efficacy and safety. Enoxaparin, fondaparinux, and bivalirudin are new anticoagulant therapy options with either superior efficacy or better safety than unfractionated heparin. Compared with unfractionated heparin, enoxaparin and fondaparinux are easier to administer, do not require monitoring, and facilitate longer treatment duration. Bivalirudin offers advantages for patients undergoing early percutaneous revascularization. Careful attention to dosing and excellent vascular access site management after cardiac catheterization are required to decrease the risk of bleeding and blood transfusion, which have been associated with increased mortality risk.

Antithrombotic strategies in non-ST elevation acute coronary syndromes: focus on bivalirudin

Acute coronary syndromes (ACS) are a common presentation of coronary artery disease, accounting for more than one million hospital admissions in the US annually. Owing to high rates of mortality and reinfarction, ACS represent a major public health concern. The following review discusses the pathogenesis of ACS and optimal approaches for the management of patients with ACS, with special focus on new antithrombotic strategies, including the direct thrombin inhibitor bivalirudin. Bivalirudin has several notable mechanistic advantages compared with unfractionated heparin, including activity against clot-bound thrombin, inhibition of thrombin-induced platelet activation, short plasma half-life in patients with normal or mildly impaired renal function (25 minutes), and linear pharmacokinetics less affected by plasma proteins and renal insufficiency. These properties provide a more predictable inhibition of coagulant activity than unfractionated heparin, with less degree of inter-patient variability in anticoagulation response. The findings from the several clinical trials assessing safety and efficacy of bivalirudin are analyzed in detail, including the recent randomized controlled Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial. Based on the results of the ACUITY trial, a newer streamlined strategy for the invasive treatment of moderate- and high-risk patients with ACS is discussed.

Anticoagulant therapy in acute coronary syndromes

Thrombus formation on a disrupted atherosclerotic coronary artery plaque is the usual event that precipitates acute coronary syndromes (ACS). Anticoagulation therapy with unfractionated heparin, in addition to antiplatelet therapy with aspirin, decreases the risk of myocardial infarction and death with ACS. However, unfractionated heparin has pharmacological limitations that limit efficacy and safety. Low-molecular-weight heparins (enoxaparin), direct thrombin inhibitors (bivalirudin) and Factor Xa inhibitors (fondaparinux) are new anticoagulant therapy options with either superior efficacy or improved safety over unfractionated heparin. Compared with unfractionated heparin, enoxaparin and fondaparinux are easier to administer, do not require monitoring and facilitate longer treatment duration. Bivalirudin offers advantages for patients undergoing percutaneous revascularization. Careful attention to dosing and excellent vascular access site management are required to decrease the risk of bleeding and blood transfusion, which have been associated with increased mortality risk.

Pharmacological antithrombotic adjuncts to percutaneous coronary intervention

Stent thrombosis is the major cause of early adverse events during percutaneous coronary intervention. Its incidence has fallen considerably in recent years, principally due to the introduction of effective antithrombotic therapies. The selection of an appropriate antithrombotic regimen is critical in achieving a balance between reducing ischaemic events and minimising bleeding complications in patients undergoing percutaneous coronary intervention. In this article, evidence for the role of antiplatelet and anticoagulant therapies is discussed, including the thienopyridines, glycoprotein IIb/IIIa receptor antagonists, direct thrombin inhibitors and pentasaccharides.

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.

Bivalirudin for patients with acute coronary syndromes

BACKGROUND

Current guidelines for patients with moderate- or high-risk acute coronary syndromes recommend an early invasive approach with concomitant antithrombotic therapy, including aspirin, clopidogrel, unfractionated or low-molecular-weight heparin, and glycoprotein IIb/IIIa inhibitors. We evaluated the role of thrombin-specific anticoagulation with bivalirudin in such patients.

METHODS

We assigned 13,819 patients with acute coronary syndromes to one of three antithrombotic regimens: unfractionated heparin or enoxaparin plus a glycoprotein IIb/IIIa inhibitor, bivalirudin plus a glycoprotein IIb/IIIa inhibitor, or bivalirudin alone. The primary end points were a composite ischemia end point (death, myocardial infarction, or unplanned revascularization for ischemia), major bleeding, and the net clinical outcome, defined as the combination of composite ischemia or major bleeding.

RESULTS

Bivalirudin plus a glycoprotein IIb/IIIa inhibitor, as compared with heparin plus a glycoprotein IIb/IIIa inhibitor, was associated with noninferior 30-day rates of the composite ischemia end point (7.7% and 7.3%, respectively), major bleeding (5.3% and 5.7%), and the net clinical outcome end point (11.8% and 11.7%). Bivalirudin alone, as compared with heparin plus a glycoprotein IIb/IIIa inhibitor, was associated with a noninferior rate of the composite ischemia end point (7.8% and 7.3%, respectively; P=0.32; relative risk, 1.08; 95% confidence interval [CI], 0.93 to 1.24) and significantly reduced rates of major bleeding (3.0% vs. 5.7%; P<0.001; relative risk, 0.53; 95% CI, 0.43 to 0.65) and the net clinical outcome end point (10.1% vs. 11.7%; P=0.02; relative risk, 0.86; 95% CI, 0.77 to 0.97).

CONCLUSIONS

In patients with moderate- or high-risk acute coronary syndromes who were undergoing invasive treatment with glycoprotein IIb/IIIa inhibitors, bivalirudin was associated with rates of ischemia and bleeding that were similar to those with heparin. Bivalirudin alone was associated with similar rates of ischemia and significantly lower rates of bleeding. (ClinicalTrials.gov number, NCT00093158 [ClinicalTrials.gov].).

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.

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

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

Bivalirudin as an Anticoagulation Agent: Safety and Efficacy in Peripheral Interventions

PURPOSE

Traditionally, unfractionated heparin is used to prevent thrombotic complications in peripheral interventions. The purpose of this study is to evaluate the use of bivalirudin as the anticoagulant agent for peripheral interventions.

MATERIALS AND METHODS

A retrospective analysis of 108 patients who underwent 110 peripheral interventions between January 2002 and January 2004 and received bivalirudin as the sole anticoagulation agent was conducted at Baptist Cardiac and Vascular Institute. Interventions were performed in the following areas: iliac, femoropopliteal, and distal (n = 55), carotid (n = 31), vertebral (n = 1), renal (n = 14), aorta (n = 7), and subclavian (n = 2). The following procedural and clinical endpoints were examined: death, requirement of urgent surgery or surgery during the same admission, urgent percutaneous revascularization in the same treated vessel, thrombotic or embolic events, bleeding events, and groin complications.

RESULTS

A total of 266 lesions were dilated in 185 arteries. There were no procedural mortalities, procedural success was 99.1%, and the complication rate was 3.6%. There was one embolic stroke (0.9%), one thrombosis (0.9%), and two groin hematomas (1.8%). No patient required urgent surgery or reintervention in the same treated vessel. No complications were noted at 7 days after the procedure. There were two interventions by postprocedure day 30: toe amputation and groin debridement.

CONCLUSION

Bivalirudin is a safe alternative to unfractionated heparin as the anticoagulation agent in peripheral interventions. This study shows that the complication profile is comparable to other bivalirudin studies. Bivalirudin is effective, easy to use, and is associated with few bleeding complications.

Bivalirudin: a review

Bivalirudin (Angiomax) is a thrombin-inhibiting oligopeptide that was developed via rational drug design as a hirudin analogue ('hirulog'). Similar to hirudin, it is a bivalent thrombin inhibitor, as its 20-amino acid structure combines a carboxy-terminal region that recognises thrombin's fibrin(ogen)-binding site, and an amino-terminal tetrapeptide that inhibits the active site of thrombin, connected by a tetraglycine spacer. It has certain pharmacological advantages over hirudin, including enzymic metabolism (less dependence on renal clearance) and low immunogenicity (reduced potential for anaphylaxis). Bivalirudin is approved for use in percutaneous transluminal coronary angioplasty (PTCA), and is undergoing active investigation for anticoagulation during cardiac surgery, both 'off-pump' and with cardiopulmonary bypass ('on-pump'). Anecdotal 'off-label' experience for the treatment of heparin-induced thrombocytopenia shows promise.

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.

Thrombocytopenia in Cardiovascular Patients

Thrombocytopenia is a common problem in cardiovascular patients, but the etiology and management of this condition may be different than those in other populations. Around the time that percutaneous coronary interventions are performed, the drugs most commonly associated with thrombocytopenia are the glycoprotein (GP) IIb/IIIa receptor inhibitors and heparin. Thienopyridines only rarely cause thrombocytopenia. Patients with non-ST-elevation acute coronary syndromes may be exposed to prolonged heparin infusions, GPIIb/IIIa inhibitors, and thienopyridines. After open-heart surgery, as opposed to other surgical procedures, the platelet count falls, primarily due to platelet damage and destruction in the bypass circuit and hemodilution. Heparin is the most common drug to be implicated in thrombocytopenia in ICU patients. Determining the etiology for the low platelet count is important for the implementation of appropriate management. The use of a direct thrombin inhibitor in treatment should be considered early if a diagnosis of heparin-induced thrombocytopenia is possible.

Acute Catheterization and Urgent Intervention Triage strategY (ACUITY) trial: study design and rationale

BACKGROUND

Patients with acute coronary syndromes (ACS; unstable angina and non-ST-segment elevation myocardial infarction) are at significant risk for death and myocardial infarction. Early angiography followed by revascularization is considered the treatment of choice for moderate- to high-risk patients with ACS. However, despite the integration of newer therapies including stents, glycoprotein IIb/IIIa inhibitors, and thienopyridines, the rate of adverse ischemic events still remains unacceptably high, and the intensive pharmacologic regimens used to stabilize the disrupted atherosclerotic plaque and support angioplasty and surgical revascularization procedures elicit a high rate of bleeding complications. Pilot trials suggest that the thrombin-specific anticoagulant bivalirudin may improve clinical outcomes in ACS.

STUDY DESIGN

In the Acute Catheterization and Urgent Intervention Triage strategY (ACUITY) trial, 13,800 patients with moderate- to high-risk ACS are being prospectively randomly assigned at up to 600 centers to unfractionated heparin or enoxaparin + IIb/IIIa inhibition, versus bivalirudin + IIb/IIIa inhibition, versus bivalirudin + provisional IIb/IIIa inhibition. All patients undergo cardiac catheterization within 72 hours, followed by percutaneous or surgical revascularization when appropriate. In a second random assignment, patients assigned to receive IIb/IIIa inhibitors are subrandomized to upstream drug initiation, versus IIb/IIIa inhibitor administration during angioplasty only. The primary study end point is the composite of death, myocardial infarction, unplanned revascularization for ischemia, and major bleeding at 30 days. Clinical follow-up will continue for 1 year.

CONCLUSIONS

The ACUITY trial is the largest study yet performed in patients with ACS undergoing an invasive strategy. In addition to evaluating the utility of bivalirudin in ACS, this study will also provide important guidance regarding the necessity for and timing of IIb/IIIa inhibitor administration.

When to Stress Over Triptans: A Markov Analysis of Cardiovascular Risk in Migraine Treatment

BACKGROUND

Migraines affect 10% of the U.S. population and the episodes are frequently associated with significant disability. Triptans, 5HT1 receptor agonists, can be highly effective in treating pain and reducing disability. However, reports of cardiac events associated with triptan ingestion have led to concerns about its use in the face of possible cardiac disease.

OBJECTIVE

Should a patient without known cardiovascular disease (CAD) and moderately severe to severe migraines undergo cardiovascular testing prior to the initiation of triptan therapy?

DESIGN

A Markov model of migraine and cardiac disease using DATA 4.0. Three strategies were compared: (1) use triptans without further evaluation (TREAT); (2) test, then treat if negative (TEST); and (3) avoid triptans (NOTRIPTAN). Triptans were prohibited if a cardiac event occurred.

DATA

Model inputs were derived from the literature and subjected to sensitivity analyses across all possible values.

TIME HORIZON

Markov cycle is 1 week.

OUTCOMES

The primary outcomes of interest were quality-adjusted life expectancy, in years (QALYs) and the impact of various cardiovascular risk levels on the preferred strategy.

RESULTS

For the base case results were TREAT 19.4 QALYs, TEST 19.2, NOTRIPTAN 19.1. When altering CAD probability: TREAT dominated from 0 to 87%, TEST 87% to 97%, and NOTRIPTAN above 97%. Results were robust during sensitivity analyses.

CONCLUSIONS

This analysis suggests that even for individuals with a relatively high risk of CAD it is not beneficial to perform cardiac testing, nor to avoid triptans. The exact level of cardiac risk at which testing should be considered is probably at or above 87%.

Integrating antithrombin and antiplatelet therapies with early invasive management for non-ST-segment elevation acute coronary syndromes

Non-ST-segment elevation acute coronary syndromes are a dramatic manifestation of coronary artery disease. Multiple clinical trials have shown that early cardiac catheterization improves clinical outcomes in patients with non-ST-segment elevation acute coronary syndromes. Many antithrombotic agents effectively manage unstable coronary syndromes and serve as adjuncts to percutaneous coronary intervention. Yet, the growing number of pharmacologic agents makes early management of non-ST-segment elevation acute coronary syndromes increasingly complex. We review the current evidence regarding the optimal integration of early antithrombotic and antiplatelet therapies with early coronary angiography and subsequent revascularization.

Revised guidelines for the management of non-ST-segment elevation acute coronary syndromes

Unstable angina (UA) and non-ST-segment elevation myocardial infarction (NSTEMI) refer to a spectrum of acute severe cardiac disorders characterized by myocardial oxygen demand and supply mismatch, caused by atherosclerotic coronary artery disease. Patients presenting with acute coronary syndromes represent a major medical problem, accounting for 2.5 million hospitalizations and 500000 deaths annually in the United States alone. Of these, 1.5 million have a final diagnosis of UA, and myocardial infarction (ST-segment and non-ST-segment elevation) accounts for the remaining 1 million. The management of UA/NSTEMI presents a challenge to the cardiologist because treatment strategies continue to evolve. A number of trials have now assessed the safety and efficacy of early revascularization strategies in the treatment of patients with UA/NSTEMI, whereas others have focused on pharmacologic adjunctive therapy. An optimal single strategy encompassing most patients' needs is not clear. This review focuses on the revised American College of Cardiology/American Heart Association guidelines for the management of patients presenting with UA/NSTEMI.

Evolving role of bivalirudin in percutaneous coronary interventions; impact of the REPLACE-2 study

Percutaneous coronary interventions are being used with increasing frequency nowadays for the treatment of patients with coronary heart disease. Acute thrombotic complications remain one of the major limitations of these procedures for which unfractionated heparin has been the standard foundation anticoagulant. It has, however, many limitations and disadvantages that necessitated research and development of alternative anticoagulant therapies. The direct thrombin inhibitor bivalirudin has been approved as a substitute for heparin in patients undergoing angioplasty for unstable angina based on data in higher-risk patients where bivalirudin resulted in lower rates of ischaemic and bleeding complications compared to heparin. This evidence was collected prior to the widespread use of platelet glycoprotein (GP) IIb/IIIa receptor blockers, thienopyridines and intracoronary stents, considered standard practice for such patients today. The REPLACE-2 study was carried out to establish whether, in the current era, bivalirudin used with provisional GP IIb/IIIa blockade if necessary during the procedure could provide equivalent protection from ischaemic events compared with the gold standard of heparin plus routine GP IIb/IIIa blockade. With advantages with regards to bleeding, ease of use and reduced cost, bivalirudin use with provisional GP IIb/IIIa inhibitors in low-to-moderate risk percutaneous coronary interventions allows GP IIb/IIIa receptor antagonists to be used in a selective fashion, rather than in all patients. In this article, background rationale for bivalirudin use in this setting is reviewed as well as past research in this area. Additionally, the implications of the REPLACE-2 study in establishing where bivalirudin fits into our current interventional cardiology practice and future directions are presented.

Bivalirudin: a direct thrombin inhibitor for percutaneous transluminal coronary angioplasty

The treatment of patients with acute coronary syndromes has changed dramatically over the last several years. Most patients now undergo some form of percutaneous coronary intervention (PCI), which includes either stent placement or percutaneous transluminal coronary angioplasty (PTCA). Along with new medical interventions for acute coronary syndromes comes the need for new antithrombotic therapies. Combination therapy with antiplatelet agents (aspirin, adenosine diphosphate inhibitors), glycoprotein (GP) IIb-IIIa receptor inhibitors, and anticoagulants (unfractionated heparin or low-molecular-weight heparins) is administered, depending on the type of intervention and severity of the coronary lesion. Bivalirudin is a direct thrombin inhibitor that recently was approved as an alternative to heparin in patients undergoing PTCA. Compared with unfractionated heparin, bivalirudin reduces the rate of death, myocardial infarction, or revascularization, with a concurrent reduction in bleeding. This agent offers promise as a replacement for unfractionated heparin in PCI and is being studied in comparison with unfractionated heparin plus GP IIb-IIIa receptor inhibitors in patients undergoing intracoronary stent placement.

Bivalirudin: a review of its potential place in the management of acute coronary syndromes

Bivalirudin, a synthetic analogue of hirudin, is a specific and reversible inhibitor of thrombin which binds directly with both fluid-phase and clot-bound thrombin. In patients with unstable angina undergoing percutaneous transluminal coronary angioplasty (PTCA), results from a large well designed study and its reanalysis (n = 4312) indicate that bivalirudin is more effective than heparin in the prevention of ischaemic complications for up to 90 days after the start of treatment. In addition, among patients undergoing PTCA for post myocardial infarction (MI) bivalirudin may be more effective than heparin in preventing ischaemic complications for up to 180 days after treatment was started. Data from dose-finding studies indicate bivalirudin has potential in the treatment of patients with unstable angina not undergoing percutaneous coronary intervention (PCI); however, well designed comparative studies are needed before firm conclusions can be made. Among patients with acute ST elevation MI, randomised trials have demonstrated bivalirudin to be significantly more effective than heparin in improving early patency in patients receiving thrombolytic therapy with streptokinase. Data from the Hirulog and Early Reperfusion/Occlusion (HERO)-1 trial (n = 412) indicate that bivalirudin recipients were significantly more likely to have Thrombin Inhibition in Myocardial Ischaemia (TIMI) grade 3 flow at 90 to 120 minutes than heparin recipients. In addition, data from the HERO-2 trial (n = 17 073) show bivalirudin was significantly more effective than heparin in reducing adjudicated 96-hour reinfarction and 30-day investigator-reported death/reinfarction than heparin. Bivalirudin was as effective as heparin in reducing 30-day mortality. Data from a meta-analysis of four randomised trials among patients undergoing PTCA or treatment for acute coronary syndromes indicate that, at after 30 to 50 days of follow-up, bivalirudin was significantly more effective than heparin in reducing the incidence of nonfatal MI and the combined endpoint of death or nonfatal MI. The most significant adverse events associated with bivalirudin are bleeding complications. In individual trials, bivalirudin was as well tolerated as heparin with, in general, a reduced incidence of bleeding complications. Additionally, bivalirudin provides a more consistent, predictable anticoagulant response. In 4312 patients with unstable angina undergoing PTCA the incidence of retroperitoneal bleeding, blood transfusion and major haemorrhage was significantly lower in bivalirudin than heparin recipients. Data from the HERO-2 trial in patients with acute MI indicate that although bivalirudin recipients had a significantly higher incidence of mild or moderate bleeding than heparin recipients, there was no difference in intracranial haemorrhage, severe bleeding or transfusions. Data from a meta-analysis among 5674 patients with ischaemic heart disease show bivalirudin recipients were at a significantly lower risk of haemorrhagic events than heparin recipients.

CONCLUSIONS

Bivalirudin is an effective alternative to heparin in the prevention of ischaemic complications in patients with unstable angina undergoing PTCA. In addition, the drug has shown potential in the treatment of patients with unstable angina not undergoing PCI. For patients with MI, it is clear that bivalirudin can replace heparin in the management of MI where streptokinase is used as the thrombolytic agent. Further data are required on the efficacy of bivalirudin in patients undergoing thrombolysis with newer thrombolytics.

Clinical pharmacology of bivalirudin

Much progress has been made in understanding and treating acute coronary syndromes. For patients undergoing percutaneous transluminal coronary angioplasty, anticoagulant therapy during the procedure must strike a balance between providing sufficient anticoagulation to prevent thrombus formation and ischemic complications while averting hemorrhagic complications. Bivalirudin, a thrombin-specific anticoagulant, is the only anticoagulant that reduces both ischemic and bleeding complications associated with percutaneous coronary intervention (PCI). Bivalirudin is easy to use, provides predictable anticoagulation, inactivates both free and clot-bound thrombin, and blocks thrombin-mediated platelet activation and aggregation. Drug-drug interaction studies have found no clinically relevant interactions between bivalirudin and ticlopidine, abciximab, tirofiban, or eptifibatide. Bivalirudin is well tolerated by patients who previously received low-molecular-weight heparin (LMWH), when LMWH is discontinued 8-14 hours before bivalirudin is started. Similarly, switching from heparin to bivalirudin at the time of PCI reduces both ischemic and bleeding events.

Bivalirudin: an anticoagulant for acute coronary syndromes and coronary interventions

Heparin is a commonly used anticoagulant in patients with coronary artery disease but its use does not always result in low rates of ischaemic and bleeding events, so the search for new anticoagulants continues. Thrombin plays a key role in both thrombosis and haemostasis and direct thrombin inhibitors modelled on the hirudin molecule found in the saliva of the medicinal leech, Hirudo medicinalis, have recently been developed. To date, the only direct thrombin inhibitor shown to reduce both the ischaemic and the bleeding complications associated with percutaneous coronary intervention (PCI) is bivalirudin, which is approved for this indication in the US and New Zealand. This agent is currently being studied in patients undergoing PCI with or without glycoprotein IIb/IIIa inhibitors and stenting. Bivalirudin has been shown to significantly reduce the risk of reinfarction in patients with acute myocardial infarction (MI) treated with streptokinase, but its use for this indication is not approved in the US. It may also prove to be beneficial in patients with acute MI treated with other fibrinolytic regimens or with primary or facilitated PCI. Bivalirudin is suitable for use as an alternative to heparin in the majority of patients undergoing PCI and in patients receiving streptokinase for acute MI.

Bivalirudin for percutaneous coronary intervention and in acute coronary syndromes

This review focuses on the use of bivalirudin as a replacement anticoagulant for heparin in patients undergoing percutaneous coronary intervention, or who are being treated for unstable angina pectoris, ST-elevation, or non-ST-elevation myocardial infarction. Potential advantages of bivalirudin include a lack of dependence on antithrombin III for anticoagulant activity, the ability to inactivate both fibrin-bound and soluble thrombin, a lack of aggregatory effects on platelets, a predictable anticoagulant response without monitoring, and a wider therapeutic window. Clinical trial results to date suggest that bivlirudin is at least as effective as heparin with superior safety due to lower bleeding rates.