High on-aspirin treatment platelet reactivity and restenosis after percutaneous coronary intervention: results of the Intracoronary Stenting and Antithrombotic Regimen-ASpirin and Platelet Inhibition (ISAR-ASPI) Registry

OBJECTIVE

The aim of this study was to assess the association between high on-aspirin treatment platelet reactivity (HAPR) and the subsequent risk of restenosis after percutaneous coronary intervention (PCI) with predominantly drug-eluting stents.

BACKGROUND

The association between HAPR and subsequent risk of restenosis after PCI is unclear.

METHODS

This study included 4839 patients undergoing PCI (02/2007-12/2011) in the setting of the Intracoronary Stenting and Antithrombotic Regimen-ASpirin and Platelet Inhibition (ISAR-ASPI) registry. Platelet function was assessed with impedance aggregometry using the multi-plate analyzer immediately before PCI and after intravenous administration of aspirin (500 mg). The primary outcome was clinical restenosis, defined as target lesion revascularization at 1 year. Secondary outcomes included binary angiographic restenosis and late lumen loss at 6- to 8-month angiography.

RESULTS

The upper quintile cut-off of platelet reactivity measurements (191 AU × min) was used to categorize patients into a group with HAPR (platelet reactivity > 191 AU × min; n = 952) and a group without HAPR (platelet reactivity ≤ 191 AU × min; n = 3887). The primary outcome occurred in 94 patients in the HAPR group and 405 patients without HAPR (cumulative incidence, 9.9% and 10.4%; HR = 0.96, 95% CI 0.77-1.19; P = 0.70). Follow-up angiography was performed in 73.2% of patients. There was no difference in binary restenosis (15.2% vs. 14.9%; P = 0.79) or late lumen loss (0.32 ± 0.57 vs. 0.32 ± 0.59 mm; P = 0.93) between patients with HAPR versus those without HAPR.

CONCLUSIONS

This study did not find an association between HAPR, measured at the time of PCI, and clinical restenosis at 1 year after PCI.

Comparison of Vascular Closure Devices vs Manual Compression After Femoral Artery Puncture in Patients on Oral Anticoagulation - Post Hoc Analysis of the ISAR-CLOSURE Trial

OBJECTIVES

To compare vascular closure devices (VCD) with manual compression (MC) in patients on chronic oral anticoagulation (OAC) who undergo diagnostic coronary angiography in terms of vascular access-site complications.

METHODS

This is a subanalysis of 604 patients that had undergone transfemoral diagnostic coronary angiography and were randomly assigned to arteriotomy closure with either VCDs (intravascular FemoSeal VCD or extravascular EXOSEAL VCD) or MC within the large scale, randomized ISAR-CLOSURE trial. Primary endpoint was the composite of access-site-related vascular complications at 30 days. Secondary endpoints were time to hemostasis and repeat MC.

RESULTS

Vascular access-site complications were similar in patients assigned to VCDs compared to MC (8.2% vs 10.6%; P=.33). There was no interaction of treatment effect and OAC (P interaction = 0.59). Rates of pseudoaneurysms were lower with VCDs (0.8% vs 3.2%; P=.02). Time to hemostasis was significantly shortened with VCDs compared to MC (1 [IQR 0.5-2.0] min vs 12 [IQR 10-15] min; P<.001). There was no difference regarding repeat MC in both groups (VCD 1.5% vs MC 0.5%; P=.23). Time to hemostasis (0.5 [0.2-1.0] min, vs 2.0 [1.75-2.0] min; P<.001) and closure device failure (3.7% vs 17.2%; P<.001) were lower with the intravascular VCD, compared with the extravascular VCD.

CONCLUSIONS

In patients on chronic OAC undergoing transfemoral diagnostic coronary angiography, the use of VCDs was comparable to MC regarding the primary combined endpoint of vascular access-site related complications. VCDs reduced the occurrence of pseudoaneurysms and time to hemostasis.

Efficacy and Safety of Ticagrelor Versus Prasugrel in Women and Men with Acute Coronary Syndrome: A Pre-specified, Sex-Specific Analysis of the ISAR-REACT 5 Trial

Aim: Sex-specific analyses of direct head-to-head comparisons between newer P2Y₁₂ inhibitors are limited. This study was conducted to assess the efficacy and safety of ticagrelor versus prasugrel in women and men with acute coronary syndromes (ACS) planned for an invasive strategy.

Methods: This pre-specified analysis of the ISAR-REACT 5 trial included 956 women and 3,062 men with ACS randomly assigned to either ticagrelor or prasugrel. The primary endpoint was the 12-month incidence of death, myocardial infarction, or stroke; the safety endpoint was the 12-month incidence of bleeding (type 3–5 according to the Bleeding Academic Research Consortium [BARC]).

Results: The primary endpoint occurred in 42 women (8.9%) in the ticagrelor group and 39 women (8.3%) in the prasugrel group (hazard ratio [HR]=1.10, 95% confidence interval [CI] 0.71–1.70,P=0.657) and in 142 men (9.4%) in the ticagrelor group and 98 men (6.5%) in the prasugrel group (HR=1.47 [1.13–1.90],P=0.004;P for interaction [P_int]=0.275). BARC type 3–5 bleeding occurred in 36 women (9.7%) in the ticagrelor group and 34 women (9.7%) in the prasugrel group (HR=1.04 [0.65–1.67],P=0.856) and in 59 men in the ticagrelor group (4.4%) and 46 men (3.6%) in the prasugrel group (HR=1.24 [0.85–1.83],P=0.266; P_int=0.571).

Conclusions: Although there was no significant interaction between sex and treatment effect of study drugs, the superior efficacy of prasugrel was more evident among men. No difference in bleeding between the two study groups was seen for both women and men.

Comparison of Vascular Closure Devices Versus Manual Compression After Femoral Artery Puncture in Women

BACKGROUND

The value of vascular closure devices (VCD) in women undergoing transfemoral catheterization has not been sufficiently investigated.

METHODS AND RESULTS

This is a sex-specific analysis of 1395 women enrolled in a large-scale, randomized, multicenter trial, in which patients undergoing transfemoral diagnostic coronary angiography were randomly assigned in a 1:1:1 ratio to arteriotomy closure with an intravascular VCD, extravascular VCD, or manual compression (MC). Primary objective was to assess the safety and efficacy of 2 different VCD compared with MC regarding vascular access-site complications at 30 days. A secondary comparison was between 2 different types of contemporary VCD. Overall, women were at higher risk for vascular access-site complications compared with men (9.0% versus 6.4%; P=0.002). Vascular access-site complications were comparable in women assigned to VCD and MC (8.6% versus 9.8%; P=0.451). There was no interaction of treatment effect and sex ( P_interaction=0.970). Time to hemostasis was significantly shortened with VCD compared with MC (1 [interquartile range, 0.5-2.0] minutes) versus 11 [interquartile range, 10-15] minutes; P<0.001); however, more women with VCD required repeat MC (2.4% versus 0.6%; P=0.018). The use of the intravascular compared with the extravascular VCD was associated with a numerical reduction in vascular access-site complications (6.6% versus 10.7%; P=0.027) and significant reductions in time to hemostasis and VCD failure.

CONCLUSIONS

In women undergoing diagnostic coronary angiography via the common femoral artery, VCD and MC provided comparable safety, while time to hemostasis was reduced with VCD.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01389375.

Antiplatelet efficacy of prasugrel in patients with high on-clopidogrel treatment platelet reactivity and a history of coronary stenting

Little is known about the antiplatelet action of the 3rd generation thienopyridine prasugrel in patients showing high platelet reactivity (PR) levels on clopidogrel. Thus, we aimed to determine the antiplatelet efficacy of prasugrel loading (LD) and maintenance dose (MD) treatment in a registry of patients with high PR levels on clopidogrel and a consecutive switch over to prasugrel in a setting of routine platelet function testing. In our registry of patients treated by percutaneous coronary intervention (n=73) with high levels of PR on clopidogrel, the ADP-induced platelet aggregation (PA, in AU x min) was assessed on a Multiplate analyser 1) after clopidogrel LD, 2) after prasugrel LD and 3) on prasugrel MD (5 vs. 10 mg/day). In patients with high PR levels on clopidogrel, prasugrel LD resulted in significantly lower PA values (574 [462–698] vs. 156 [89–234] AU x min; p<0.0001). Only 2.7% of patients showed high PR (HPR, 468 AU x min) following prasugrel LD. On prasugrel MD, PA was significantly higher as compared to prasugrel LD (248 [145–406] vs. 156 [89–234] AU x min; p<0.0001) with more patients showing HPR on MD vs. LD (16.4% vs. 2.7%; p=0.009). For prasugrel MD, HPR rates were higher in 5 vs. 10 mg/day treated patients (46.2% vs. 10.0%; p=0.006). In conclusion, for patients with high PR levels on clopidogrel, prasugrel LD abolished this status in the majority of patients. However, prasugrel response variability was detected, being more pronounced on prasugrel MD vs. LD treatment. The clinical impact of these findings warrants further investigation.

Impact of proton pump inhibitors on the antiplatelet effects of clopidogrel

Patients receiving dual antiplatelet treatment with aspirin and clopidogrel are commonly treated with proton pump inhibitors (PPIs). Attenuating effects on platelet response to clopidogrel have been reported solely for the PPI omeprazole. PPIs differ in their metabolisation properties as well as their potential for drug-drug interactions. The aim of this study was to investigate the impact of different PPIs (pantoprazole, omeprazole, esomeprazole) on platelet response to clopidogrel in patients with previous coronary stent placement under chronic clopidogrel treatment. In a cross-sectional observational study, consecutive patients under clopidogrel maintenance treatment (n=1,000) scheduled for a control coronary angiography were enrolled. Adenosine diphosphate (ADP)-induced platelet aggregation (in AU*min) was measured with multiple electrode platelet aggregometry (MEA). From the entire study population, 268 (26.8%) patients were under PPI treatment at the time point of platelet function testing (pantoprazole, n=162; omeprazole, n=64; esomeprazole, n=42). Platelet aggregation (median [interquar-tile range]) was significantly higher in patients with omeprazole treatment (295.5 [193.5–571.2] AU*min) compared to patients without PPI treatment (220.0 [143.8–388.8] AU*min; p=0.001). Platelet aggregation was similar in patients with pantoprazole (226.0 [150.0–401.5] AU*min) or esomeprazole (209.0 [134.8–384.8] AU*min) treatment compared to patients without PPI treatment (p=0.69 and p=0.88, respectively). Attenuating effects of concomitant PPI treatment on platelet response to clopidogrel were restricted to the use of omeprazole. No attenuating effects on platelet response to clopidogrel were observed for pantoprazole or esomeprazole. Specifically designed and randomized clinical studies are needed to define the impact of concomitant PPI treatment on adverse events after percutaneous coronary intervention.

Prasugrel vs clopidogrel in cardiogenic shock patients undergoing primary PCI for acute myocardial infarction

There is limited clinical data comparing different P2Y12-receptor inhibitors in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock. The aim of the ISAR-SHOCK registry was to compare the clinical outcome of patients treated with clopidogrel vs prasugrel in this setting. Patients (n=145) with AMI complicated by cardiogenic shock and undergoing primary PCI in two centres (Deutsches Herzzentrum München and Klinikum rechts der Isar, Technical University Munich) between January 2009 and May 2012 were included in this registry. The use of prasugrel for patients within this registry reflected co-morbidities and platelet function testing results during the acute AMI phase. Early outcome at 30-days was reported with regard to all-cause mortality, myocardial infarction (MI), stent thrombosis (ST) and bleeding events. With regard to antiplatelet treatment in the 145 cardiogenic shock patients, 50 patients were initially treated or immediately switched to prasugrel while 95 patients were treated with clopidogrel. All-cause mortality was lower in prasugrelvs clopidogrel-treated patients (30 % vs 50.5%, HR: 0.51, 95% CI [0.29–0.92], p=0.025). No significant differences in prasugrel- vs clopidogrel-treated patients were observed for the occurrence of MI (p=0.233), ST (p=0.306) or TIMI major bleedings (p=0.571). Results of the ISAR-SHOCK registry suggest that the use of prasugrel in AMI patients complicated by cardiogenic shock might be associated with a lower mortality risk as compared to clopidogrel therapy without increasing the risk of bleeding. These findings, however, need confirmation from specifically designed randomised studies in this high-risk cohort of patients.

Validation of the DAPT score in patients randomized to 6 or 12 months clopidogrel after predominantly second-generation drug-eluting stents

The DAPT score is a recently-proposed decision tool for guiding optimal duration of dual antiplatelet therapy (DAPT). It showed modest accuracy in prior derivation and validation cohorts of patients with ≥12 months DAPT. This study was aimed to evaluate the validity of the DAPT score in a cohort of patients with 6 or 12 months DAPT after implantation of predominantly second-generation drug-eluting stents. We analyzed data of patients enrolled in the ISAR-SAFE trial. Patients were classified into low (<2) or high (≥2) DAPT score groups. Primary ischaemic (all-cause death, myocardial infarction, definite stent thrombosis or stroke) and bleeding (TIMI major or minor) outcomes were analyzed in the low and high DAPT score groups. Data of 3976 patients were available for DAPT score calculation. 2407 patients (60.5%) were classified in the low DAPT score group and 1569 patients (39.5%) in the high DAPT score group. In the low DAPT score group there were no significant differences between 6 and 12 months DAPT regarding ischaemic (1.0% vs. 1.4%, HR=0.74, 95% CI, 0.35–1.57; p=0.43) or bleeding outcomes (0.3% vs. 0.8%, HR=0.44, 95% CI, 0.13–1.42; p=0.17). In the high DAPT score group there were also no significant differences between 6 and 12 months DAPT regarding ischaemic (1.9% vs. 1.8%, HR=1.02, 95% CI, 0.49–2.14; p=0.96) or bleeding (0.3% vs. 0.5%, HR=0.51, 95% CI, 0.09–2.78; p=0.44) outcomes. In conclusion, the DAPT score failed to show a differential treatment effect in patients receiving 6 or 12 months DAPT after contemporary drug-eluting stent implantation.

Ticagrelor versus prasugrel in patients with high on-clopidogrel treatment platelet reactivity after PCI: The ISAR-ADAPT-PF study

Patients with high on-treatment platelet reactivity (HTPR) on clopidogrel are at high risk for adverse cardiovascular events after percutaneous coronary intervention (PCI). The aim of the ISAR-ADAPT-PF study was to assess the antiplatelet efficacy of ticagrelor versus prasugrel in patients with HTPR on clopidogrel. In a prospective and randomized clinical study, 70 patients with HTPR on clopidogrel loading dose (LD) within 24 h post PCI were assigned to receive either ticagrelor [180 mg LD followed by 90 mg maintenance dose (MD) twice daily] or prasugrel (60 mg LD followed by 10 mg MD once daily). The adenosine diphosphate-induced platelet aggregation assessed on the Multiplate analyzer on day 2 after randomization (primary end point) was as follows: the mean difference between the two treatment groups was 6 aggregation units (AU) × min with an upper 95% confidence interval (CI) of 41 AU × min, which was greater than the predefined noninferiority margin of 18 AU × min (P for noninferiority = 0.29). However, no significant differences in absolute platelet reactivity levels between ticagrelor- versus prasugrel-treated patients at that time point were observed (138 ± 100 AU × min vs. 132 ± 64 AU × min, P for superiority = 0.77). In conclusion, neither drug was statistically more effective for inhibition of platelet aggregation in patients with HTPR on clopidogrel post PCI, although the study could not formally demonstrate the assumed noninferiority of ticagrelor versus prasugrel.

The impact of therapeutic hypothermia on on-treatment platelet reactivity and clinical outcome in cardiogenic shock patients undergoing primary PCI for acute myocardial infarction: Results from the ISAR-SHOCK registry

INTRODUCTION

Mild therapeutic hypothermia (TH) is standard of care after cardiac arrest of any cause. However, its impact on on-treatment platelet reactivity and clinical outcome in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock and undergoing PCI with P2Y12 receptor inhibitor treatment is less clear.

METHODS AND RESULTS

For the ISAR-SHOCK registry, 145 patients with AMI, cardiogenic shock and primary PCI in two centers (Deutsches Herzzentrum München and Klinikum rechts der Isar, Technical University Munich) between January 2009-May 2012 were analysed. Of these, 64 (44%) patients received TH treatment. The median [IQR] ADP-induced platelet aggregation following thienopyridine loading dose administration (clopidogrel in 95 and prasugrel in 50 patients) did not differ between the two groups (419 [283-684] for TH vs. 355 [207-710] AU x min for non-TH patients, P=0.22). After 30days follow-up, no significant differences were observed between both groups for mortality (42 vs. 44 %, HR: 0.93, 95% CI [0.56-1.53], p=0.77), MI (6 vs. 6%, HR: 0.99 95% CI [0.27-3.7], p=0.99) and TIMI minor bleedings (17 vs. 17%, HR 0.99 95% CI [0.45-2.18], p=0.98). TIMI major bleedings were numerically higher in the TH vs. non-TH cohort (25 % vs. 12 %, HR: 2.1 95% CI [0.95-4.63], p=0.07). Three definite stent thrombosis (ST) were observed in this registry and all STs occurred in the TH group of patients (p=0.09).

CONCLUSION

Results of this registry suggest that TH does not negatively impact on platelet reactivity in shock patients receiving either clopidogrel or prasugrel. The numerically higher rate of major bleedings and the clustering of STs in the TH cohort warrant further investigation.

Comparison of vascular closure devices vs manual compression after femoral artery puncture: the ISAR-CLOSURE randomized clinical trial

IMPORTANCE

The role of vascular closure devices (VCD) for the achievement of hemostasis in patients undergoing transfemoral coronary angiography remains controversial.

OBJECTIVE

To compare outcomes with the use of 2 hemostasis strategies after diagnostic coronary angiography performed via transfemoral access-a VCD-based strategy with 2 types of devices, an intravascular device and an extravascular device, vs standard manual compression. The primary hypothesis to be tested was that femoral hemostasis achieved through VCD is noninferior to manual compression in terms of vascular access-site complications. A secondary objective was the comparison of the 2 types of VCD.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, large-scale, multicenter, open-label clinical trial. We enrolled 4524 patients undergoing coronary angiography with a 6 French sheath via the common femoral artery from April 2011 through May 2014 in 4 centers in Germany. Last 30-day follow-up was performed in July 2014.

INTERVENTIONS

After angiography of the access site, patients were randomized to hemostasis with an intravascular VCD, extravascular VCD, or manual compression in a 1:1:1 ratio.

MAIN OUTCOMES AND MEASURES

Primary end point: the composite of access site-related vascular complications at 30 days after randomization with a 2% noninferiority margin. Secondary end points: time to hemostasis, repeat manual compression, and VCD failure. An α-level of .025 was chosen for primary and secondary comparisons.

RESULTS

Of the 4524 enrolled patients, 3015 were randomly assigned to a VCD group (1509 received intravascular VCD and 1506 received extravascular VCD) and 1509 patients were randomly assigned to the manual compression group. Before hospital discharge, duplex sonography of the access site was performed in 4231 (94%) patients. The primary end point was observed in 208 patients (6.9%) assigned to receive a VCD and 119 patients (7.9%) assigned to manual compression (difference, -1.0% [1-sided 97.5% CI, 0.7%]; P for noninferiority<.001). Time to hemostasis was significantly shorter in patients with VCD (1 minute [interquartile range {IQR}, 0.5-2.0]), vs manual compression (10 minutes [IQR, 10-15]; P < .001). Time to hemostasis was significantly shorter among patients with intravascular VCD (0.5 minute [IQR, 0.2-1.0]), vs extravascular VCD (2.0 minutes [IQR, 1.0-2.0]; P <.001) and closure device failure was also significantly lower among those with intravascular vs extravascular VCD (80 patients [5.3%], vs 184 patients [12.2%]; P < .001).

CONCLUSIONS AND RELEVANCE

In patients undergoing transfemoral coronary angiography, VCDs were noninferior to manual compression in terms of vascular access-site complications and reduced time to hemostasis.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01389375.

A comparative cohort study on personalised antiplatelet therapy in PCI-treated patients with high on-clopidogrel platelet reactivity. Results of the ISAR-HPR registry

In clopidogrel-treated patients undergoing percutaneous coronary intervention (PCI), high platelet reactivity (HPR) is associated with a higher risk for thrombotic events including stent thrombosis (ST). A personalised therapy with selective intensification of treatment may improve HPR patients´ outcome in this setting although recent randomised trials are against this hypothesis. The aim of the ISAR-HPR registry was to assess whether clopidogrel-treated HPR patients benefit from selective intensification of P2Y12 receptor inhibition. For the registry, outcomes were compared between two cohorts. We identified 428 clopidogrel treated HPR patients (AU x min ≥468 on the Multiplate analyser) between 2007-2008 (historical control cohort) without a change of treatment based on platelet function (PF) testing results. Between 2009-2011, we identified 571 HPR patients (guided therapy cohort) and used this information for guidance and selective intensification of P2Y12 receptor directed treatment (reloading with clopidogrel, switch to prasugrel, re-testing) in a setting of routine PF testing. The primary outcome was the composite of death from any cause or ST after 30 days. Major bleeding according to TIMI criteria was also monitored. The incidence of the primary outcome was significantly lower in the guided vs the control cohort (7 [1.2%] vs 16 [3.7%] events; HR 0.32, 95% CI 0.13-0.79; p=0.009). The incidence of major bleeding was numerically but not statistically higher in the guided vs the control cohort (1.9 vs 0.7%; p=0.10). In conclusion, present findings are in support for a PF testing guided antiplatelet therapy with selective intensification of P2Y12 receptor inhibition. The issue of personalised antiplatelet treatment warrants further investigation in randomized and well-controlled clinical trials.

Comparison of prasugrel and bivalirudin vs clopidogrel and heparin in patients with ST-segment elevation myocardial infarction: Design and rationale of the Bavarian Reperfusion Alternatives Evaluation (BRAVE) 4 trial

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

Randomized comparison of ticagrelor versus prasugrel in patients with acute coronary syndrome and planned invasive strategy--design and rationale of the iNtracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment (ISAR-REACT) 5 trial

In acute coronary syndromes (ACS), a dual antiplatelet regimen with an adenosine diphosphate (ADP) receptor antagonist plus aspirin has become the cornerstone of treatment. The third-generation thienopyridine prasugrel and the cyclopentyl-triazolo-pyrimidine ticagrelor provide a greater, more rapid and consistent platelet inhibition compared to their predecessor clopidogrel. Based on their advantages over clopidogrel in two landmark studies, both drugs received a class I recommendation for their use in ACS patients with and without ST segment elevation. Due to differences in ACS populations and conditions investigated, the relative merits of ticagrelor versus prasugrel in the treatment of ACS patients with planned invasive strategy cannot be reliably estimated from independent trials. To date, no direct head-to-head comparison of ticagrelor and prasugrel in terms of clinical outcome exists. The aim of this multicenter, randomized, open-label trial is to assess whether ticagrelor is superior to prasugrel in ACS patients with planned invasive strategy.

Impact of smoking on antiplatelet effect of clopidogrel and prasugrel after loading dose and on maintenance therapy

BACKGROUND

Pharmacodynamic studies reported an amplified on-clopidogrel platelet inhibition in smokers potentially caused by an increased metabolic drug activation via induction of cytochrome P450 1A2. The aims of this analysis were to evaluate the impact of smoking on the antiplatelet effect of clopidogrel and prasugrel and to test the potential interaction of smoking with the treatment effect of these drugs.

METHODS

A variety of platelet function results was analyzed from 2 large cohorts of patients undergoing coronary intervention after loading with clopidogrel 600 mg (n = 2,533 and n = 1,996), a cohort of patients undergoing dose adaptation from 75 to 150 mg according to response to clopidogrel (n = 117) and a crossover trial comparing clopidogrel 150 mg with prasugrel 10 mg (n = 87). Linear regression analyses were used to test the impact of smoking on platelet function and to identify independent predictors of on-treatment platelet reactivity. The potential interaction of smoking with the clinical effect of clopidogrel versus prasugrel was analyzed in the TRITON-TIMI 38 cohort (n = 13,608).

RESULTS

No significant association of smoking with platelet reactivity on clopidogrel was seen in unadjusted and adjusted analyses. The variables most consistently associated with on-clopidogrel platelet function were age, sex, diabetes, and body mass index. There was no significant interaction of smoking status at presentation with the clinical efficacy of prasugrel versus clopidogrel (P for interaction = .39).

CONCLUSIONS

Smoking does not impact on platelet reactivity in patients after loading or on different maintenance doses of clopidogrel. The clinical treatment effect of clopidogrel versus prasugrel is not affected by smoking status at presentation.

Stability of the high on-treatment platelet reactivity phenotype over time in clopidogrel-treated patients

Interindividual response variability to clopidogrel treatment is a well established phenomenon. In recent studies and ongoing large-scale trials where patients with high on-treatment platelet reactivity (HPR) to clopidogrel are being randomised to an intensified antiplatelet treatment, confirmation of the HPR phenotype is based on one single platelet function assessment. The stability of the HPR phenotype over time has never been investigated but should be considered crucial for justification of intensified antiplatelet treatment regimens beyond clinical trials. The goal of this study was to test for the stability of the HPR phenotype over time in clopidogrel-treated patients. Patients (n=31) under chronic clopidogrel treatment (75 mg/day) were investigated by serial adenosine diphosphate (ADP)-induced platelet aggregation assessment with multiple electrode aggregometry (MEA) on a Multiplate analyser and light transmission aggregometry (LTA) at three different time points (once per week) during monitored antiplatelet treatment. On the basis of a cut-off level approach (468 AU*min for MEA, 53% for LTA) patients were classified into patients with (n=27) or without (n=4) HPR. For MEA, the phenotype was stable in 93.5% (n=29) of patients whereas 6.5% (n=2) crossed the cut-off level. For LTA, the phenotype was stable in 68% (n=21) of patients whereas 32% (n=10) patients crossed the cut-off level (chi-square P=0.01 for comparison of phenotype stability between both assays). In conclusion, the HPR phenotype is stable over time in the majority of clopidogrel-treated patients. Comparative assessment of phenotype stability across available platelet function assays warrants further investigation.

Association between inflammatory biomarkers and platelet aggregation in patients under chronic clopidogrel treatment

Inflammatory processes in the vessel wall are associated with progression of atherosclerosis and myocardial infarction. Both high levels of C-reactive protein (CRP)and high on-clopidogrel treatment platelet reactivity (HPR) have been linked to an increased risk of ischaemic events after percutaneous coronary intervention (PCI). The aim of this study was to explore the association between biomarker levels of inflammation and platelet reactivity. Stable patients (n=1,223) eligible for this study were under chronic antiplatelet treatment with aspirin and clopidogrel due to prior coronary stent placement. ADP-induced platelet aggregation (in AU*min) was measured on a Multiplate analyser. The primary outcome measure of this retrospective study was the ADP-induced platelet aggregation in patients with versus those without elevated CRP levels. Of the patients 15.5% (n=189) showed elevated CRP levels (≥5 mg/l). Platelet aggregation (median [interquartile range]) was significantly higher in patients with elevated CRP levels compared to patients with normal (<5 mg/l) CRP levels (305 [202-504] AU*min vs. 218 [144-384] AU*min; p<0.001).A multivariable linear regression model that adjusted for known predictors of HPR confirmed a significant independent association between elevated CRP levels and high ADP-induced platelet aggregation values (p=0.0002).Elevated WBC count and fibrinogen levels were also associated with higher platelet aggregation values (p<0.001 for both). In conclusion, elevated levels of CRP, WBC count and fibrinogen were significantly associated with high platelet reactivity in patients under chronic clopidogrel treatment. Whether a direct relation between platelets and inflammation exists, as well as the clinical impact of our results, warrants further investigations.

Isolated and interactive impact of common CYP2C19 genetic variants on the antiplatelet effect of chronic clopidogrel therapy

BACKGROUND

With the cytochrome P450 CYP2C19*2 (*2) allelic variant resulting in complete loss of enzyme function and the CYP2C19*17 (*17) variant being linked to increased transcriptional activity with extensive metabolism of CYP2C19 substrates, two common variants of the CYP2C19 gene have been explored recently. Currently, the isolated and interactive impacts of both variants on the antiplatelet effects of chronic clopidogrel therapy are unknown.

OBJECTIVES

The aim of this study was to assess the isolated and interactive impacts of *2 and *17 on clopidogrel responsiveness in patients under clopidogrel maintenance treatment.

METHODS

Patients (n=986) eligible for this study were under therapy with coronary stent-related chronic treatment with aspirin and clopidogrel. The ADP-induced platelet aggregation was measured on a Multiplate analyzer (in AU*min), and genotypes were determined with a TaqMan assay.

RESULTS

Platelet aggregation values were significantly higher in carriers of at least one *2 allele than in homozygous wild-type allele carriers (P<0.001). For *17, platelet aggregation values were significantly lower in carriers of at least one *17 allele than in homozygous wild-type patients (P=0.01). A gene-dose effect was observed for both variants, with a pronounced effect of the mutant allele (*2 or *17) in homozygous patients being seen. For the interactive effect of both variants on platelet aggregation values, a gradual increase in platelet aggregation values was observed from (+)*17/(-)*2 patients, who exhibited the lowest values (median of 207 AU*min) to (-)*17/(-)*2, (+)*17/(+)*2 and (-)*17/(+)*2 patients, who exhibited the highest values (median of 309 AU*min) (P<0.001).

CONCLUSIONS

*2 and *17 allele carriage are independent predictors for the antiplatelet effect of chronic clopidogrel therapy.

Platelet response to clopidogrel and restenosis in patients treated predominantly with drug-eluting stents

BACKGROUND

Preclinical studies suggest a relationship between early thrombotic response after vascular injury and later development of restenosis. The aim of this study was to assess the impact of platelet response to clopidogrel on the risk of restenosis after drug-eluting stenting (DES).

METHODS

A total of 1,608 consecutive patients were previously enrolled in a study on the relation between platelet reactivity and outcomes after DES. All patients received a loading dose of 600 mg clopidogrel. Blood samples for the assessment of adenosine diphosphate-induced platelet aggregation with multiple electrode platelet aggregometry were drawn directly before percutaneous coronary intervention. Clopidogrel low response was defined as upper quintile of multiple electrode platelet aggregometry measurements. Accordingly, 323 patients (20%) were considered as low and 1,285 (80%) as normal responders. Primary end point of the present study was target lesion revascularization at 1 year. Secondary end points included binary angiographic restenosis and late lumen loss at 6- to 8-month angiography.

RESULTS

Target lesion revascularization rates were comparable in both groups (10.9% vs 9.5%, hazard rate [HR] 1.2, 95% CI 0.8-1.7, P = .441). Follow-up angiography revealed no difference in binary angiographic restenosis (13.9% vs 15.9%, P = .445) and late lumen loss (0.32 +/- 0.64 vs 0.35 +/- 0.63 mm, P = .477). Low responders had significantly more stent thromboses (2.5% vs 0.5%, HR 5.4, 95% CI 1.9-15.6, P = .002), Q wave myocardial infarctions (2.5% vs 0.6%, HR 4.0, 95% CI 1.5-10.7, P = .005), and ischemic strokes (1.3% vs 0.2%, HR 5.4, 95% CI 1.2-24.0, P = .028) at 1 year.

CONCLUSION

Low platelet responsiveness to clopidogrel, a known predictor of thrombotic complications, does not have a significant impact on restenosis after DES.

Oral anticoagulation with coumarin derivatives and antiplatelet effects of clopidogrel

AIMS

A relevant proportion of patients receiving aspirin and clopidogrel after percutaneous coronary intervention (PCI) also require oral anticoagulation with a coumarin derivative such as phenprocoumon. Both clopidogrel and phenprocoumon are metabolized by the hepatic cytochrome P450 system and a drug-drug interaction may exist at this level. The aim of this study was to investigate the impact of phenprocoumon on the antiplatelet effects of clopidogrel in patients with coronary artery disease.

METHODS AND RESULTS

Patients (n = 1223) eligible for this study were under dual maintenance antiplatelet treatment with aspirin and clopidogrel. Adenosine diphosphate-induced platelet aggregation (in AU*min) was measured with multiple electrode platelet aggregometry on a Multiplate analyzer (Dynabyte, Munich, Germany). From the entire study population, 124 (10.1%) patients were under concomitant phenprocoumon treatment at the time point of platelet function testing. Platelet aggregation (median [interquartile range]) was significantly higher in patients with (n = 124) concomitant phenprocoumon treatment compared with patients without (n = 1099) phenprocoumon treatment (308 [190-493] AU*min vs. 224 [145-390] AU*min; P = 0.0001, adjusted P = 0.002).

CONCLUSION

Phenprocoumon significantly attenuates the antiplatelet effects of clopidogrel. The impact of this interaction on the risk of thrombotic and bleeding events after PCI requires further investigations.

Antiplatelet effects of clopidogrel and bleeding in patients undergoing coronary stent placement

BACKGROUND

In patients undergoing percutaneous coronary intervention (PCI), a link between bleeding and excess mortality has been demonstrated. A potential association of platelet response to clopidogrel and bleeding has not been well established yet.

OBJECTIVES

The aim of the present study was to assess the impact of clopidogrel responsiveness on the risk of bleeding in clopidogrel-treated patients undergoing PCI.

METHODS

Patients (n=2533) undergoing PCI after pretreatment with 600 mg of clopidogrel were enrolled in this study. Blood was obtained directly before PCI. Adenosine-diphosphate (ADP)-induced platelet aggregation was assessed on a Multiplate analyzer. The primary endpoint was the incidence of in-hospital Thrombolysis in Myocardial Infarction (TIMI) major bleeding and the secondary endpoint was in-hospital TIMI minor bleeding. Receiver-operator curve (ROC) analysis was used to derive the optimal platelet aggregation value defining enhanced clopidogrel responders for the association of measurements with major bleeding.

RESULTS

Thirty-four (1.3%) major bleeding events and 137 (5.4%) minor bleeding events were observed. The risk of a major bleeding was significantly higher in patients (n=975) with an enhanced response to clopidogrel as compared with the remaining patients (n=1558) (2.2 vs. 0.8%, unadjusted odds ratio (OR) 2.6, 95% confidence interval (CI) 1.3-5.2, P=0.005; adjusted OR 3.5, 95% CI 1.6-7.3, P=0.001). No significant differences between both groups were observed for the occurrence of minor bleeding events (P=0.68).

CONCLUSIONS

Enhanced clopidogrel responsiveness is associated with a higher risk of major bleeding. Whether guidance of antiplatelet treatment based on platelet function testing proves useful for avoiding bleeding events warrants further investigation.

Cytochrome 2C19*17 allelic variant, platelet aggregation, bleeding events, and stent thrombosis in clopidogrel-treated patients with coronary stent placement

BACKGROUND

The cytochrome P450 (CYP) 2C19 isoenzyme plays an important role in clopidogrel metabolization. A recently explored CYP2C19*17 allelic variant has been linked to increased transcriptional activity, resulting in extensive metabolization of CYP2C19 substrates, which may lead to an enhanced platelet response to clopidogrel treatment. The aim of this study was to assess the impact of CYP2C19*17 on ADP-induced platelet aggregation, the risk of bleeding, and stent thrombosis in clopidogrel-treated patients undergoing percutaneous coronary intervention.

METHODS AND RESULTS

The study population included 1524 patients undergoing percutaneous coronary intervention after pretreatment with 600 mg clopidogrel. Genotypes were determined with a TaqMan assay. ADP-induced platelet aggregation was assessed on a Multiplate analyzer. The primary clinical safety end point was the 30-day incidence of bleeding defined according to Thrombolysis in Myocardial Infarction criteria, and the primary clinical efficacy end point was the 30-day incidence of stent thrombosis. For both heterozygous (*wt/*17; n=546) and homozygous (*17/*17; n=76) allele carriers, significantly lower ADP-induced platelet aggregation values were found compared with wild-type homozygotes (*wt/*wt; n=902; P=0.039 and P=0.008, respectively). CYP2C19*17 allele carriage was significantly associated with an increased risk of bleeding; the highest risk was observed for CYP2C19*17 homozygous patients (P=0.01, chi(2) test for trend). Multivariate analysis confirmed the independent association of CYP2C19*17 allele carriage with platelet aggregation values (P<0.001) and the occurrence of bleeding (P=0.006). No significant influence of CYP2C19*17 on the occurrence of stent thrombosis was found (P=0.79).

CONCLUSIONS

CYP2C19*17 carrier status is significantly associated with enhanced response to clopidogrel and an increased risk of bleeding.

Clopidogrel response status assessed with Multiplate point-of-care analysis and the incidence and timing of stent thrombosis over six months following coronary stenting

Clopidogrel low-responsiveness assessed with multiple electrode platelet aggregometry (MEA) has been shown to be a strong and independent predictor of early stent thrombosis (ST) after coronary stenting. The relation of clopidogrel response status, as assessed with MEA, with incidence and timing of ST during an extended follow-up period has never been reported. Here, we report the six-month follow-up results of a prospective trial assessing clopidogrel responsiveness with MEA in patients undergoing percutaneous coronary intervention (PCI). A total of 1,608 consecutive patients with planned drug-eluting stent placement were enrolled in this study. Before PCI patients uniformly received 600 mg clopidogrel and blood was taken directly before PCI to measure ADP-induced platelet aggregation with MEA. The upper quintile (20%) of patients according to MEA measurements (n=323) was defined as clopidogrel low responders. Compared with normal responders (n=1,285), the cumulative incidence of definite ST within six months was significantly higher in low responders [2.5% vs. 0.4%; OR 6.5; 95% CI, 2.4-17.0; P<0.001]. The combined incidence of definite or probable ST was higher as well in low vs. normal responders [4.1% vs. 0.7%; OR 5.8; 95% CI, 2.8-12.3; P<0.0001]. A significant inverse correlation of MEA values and the timing of definite or probable ST (in days) was observed (Spearman coefficient = -0.45; P=0.04) with events occurring earlier in the low-responder group. MEA measurements are highly predictive for the occurrence of ST during the first six months following coronary stenting. In the majority of clopidogrel low responders suffering ST, the ischaemic event occurs early in the course after the procedure.

Impact of proton pump inhibitors on the antiplatelet effects of clopidogrel

Patients receiving dual antiplatelet treatment with aspirin and clopidogrel are commonly treated with proton pump inhibitors (PPIs). Attenuating effects on platelet response to clopidogrel have been reported solely for the PPI omeprazole. PPIs differ in their metabolisation properties as well as their potential for drug-drug interactions. The aim of this study was to investigate the impact of different PPIs (pantoprazole, omeprazole, esomeprazole) on platelet response to clopidogrel in patients with previous coronary stent placement under chronic clopidogrel treatment. In a cross-sectional observational study, consecutive patients under clopidogrel maintenance treatment (n = 1,000) scheduled for a control coronary angiography were enrolled. Adenosine diphosphate (ADP)-induced platelet aggregation (in AU*min) was measured with multiple electrode platelet aggregometry (MEA). From the entire study population, 268 (26.8%) patients were under PPI treatment at the time point of platelet function testing (pantoprazole, n = 162; omeprazole, n = 64; esomeprazole, n = 42). Platelet aggregation (median [interquartile range]) was significantly higher in patients with omeprazole treatment (295.5 [193.5-571.2] AU*min) compared to patients without PPI treatment (220.0 [143.8-388.8] AU*min; p = 0.001). Platelet aggregation was similar in patients with pantoprazole (226.0 [150.0-401.5] AU*min) or esomeprazole (209.0 [134.8-384.8] AU*min) treatment compared to patients without PPI treatment (p = 0.69 and p = 0.88, respectively). Attenuating effects of concomitant PPI treatment on platelet response to clopidogrel were restricted to the use of omeprazole. No attenuating effects on platelet response to clopidogrel were observed for pantoprazole or esomeprazole. Specifically designed and randomized clinical studies are needed to define the impact of concomitant PPI treatment on adverse events after percutaneous coronary intervention.

Platelet reactivity after clopidogrel treatment assessed with point-of-care analysis and early drug-eluting stent thrombosis

OBJECTIVES

The aim of this prospective trial was to assess whether platelet reactivity to clopidogrel assessed with multiple electrode platelet aggregometry (MEA) correlates with the risk of early drug-eluting stent thrombosis (ST).

BACKGROUND

Studies using light transmission aggregometry (LTA) have shown that insufficient suppression of platelet reactivity to adenosine diphosphate (ADP) after clopidogrel treatment is associated with an increased risk of adverse cardiovascular events after percutaneous coronary intervention (PCI). However, LTA is time- and labor-intensive and inconvenient for the routine. A point-of-care assay with similar predictive power would be of great value.

METHODS

Between February 2007 and April 2008, a total of 1,608 consecutive patients with coronary artery disease and planned drug-eluting stent implantation were enrolled. Before PCI, all patients received 600 mg clopidogrel. Blood was obtained directly before PCI. The ADP-induced platelet aggregation was assessed in whole blood with MEA on a Multiplate analyzer (Dynabyte, Munich, Germany). The primary end point was definite ST at 30 days.

RESULTS

The upper quintile of patients according to MEA measurements (n = 323) was defined as clopidogrel low responders. Compared with normal responders (n = 1,285), low responders had a significantly higher risk of definite ST within 30 days (2.2% vs. 0.2%; odds ratio [OR]: 9.4; 95% confidence interval [CI]: 3.1 to 28.4; p < 0.0001). Mortality rates were 1.2% in low versus 0.4% in normal responders (OR: 3.2; 95% CI: 0.9 to 11.1; p = 0.07). The composite of death or ST was higher in low versus normal responders (3.1% vs. 0.6%; OR: 5.1; 95% CI: 2.2 to 11.6; p < 0.001).

CONCLUSIONS

Low response to clopidogrel assessed with MEA is significantly associated with an increased risk of ST. Further studies are warranted to evaluate the ability of MEA to guide antiplatelet therapy in patients undergoing PCI.

Cytochrome P450 2C19 loss-of-function polymorphism and stent thrombosis following percutaneous coronary intervention

AIMS

Several studies have demonstrated that the mutant *2 allele of the CYP2C19 681G>A loss-of-function polymorphism is associated with diminished metabolization of clopidogrel into its active thiol metabolite and an attenuated platelet response to clopidogrel treatment. It is not known whether patients carrying the mutant CYP2C19*2 allele have a higher risk of stent thrombosis (ST) compared with homozygous CYP2C19*1 wild-type allele carriers following percutaneous coronary intervention (PCI). The aim of this study was to assess the impact of the CYP2C19 681G>A loss-of-function polymorphism on ST following PCI performed after pre-treatment with clopidogrel.

METHODS AND RESULTS

The study population included 2485 consecutive patients undergoing coronary stent placement after pre-treatment with 600 mg of clopidogrel. Genotypes were determined with a TaqMan assay. The primary endpoint of the study was the incidence of definite ST within 30 days following PCI. Of the patients studied, 1805 (73%) were CYP2C19 wild-type homozygotes (*1/*1) and 680 (27%) carried at least one *2 allele (*1/*2 or *2/*2). The cumulative 30-day incidence of ST was significantly higher in CYP2C19*2 allele carriers (*1/*2 or *2/*2) vs. CYP2C19 wild-type homozygotes (*1/*1) [10 patients (1.5%) in CYP2C19*2 allele carriers vs. 7 (0.4%) in CYP2C19 wild-type homozygotes (*1/*1), HR 3.81, 95% CI 1.45-10.02, P = 0.007; P = 0.006 after adjustment for confounding variables]. The risk of ST was highest (2.1%) in patients with the CYP2C19 *2/*2 genotype (P = 0.002).

CONCLUSION

CYP2C19*2 carrier status is significantly associated with an increased risk of ST following coronary stent placement.

N-Acetylserotonin prevents the hypotension induced by bacterial lipopolysaccharides in the rat

Nitric oxide is produced by the NO synthase, which catalyses the conversion of arginine to citrulline and NO using tetrahydrobiopterin as an essential cofactor. N-Acetylserotonin, an inhibitor of the tetrahydrobiopterin biosynthesis, given 30 min before bacterial lipopolysaccharide to anesthetized rats, inhibited both the decrease in blood pressure and the increase in nitrite plasma levels induced by lipopolysaccharide. Thus, during endotoxemia the availability of tetrahydrobiopterin appears to be essential for the activity of NO synthase.