Late Platelet Aggregation Research Articles

Randomised comparison of adjunctive naoxintong versus standard maintenance dose clopidogrel in patients with CYP2C19*2 gene mutation

ObjectivesThe purpose of this study was to determine the impact of adjunctive Buchang Naoxintong Jiaonang (BNJ) in patients with CYP2C19*2 gene mutation undergoing percutaneous coronary intervention (PCI).BackgroundAlthough adjunctive BNJ to...

Justification of 150 mg clopidogrel in patients with high on‐clopidogrel platelet reactivity

The GRAVITAS trial showed that 150 mg clopidogrel did not improve outcome in patients with high on-clopidogrel platelet reactivity (HPR) screened by the VerifyNow assay. We aimed to determine the impact of 150 mg clopidogrel in stable angina patients with HPR identified with conventional aggregometry (LTA). Clopidogrel-naive stable angina patients before ad hoc percutaneous coronary intervention were recruited into a randomized, double-blind, placebo-controlled trial (NCT00638326). Twelve to 24 h after the 600-mg loading dose of clopidogrel, ADP(5μM)-stimulated maximal (AGGmax), late platelet aggregation (AGGlate) and vasodilator-stimulated phosphoprotein phosphorylation (VASP-PRI) were evaluated. Patients with HPR (AGGmax ≥ 34%) were randomly allocated to 75 or 150 mg clopidogrel after 4 weeks. After control platelet function measurements at day 28, 75 mg clopidogrel was administered to all patients until 1 year. The study was prematurely terminated at the stage of 200 enroled patients. Administration of 150 mg clopidogrel significantly reduced platelet aggregation (AGGmax: 45·0 ± 6·8 vs. 33·8 ± 15·1, P < 0·01; AGGlate: 27·1 ± 14·7 vs. 13·8 ± 18·0, P < 0·01) and VASP-PRI (57·5 ± 15·2 vs. 37·2 ± 17·1; P < 0·01), while platelet reactivity remained unchanged in patients with HPR receiving 75 mg clopidogrel. The higher maintenance dose of clopidogrel was associated with a significant reduction in cardiovascular (CV) death and myocardial infarction (MI) (0% vs. 11·4%, P = 0·04) and in CV death, MI or target vessel revascularization (24·6% vs. 3·1%; P = 0·01) during 1 year. One-month administration of 150 mg maintenance dose of clopidogrel reduces platelet reactivity and might decrease the risk of thrombo-ischaemic complications in stable angina patients with HPR identified by LTA.

Platelet Inhibition by Adjunctive Cilostazol Versus High Maintenance-Dose Clopidogrel in Patients With Acute Myocardial Infarction According to Cytochrome P450 2C19 Genotype

The aim of this study was to assess the degree of platelet inhibition by adjunctive cilostazol in patients with acute myocardial infarction (AMI) according to hepatic cytochrome P450 2C19 (CYP2C19) genotype. Although adjunctive cilostazol intensifies platelet inhibition in AMI patients, it is not established whether this regimen can be free from the effect of CYP2C19 loss-of-function variants (*2/*3). We randomly assigned 126 AMI patients with available CYP2C19 genotyping to receive adjunctive cilostazol (triple group; n = 64) or high maintenance-dose (MD) clopidogrel of 150 mg/day (high-MD group; n = 62). Using conventional aggregometry and VerifyNow (Accumetrics Inc., San Diego, California), platelet reactivity was measured at pre-discharge and 30-day follow-up. Primary endpoint was change in maximal platelet aggregation (ΔAgg(max)) between pre-discharge and 30-day follow-up. High on-treatment platelet reactivity (HPR) was defined as 20 μmol/l adenosine diphosphate-induced maximal platelet aggregation (Agg(max)) >59%. In noncarriers, despite numerically greater inhibition by adjunctive cilostazol, changes in platelet measures and the rate of HPR did not significantly differ between the 2 groups. In carriers, ΔAgg(max) after 5 and 20 μmol/l adenosine diphosphate stimuli was significantly higher in the triple (n = 39) versus high-MD group (n = 38) (21.8 ± 13.9% vs. 9.0 ± 13.3%, p < 0.001, and 24.2 ± 17.2% vs. 7.7 ± 15.5%, p < 0.001, respectively). Likewise, changes in late platelet aggregation and P2Y12 reaction unit were consistently greater in the triple versus high-MD group. Fewer patients in the triple group met the criteria of HPR at 30-day follow-up than in the high-MD group (15.4% vs. 44.7%, p = 0.005). Compared with high-MD clopidogrel, adjunctive cilostazol significantly enhances platelet inhibition and reduces the rate of HPR, especially in AMI patients with CYP2C19 loss-of-function variants. (Adjunctive Cilostazol Versus High Maintenance-Dose Clopidogrel in Acute Myocardial Infarction (AMI) Patients According to CYP2C19 Polymorphism [ACCELAMI2C19]; NCT00915733).

Platelet Inhibition by Adjunctive Cilostazol Versus High Maintenance-Dose Clopidogrel In Patients with Acute Myocardial Infarction According to Cytochrome P450 2C19 Genotype

AbstractAbstract 3322 ObjectivesThe aim of this study was to assess the degree of platelet inhibition by adjunctive cilostazol in patients with acute myocardial infarction (AMI) according to CYP2C19 genotype. BackgroundAlthough adjunctive cilostazol intensifies platelet inhibition in AMI patients, it is not established whether this regimen can overcome the loss-of-function effect of CYP2C19 variants. MethodsWe randomly assigned 126 AMI patients with available CYP2C19 genotyping to receive adjunctive cilostazol (triple group; n = 64) or high maintenance-dose (MD) clopidogrel of 150-mg/day (high-MD group; n = 62). Using conventional aggregometry and VerifyNow, platelet reactivity was measured at pre-discharge and 30-day follow-up. Primary endpoint was change in maximal platelet aggregation (Aggmax). High post-treatment platelet reactivity (HPPR) was defined as 5 μmol/l ADP-induced Aggmax > 50%. ResultsIn non-carriers, the two groups did not differ with respect to changes in platelet measures, and could achieve fewer rates of HPPR at 30-day follow-up (< 5%). In carriers, changes in 5 and 20 μmol/l ADP-induced Aggmax were significantly higher in the triple (n = 39) versus high-MD group (n = 38) (21.8 ± 13.9% vs. 9.0 ± 13.3%, p < 0.001, and 24.2 ± 17.2% vs. 7.7 ± 15.5%, p < 0.001, respectively). Likewise, changes in late platelet aggregation and P2Y12 reaction unit were consistently greater in the triple vs. high-MD group. Fewer patients in the triple group met the criteria of HPPR at 30-day follow-up compared with the high-MD group (2.6% vs. 21.1%, p = 0.014). ConclusionsAmong AMI patients with CYP2C19 variants, adjunctive cilostazol enhances platelet inhibition and reduces the rate of HPPR, as compared with high-MD clopidogrel. (Adjunctive Cilostazol Versus High-MD ClopidogrEL in Patients With Acute Myocardial Infarction According to CYP2C19 genotype [ACCEL-AMI-CYP2C19]; NCT00915733). Disclosures:No relevant conflicts of interest to declare.

Cytochrome 2C19 Polymorphism and Response to Adjunctive Cilostazol Versus High Maintenance-Dose Clopidogrel in Patients Undergoing Percutaneous Coronary Intervention

Among patients treated with clopidogrel, carriers of the cytochrome P450 (CYP) 2C19 loss-of-function allele have shown increased platelet reactivity and higher rates of ischemic events. Although adjunctive cilostazol to dual antiplatelet therapy (or "triple antiplatelet therapy") intensifies platelet inhibition, it remains unknown whether triple antiplatelet therapy after percutaneous coronary intervention can achieve adequate platelet inhibition in patients with the CYP2C19 mutant allele. CYP2C19 genotyping for *1, *2, and *3 was performed in 134 high-risk patients undergoing elective percutaneous coronary intervention. After measurement of preprocedural platelet reactivity, patients were randomly assigned to receive either adjunctive cilostazol 100 mg twice daily (triple group; n=69) or high maintenance-dose (MD) clopidogrel of 150 mg daily (high-MD group; n=65). Using light transmittance aggregometry and the VerifyNow P2Y(12) assay, platelet reactivity was assessed before the index procedure and at 30-day follow-up. The primary end point was absolute change in maximal platelet aggregation (ΔAgg(max)) according to CYP2C19 genotyping. High posttreatment platelet reactivity was defined as 5 μmol/L ADP-induced maximal platelet aggregation >50%. In noncarriers of the CYP2C19*2/*3 mutant allele, ΔAgg(max) values after 5 and 20 μmol/L ADP stimuli did not differ significantly between the triple (n=22) versus the high-MD group (n=22) (23.6±21.6% versus 16.6±15.4%, P=0.224 and 26.4±22.2% versus 18.6±14.9%, P=0.174, respectively). Absolute changes in late platelet aggregation and P2Y(12) reaction unit were not different between the groups. The rate of high posttreatment platelet reactivity at 30-day follow-up also was comparable between the triple versus the high-MD group (4.5% versus 13.6%, P=0.607). In carriers of at least 1 CYP2C19*2/*3 mutant allele, the triple group (n=47) showed greater values of ΔAgg(max) after addition of 5 μmol/L (25.8±16.8% versus 11.1±19.8%, P<0.001) and 20 μmol/L ADP (26.3±16.0% versus 11.5±16.3%, P<0.001) compared with the high-MD group (n=43). Likewise, absolute changes in late platelet aggregation and P2Y(12) reaction unit were consistently greater in the triple versus the high-MD group. Fewer patients in the triple group met the criteria of high posttreatment platelet reactivity at 30-day follow-up compared with the high-MD group (6.4% versus 37.2%, P<0.001). Among high-risk patients undergoing elective percutaneous coronary intervention, adjunctive cilostazol can achieve consistently intensified platelet inhibition and reduce the risk of high posttreatment platelet reactivity irrespective of CYP2C19 genotyping. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01012193.

Comparison of conventional aggregomerty with VASP for monitoring P2Y12-specifc platelet inhibition

No consensus exists regarding the optimal estimate of light transmission aggregometry (LTA) to reflect P2Y12 ADP receptor inhibition in patients receiving thienopyridine therapy. Currently, the only completely P2Y12-receptor specific method is the measurement of vasodilator stimulated phosphoprotein (VASP) phosphorylation (PRI) with flow cytometry. In the current analysis, we aimed to test the superiority of the late platelet aggregation value over other estimates of light transmission aggregometry in determining P2Y12-receptor inhibition by comparing them to VASP-PRI. On-clopidogrel platelet reactivity was measured in 121 clopidogrel-naïve patients who underwent elective coronary stent implantation. Samples for LTA and VASP assessments were drawn at 12–18 hours after a 600-mg loading dose of clopidogrel and 25 days after the intervention. ADP 5 µM-induced maximal aggregation (AGGmax), 6-minute late aggregation (AGGlate), 6-minute disaggregation (disAGG) and area under the aggregation curve (AUC) were compared to VASP-PRI. Categorical agreement with VASP-defined normal and high platelet reactivity (HPR: PRI≥50%) was calculated according to the optimal cutoff values obtained with receiver-operating characteristic (ROC) curves. The evaluation of 242 measurements showed significant, moderate-strength correlations between VASP-PRI and LTA estimates without the superiority of AGGlate over other estimates (AGGmax: ρ = 0.47; AGGlate: ρ = 0.45; disAGG: ρ = −0.44; AUC: ρ = 0.50). Notably, there were considerable intra-individual differences between VASP and LTA testing. LTA estimates were similar in classifying patients to VASP-defined normal or HPR categories (AGGmax: κ = 0.41; AGGlate: κ = 0.45; disAGG: κ = 0.44; AUC: κ = 0.44). When all estimates of LTA were compared in multivariable models, AUC proved to be the independent linear determinant of VASP-PRI and the best predictor of HPR. Estimates of LTA seem equal in determining the degree of P2Y12-receptor inhibition or in predicting VASP-defined HPR without the superiority of AGGlate over others. These results reject a commonly used hypothesis and might contribute to the standardization of the LTA assay.

The Impact of Generic Clopidogrel Bisulfate on Platelet Inhibition in Patients with Coronary Artery Stents: Results of the ACCEL-GENERIC Study

Background/AimsIn patients with coronary artery stents, the cost of clopidogrel has been cited as a factor in the premature discontinuation of therapy. Thus, the introduction of lower-cost generic clopidogrel may increase patient compliance. However, platelet inhibition by generic clopidogrel has not been compared to the original clopidogrel formulation in patients with coronary artery stents.MethodsWe prospectively enrolled 20 patients receiving chronic therapy with the original clopidogrel bisulfate (Plavix®). After assessing patient compliance with Plavix®, maintenance therapy was switched to generic clopidogrel bisulfate (Plavitor®). Platelet reactivity was assessed at baseline and 30-day after the switch using conventional aggregometry and the VerifyNow P2Y12 assay.ResultsAll patients completed maintenance therapy with Plavitor®. Before and after switching therapy maximal (36.5 ± 7.9% vs. 39.8 ± 16.2%, p = 0.280) and late platelet aggregation (23.5 ± 10.9% vs. 29.1 ± 18.3%, p = 0.156) with 5 µmol/L adenosine diphosphate (ADP) stimulus did not differ. Likewise, 20 µmol/L ADP-induced platelet aggregation and P2Y12 reaction unit in patients on Plavitor® therapy was comparable to that in patients on Plavix® therapy. However, Bland-Altman analysis showed wide limits of agreement between measured platelet reactivity on Plavix® vs. Plavitor® therapies.ConclusionsAmong patients on Plavix® maintenance therapy with coronary stents, replacement with Plavitor® shows a comparable inhibition of ADP-induced platelet aggregation. However, due to poor inter-therapy agreement, between two regimens, physicians may be cautious when introducing generic clopidogrel bisulfate.

Randomized Comparison of Adjunctive Cilostazol Versus High Maintenance Dose Clopidogrel in Patients With High Post-Treatment Platelet Reactivity: Results of the ACCEL-RESISTANCE (Adjunctive Cilostazol Versus High Maintenance Dose Clopidogrel in Patients With Clopidogrel Resistance) Randomized Study

The purpose of this study was to determine the impact of adjunctive cilostazol in patients with high post-treatment platelet reactivity (HPPR) undergoing coronary stenting. Although addition of cilostazol to dual antiplatelet therapy enhances adenosine diphosphate (ADP)-induced platelet inhibition, it is unknown whether adjunctive cilostazol can reduce HPPR. Sixty patients with HPPR after a 300-mg loading dose of clopidogrel were enrolled. HPPR was defined as maximal platelet aggregation (Agg(max)) >50% with 5 micromol/l ADP. Patients were randomly assigned to receive either adjunctive cilostazol (triple group; n = 30) or high maintenance dose (MD) clopidogrel (high-MD group; n = 30). Platelet function was assessed at baseline and after 30 days with conventional aggregometry and the VerifyNow assay. Baseline platelet function measurements were similar in both groups. After 30 days, significantly fewer patients in the triple versus high-MD group had HPPR (3.3% vs. 26.7%, p = 0.012). Percent inhibitions of 5 micromol/l ADP-induced Agg(max) and late platelet aggregation (Agg(late)) were significantly greater in the triple versus high-MD group (51.1 +/- 22.5% vs. 28.0 +/- 18.5%, p < 0.001, and 70.9 +/- 27.3% vs. 45.3 +/- 23.4%, p < 0.001, respectively). Percent inhibitions of 20 micromol/l ADP-induced Agg(max) and Agg(late) were consistently greater in the triple versus high-MD group. Percent change of P2Y12 reaction units demonstrated a higher antiplatelet effect in the triple versus high-MD group (39.6 +/- 24.1% vs. 23.1 +/- 29.9%, p = 0.022). Adjunctive cilostazol reduces the rate of HPPR and intensifies platelet inhibition as compared with a high-MD clopidogrel of 150 mg/day.

Abstract 2014: Additive Cilostazol to Dual Antiplatelet Therapy Achieves Greater Inhibition of Platelet Aggregation Compared With High Maintenance-Dose Clopidogrel in Patients With Acute Myocardial Infarction

Objectives The aim of study was to compare platelet inhibition by additive cilostazol to dual antiplatelet therapy (triple antiplatelet therapy) and high maintenance-dose (MD) clopidogrel 150mg/d in patients with acute myocardial infarction (AMI). Methods AMI patients undergoing successful stenting (n =90) were randomly assigned to 1 of 3 MD regimens: Standard group, clopidogrel 75 mg/d; High MD group, clopidogrel 150 mg/d; Triple group, additive cilostazol 100 mg twice daily. Platelet functions were evaluated before discharge and 30 days after discharge. Percent inhibition (PI) and a rate of poor responder to clopidogrel were assessed, based on maximal and late platelet aggregation (Agg max and Agg late ). Results Baseline platelet measures were similar in 3 groups. There was more potent and consistent PI by Triple group in all platelet measures. PI of 5 uM ADP-induced Agg max was 3.5% in Standard group, 22.6% in High MD group, and 44.1% in Triple group (p &lt; 0.001). In addition, PI of 5 uM ADP-induced Agg late was 12.3%, 31.5%, and 65.0% in each group, respectively (p &lt; 0.001). Similar results were demonstrated when 20 uM ADP and 6 ug/ml collagen were used. In terms of poor response to clopidogrel (5 and 20 uM ADP-induced Agg max &gt; 50%), fewer patients in triple group (4.3% and 23.3%) met a criteria than those in standard group (23.3% and 73.3%) and high MD group (16.7% and 60.0%) at 30 days (p = 0.028 and &lt; 0.001, respectively). All parameter between Triple and High MD groups were significantly different. Conclusions Triple antiplatelet therapy achieves greater platelet inhibition and lesser rate of poor response to clopidogrel compared with high MD clopidogrel in AMI patients.

Clopidogrel 600-Mg Double Loading Dose Achieves Stronger Platelet Inhibition Than Conventional Regimens: Results From the PREPAIR Randomized Study

The objective of this study was to compare the level of platelet inhibition achieved by 3 different clopidogrel loading regimens in patients undergoing elective angiography and percutaneous coronary intervention when appropriate. Optimal platelet inhibition is a key therapeutic goal for patients undergoing percutaneous coronary intervention. Although 600 mg has been described as the maximum absorbed dose when given as a single bolus, the effects of 2 boluses given 24 h apart have not been described. Patients (n = 148) were randomly assigned to one of 3 regimens: Group A, clopidogrel 300 mg the day before (>or=15 h) + 75 mg the morning of the procedure; Group B, clopidogrel 600 mg the morning of the procedure (>or=2 h); and Group C, clopidogrel 600 mg the day before (>or=15 h) and 600 mg the morning of the procedure (>or=2 h). Blood samples were obtained at baseline and immediately before angiography. Peak and late platelet aggregation were measured in platelet rich plasma, with researchers blinded to treatment allocation. There was a consistent difference favoring Group C in all aggregation parameters. Percent inhibition in Groups A, B, and C was 31.4%, 29.0%, and 49.5%, respectively, for peak aggregation (5 micromol/l adenosine diphosphate; p < 0.0001) and 54.1%, 57.7%, and 81.1%, respectively, for late aggregation (p < 0.0001). Similar striking reductions were observed when 20 micromol/l adenosine diphosphate was used. All comparisons between Group C and the other 2 groups were statistically significant, and those between Groups A and B were not. Clopidogrel 600-mg double bolus achieves greater platelet inhibition than conventional single loading doses.

Randomized Comparison of a High Clopidogrel Maintenance Dose in Patients With Diabetes Mellitus and Coronary Artery Disease

After treatment with clopidogrel, patients with type 2 diabetes mellitus (T2DM) have reduced platelet inhibition compared with patients who are not diabetic. Whether platelet inhibition can be enhanced by increasing clopidogrel maintenance dosage in T2DM patients is unknown. The aim of this pilot study was to assess the functional impact of a high maintenance dose in T2DM patients with suboptimal clopidogrel-induced antiplatelet effects. T2DM patients on chronic dual antiplatelet therapy were screened to identify suboptimal clopidogrel responders. The latter were randomized to 30-day treatment with a standard (75 mg; n=20) or high (150 mg; n=20) daily maintenance dose. Platelet function was assessed at 3 time points: baseline, 30 days after randomization, and 30 days after resuming standard dosing. Platelet function parameters included adenosine diphosphate-induced (20 and 5 micromol/L) maximal and late platelet aggregation, inhibition of platelet aggregation, platelet disaggregation, and P2Y12 reactivity index. A total of 64 T2DM patients were screened to identify 40 suboptimal responders. After randomization, maximal adenosine diphosphate-induced (20 micromol/L) platelet aggregation was significantly reduced in the 150-mg group compared with the 75-mg group (P=0.002; primary end point). However, suboptimal clopidogrel response was still present in 60% of patients on the 150-mg regimen. All other platelet function parameters showed enhanced clopidogrel-induced antiplatelet effects with 150 mg, which returned to baseline values after resumption of standard dosing. A 150-mg maintenance dose of clopidogrel is associated with enhanced antiplatelet effects compared with 75 mg in high-risk T2DM patients. However, enhanced ex vivo platelet reactivity continues to persist, the clinical implications of which are unknown and need to be evaluated in large-scale clinical trials.