Antiplatelet effects of prasugrel vs. double clopidogrel in patients on hemodialysis and with high on-treatment platelet reactivity

Antiplatelet Therapy in End-stage Renal Disease Patients on Maintenance Dialysis: a State-of-the-art Review

Patients with end-stage renal disease (ESRD) on maintenance dialysis have an increased risk of ischaemic events, such as recurrent myocardial infarction (MI) and stroke. Potent antiplatelet therapy may help mitigate this risk. Nonetheless, ERSD patients are also at increased risk of bleeding due to their complex vascular milieu, which limits the routine use of potent P2Y12 inhibitors. Moreover, these patients are often underrepresented or excluded from major clinical trials leaving a significant gap in existing knowledge. Understanding the mechanisms of this paradox may serve as a benchmark for the development of ESRD trials. The present review aims to provide an overview of the pathophysiological nature of increased bleeding and ischaemic risks in ERSD patients as well as summarize available evidence of antiplatelet use and propose new concepts to guide physicians in selecting appropriate drug regimes for this high-risk cohort.

[Heart and diabetes : Platelet function and antiplatelet therapy in chronic kidney disease]

Patients with chronic kidney disease (CKD) have an increased risk of thrombosis and approximately 50% of patients with advanced CKD die because of a cardiovascular disease. In addition to an increased risk of thrombosis, patients with CKD and particularly with advanced CKD, have an increased risk of hemorrhage, which increases parallel to the decline of kidney function. Due to this parallel existence of the prohemorrhagic and prothrombotic phenotype, antiplatelet treatment is difficult in the daily routine and data show that CKD patients with acute coronary syndrome (ACS) are less likely to receive guideline-conform treatment. The underlying mechanisms are currently insufficiently understood and both platelet-dependent mechanisms and also platelet-independent mechanisms are under discussion. Accordingly, there is currently no specific treatment or treatment strategy for patients with CKD. In addition, CKD patients are underrepresented in registration studies on antiplatelet treatment and there are no data from randomized trials for patients with advanced CKD (CKD ≥ 4). Current guideline recommendations are therefore based on subgroup analyses and observational studies. In addition, questions on the duration of treatment, on risk scores for estimation of the risk of hemorrhage and on potential benefits of escalation and de-escalation strategies remain largely unanswered and should therefore be the focus of future studies.

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.

The use of point-of-care testing in detecting platelet function recovery in a patient treated with prasugrel undergoing urgent surgical revascularization

A recent administration of potent P2Y₁₂ receptor inhibitor such as prasugrel in patients undergoing cardiac surgery remains a dilemma and little is known about its impact on platelet function recovery. Guidelines recommend discontinuation of prasugrel 7 days before surgery to reduce the risk of surgery-related bleeding. Patients at risk may benefit from preoperative platelet function testing to guide individualized preoperative waiting time. We present a rare case of complete function recovery in a patient treated with prasugrel revealed by preoperative platelet function monitoring before urgent coronary artery bypass surgery (CABG). A complete platelet function recovery was revealed by platelet function testing after discontinuation of prasugrel for four days and patient underwent urgent CABG without increased risk of postoperative bleeding. Our case with a review of literature emphasized that the decision to proceed with urgent CABG in a patient recently treated with prasugrel should be based on a personalized risk assessment and might be supported by preoperative platelet function monitoring to shorten the waiting time.

Medical adjuvant treatment to increase patency of arteriovenous fistulae and grafts

BACKGROUND

People with end-stage renal disease (ESRD) often require either the formation of an arteriovenous fistula (AVF) or an interposition prosthetic arteriovenous graft (AVG) for haemodialysis. These access sites should ideally have a long life and a low rate of complications (e.g. thrombosis, infection, stenosis, aneurysm formation and distal limb ischaemia). Although some of the complications may be unavoidable, any adjuvant technique or medical treatment aimed at decreasing complications would be welcome. This is the fourth update of the review first published in 2003.

OBJECTIVES

To assess the effects of adjuvant drug treatment in people with ESRD on haemodialysis via autologous AVFs or prosthetic interposition AVGs.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL databases and ClinicalTrials.gov trials register to 6 August 2020.

SELECTION CRITERIA

Randomised controlled trials of active drug versus placebo in people with ESRD undergoing haemodialysis via an AVF or prosthetic interposition AVG.

DATA COLLECTION AND ANALYSIS

For this update, two review authors (IM, MFAK) independently selected trials for inclusion, extracted data, assessed risk of bias and assessed the certainty of the evidence according to GRADE. We resolved disagreements by discussion or consultation with another review author (ADS). The primary outcome was the long-term fistula or graft patency rate. Secondary outcomes included duration of hospital stay; complications such as infection, aneurysm formation, stenosis and distal limb ischaemia; and number of related surgical or radiological interventions.

MAIN RESULTS

For this update, one additional study was suitable for inclusion, making a total of 13 trials with 2080 participants. Overall the certainty of the evidence was low or moderate due to short follow-up periods, heterogeneity between trials, small sample sizes, and risk of bias due to incomplete reporting. Medical adjuvant treatments used in the included trials were aspirin, ticlopidine, dipyridamole, dipyridamole plus aspirin, warfarin, fish oil, clopidogrel, sulphinpyrazone and glyceryl trinitrate (GTN) patch.  All included studies reported on graft patency by measuring graft thrombosis. There was insufficient evidence to determine if there was a difference in graft patency in studies comparing aspirin versus placebo (odds ratio (OR) 0.40, 95% confidence interval (CI) 0.07 to 2.25; 3 studies, 175 participants; low-certainty evidence). The meta-analysis for graft patency comparing ticlopidine versus placebo favoured ticlopidine (OR 0.45, 95% CI 0.25 to 0.82; 3 studies, 339 participants; moderate-certainty evidence). There was insufficient evidence to determine if there was a difference in graft patency in studies comparing fish oil versus placebo (OR 0.24, 95% CI 0.03 to 1.95; 2 studies, 220 participants; low-certainty evidence); and studies comparing clopidogrel and placebo (OR 0.40, 95% CI 0.13 to 1.19; 2 studies, 959 participants; moderate-certainty evidence). Similarly, there was insufficient evidence to determine if there was a difference in graft patency comparing the effect of dipyridamole versus placebo (OR 0.46, 95% CI 0.11 to 1.94; 1 study, 42 participants, moderate-certainty evidence) and dipyridamole plus aspirin versus placebo (OR 0.64, CI 0.16 to 2.56; 1 study, 41 participants; moderate-certainty evidence); comparing low-intensity warfarin with placebo (OR 1.76, 95% CI 0.78 to 3.99; 1 study, 107 participants; low-certainty evidence); comparing sulphinpyrazone versus placebo (OR 0.43, 95% CI 0.03 to 5.98; 1 study, 16 participants; low-certainty evidence) and comparing GTN patch and placebo (OR 1.26, 95% CI 0.63 to 2.54; 1 study, 167 participants; moderate-certainty evidence). The single trial evaluating warfarin was terminated early because of major bleeding events in the warfarin group. Only two studies published data on the secondary outcome of related interventions (surgical or radiological); there was insufficient evidence to determine if there was a difference in related interventions between placebo and treatment groups. None of the included studies reported on the duration of hospital stay.  Most studies reported complications ranging from mortality to nausea. However, data on complications were limited and reporting varied between studies.

AUTHORS' CONCLUSIONS

The meta-analyses of three studies for ticlopidine (an antiplatelet treatment), which all used the same dose of treatment but with a short follow-up of only one month, suggest ticlopidine may have a beneficial effect as an adjuvant treatment to increase the patency of AVFs and AVGs in the short term. There was insufficient evidence to determine if there was a difference in graft patency between placebo and other treatments such as aspirin, fish oil, clopidogrel, dipyridamole, dipyridamole plus aspirin, warfarin, sulphinpyrazone and GTN patch. The certainty of the evidence was low to moderate due to short follow-up periods, the small number of studies for each comparison, small sample sizes, heterogeneity between trials and risk of bias due to incomplete reporting. Therefore, it appears reasonable to suggest further prospective studies be undertaken to assess the use of these antiplatelet drugs in renal patients with an AVF or AVG.

Comparative efficacy and safety of oral P2Y12 inhibitors for patients with chronic kidney disease and acute coronary syndrome: a network meta-analysis

BACKGROUND

Currently, there is a paucity of data concerning the safety and effectiveness of P2Y₁₂ inhibitors in the acute coronary syndrome (ACS) with chronic kidney disease (CKD) population. The aim of this study is to compare the different oral P2Y₁₂ inhibitors in terms of efficacy and safety, focusing exclusively on patients with CKD who were treated for ACS.

METHODS

We systematically searched PubMed, CENTRAL, and Web of Science to identify studies that compared different oral P2Y₁₂ inhibitors (clopidogrel, prasugrel, and ticagrelor) in patients with ACS with CKD. Efficacy outcomes included the major adverse cardiovascular events composite outcome and safety outcomes included major bleedings and major or minor bleedings combined. We performed a frequentist network meta-analysis.

RESULTS

Twelve studies were included in the systematic review, 7 CKD subgroup analyses of RCTs (8878 patients) and 5 observational studies (20175 patients). After the exclusion of studies with conservative management, prasugrel resulted in significant primary endpoint reduction versus clopidogrel (HR 0.80 and 95% CI 0.64 - 0.99), while ticagrelor did not (HR 0.88 and 95% CI 0.73 - 1.06). Major bleedings did not differ between the interventions. Ticagrelor resulted in more major or minor bleedings than clopidogrel (HR 1.21 and 95% CI 1.06 - 1.38), whereas prasugrel did not (HR 1.12 and 95% CI 0.84 - 1.49).

CONCLUSION

In patients with ACS with underlying CKD, who are intended to receive invasive management, there may be a significant reduction of the primary efficacy outcome with prasugrel as compared to clopidogrel but not with ticagrelor as compared to clopidogrel. There probably exists no difference among interventions in the major bleedings. Dedicated RCTs are needed to confirm these results.

P2Y12 Antiplatelet Choice for Patients with Chronic Kidney Disease and Acute Coronary Syndrome: A Systematic Review and Meta-Analysis

This study aims to evaluate potentially appropriate antiplatelet therapy in patients with chronic kidney disease. A systematic analysis was conducted to identify the clinical outcomes of available antiplatelet therapy regimens with enhanced platelet inhibition activity (intervention of 5 regimens) over the standard dose of clopidogrel-based dual antiplatelet therapy in patients with renal insufficiency. An electronic keyword search was performed on Pubmed, Embase, and Cochrane Library per PRISMA guidelines. We performed a prespecified net clinical benefit analysis (a composite of the rates of all-cause or cardiac-related death, myocardial infarction, major adverse cardiac outcomes, and minor and major bleeding), and included 12 studies. The intervention substantially lowered the incidence of all-cause mortality (RR 0.67; p = 0.003), major adverse cardiac outcomes (RR 0.79; p < 0.00001), and myocardial infarction (RR 0.28; p = 0.00007) without major bleeding (RR 1.14; p = 0.33) in patients with renal insufficiency, but no significant differences were noticed with cardiac-related mortality and stent thrombosis. The subgroup analysis revealed substantially elevated bleeding risk in patients with severe renal insufficiency or on hemodialysis (RR 1.68; p = 0.002). Our study confirmed that the intervention considerably enhances clinical outcomes in patients with renal insufficiency, however, a standard dose of clopidogrel-based antiplatelet therapy is favorable in patients with severe renal insufficiency.

Stratified Approaches to Antiplatelet Therapies Based on Platelet Reactivity Testing

Antiplatelet therapy with P2Y₁₂ receptor inhibitors (clopidogrel, prasugrel, ticagrelor, cangrelor) is a cornerstone of medical therapy after percutaneous coronary interventions. Significant prevalence of high on-treatment platelet reactivity (HTPR) on clopidogrel treatment led to introduction of more potent P2Y₁₂ inhibitors: prasugrel (a third generation thienopyridine), ticagrelor, and cangrelor (cyclopentyl-triazolo-pyrimidines). Nevertheless, more potent platelet inhibition and resulting low on-treatment platelet reactivity (LTPR) has led to increased risk of major bleeding events. These limitations resulted in a need for an individualized antiplatelet therapy approach. This review discusses the current role and future perspectives of diagnostic tools such as platelet function testing to optimize antiplatelet therapy with a focus on deescalating therapies to reduce bleeding risks.

Trends for and Clinical Factors Associated with Choice of Oral P2Y12 Inhibitors for Patients on Chronic Dialysis

Background

Trends and clinical factors associated with prescribing choices for oral P2Y12 inhibitors (P2Y12-I) remain unknown for patients on chronic dialysis, i.e., with end-stage renal disease (ESRD).

Methods

From 2011–2014 U.S. Renal Data System registry, we identified 36,542 ESRD patients who received new prescriptions for P2Y12-I (median age 64.0 years and 54% males). Of the cohort, 93% were receiving hemodialysis and 7% on peritoneal dialysis. We analyzed trends and investigated clinical factors associated with specific P2Y12-I prescribed.

Results

Clopidogrel was prescribed for 95%, prasugrel for 3%, and ticagrelor for 2%. Clopidogrel was favored for those ≥75 years (18% of cohort). Compared to Caucasians, African Americans (36% of cohort) and Hispanics (19% of cohort) were less likely to receive prasugrel and ticagrelor (P<0.05). Patients receiving hemodialysis versus peritoneal dialysis were less likely to receive prasugrel over clopidogrel, adjusted odds ratio (aOR) 0.67 (0.55-0.82). Each additional year of dialysis decreased the odds of receiving prasugrel over clopidogrel, aOR 0.91 (0.85-0.98). History of atrial fibrillation reduced the odds of receiving ticagrelor or prasugrel over clopidogrel, aOR 0.69 (0.54-0.89) and 0.73 (0.60-0.89), respectively. Concomitant oral anticoagulant use was not associated with choice of P2Y12-I. Occurrence of non-ST segment elevation myocardial infarction or percutaneous coronary intervention within the 6-month period prior to the index date favored ticagrelor over prasugrel, aOR 1.31 (1.06-1.62) and 1.29 (1.01-1.66), respectively. However, prescribing trends favoring ticagrelor over prasugrel were not observed for deployment of drug-eluting, or multiple coronary stents.

Conclusion

Between 2011 and 2014, clopidogrel remained the most common P2Y12-I whereas ticagrelor and prasugrel remained underutilized in ESRD patients. Prescribing practices for these drugs were based upon clinically approved indication for their use in the general population as well as perceived complexity of an ESRD patient including demographics, dialysis-related factors and comorbidities. Comparative effectiveness studies involving ESRD patients are needed to prove that ticagrelor and prasugrel are just as safe and effective as clopidogrel before clinicians can make informed decisions for choice of P2Y12-I in this patient population.

Electronic supplementary material

The online version of this article (10.1007/s10557-019-06913-w) contains supplementary material, which is available to authorized users.

Platelet reactivity patterns in patients treated with dual antiplatelet therapy

AIM

The aim of the present study was to investigate the patterns of platelet reactivity and discriminators of therapeutic response to dual antiplatelet therapy (DAPT) with aspirin and ticagrelor or prasugrel in patients with acute coronary syndrome (ACS).

DESIGN

In this multicentre prospective observational study, 492 patients with ACS were enrolled. Platelet aggregation was determined by multiple electrode aggregometry after stimulation with adenosine diphosphate (ADP) or arachidonic acid (AA) as agonists in the maintenance phase of treatment with prasugrel or ticagrelor.

RESULTS

Age emerged as the strongest variable influencing aspirin response status: The mean AA-induced platelet aggregation in patients <49 years of age was 49% higher than in those >49 years (13.1 U vs 8.8 U; P = 0.011). The second strongest discriminator of aspirin response was sex: Male patients had a 40% higher AA-induced platelet aggregation values than female patients (9.5 U vs 6.8 U; P = 0.026). Platelet count emerged as the only variable influencing ADP antagonists response status showing that patients with platelet count >320 g/L displayed higher ADP-induced platelet aggregation. About 12% of patients had high on-treatment platelet reactivity (HTPR) to aspirin, 3% and 4% a HTPR to prasugrel and ticagrelor, respectively, and only 2% displayed HTPR to dual antiplatelet therapy.

CONCLUSION

When potent platelet inhibitors as prasugrel and ticagrelor are administered with aspirin, HTPR to DAPT plays only a marginal role.

Efficacy and Safety of Ticagrelor Compared with Clopidogrel in Patients with End-Stage Renal Disease with Acute Myocardial Infarction

OBJECTIVE

This study investigated the efficacy and safety of ticagrelor compared with clopidogrel in patients with end-stage renal disease (ESRD) and acute myocardial infarction (AMI).

METHODS

We retrospectively enrolled patients who had received regular dialysis and had undergone percutaneous coronary intervention (PCI) for AMI at our hospital between January 2013 and December 2016. Outcomes analyzed included cardiovascular death, death from any cause, MI, stroke, and bleeding events.

RESULT

Patients were allocated to the ticagrelor group (N = 74) or the clopidogrel group (N = 116) according to the treatment they had received. No statistically significant differences were found between the groups in terms of in-hospital primary endpoint (composite of cardiovascular death, MI, and stroke: 12.2% and 15.5% for ticagrelor and clopidogrel, respectively; p = 0.518), secondary endpoint, or any bleeding events (39.2 vs. 34.5%; p = 0.511). No statistically significant differences were found for the 1-year primary endpoint (p = 0.424), secondary endpoint, and any bleeding events (p = 0.663). Risk factors for in-hospital cardiovascular death were shock and cardiopulmonary resuscitation at initial AMI presentation, lack of beta-blocker use, and in-hospital gastrointestinal bleeding. Risk factors for 1-year cardiovascular death were shock at initial AMI presentation and lack of beta-blocker use. Only respiratory failure was a risk factor for in-hospital and 1-year gastrointestinal bleeding.

CONCLUSION

In patients with ESRD and AMI, ticagrelor resulted in numerically fewer but statistically nonsignificant rates of in-hospital and 1-year cardiovascular events with no significant increase in bleeding events compared with clopidogrel.

Between a rock and a hard place: a high-risk patient with resistance to multiple P2Y12 antagonists

Impaired response to P2Y12 receptor antagonists, such as clopidogrel and prasugrel, can have devastating consequences for patients that require prolonged or indefinite therapy with these agents, including those with a left ventricular assist device (LVAD). While loss-of-function (LOF) alleles in CYP2C19 have been elucidated as contributing to high on treatment platelet reactivity (HTPR) during clopidogrel therapy, genetic variations in the metabolic pathway of prasugrel have not been shown to elicit this same effect. Moreover, limited studies have assessed the effect of coexisting genetic variations in pharmacokinetic and pharmacodynamic pathways. Herein, we report a left ventricular assist device patient exhibiting high on treatment platelet reactivity during clopidogrel and prasugrel therapy. Genotyping revealed variants in pharmacokinetic (CYP2B6), and pharmacodynamic pathways, with multiple variants in P2Y12, the target receptor.

Haemodialysis impairs clopidogrel but not aspirin responsiveness in patients with end-stage renal disease

Dual antiplatelet therapy (DAPT) with aspirin (ASA) and clopidogrel (Clp) is the standard treatment to reduce ischaemic coronary events, but in patients with end-stage renal disease (ESRD) the efficacy of Clp remains unclear. Patients with ESRD are at higher risk for coronary artery disease (CAD) and also their post-interventional outcome is worse compared to patients with normal renal function. Little is known about the influence of haemodialysis (HD) on ASA and Clp responsiveness. To assess the effect of HD on ASA- and Clp-responsiveness in patients with documented CAD and ESRD, 31 patients with ESRD (mean age 66.5 ± 1.8 years, 23 male ) on DAPT were evaluated for their ASA and Clp responsiveness with the Verify Now System (Accumetrics Inc.) We measured the antiplatelet effect in all ESRD patients at three time points: T1: just before HD; T2: directly after HD; T3: steady state on a HD free day one week after T1. In our study at baseline 10 (32.3%) patients were ASA-low responder (ASA-LR) and 14 (45.2%) patients Clp-low responder (Clp-LR). There was a significant difference in the PRU values before ( T1) and immediately after HD (T2) [PRU T1=234 (169; 274) vs PRUT2= 247 (199; 278); pT1,2=0.036; ]. Results were shown as median ARU T1 (25th, 75th percentile) or median PRU T1 (25th, 75th percentile). Hence HD seems to impair responsiveness to Clp, resulting in an increase of 6.5 % Clp-LR. No significant differences in the ARU values at the different time-points were found.

How to improve the concept of individualised antiplatelet therapy with P2Y12 receptor inhibitors – is an algorithm the answer?

Within the past decade, high on-treatment platelet reactivity (HTPR) on clopidogrel and its clinical implications have been frequently discussed. Although it has been previously assumed that HTPR is a phenomenon occurring only in patients treated with clopidogrel, recent data show that HTPR might also occur during treatment with prasugrel or ticagrelor in the acute phase of ST-elevation myocardial infarction. Moreover, it has been postulated that there is a therapeutic window for P2Y12 receptor blockers, thus indicating that HTPR is associated with thrombotic events whereas low on-treatment platelet reactivity (LTPR) is associated with bleeding events. The current paper focuses on tools to identify risk factors for HTPR (pharmacogenomic testing, clinical scoring and drug-drug interactions) and on the use of platelet function testing in order to identify patients who might not respond adequately to clopidogrel. The majority of recent clinical randomised trials have not supported the hypothesis that platelet function testing and tailored antiplatelet therapy are providing a favourable clinical outcome. These trials, mainly performed in low-to-moderate risk patients, will be reviewed and discussed. Finally, an algorithm based on current knowledge is suggested, which might be of use for design of clinical trials.

Associations Between Chronic Kidney Disease and Outcomes With Use of Prasugrel Versus Clopidogrel in Patients With Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention: A Report From the PROMETHEUS Study

OBJECTIVES

This study sought to compare clinical outcomes in a contemporary acute coronary syndrome (ACS) percutaneous coronary intervention (PCI) cohort stratified by chronic kidney disease (CKD) status.

BACKGROUND

Patients with CKD exhibit high risks for both thrombotic and bleeding events, thus complicating decision making regarding antiplatelet therapy in the setting of ACS.

METHODS

The PROMETHEUS study was a multicenter observational study comparing outcomes with prasugrel versus clopidogrel in ACS PCI patients. Major adverse cardiac events (MACE) at 90 days and at 1 year were defined as a composite of death, myocardial infarction, stroke, or unplanned revascularization. Clinically significant bleeding was defined as bleeding requiring transfusion or hospitalization. Cox regression multivariable analysis was performed for adjusted associations between CKD status and clinical outcomes. Hazard ratios for prasugrel versus clopidogrel treatment were generated using propensity score stratification.

RESULTS

The total cohort included 19,832 patients, 28.3% with and 71.7% without CKD. CKD patients were older with greater comorbidities including diabetes and multivessel disease. Prasugrel was less often prescribed to CKD versus non-CKD patients (11.0% vs. 24.0%, respectively; p < 0.001). At 1 year, CKD was associated with higher adjusted risk of MACE (1.27; 95% confidence interval: 1.18 to 1.37) and bleeding (1.46; 95% confidence interval: 1.24 to 1.73). Although unadjusted rates of 1-year MACE were lower with prasugrel versus clopidogrel in both CKD (18.3% vs. 26.5%; p < 0.001) and non-CKD (10.9% vs. 17.9%; p < 0.001) patients, associations were attenuated after propensity stratification. Similarly, unadjusted differences in 1-year bleeding with prasugrel versus clopidogrel (6.0% vs. 7.4%; p = 0.18 in CKD patients; 2.6% vs. 3.5%; p = 0.008 in non-CKD patients) were not significant after propensity score adjustment.

CONCLUSIONS

Although risks for 1-year MACE were significantly higher in ACS PCI patients with versus without CKD, prasugrel use was 50% lower in patients with renal impairment. Irrespective of CKD status, outcomes associated with prasugrel use were not significant after propensity adjustment. These data highlight the need for randomized studies evaluating the optimal antiplatelet therapy in CKD patients with ACS.

Post Hoc Analyses of Randomized Clinical Trial for the Effect of Clopidogrel Added to Aspirin on Kidney Function

BACKGROUND AND OBJECTIVES

Despite the high burden of CKD, few specific therapies are available that can halt disease progression. In animal models, clopidogrel has emerged as a potential therapy to preserve kidney function. The effect of clopidogrel on kidney function in humans has not been established.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Secondary Prevention of Small Subcortical Strokes Study randomized participants with prior lacunar stroke to treatment with aspirin or aspirin plus clopidogrel. We compared annual eGFR decline and incidence of rapid eGFR decline (≥30% from baseline) using generalized estimating equations and interval-censored proportional hazards regression, respectively. We also stratified our analyses by baseline eGFR, systolic BP target, and time after randomization.

RESULTS

At randomization, median age was 62 (interquartile range, 55-71) years old; 36% had a history of diabetes, 90% had hypertension, and the median eGFR was 81 (interquartile range, 65-94) ml/min per 1 m2. Persons receiving aspirin plus clopidogrel had an average annual change in kidney function of -1.39 (95% confidence interval, -1.15 to -1.62) ml/min per 1.73 m2 per year compared with -1.52 (95% confidence interval, -1.30 to -1.74) ml/min per 1.73 m2 per year among persons receiving aspirin only (P=0.42). Rapid kidney function decline occurred in 21% of participants receiving clopidogrel plus aspirin compared with 22% of participants receiving aspirin plus placebo (hazard ratio, 0.94; 95% confidence interval, 0.79 to 1.10; P=0.42). Findings did not vary by baseline eGFR, time after randomization, or systolic BP target (all P values for interaction were >0.3).

CONCLUSIONS

We found no effect of clopidogrel added to aspirin compared with aspirin alone on kidney function decline among persons with prior lacunar stroke.

Antithrombotic therapy in end-stage renal disease

The delicate balance of risk vs. benefit of using antiplatelet and antithrombotic agents in the general population is well established. The decision to use these agents in the end stage renal disease (ESRD) population remains complex and difficult. The concomitant association of a prothombotic state with high risk of bleeding in the ESRD population requires individualization and careful clinical judgment before implementing such therapy. There remains a paucity of clinical trials and lack of substantial evidence in literature for safe and effective use of antithrombotic drugs in patients with advanced chronic kidney disease. The current review summarizes the pros and cons of using antiplatelet and antithrombotic agents in primary and secondary prevention of cardiovascular events, evaluate the risks with routine use of anticoagulation for cerebrovascular stroke prevention with nonvalvular atrial fibrillation and role of newer oral anticoagulants as alternate agents in the dialysis population.

Antithrombotic medications in dialysis patients: a double-edged sword

In the clinical context of end-stage renal disease (ESRD), thrombosis and bleeding risks are simultaneously increased and may have devastating consequences. While anticoagulant and antiplatelet drugs are indispensable for the prevention of thromboembolic events, the significantly higher bleeding risk makes their handling extremely complicated. In ESRD, they are frequently administered for a wide array of conditions. For example, atrial fibrillation is quite common in ESRD and warrants the use of anticoagulants like warfarin. Unfractionated heparin and low molecular weight heparins are typically used for clotting prevention in the hemodialysis extracorporeal circuit. The antithrombotics use dilemma has worsened because ESRD patients have been excluded from major clinical trials that defined standard indications, contraindications and optimal management of these medications. That limits our knowledge and results in that the process of decision-making depends on weaker data. Besides the substantial bleeding risk, warfarin may also increase cardiovascular risk because it is implicated in the pathogenesis of vascular calcifications in ESRD. The present article attempts to offer a comprehensive overview of practical considerations for the use of the most common antithrombotic medications in ESRD linking them, at the same time, to the best available evidence from randomized controlled trials and observational studies.

Antiplatelet agents in hemodialysis

Patients affected by cardiovascular disease (CVD) are treated with antiplatelet agents (AA) and/or anticoagulant drugs, which are fundamental in the management of stroke, coronary atherosclerotic disease, peripheral vascular disease and atrial fibrillation. CVD is the most important cause of death in chronic renal failure (CRF). Death rates from myocardial infarction (MI) and from all other cardiac causes exceed those for the general population. Incidence of MI in CRF is triple that in the general population. Moreover, mortality is seven- to eight-fold higher in patients requiring chronic hemodialysis compared to the general population, and approximately 40% of deaths in this population are attributable to coronary artery disease (CAD). For these reasons, AA are widely used in patients affected by CRF. Current data do not support a protective effect of antiplatelet administration in hemodialytic patients as primary prevention of cardiovascular mortality. Different results have been obtained concerning secondary prevention of CVD. The Cooperative Cardiovascular Project demonstrated that dialysis patients treated with aspirin following MI had a 43% lower mortality. Another study reported that the use of aspirin and beta-blockers following MI was associated with lower mortality in CRF patients. However, aspirin plus clopidogrel seems to increase the hemorrhagic risk without a significant reduction in cardiovascular mortality and there are insufficient data to support the use of new AA drugs in hemodialytic patients. In conclusion, since CRF patients are one of the groups at highest risk for atherosclerotic events, it could be reasonable to use aspirin in HD patients. However, the bleeding risk in HD patients needs to be strongly evaluated, especially before starting dual AA treatment.

Oral antiplatelet therapy and platelet inhibition: An experience from a tertiary care center

AIMS AND OBJECTIVES

Although clopidogrel combined with aspirin is the most commonly used dual drug combination to avert thrombotic events in patients with coronary artery disease, the poor responsiveness to clopidogrel remains a concern. The objective of the current study is to assess the extent of resistance to clopidogrel, prasugrel, and ticagrelor in a real life set of patients with coronary artery disease who underwent percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

A total of 539 patients, who underwent PCI and were on aspirin and on any of the three drugs, namely, clopidogrel, prasugrel and ticagrelor, were followed up regularly in the outpatient department. After 24h of initiation of antiplatelet medication, response to the treatment in all the patients was assessed using thrombelastography. The average percentage platelet inhibition was assessed along with the resistance and sensitivity to the drug in each patient. Sensitivity and resistance to the specific drug was defined as >50% and <50% of mean platelet inhibition, respectively.

RESULTS

About 99.15% of the patients treated with ticagrelor were sensitive to the drug and the difference between ticagrelor, clopidogrel, and prasugrel groups for sensitivity was significant with a p value of 0.00001, in favor of ticagrelor. It was also found that ticagrelor was significantly (p value of 0.001) associated with least resistance as compared with the other drugs assessed in the study.

CONCLUSIONS

Use of ticagrelor as dual therapy along with aspirin in patients with coronary artery disease (CAD) and undergoing PCI was associated with a significantly higher mean percentage platelet inhibition, higher sensitivity, and lower resistance as compared with the usage of clopidogrel or prasugrel.

Clopidogrel treatment may associate with worsening of endothelial function and development of new digital ulcers in patients with systemic sclerosis: results from an open label, proof of concept study

Background

Activated platelets release serotonin that binds 5-HT_2B receptor on fibroblasts leading to fibroblast activation. Clopidogrel, an inhibitor of ADP-dependent platelet activation prevents fibrosis in animal models of systemic sclerosis (SSc). We aimed at assessing whether i) ADP-dependent platelet activation is increased in patients with SSc compared to healthy subjects and patients with rheumatoid arthritis (RA) and ii) whether clopidogrel can effectively suppress ADP-dependent activation, reduce circulating serotonin levels and hence, favorably affect fibrosis or vasculopathy in patients with systemic sclerosis.

Methods

Thirteen patients with SSc were recruited. Platelet activation was assessed by aggregometry prior to and following 14 days of clopidogrel treatment. At the same time points serotonin and soluble vascular cell adhesion molecule 1 (s-VCAM1), a marker of endothelial dysfunction, were measured.

Results

ADP-dependent platelet activation was similar between patients with SSc (n = 13), patients with RA (n = 28) and healthy subjects (n = 22) (mean ± SEM AU*min: 392.1 ± 58.4, 535.5 ± 61.33 and 570.9 ± 42.9 in patients with SSc, patients with RA and healthy subjects respectively, p = 0.14). Clopidogrel treatment significantly reduced platelet activation in patients with SSc (mean ± SEM AU*min: 392.1 ± 58.4 vs 163.8 ± 51.7, p = 0.014). Clopidogrel treatment did not affect serotonin levels but led to a significant increase in s-VCAM1 (p = 0.03). Three patients developed new digital ulcers during the study. The potential association of the study drug with the development of new digital ulcers led to early termination of the study.

Conclusion

Clopidogrel may worsen markers of endothelial function and associate with development of new digital ulcers in patients with SSc.

Clinical trial registration

ISRCTN63206606. Registered 02/Dec/2014.

Repetitive stent thrombosis in a patient who had resistance to both clopidogrel and prasugrel

Clopidogrel resistance is associated with stent thrombosis. Prasugrel achieves greater platelet inhibition with less variability among patients than does clopidogrel. Thus, a patient who had stent thrombosis due to clopidogrel resistance may receive prasugrel to prevent repeated episodes of stent thrombosis. This case report describes a case of repetitive stent thrombosis in which resistance not only to clopidogrel, but also to prasugrel, was observed. <Learning objective: In the face of clopidogrel resistance, prescribing prasugrel may be an acceptable treatment option. However, cross-unresponsiveness may be observed between clopidogrel and prasugrel. Thus, platelet function assay should be performed in patients with stent thrombosis, even when clopidogrel is replaced with prasugrel.>.

Inter-patient variability of platelet reactivity in patients treated with prasugrel and ticagrelor

The aim of this study was to evaluate the distribution of platelet reactivity values in patients treated with prasugrel and ticagrelor. This prospective observational study enrolled 200 patients treated with prasugrel or ticagrelor. Platelet aggregation was determined by multiple electrode aggregometry after stimulation with adenosine diphosphate (ADP) in the maintenance phase of treatment with prasugrel or ticagrelor. Only 3% of patients in the prasugrel group and 2% of study participants in the ticagrelor group had high on treatment platelet reactivity (HTPR). The majority of patients displayed low on treatment platelet reactivity (LTPR; prasugrel: 69%; ticagrelor: 64%). The pharmacodynamic effect was similar in patients treated with prasugrel and ticagrelor: the median level of ADP-induced platelet aggregation was 15U (interquartile range IQR 9-21U) under prasugrel treatment and 17U (IQR 8-24U) under ticagrelor treatment (p=0.370). In conclusion, our study suggests that there is some degree of variability in ADP-induced platelet aggregation under treatment with prasugrel and ticagrelor.

Impact of residual platelet reactivity under clopidogrel treatment for lesions and the clinical outcome after drug-eluting stent implantation in patients with hemodialysis

BACKGROUND

Hemodialysis (HD) patients are at high risk for adverse clinical outcomes after drug-eluting stent (DES) implantation. However, the impact of residual platelet reactivity under dual anti-platelet therapy in this subset of patients remains unclear.

METHODS

We enrolled 142 stable angina patients (194 lesions) treated with DES, who were taking aspirin and 75mg clopidogrel and had undergone 8-month angiography with optical coherence tomography (OCT). OCT findings and major adverse cardiac events (MACEs) at 1 year (cardiac death, acute coronary syndrome, target lesion and vessel revascularization, and stent thrombosis) were compared between 28 HD patients and 114 non-HD patients. Responsiveness to clopidogrel was assessed by measuring P2Y12 reaction unit (PRU) at 8 months.

RESULTS

PRU was significantly higher in HD patients than in non-HD patients (p=0.006), even though proportion of cytochrome P450 2C19 genotype was equivalent. HD patients had a significantly higher rate of thrombi formation (assessed using OCT) and MACEs than non-HD patients (thrombi: p=0.001; MACEs: p=0.0001). The PRU value was independently associated with MACEs in both groups. The optimal cutoff values of PRU for predicting MACEs were 235 for HD patients and 259 for non-HD patients.

CONCLUSIONS

HD was associated with a high residual platelet reactivity, which may contribute to the higher incidence of MACEs after DES implantation in HD patients. HD may be a patient profile that merits a more potent anti-platelet regimen.

Antiplatelet Therapy in Hemodialysis Patients Undergoing Percutaneous Coronary Interventions

Context:

Coronary artery disease is highly prevalent among patients with end stage renal disease/hemodialysis (ESRD/HD) and coronary percutaneous interventions (PCI) has been increased by nearly 50% over the past decade. After PCI with stent placement, guidelines recommend dual antiplatelet therapy (DAPT), but no specifically tailored pharmacotherapy approach is outlined for this frail population, mostly excluded from large randomized clinical trials (RCTs).

Evidence Acquisition:

We reviewed current evidences on the use of antiplatelet therapy in patients with ESRD/HD undergoing PCI, focusing on the efficacy and safety of specific agents and their indications for detailed clinical settings.

Results:

Clinical setting in HD patients is the principal determinant of the type, onset, combination and duration of the DAPT. However, irrespective clinical setting, in addition to aspirin, clopidogrel is currently the most used antiplatelet agent even if no information derived from RCTs are available in ESRD. Due to the large experience acquired in routine clinical practice, the awareness of safety is higher for clopidogrel than newer antiplatelet agents. Because of lack of data, the use of prasugrel and ticagrelor is actually not recommended. However, in case of high ischemic and acceptable bleeding risk, they may be selectively used in ESRD/HD.

Conclusions:

This investigation might contribute to delineate the best treatment options for this high risk population.

Medical adjuvant treatment to increase patency of arteriovenous fistulae and grafts

BACKGROUND

End-stage renal disease (ESRD) patients often require either the formation of an arteriovenous (AV) fistula or an AV interposition prosthetic shunt for haemodialysis. These access sites should ideally have a long life and a low rate of complications (for example thrombosis, infection, stenosis, aneurysm formation and distal limb ischaemia). Although some of the complications may be unavoidable, any adjuvant technique or medical treatment aimed at decreasing complications would be welcome. This is the second update of the review first published in 2004.

OBJECTIVES

To assess the effects of adjuvant drug treatment in ESRD patients on haemodialysis via autologous AV fistulae or prosthetic interposition AV shunts.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched March 2015) and CENTRAL (2015, Issue 2).

SELECTION CRITERIA

Randomised controlled trials (RCTs) of active drug versus placebo in people with ESRD undergoing haemodialysis via an AV fistula or prosthetic interposition AV graft.

DATA COLLECTION AND ANALYSIS

For this update, the two review authors (NCT, ADS) independently assessed trial quality and one review author (NCT) extracted data. Information on adverse events was collected from the trials. The primary outcome was the long-term fistula or graft patency rate. Secondary outcomes included duration of hospital stay, complications and number of related surgical interventions.

MAIN RESULTS

For this update, an additional six studies were deemed suitable for inclusion, making a total of 15 trials with 2230 participants. Overall the quality of the evidence was low due to short follow-up periods, heterogeneity between trials and moderate methodological quality of the studies due to incomplete reporting. Medical adjuvant treatments used in the trials were aspirin, ticlopidine, dipyridamole, dipyridamole plus aspirin, warfarin, fish oil, clopidogrel, sulphinpyrazone, and human type I pancreatic elastase (PRT-201). Where possible, the included studies were pooled into similar medical adjuvant groups for meta-analyses.All included studies reported on graft patency by measuring graft thrombosis. There was insufficient evidence to determine if there was a difference in graft patency in studies comparing aspirin versus placebo (three RCTs, 175 participants) (odds ratio (OR) 0.40, 95% confidence interval (CI) 0.07 to 2.25; P = 0.30). The meta-analysis for graft patency comparing ticlopidine versus placebo (three RCTs, 339 participants) favoured ticlopidine (OR 0.45, 95% CI 0.25 to 0.82; P = 0.009). There was insufficient evidence to determine if there was a difference in graft patency in studies comparing fish oil versus placebo (two RCTs, 220 participants; OR 0.24, 95% CI 0.03 to 1.95; P = 0.18); and studies comparing clopidogrel and placebo (two RCTs, 959 participants; OR 0.40, 95% CI 0.13 to 1.19; P = 0.10). Similarly, there was insufficient evidence to determine if there was a difference in graft patency in three studies (306 participants) comparing PRT-201 versus placebo (OR 0.75, 95% CI 0.42 to 1.32; P = 0.31); in one trial comparing the effect of dipyridamole versus placebo (42 participants; OR 0.46, 95% CI 0.11 to 1.94, P = 0.29) and dipyridamole plus aspirin versus placebo (41 participants; OR 0.64, CI 0.16 to 2.56, P = 0.52); in one trial comparing low-dose warfarin with placebo (107 participants; OR 1.76, 95% CI 0.78 to 3.99, P = 0.17); and one trial (16 participants) comparing sulphinpyrazone versus placebo (OR 0.43, 95% CI 0.03 to 5.98, P = 0.53). The single trial evaluating warfarin was terminated early because of major bleeding events in the warfarin group. Only two studies published data on the secondary outcome of related interventions (surgical or radiological); there was insufficient evidence to determine if there was a difference in related interventions between placebo and treatment groups. No studies reported on the length of hospital stay and data reporting on complications was limited and varied between studies.

AUTHORS' CONCLUSIONS

The meta-analyses of three studies for ticlopidine (an anti-platelet treatment), which all used the same dose of treatment but with a short follow-up of only one month, suggest ticlopidine may have a beneficial effect as an adjuvant treatment to increase the patency of AV fistulae and grafts in the short term. There was insufficient evidence to determine if there was a difference in graft patency between placebo and other treatments such as aspirin, fish oil, clopidogrel, PRT-201, dipyridamole, dipyridamole plus aspirin, warfarin, and sulphinpyrazone. However, the quality of the evidence was low due to short follow-up periods, the small number of studies for each comparison, heterogeneity between trials and moderate methodological quality of the studies due to incomplete reporting. It, therefore, appears reasonable to suggest further prospective studies be undertaken to assess the use of these anti-platelet drugs in renal patients with an arteriovenous fistula or graft.

High On-Treatment Platelet Reactivity Associated With Prasugrel

Objective: To report a case of high on-treatment platelet reactivity (HTPR) with prasugrel maintenance therapy despite adequate initial platelet response to a loading dose. Case Summary: A 51-year-old woman presented to the emergency department complaining of chest pain. She was diagnosed with acute-on-chronic systolic heart failure and non-ST-elevated myocardial infarction (MI). She had a previous MI with bare metal stent placement and was taking aspirin and prasugrel 10 mg daily. Once admitted, a P2Y12 assay revealed HTPR (331 PRU); therefore, prasugrel was reloaded (60 mg). The next day a P2Y12 assay showed adequate platelet reactivity inhibition (118 PRU), so prasugrel 10 mg daily was continued in the hospital and on discharge. Seventeen days after discharge she was readmitted for possible ischemia. On day 3 of admission, a P2Y12 assay revealed HTPR (278 PRU); subsequently, prasugrel was discontinued and ticagrelor started. After 3 doses of ticagrelor, a P2Y12 assay was 97 PRU, so ticagrelor was continued. Five months have passed since discharge. The patient continues to take ticagrelor and has had no further cardiac events. Discussion: HTPR indicates hypo- or nonresponsiveness for antiplatelet agents and may result in serious adverse events. HTPR has rarely been reported with prasugrel or ticagrelor. An objective causality assessment of our case revealed a probable association between HTPR and prasugrel. Conclusion: Patient education and recognition of signs and symptoms associated with prasugrel HTPR may prevent morbidity and mortality from treatment failure. Additional research may determine incidence, risk factors, and optimal management of HTPR with prasugrel.

Platelet reactivity after receiving clopidogrel compared with ticagrelor in patients with kidney failure treated with hemodialysis: a randomized crossover study

BACKGROUND

Patients with kidney failure treated with maintenance hemodialysis (HD) are poor responders to clopidogrel. More beneficial platelet-inhibiting strategies in HD patients therefore are required.

STUDY DESIGN

Single-center, prospective, randomized, crossover study.

SETTING & PARTICIPANTS

25 HD patients in Seoul, Korea.

INTERVENTION

Patients were randomly assigned to receive clopidogrel (300mg loading, 75mg once daily for maintenance dose) or ticagrelor (180mg loading, 90mg twice daily for maintenance dose) for 14 days, and after a 14-day washout period, crossover treatment for another 14 days. All patients received aspirin (100mg/d).

OUTCOMES & MEASUREMENTS

Platelet function was evaluated predosing and at 1, 5, and 48 hours and 14 days after the first loading dose. During the offset phase, platelet function was assessed at 1 hour and 2, 4, and 14 days after the last dose by light transmittance aggregometry and the VerifyNow P2Y12 assay, and patients were genotyped for the CYP2C19*2 allele. Maximal extent of aggregation, inhibition of platelet aggregation (IPA), P2Y12 reaction units (PRUs), and percentage of inhibition were evaluated. We performed per-protocol analysis, excluding patients who did not complete the protocol.

RESULTS

9 patients did not complete the protocol (7 patients due to adverse events; 2, nonadherence). Higher IPA occurred with ticagrelor than with clopidogrel at 1, 5, and 48 hours and 14 days after loading. By 5 hours after loading, a greater proportion of patients in the ticagrelor group than in the clopidogrel group achieved IPA>50% (75% vs 12%, respectively; P<0.05) and IPA>70% (44% vs 0%, respectively; P<0.05). Rates (slope) of onset and offset of the antiplatelet effect were faster in patients receiving ticagrelor than for those receiving clopidogrel (P<0.05). Regardless of CYP2C19*2 allele, the ticagrelor group had significantly lower PRUs at all times than the clopidogrel group.

LIMITATIONS

Single-center study with a small number of patients, not a double-blind study, and not intention-to-treat analysis.

CONCLUSIONS

Ticagrelor may result in more rapid and greater platelet inhibition than clopidogrel in patients with kidney failure receiving HD.

Personalized antiplatelet therapy with P2Y12 receptor inhibitors: benefits and pitfalls

Antiplatelet therapy with P2Y₁₂ receptor inhibitors has become the cornerstone of medical treatment in patients with acute coronary syndrome, after percutaneous coronary intervention and in secondary prevention of atherothrombotic events. Clopidogrel used to be the most broadly prescribed P2Y₁₂ receptor inhibitor with undisputable benefits especially in combination with aspirin, but a considerable number of clopidogrel-treated patients experience adverse thrombotic events in whom insufficient P2Y₁₂-inhibition and a consequential high on-treatment platelet reactivity is a common finding. This clinically relevant limitation of clopidogrel has driven the increased use of new antiplatelet agents. Prasugrel (a third generation thienopyridine) and ticagrelor (a cyclopentyl-triazolo-pyrimidine) feature more potent and predictable P2Y₁₂-inhibition compared to clopidogrel, which translates into improved ischemic outcomes. However, excessive platelet inhibition and consequential low on-treatment platelet reactivity comes at the price of increased risk of major bleeding. The majority of randomized clinical trials failed to demonstrate improved clinical outcomes with platelet function testing and tailored antiplatelet therapy, but results of all recent trials of potent antiplatelets and prolonged antiplatelet durations point towards a need for individualized antiplatelet approach in order to decrease thrombotic events without increasing bleeding. This review focuses on potential strategies for personalizing antiplatelet treatment.

Prasugrel and ticagrelor: is there a winner?

Clopidogrel is a prodrug that undergoes extensive enteric clearance and requires two-stage hepatic activation by cytochrome P450 (CYP) enzymes. This metabolic pathway is susceptible to genetic polymorphisms, resulting in a variable platelet inhibitory effect. A growing number of studies have linked poor antiplatelet response to clopidogrel to adverse clinical outcomes, particularly coronary ischemic events and stent thrombosis. This has prompted the development of new ADP receptor antagonists that inhibit platelets more effectively. Two of these agents, prasugrel and ticagrelor, have been investigated in two large randomized clinical trials, and both have shown superiority versus clopidogrel in reducing ischemic endpoints, with an increase in bleeding events, but a favorable final net clinical outcome. Since the publication of the main articles, several sub-analyses have been performed on the same data, and Guideline recommendations have largely endorsed these subgroup findings. Most clinicians have accepted the concept that we might consider approaching the patient differently, deserving a specific agent for each different settings. However, subgroup analyses of randomized trials are often post hoc, underpowered and prone to bias. Weighing efficacy and safety of the most commonly used antiplatelet agents will represent a clinical challenge over the next few years. Furthermore, individuals and organizations involved in formulary decisions will have to face economic constraints, also taking into account the availability of low-cost generic clopidogrel. In the following review, we have performed a critical appraisal of the current literature in order to outline lights and shadows on the most relevant clinical scenarios.

Efficacy of clopidogrel treatment and platelet responsiveness in peripheral arterial procedures

INTRODUCTION

Long-term antiplatelet therapy with clopidogrel has been recommended in patients undergoing peripheral arterial procedures. Poor antiplatelet effect of clopidogrel or high on-clopidogrel platelet reactivity (HCPR) has been recently identified in patients with peripheral arterial disease (PAD).

AREAS COVERED

This review focuses on the use of clopidogrel and the phenomenon of HCPR in PAD patients treated for intermittent claudication or critical limb ischaemia (CLI). The authors summarize current guidelines and recommendations for use of clopidogrel following peripheral arterial procedures and explore the prevalence and clinical impact of HCPR in the PAD population. Underlying mechanisms of HCPR and relevant clinical and genetic factors are analyzed with particular attention to the potential utility of point-of-care platelet function testing (PFT).

EXPERT OPINION

Clopidogrel is a safe, effective and well-tolerated antiplatelet agent in PAD patients following peripheral arterial revascularization. Dual-antiplatelet therapy could also be considered after complex endovascular procedures. HCPR has been identified in more than 50% of PAD patients on clopidogrel and has been related with significantly increased re-intervention rates. Incidence of HCPR is significantly higher in patients with CLI, diabetes mellitus and chronic renal disease. Personalized antiplatelet therapy on the basis of PFT is an elegant emerging concept for optimization of platelet inhibition and potential identification of patients at increased risk of bleeding and warrants investigation in future large-scale trials.

The net clinical benefit of personalized antiplatelet therapy in patients undergoing percutaneous coronary intervention

In this study we have demonstrated that individualized treatment with ADP-receptor blockers might result in an improved efficacy with an equal safety.

High on-treatment platelet reactivity in peripheral endovascular procedures

The use of aspirin is considered the "gold standard" for the decrease of major adverse cardiovascular events in patients with atherosclerosis, including peripheral arterial disease (PAD), whereas a dual-antiplatelet regimen with aspirin and clopidogrel is usually indicated for such patients after angioplasty and stent deployment. However, a substantial number of subsequent adverse events still occur, even in patients who receive double-antiplatelet therapy. The "high on-treatment platelet reactivity" (HTPR) phenomenon has been lately recognized and plays a major role in the management of patients with PAD. Greater and more rapid inhibition of platelet aggregation has become the goal for new antiplatelet agents with the expectation of further improving outcomes for percutaneous intervention for PAD. The purpose of this review article is to highlight current evidence regarding the prevalence, aetiology, and clinical implications of HTPR in PAD as well as to discuss the possibilities of novel alternative antiplatelet regiments.

Platelet-reactivity tests identify patients at risk of secondary cardiovascular events: a systematic review and meta-analysis

BACKGROUND

Antiplatelet therapy is the standard treatment for the prevention of cardiovascular events (CVEs). High on-treatment platelet reactivity (HPR) is a risk factor for secondary CVEs in patients prescribed aspirin and/or clopidogrel. The present review and meta-analysis was aimed at assessing the ability of individual platelet-function tests to reliably identify patients at risk of developing secondary CVEs.

METHODS AND RESULTS

A systematic literature search was conducted to identify studies on platelet-reactivity measurements and CVEs. The main inclusion criteria were: (i) prospective study design; (ii) study medication, including aspirin and/or clopidogrel; and (iii) a platelet-function test being performed at baseline, before follow-up started. Of 3882 identified studies, 102 (2.6%; reporting on 44 098 patients) were included in the meta-analysis. With regard to high on-aspirin platelet reactivity (HAPR), 22 different tests were discussed in 55 studies (22 441 patients). Pooled analysis showed that HAPR was diagnosed in 22.2% of patients, and was associated with an increased CVE risk (relative risk [RR] 2.09; 95% confidence interval [CI] 1.77-2.47). Eleven HAPR tests independently showed a significantly increased CVE risk in patients with HAPR as compared with those with normal on-aspirin platelet reactivity. As regards high on-clopidogrel platelet reactivity (HCPR), 59 studies (34 776 patients) discussed 15 different tests, and reported that HCPR was present in 40.4% of patients and was associated with an increased CVE risk (RR 2.80; 95% CI 2.40-3.27). Ten tests showed a significantly increased CVE risk.

CONCLUSIONS

Patients with HPR are suboptimally protected against future cardiovascular complications. Furthermore, not all of the numerous platelet tests proved to be able to identify patients at increased cardiovascular risk.

p2y12 receptor inhibitors in acute coronary syndromes: from the research laboratory to the clinic and vice versa

The P2Y12 receptor plays a pivotal role in platelet activation and aggregation through a complex cascade of actions. Laboratory and clinical data have convincingly shown the benefit of P2Y12 inhibition combined with aspirin in patients with acute coronary syndrome (ACS)/undergoing percutaneous coronary intervention (PCI). Newer agents - like prasugrel, ticagrelor, and cangrelor - provide more consistent, faster, and stronger platelet inhibition than clopidogrel. In large clinical trials newer agents have resulted in fewer ischemic complications (though with increased bleeding potential) than clopidogrel. High-risk subpopulations like ST-segment elevation myocardial infarction, diabetes, chronic kidney disease, elderly, and low body weight patients have been identified. A 'return to the laboratory' has been observed recently, with several pharmacodynamic studies being performed particularly in these cohorts. This interplay between research laboratory and clinical data may lead to a more efficient and safer use of P2Y12 inhibitors.