Direct thrombin inhibitors in cardiac disease

Most acute coronary syndromes (ACS) are triggered by platelet-rich thrombus superimposed on disrupted atherosclerotic plaque. Thrombin and platelets both play a role in this process. Whereas unfractionated heparin and aspirin have served as cornerstones in the treatment of ACS, several limitations of heparin provide the impetus to seek out better anticoagulants. Direct thrombin inhibitors such as bivalirudin, hirudin, and argatroban offer several pharmacologic advantages over heparin. Additionally, bivalirudin also appears to provide clinical advantages over unfractionated heparin therapy in ACS patients and those undergoing percutaneous coronary intervention.     

Bivalirudin in Percutaneous Coronary Intervention,is it the Anticoagulant of Choice?

For decades, unfractionated heparin (UFH) has been widely used in catheterization laboratories for anticoagulation for percutaneous coronary intervention (PCI). The direct thrombin inhibitors, bivalirudin, has emerged as an alternative to UFH for PCI procedures, due to its lower bleeding risk. More recently, randomized trials and meta‐analyses questioned the efficacy of bivalirudin, and demonstrated that bivalirudin might be associated with a higher incidence of ischemic events and in particular stent thrombosis. In this review, we discuss the pharmacology of bivalirudin along with the clinical evidence comparing bivalirudin versus UFH in patients undergoing PCI for various indications.     

Use of Prolonged Bivalirudin Infusions Following Percutaneous Coronary Intervention

Introduction  

Antithrombotic therapy plays an integral role in percutaneous coronary intervention (PCI). Bivalirudin has been evaluated in elective procedures and across the spectrum of acute coronary syndromes and is associated with decreased bleeding events compared to unfractionated heparin (UFH) in combination with glycoprotein IIb/IIIa inhibitors (GPI) when used for the duration of PCI. The use of bivalirudin beyond the end of PCI is not as well established but is being explored as an option for specific patients.     

Direct thrombin inhibitors

Direct thrombin inhibitors (DTIs) are a new class of therapeutics possessing theoretic advantages over unfractionated heparin (UFH). In contrast to UFH, DTIs do not activate platelets, have no circulating inhibitors, and bind to both free and clot-bound thrombin. These theoretical advantages have spurred clinical trials investigating DTIs in a variety of cardiovascular indications. Currently, the major role for DTIs in cardiology is as an adjunct during percutaneous coronary intervention (PCI). Such a role stems from the results of the Randomized Evaluation in PCI Linking Angiomax to Reduced Clinical Events (REPLACE)-2 randomized trial, in which bivalirudin with provisional abciximab was demonstrated to be equivalent to UFH plus planned abciximab with respect to ischemic endpoints, while being associated with less bleeding. Ongoing clinical trials will define the role of bivalirudin as an adjunct to primary PCI for ST-segment elevation myocardial infarction and in non-ST segment elevation acute coronary syndrome as an adjunct to an early invasive strategy.     

Anticoagulation strategies for patients undergoing percutaneous coronary intervention: unfractionated heparin, low-molecular-weight heparins, and direct thrombin inhibitors

Low-molecular-weight heparins and direct thrombin inhibitors are emerging as alternative anticoagulants to unfractionated heparin in patients undergoing percutaneous coronary intervention (PCI). This paper reviews the pharmacologic properties of these newer antithrombotic agents and evaluates the clinical data demonstrating their use in patients undergoing PCI.     

Intracoronary macrothrombus formation during percutaneous coronary intervention despite optimal activated clotting time using bivalirudin--a case report

The occurrence of intracoronary thrombus during percutaneous coronary intervention (PCI) is a well-known complication. It has been estimated that it complicates approximately 6% of all coronary procedures. Patients at highest risk for this complication include those with acute ischemic syndromes or with angiographically apparent thrombus. Since the development of PCI, intravenous unfractionated heparin (UFH) has remained the primary antithrombotic therapy for the prevention of periprocedural ischemic complications. The availability of a rapid "point of care' test for dose individualization (the activated clotting time [ACT]) has facilitated this process. Other forms of antithrombotic therapies such as direct thrombin inhibitors or low-molecular-weight heparin have been proposed as more effective anticoagulants during PCI. Bivalirudin is a direct thrombin inhibitor proven to decrease post-PCI ischemic complication rate compared with UFH and have a lower vascular complication rate compared with glycoprotein IIb/IIIa receptor antagonists. We herein report a case of acute macrothrombus formation during PCI despite adequate ACT achieved with bivalirudin.     

Clinician Update: Direct Thrombin Inhibitors in Acute Coronary Syndromes

Antithrombotic therapy has become the cornerstone of the treatment for atherosclerotic cardiovascular disease. Unfractionated heparin (UFH) has been the thrombin inhibitor of choice for decades. UFH, however, has its deficiencies. To overcome these problems several direct thrombin inhibitors (DTIs) have been developed. These agents are capable of inactivating clot-bound thrombin more efficiently, and provide more predictable and safer anticoagulation in patients with of acute coronary syndromes (ACS). The initial studies of hirudin and bivalirudin in the clinical settings of acute myocardial infarction (AMI), unstable angina (UA) and percutaneous coronary interventions (PCI) conducted in the early 1990s proved to be disappointing. As the knowledge of more appropriate use of these drugs progressed, there is a renewed interest in DTIs. Herein we will review the clinical studies assessing hirudin, bivalirudin and argatroban in the settings of AMI, UA and PCI.     

Adjunctive pharmacologic therapy in percutaneous coronary intervention: part II anticoagulant therapy

Pharmacological adjuvant therapies to protect against procedure-related thrombotic complication are indispensable during percutaneous coronary intervention. In addition to antiplatelet therapy, use of anticoagulants to prevent acute thrombotic complication during percutaneous coronary intervention is essential. Besides unfractionated heparin (UFH), new anticoagulants have been developed and compared with UFH. Low-molecular weight heparins, direct thrombin inhibitors (e.g. bivalirudin), and recently developed agents such as fondaparinux (a factor Xa inhibitor) provide new alternatives to conventional UFH.     

Plättchenhemmung und Antikoagulation beim akuten Koronarsyndrom

In recent years, the prognosis of patients with an acute coronary syndrome (ACS) has significantly improved. This can mainly be attributed to the implementation of primary percutaneous coronary intervention (PCI). Apart from mechanical reperfusion, an optimal medical strategy is of great importance. Antiplatelet and antithrombotic therapies in particular play a crucial role in the management of patients with ACS. New options in antiplatelet therapy are more potent P2Y₁₂ inhibitors in addition to acetylsalicylic acid and clopidogrel. Furthermore, anticoagulant therapy before, during and after PCI can be performed by the use of unfractionated heparin, low molecular weight heparins, such as enoxaparin, the synthetic pentasaccharide fondaparinux and the direct thrombin inhibitor bivalirudin with or without additional administration of glycoprotein IIb/IIIa inhibitors. In this article, data on antiplatelet and anticoagulant therapy are presented and the current evidence is discussed.     

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 hemor‐rhagic 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.     

国产比伐卢定在老年急性冠脉综合征患者介入术中治疗效果

目的 研究老年（年龄>65岁）急性冠脉综合征（ACS）患者在经皮冠脉介入（PCI）治疗术中使用国产比伐卢定的安全和有效性。方法 本研究通过回顾性分析我院35例PCI术中应用比伐卢定的老年ACS患者的临床资料,按1∶1匹配选取同期35例PCI治疗过程中常规应用普通肝素的老年ACS患者作为对照组,分析术后30 d内的主要不良心脑血管事件(major adverse cardiac and cerebrovascular events,MACCE)及出血并发症的发生情况。结果 两组临床资料对比,差异无统计学意义。术后30 d内MACCE发生率分别为4例（11%）和5例（14%）,差异无统计学意义;出血并发症发生率分别为1例（3%）和6例（17%）,比伐卢定组优于普通肝素组（P<0.05）。结论 老年ACS患者PCI术中使用比伐卢定与普通肝素相比,可减少术后30d内的出血事件发生率,且不增加MACCE的风险。     

Comparison of bivalirudin versus heparin plus glycoprotein IIb/IIIa inhibitors in patients undergoing an invasive strategy: A meta-analysis of randomized clinical trials

Objective

This meta-analysis was performed to assess the efficacy and safety of bivalirudin compared with unfractionated heparin or enoxaparin plus glycoprotein (GP) IIb/IIIa inhibitors in patients undergoing percutaneous coronary intervention (PCI).

Background

Pharmacotherapy for patients undergoing PCI includes bivalirudin, heparin, and GP IIb/IIIa inhibitors. We sought to compare ischemic and bleeding outcomes with bivalirudin versus heparin plus GP IIb/IIIa inhibitors in patients undergoing PCI.

Methods

A literature search was conducted to identify fully published randomized trials that compared bivalirudin with heparin plus GP IIb/IIIa inhibitors in patients undergoing PCI.

Results

A total of 19,772 patients in 5 clinical trials were included in the analysis (9785 patients received bivalirudin and 9987 patients received heparin plus GP IIb/IIIa inhibitors during PCI). Anticoagulation with bivalirudin, as compared with heparin plus glycoprotein IIb/IIIa inhibitors, results in no difference in major adverse cardiovascular events (odds ratio [OR] 1.07, 95% confidence interval [CI] 0.96 to 1.19), death (OR 0.93, 95% CI 0.72 to 1.21), or urgent revascularization (OR 1.06, 95% CI 0.86 to 1.30). There is a trend towards a higher risk of myocardial infarction (OR 1.12, 95% CI 0.99 to 1.28) but a significantly lower risk of TIMI major bleeding with bivalirudin (OR 0.55, 95% CI 0.44 to 0.69).

Conclusion

In patients who undergo PCI, anticoagulation with bivalirudin as compared with unfractionated heparin or enoxaparin plus GP IIb/IIIa inhibitors results in similar ischemic adverse events but a reduction in major bleeding.     

The effects of bivalirudin compared with those of unfractionated heparin plus eptifibatide on inflammation and thrombin generation and activity during coronary intervention

OBJECTIVE: To characterize effects of bivalirudin compared with unfractionated heparin plus eptifibatide on inflammation, and thrombin generation and activity after percutaneous coronary intervention. METHODS: We measured the concentration in blood of fibrinopeptide A, prothrombin fragment 1+2, soluble CD40 ligand, interleukin 1 receptor antagonist, interleukin 6, and high sensitivity C-reactive protein in 63 patients treated with aspirin and clopidogrel and undergoing elective percutaneous coronary intervention, who were randomized to treatment with either bivalirudin (n=34) or unfractionated heparin plus eptifibatide (n=29). RESULTS: Neither generation nor activity of thrombin increased 10 min after percutaneous coronary intervention in patients randomized to bivalirudin or unfractionated heparin plus eptifibatide. However, prothrombin fragment 1+2 increased modestly and comparably in both groups after 1 day. Inflammation, reflected by concentrations of interleukin 6 and high sensitivity C-reactive protein in blood, increased similarly 1 day after percutaneous coronary intervention in patients treated with either regimen. In a subset of patients (n=12 in each group) from whom blood was obtained 30 days after percutaneous coronary intervention, the concentration of high sensitivity C-reactive protein was lower in those who had been treated with bivalirudin (by 3.5 mg/l, P=0.002). CONCLUSION: The early effects on inflammation and thrombin generation and activity are similar after treatment with bivalirudin alone compared with unfractionated heparin plus eptifibatide in patients treated with aspirin and clopidogrel who are undergoing percutaneous coronary intervention for symptoms of stable angina. The decreased concentration of high sensitivity C-reactive protein seen 30 days after percutaneous coronary intervention in those treated with bivalirudin is consistent with greater attenuation of inflammation that may have contributed to the trend toward reduced mortality 1 year later in those treated with bivalirudin in REPLACE-2.     

What anti‐thrombotic therapy is best with primary PCI for acute ST elevation myocardial infarction: How should the HORIZONS trial change current practice?

The current standard of care for anti‐thrombotic therapy with primary PCI for acute ST elevation myocardial infarction (STEMI) is aspirin, clopidogrel, unfractionated heparin and platelet glycoprotein IIb/IIIa inhibitors. However, heparin and glycoprotein IIb/IIIa inhibitors are associated with a high incidence of bleeding, and many of the trials documenting benefit with this therapy were performed before the widespread use of stents and clopidogrel. Bivalirudin is a direct thrombin inhibitor which has been found to have similar efficacy with less bleeding compared with heparin plus glycoprotein IIb/IIIa inhibitors when used with elective PCI and with PCI for unstable angina and non‐ST elevation myocardial infarction. The HORIZONS trial evaluated bivalirudin compared with unfractionated heparin and IIb/IIIa inhibitors in patients with STEMI treated with primary PCI and found similar MACE (major adverse cardiac events) with less bleeding and a lower incidence of net adverse clinical events (MACE or major bleeding) at 30 days. Mortality at 30 days was also significantly less with bivalirudin. These results make a strong case for the use of bivalirudin with primary PCI in the great majority of patients with STEMI, with the possible exception of patients with cardiogenic shock or stent thrombosis, and patients with a large thrombus burden or no re‐flow following PCI. In the latter case, platelet glycoprotein IIb/IIIa inhibitors would be used as a bail‐out strategy. © 2008 Wiley‐Liss, Inc.     

Bivalirudin Inhibits Periprocedural Platelet Function and Tissue Factor Expression of Human Smooth Muscle Cells

Aim: A major concern of stent implantation after percutaneous coronary intervention (PCI) is acute stent thrombosis. Effective inhibition of periprocedural platelet function in patients with coronary artery disease (CAD) leads to an improved outcome. In this study, we examined the periprocedural platelet reactivity after administrating bivalirudin during PCI compared to unfractionated heparin (UFH) administration. Further, the effect of bivalirudin on induced tissue factor (TF) expression in smooth muscle cells (SMC) was determined. Methods: Patients with CAD (n = 58) and double antithrombotic medication were treated intraprocedural with UFH (n = 30) or bivalirudin (n = 28). Platelet activation markers were flow cytometrically measured before and after stenting. The expression of TF in SMC was determined by real‐time PCR and Western blotting. The thrombogenicity of platelet‐derived microparticles and SMC was assessed via a TF activity assay. Results: Bivalirudin significantly diminished the agonist‐induced platelet reactivity post‐PCI. Compared to UFH treatment, the adenosine diphosphate (ADP) and thrombin receptor‐activating peptide (TRAP)‐induced thrombospondin expression post‐PCI was reduced when bivalirudin was administrated during intervention. In contrast to UFH, bivalirudin reduced the P‐selectin expression of unstimulated and ADP‐induced platelets post‐PCI. Moreover, bivalirudin inhibited the thrombin‐, but not FVIIa‐ or FVIIa/FX‐induced TF expression and pro‐coagulant TF activity of SMC. Moreover, bivalirudin reduced the TF activity of platelet‐derived microparticles postinduction with TRAP or ADP. Conclusions: Bivalirudin is better than UFH in reducing periprocedural platelet activation. Moreover, thrombin‐induced TF expression is inhibited by bivalirudin. Thus, bivalirudin seems to be a better anticoagulant during PCI than UFH.     

Comparison of Prasugrel and Bivalirudin vs Clopidogrel and Heparin in Patients With ST‐Segment Elevation Myocardial Infarction: Design and Rationale of the Bavarian Reperfusion Alternatives Evaluation (BRAVE) 4 Trial

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for patients with ST‐segment elevation myocardial infarction (STEMI). Effective and safe adjunct antithrombotic therapy is a major determinant for short‐ and long‐term outcomes after primary PCI. Two separate studies have shown significant benefits vs conventional therapy for 2 recently approved drugs. In the Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction (HORIZONS‐AMI) trial, bivalirudin after pretreatment with clopidogrel resulted in improved net clinical outcome compared with heparin plus glycoprotein IIb/IIIa inhibitors. However, during the first 24 hours after PCI, there was an increase in stent thrombosis rates with bivalirudin. In the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel—Thrombolysis In Myocardial Infarction (TRITON‐TIMI) 38 trial, prasugrel was superior to clopidogrel in patients with acute coronary syndrome with and without ST‐segment elevation. The synergic actions of prasugrel and bivalirudin may maximize the benefit of antithrombotic therapy for STEMI patients undergoing primary PCI. However, no specifically designed studies have so far compared the combination of prasugrel plus bivalirudin with that of clopidogrel plus unfractionated heparin in these patients. The Bavarian Reperfusion Alternatives Evaluation (BRAVE) 4 study is a randomized, open‐label, multicenter trial aimed to test the hypothesis that a strategy based on prasugrel plus bivalirudin is superior to a strategy based on clopidogrel plus unfractionated heparin in terms of net clinical outcome in STEMI patients with planned primary PCI.     

Percutaneous interventions in patients with immune-mediated heparin-induced thrombocytopenia

The use of unfractionated heparin, the traditional antithrombotic agent during percutaneous coronary interventions (PCI), is associated with the risk of heparin-induced thrombocytopenia, a rare but often fatal clinical condition. This article focuses on several issues related to heparin-induced immune-mediated thrombocytopenia (HIT, type II) and alternative modes of periprocedural anticoagulation in patients with suspected or known HIT. The hypercoagulable state characterizing HIT, along with mechanical plaque disruption resulting from PCI place patients with HIT at particular risk of thrombosis during PCI. Given that a diagnosis of HIT precludes any further use of heparin, other treatment modalities are essential. Direct thrombin inhibitors are the drugs of choice in this challenging situation. These agents offer several advantages as anticoagulants for patients with HIT: (1) the ability to inhibit both thrombin that is bound to fibrin (clot-bound thrombin) and fluid-phase free thrombin; (2) rapid achievement of steady state; and (3) no cross-reactivity with HIT antibodies. Recent data on the use of bivalirudin, lepirudin, and argatroban in the setting of PCI in patients with HIT are encouraging. Optimal dosing regimens for argatroban, lepirudin, and bivalirudin should be further established in PCI patients.     

国产比伐卢定在急诊介入治疗中对血小板功能的影响

目的：探讨国产比伐卢定在急诊经皮冠状动脉介入治疗（PCI）中对血小板功能的影响。方法：100例急性ST段抬高性心肌梗死接受急诊PCI的患者随机分为肝素组（53例）和比伐卢定组（47例）。检测两组 PCI术前后二磷酸腺苷（ADP）诱导的血小板聚集率,并进行统计学比较。结果：急诊PCI术前,两组 ADP诱导的血小板凝聚率差异无统计学意义（ P＝0.99）。急诊 PCI术后,比伐卢定组 ADP 诱导的血小板凝聚率显著低于肝素组[（16.46±10.23）％比（25.21±15.91）％, P＜0.01]。结论：PCI术中,与常规肝素抗凝相比,作为抗凝剂的比伐卢定可以更明显抑制血小板凝聚,具有抗血小板的功能。     

A randomized trial to evaluate the relative protection against post-percutaneous coronary intervention microvascular dysfunction, ischemia, and inflammation among antiplatelet and antithrombotic agents: the PROTECT-TIMI-30 trial.

OBJECTIVES: The goal of this study was to evaluate glycoprotein IIb/IIIa inhibition with eptifibatide when administered with indirect thrombin inhibition as compared with monotherapy with direct thrombin inhibition with bivalirudin among patients with non-ST-segment elevation acute coronary syndromes (ACS). BACKGROUND: The optimal combination of antiplatelet and antithrombin regimens that maximizes efficacy and minimizes bleeding among patients with non-ST-segment elevation ACS undergoing percutaneous coronary intervention (PCI) is unclear. METHODS: A total of 857 patients with non-ST-segment elevation ACS were assigned randomly to eptifibatide + reduced dose unfractionated heparin (n = 298), eptifibatide + reduced-dose enoxaparin (n = 275), or bivalirudin monotherapy (n = 284). RESULTS: Among angiographically evaluable patients (n = 754), the primary end point of post-PCI coronary flow reserve was significantly greater with bivalirudin (1.43 vs. 1.33 for pooled eptifibatide arms, p = 0.036). Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade more often was normal with eptifibatide treatment compared with bivalirudin (57.9% vs. 50.9%, p = 0.048). The duration of ischemia on continuous Holter monitoring after PCI was significantly longer among patients treated with bivalirudin (169 vs. 36 min, p = 0.013). There was no excess of TIMI major bleeding among patients treated with eptifibatide compared with bivalirudin (0.7%, n = 4 vs. 0%, p = NS), but TIMI minor bleeding was increased (2.5% vs. 0.4%, p = 0.027) as was transfusion (4.4% to 0.4%, p < 0.001). CONCLUSIONS: Among moderate- to high-risk patients with ACS undergoing PCI, coronary flow reserve was greater with bivalirudin than eptifibatide. Eptifibatide improved myocardial perfusion and reduced the duration of post-PCI ischemia but was associated with higher minor bleeding and transfusion rates. Ischemic events and biomarkers for myonecrosis, inflammation, and thrombin generation did not differ between agents.     

Angiographic and clinical outcomes of bivalirudin versus heparin in patients with acute coronary syndrome undergoing percutaneous coronary intervention

BACKGROUND: Heparin with adjunctive glycoprotein IIb/IIIa platelet receptor (GP IIb/IIIa) inhibitors has demonstrated its effectiveness in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI). Bivalirudin, a direct thrombin inhibitor, has recently been shown to be an effective alternative for patients undergoing elective PCI. OBJECTIVES: To assess the angiographic and clinical outcomes of adjunctive pharmacological strategies in a high-risk population presenting with ACS. METHODS: Of 891 consecutive PCI patients with ACS, 304 received bivalirudin (60.5% male, 68+/-11 years) and were compared with 283 who received heparin (58.7% male, 66+/-12 years). A 30-day major adverse cardiac event was defined as the occurrence of cardiac death, nonfatal myocardial infarction, urgent revascularization or major hemorrhage. RESULTS: Adjunctive GP IIb/IIIa inhibitors were used in 14.1% of the bivalirudin group and in 72.4% of the heparin group (P<0.010). The occurrence of Thrombolysis In Myocardial Infarction (TIMI) flow less than grade 3 was lower and the achievement of angiographic success was higher in the bivalirudin group than in the heparin group (5.2% versus 8.2%, 94.7% versus 89.7%, P=0.039 and P<0.010, respectively). There was no difference between groups in the incidence of bleeding events (bivalirudin 2.0% versus heparin 3.5%, P not significant) and in 30-day major adverse cardiac events (bivalirudin 8.3% versus heparin 5.7%, P=0.223). CONCLUSIONS: In the high-risk cohort undergoing PCI, bivalirudin with provisional GP IIb/IIIa inhibitors achieved better angiographic results. Although not powered to show a difference, and while acknowledging that a selection bias could have affected the data, the present study showed that bivalirudin may be as clinically effective and safe as heparin with adjunctive GP IIb/IIIa inhibitors.