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      Bivalirudin in percutaneous coronary intervention

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          Abstract

          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.

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          Most cited references37

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          AN ENZYME CASCADE IN THE BLOOD CLOTTING MECHANISM, AND ITS FUNCTION AS A BIOCHEMICAL AMPLIFIER.

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            Bivalirudin and provisional glycoprotein IIb/IIIa blockade compared with heparin and planned glycoprotein IIb/IIIa blockade during percutaneous coronary intervention: REPLACE-2 randomized trial.

            The direct thrombin inhibitor bivalirudin has been associated with better efficacy and less bleeding than heparin during coronary balloon angioplasty but has not been widely tested during contemporary percutaneous coronary intervention (PCI). To determine the efficacy of bivalirudin, with glycoprotein IIb/IIIa (Gp IIb/IIIa) inhibition on a provisional basis for complications during PCI, compared with heparin plus planned Gp IIb/IIIa blockade with regard to protection from periprocedural ischemic and hemorrhagic complications. The Randomized Evaluation in PCI Linking Angiomax to Reduced Clinical Events (REPLACE)-2 trial, a randomized, double-blind, active-controlled trial conducted among 6010 patients undergoing urgent or elective PCI at 233 community or referral hospitals in 9 countries from October 2001 through August 2002. Patients were randomly assigned to receive intravenous bivalirudin (0.75-mg/kg bolus plus 1.75 mg/kg per hour for the duration of PCI), with provisional Gp IIb/IIIa inhibition (n = 2999), or heparin (65-U/kg bolus) with planned Gp IIb/IIIa inhibition (abciximab or eptifibatide) (n = 3011). Both groups received daily aspirin and a thienopyridine for at least 30 days after PCI. The primary composite end point was 30-day incidence of death, myocardial infarction, urgent repeat revascularization, or in-hospital major bleeding; the secondary composite end point was 30-day incidence of death, myocardial infarction, or urgent repeat revascularization. Provisional Gp IIb/IIIa blockade was administered to 7.2% of patients in the bivalirudin group. By 30 days, the primary composite end point had occurred among 9.2% of patients in the bivalirudin group vs 10.0% of patients in the heparin-plus-Gp IIb/IIIa group (odds ratio, 0.92; 95% confidence interval, 0.77-1.09; P =.32). The secondary composite end point occurred in 7.6% of patients in the bivalirudin vs 7.1% of patients in the heparin-plus-Gp IIb/IIIa groups (odds ratio, 1.09; 95% confidence interval 0.90-1.32; P =.40). Prespecified statistical criteria for noninferiority to heparin plus Gp IIb/IIIa were satisfied for both end points. In-hospital major bleeding rates were significantly reduced by bivalirudin (2.4% vs 4.1%; P<.001). Bivalirudin with provisional Gp IIb/IIIa blockade is statistically not inferior to heparin plus planned Gp IIb/IIIa blockade during contemporary PCI with regard to suppression of acute ischemic end points and is associated with less bleeding.
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              Binding of thrombin to glycoprotein Ib accelerates the hydrolysis of Par-1 on intact platelets.

              The activation of human platelets by alpha-thrombin is mediated at least in part by cleavage of protease-activated G-protein-coupled receptors, PAR-1 and PAR-4. Platelet glycoprotein Ibalpha also has a high affinity binding site for alpha-thrombin, and this interaction contributes to platelet activation through a still unknown mechanism. In the present study the hypothesis that GpIbalpha may contribute to platelet activation by modulating the hydrolysis of PAR-1 on the platelet membrane was investigated. Gel-filtered platelets from normal individuals were stimulated by alpha-thrombin, and the kinetics of PAR-1 hydrolysis by enzyme was followed with flow cytometry using an anti-PAR-1 monoclonal antibody (SPAN 12) that recognizes only intact PAR-1 molecules. This strategy allowed measurement of the apparent k(cat)/K(m) value for thrombin hydrolysis of PAR-1 on intact platelets, which was equal to 1.5 +/- 0.1 x 10(7) m(-1) sec(-1). The hydrolysis rate of PAR-1 by thrombin was measured under conditions in which thrombin binding to GpIb was inhibited by different strategies, with the following results. 1) Elimination of GpIbalpha on platelet membranes by mocarhagin treatment reduced the k(cat)/K(m) value by about 6-fold. 2) A monoclonal anti-GpIb antibody reduced the apparent k(cat)/K(m) value by about 5-fold. 3) An oligonucleotide DNA aptamer, HD22, which binds to the thrombin heparin-binding site (HBS) and inhibits thrombin interaction with GpIbalpha, reduced the apparent k(cat)/K(m) value by about 5-fold. 4) Displacement of alpha-thrombin from the binding site on GpIb using PPACK-thrombin reduced the apparent k(cat)/K(m) value by about 5-fold, and 5) mutation at the HBS of thrombin (R98A) caused a 5-fold reduction of the apparent k(cat)/K(m) value of PAR-1 hydrolysis. Altogether these results show that thrombin interaction with GpIb enhances the specificity of thrombin cleavage of PAR-1 on intact platelets, suggesting that GpIb may function as a "cofactor" for PAR-1 activation by thrombin.
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                Author and article information

                Journal
                Vasc Health Risk Manag
                Vascular Health and Risk Management
                Vascular Health and Risk Management
                Dove Medical Press
                1176-6344
                1178-2048
                December 2006
                December 2006
                : 2
                : 4
                : 357-363
                Affiliations
                Department of Medicine, Flinders University South Australia, Australia
                Author notes
                Correspondence: Derek P Chew Department of Cardiology, Flinders Medical Centre, Bedford Drive, South Australia Tel + 61 8 8204 5619 Fax + 61 8 8204 5625 Email derek.chew@ 123456flinders.edu.au
                Article
                10.2147/vhrm.2006.2.4.357
                1994003
                17323589
                79da89d7-6d35-46a2-85f9-36961c1df3b9
                © 2006 Dove Medical Press Limited. All rights reserved
                History
                Categories
                Review

                Cardiovascular Medicine
                bivalirudin,direct thrombin inhibitor,percutaneous coronary intervention,acute coronary syndrome

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