ESPRIT Investigators. Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy. Novel dosing regimen of eptifibatide in planned coronary stent implantation (ESPRIT): a randomised, placebo-controlled trial

Newer agents in antiplatelet therapy: a review

Antiplatelet therapy remains the mainstay in preventing aberrant platelet activation in pathophysiological conditions such as myocardial infarction, ischemia, and stroke. Although there has been significant advancement in antiplatelet therapeutic approaches, aspirin still remains the gold standard treatment in the clinical setting. Limitations in safety, efficacy, and tolerability have precluded many of the antiplatelet inhibitors from use in patients. Unforeseen incidences of increased bleeding risk and recurrent arterial thrombosis observed in patients have hampered the development of superior next generation antiplatelet therapies. The pharmacokinetic and pharmacodynamic profiles have also limited the effectiveness of a number of antiplatelet inhibitors currently in use due to variability in metabolism, time to onset, and reversibility. A focused effort in the development of newer antiplatelet therapies to address some of these shortcomings has resulted in a significant number of potential antiplatelet drugs which target enzymes (phosphodiesterase, cyclooxygenase), receptors (purinergic, prostaglandins, protease-activated receptors, thromboxane), and glycoproteins (αIIbβ3, GPVI, vWF, GPIb) in the platelet. The validation and search for newer antiplatelet therapeutic approaches proven to be superior to aspirin is still ongoing and should yield a better pharmacodynamic profile with fewer untoward side-effects to what is currently in use today.

Novel antiplatelet therapies

Advances in antiplatelet therapy have significantly improved outcomes in patients with ischemic heart disease. Thienopyridines remain a cornerstone of therapy along with aspirin. Recently, concerns have been raised about the use of clopidogrel due to its pharmacokinetic and pharmacogenetic interpatient variability. A third-generation thienopyridine, prasugrel, overcomes some of these problems by improving inhibition of platelet aggregation, but increasing the risk of peri-procedural bleeding. Other novel antiplatelet agents, such as ticagrelor, have shown improved efficacy in recent trials and require further investigations. The field of pharmacotherapy continues to rapidly evolve as newer agents, such as thrombin receptor antagonists, along with older agents, such as cilostazol and glycoprotein IIb/IIIa inhibitors, are being explored.

Risk of bleeding after prehospital administration of high dose tirofiban for ST elevation myocardial infarction

BACKGROUND

In most patients with ST-elevation myocardial infarction (STEMI), antiplatelet drugs are already administrated in the ambulance, before hospital admission. We investigated the safety of prehospital initiation of a high dose of the glycoprotein IIb/IIIa inhibitor tirofiban on top of aspirin, clopidogrel and heparin.

METHODS

It concerns a sub-analysis of the On-TIME 2 trial. 1398 patients were enrolled and 1275 patients (91.2%) had clinical follow up. Non CABG-related bleeding was defined according to the TIMI criteria. Logistic regression was used to determine predictors of 30-day bleeding. The independent association between bleeding and mortality (30-day and 1-year) was evaluated using Cox proportional Hazard models.

RESULTS

Bleeding (major or minor) was observed in 47 patients (3.7%), with only 13 patients (1%) with major bleeding. The strongest independent determinants of bleeding were age (OR 1.05, 95% CI 1.01-1.08, p=0.011), Killip class >1 at admission (OR 2.5, 95% CI 1.2-5.3, p=0.020) and intra aortic balloon pump (IABP) use (OR 4.2, 95% CI 1.6-11.1, p=0.003). High dose tirofiban was not an independent predictor of bleeding (OR 1.7, 95% CI 0.9-3.2, p=0.116). Bleeding was associated with an increased risk of 30-day mortality (HR 5.5, 95% CI 1.6-7.8, p<0.001) and one-year mortality (HR 3.2, 95% CI 1.4-7.2, p=0.005).

CONCLUSION

Prehospital use of high dose tirofiban is safe and associated with a low risk of bleeding. Age, Killip class >1, IABP use, but not high dose tirofiban are independent determinants of bleeding in STEMI patients. Bleeding is independently associated with 30-day and 1-year mortality.

Antiplatelet drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

The article describes the mechanisms of action, pharmacokinetics, and pharmacodynamics of aspirin, dipyridamole, cilostazol, the thienopyridines, and the glycoprotein IIb/IIIa antagonists. The relationships among dose, efficacy, and safety are discussed along with a mechanistic overview of results of randomized clinical trials. The article does not provide specific management recommendations but highlights important practical aspects of antiplatelet therapy, including optimal dosing, the variable balance between benefits and risks when antiplatelet therapies are used alone or in combination with other antiplatelet drugs in different clinical settings, and the implications of persistently high platelet reactivity despite such treatment.

Safety and efficacy of antiplatelet and antithrombotic therapy in acute coronary syndrome patients with chronic kidney disease

Chronic kidney disease (CKD) is prevalent and affects an ever-increasing proportion of patients presenting with acute coronary syndrome (ACS). Patients with CKD have a higher risk of ACS and significantly higher mortality, and are also predisposed to increased bleeding complications. Antiplatelet and antithrombotic drugs form the bedrock of management of patients with ACS. Most randomized trials of these drugs exclude patients with CKD, and current guidelines for management of these patients are largely based on these trials. We aim to review the safety and efficacy of these drugs in patients with CKD presenting with ACS.

Anti-platelet therapy: glycoprotein IIb-IIIa antagonists

Glycoprotein (GP) IIb-IIIa antagonists inhibit the aggregation of activated platelets. Three agents are approved for clinical use. In this review, the characteristics of each agent, their pharmacodynamic profile, results in pivotal clinical trials and the associated clinical implications are discussed. GP IIb-IIIa antagonists have greatest benefit when used as adjunctive therapy during percutaneous coronary intervention (PCI) when the patient has intra-coronary thrombosis. These agents appear to provide greatest benefit when used in combination with heparin. The clinical niche for parenteral GP IIb-IIIa antagonists is evolving. The rapid onset and offset of GP IIb-IIIa antagonists plus dosing designed to inhibit extensively platelet aggregation differentiates them from oral agents. The contemporary niche appears to include patients in transition, such as individuals requiring emergent PCI before oral agents are fully active and for unstable patients requiring transport to PCI centres, particularly in patients likely to have intracoronary thrombus. Subsequent studies should evaluate the optimal duration of therapy with GP IIb-IIIa antagonists.

Contemporary use of glycoprotein IIb/IIIa inhibitors

Platelet glycoprotein IIb/IIIa inhibitors (GPI) are antithrombotic agents preventing the binding of fibrinogen to GP IIb/IIIa receptors. Thus, GPI interfere with interplatelet bridging mediated by fibrinogen. Currently, three generic GPI with different antithrombotic properties are available for intravenous administration: abciximab, eptifibatide, and tirofiban. The development of oral GPI was abandoned, whereas intravenous GPI were introduced in various clinical settings during the 1990s, yielding substantial benefit in the treatment of acute coronary syndromes, particularly during percutaneous coronary interventions. Results of the many randomised trials evidenced the efficacy of this drug class, though these trials were conducted prior to the emergence of modern oral antiplatelet therapy with efficient P2Y(12) inhibitors. Subsequent trials failed to consolidate the strongly favourable impression of GPI, and indications for their use have been more restricted in recent years. Nonetheless, GPI may still be beneficial during coronary interventions among high-risk patients including acute ST-elevation and non-ST-elevation myocardial infarctions, particularly in the absence of adequate pretreatment with oral antiplatelet drugs or when direct thrombin inhibitors are not utilised. Intracoronary GPI administration has been suggested as adjunctive therapy during primary percutaneous coronary intervention, and the results of larger ongoing trials are expected to elucidate its clinical potential. The present review outlines the key milestones of GPI development and provides an up-to-date overview of the clinical applicability of these drugs in the era of refined coronary stenting, potent antithrombotic drugs, and novel thrombin inhibiting agents.

Optimal use of platelet glycoprotein IIb/IIIa receptor antagonists in patients undergoing percutaneous coronary interventions

Discovery of the central role of platelets in the pathogenesis of acute coronary syndromes (ACS) and ischaemic complications of percutaneous coronary interventions (PCI) has led to the widespread use of oral and parenteral platelet inhibitors to treat these conditions. Glycoprotein (GP) IIb/IIIa (also known as α(IIb)β(3)) receptors on the surface of platelets play an essential role in platelet aggregation and serve as a key mediator in the formation of arterial thrombus. When activated, GP IIb/IIIa receptors bind to fibrinogen, which serves as the 'final common pathway' in platelet aggregation. Of the numerous agents developed for modulating platelet activity, intravenous platelet GP IIb/IIIa receptor antagonists are the most potent. There are four agents in clinical use, including abciximab, eptifibatide, tirofiban and lamifiban, although lamifiban is not approved for use in the US. While all agents block fibrinogen binding to GP IIb/IIIa, they do so by different mechanisms. Abciximab is a humanized form of a murine monoclonal antibody directed against GP IIb/IIIa, eptifibatide is a synthetic, cyclic heptapeptide that contains a lysine-glycine-aspartic acid (KGD) sequence that mimics the arginine-glycine-aspartic acid (RGD) sequence found on GP IIb/IIIa, tirofiban is a non-peptide antagonist derived by optimization of the tyrosine analogue that structurally mimicks the RGD-containing loop of the disintegrin echistatin, and lamifiban is a synthetic, non-cyclic, non-peptide, low-molecular-weight compound. In clinical trials, use of these agents reduces ischaemic adverse cardiovascular events in patients with ACS undergoing PCI, but at a cost of increased bleeding.

Tirofiban versus abciximab: tirofiban is administered at suboptimal dosages when evaluated in an arterial thrombosis model in non-human primates

To prevent thrombosis in high-risk acute coronary syndrome patients undergoing percutaneous coronary intervention for re-vascularisation, concomitant administration of a glycoprotein IIb/IIIa inhibitor, such as abciximab, tirofiban or eptifibatide, is recommended. Abciximab and eptifibatide are mostly preferred over tirofiban, which is less effective in preventing ischaemic events. We compared the efficacy and bleeding potential of escalating doses of tirofiban and abciximab in non-human primates. The efficacy of tirofiban and abciximab in inhibiting cyclic flow reductions (CFRs) was tested in a high shear arterial thrombosis model. Bleeding was evaluated with the template bleeding time and an incision bleeding model. Abciximab completely inhibited arterial thrombosis after injection of its therapeutic bolus dose. With tirofiban, a dose three times higher than the recommended therapeutic dose caused weak inhibition characterised by a return of CFRs after re-injury. At nine times the recommended therapeutic dose, complete inhibition was observed, and the efficacy of tirofiban was comparable to abciximab at its therapeutic bolus dose. Blood loss was less than with abciximab at its effective dose. In this model, tirofiban compared favourably with abciximab, although only at a dose of 3-9 times the therapeutic dose, and caused less bleeding than abciximab.

Glycoprotein IIb/IIIa antagonists

Mortality from ischemic cardiac disease in adults has been dramatically reduced by the development of novel therapies for inhibiting platelet function. Circulating platelets are maintained in a resting state and are activated at sites of vascular injury by exquisitely controlled mechanisms, thereby maintaining vascular integrity without causing intravascular thrombosis. As it became clear that platelets play a central role in arterial thrombosis, the processes of platelet activation, adhesion, and aggregation became logical targets for the development of antithrombotic agents.

The kinetics of integrilin limited by obesity: a multicenter randomized pharmacokinetic and pharmacodynamic clinical trial

BACKGROUND

KILO tested 2 novel weight-based eptifibatide dosing strategies compared with standard dosing in obese patients undergoing elective percutaneous coronary intervention (PCI). Eptifibatide dosing is weight adjusted for patients up to 121 kg. Patients above this weight receive the same maximal dose, although it is unknown if this provides adequate eptifibatide concentration or platelet inhibition.

METHODS

Sixty-seven patients weighing ≥125 kg undergoing elective PCI were randomized to 1 of 3 eptifibatide dosing regimens: standard dosing using a weight of 121 kg, actual body weight (ABW)-based dosing with no upper limit, or ideal body weight (IBW)-based dosing. Boluses of 180 μg/kg were given 10 minutes apart, followed by a 2.0 μg/kg per minute infusion. Plasma eptifibatide concentrations were drawn at 12 to 18 hours after initiating the infusion. Platelet aggregation was assessed at baseline and 10 minutes after the second bolus.

RESULTS

Sixty-seven patients were randomized to standard (n = 22), ABW (n = 23), or IBW (n = 22) dosing. The median (25th, 75th) steady-state plasma eptifibatide concentrations were 1,740 ng/mL (1,350, 2,350), 1,780 ng/mL (1,510, 2,350), and 1,055 ng/mL (738, 1,405), respectively (P < .001). Ten-minute median (25th, 75th) platelet aggregation units were 7 (0, 21), 2 (0, 8), and 14 (8, 20), respectively (P = .001).

CONCLUSIONS

Actual body weight eptifibatide dosing leads to higher plasma concentrations and greater platelet inhibition than standard or IBW dosing in obese patients undergoing PCI. Current recommendations for eptifibatide dosing may be inadequate in patients >121 kg. Further study is warranted to define the optimal dosing of eptifibatide and other medications in obese patients.

Safety and efficacy of adjusted-dose eptifibatide in patients with acute coronary syndromes and reduced renal function

BACKGROUND

Dose adjustment of renally excreted antithrombotic drugs is recommended for patients with reduced renal function. We examined the influence of dose modification on bleeding and efficacy.

METHODS

Based on initial study drug infusion rate, Early GP IIb/IIIa Inhibition in non-ST-segment elevation acute coronary syndromes (EARLY ACS) patients were categorized into groups: standard dose (2 μg/kg/min; estimated creatinine clearance [eCrCl] ≥50 ml/min), adjusted dose (1 μg/kg/min; eCrCl <50 ml/min, per protocol), excess dose (2 μg/kg/min; eCrCl <50 ml/min). We explored relationships among initial dosing, randomized treatment assignment, and bleeding and ischemic end points (96-h composite of death, myocardial infarction [MI], recurrent ischemia requiring urgent revascularization or thrombotic bailout, and 30-d death or MI).

RESULTS

Of 8,708 patients with eCrCl and dosing data, 19% had eCrCl <50 ml/min. Of these, 13% received adjusted dose eptifibatide and 6% received an excess dose. Across all dosing groups, no significant reductions were found in ischemic end points between early versus delayed provisional eptifibatide (OR 1.14, 95% CI 0.80-1.65; OR 1.13, 95% CI 0.81-1.56, respectively, for 96-h and 30-d composite end points). Bleeding risk was not significantly increased in the early versus delayed provisional treatment group in either the adjusted (OR 1.50, 95% CI 0.95-2.39) or excess dose group (OR 1.67, 95% CI 0.85-3.39). There were no significant interactions between dose group and treatment strategy on bleeding or efficacy.

CONCLUSION

Similar to observations in practice, despite guidelines recommendations and protocol guidance, 34% of EARLY ACS patients with reduced renal function failed to receive an appropriately adjusted study drug infusion. Use of an appropriately adjusted eptifibatide infusion was not associated with expected reductions in bleeding among patients with renal insufficiency.

Antiplatelet therapy in acute coronary syndromes: implications for nursing practice

The care of cardiovascular patients experiencing a myocardial infarction (MI) has evolved from simple bed rest and relief of pain to complex interventions and multiple medications that target both the short- and long-term risks associated with atherosclerosis and ischemia. Even the terminology has changed, from MI to acute coronary syndromes (ACSs). The term, acute coronary syndrome, refers to the clinical symptoms resulting from acute myocardial ischemia; it encompasses unstable angina, non-ST-elevation MI, and ST-elevation MI. Antiplatelet therapies are critically important in the management of patients with ACS. Antiplatelet therapies interfere with platelet aggregation and platelet activation both acutely and chronically and thus impact the development of acute MI. Thus, they are prescribed for millions of patients with ACS. As a result of this progress in treatment, nursing management of persons with ACS has also evolved. This article reviews the pathophysiology of ACS, the role of antiplatelet therapies, their effects on platelet adhesion, and the role of the nurse in caring for patients with ACS who are prescribed these important therapies.

Use of antiplatelet inhibitors in peripheral vascular interventions

In the past decade, a tremendous amount of information has been gathered about platelet function and its impact on percutaneous vascular interventions. Strategies for prevention of platelet aggregation have moved beyond aspirin administration. Powerful oral antiplatelet agents such as ticlopidine (Ticlid) and clopidogrel (Plavix) have been developed to prevent platelet aggregation and thrombosis. The discovery of the glycoprotein IIb/IIIa receptor, which is responsible for platelet aggregation, has led to the development of receptor antagonists. These drugs include abciximab (ReoPro), eptifibatide (Integrilin), and tirofiban (Aggrastat). Several large studies have demonstrated that these drugs can improve outcomes in coronary interventions. Because most of the data regarding antiplatelet agents in percutaneous interventions comes from studies of coronary interventions, knowledge of these studies is necessary before using the antiplatelet drugs in peripheral vascular interventions. This article reviews the use of these agents in percutaneous coronary artery interventions and discusses their potential use in peripheral interventions.

Thrombocytopenia following percutaneous coronary intervention

BACKGROUND

Thrombocytopenia following percutaneous coronary intervention (PCI) is an underappreciated condition that is often clinically challenging. There are no guidelines on the management of patients with this condition.

OBJECTIVE

To review recent data in etiologies, risk factors, prevention, management, and prognostic implications of thrombocytopenia following PCI.

EVIDENCE ACQUISITION

Search of MEDLINE, EMBASE, the Cochrane Database, and Google Scholar using the term thrombocytopenia + PCI and other relevant keywords to identify systematic reviews, clinical trials, cohort studies, case series, and case reports. The review was limited to English-language articles published between January 1980 and June 2009. Articles on patients with baseline thrombocytopenia prior to PCI were excluded.

EVIDENCE SYNTHESIS

Thrombocytopenia is not infrequent following PCI. The typical patient with post-PCI thrombocytopenia is on multiple therapies that can potentially cause a decrease in the platelet count. Identification of the cause is critical because management of the condition varies significantly based on the etiology. The severity of the thrombocytopenia also determines the clinical management of the patient. Several observational studies have demonstrated the adverse prognostic impact of the complication on clinical outcomes and have identified risk factors.

CONCLUSIONS

Judicious use of therapies that can cause thrombocytopenia, efficient detection of the cause of the decrease in platelet count, and appropriate management of the condition can potentially improve the quality of care and outcomes following PCI. Further research into risk factors that predispose post-PCI patients to developing thrombocytopenia is warranted.

Bivalirudin in contemporary percutaneous coronary intervention for non-ST-segment elevation acute coronary syndromes: what is the current role of platelet glycoprotein IIb/IIIa receptor inhibitor agents?

Currently, the wide variety of antithrombotic agents as adjunctive pharmacological therapy for non-ST-segment elevation acute coronary syndromes (ACS) in the setting of contemporary percutaneous coronary intervention (PCI) available for clinical use has made choosing the optimal drug therapy a complex and difficult task. In the stent era, bivalirudin, a semisynthetic direct thrombin inhibitor, has recently been shown to provide similar efficacy with less bleeding compared with unfractionated heparin plus platelet glycoprotein IIb/IIIa inhibitors in ACS patients treated with PCI. Although there are some controversial results and limitations in the studies with bivalirudin, this drug certainly is a plausible option in the treatment of ACS. With current findings in contemporary PCI, there may be a steady increase in the utilization of bivalirudin. On the other hand, in the real world, there may be reinforcement in the sole use of unfractionated heparin confining glycoprotein IIb/IIIa inhibitors and other intravenous antithrombotics to bailout therapy for periprocedural PCI complications in ACS patients.

The evolving role of glycoprotein IIb/IIIa inhibitors in the setting of percutaneous coronary intervention strategies to minimize bleeding risk and optimize outcomes

The use of glycoprotein IIb/IIIa inhibitors (GPI) reduces ischemic events in patients undergoing percutaneous coronary intervention (PCI). However, the same properties that confer this benefit lead to an increased bleeding risk. Recent studies have shown a less robust net clinical benefit of GPI in the current era of routine thienopyridine and direct thrombin inhibitor use. To optimize the net clinical benefit of GPI, these agents need to be selectively used in patients most likely to benefit from their anti-ischemic effect, namely patients undergoing PCI for non-ST-segment elevation myocardial infarction, select patients undergoing primary PCI, and select patients undergoing PCI without appropriate pre-loading with a thienopyridine. Moreover, strategies to minimize bleeding should be applied in these patients and include shorter GPI infusions (in some patients), dose adjustments of heparin and GPI, careful access site management with more frequent use of the transradial approach, use of smaller sheaths, and identification of patients at high bleeding risk. This review provides an update of the current literature that supports these measures, an insight on the tailored use of GPI, and a potential direction for future research addressing combined antithrombotic therapies.

Emergency cardiac surgery in patients with acute coronary syndromes: a review of the evidence and perioperative implications of medical and mechanical therapeutics

Patients with acute coronary syndromes who require emergency cardiac surgery present complex management challenges. The early administration of antiplatelet and antithrombotic drugs has improved overall survival for patients with acute myocardial infarction, but to achieve maximal benefit, these drugs are given before coronary anatomy is known and before the decision to perform percutaneous coronary interventions or surgical revascularization has been made. A major bleeding event secondary to these drugs is associated with a high rate of death in medically treated patients with acute coronary syndrome possibly because of subsequent withholding of antiplatelet and antithrombotic therapies that otherwise reduce the rate of death, stroke, or recurrent myocardial infarction. Whether the added risk of bleeding and blood transfusion in cardiac surgical patients receiving such potent antiplatelet or antithrombotic therapy before surgery specifically for acute coronary syndromes affects long-term mortality has not been clearly established. For patients who do proceed to surgery, strategies to minimize bleeding include stopping the anticoagulation therapy and considering platelet and/or coagulation factor transfusion and possibly recombinant-activated factor VIIa administration for refractory bleeding. Mechanical hemodynamic support has emerged as an important option for patients with acute coronary syndromes in cardiogenic shock. For these patients, perioperative considerations include maintaining appropriate anticoagulation, ensuring suitable device flow, and periodically verifying correct device placement. Data supporting the use of these devices are derived from small trials that did not address long-term postoperative outcomes. Future directions of research will seek to optimize the balance between reducing myocardial ischemic risk with antiplatelet and antithrombotics versus the higher rate perioperative bleeding by better risk stratifying surgical candidates and by assessing the effectiveness of newer reversible drugs. The effects of mechanical hemodynamic support on long-term patient outcomes need more stringent analysis.

Integrin targeted therapeutics

Integrins are heterodimeric, transmembrane receptors that function as mechanosensors, adhesion molecules and signal transduction platforms in a multitude of biological processes. As such, integrins are central to the etiology and pathology of many disease states. Therefore, pharmacological inhibition of integrins is of great interest for the treatment and prevention of disease. In the last two decades several integrin-targeted drugs have made their way into clinical use, many others are in clinical trials and still more are showing promise as they advance through preclinical development. Herein, this review examines and evaluates the various drugs and compounds targeting integrins and the disease states in which they are implicated.

Bleeding associated with current therapies for acute coronary syndrome: what are the mechanisms?

Coronary artery plaque rupture results in platelet adhesion and activation, the release of adenosine diphosphate (ADP), thromboxane A(2), and the generation of thrombin. These factors propagate further platelet activation through a positive feedback mechanism, resulting in the formation of a platelet plug. The treatment of patients with ACS is centered upon the prompt initiation of both antiplatelet and anticoagulant agents. The widespread use of antiplatelet and anticoagulant agents has resulted in a significant reduction in morbidity and mortality but has also increased the risk for bleeding complications. Female gender, advanced age, low body mass index (BMI), low creatinine clearance, and the use of percutaneous coronary intervention have been consistently shown to be risk factors for bleeding. While bleeding was thought to be a necessary side effect and of little clinical significance in the past, it is now clear that bleeding is an independent predictor of adverse ischemic events and mortality. The mechanisms underlying this relationship are not yet fully elucidated and are likely multifactorial (direct effects of bleeding, increased incidence of blood transfusions, less use of antiplatelet agents in both the short and long term). Current treatment guidelines for the use of antithrombotic therapy recommend utilization of evidence-based therapies using clinical strategies shown to minimize the risk of bleeding should when possible. Novel therapies that minimize bleeding risk while providing protection against thrombotic events are needed and may improve outcomes among patients with ACS. Multiple platelet activation pathways and the coagulation cascade regulate hemostasis and thrombosis. Current antiplatelet and anticoagulant therapies for acute coronary syndromes (ACS) act on distinct sites in the pathways for platelet activation and coagulation. While these therapies are effective in reducing the morbidity and mortality associated with ACS, they are associated with a clinically significant increase in the risk of bleeding events. Novel therapies that minimize bleeding risk while providing protection against thrombotic events may improve outcomes in patients with ACS.

Strategic lessons from the clinical event classification process for the Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) trial

BACKGROUND

Independent adjudication of clinical trial events is traditionally performed by physicians on a clinical event classification (CEC) committee.

OBJECTIVES

The experience of the centralized CEC group of the APEX-AMI trial is described. This group adjudicated key secondary pre-specified outcome measures of congestive heart failure (CHF) and cardiogenic shock through 90 days using an algorithmic approach for some events.

METHODS

Data were collected via an electronic data capture (EDC) tool on all subjects, and additional information was provided via EDC for patients identified by site investigators with CHF or shock. Two strategies were used to adjudicate potential events: 1) a computer algorithm (followed by physician confirmation) analyzed data to determine whether events met trial end point definitions; or 2) physician review was used if EDC data were inadequate to allow classification by algorithm.

RESULTS

Of 5745 patients, 282 suspected cardiogenic shock and 465 suspected CHF events were identified. The computer algorithm or physicians confirmed 196/282 cardiogenic shock and 277/465 CHF end points. Overall, 242/742 (32.6%) of suspected events were classified by algorithm. Of the 500 events not resolved by computer algorithm, the CEC physicians agreed with site investigator assessments in 126/277 (45%) of CHF and 151/196 (77%) of cardiogenic shock events. The CEC committee completed adjudication of all suspected 30- and 90-day CHF and cardiogenic shock events within 7 days of the last patient 30-day follow-up visit and within 1 day of the last patient 90-day follow-up visit. Only 27% of patients required source document collection in addition to EDC-collected information.

CONCLUSIONS

A complementary approach of a computerized assessment and physician review was used in the CEC effort of the APEX-AMI trial. The algorithm categorized approximately one third of suspected CHF/cardiogenic shock events. The APEX-AMI CEC experience shows that an algorithmic approach may be a useful strategy for end point evaluation but requires validation.

Periprocedural myocardial infarction: review and classification

Technical and pharmacologic advances have reduced the occurrence of large periprocedural myocardial infarction (PMI) after percutaneous coronary interventions (PCI), but PMI still occurs in 6% to 18% of the cases and is associated with impaired short- and long-term survival. PMI might be due to side branch closure or flow-limiting dissection, but is most often diagnosed after apparently uncomplicated PCI and is due to atheroembolization into the microcirculation. Various definitions of PMI are used in clinical trials, but a rise in creatine kinase-MB greater than 3 to 8 times the upper limit of normal is consistently associated with worse prognosis, particularly as it reflects a more extensive and unstable atherosclerotic burden. On the other hand, data regarding the independent prognostic value of periprocedural troponin increase are conflicting. Some data suggest that PMI has a better prognosis than a spontaneously occurring myocardial infarction, and that its incidence is reduced with aggressive antiplatelet and statin therapy.

ED to catheterization laboratory: a roundtable integrating trials with practice

BACKGROUND

Clinical trials are the foundation underlying clinical decision-making. However, stringent inclusion and exclusion criteria may reduce the generalizability of their results, especially for patients seen in the emergency department (ED). Guideline recommendations, based on clinical trials and pertinent registries, apply to broad populations, but not all patients cared for at the bedside fit the predefined categories that make guidelines practical. Furthermore, these documents may not incorporate the latest evidence. As a result, other factors (eg, individual patient characteristics, clinician experience, cost, regulatory labels, expert opinions) often result in clinical decision-making that varies from strict adherence to guideline recommendations.

OBJECTIVES

These challenges demonstrate a need to integrate clinical data and guidelines advice with actual ED practice in a manner that will be consistent with decisions made later in the continuum of care.

DISCUSSION

In recognition of these issues, a roundtable was convened in New York City on June 5, 2009, to discuss the implications of recent trials involving patients with non-ST-segment elevation acute coronary syndromes. Eight physicians, representing both emergency medicine and cardiology, shared information on advances and clinical trial results in antiplatelet treatment, guidelines, and other developments in patient care. This article is based on transcripts of their presentations and the ensuing discussions that were of particular importance for emergency physicians.

CONCLUSIONS

Although guidelines and clinical registries can provide broad direction for practice, there is no substitute for a prospective, multidisciplinary, institution-specific, consistent, evidence-based approach to patient management.

Comparison of Bivalirudin versus Bivalirudin plus glycoprotein IIb/IIIa inhibitor versus heparin plus glycoprotein IIb/IIIa inhibitor in patients with acute coronary syndromes having percutaneous intervention for narrowed saphenous vein aorto-coronary grafts (the ACUITY trial investigators)

Clinical outcomes in patients with acute coronary syndromes randomized in the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial who underwent percutaneous coronary intervention (PCI) of saphenous vein grafts (SVGs) were examined. The ACUITY trial assessed the safety and efficacy of bivalirudin alone versus bivalirudin plus a glycoprotein (GP) IIb/IIIa inhibitor versus heparin plus a GP IIb/IIIa inhibitor in 13,819 patients with moderate- and high-risk acute coronary syndromes, 7,789 of whom underwent PCI. A total of 329 patients (4.2%) underwent PCI of SVGs in ACUITY. The primary end points at 30 days were composite ischemia or major adverse cardiac events (death, myocardial infarction, or unplanned target vessel revascularization), major bleeding (unrelated to coronary artery bypass grafting), and net adverse clinical events (composite ischemia or major bleeding). The rates of ischemic, bleeding, and net clinical end points were similar with bivalirudin monotherapy, bivalirudin plus a GP IIb/IIIa inhibitor, and heparin plus a GP IIb/IIIa inhibitor. Net adverse clinical outcome rates at 30 days were 22%, 26%, and 22% (p = 0.67), respectively, for the 3 groups. Major adverse cardiac event rates at 1 year were 37%, 37%, and 43% (p = 0.95), respectively. Minor bleeding unrelated to coronary artery bypass grafting at 30 days was significantly lower with bivalirudin alone compared with heparin plus a GP IIb/IIIa inhibitor (26% vs 38%, p = 0.05). In conclusion, bivalirudin is an effective anticoagulant in PCI of SVGs in acute coronary syndromes, with similar rates of major adverse cardiac events and net adverse cardiac events and lower minor bleeding complications in comparison with heparin plus a GP IIb/IIIa inhibitor or bivalirudin plus a GP IIb/IIIa inhibitor.

Safety and feasibility of intraarterial eptifibatide as a revascularization tool in acute ischemic stroke

OBJECT

Experience with the use of platelet glycoprotein (GP) IIb-IIIa inhibitor eptifibatide in patients with ischemic stroke is limited. The authors report the off-label use of intraarterial eptifibatide during endovascular ischemic stroke revascularization procedures for reocclusion after documented recanalization or formed fresh thrombi in distal vessels that were inaccessible to endovascular devices.

METHODS

Patients who received intraarterial eptifibatide were identified from a prospectively collected database of patients in whom endovascular revascularization for acute ischemic stroke was attempted between 2005 and 2008. Data were analyzed retrospectively. The intraarterial eptifibatide dose was a single-bolus dose of 180 μg/kg body weight. Primary outcome measures were angiographic recanalization (Thrombolysis in Myocardial Infarction Grade 2 or 3), symptomatic intracranial hemorrhage rate, overall mortality rate, and favorable 3-month modified Rankin Scale score (≤ 2).

RESULTS

The study included 35 patients (mean age 62 years, range 18-85 years). The median presenting National Institutes of Health Stroke Scale score was 13. Two patients received intravenous tissue plasminogen activator before endovascular therapy. The median time from symptom onset to therapy initiation was 230 minutes (range 90-1370 minutes). Twelve patients (34%) received intraarterial tissue plasminogen activator without mechanical measures. Mechanical revascularization measures used were Merci retriever in 19 (54%), Penumbra device in 1 (3%), balloon angioplasty in 15 (43%), and stent placement in 22 (63%) patients. The mean dose of intraarterial eptifibatide was 11.6 mg (range 5-16.6 mg). Partial-to-complete recanalization (Thrombolysis in Myocardial Infarction Grade 2 or 3) was achieved in 27 patients (77%). Postprocedure intracranial hemorrhage occurred in 13 patients (37%), causing symptoms in 5 (14%). In the 5 symptomatic intracranial hemorrhage cases, all patients but one presented more than 8 hours after symptom onset and all received intraarterial recombinant tissue plasminogen activator. The median discharge National Institutes of Health Stroke Scale score was 7 (range 0-17). At 3 months postprocedure, 21 patients (60%) had a modified Rankin Scale score ≤ 2, and 8 patients (23%) had died.

CONCLUSIONS

Adjunctive intraarterial eptifibatide is a feasible option for salvage of reocclusion and thrombolysis of distal inaccessible thrombi during endovascular stroke revascularization. Its safety and efficacy need to be studied further in larger, multicenter, controlled studies.

Platelet glycoprotein IIb/IIIa blockers during percutaneous coronary intervention and as the initial medical treatment of non-ST segment elevation acute coronary syndromes

BACKGROUND

During percutaneous coronary intervention (PCI), and in non-ST segment elevation acute coronary syndromes (NSTEACS), the risk of acute vessel occlusion by thrombosis is high. IIb/IIIa blockers strongly inhibit platelet aggregation and may prevent mortality and myocardial infarction (MI). This is an update of a Cochrane review first published in 2001, and previously updated in 2007.

OBJECTIVES

To assess the effects and safety of IIb/IIIa blockers when administered during PCI, and as initial medical treatment in patients with NSTEACS.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 3, 2009), MEDLINE (1966 to October 2009), and EMBASE (1980 to October 2009).

SELECTION CRITERIA

Randomised controlled trials comparing intravenous IIb/IIIa blockers with placebo or usual care.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion, assessed trial quality and extracted data. We collected major bleeding as adverse effect information from the trials. Odds ratios (OR) and 95% confidence intervals (CI) were used for effect measures.

MAIN RESULTS

Forty-eight trials involving 62,417 patients were included. During PCI, IIb/IIIa blockers decreased mortality at 30 days (OR 0.76, 95% CI 0.62 to 0.95) and at six months (OR 0.84, 95% CI 0.71 to 1.00). Death or MI was decreased both at 30 days (OR 0.65, 95% CI 0.60 to 0.72), and at 6 months (OR 0.70, 95% CI 0.61 to 0.81), although severe bleeding was increased (OR 1.38, 95% CI 1.20 to 1.59; absolute risk increase (ARI) 8.0 per 1000). The efficacy results were homogeneous for every endpoint according to the clinical condition of the patients, but were less marked for patients pre-treated with clopidogrel, especially in patients without ACS.As initial medical treatment of NSTEACS, IIb/IIIa blockers did not decrease mortality at 30 days (OR 0.91, 95% CI 0.80 to 1.03) or at six months (OR 1.00, 95% CI 0.87 to 1.15), but slightly decreased death or MI at 30 days (OR 0.92, 95% CI 0.86 to 0.99) and at six months (OR 0.88, 95% CI 0.81 to 0.96), although severe bleeding was increased (OR 1.27, 95% CI 1.12 to 1.43; ARI 1.4 per 1000).

AUTHORS' CONCLUSIONS

When administered during PCI, intravenous IIb/IIIa blockers reduce the risk of death and of death or MI at 30 days and at six months, at a price of an increase in the risk of severe bleeding. The efficacy effects are homogeneous but are less marked in patients pre-treated with clopidogrel where they seem to be effective only in patients with ACS. When administered as initial medical treatment in patients with NSTEACS, these agents do not reduce mortality although they slightly reduce the risk of death or MI.

Comparison of catheterization laboratory initiated abciximab and eptifibatide during percutaneous coronary intervention in acute coronary syndromes (an ACUITY substudy)

Abciximab and eptifibatide have been shown to reduce ischemic complications compared with heparin alone in patients with acute coronary syndromes who undergo percutaneous coronary intervention. Whether 1 agent is safer and/or more effective has not been prospectively examined. The aim of this study was to assess the outcomes related to downstream glycoprotein IIb/IIIa inhibitor treatment selection during percutaneous coronary intervention in 2,211 patients with moderate and high-risk acute coronary syndromes in the prospective multicenter Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial. The protocol permitted operator selection of abciximab (n = 835) or eptifibatide (n = 1,376) for routine use in the trial. Multivariate and propensity-based adjustments were used to assess the independent association of glycoprotein IIb/IIIa inhibitor treatment selection with prespecified study end points. Compared to patients receiving eptifibatide, those administered abciximab were older, more likely to be enrolled outside of North America, more frequently had biomarker elevations and ST-segment deviation, but had fewer baseline cardiac risk factors and previous revascularization procedures. After multivariate propensity-based adjustment, abciximab was independently associated with significantly fewer net clinical adverse events (odds ratio 0.61, 95% confidence interval 0.42 to 0.90, p = 0.01), mediated by composite ischemia (odds ratio 0.61, 95% confidence interval 0.38 to 0.98, p = 0.04) and major bleeding (odds ratio 0.58, 95% confidence interval 0.34 to 1.00, p = 0.051). In conclusion, in this prespecified but nonrandomized comparison in patients with acute coronary syndromes who underwent percutaneous coronary intervention with catheterization laboratory initiation of glycoprotein IIb/IIIa inhibitors, the use of abciximab rather than eptifibatide was associated with improved clinical outcomes at 30 days. These findings should be viewed as exploratory in light of the nonrandomized and heterogeneous nature of the comparator groups and significant potential for residual confounding.

A multicenter randomized study to evaluate intracoronary abciximab with the ClearWay catheter to improve outcomes with Lysis (IC ClearLy): trial study design and rationale

BACKGROUND

Percutaneous coronary intervention (PCI) is a highly effective therapy for acute ST-elevation myocardial infarction. Adjunctive therapy with platelet glycoprotein (GP) IIb/IIIa inhibitor can result in increased vessel patency and improved outcomes in ST-elevation myocardial infarction patients undergoing PCI. The investigation of novel dosing and delivery strategies of this therapy may help to further improve outcomes.

METHODS

IC-Clearly is a randomized, open-label, multicenter trial, with the purpose of evaluating the effectiveness of an intracoronary bolus dose of abciximab delivered using the ClearWay RX catheter vs. an intravenous bolus of abciximab for ST-elevation myocardial infarction with angiographically visible thrombus (thrombus grade >or=2). A total of 150 patients will be randomized 1: 1 to treatment of the culprit artery with intracoronary abciximab (75 patients) or intravenous abciximab (75 patients) in addition to a maintenance infusion regimen of abciximab administered intravenously for 12 h after PCI. The number of patients included in this study is based on the estimation of sample size needed to identify a statistically significant difference in the primary endpoints between the two groups. The primary endpoint chosen to evaluate this hypothesis is infarct size assessed by cardiac magnetic resonance. Clinical outcomes will be assessed for each patient through hospital discharge and at 30-day follow-up.

CONCLUSION

The purpose of this study is to evaluate whether an intracoronary bolus of abciximab delivered with the ClearWay RX catheter prior to the 12 h post-PCI intravenous infusion regimen of abciximab will result in significant additional clot resolution in vivo and improved myocardial perfusion when compared with an intravenous bolus of abciximab on top of the 12 h post-PCI intravenous infusion regimen of abciximab as per standard practice. The primary endpoint chosen to evaluate this hypothesis is infarct size as assessed by cardiac magnetic resonance.

Triple antiplatelet therapy for preventing vascular events: a systematic review and meta-analysis

BACKGROUND

Dual antiplatelet therapy is usually superior to mono therapy in preventing recurrent vascular events (VEs). This systematic review assesses the safety and efficacy of triple antiplatelet therapy in comparison with dual therapy in reducing recurrent vascular events.

METHODS

Completed randomized controlled trials investigating the effect of triple versus dual antiplatelet therapy in patients with ischaemic heart disease (IHD), cerebrovascular disease or peripheral vascular disease were identified using electronic bibliographic searches. Data were extracted on composite VEs, myocardial infarction (MI), stroke, death and bleeding and analysed with Cochrane Review Manager software. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using random effects models.

RESULTS

Twenty-five completed randomized trials (17,383 patients with IHD) were included which involving the use of intravenous (iv) GP IIb/IIIa inhibitors (abciximab, eptifibatide, tirofiban), aspirin, clopidogrel and/or cilostazol. In comparison with aspirin-based therapy, triple therapy using an intravenous GP IIb/IIIa inhibitor significantly reduced composite VEs and MI in patients with non-ST elevation acute coronary syndromes (NSTE-ACS) (VE: OR 0.69, 95% CI 0.55-0.86; MI: OR 0.70, 95% CI 0.56-0.88) and ST elevation myocardial infarction (STEMI) (VE: OR 0.39, 95% CI 0.30-0.51; MI: OR 0.26, 95% CI 0.17-0.38). A significant reduction in death was also noted in STEMI patients treated with GP IIb/IIIa based triple therapy (OR 0.69, 95% CI 0.49-0.99). Increased minor bleeding was noted in STEMI and elective percutaneous coronary intervention (PCI) patients treated with GP IIb/IIIa based triple therapy. Stroke events were too infrequent for us to be able to identify meaningful trends and no data were available for patients recruited into trials on the basis of stroke or peripheral vascular disease.

CONCLUSIONS

Triple antiplatelet therapy based on iv GPIIb/IIIa inhibitors was more effective than aspirin-based dual therapy in reducing VEs in patients with acute coronary syndromes (STEMI and NSTEMI). Minor bleeding was increased among STEMI and elective PCI patients treated with a GP IIb/IIIa based triple therapy. In patients undergoing elective PCI, triple therapy had no beneficial effect and was associated with an 80% increase in transfusions and an eightfold increase in thrombocytopenia. Insufficient data exist for patients with prior ischaemic stroke and peripheral vascular disease and further research is needed in these groups of patients.

Eptifibatide: The evidence for its role in the management of acute coronary syndromes

Introduction:

Acute coronary syndromes and non-Q-wave myocardial infarction are often initiated by platelet activation. Eptifibatide is a cyclic heptapeptide and is the third inhibitor of glycoprotein (Gp) IIb/IIIa that has found broad acceptance after the specific antibody abciximab and the nonpeptide tirofiban entered the global market. Gp IIb/IIIa inhibitors act by inhibiting the final common pathway of platelet aggregation, and play an important role in the management of acute coronary syndromes.

Aims:

This review assesses the evidence for therapeutic value of eptifibatide as a Gp IIb/IIIa inhibitor in patients with acute coronary syndromes.

Evidence review:

Several large, randomized controlled trials show that eptifibatide as adjunctive therapy to standard care in patients with non-ST segment elevation acute coronary syndrome is associated with a significant reduction in the incidence of death or myocardial infarction. Data are limited regarding the use of eptifibatide in patients with ST segment elevation myocardial infarction. Cost-effectiveness analysis indicates that eptifibatide is associated with a favorable cost-effectiveness ratio relative to standard care. According to US cost-effectiveness analysis about 70% of the acquisition costs of eptifibatide are offset by the reduced medical resource consumption during the first year. Eptifibatide was well tolerated in most of the trials. Bleeding is the most commonly reported adverse event, with most major bleeding episodes occurring at the vascular access site. Major intracranial bleeds, stroke, or profound thrombocytopenia rarely occurred during eptifibatide treatment.

Place in therapy:

Eptifibatide has gained widespread acceptance as an adjunct to standard anticoagulation therapy in patients with acute coronary syndromes, and may be particularly useful in the management of patients with elevated troponin or undergoing percutaneous coronary interventions.

Bridging the gap between clinical trials of antiplatelet therapies and applications among elderly patients

Although patients aged > or =75 years represent nearly 40% of all those hospitalized with acute coronary syndromes, their enrollment in trials of therapeutic interventions has been relatively modest. Thus, scarce information exists to guide clinicians in decision-making and assessing projections of safety and efficacy for antiplatelet agents. The pathobiology of aging, including age-related changes in vascular repair and integrity, applies to patient management and offers a platform for investigation. Because older patients receive excess dosing of antithrombotic agents much more often than their younger counterparts do, initial steps toward optimized care include attention to indications, dosing, and duration of treatment. This review, representing a summary of information presented at the Fourth Annual Platelet Colloquium held in Washington, DC, in January 2009 and supplemented with recent clinical trial results, underscores an increasingly narrow safety index for antiplatelet agents in the elderly and the all-important balance of safety and efficacy--a dynamic continuum that remains paramount in quality of care. Considerations for future trial designs, registries, and analyses of existing data are highlighted to better guide clinicians toward the optimal management of this rapidly growing, high-risk group.