Do anticoagulant and antiplatelet agents prevent acute graft thrombosis in renal transplantation? A meta-analysis of case series studies

Introduction & Objectives: Thrombosis of the renal allograft is expected to occur in 1–6% of kidney transplants, and graft loss is expected in almost all cases. Anticoagulant and anti-platelet agents could serve as an adjunctive preventive measure, but sound evidence of benefits are still lacking, in this setting. We therefore assessed the efficacy and safety of anticoagulant and anti-platelet agents, in reducing the rate of renal allograft thrombosis. Methods: A review of the literature was carried out in major databases (MEDLINE, EMBASE and LILACS), with a comprehensive search strategy, to locate all available case series studies of anticoagulant and/or anti-platelet prophylaxis of thrombosis in renal transplantation. The date of the last search was 11 August 2014. We pooled all case series in a proportional meta-analysis. Statistical significance was achieved if the 95% confidence intervals obtained for each intervention did not overlap. Results: Our search strategy retrieved 7160 titles, from which 21 case series were chosen for analysis. A total of 3246 patients were identified (1718 treated with antiplatelet and/or anticoagulant agents, and 1528 non-treated control subjects). Allograft thrombosis occurred in 7.24% (95% CI 3.45 to 12.27%) of the patients receiving no intervention, compared to 3.38% (95% CI 1.45 to 6.1%), 1.2% (95% CI 0.6 to 2.1%) and 0.47% (95% CI 0.001 to 1.79%), in the anticoagulant, aspirin, and aspirin + anticoagulant groups, respectively. Bleeding complication rates were 28.0% (95% CI 15.4 to 42.7%) for anticoagulants, compared to 12.13% (95% CI 0.8 to 33.93%) for aspirin + anticoagulant, 0.31% (95% CI 0.0001 to 1.32%) for aspirin, and 6.1% (95% CI 2.2 to 11.7%) for the control group. Conclusions: Aspirin is more effective in reducing allograft thrombosis, after kidney transplantation, whether alone or in association with an anticoagulant, when compared to no drug prophylaxis, and without higher haemorrhagic complication rates. Anticoagulants, when used alone, do not show a beneficial effect on thrombosis rates, additionally yielding higher bleeding rates.

Perioperative antiplatelet therapy.

Aspirin is recommended as a lifelong therapy that should never be interrupted for patients with cardiovascular dis- ease. Clopidogrel therapy is mandatory for six weeks after placement of bare-metal stents, three to six months after myocardial infarction, and at least 12 months after placement of drug-eluting stents. Because of the hypercoagulable state induced by surgery, early withdrawal of antiplatelet therapy for secondary prevention of cardiovascular disease increases the risk of postoperative myocardial infarction and death five- to 10-fold in stented patients who are on continuous dual antiplatelet therapy. The shorter the time between revascularization and surgery, the higher the risk of adverse cardiac events. Elective surgery should be postponed beyond these periods, whereas vital, semiurgent, or urgent operations should be performed under continued dual antiplatelet therapy. The risk of surgical hemorrhage is increased approximately 20 percent by aspirin or clopidogrel alone, and 50 percent by dual antiplatelet therapy. The present clinical data suggest that the risk of a cardiovascular event when stopping antiplatelet agents preoperatively is higher than the risk of surgical bleeding when continuing these drugs, except during surgery in a closed space (e.g., intracranial, posterior eye chamber) or surgeries associated with massive bleeding and difficult hemostasis.

Antiplatelet therapy for secondary prevention of coronary artery disease.

The choice and duration of antiplatelet therapy for secondary prevention of coronary artery disease (CAD) is determined by the clinical context and treatment strategy. Oral antiplatelet agents for secondary prevention include the cyclo-oxygenase-1 inhibitor aspirin, and the ADP dependent P2Y12 inhibitors clopidogrel, prasugrel and ticagrelor. Aspirin constitutes the cornerstone in secondary prevention of CAD and is complemented by clopidogrel in patients with stable CAD undergoing percutaneous coronary intervention. Among patients with acute coronary syndrome, prasugrel and ticagrelor improve net clinical outcome by reducing ischaemic adverse events at the expense of an increased risk of bleeding as compared with clopidogrel. Prasugrel appears particularly effective among patients with ST elevation myocardial infarction to reduce the risk of stent thrombosis compared with clopidogrel, and offered a greater net clinical benefit among patients with diabetes compared with patients without diabetes. Ticagrelor is associated with reduced mortality without increasing the rate of coronary artery bypass graft (CABG)-related bleeding as compared with clopidogrel. Dual antiplatelet therapy should be continued for a minimum of 1 year among patients with acute coronary syndrome irrespective of stent type; among patients with stable CAD treated with new generation drug-eluting stents, available data suggest no benefit to prolong antiplatelet treatment beyond 6 months.

Republished: Antiplatelet therapy for secondary prevention of coronary artery disease

The choice and duration of antiplatelet therapy for secondary prevention of coronary artery disease (CAD) is determined by the clinical context and treatment strategy. Oral antiplatelet agents for secondary prevention include the cyclo-oxygenase-1 inhibitor aspirin, and the ADP dependent P2Y12 inhibitors clopidogrel, prasugrel and ticagrelor. Aspirin constitutes the cornerstone in secondary prevention of CAD and is complemented by clopidogrel in patients with stable CAD undergoing percutaneous coronary intervention. Among patients with acute coronary syndrome, prasugrel and ticagrelor improve net clinical outcome by reducing ischaemic adverse events at the expense of an increased risk of bleeding as compared with clopidogrel. Prasugrel appears particularly effective among patients with ST elevation myocardial infarction to reduce the risk of stent thrombosis compared with clopidogrel, and offered a greater net clinical benefit among patients with diabetes compared with patients without diabetes. Ticagrelor is associated with reduced mortality without increasing the rate of coronary artery bypass graft (CABG)-related bleeding as compared with clopidogrel. Dual antiplatelet therapy should be continued for a minimum of 1 year among patients with acute coronary syndrome irrespective of stent type; among patients with stable CAD treated with new generation drug-eluting stents, available data suggest no benefit to prolong antiplatelet treatment beyond 6 months.

A randomised controlled trial of triple antiplatelet therapy (Aspirin, Clopidogrel and Dipyridamole) in the secondary prevention of stroke: safety, tolerability and feasibility

Background: Aspirin, dipyridamole and clopidogrel are effective in secondary vascular prevention. Combination therapy with three antiplatelet agents might maximise the benefit of antiplatelet treatment in the secondary prevention of ischaemic stroke. Methodology/Principal Findings: A randomised, parallel group, observer-blinded phase II trial compared the combination of aspirin, clopidogrel and dipyridamole with aspirin alone. Adult patients with ischaemic stroke or transient ischaemic attack (TIA) within 5 years were included. The primary outcome was tolerability to treatment assessed as the number of patients completing randomised treatment. Recruitment was halted prematurely after publication of the ESPRIT trial (which confirmed that combined aspirin and dipyridamole is more effective than aspirin alone). 17 patients were enrolled: male 12 (71%), mean age 62 (SD 13) years, lacunar stroke syndrome 12 (71%), median stroke/TIA onset to randomisation 8 months. Treatment was discontinued in 4 of 9 (44%) patients receiving triple therapy vs. none of 8 taking aspirin (p = 0.08). One recurrent stroke occurred in a patient in the triple group who was noncompliant of all antiplatelet medications. The number of patients with adverse events and bleeding complications, and their severity, were significantly greater in the triple therapy group (p,0.01). Conclusions/Significance: Long term triple antiplatelet therapy was asociated with a significant increase in adverse events and bleeding rates, and their severity, and a trend to increased discontinuations. However, the patients had a low risk of recurrence and future trials should focus on short term therapy in high risk patients characterised by a very recent event or failure of dual antiplatelet therapy.

Évaluation pré-clinique et clinique de deux nouvelles stratégies dans le traitement des maladies cardiovasculaires : activité anti-thrombotique de l'inhibition du récepteur P2Y1 et activité anti-inflammatoire de l'inhibition du récepteur PAR-1.

Alors que la plaquette a un rôle prépondérant dans le maintient de l'hémostase, son implication dans la formation de la thrombose est également incontestée. Il existe à présent des traitements antiplaquettaires mais ceux-ci présentent quelques failles. Le but de ma maîtrise a donc été de caractériser de nouvelles voies d'inhibition de l'activité plaquettaire. Les deux études qui ont été réalisées concernent l'inhibition de récepteurs couplés aux protéines G, soit le récepteur à l'ADP P2Y1 et le récepteur à la thrombine PAR-1. Dans un premier temps, l'étude du récepteur P2Y1 suggère que l'inhibition de celui-ci seul ou en combinaison avec l'inhibition du récepteur P2Y12 présente un potentiel thérapeutique chez des patients coronariens stables. Dans un deuxième temps, l'étude d'un nouvel antiplaquettaire qui est présentement en phase III de son développement clinique, soit le SCH 530348, a été effectuée. Étant un antagoniste du récepteur PAR-1, le SCH 530348 a des effets qui se répercutent à la fois chez la plaquette et les leucocytes qui possèdent eux aussi ce récepteur. Cette deuxième étude suggère que complémentairement à son effet chez la plaquette, cet inhibiteur diminue les marqueurs de l'inflammation systémique.

Prevalencia de resistencia plaquetaria a clopidogrel en pacientes sometidos a intervencion coronaria percutanea

Los agentes antiplaquetarios son el principal tratamiento para pacientes con síndromes coronarios agudos, han demostrado reducción en el riesgo de muerte, infarto del miocardio, y necesidad de revascularización urgente. Algunos pacientes presentan eventos cardiacos mayores a pesar de recibir estos medicamentos. El impacto de la resistencia a los medicamentos ha sido material de múltiples estudios. En Colombia no existen estadísticas sobre la resistencia al Clopidogrel.En nuestro estudio la prevalencia de resistencia a Clopidogrel por el método de agregometria plaquetaria por transferencia de luz con muestras tomadas entre el día 7 y el 10 post angioplastia, está por encima del promedio internacional en nuestra población, lo que amerita la realización de nuevos estudios por las implicaciones pronosticas que pudieran tener en términos de eventos cardiovasculares adversos.

Investigating flavonoids as molecular templates for the design of small-molecule inhibitors of cell signaling

Epidemiological and clinical trials reveal compelling evidence for the ability of dietary flavonoids to lower cardiovascular disease risk. The mechanisms of action of these polyphenolic compounds are diverse, and of particular interest is their ability to function as protein and lipid kinase inhibitors. We have previously described structure-activity studies that reinforce the possibility for using flavonoid structures as templates for drug design. In the present study, we aim to begin constructing rational screening strategies for exploiting these compounds as templates for the design of clinically relevant, antiplatelet agents. We used the platelet as a model system to dissect the structural influence of flavonoids, stilbenes, anthocyanidins, and phenolic acids on inhibition of cell signaling and function. Functional groups identified as relevant for potent inhibition of platelet function included at least 2 benzene rings, a hydroxylated B ring, a planar C ring, a C ring ketone group, and a C-2 positioned B ring. Hydroxylation of the B ring with either a catechol group or a single C-4' hydroxyl may be required for efficient inhibition of collagen-stimulated tyrosine phosphorylated proteins of 125 to 130 kDa, but may not be necessary for that of phosphotyrosine proteins at approximately 29 kDa. The removal of the C ring C-3 hydroxyl together with a hydroxylated B ring (apigenin) may confer selectivity for 37 to 38 kDa phosphotyrosine proteins. We conclude that this study may form the basis for construction of maps of flavonoid inhibitory activity on kinase targets that may allow a multitargeted therapeutic approach with analogue counterparts and parent compounds.

Discovery of novel GPVI receptor antagonists by structure-based repurposing.

Inappropriate platelet aggregation creates a cardiovascular risk that is largely managed with thienopyridines and aspirin. Although effective, these drugs carry risks of increased bleeding and drug 'resistance', underpinning a drive for new antiplatelet agents. To discover such drugs, one strategy is to identify a suitable druggable target and then find small molecules that modulate it. A good and unexploited target is the platelet collagen receptor, GPVI, which promotes thrombus formation. To identify inhibitors of GPVI that are safe and bioavailable, we docked a FDA-approved drug library into the GPVI collagen-binding site in silico. We now report that losartan and cinanserin inhibit GPVI-mediated platelet activation in a selective, competitive and dose-dependent manner. This mechanism of action likely underpins the cardioprotective effects of losartan that could not be ascribed to its antihypertensive effects. We have, therefore, identified small molecule inhibitors of GPVI-mediated platelet activation, and also demonstrated the utility of structure-based repurposing.

Planejamento, síntese e avaliação farmacológica de novos compostos 1,2,5-oxadiazol-2-n-óxido úteis como preventivos de aterotrombose

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Increased clopidogrel response is associated with ABCC3 expression: A pilot study

Background: The aim of this study was investigate the relationship between ABCB1 and ABCC3 gene expressions in peripheral blood cells (PBC) and the response to clopidogrel in patients with coronary arterial disease (CAD). Methods: Twenty-six male CAD patients (50-70 years) under treatment with clopidogrel (75 mg/day) for at least 5 days were selected. Blood samples were obtained to evaluate platelet reactivity and ABCB1 and ABCC3 mRNA expression. Platelet reactivity was measured in P2Y12 Reaction Units (PRU) using VerifyNow. RNA was extracted from PBC and mRNA levels were measured by qPCR, using GAPD as a reference gene. Results: Platelet response to clopidogrel was categorized in to PRU quartiles. Individuals with PRU values within the first quartile (Q1, <151 units) were considered good responders, while those who had PRU within the fourth quartile (Q4. PRU>260) were considered non-responders. ABCC3 was 1.7 times more expressed in Q4 than in Q1 PRU group (p=0.048). Moreover, CAD patients with low ABCC3 expression (Qe1, <2.5x10(-3)) had higher probability to have a good response to clopidogrel (OR: 18.00, 95%CI: 1.90-169.99, p=0.001). Univariate linear regression analysis demonstrated that low ABCC3 mRNA expression contributed with a reduction of 73 PRU in relation to the patients with expression value higher than 2.5x10(-3) (p=0.027). Neither ABCB1 mRNA levels nor clinical variables studied influenced PRU values. Conclusions: Low ABCC3 mRNA expression in peripheral blood cells is associated with increased clopidogrel response, but further studies are needed to describe the functional relationship of clopidogrel with the ABCC3. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.

Randomized clinical trial comparing percutaneous closure of patent foramen ovale (PFO) using the Amplatzer PFO Occluder with medical treatment in patients with cryptogenic embolism (PC-Trial): rationale and design

Background Several studies have shown an association of cryptogenic stroke and embolism with patent foramen ovale (PFO), but the question how to prevent further events in such patients is unresolved. Options include antithrombotic treatment with warfarin or antiplatelet agents or surgical or endovascular closure of the PFO. The PC-Trial was set up to compare endovascular closure and best medical treatment for prevention of recurrent events. Methods The PC-Trial is a randomized clinical trial comparing the efficacy of percutaneous closure of the PFO using the Amplatzer PFO occluder with best medical treatment in patients with cryptogenic embolism, i.e. mostly cryptogenic stroke. Warfarin for 6 months followed by antiplatelet agents is recommended as medical treatment. Randomization is stratified according to patients age (<45 versus ≥45 years), presence of atrial septal aneurysm (ASA yes or no) and number of embolic events before randomization (one versus more than one event). Primary endpoints are death, nonfatal stroke and peripheral embolism. Discussion patients were randomized in 29 centers of Europe, Canada, and Australia. Randomization started February 2000. Enrollment of 414 patients was completed in February 2009. All patients will be followed-up longitudinally. Follow-up is maintained until the last enrolled patient is beyond 2.5 years of follow-up (expected in 2011).

Secondary stroke prevention: patent foramen ovale, aortic plaque, and carotid stenosis

Stroke is the most debilitating cardiovascular event. It has a variety of causes that may be present simultaneously. In young or otherwise healthy people, the search for a patent foramen ovale (PFO) has become standard. In stroke of the elderly, atherosclerosis and atrial fibrillation are in the foreground but the PFO should not be ignored. The risk of a PFO-related stroke over time is controversial and so is its prevention by device closure. The association of proximal aortic plaques in arteries subtending the brain and stroke is considered strong, ignoring that it is as putative as that of the PFO. Statins can prevent progression of such plaques. Antiplatelet agents in asymptomatic and surgical endarterectomy in symptomatic patients or highly ulcerated lesions are the treatment of choice. Stenting with protection devices was shown competitive in selected patients.

Impact of atrial fibrillation on clinical outcomes among patients with coronary artery disease undergoing revascularisation with drug-eluting stents

Coronary artery disease (CAD) and atrial fibrillation (AF) are major determinants of morbidity and mortality. A combined treatment with antiplatelet agents and vitamin K antagonists limits the risk of stent thrombosis and stroke while increasing the rate of bleeding. The objective of this study was to investigate the impact of atrial fibrillation (AF) on long-term clinical outcomes in patients with CAD undergoing percutaneous coronary intervention (PCI) with drug-eluting stents (DES).