Biological efficacy of a 600 mg loading dose of clopidogrel in ST-elevation myocardial infarction

Infarct size following loading with Ticagrelor/Prasugrel versus Clopidogrel in ST-segment elevation myocardial infarction

BACKGROUND

Treatment with newer direct-acting anti-platelet drugs (Ticagrelor and Prasugrel) prior to primary percutaneous coronary intervention (PCI) is associated with improved outcome in patients with ST-segment elevation myocardial infarction (STEMI) when compared with Clopidogrel. We compared infarct size following treatment with Ticagrelor/Prasugrel versus Clopidogrel in the DANish trial in Acute Myocardial Infarction (DANAMI-3) population of STEMI patients treated with primary PCI.

METHODS AND RESULTS

Patients were loaded with Clopidogrel, Ticagrelor or Prasugrel in the ambulance before primary PCI. Infarct size and myocardial salvage index were calculated using cardiac magnetic resonance (CMR) during index admission and at three-month follow-up. Six-hundred-and-ninety-three patients were included in this analysis. Clopidogrel was given to 351 patients and Ticagrelor/Prasugrel to 342 patients. The groups were generally comparable in terms of baseline and procedural characteristics. Median infarct size at three-month follow-up was 12.9% vs 10.0%, in patients treated with Clopidogrel and Ticagrelor/ Prasugrel respectively (p < 0.001), and myocardial salvage index was 66% vs 71% (p < 0.001). Results remained significant in a multiple regression model (p < 0.001).

CONCLUSIONS

Pre-hospital loading with Ticagrelor or Prasugrel compared to Clopidogrel, was associated with smaller infarct size and larger myocardial salvage index at three-month follow-up in patients with STEMI treated with primary PCI.

Efficacy of Clopidogrel-Aspirin Therapy for Stroke Does Not Exist in C YP2C19 Loss-of-Function Allele Noncarriers With Overweight/Obesity

Background and Purpose—

The role of dual-antiplatelet therapy with clopidogrel plus aspirin has been demonstrated to substantially decrease the risk of recurrent stroke among patients with minor stroke and transient ischemic attack. We aimed to determine whether the efficacy of clopidogrel-aspirin therapy among patients with minor stroke / transient ischemic attack was influenced by the stratification of CYP2C19 genotype and body mass index (BMI).

Methods—

CYP2C19 loss-of-function allele (LoFA) carriers were defined as patients with either LoFA of *2 or *3. Low/normal weight and overweight/obesity was defined as BMI <25 and ≥25 kg/m 2 , respectively. Primary outcome was defined as stroke recurrence at 3 months.

Results—

In a total of 2933 patients, there were 1726 (58.8%) LoFA carriers and 1275 (43.5%) patients with overweight/obesity (BMI ≥25 kg/m 2 ). Stratified analyses by LoFA carrying status and BMI, hazard ratios (hazard ratios 95% CIs) of the clopidogrel-aspirin therapy for stroke recurrence were 0.90 (0.60–1.36), 0.87 (0.56–1.35), 0.65 (0.39–1.09), and 0.40 (0.22–0.71) among subgroups of LoFA carriers with overweight/obesity, LoFA carriers with low/normal weight, LoFA noncarriers with overweight/obesity, and LoFA noncarriers with low/normal weight, respectively, with P =0.049 for interaction.

Conclusions—

Efficacy of clopidogrel-aspirin therapy in reducing the risk of stroke recurrence is not present in CYP2C19 LoFA noncarriers with overweight/obesity. Our study suggests that BMI significantly influences the correlation between CYP2C19 genotype and efficacy of clopidogrel-aspirin therapy.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00979589.

Planned use of GP IIb/IIIa inhibitors is safe and effective during implantation of the Absorb Bioresorbable Vascular Scaffold

Bioresorbable Vascular Scaffolds (BVS) have the potential for adaptive vessel remodeling, restoration of vasomotion, and late luminal enlargement, thus allowing them to circumvent target lesion failures associated with bare metal stents (BMS) and drug-eluting stents (DES). However, recent data has shown a concerning increase in BVS-associated scaffold thrombosis (ScT) compared to DES. Upfront administration of GP IIb/IIIa inhibitors (GPIs) has shown to reduce early stent thrombosis (ST) compared to standard of care in BMS and DES. Since the use of GPIs was limited in BVS studies, the effect of GPIs on the rate of BVS-associated ScT is largely unknown. This is the first study investigating whether a planned use of GPIs during implantation of the Absorb BVS represents a safe and effective strategy in reducing ScT. In a retrospective chart review of 22 patients undergoing PCI with BVS implantation and planned GPI administration, no acute ScT, in-hospital MACE, or in-hospital major/minor bleeding events were observed. Bleeding reduction strategies such as shorter GPI infusion and radial access were implemented. This study provides valuable preliminary evidence on the benefit and safety in using planned GPI administration to reduce the incidence of ScT after implantation of BVS.

Transferring from clopidogrel loading dose to prasugrel loading dose in acute coronary syndrome patients

High on-treatment platelet reactivity (HPR) has been identified as an independent risk factor for ischaemic events. The randomised, doubleblind, TRIPLET trial included a pre-defined comparison of HPR in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) following a placebo/600-mg clopidogrel loading dose (LD) immediately before a subsequent prasugrel 60-mg or 30-mg LD. Platelet reactivity was assessed using the VerifyNow® P2Y12 assay (P2Y12 Reaction Units, PRU) within 24 hours (h) following the placebo/clopidogrel LD (immediately prior to prasugrel LD), and at 2, 6, 24, 72 h following prasugrel LDs. The impact of CYP2C19 predicted metaboliser phenotype (extensive metaboliser [EM] and reduced metabolisers [RM]) on HPR status was also assessed. HPR (PRU ≥240) following the clopidogrel LD (prior to the prasugrel LD) was 58.5% in the combined clopidogrel LD groups. No significant difference was noted when stratified by time between the clopidogrel and prasugrel LDs (≤6 hs vs >6 h). At 6 h following the 2nd loading dose in the combined prasugrel LD groups, HPR was 7.1%, with 0% HPR by 72 h. There was no significant effect of CYP2C19 genotype on pharmacodynamic (PD) response following either prasugrel LD treatments at any time point, regardless of whether it was preceded by a clopidogrel 600-mg LD. In conclusion, in this study, patients with ACS intended for PCI showed a high prevalence of HPR after clopidogrel 600-mg LD regardless of metaboliser status. When prasugrel LD was added, HPR decreased substantially by 6 h, and was not seen by 72 h.

Onset of optimal P2Y12-ADP receptor blockade after ticagrelor and prasugrel intake in Non-ST elevation acute coronary syndrome

Pretreatment with a loading dose (LD) of clopidogrel or ticagrelor before percutaneous coronary intervention (PCI) in acute coronary syndrome (ACS) is supported by the guidelines, but debated following a recent meta-analysis on clopidogrel pretreatment and the ACCOAST trial. In this trial prasugrel pretreatment failed to reduce ischaemic events. The timing of optimal platelet reactivity (PR) inhibition of ticagrelor and prasugrel in non ST-elevation ACS (NSTE ACS) is yet undetermined. In the present study, we aimed to investigate the delay required to reach optimal PR inhibition in NSTE ACS following a LD of ticagrelor or prasugrel. Consecutive patients undergoing PCI for NSTE ACS were randomised in this monocentre study. The Vasodilatorphosphoprotein index (VASP) was used to measure PR before the LD and then at 30 minutes, 1, 2, 4 and 24 hours (h) post-LD. Optimal PR inhibition was defined as a VASP< 50 %. We randomised 24 patients to ticagrelor or prasugrel LD. One hour after the LD, 29 % of patients had a VASP > 50 % (ticagrelor and prasugrel: 25 vs 33 %; p=0.7). Optimal PR inhibition was obtained 2 h after the LD in both groups (12/12 with ticagrelor and 11/12 with prasugrel). At that time, the mean VASP index was 19 ± 16 % (95 %CI: 12–25). Maximal PR inhibition was reached after 4 h: 11 ± 10 % (95 %CI: 6–15). In NSTE ACS undergoing PCI a LD of ticagrelor or prasugrel given during the procedure provides optimal P2Y12-ADP receptor blockade in 2 h and maximal inhibition within 4 h.

Pharmacodynamic effects of standard dose prasugrel versus high dose clopidogrel in non-diabetic obese patients with coronary artery disease

Increased body weight is independently associated with impaired clopidogrel pharmacodynamic (PD) response. Prasugrel has more potent PD effects compared with clopidogrel, although its PD effects in obese patients are unknown. The aim of this prospective, randomised, study was to compare the PD effects of standard-dose prasugrel [60 mg loading dose (LD)/10 mg daily maintenance dose (MD)] with highdose clopidogrel (900 mg LD/150 mg daily MD) in non-diabetic obese [body mass index (BMI) ≥30 kg/m2] patients, with coronary artery disease (CAD) on aspirin therapy. PD assessments (baseline, 2 hours post-LD and 6 ± 2 days after MD) were conducted using four platelet function assays, and the platelet reactivity index (PRI) assessed by VASP was used for sample size estimation. A total of 42 patients with a BMI of 36.42 ± 5.6 kg/m2 completed the study. There were no differences in baseline PD measures between groups. At 2 hours post-LD, prasugrel was associated with lower PRI compared with clopidogrel (24.3 ± 5.5 vs 58.7 ± 5.7, p≤0.001), with consistent findings for all assays. At one-week, PRI values on prasugrel MD were lower than clopidogrel MD without reaching statistical significance (34.7 ± 5.8 vs 42.9 ± 5.8, p=0.32), with consistent findings for all assays. Accordingly, rates of high on-treatment platelet reactivity were markedly reduced after prasugrel LD, but not after MD. In conclusion, in non-diabetic obese patients with CAD, standard prasugrel dosing achieved more potent PD effects than high-dose clopidogrel in the acute phase of treatment, but this was not sustained during maintenance phase treatment. Whether an intensified prasugrel regimen is required in obese patients warrants investigation.

Baseline characteristics, adenosine diphosphate receptor inhibitor treatment patterns, and in-hospital outcomes of myocardial infarction patients undergoing percutaneous coronary intervention in the prospective Canadian Observational AntiPlatelet sTudy (COAPT)

BACKGROUND

Contemporary use of dual antiplatelet therapy and consistency with guideline recommendations in acute coronary syndrome patients undergoing percutaneous coronary intervention (PCI) have not been well characterized.

METHODS

The COAPT was a prospective, observational, multicenter, longitudinal study of patients with myocardial infarction (MI) undergoing PCI. Baseline characteristics, treatment patterns, processes of care, factors associated with switching to and from novel adenosine diphosphate receptor inhibitors (ADPris), and in-hospital outcomes are described.

RESULTS

Among 2,179 MI patients undergoing PCI during their index hospitalization, 1,328 (60.9%) had ST elevation. Initial ADPri use included clopidogrel in 1,812 (83.2%), prasugrel in 125 (5.7%), and ticagrelor in 242 (11.1%). At discharge, 1,597 patients (73.4%) were prescribed clopidogrel, 220 (10.1%) prasugrel, and 358 (16.5%) ticagrelor. Switching between ADPri therapies during the index hospitalization occurred in 15.3%, 22.4%, and 25.2% of patients initially started on clopidogrel, prasugrel, and ticagrelor, respectively. Most switches over the 15-month study period occurred during the index admission (16.8% of patients vs 4.4% switches postdischarge). Major adverse cardiovascular events occurred in 7.5% of patients during the index hospitalization. In-hospital bleeding events occurred in 6.0% of patients and most were mild.

CONCLUSIONS

Despite randomized trial evidence and guideline recommendations, only a minority of Canadian MI patients undergoing PCI initially received or were discharged on one of the newer ADPri agents. These findings suggest an opportunity to improve upon the appropriate selection of the ADPris at index hospitalization and discharge in Canadian MI patients undergoing PCI.

Characterization of the platelet transcriptome by RNA sequencing in patients with acute myocardial infarction

Transcripts in platelets are largely produced in precursor megakaryocytes but remain physiologically active as platelets translate RNAs and regulate protein/RNA levels. Recent studies using transcriptome sequencing (RNA-seq) characterized the platelet transcriptome in limited number of non-diseased individuals. Here, we expand upon these RNA-seq studies by completing RNA-seq in platelets from 32 patients with acute myocardial infarction (MI). Our goals were to characterize the platelet transcriptome using a population of patients with acute MI and relate gene expression to platelet aggregation measures and ST-segment elevation MI (STEMI) (n = 16) vs. non-STEMI (NSTEMI) (n = 16) subtypes. Similar to other studies, we detected 9565 expressed transcripts, including several known platelet-enriched markers (e.g. PPBP, OST4). Our RNA-seq data strongly correlated with independently ascertained platelet expression data and showed enrichment for platelet-related pathways (e.g. wound response, hemostasis, and platelet activation), as well as actin-related and post-transcriptional processes. Several transcripts displayed suggestively higher (FBXL4, ECHDC3, KCNE1, TAOK2, AURKB, ERG, and FKBP5) and lower (MIAT, PVRL3, and PZP) expression in STEMI platelets compared to NSTEMI. We also identified transcripts correlated with platelet aggregation to TRAP (ATP6V1G2, SLC2A3), collagen (CEACAM1, ITGA2), and ADP (PDGFB, PDGFC, ST3GAL6). Our study adds to current platelet gene expression resources by providing transcriptome-wide analyses in platelets isolated from patients with acute MI. In concert with prior studies, we identify various genes for further study in regards to platelet function and acute MI. Future platelet RNA-seq studies examining more diverse sets of healthy and diseased samples will add to our understanding of platelet thrombotic and non-thrombotic functions.

Biolimus-eluting stents with biodegradable polymer versus bare-metal stents in acute myocardial infarction: two-year clinical results of the COMFORTABLE AMI trial

BACKGROUND

This study sought to determine whether the 1-year differences in major adverse cardiac event between a stent eluting biolimus from a biodegradable polymer and bare-metal stents (BMSs) in the COMFORTABLE trial (Comparison of Biolimus Eluted From an Erodible Stent Coating With Bare Metal Stents in Acute ST-Elevation Myocardial Infarction) were sustained during long-term follow-up.

METHODS AND RESULTS

A total of 1161 patients were randomly assigned to biolimus-eluting stent (BES) and BMS at 11 centers, and follow-up rates at 2 years were 96.3%. A subgroup of 103 patients underwent angiography at 13 months. At 2 years, differences in the primary end point of cardiac death, target-vessel myocardial infarction, and target lesion revascularization continued to diverge in favor of BES-treated patients (5.8%) compared with BMS-treated patients (11.9%; hazard ratio = 0.48; 95% confidence interval, 0.31-0.72; P < 0.001) with a significant risk reduction during the second year of follow-up (hazard ratio 1-2 years = 0.45; 95% confidence interval, 0.20-1.00; P = 0.049). Differences in the primary end point were driven by a reduction in target lesion revascularization (3.1% versus 8.2%; P < 0.001) and target-vessel reinfarction (1.3% versus 3.4%; P = 0.023). The composite of death, any reinfarction and revascularization (14.5% versus 19.3%; P = 0.03), and cardiac death or target-vessel myocardial infarction (4.2% versus 7.2%; P = 0.036) were less frequent among BES-treated patients compared with BMS-treated patients. The 13-month angiographic in-stent percent diameter stenosis amounted to 12.0 ± 7.2 in BES- and 39.6 ± 25.2 in BMS-treated lesions (P < 0.001).

CONCLUSIONS

Among patients with ST-segment-elevation myocardial infarction undergoing primary percutaneous coronary intervention, BES continued to improve cardiovascular events compared with BMS beyond 1 year.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NTC00962416.

Impact of mild hypothermia on platelet responsiveness to aspirin and clopidogrel: an in vitro pharmacodynamic investigation

The combination of percutaneous coronary intervention (PCI) and therapeutic hypothermia in comatose patients after cardiac arrest due to an acute coronary syndrome has been reported to be safe and effective. However, recent investigations suggest that hypothermia may be associated with impaired response to clopidogrel and greater risk of thrombotic complications after PCI. This investigation aimed to evaluate the effect of hypothermia on the pharmacodynamic response of aspirin and clopidogrel in patients (n = 20) with ST elevation myocardial infarction undergoing primary PCI. Higher platelet reactivity (ADP stimulus) was observed in samples incubated at 33 °C compared with those at 37 °C (multiple electrode aggregometry, 235.2 ± 31.4 AU×min vs. 181.9 ± 30.2 AU×min, p < 0.001; VerifyNow P2Y12, 172.9 ± 20.3 PRU vs. 151.0 ± 19.3 PRU, p = 0.004). Numerically greater rates of clopidogrel poor responsiveness were also observed at 33 °C. No differences were seen in aspirin responsiveness. In conclusion, mild hypothermia was associated with reduced clopidogrel-mediated platelet inhibition with no impact on aspirin effects.

CLINICAL RELEVANCE

Mild therapeutic hypothermia is associated with impaired response to clopidogrel therapy, which might contribute to increase the risk of thrombotic events in ACS comatose patients undergoing PCI.

Combined cardioprotectant and antithrombotic actions of platelet P2Y12 receptor antagonists in acute coronary syndrome: just what the doctor ordered

Since the P2Y12 receptor antagonists were first introduced, they have been extensively tested in patients with acute coronary syndrome and are now standard of care. These antiplatelet drugs are very effective in reducing subsequent cardiovascular events, stent thromboses, and mortality in patients with acute myocardial infarction undergoing reperfusion therapy. Although the prevailing view is that their benefit derives from their antithrombotic properties, other unrelated pleiotropic effects appear to be equally beneficial. Accumulating clinical and animal evidence indicates that, if present at the time of reperfusion, these drugs have a direct anti-infarct effect similar to that of ischemic postconditioning. Four oral antagonists have been developed in rapid succession: ticlopidine, clopidogrel, prasugrel, and ticagrelor. Each agent had a more consistent and rapid onset of action than the previous one, and this has correlated with improved clinical outcomes when given early in treatment. Unfortunately, gut absorption causes an appreciable delay in the onset of effect, especially when morphine is used, and the constant push to minimize the door-to-balloon time has made it difficult to achieve adequate platelet inhibition at the time of percutaneous coronary intervention with an oral agent. An intravenous P2Y12 antagonist such as cangrelor may optimize treatment because it produces nearly maximal inhibition of platelet aggregation within minutes. If antiplatelet agents do protect through postconditioning's mechanism, then they would render any other intervention that protects through that mechanism redundant. Indeed, animals treated with cangrelor cannot be further protected by pre- or postconditioning. However, interventions that use a different mechanism such as mild hypothermia or cariporide, a Na(+)-H(+) exchange blocker, do add to cangrelor's protection. Future research should be directed toward identifying interventions that can augment the protection from antiplatelet therapy and finding a way to optimize P2Y12 inhibition at reperfusion in all patients.

Effect on Platelet Reactivity From a Prasugrel Loading Dose After a Clopidogrel Loading Dose Compared With a Prasugrel Loading Dose Alone

Background—

Adding a prasugrel loading dose (LD) to a clopidogrel LD could be desirable because clopidogrel may fail to provide adequate levels of platelet inhibition in patients with acute coronary syndrome undergoing percutaneous coronary intervention.

Methods and Results—

The pharmacodynamic response of prasugrel 60 mg LD alone was compared with prasugrel 60 mg or 30 mg added ≤24 hours to clopidogrel 600 mg in Transferring from Clopidogrel Loading Dose to Prasugrel Loading Dose in Acute Coronary Syndrome Patients study—a multicenter, randomized, double-blind, double-dummy, 3-arm, parallel, active-comparator controlled study. Two hundred eighty-two patients were randomized to 3 LD strategies: placebo plus prasugrel 60 mg, clopidogrel 600 mg plus prasugrel 60 mg, or clopidogrel 600 mg plus prasugrel 30 mg. Platelet function was assessed using VerifyNow P2Y12 Reaction Units (PRU) immediately before prasugrel LD, and 2, 6, 24, and 72 hours after prasugrel LD in 149 patients with evaluable platelet function studies. At 6 hours after the prasugrel 60 mg LD, the least squares mean (95% confidence interval) difference between placebo/prasugrel 60 mg and clopidogrel 600 mg/prasugrel 60 mg (primary outcome) was 22.2 (−11.0 to 55.5; P =0.19; least squares mean PRU 57.9 versus 35.6, respectively). For clopidogrel 600 mg/prasugrel 30 mg (least squares mean PRU, 53.9), the difference was 3.9 (−28.2 to 36.1; P =0.81) versus placebo/prasugrel 60 mg. No significant differences in PRU were observed at any time point across the 3 groups. There were few bleeding events observed regardless of treatment.

Conclusions—

Platelet reactivity with prasugrel 60 mg LD added to clopidogrel 600 mg LD was not significantly different compared with prasugrel 60 mg LD alone in acute coronary syndrome patients undergoing percutaneous coronary intervention.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01115738.

Assessing post-treatment platelet reactivity: a focus on patient selection and setting

Dual antiplatelet therapy is critical to inhibit platelet reactivity in order to prevent ischemic recurrences in stented patients. However, studies have observed a variable blockade of the P2Y12 adenosine diphosphate receptor between patients following clopidogrel intake. This interindividual variability in the biological response is not uncommon with clopidogrel (about 50%) and even prasugrel (20%). High on-treatment platelet reactivity (HTPR) is correlated with thrombotic events following percutaneous coronary intervention. Several studies suggested that tailoring of antiplatelet therapy based on platelet reactivity (PR) monitoring could safely reduce the rate of major adverse cardiovascular events in HTPR patients. In addition, low on-treatment PR was recently associated with bleeding events both in patients treated with prasugrel and clopidogrel. Of importance, bleedings are associated with a poor prognosis in stented patients. Overall, the potential of PR monitoring to individualize antiplatelet therapy might benefit stented patients by reducing both ischemic and bleeding risks. However, such strategies remain to be evaluated in adequately designed large-scale randomized clinical trials.

Clopidogrel pretreatment in primary percutaneous coronary intervention: prevalence of high on-treatment platelet reactivity and impact on preprocedural patency of the infarct-related artery

To date, there is limited data on levels of platelet inhibition achieved in patients with ST-elevation myocardial infarction (STEMI) who are loaded with clopidogrel and aspirin (ASA) prior to undergoing primary percutaneous coronary intervention (P-PCI). The aim of this investigation was to evaluate the percentage of STEMI patients with high on-treatment platelet reactivity (HPR) to clopidogrel at the time of initiating P-PCI and its association with the initial patency of the infarct-related artery (IRA). This prospective pharmacodynamic study included 50 STEMI patients, previously naïve to oral antiplatelet agents, who received 500-mg ASA and 600-mg clopidogrel loading doses prior to P-PCI. Platelet function assessment was performed at the beginning of the procedure using various assays, including VerifyNow™ system (primary endpoint), light transmission aggregometry and multiple electrode aggregometry. The percentage of patients with suboptimal response to clopidogrel and ASA assessed with the VerifyNow™ system was 88.0% and 28.6%, respectively. Similar results were obtained with the other assays used. A higher percentage of patients with initial patency of the IRA was observed among those patients without HPR compared with those with HPR to clopidogrel (66.7% vs 15.9%; p=0.013), while no differences were observed regarding postprocedural angiographic or electrocardiographic outcomes. In conclusion, this study shows that a high percentage of STEMI patients have inadequate levels of clopidogrel-induced and, to a lesser extent, aspirin-mediated platelet inhibition when starting a P-PCI procedure, and suggests that a poor response to clopidogrel might be associated with impaired initial TIMI flow in the IRA.