Long-term treatment with a platelet glycoprotein-receptor antagonist after percutaneous coronary revascularization. EXCITE Trial Investigators. Evaluation of Oral Xemilofiban in Controlling Thrombotic Events

Clinical Outcomes With Postprocedural Anticoagulation Versus No Anticoagulation in Patients With Acute Myocardial Infarction After Percutaneous Coronary Intervention: A Meta-Analysis

Postprocedural anticoagulation (PPAC) after percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI) can mitigate thrombotic events. However, current clinical guidelines do not recommend PPAC after PCI considering the scarce evidence supporting its use. A comprehensive literature search of electronic databases was conducted to identify studies comparing PPAC to no anticoagulation (AC) after PCI for AMI. Using the inverse-variance random-effects model, we pooled risk ratios (RRs) with 95% confidence intervals (CIs), with P < 0.05 considered statistically significant. Seven studies with a total of 47,981 patients (32,010: PPAC and 15,971: no AC) were included in the final analysis. PPAC administration demonstrated no significant difference in 30-day all-cause mortality [RR, 0.73 (95% CI, 0.47-1.16); P = 0.19], 30-day cardiovascular mortality [RR, 0.76 (95% CI, 0.45-1.30); P = 0.32], 30-day myocardial infarction [RR, 0.68 (95% CI, 0.41-1.12); P = 0.13], 30-day stroke [RR, 0.89 (95% CI, 0.47-1.67); P = 0.71], 30-day target vessel revascularization [RR, 0.74 (95% CI, 0.37-1.47); P = 0.39], 30-day stent thrombosis [RR, 1.08 (95% CI, 0.75-1.57); P = 0.67], and 30-day bleeding [RR, 1.25 (95% CI, 0.83-1.88); P = 0.29] compared with no AC. This meta-analysis concludes that there are no benefits of routine PPAC after PCI in AMI. The decision to prolong anticoagulant use post-PCI depends on risk versus benefits, which vary from case to case. Future large-scale multicentric randomized trials are warranted to corroborate the results of this meta-analysis.

Eptifibatide, an Older Therapeutic Peptide with New Indications: From Clinical Pharmacology to Everyday Clinical Practice

Therapeutic peptides are oligomers or short polymers of amino acids used for various medical purposes. Peptide-based treatments have evolved considerably due to new technologies, stimulating new research interests. They have been shown to be beneficial in a variety of therapeutic applications, notably in the treatment of cardiovascular disorders such as acute coronary syndrome (ACS). ACS is characterized by coronary artery wall damage and consequent formation of an intraluminal thrombus obstructing one or more coronary arteries, leading to unstable angina, non-ST elevated myocardial infarction, and ST-elevated myocardial infarction. One of the promising peptide drugs in the treatment of these pathologies is eptifibatide, a synthetic heptapeptide derived from rattlesnake venom. Eptifibatide is a glycoprotein IIb/IIIa inhibitor that blocks different pathways in platelet activation and aggregation. In this narrative review, we summarized the current evidence on the mechanism of action, clinical pharmacology, and applications of eptifibatide in cardiology. Additionally, we illustrated its possible broader usage with new indications, including ischemic stroke, carotid stenting, intracranial aneurysm stenting, and septic shock. Further research is, however, required to fully evaluate the role of eptifibatide in these pathologies, independently and in comparison to other medications.

An Updated Review on Glycoprotein IIb/IIIa Inhibitors as Antiplatelet Agents: Basic and Clinical Perspectives

The glycoprotein (GP) IIb/IIIa receptor is found integrin present in platelet aggregations. GP IIb/IIIa antagonists interfere with platelet cross-linking and platelet-derived thrombus formation through the competition with fibrinogen and von Willebrand factor. Currently, three parenteral GP IIb/IIIa competitors (tirofiban, eptifibatide, and abciximab) are approved for clinical use in patients affected by percutaneous coronary interventions (PCI) in the location of acute coronary syndrome (ACS). GP IIb/IIIa antagonists have their mechanism of action in platelet aggregation prevention, distal thromboembolism, and thrombus formation, whereas the initial platelet binding to damage vascular areas is preserved. This work is aimed to provide a comprehensive review of the significance of GP IIb/IIIa inhibitors as a sort of antiplatelet agent. Their mechanism of action is based on factors that affect their efficacy. On the other hand, drugs that inhibit GP IIb/IIIa already approved by the FDA were reviewed in detail. Results from major clinical trials and regulatory practices and guidelines to deal with GP IIb/IIIa inhibitors were deeply investigated. The cardiovascular pathology and neuro-interventional surgical application of GP IIb/IIIa inhibitors as a class of antiplatelet agents were developed in detail. The therapeutic risk/benefit balance of currently available GP IIb/IIa receptor antagonists is not yet well elucidated in patients with ACS who are not clinically evaluated regularly for early cardiovascular revascularization. On the other hand, in patients who have benefited from PCI, the antiplatelet therapy intensification by the addition of a GP IIb/IIIa receptor antagonist (intravenously) may be an appropriate therapeutic strategy in reducing the occurrence of risks of thrombotic complications related to the intervention. Development of GP IIb/IIIa inhibitors with oral administration has the potential to include short-term antiplatelet benefits compared with intravenous GP IIb/IIIa inhibitors for long-term secondary preventive therapy in cardiovascular disease. But studies showed that long-term oral administration of GP IIb/IIIa receptor inhibitors has been ineffective in preventing ischemic events. Paradoxically, they have been linked to a high risk of side effects by producing prothrombotic and pro-inflammatory events.

Antiplatelet agents and anticoagulants for hypertension

BACKGROUND

The main complications of elevated systemic blood pressure (BP), coronary heart disease, ischaemic stroke, and peripheral vascular disease, are related to thrombosis rather than haemorrhage. Therefore, it is important to investigate if antithrombotic therapy may be useful in preventing thrombosis-related complications in patients with elevated BP.

OBJECTIVES

To conduct a systematic review of the role of antiplatelet therapy and anticoagulation in patients with elevated BP, including elevations in systolic or diastolic BP alone or together. To assess the effects of antiplatelet agents on total deaths or major thrombotic events or both in these patients versus placebo or other active treatment. To assess the effects of oral anticoagulants on total deaths or major thromboembolic events or both in these patients versus placebo or other active treatment.

SEARCH METHODS

The Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials (RCTs) up to January 2021: the Cochrane Hypertension Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL; 2020, Issue 12), Ovid MEDLINE (from 1946), and Ovid Embase (from 1974). The World Health Organization International Clinical Trials Registry Platform and the US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov) were searched for ongoing trials.  SELECTION CRITERIA: RCTs in patients with elevated BP were included if they were ≥ 3 months in duration and compared antithrombotic therapy with control or other active treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data for inclusion criteria, our prespecified outcomes, and sources of bias. They assessed the risks and benefits of antiplatelet agents and anticoagulants by calculating odds ratios (OR), accompanied by the 95% confidence intervals (CI). They assessed risks of bias and applied GRADE criteria.  MAIN RESULTS: Six trials (61,015 patients) met the inclusion criteria and were included in this review. Four trials were primary prevention (41,695 patients; HOT, JPAD, JPPP, and TPT), and two secondary prevention (19,320 patients, CAPRIE and Huynh). Four trials (HOT, JPAD, JPPP, and TPT) were placebo-controlled and two studies (CAPRIE and Huynh) included active comparators. Four studies compared acetylsalicylic acid (ASA) versus placebo and found no evidence of a difference for all-cause mortality (OR 0.97, 95% CI 0.87 to 1.08; 3 studies, 35,794 participants; low-certainty evidence). We found no evidence of a difference for cardiovascular mortality (OR 0.98, 95% CI 0.82 to 1.17; 3 studies, 35,794 participants; low-certainty evidence). ASA reduced the risk of all non-fatal cardiovascular events (OR 0.63, 95% CI 0.45 to 0.87; 1 study (missing data in 3 studies), 2540 participants; low-certainty evidence) and the risk of all cardiovascular events (OR 0.86, 95% CI 0.77 to 0.96; 3 studies, 35,794 participants; low-certainty evidence). ASA increased the risk of major bleeding events (OR 1.77, 95% CI 1.34 to 2.32; 2 studies, 21,330 participants; high-certainty evidence). One study (CAPRIE; ASA versus clopidogrel) included patients diagnosed with hypertension (mean age 62.5 years, 72% males, 95% Caucasians, mean follow-up: 1.91 years). It showed no evidence of a difference for all-cause mortality (OR 1.02, 95% CI 0.91 to 1.15; 1 study, 19,143 participants; high-certainty evidence) and for cardiovascular mortality (OR 1.08, 95% CI 0.94 to 1.26; 1 study, 19,143 participants; high-certainty evidence). ASA probably reduced the risk of non-fatal cardiovascular events (OR 1.10, 95% CI 1.00 to 1.22; 1 study, 19,143 participants; high-certainty evidence) and the risk of all cardiovascular events (OR 1.08, 95% CI 1.00 to 1.17; 1 study, 19,143 participants; high-certainty evidence) when compared to clopidogrel. Clopidogrel increased the risk of major bleeding events when compared to ASA (OR 1.35, 95% CI 1.14 to 1.61; 1 study, 19,143 participants; high-certainty evidence). In one study (Huynh; ASA verus warfarin) patients with unstable angina or non-ST-segment elevation myocardial infarction, with prior coronary artery bypass grafting (CABG) were included (mean age 68 years, 79.8% males, mean follow-up: 1.1 year). There was no evidence of a difference for all-cause mortality (OR 0.98, 95% CI 0.06 to 16.12; 1 study, 91 participants; low-certainty evidence). Cardiovascular mortality, non-fatal cardiovascular events, and all cardiovascular events were not available. There was no evidence of a difference for major bleeding events (OR 0.13, 95% CI 0.01 to 2.60; 1 study, 91 participants; low-certainty evidence).  AUTHORS' CONCLUSIONS: There is no evidence that antiplatelet therapy modifies mortality in patients with elevated BP for primary prevention. ASA reduced the risk of cardiovascular events and increased the risk of major bleeding events.  Antiplatelet therapy with ASA probably reduces the risk of non-fatal and all cardiovascular events when compared to clopidogrel. Clopidogrel increases the risk of major bleeding events compared to ASA in patients with elevated BP for secondary prevention.  There is no evidence that warfarin modifies mortality in patients with elevated BP for secondary prevention.  The benefits and harms of the newer drugs glycoprotein IIb/IIIa inhibitors, clopidogrel, prasugrel, ticagrelor, and non-vitamin K antagonist oral anticoagulants for patients with high BP have not been studied in clinical trials. Further RCTs of antithrombotic therapy including newer agents and complete documentation of all benefits and harms are required in patients with elevated BP.

Antiplatelet agents for chronic kidney disease

BACKGROUND

Antiplatelet agents are widely used to prevent cardiovascular events. The risks and benefits of antiplatelet agents may be different in people with chronic kidney disease (CKD) for whom occlusive atherosclerotic events are less prevalent, and bleeding hazards might be increased. This is an update of a review first published in 2013.

OBJECTIVES

To evaluate the benefits and harms of antiplatelet agents in people with any form of CKD, including those with CKD not receiving renal replacement therapy, patients receiving any form of dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 13 July 2021 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We selected randomised controlled trials of any antiplatelet agents versus placebo or no treatment, or direct head-to-head antiplatelet agent studies in people with CKD. Studies were included if they enrolled participants with CKD, or included people in broader at-risk populations in which data for subgroups with CKD could be disaggregated.

DATA COLLECTION AND ANALYSIS

Four authors independently extracted data from primary study reports and any available supplementary information for study population, interventions, outcomes, and risks of bias. Risk ratios (RR) and 95% confidence intervals (CI) were calculated from numbers of events and numbers of participants at risk which were extracted from each included study. The reported RRs were extracted where crude event rates were not provided. Data were pooled using the random-effects model. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 113 studies, enrolling 51,959 participants; 90 studies (40,597 CKD participants) compared an antiplatelet agent with placebo or no treatment, and 29 studies (11,805 CKD participants) directly compared one antiplatelet agent with another. Fifty-six new studies were added to this 2021 update. Seven studies originally excluded from the 2013 review were included, although they had a follow-up lower than two months. Random sequence generation and allocation concealment were at low risk of bias in 16 and 22 studies, respectively. Sixty-four studies reported low-risk methods for blinding of participants and investigators; outcome assessment was blinded in 41 studies. Forty-one studies were at low risk of attrition bias, 50 studies were at low risk of selective reporting bias, and 57 studies were at low risk of other potential sources of bias. Compared to placebo or no treatment, antiplatelet agents probably reduces myocardial infarction (18 studies, 15,289 participants: RR 0.88, 95% CI 0.79 to 0.99, I² = 0%; moderate certainty). Antiplatelet agents has uncertain effects on fatal or nonfatal stroke (12 studies, 10.382 participants: RR 1.01, 95% CI 0.64 to 1.59, I² = 37%; very low certainty) and may have little or no effect on death from any cause (35 studies, 18,241 participants: RR 0.94, 95 % CI 0.84 to 1.06, I² = 14%; low certainty). Antiplatelet therapy probably increases major bleeding in people with CKD and those treated with haemodialysis (HD) (29 studies, 16,194 participants: RR 1.35, 95% CI 1.10 to 1.65, I² = 12%; moderate certainty). In addition, antiplatelet therapy may increase minor bleeding in people with CKD and those treated with HD (21 studies, 13,218 participants: RR 1.55, 95% CI 1.27 to 1.90, I² = 58%; low certainty). Antiplatelet treatment may reduce early dialysis vascular access thrombosis (8 studies, 1525 participants) RR 0.52, 95% CI 0.38 to 0.70; low certainty). Antiplatelet agents may reduce doubling of serum creatinine in CKD (3 studies, 217 participants: RR 0.39, 95% CI 0.17 to 0.86, I² = 8%; low certainty). The treatment effects of antiplatelet agents on stroke, cardiovascular death, kidney failure, kidney transplant graft loss, transplant rejection, creatinine clearance, proteinuria, dialysis access failure, loss of primary unassisted patency, failure to attain suitability for dialysis, need of intervention and cardiovascular hospitalisation were uncertain. Limited data were available for direct head-to-head comparisons of antiplatelet drugs, including prasugrel, ticagrelor, different doses of clopidogrel, abciximab, defibrotide, sarpogrelate and beraprost.

AUTHORS' CONCLUSIONS

Antiplatelet agents probably reduced myocardial infarction and increased major bleeding, but do not appear to reduce all-cause and cardiovascular death among people with CKD and those treated with dialysis. The treatment effects of antiplatelet agents compared with each other are uncertain.

Exogenous Integrin αIIbβ3 Inhibitors Revisited: Past, Present and Future Applications

The integrin αIIbβ3 is the most abundant integrin on platelets. Upon platelet activation, the integrin changes its conformation (inside-out signalling) and outside-in signalling takes place leading to platelet spreading, platelet aggregation and thrombus formation. Bloodsucking parasites such as mosquitoes, leeches and ticks express anticoagulant and antiplatelet proteins, which represent major sources of lead compounds for the development of useful therapeutic agents for the treatment of haemostatic disorders or cardiovascular diseases. In addition to hematophagous parasites, snakes also possess anticoagulant and antiplatelet proteins in their salivary glands. Two snake venom proteins have been developed into two antiplatelet drugs that are currently used in the clinic. The group of proteins discussed in this review are disintegrins, low molecular weight integrin-binding cysteine-rich proteins, found in snakes, ticks, leeches, worms and horseflies. Finally, we highlight various oral antagonists, which have been tested in clinical trials but were discontinued due to an increase in mortality. No new αIIbβ3 inhibitors are developed since the approval of current platelet antagonists, and structure-function analysis of exogenous disintegrins could help find platelet antagonists with fewer adverse side effects.

GPIIb/IIIa inhibitors: From bench to bedside and back to bench again

From the discovery of the platelet glycoprotein (GP) IIb/IIIa and identification of its central role in haemostasis, the integrin GPIIb/IIIa (αIIbβ3, CD41/CD61) was destined to be an anti-thrombotic target. The subsequent successful development of intravenous ligand-mimetic inhibitors occurred during a time of limited understanding of integrin physiology. Although efficient inhibitors of ligand binding, they also mimic ligand function. In the case of GPIIb/IIIa inhibitors, despite strongly inhibiting platelet aggregation, paradoxical fibrinogen binding and platelet activation can occur. The quick progression to development of small-molecule orally available inhibitors meant that this approach inherited many potential flaws, which together with a short half-life resulted in an increase in mortality and a halt to the numerous pharmaceutical development programs. Limited clinical benefits, together with the success of other anti-thrombotic drugs, in particular P2Y12 ADP receptor blockers, have also led to a restrictive use of intravenous GPIIb/ IIIa inhibitors. However, with a greater understanding of this key platelet-specific integrin, GPIIb/IIIa remains a potentially attractive target and future drug developments will be better informed by the lessons learnt from taking the current inhibitors back to the bench. This overview will review the physiology behind the inherent problems of a ligand-based integrin inhibitor design and discuss novel promising approaches for GPIIb/IIIa inhibition.

Contemporary Reflections on the Safety of Long-Term Aspirin Treatment for the Secondary Prevention of Cardiovascular Disease

Aspirin has been the cornerstone of therapy for the secondary prevention treatment of patients with cardiovascular disease since landmark trials were completed in the late 1970s and early 1980s that demonstrated the efficacy of aspirin for reducing the risk of ischemic events. Notwithstanding the consistent benefits demonstrated with aspirin for both acute and chronic cardiovascular disease, there are a number of toxicities associated with aspirin that have been showcased by recent long-term clinical trials that have included an aspirin monotherapy arm. As an inhibitor of cyclooxygenase (COX), aspirin impairs gastric mucosal protective mechanisms. Previous trials have shown that up to 15-20 % of patients developed gastrointestinal symptoms with aspirin monotherapy, and approximately 1 % of patients per year had a clinically significant bleeding event, including 1 in 1000 patients who suffered an intracranial or fatal bleed. These risks have been shown to be compounded for patients with acute coronary syndromes (ACS) and those undergoing percutaneous coronary intervention (PCI) who are also treated with other antithrombotic agents during the acute care/procedural period, as well as for an extended time period afterwards. Given observations of substantial increases in bleeding rates from many prior long-term clinical trials that have evaluated aspirin together with other oral platelet inhibitors or oral anticoagulants, the focus of contemporary research has pivoted towards tailored antithrombotic regimens that attempt to either shorten the duration of exposure to aspirin or replace aspirin with an alternative antithrombotic agent. While these shifts are occurring, the safety profile of aspirin when used for the secondary prevention treatment of patients with established cardiovascular disease deserves further consideration.

Platelets and Cardiovascular Disease

Platelets play an important, but often under-recognized role in cardiovascular disease. For example, the normal response of the platelet can be altered, either by increased pro-aggregatory stimuli or by diminished anti-aggregatory substances to produce conditions of increased platelet activation/aggregation and occur in active cardiovascular disease states both on a chronic (e.g. stable angina pectoris) and acute basis (e.g. acute myocardial infarction). In addition, platelet hyperaggregability is also associated with the risk factors for coronary artery disease (e.g. smoking, hypertension, and hypercholesterolaemia). Finally, the utility of an increasing range of anti-platelet therapies in the management of the above disease states further emphasizes the pivotal role platelets play in the pathogenesis of cardiovascular disease. This paper provides a comprehensive overview of the normal physiologic role of platelets in maintain homeostasis, the pathophysiologic processes that contribute to platelet dysfunction in cardiovascular disease and the associated role and benefits of anti-platelet therapies.

Development of glycoprotein IIb–IIIa antagonists: translation of pharmacodynamic effects into clinical benefit

This article will review the development of glycoprotein IIb-IIIa antagonists, with particular emphasis on the characteristics and pharmacodynamic studies of each agent that is available for clinical use. Abciximab is a Fab fragment of the 7E3 antibody that has high affinity and a slow rate of dissociation from glycoprotein IIb-IIIa. In contrast, the small molecules eptifibatide and tirofiban, have a much more rapid rate of dissociation, with an off time of 10 to 15 s. Accordingly, the circulating pool of abciximab is predominantly associated with platelets, whereas maintenance of a consistent concentration of tirofiban and eptifibatide in the blood is critical in order to achieve and sustain their inhibitory effects. The affinity of abciximab and tirofiban for glycoprotein IIb-IIIa are substantially greater than that of eptifibatide, necessitating maintenance of greater molar concentrations of eptifibatide in blood in order to achieve effective inhibition of the binding of fibrinogen to the activated conformer of glycoprotein IIb-IIIa.

Comparing coronary artery bypass grafting with drug-eluting stenting in patients with diabetes mellitus and multivessel coronary artery disease: a meta-analysis

OBJECTIVES

Although drug-eluting stents (DESs) reduce the rate of target vessel revascularization compared with bare-metal stents, the results of DESs for patients with diabetes and multivessel coronary artery disease (CAD) in the DES era are inconsistent. This meta-analysis was undertaken to assess the efficacy and safety of coronary artery bypass grafting (CABG) compared with drug-eluting stent implantation in patients with diabetes mellitus and multivessel coronary artery disease.

METHODS

We conducted a search of Medline, EMBASE from January 2003 to July 2013 by two reviewers independently, using the terms 'coronary artery bypass graft surgery', 'drug-eluting stent', 'sirolimus-eluting stent', 'paclitaxel-eluting stent', 'diabetes mellitus' and 'multivessel disease', according to established criteria. Studies comparing CABG with DES in patients with diabetes and multivessel CAD with a minimum follow-up of 1 year were included.

RESULTS

Thirteen studies including 6653 patients with diabetes (3237 who underwent CABG and 3416 who underwent DES implantation) met the selection criteria. The mean follow-up period was 2.9 years (range 1-5). Compared with DES, CABG was associated with a lower risk for major adverse cardiac events (odds ratio [OR] 0.51, 95% confidence interval [CI] 0.46-0.58), driven mainly by a lower risk for repeat revascularization (OR 0.29, 95% CI 0.23-0.35). There was no significant difference with regard to death (OR 0.89, 95% CI 0.75-1.05). Patients in the CABG group had a higher risk for stroke events (OR 2.09, 95% CI 1.45-3.02).

CONCLUSIONS

Percutaneous coronary intervention with DES in patients with diabetes and multivessel CAD is safe, but has a high risk of long-term repeat revascularization. CABG should remain the standard procedure for diabetic patients with multivessel CAD.

Coronary artery bypass graft surgery up-regulates genes involved in platelet aggregation

BACKGROUND

During and shortly after coronary artery bypass graft (CABG) surgery, there is an increase in thromboembolic events. CABG, a strong inflammatory stimulus, is associated with a hypercoaguable state. Platelets might contribute to this hypercoaguable state because they have a pivotal role in thrombosis. In the days following surgery there is augmented platelet regeneration in response to the inflammatory stimulus.

OBJECTIVES

The aim of this study was to investigate any changes in platelet mRNA profiles to test the hypothesis that post-CABG surgery platelets are associated with a prothrombotic state.

METHODS

Blood was sampled and platelets purified from 11 patients before and 3-6 days after CABG. Gene expression profiling was performed using low density array (LDA) plates for seven of the patients.

RESULTS

Forty-five genes were examined and those significantly up-regulated were glycoprotein (GP)IIb, GPIIIa and cyclooxygenase-1 (COX-1). These findings were confirmed in four more patients, including flow cytometry analysis of the GPIIb/IIIa receptor.

CONCLUSIONS

CABG surgery up-regulates mRNA and protein levels of proteins that are key players in platelet aggregation. Marked elevation of GPIIb/IIIa mRNA levels results in significantly increased GPIIb/IIIa expression in platelets post-CABG surgery, which may be a reason for increased thrombus formation and myocardial infarction after CABG.

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.

Current concepts of platelet activation: possibilities for therapeutic modulation of heterotypic vs. homotypic aggregation

Thrombogenic and inflammatory activity are two distinct aspects of platelet biology, which are sustained by the ability of activated platelets to interact with each other (homotypic aggregation) and to adhere to circulating leucocytes (heterotypic aggregation). These two events are regulated by distinct biomolecular mechanisms that are selectively activated in different pathophysiological settings. They can occur simultaneously, for example, as part of a pro-thrombotic/pro-inflammatory response induced by vascular damage, or independently, as in certain clinical conditions in which abnormal heterotypic aggregation has been observed in the absence of intravascular thrombosis. Current antiplatelet drugs have been developed to target specific molecular signalling pathways mainly implicated in thrombus formation, and their ever increasing clinical use has resulted in clear benefits in the treatment and prevention of arterial thrombotic events. However, the efficacy of currently available antiplatelet drugs remains suboptimal, most likely because their therapeutic action is limited to only few of the signalling pathways involved in platelet homotypic aggregation. In this context, modulation of heterotypic aggregation, which is believed to contribute importantly to acute thrombotic events, as well to the pathophysiology of atherosclerosis itself, may offer benefits over and above the classical antiplatelet approach. This review will focus on the distinct biomolecular pathways that, following platelet activation, underlie homotypic and heterotypic aggregation, aiming potentially to identify novel therapeutic targets.

Antiplatelet agents and anticoagulants for hypertension

BACKGROUND

Elevated systemic blood pressure results in high intravascular pressure but the main complications, coronary heart disease (CHD), ischaemic strokes and peripheral vascular disease (PVD), are related to thrombosis rather than haemorrhage. Some complications related to elevated blood pressure, heart failure or atrial fibrillation, are themselves associated with stroke and thromboembolism. Therefore it is important to investigate if antithrombotic therapy may be useful in preventing thrombosis-related complications in patients with elevated blood pressure.

OBJECTIVES

To conduct a systematic review of the role of antiplatelet therapy and anticoagulation in patients with high blood pressure, including those with elevations in both systolic and diastolic blood pressure, isolated elevations of either systolic or diastolic blood pressure, to address the following hypotheses: (i) antiplatelet agents reduce total deaths and/or major thrombotic events when compared to placebo or other active treatment; and (ii) oral anticoagulants reduce total deaths and/or major thromboembolic events when compared to placebo or other active treatment.

SEARCH METHODS

Electronic databases (MEDLINE, EMBASE, DARE, CENTRAL, Hypertension Group specialised register) were searched up to January 2011. The reference lists of papers resulting from the electronic searches and abstracts from national and international cardiovascular meetings were hand-searched to identify missed or unpublished studies. Relevant authors of studies were contacted to obtain further data.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in patients with elevated blood pressure were included if they were of at least 3 months in duration and compared antithrombotic therapy with control or other active treatment.

DATA COLLECTION AND ANALYSIS

Data were independently collected and verified by two reviewers. Data from different trials were pooled where appropriate.

MAIN RESULTS

Four trials with a combined total of 44,012 patients met the inclusion criteria and are included in this review. Acetylsalicylic acid (ASA) did not reduce stroke or 'all cardiovascular events' compared to placebo in primary prevention patients with elevated blood pressure and no prior cardiovascular disease. In one large trial ASA taken for 5 years reduced myocardial infarction (ARR 0.5%, NNT 200), increased major haemorrhage (ARI 0.7%, NNT 154), and did not reduce all cause mortality or cardiovascular mortality. In one trial there was no significant difference between ASA and clopidogrel for the composite endpoint of stroke, myocardial infarction or vascular death. In two small trials warfarin alone or in combination with ASA did not reduce stroke or coronary events. The ATC meta-analysis of antiplatelet therapy for secondary prevention in patients with elevated blood pressure reported an absolute reduction in vascular events of 4.1% as compared to placebo. Data on the 10,600 patients with elevated blood pressure from the 29 individual trials included in the ATC meta-analysis was requested but could not be obtained.

AUTHORS' CONCLUSIONS

Antiplatelet therapy with ASA for primary prevention in patients with elevated blood pressure provides a benefit, reduction in myocardial infarction, which is negated by a harm of similar magnitude, increase in major haemorrhage.The benefit of antiplatelet therapy for secondary prevention in patients with elevated blood pressure is many times greater than the harm.Benefit has not been demonstrated for warfarin therapy alone or in combination with aspirin in patients with elevated blood pressure. Ticlopidine, clopidogrel and newer antiplatelet agents such as prasugrel and ticagrelor have not been sufficiently evaluated in patients with high blood pressure. Newer antithrombotic oral drugs such as dabigatran, rivaroxaban, apixaban and endosaban are yet to be tested in patients with high blood pressure.Further trials of antithrombotic therapy including with newer agents and complete documentation of all benefits and harms are required in patients with elevated blood pressure.

The Optimal Route of Administration of the Glycoprotein IIb/IIIa Receptor Antagonist Abciximab During Percutaneous Coronary Intervention; Intravenous Versus Intracoronary

The use of the glycoprotein (GP) IIb/IIIa receptor antagonist Abciximab has over the years become an important part of the anticoagulant regimen in patients with acute coronary syndrome undergoing percutaneous coronary intervention. Abciximab is a potent inhibitor of platelet aggregation and thrombus formation, but other mechanisms, such as suppression of the inflammatory pathways, have also been proposed to contribute to the benefits of Abciximab.

The optimal route of administration, i.e. intravenous versus intracoronary, of the first dose has been questioned, but only tested in small, non-randomised and retrospective studies or studies with short follow-up. No definite conclusion can be made based on these studies.

In this review we present the current knowledge published about the intracoronary administration of Abciximab including the mechanisms behind the potential beneficial effects, and the safety. The emphasis will be on clinical trials rather than on studies on the pharmacological mechanisms, as the latter have been reviewed thoroughly elsewhere.

Our conclusion from this present review is that randomized trials of intracoronary versus intravenous bolus of Abciximab are needed.

Glycoprotein IIb/IIIa inhibitors: an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy

The human glycoprotein (GP)IIb/IIIa belongs to a large family of cation-dependent adhesion molecules known as integrins, which share a common heterodimeric structure. The primary function of GPIIb/IIIa is to aid platelet aggregation by transmitting bidirectional signals across the plasma membrane. Since the GPIIb/IIIa receptor is among the key integrins involved in platelet aggregation and, therefore, thrombus formation, the development of GPIIb/IIIa antagonists (e.g., abciximab, eptifibatide and tirofiban) has become an attractive strategy for antiplatelet therapy with an expected strong and specific effect. All three drugs are administered intravenously, and large-scale clinical trials have demonstrated a clear clinical benefit and good safety profile in high-risk patients, especially those undergoing percutaneous coronary intervention. However, the adverse events related to thrombosis or bleeding are still reported in patients undergoing therapy with GPIIb/IIIa antagonists and reflect a variable interindividual responsiveness. Therefore, some form of laboratory monitoring is required to optimize the effects of a drug or to indicate that it needs replacing with other antithrombotic agents, as well as for identifying and enhancing the platelet inhibition in this subgroup of patients to improve the clinical outcome and reduce bleeding complications. As such, the aim of this article is to provide an update on the mechanism of action and use of functional testing methods to assess antiplatelet efficacy in patients undergoing therapy with GPIIb/IIIa antagonists.

Platelet pharmacogenomics

Platelet responsiveness to conventional antiplatelet therapy underlies a high interindividual variability influenced by various factors. For instance, antiplatelet therapy does not curtail the expected effects in a relevant number of patients as demonstrated by the occurrence of repeated cardiovascular events including stent thrombosis and/or by inadequate platelet inhibition measured by in vitro platelet function assays. Besides non-genetic factors such as age, gender, liver and renal function and co-medication, considerable variation of antiplatelet drug responsiveness can be attributed to genetic factors including polymorphisms and genetic variants of platelet surface proteins and drug metabolizing enzymes. Nowadays, platelet pharmacogenomics has started a new field with the goal to link genetic information of various drug targets to interindividual variability of drug response. Evolving data from large cohort studies suggest a promising role for pharmacogenomics in the context of antiplatelet therapy. Additionally, with the revolution of low cost and high-throughput genotyping techniques, genetic testing has become affordable for clinical application and individualization of therapy. However, a key issue to define the future role of pharmacogenomics will rely on the benefit and the timeliness of implementing the genetic information into therapeutic decision. Hence, it warrants further investigations to document the prognostic effects of therapeutic alterations in distinct genotypes. Concerning the safety profile of emerging antiplatelet and antithrombotic drugs in certain risk groups it would be fatal to individualize treatment barely on behalf of an atherothrombotic genotype. In contrast, individual risk assessment combining non-genetic information and pharmacogenetic analysis represents a reasonable concept. Here, we provide a review on current data describing the role of pharmacogenomics in the field of antiplatelet drug treatment in cardiovascular patients with future directions.

Pharmacogenetics in cardiovascular antithrombotic therapy

Thrombosis is the most important underlying mechanism of coronary artery disease and embolic stroke. Hence, antithrombotic therapy is widely used in these scenarios. However, not all patients achieve the same degree of benefit from antithrombotic agents, and a considerable number of treated patients will continue to experience a new thrombotic event. Such lack of clinical benefit may be related to a wide variability of responses to antithrombotic treatment among individuals (i.e., interindividual heterogeneity). Several factors have been identified in this interindividual heterogeneity in response to antithrombotic treatment. Pharmacogenetics has emerged as a field that identifies specific gene variants able to explain the variability in patient response to a given drug. Polymorphisms affecting the disposition, metabolism, transporters, or targets of a drug all can be implicated in the modification of an individual's antithrombotic drug response and therefore the safety and efficacy of the aforementioned drug. The present paper reviews the modulating role of different polymorphisms on individuals' responses to antithrombotic drugs commonly used in clinical practice.

Effect of an anti‐PDGF‐β‐receptor‐blocking antibody on restenosis in patients undergoing elective stent placement

AIM

The aim of the study was to determine whether a single intravenous infusion of 25 mg/kg CDP860, a humanized di-Fab' fragment against PDGF-beta receptor, leads to a reduction of in-stent restenosis.

METHODS

In this phase II, double-blind, placebo-controlled, multicentre study 145 patients presenting with stable or unstable angina were randomized to a single infusion of placebo or active drug (CDP860) before undergoing stenting. Quantitative angiography and 3D intravascular ultrasound (IVUS) were obtained at baseline and follow-up. Primary endpoint was the IVUS assessment of percentage in-stent volume obstruction.

RESULTS

At six-month follow-up, the placebo group and CDP860 group did not differ significantly regarding minimal luminal diameter (1.75 +/- 0.68 versus 1.82 +/--0.66 mm), restenosis rate (16.2 versus 14.1%), minimal lumen area (4.71 +/- 1.85 versus 4.41 +/- 1.77 mm(2) ), in-stent neointimal volume (30 +/- 23 versus 31 +/- 31 mm(3)) and in-stent obstruction volume (23.8 +/- 14.4 versus 22.1 +/- 15.3%). Major adverse cardiac events at 210 days were similar in both groups: death 1.5 versus 1.4%, myocardial infarction 5.9 versus 8.1% and target vessel revascularization 16.4 versus 17.6%.

CONCLUSION

A single intravenous administration of monoclonal antibody against PDGF-beta receptor failed to reduce the amount of neointimal hyperplasia after stent implantation.

Relation of periprocedural bleeding complications and long-term outcome in patients undergoing percutaneous coronary revascularization (from the Evaluation of Oral Xemilofiban in Controlling Thrombotic Events [EXCITE] Trial)

Several clinical trials have shown that antagonists of the glycoprotein IIb/IIIa receptor decreased the incidence of death, nonfatal myocardial infarction, and the need for urgent revascularization when administered immediately before or during the 24- to 48-hour period after percutaneous coronary intervention (PCI). However, these agents increased the risk of thrombocytopenia and periprocedural bleeding complications. Therefore, the relation between periprocedural bleeding complications during PCI and long-term outcome was assessed in 6,995 patients in the EXCITE trial. Periprocedural bleeding was classified as none, mild, moderate, and severe. Measured outcomes included the incidence of all-cause mortality or the composite end point (cardiovascular disease) of death, myocardial infarction, or stroke. Subjects were followed up for a median of 210 days (7 months). Mean patient age was 59.1 years, and 21.8% were women. Periprocedural bleeding complications occurred in 1,869 patients (26.7%), and blood transfusion was administered to 189 patients (2.7%). In multivariate analysis, periprocedural bleeding complications were significantly associated with increased risk of the composite outcome for mild (hazard ratio [HR] 0.80, 95% confidence interval [CI] 0.64 to 0.97), moderate (HR 2.38, 95% CI 1.78 to 3.20), and severe bleeding complications (HR 3.55, 95% CI 2.20 to 5.73) during follow-up. Also, the necessity of blood transfusion was an important predictor of the composite end point (HR 2.61, 95% CI 1.96 to 3.60). Patients in the United States were more likely to be administered a blood transfusion than non-US patients independently of cardiovascular risk factors. In conclusion, moderate and severe periprocedural bleeding complications increased the risk of mortality and incident cardiovascular events after PCI.

Learning from the recently completed oral glycoprotein IIb/IIIa receptor antagonist trials

Although parenteral therapy with glycoprotein (GP) IIb/IIIa inhibitors has resulted in a reduced risk of death or myocardial infarction in patients with acute coronary syndromes and in patients undergoing percutaneous coronary intervention, the benefit is achieved only during the infusion period. Oral GP IIb/IIIa inhibitors may offer an opportunity to expand the application of this therapy to additional vascular indications and to extend therapy beyond the in-hospital period. A number of oral GP IIb/IIIa inhibiting agents have been evaluated; however, no benefit has been observed. Oral GP IIb/IIIa inhibitors have been associated with an increased incidence of bleeding, but additional experience may permit the design of dosing regimens that decrease this risk. The recent Orbofiban in Patients with Unstable Coronary Syndromes (OPUS/TIMI-16) trial showed a small but significant increase in mortality in orbofiban-treated patients. It appears that this agent, and perhaps other oral GP IIb/IIIa inhibitors including sibrafiban and xemilofiban, may have a pro-aggregatory effect. This may be caused by the drug dissociating from the GP IIb/IIIa receptor, leaving an activated receptor that can then bind fibrinogen and form a platelet aggregate. Further studies are needed to elucidate the mechanism of this effect and to evaluate whether the second-generation of oral GP IIb/IIIa inhibitors, which have tight binding and a longer duration of antiplatelet effect, will be of clinical benefit.

Optimizing antiplatelet therapy in coronary interventions

Percutaneous coronary intervention has had a dramatic impact on the current practice of cardiology. One of its important limitations, however, is the potential for producing unfavorable outcomes such as acute coronary closure following angioplasty or atherectomy or subacute thrombosis following stent implantation. These complications may lead to death, myocardial infarction, or the need for urgent bypass surgery. One mechanism underlying these clinical events is platelet-mediated thrombosis due to arterial trauma. Therapeutically, platelet activation by thromboxane and adenosine diphosphate (ADP), as well as platelet aggregation by glycoprotein IIb/IIIa (GPIIb/IIIa) receptors, has been inhibited with various pharmacologic agents. c7E3 (abciximab), a monoclonal antibody directed against GPIIb/IIIa, has been shown to have potent effects on reducing both acute and subacute complications. Other parenteral GPIIb/IIIa inhibitors, including peptide and small nonpeptide molecules, have also been found to be clinically effective. Oral versions of similar drugs are currently being evaluated, but several have resulted in disappointing efficacy and safety profiles and have failed to show advantages over aspirin. With all antiplatelet agents, in particular GPIIb/IIIa receptor inhibitors, bleeding and vascular complications must be addressed. Inhibition of thromboxane-induced platelet activation with aspirin has been standard therapy for angioplasty and in the global management of vascular disease. Newer agents that block ADP-mediated platelet activation, the thienopyridines, have been found to be synergistic to aspirin in their effects on the complications of coronary intervention. Ticlopidine and, more recently, clopidogrel, in conjunction with aspirin, have become standard therapies for preventing subacute thrombosis after stent implantation. Large-scale clinical trials are ongoing to optimize their use in combination with GPIIb/IIIa inhibitors.

Usefulness of proteinuria as a prognostic marker of mortality and cardiovascular events among patients undergoing percutaneous coronary intervention (data from the Evaluation of Oral Xemilofiban in Controlling Thrombotic Events [EXCITE] trial)

Proteinuria was associated with cardiovascular events and mortality in community-based cohorts. The association of proteinuria with mortality and cardiovascular events in patients undergoing percutaneous coronary intervention (PCI) was unknown. The association of urinary dipstick proteinuria with mortality and cardiovascular events (composite of death, myocardial infarction, or nonhemorrhagic stroke) in 5,835 subjects of the EXCITE trial was evaluated. Dipstick urinalysis was performed before PCI, and proteinuria was defined as trace or greater. Subjects were followed up for 210 days/7 months after enrollment for the occurrence of events. Multivariate Cox regression analysis evaluated the independent association of proteinuria with each outcome. Mean age was 59 years, 21% were women, 18% had diabetes mellitus, and mean estimated glomerular filtration rate was 90 ml/min/1.73 m(2). Proteinuria was present in 750 patients (13%). During follow-up, 22 subjects (2.9%) with proteinuria and 54 subjects (1.1%) without proteinuria died (adjusted hazard ratio 2.83, 95% confidence interval [CI] 1.65 to 4.84, p <0.001). The severity of proteinuria attenuated the strength of the association with mortality after PCI (low-grade proteinuria, hazard ratio 2.67, 95% CI 1.50 to 4.75; high-grade proteinuria, hazard ratio 3.76, 95% CI 1.24 to 11.37). No significant association was present for cardiovascular events during the relatively short follow-up, but high-grade proteinuria tended toward increased risk of cardiovascular events (hazard ratio 1.45, 95% CI 0.81 to 2.61).In conclusion, proteinuria was strongly and independently associated with mortality in patients undergoing PCI. These data suggest that such a relatively simple and clinically easy to use tool as urinary dipstick may be useful to identify and treat patients at high risk of mortality at the time of PCI.

Clinical aspects of platelet inhibitors and thrombus formation

The platelet, once thought to be solely involved in clot formation, is now known to be a key mediator in various others processes such as inflammation, thrombosis, and atherosclerosis. Supported by the wealth of evidence from clinical trials demonstrating their benefits in patient outcomes, antiplatelet agents have become paramount in the prevention and management of various diseases involving the cardiovascular, cerebrovascular, and peripheral arterial systems. Despite being among the most widely used and studied classes of medical therapies, new discoveries regarding important clinical aspects and properties of these agents continue to be made. As our understanding of platelet biology expands, more effective and safer novel therapies continue to be developed. The use of more refined agents in conjunction with a better understanding of their effects will further the ability to provide more optimized care on an individual basis.

Current developments in anti-platelet therapy

Platelets play a life-saving role in hemostasis and blood clotting at sites of vascular injury and consequently are similarly involved in the pathological counterpart, namely thrombosis. Thus, anti-platelet therapy has become a mainstay in treatment and/or prophylaxis of conditions like myocardial infarction, stroke and other cardiovascular diseases. Acetyl-salicylic acid (ASA, aspirin) is still the most widely used agent and considered as the prototype antiplatelet drug. Since platelet activation occurs via several pathways that are not influenced by ASA, several other compounds have been developed to add to its beneficial effect. Currently four main classes of antiplatelet agents are available for clinical use: acetyl-salicylic acid (ASA), phosphodiesterase (PDE) inhibitors, thienopyridines and the intravenous GPIIb/IIIa antagonists. This article gives a concise review of these four classes of anti-platelet agents, using ASA as the reference standard.

PubMed vs. HighWire Press: a head-to-head comparison of two medical literature search engines

PubMed and HighWire Press are both useful medical literature search engines available for free to anyone on the internet. We measured retrieval accuracy, number of results generated, retrieval speed, features and search tools on HighWire Press and PubMed using the quick search features of each. We found that using HighWire Press resulted in a higher likelihood of retrieving the desired article and higher number of search results than the same search on PubMed. PubMed was faster than HighWire Press in delivering search results regardless of search settings. There are considerable differences in search features between these two search engines.

Oral platelet glycoprotein IIb/IIIa receptor inhibitors--Part I

With the central importance of antiplatelet therapy in patients with coronary artery disease and the numerous positive trials with glycoprotein (GP) IIb/IIa inhibitors given intravenously, it was hoped that one could extend the benefit of IIb/IIIa inhibition to long-term treatment. Although the hypothesis that prolonged oral IIb/IIIa inhibition was appealing, many issues have been identified in the initial Phase II trials that would limit the usefulness of these compounds. Variability of the level of platelet inhibition was one major culprit that distinguished the oral compounds from intravenous ones. The problems that arose were that increased bleeding has been seen when levels of platelet inhibition are high (e.g., > 90%) and that, conversely, efficacy would likely be limited when levels of platelet inhibition were low. If further development of this class of drugs is undertaken, formal dosing studies would have to establish an oral dosing strategy that achieves appropriately high (80-95% inhibition) and steady levels of inhibition.

The exclusion of patients with chronic kidney disease from clinical trials in coronary artery disease

Chronic kidney disease (CKD) is associated with a high risk of death from coronary artery disease and may modify the response to standard cardiovascular therapies. Treatment of subjects with CKD should ideally be based on evidence from randomized, clinical trials, but how often subjects with CKD have been excluded from these trials is uncertain. We undertook this study in order to quantify how often subjects with moderate to advanced CKD were excluded from large cardiovascular trials. MEDLINE and the reference list of selected articles were searched in order to identify large, randomized, controlled trials of five different coronary artery disease therapies published between 1998 and 2005. Exclusion criteria and reported clinical characteristics of subjects were abstracted. Rates of exclusion and reporting of baseline characteristics of study participants were compared for CKD, diabetes, history of smoking, and hypertension. Eighty-six trials randomizing 411 653 patients were identified. More than 80% of trials excluded subjects with end-stage renal disease and 75.0% excluded patients with CKD. Subjects with diabetes, hypertension, or a history of smoking were excluded less than 4% of the time. Baseline renal function of study participant was reported in only 7% of trials. Patients with CKD are frequently excluded from coronary artery disease trials and renal function of randomized subjects is rarely reported. These findings reinforce the notion that available data on the treatment of coronary artery disease in subjects with CKD have significant limitations and should be generalized to the treatment of subjects with CKD cautiously.