Vasodilator-stimulated Phosphoprotein Index Research Articles

Impact of Platelet Reactivity in ACS Patients on Clinical Outcomes with Triple Antithrombotic Therapy.

Optimal antithrombotic therapy after percutaneous coronary intervention (PCI) in patients on oral anticoagulants (OAC) remains a clinical conundrum. In fact, combining an OAC with dual antiplatelet therapy (triple antithrombotic therapy, TAT) increases the risk of bleeding. Clopidogrel is the only thienopyridine recommended in TAT patients. Whether its response plays a relevant role in this setting remains uncertain. We aimed to evaluate the level of platelet reactivity inhibition (PRI) achieved by oral TAT in Acute Coronary Syndrome (ACS) patients undergoing PCI and its relationship with outcomes. We performed a multicenter prospective observational study and assessed PRI by vasodilator-stimulated phosphoprotein (VASP) index following a loading dose of clopidogrel. The primary endpoint was the incidence of major adverse cerebral or cardiovascular events (MACCE) at six months based on High on Treatment Platelet Reactivity (HTPR, VASP > 50%). The secondary endpoint was the incidence of bleeding at six months based on Low on Treatment Platelet Reactivity (LTPR, VASP < 16%). 491 patients were followed up for six months: 7.7% experienced MACCE and 17.3% experienced bleeding. There was no significant relationship between HTPR and MACCE, neither between LTPR and bleeding. Vitamin-K antagonist (VKA) treatment was associated with more MACCE and bleeding events, and the majority of events occurred within the first months. VASP index failed to predict outcomes in post-ACS patients with TAT. We confirm that direct acting OAC should be prioritized over VKA in TAT regimen.

On-Ticagrelor Platelet Reactivity and Clinical Outcome in Patients Undergoing Percutaneous Coronary Intervention for Acute Coronary Syndrome.

A strong association between on-thienopyridine platelet reactivity (PR) and the risk of both thrombotic and bleeding events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) has been demonstrated. However, no study has analyzed the relationship between on-ticagrelor PR and clinical outcome in this clinical setting. We aimed to investigate the relationship between on-ticagrelor PR, assessed by the vasodilator-stimulated phosphoprotein (VASP) index, and clinical outcome in patients with ACS undergoing PCI. We performed a prospective, multicenter, observational study of patients undergoing PCI for ACS. PR was measured using the VASP index following ticagrelor loading dose. The primary study endpoint was the rate of Bleeding Academic Research Consortium (BARC) type ≥2 at 1 year. The key secondary endpoint was the rate of major adverse cardiovascular events (MACE) defined as the composite of cardiovascular death, myocardial infarction, stroke, and urgent revascularization. We included 570 ACS patients, among whom 33.9% had ST-elevation myocardial infarction. BARC type ≥2 bleeding occurred in 10.9% and MACE in 13.8%. PR was not associated with BARC ≥2 or with MACE (p = 0.12 and p = 0.56, respectively). No relationship between PR and outcomes was observed, neither when PR was analyzed quantitatively nor when it was analyzed qualitatively (low on-treatment PR [LTPR] vs. no LTPR). On-ticagrelor PR measured by the VASP was not associated with bleeding or thrombotic events in ACS patients undergoing PCI. PR measured by the VASP should not be used as a surrogate endpoint in studies on ticagrelor.

Clopidogrel resistance in stroke patients (The CRISP Trial)

Objective: To investigate the incidence of clopidogrel resistance in patients with acute ischaemic stroke and to evaluate whether there is an association between clopidogrel resistance and the occurrence of a further cerebrovascular ischaemic event using the vasodilator-stimulated phosphoprotein (VASP) index as a marker of clopidogrel resistance. Methods: It is a prospective cohort study that recruited 120 patients from the acute stroke unit at the Royal Liverpool University Hospital. All patients with confirmed acute ischaemic stroke had clopidogrel 75mg/day at discharge or after 14 days of acute stroke if deemed by the direct clinical team to be the most appropriate treatment. After at least 7 days of clopidogrel 75mg/day, all those patients fulfilling inclusion/exclusion criteria had phosphorylation of vasodilator-stimulated phosphoprotein (VASP) measured. If VASP measured ≥50% after ≥7 days of clopidogrel maintenance, these patients were deemed as ‘clopidogrel resistant’, while those with VASP &lt;50% were deemed as ‘clopidogrel responder’. Statistical analysis was by univariable analysis which considered the association of each variable – diagnosis, age, duration of clopidogrel, VASP, days to VASP, and number of comorbidities – with the outcome. Risk of second stroke after a first at 6, 12 and 24 months was estimated using logistic regression. Results: No variables were significantly associated with risk of stroke at 6 months with clopidogrel resistance having no significant effect on likelihood of a further stroke compared to the no clopiodgrel resistance cohort (p value= 0.39). Results were similar at 12 months follow up. However, at 24 months VASP index was significantly associated with risk of a further stroke; each one unit increase in VASP was associated with a 3% increase in risk of stroke at 24 months (p value = 0.05, CI Interval of 1.00- 1.06). Conclusion: No variables were significantly associated with risk of further stroke at 6 months and 12 months after a first stroke. However, VASP was significantly associated with risk of further stroke at 24 months with increasing VASP leading to a higher risk of further stroke.

Prevalence and types of genetic polymorphisms of CYP2C19 and their effects on platelet aggregation inhibition by clopidogrel.

The current study was conducted to determine the distribution of genetic polymorphisms in CYP2C19 in Iraqi patients and their role in inter-individual variability of clopidogrel efficacy. A prospective controlled study was done on 100 patients under high risk of cardiovascular diseases who started clopidogrel prophylactic therapy. Polymerase chain reaction-restriction fragment length polymorphism method was used to determine the existence of the CYP2C19 gene mutation. Vasodilator-stimulated phosphoprotein (VASP) index baseline besides one-month post-therapy was analyzed by dual-color flow cytometry analysis. Eight gene mutations of CYP2C19 werefound(*1/*1), (*1/*2), (*1/*3), (*1/*8), (*1/*17), (*2/*2), (*2/*4), and (*3/*3) with higher prevalent CYP2C19*1 gene. Homozygous CYP2C19*1 allele was shown to be the rapid metabolizer comparing to the heterozygous CYP2C19*1 allele, whereas, CYP2C19*2 and CYP2C19*3 were resistant alleles and were present in 28% of patients. The analysis of VASP phosphorylation produces accurate inter-individual response variability in platelets inhibition by antiplatelet drugs. In vitro gene analysis and VASP index improve the clinical outcome of a patient candidate to clopidogrel as prophylaxisin cardiovascular events.

Clopidogrel resistance in stroke patients (The CRISP Trial)

Objective: To investigate the incidence of clopidogrel resistance in patients with acute ischaemic stroke and to evaluate whether there is an association between clopidogrel resistance and the occurrence of a further cerebrovascular ischaemic event using the vasodilator-stimulated phosphoprotein (VASP) index as a marker of clopidogrel resistance. Methods: It is a prospective cohort study that recruited 120 patients from the acute stroke unit at the Royal Liverpool University Hospital. All patients with confirmed acute ischaemic stroke had clopidogrel 75mg/day at discharge or after 14 days of acute stroke if deemed by the direct clinical team to be the most appropriate treatment. After at least 7 days of clopidogrel 75mg/day, all those patients fulfilling inclusion/exclusion criteria had phosphorylation of vasodilator-stimulated phosphoprotein (VASP) measured. If VASP measured ≥50% after ≥7 days of clopidogrel maintenance, these patients were deemed as ‘clopidogrel resistant’, while those with VASP &lt;50% were deemed as ‘clopidogrel responder’. Statistical analysis was by univariable analysis which considered the association of each variable – diagnosis, age, duration of clopidogrel, VASP, days to VASP, and number of comorbidities – with the outcome. Risk of second stroke after a first at 6, 12 and 24 months was estimated using logistic regression. Results: No variables were significantly associated with risk of stroke at 6 months with clopidogrel resistance having no significant effect on likelihood of a further stroke compared to the no clopiodgrel resistance cohort (p value= 0.39). Results were similar at 12 months follow up. However, at 24 months VASP index was significantly associated with risk of a further stroke; each one unit increase in VASP was associated with a 3% increase in risk of stroke at 24 months (p value = 0.05, CI Interval of 1.00- 1.06). Conclusion: No variables were significantly associated with risk of further stroke at 6 months and 12 months after a first stroke. However, VASP was significantly associated with risk of further stroke at 24 months with increasing VASP leading to a higher risk of further stroke.

Platelet reactivity inhibition following ticagrelor-loading dose in patients undergoing percutaneous coronary intervention for acute coronary syndrome

Ticagrelor induces more potent platelet reactivity (PR) inhibition with reduced interindividual variability compared to clopidogrel. Although on-clopidogrel PR was shown to correlate with ischemia and bleeding events, data regarding PR from ticagrelor and the outcomes are lacking. We aimed to determine the association between PR after a ticagrelor loading dose (LD), assessed by the vasodilator-stimulated phosphoprotein index (VASP), and thrombotic and bleeding events in patients with acute coronary syndrome (ACS) treated by percutaneous coronary intervention (PCI). We performed a prospective, multicenter observational study on patients treated with PCI for ACS. The VASP index was used to assess PR after ticagrelor LD. The primary endpoint was the link between major adverse cardiovascular events (MACE) and PR. Among the included 530 patients with ACS, 185 (34.5%) were admitted for ST elevation myocardial infarction. We observed high potency and limited interindividual variability after the ticagrelor LD (VASP 19.1 ± 16.6%). At 1 month, 21 (3.8%) MACE and 29 (5.5%) bleedings Academic Research Consortium ≥ 2 events were recorded. Neither MACE nor bleeding were associated with PR ( P = 0.34and p = 0.78 respectively). However, there was a strong association between PR and the occurrence of definite acute stent thrombosis ( P = 0.03). PR was the only factor associated with acute definite stent thrombosis. In patients receiving a ticagrelor LD while undergoing PCI for ACS, PR using the VASP does not predict MACE or bleeding, but it is significantly associated with the occurrence of definite acute ST.

Abstract TMP88: Cyp2c19 Polymorphisms Are Not Associated With the Long-term Clinical Outcomes in Stroke Patients Treated With Clopidogrel

Introduction: Active metabolite of clopidogrel blocks P2Y12 receptor and consequently reduces cardiovascular events (CVEs) in stroke patients. Since CYP2C19 is the major enzyme involved in the generation of active metabolite, several large-scale studies of the patients who mostly underwent percutaneous coronary intervention have indicated that the genotypes of CYP2C19 are associated with recurrent CVEs. However, reliable prospective data regarding this association in stroke patients are sparse. Methods: A multicenter, prospective cohort study of stable stroke patients receiving long-term clopidogrel therapy (for at least 28 days before enrollment) for the secondary prevention of CVEs was conducted at 14 hospitals in Japan. Between September 2010 and March 2012, 511 patients were enrolled and underwent CYP2C19 genotyping to identify loss-of-function polymorphisms (*2 and *3). On-treatment platelet reactivity was assessed by ADP-induced platelet aggregation and vasodilator-stimulated phosphoprotein (VASP) index. We followed all patients for 2 years to evaluate the association of CYP2C19 polymorphisms with the composite outcome including cardiac death, stroke, myocardial infarction and cerebral/carotid vascularization. Results: Median follow-up period was 728 days. Of 511 patients, 243 (48%) and 76 (15%) patients were classified as intermediate (IM:*1/*2 or *1/*3) and poor (PM:*2/*2, *2/*3, or *3/*3) metabolizers, respectively. The prevalence of IM/PM was substantially higher than that of studies on Caucasian populations. On-treatment platelet reactivity (mean±SD) assessed by ADP-induced platelet aggregation (52±18% in extensive metabolizer [EM:*1/*1], 60±16% in IM, and 69±71% in PM) or VASP index (43±15% in EM, 52±16% in IM, and 67±14% in PM) was significantly different among the groups (p&lt;0.0001). However, there was no significant difference in the incidence of the composite outcome among the groups (EM vs IM; hazard ratio [HR] 0.99 [95% CI 0.48—2.04], p=0.97, vs PM; HR 0.80 [0.26—2.51], p=0.70). Conclusions: Despite the significant association of CYP2C19 polymorphisms with on-treatment platelet reactivity, these parameters did not predict the recurrence of CVEs in stroke patients with long-term clopidogrel therapy.

Pharmacodynamic Effects During the Transition Between Cangrelor and Ticagrelor

This study sought to determine pharmacodynamic effects during transition from intravenous cangrelor to oral ticagrelor and from oral ticagrelor to intravenous cangrelor. Cangrelor is an intravenous antagonist of P2Y12 and its use will require transition to and from oral agents. Patients (n = 12) with stable coronary artery disease who were taking aspirin 81 mg daily were recruited. On study day 1, they received a bolus plus 2-h infusion of cangrelor plus a 180-mg dose of ticagrelor at either 0.5 h (n = 6) or 1.25 h (n = 6). Pharmacodynamic effects (light transmission platelet aggregation in response to 20 and 5 μmol/l adenosine diphosphate, VerifyNow, P2Y12 assay (Accumetrics, San Diego, California), vasodilator-stimulated phosphoprotein index, and flow cytometry) were assessed during and after the cangrelor infusion. Patients took 90 mg of ticagrelor twice daily for either 6 (n = 6) or 7 (n = 6) doses. On study day 5, pharmacodynamic effects were assessed before and during a bolus plus 2-h infusion of cangrelor. During cangrelor infusion, extensive inhibition of platelet function reflected by limited residual platelet reactivity was apparent. After cangrelor was stopped, the antiplatelet effects of ticagrelor were preserved despite a modest increase in platelet reactivity. Ticagrelor given before or during infusion of cangrelor did not attenuate the pharmacodynamic effects of cangrelor. The pharmacodynamic effects of ticagrelor were preserved when ticagrelor was given during infusion of cangrelor. Consistent with the reversible binding of ticagrelor, this oral P2Y12 antagonist can be administered before, during, or after treatment with cangrelor.

Abstract T P341: Impact Of Cytochrome P450 2C19 Polymorphism On High On-treatment Platelet Reactivity In Stroke Patients Treated With Clopidogrel

BACKGROUND: Clopidogrel is one of the most commonly used anti-platelet drugs. Recent reports suggested the association of allelic variants of the genes modulating metabolic activation (CYP2C19 and paraoxonase-1) and bioavailability (ABCB1) of clopidogrel with high on-treatment platelet reactivity (HTPR), possibly resulting in the recurrence of thrombotic events. However, these studies mostly examined patients with coronary heart disease and the impact of these polymorphisms in stroke patients is largely unknown. METHODS: We conducted a multicenter, prospective cohort study of 518 Japanese patients from 14 hospitals who were administrated clopidogrel. Residual platelet reactivity was determined by a change in light transmission induced by platelet aggregation in platelet-rich plasma after adding ADP. The vasodilator-stimulated phosphoprotein (VASP) index was also measured using flow cytometry. We investigated the association of polymorphisms of aforementioned enzymes with HTPR. RESULTS: In terms of CYP2C19 loss-of-function polymorphisms (*2 and *3), the prevalence of intermediate (IM: *1*2 or *1*3) or poor (PM: *2*2, *2*3, or *3*3) metabolizer was much higher (IM: 47% or PM: 15%) in Japanese than in Caucasian populations. Residual platelet reactivity was significantly higher in PM and IM groups than that in the wild-type extensive metabolizer (EM: *1*1) group assessed by 5 μM ADP-induced platelet aggregation (PM: 69.4% ± 17.1%, IM: 59.7% ± 16.2%, EM: 51.5% ± 17.5%, p &lt; 0.0001) and VASP index (PM: 66.6% ± 14.1%, IM: 52.4% ± 16.0%, EM: 42.9% ± 15.0%, p &lt; 0.0001). Furthermore, HTPR determined by both assays was associated with the ABCB1 polymorphism (rs1045642) but not with the paraoxonase-1 Q192R mutation. CONCLUSIONS: Our results indicate that both CYP2C19 and ABCB1 polymorphisms significantly contribute to HTPR in stroke patients treated with clopidogrel. At present, we are monitoring these patients for a two-year period to determine whether these genetic variants and HTPR affect the recurrence of thrombotic events.

Prasugrel Monitoring and Bleeding in Real World Patients

The aim of this study was to evaluate platelet reactivity and 30-day bleeding events in patients treated with prasugrel 10 mg after acute coronary syndromes. A total of 444 patients with acute coronary syndromes treated with percutaneous coronary intervention and prasugrel 10 mg/day were monitored by measurement of the vasodilator-stimulated phosphoprotein (VASP) index 2 to 4 weeks after hospital discharge. Platelet reactivity was also assessed using the VerifyNow P2Y(12) assay and light transmission aggregometry. Bleeding events (per the Bleeding Academic Research Consortium [BARC] definition) and ischemic events (death, myocardial infarction, and definite stent thrombosis) were collected over 30 days of follow-up. Two thirds of the patients presented with ST-segment elevation myocardial infarctions, 28.8% had diabetes, and 12.4% were aged >75 years. High on-treatment platelet reactivity according to 3 prespecified definitions (VASP index ≥ 50%, platelet reactivity ≥ 235 P2Y(12) reaction units, and residual platelet reactivity ≥ 46.2%) was found in 6.8%, 3.4%, and 3.2% of patients, respectively. Obesity (body mass index >30 kg/m(2)) and multivessel disease were the only independent factors associated with high on-treatment platelet reactivity (p = 0.006 and p = 0.045, respectively). At 30 days, there was no major bleeding complication (BARC grade 3 or 5), and 1.6% of patients had recurrent ischemic events. Nuisance bleeding (BARC grade 1) and minor bleeding (BARC grade 2) occurred in 14.2% (n = 63) and 2.5% (n = 11) of patients, respectively, but were not predicted by VASP index. In conclusion, patients with acute coronary syndromes receiving maintenance doses of prasugrel have low rates of HPR and ischemic events within the first month. Minor or minimal bleeding is frequent, but not major bleeding. VASP was poorly correlated with the risk for minor or minimal bleeding.

THE ASSOCIATION BETWEEN CYP2C19*2 GENE POLYMORPHISMS AND CLOPIDOGREL RESISTANCE IN THE HAN POPULATION OF NORTH CHINA WITH CORONARY ATHEROSCLEROTIC HEART DISEASE

ObjectivesDue to the diversification of platelet function test and defined criteria applied in previous studies, there is a big difference in the incidence of CR. Besides, it remains unclear of...

Relationship between post‐treatment platelet reactivity and ischemic and bleeding events at 1‐year follow‐up in patients receiving prasugrel

Post-treatment platelet reactivity (PR) is associated with ischemic and bleeding events in patients receiving P2Y12 receptor antagonists. We aimed to study the relationship between post-treatment PR after a 60-mg loading dose (LD) of prasugrel and 1-year thrombotic and bleeding events. Patients were prospectively included in this multicenter study if they had a successful percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) and received prasugrel. The platelet reactivity index (PRI) was measured using the Vasodilator-Stimulated Phosphoprotein index (VASP) after a prasugrel LD. Endpoints included the rate of thrombotic events and bleeding events at 1 year. Among the 301 patients enrolled, 9 (3%) were lost to follow-up at 1 year. The rates of thrombotic and bleeding events at 1 year were of 7.5% and 6.8%, respectively. Receiver-operating curve (ROC) analysis demonstrated an optimal cut-off value of 53.5% of PRI to predict thrombotic events at 1 year. Using this cut-off value we observed that patients exhibiting high on-treatment platelet reactivity (HTPR) had a higher rate of thrombotic events (22.4% vs. 2.9%; P < 0.001). In parallel the optimal cut-off value of PRI to predict bleeding was 16%. Patients with a PRI ≤ 16% had a higher rate of bleeding events compared with those with a PRI > 16% (15.6% vs. 3.3%; P < 0.001). In multivariate analysis, the PRI predicted both thrombotic and bleeding events (OR: 1.44, 95% confidence interval [CI]: 1.2-1.72; P < 0.001 and OR: 0.75, 95% CI: 0.59-0.96; P = 0.024 [respectively, per 10% increase]). Platelet reactivity measurement after a prasugrel LD predicts both ischemic and bleeding events at 1 year follow-up for ACS patients undergoing PCI.

Angiographic and platelet reactivity outcomes with prasugrel 60 mg pretreatment and clopidogrel 600 mg pretreatment in primary percutaneous coronary intervention

Pretreatment with 60mg of prasugrel is more effective than 300mg of clopidogrel in reducing thrombotic complications with primary percutaneous coronary intervention (PCI). We compared angiographic outcomes and platelet reactivity between treatment with 60mg of prasugrel and 600mg of clopidogrel administered before primary PCI. In this single centre non-randomized study, 65 consecutive Asian patients with ST-elevation myocardial infarction (STEMI) received 60mg of prasugrel before primary PCI. The pre- and post-PCI corrected thrombolysis in myocardial infarction frame count (CTFC) and the 8-h post-treatment platelet vasodilator-stimulated phosphoprotein (VASP) index was compared with a matched historical Asian STEMI cohort (n=65) receiving 600mg of clopidogrel pretreatment. Comparing the prasugrel and clopidogrel groups, the mean age was 54.1±10.2 versus 55.5±11.8years, P=0.238, and the mean body mass index was 24.6±2.0 versus 24.7±2.8kgm(-2), P=0.393. The mean pre-PCI CTFC was 82.1±30.2 versus 86.1±27.6, P=0.045, and the mean post-PCI CTFC was 21.1±13.9 versus 20.1±9.2, P=0.309. Pre-PCI coronary thrombi were visualised in 6.3 versus 18.1%, P=0.038. The median VASP index was 22.2±24.5 versus 70.5±17.5%, P<0.001, and high on-treatment platelet reactivity (VASP index>50%) was observed in 13.8 versus 84.3%, P=0.001. Rescue intracoronary glycoprotein inhibitors were administered to 29.7 versus 51.0%, P=0.018, respectively. Treatment with 60mg of prasugrel before primary PCI was associated with lower platelet reactivity, a modest trend towards better pre-PCI angiographic outcomes, less pre-PCI coronary thrombi and less rescue glycoprotein inhibitor use compared with 600mg of clopidogrel. The very high frequency of high on-clopidogrel platelet reactivity with 600mg of clopidogrel in this Asian STEMI cohort deserves further study.

Factors associated with the failure of clopidogrel dose-adjustment according to platelet reactivity monitoring to optimize P2Y12-ADP receptor blockade

IntroductionInter-individual variability in clopidogrel responsiveness is dependent on genetic polymorphisms. We aimed to investigate the impact of 3 genetic polymorphisms involved in clopidogrel metabolism on a strategy of dose-adjustment according to platelet reactivity (PR) monitoring. Materiel and methodsThis prospective multicenter study enrolled 498 ACS patients undergoing PCI. PR was measured using the Vasodilator-Stimulated Phosphoprotein index (VASP) and a cut-off value of ≥50% defined high on-treatment platelet reactivity (HTPR). Genetic polymorphisms of cytochrome (CYP) 2C19, Paraxonase-1 (PON1) and ABCB1 were determined by allele specific PCR. Dose-adjustment was performed using up-to 3 additional loading doses (LD) of 600mg clopidogrel in order to obtain a VASP <50% in patients with HTPR following the first LD. ResultsCYP 2C19 2*polymorphism (p=0.02), but neither PON1 (p=0.8) nor ABCB1 genotype (p=0.9), was significantly associated with HTPR. The dose-adjustment strategy failed in 11% of patients. ABCB1 polymorphism was significantly associated with a failed dose-adjustment (FDA) (p=0.04). No relation was found between the other genotypes and the efficacy of LD adjustment. In multivariate analysis, BMI and ABCB1 polymorphism were the only factors significantly associated with FDA (p=0.005 and p=0.04 respectively). ConclusionWhile CYP 2C19 2* is associated with HTPR after 600mg of clopidogrel, ABCB1 is responsible for the failure of a strategy of loading dose-adjustment according to PR monitoring. These findings may help to define a therapeutic strategy to optimize anti-platelet therapy in ACS patients undergoing PCI.

Renal Function Assessed Using Cystatin C and Antiplatelet Efficacy of Clopidogrel Assessed Using the Vasodilator-Stimulated Phosphoprotein Index in Patients Having Percutaneous Coronary Intervention

Renal dysfunction is a strong independent predictor of stent thrombosis. The aim of the present study was to evaluate the strength and direction of the association between kidney function and clopidogrel efficacy. The study group consisted of consecutive patients (n = 275) who underwent stent implantation. Drug efficacy was measured using the vasodilator-stimulated phosphoprotein (VASP) index 20 ± 4 hours after clopidogrel 600 mg. Nonresponse was defined as an VASP index ≥50%. Renal function was determined using serum cystatin C. The upper reference levels are 1.12 mg/L for ≤65 years of age and 1.21 mg/L for >65 years of age. Estimated glomerular filtration was calculated using cystatin C. The median value of cystatin C was 1.16 mg/L (twenty-fifth and seventy-fifth percentiles 0.96 and 1.43); 47.63% of the study population had cystatin C above reference levels and 33.1% of patients were nonresponders to clopidogrel. No correlation was found between clopidogrel efficacy assessed with the VASP index and kidney function assessed with cystatin C (Spearman r = -0.070, p = 0.248). Based on cystatin C the proportion of nonresponders to clopidogrel was 34.4% versus 31.9% (p = 0.702) in patients with impaired renal function compared to normal renal function, respectively. The proportion of clopidogrel nonresponders did not differ (p = 0.902) among groups with normal (28.8%), mildly impaired (34.8%), moderately impaired (32.9%), and severely impaired (34.8%) renal function. In conclusion, renal function assessed by cystatin C does not predict clopidogrel efficacy. Renal dysfunction is a complex entity and its significant relation to stent thrombosis cannot be explained simply by a decrease in clopidogrel efficacy.

A Comprehensive Analysis on the Agreement and Correlation of Consensual Cut-Offs of High on-Treatment Platelet Reactivity with the Vasodilator-Stimulated Phosphorylation Assay, the VerifyNow P2Y12 Analyzer and Light Transmittance Aggregometry

Abstract 2315 Background:Multiple lines of evidence have demonstrated a relationship between high on-treatment platelet reactivity (HPR) measured by multiple platelet assays and adverse clinical ischemic events. Although the Working Group on High On-Treatment Platelet Reactivity recently provided a consensus opinion on the definition of HPR, correlations between HPR cut-offs have not been validated yet. Therefore, we performed this study to provide a comprehensive analysis on the agreement and correlation of HPR cut-offs based on the consensual definition among the different platelet function measurements. Methods:We analyzed data from coronary intervention-treated patients on dual antiplatelet therapy (n = 962). Platelet measures were concurrently 5 and 20 μM ADP-stimulated light transmittance aggregometry (LTA), the VerifyNow P2Y12 analyzer, and flow cytometric analysis of vasodilator-stimulated phosphoprotein (VASP)-platelet reactivity index (PRI). As the Working Group noted, HPR cut-offs were defined as 5 and 20 μM ADP-induced maximal platelet aggregation (PRmax) > 46% and 59%, the VerifyNow P2Y12 assay > 240 P2Y12 reaction unit (PRU), and the VASP-PRI > 50%, respectively. Agreement between the consensual cut-off points of different tests was determined by kappa statistics, and 95% confidence intervals (CI) were also calculated. Receiver-operating characteristics (ROC) curve analysis was performed to identify the matched points for consensual definition-based cut-offs for HPR. Results:The consensual cut-off as 5μmol/l ADP-induced PRmax >46% showed a substantial agreement with 20 μmol/l ADP-induced PRmax, however, this cut-off showed a moderate agreement with the VerifyNow P2Y12 assay > 240 PRU and the VASP-PRI > 50%, respectively (Table 1). Fair correlations were observed between ADP-induced PRmax, the VerifyNow P2Y12 assay, and VASP-PRI according to the ROC curve analyses (Table 2). The cut-offs for 5μmol/l ADP-induced PRmax >46% based HPR matched well with the VerifyNow P2Y12 assay > 284 PRU (AUC 0.791, 95% CI 0.763–0.819, sensitivity 62.0%, and specificity 80.7%, p < 0.001), and the VASP-PRI > 60.3% (AUC 0.788, 95% CI 0.759–0.816, sensitivity 78.2%, and specificity 70.2%, p < 0.001) by the ROC curve analysis, respectively. The consensus-defined cut-offs of VerifyNow P2Y12 assay and VASP index overestimated HPR risk based on LTA cut-offs. [Display omitted] Conclusion:Although the VerifyNow P2Y12 and VASP assay correlated significantly with LTA, there are moderate agreements and fair correlations among the consensual cut-offs of HPR. These data suggest the platelet function measurements need to be improved to become clinically used diagnostic tests and the need for a new cut-offs to balance safety and efficacy of P2Y12 receptor antagonists. Further, it still may be too early to define the gold standard method for assessing platelet reactivity and generally acceptable cut-off values. Disclosures:No relevant conflicts of interest to declare.

Modified clopidogrel loading dose according to platelet reactivity monitoring in patients carrying ABCB1 variant alleles in patients with clopidogrel resistance

Objectives The aim of the present study was to investigate the impact of a adjusted clopidogrel loading dose (LD) according to platelet reactivity index in carriers of ABCB1 mutant allele undergoing percutaneous coronary intervention (PCI). Methods All patients met the inclusion criteria were recruited in the present study. Platelet reactivity was measured using the vasodilator-stimulated phosphoprotein (VASP) index. High treatment platelet reactivity (HTPR) was determined by a cut-off value of > 50%. The genetic polymorphism of ABCB1 was determined by allele-specific polymerase chain reaction (PCR). In patients carrying ABCB1 and HTPR after a first 300-mg LD of clopidogrel, dose adjustment was performed by using up to 3 additional 300-mg LDs to obtain a VASP index < 50%. The rate of major adverse cardiovascular events (MACE) and major or minor bleeding in one month were recorded. Results 536 patients were included in the present study. One hundred seventy-two patients (32%) carried ABCB1 mutant allele (11 homozygotes [2%] and 161 heterozygotes [30%]). The VASP index in these patients was significantly higher than in homozygotic patients for the wild allele (65.5 ± 13.8% vs. 47.6 ± 21.8%; p < 0.001). Of the 172 ABCB1 mutant allele carriers, 130 were considered to have HTPR. After a second clopidogrel LD, the VASP index was significantly decreased in these patients (66.9 ± 12.8% vs.50.2 ± 18.3%; < 0.001). Finally, dose adjustment according to platelet reactivity monitoring enabled 88% of ABCB1 mutant allele carriers and 91% of wild allele carriers exhibiting HTPR to reach a VASP index < 50%. The rate of MACE and major or minor bleeding in one-month follow-up between the wild allele carriers and the mutant allele carriers didn't differentiate significantly. Conclusions Increased and adjusted clopidogrel loading dose according to platelet reactivity monitoring attenuated clopidogrel resistance in carriers of ABCB1 mutant allele.

High On-Treatment Platelet Reactivity After Prasugrel Loading Dose and Cardiovascular Events After Percutaneous Coronary Intervention in Acute Coronary Syndromes

The aim of this study was to investigate the relationship between platelet reactivity (PR) after a loading dose (LD) of prasugrel and thrombotic events. Post-treatment PR has been shown to be strongly associated with the occurrence of major adverse cardiac events (MACE) after percutaneous coronary intervention (PCI) in the clopidogrel era. Prasugrel is a new P2Y(12)-adenosine diphosphate receptor with a higher potency on PR. A prospective multicenter study included patients who underwent successful PCI for acute coronary syndromes and received prasugrel therapy. Vasodilator-stimulated phosphoprotein (VASP) index was measured after the prasugrel LD. High on-treatment PR was defined as a VASP index ≥50%. MACE included cardiovascular death, myocardial infarction, and definite stent thrombosis at 1 month. Three hundred one patients were enrolled. The mean VASP index after 60 mg of prasugrel was 34.3 ± 23.1%. High on-treatment PR was observed in 76 patients (25.2%). Patients experiencing thrombotic events after PCI had significantly higher VASP indexes compared with those free of events (64.4 ± 14.4% vs. 33.4 ± 22.7%; range: 51% to 64% and 5% to 47.6%, respectively; p = 0.001). Kaplan-Meier analysis comparing good responders and patients with high on-treatment PR demonstrated a significantly higher rate of MACE in patients with suboptimal PR inhibition (log-rank p < 0.001). Receiver-operating characteristic curve analysis found a cutoff value of 53.5% of the VASP index to predict thrombotic events at 1 month (r = 0.86, p < 0.001). Patients with minor or major Thrombolysis In Myocardial Infarction unrelated to coronary artery bypass grafting bleeding and those without had similar VASP indexes (30 ± 17.8% vs. 34.3 ± 23%, p = 0.70). Despite the use of prasugrel, a significant number of patients undergoing PCI in the setting of acute coronary syndromes do not achieve optimal PR inhibition. Such patients have a higher risk for MACE after PCI.

Level of Adenosine Diphosphate Receptor P2Y12 Blockade During Percutaneous Coronary Intervention Predicts the Extent of Endothelial Injury, Assessed by Circulating Endothelial Cell Measurement

We aimed to investigate whether clopidogrel-induced inhibition of platelet reactivity could reduce the level of circulating endothelial cells (CEC), reflecting the endothelial injury induced by percutaneous coronary intervention (PCI). Clopidogrel loading dose before percutaneous coronary angioplasty (PCI) reduces platelet activation through a selective and irreversible blockade of the adenosine diphosphate (ADP) receptor P2Y(12). The impact of clopidogrel on endothelial cells has been scarcely studied. A total of 149 patients undergoing PCI for stable angina were enrolled. Levels of CEC were measured at baseline (H0) and 6 (H6) and 24 (H24) h after the procedure using a CD146-based immunomagnetic separation assay. The CEC delta-change (CEC at H6 - CEC at H0) was analyzed according to ADP receptor P2Y(12) blockade, assessed by a vasodilator-stimulated phosphoprotein (VASP) assay after a 600-mg loading dose of clopidogrel. The PCI induced a significant rise in CEC levels 6 h after the procedure. The CEC peak value was significantly higher in patients with high on-treatment platelet reactivity (VASP index ≥50%: 59.6 ± 27.5 cells/ml) as compared with good responders (VASP index <50%: 27 ± 22 cells/ml; p = 0.04). The endothelial injury, assessed by CEC delta-change between H6 and H0, was significantly higher in the high on-treatment platelet reactivity group compared with the good responders group (52.6 ± 25.6 vs. 18.6 ± 23.5, respectively; p < 0.001) and correlated with the VASP index (r = 0.59; p < 0.001). In multivariate analysis, VASP group, the number of diseased vessels, and the number of implanted stents independently predicted the endothelial injury (p < 0.001). Optimal ADP receptor P2Y(12) blockade reduces the endothelial injury during PCI. This protective effect of clopidogrel on endothelial cells could add to the clinical benefit associated with this drug.

Clopidogrel Loading Dose Adjustment According to Platelet Reactivity Monitoring in Patients Carrying the 2C19*2Loss of Function Polymorphism

We aimed to investigate the biological impact of a tailored clopidogrel loading dose (LD) according to platelet reactivity monitoring in carriers of the cytochrome (CYP) 2C19*2 loss-of-function polymorphism undergoing percutaneous coronary intervention for an acute coronary syndromes. CYP2C19*2 polymorphism is associated with reduced clopidogrel metabolism and a worse prognosis after percutaneous coronary intervention. A prospective multicenter study enrolling 411 patients with non-ST-segment elevation acute coronary syndrome undergoing percutaneous coronary intervention was performed. Platelet reactivity was measured using the vasodilator-stimulated phosphoprotein (VASP) index, and a cutoff value of ≥ 50% was used to define high on-treatment platelet reactivity (HTPR). The genetic polymorphism of CYP2C19 was determined by allele-specific polymerase chain reaction. In patients carrying CYP2C19*2 and exhibiting HTPR after a first 600-mg LD of clopidogrel, dose adjustment was performed by using up to 3 additional 600 mg LDs to obtain a VASP index <50%. One hundred thirty-four patients (35.3%) carried at least one 2C19*2 allele (11 homozygotes [2.7%] and 123 heterozygotes [32.6%]). The VASP index in these patients was significantly higher than in homozygotic patients for the wild-type alleles (61.7 ± 18.4% vs. 49.2 ± 24.2%; p < 0.001). Of the 134 carriers of the loss-of-function polymorphism, 103 were considered to have HTPR. After a second clopidogrel LD, the VASP index was significantly decreased in these patients (69.7 ± 10.1% vs. 50.6 ± 17.6%; p < 0.0001). Finally, dose adjustment according to platelet reactivity monitoring, enabled 88% of 2C19*2 carriers exhibiting HTPR to reach a VASP index <50%. Increased and tailored clopidogrel loading dose according to platelet reactivity monitoring overcome HTPR in carriers of the loss-of-function CYP2C19*2 polymorphism.