Christian Stratz

Cytochrome P450 2C19 681G>A Polymorphism and High On-Clopidogrel Platelet Reactivity Associated With Adverse 1-Year Clinical Outcome of Elective Percutaneous Coronary Intervention With Drug-Eluting or Bare-Metal Stents

OBJECTIVES We investigated whether the loss of function CYP2C19 681G>A *2 polymorphism is associated with high (>14%) residual platelet aggregation (RPA) on clopidogrel and whether high on-clopidogrel RPA impacts clinical outcome after elective coronary stent placement. BACKGROUND The cytochrome P450 (CYP)-dependent conversion of clopidogrel to its active metabolite may contribute to the variability in antiplatelet effect of clopidogrel. METHODS The study included 797 consecutive patients undergoing percutaneous coronary intervention, who were followed-up for 1 year. Adenosine-diphosphate-induced (5 mumol/l) RPA was assessed after a 600-mg loading dose and after the first 75-mg maintenance dose of clopidogrel before discharge. CYP2C19 genotype was analyzed by real-time polymerase chain reaction. RESULTS Of the patients included, 552 (69.3%) were CYP2C19 wild-type homozygotes (*1/*1) and 245 (30.7%) carried at least one *2 allele. Residual platelet aggregation at baseline did not differ significantly between genotypes. On clopidogrel, RPA was significantly (p < 0.001) higher in *2 carriers than in wild-type homozygotes (23.0% [interquartile range (IQR) 8.0% to 38.0%] vs. 11.0% [IQR 3.0% to 28.0%] after loading; 11.0% [IQR 5.0% to 22.0%] vs. 7.0% [IQR 3.0% to 14.0%] at pre-discharge). Between *2 carriers and wild-type homozygotes, we found significant (p < 0.001) differences in the proportion of patients with RPA >14%, both after loading (62.4% vs. 43.4%) and at pre-discharge (41.3% vs. 22.5%). Residual platelet aggregation >14% at pre-discharge incurred a 3.0-fold increase (95% confidence interval 1.4 to 6.8; p = 0.004) in the 1-year incidence of death and myocardial infarction. CONCLUSIONS Patients carrying at least one CYP2C19*2 allele are more prone to high-on clopidogrel platelet reactivity, which is associated with poor clinical outcome after coronary stent placement (Effect of Clopidogrel Loading and Risk of PCI [EXCELSIOR]; NCT00457236).

Impact of cytochrome P450 2C19 loss-of-function polymorphism and of major demographic characteristics on residual platelet function after loading and maintenance treatment with clopidogrel in patients undergoing elective coronary stent placement.

OBJECTIVES The aim of this study was to evaluate the relative impact of demographic and clinical variables versus the cytochrome P450 2C19 (CYP2C19) polymorphism on antiplatelet effects of clopidogrel. BACKGROUND Platelet responses to clopidogrel show a marked interindividual variability with substantial impact on clinical outcome. Several demographic and clinical characteristics as well as a polymorphism of CYP2C19 have been described as predictors for a low response to clopidogrel. METHODS This analysis enrolled 760 patients undergoing elective coronary stent implantation after loading with 600 mg of clopidogrel. Residual platelet aggregation was determined by optical aggregometry (adenosine diphosphate 5 micromol/l) before discharge. We analyzed the predictive value of the CYP2C19*2 polymorphism and baseline variables for an insufficient antiplatelet response by multivariable regression analysis and classification and regression trees analysis and determined the proportion responsible for the antiplatelet response of these predictors by multivariable linear regression analysis. RESULTS Major independent predictors for an insufficient antiplatelet response to clopidogrel were CYP2C19*2 carrier status (odds ratio [OR]: 2.74; 95% confidence interval [CI]: 1.93 to 3.90) together with age (OR: 1.03; 95% CI: 1.01 to 1.05), diabetes mellitus (OR: 1.75; 95% CI: 1.19 to 2.56), and body mass index (OR: 1.06; 95% CI: 1.02 to 1.11). The classification and regression trees analysis demonstrated that CYP2C19*2 carrier status followed by diabetes mellitus was the best discriminator between a sufficient and an insufficient antiplatelet response to clopidogrel. The full linear regression model including all these parameters could only explain 11.5% of the antiplatelet response (5.2% by CYP2C19*2 carrier status alone). CONCLUSIONS Thus, our study does not suggest that, in patients critically dependent on adequate platelet inhibition, genotyping alone or in combination with clinical factors can replace phenotyping of platelet function. (Effect of Clopidogrel Loading and Risk of PCI [EXCELSIOR]; NCT00457236).

The Serotoninergic Receptors of Human Dendritic Cells: Identification and Coupling to Cytokine Release

The neurotransmitter 5-hydroxytryptamine (5-HT), commonly known as serotonin, is stored at peripheral sites in mast cells and released from this peripheral source upon IgE cross-linking. In this study, we investigated the expression of serotoninergic receptors (5-HTR), the signaling pathway, and biological activity of 5-HT on human dendritic cells (DC), showing that immature and mature DC expressed mRNA for different serotoninergic receptors. Thereby, the mRNA of 5-HTR1B, 5-HTR1E, 5-HTR2A, 5-HTR2B, one splicing variant of the 5-HTR3, 5-HTR4, and 5-HTR7 receptors were detected. Immature DC preferentially expressed mRNA for the heptahelical 5-HTR1B, 5-HTR1E, and 5-HTR2B receptors, while mature DC mostly expressed 5-HTR4 and 5-HTR7. The mRNA expression level of the ligand-gated cation channel 5-HTR3 and the heptahelical 5-HTR2A did not significantly change during maturation. Isotype-selective receptor agonists allowed us to show that 5-HT stimulated 5-HTR3-dependent Ca2+ influx in immature and mature DC. Moreover, we revealed that 5-HTR1 and 5-HTR2 receptor stimulation induced intracellular Ca2+ mobilization via Gi/o proteins in immature, but not mature, DC. Activation of 5-HTR4 and 5-HTR7 induced cAMP elevation in mature DC. Functional studies indicated that activation of 5-HTR4 and 5-HTR7 enhanced the release of the cytokines IL-1β and IL-8, while reducing the secretion of IL-12 and TNF-α in mature DC. In summary, our study shows that 5-HT stimulated, in a maturation-dependent manner, different signaling pathways in DC. These data point to a role for 5-HT in regulating the immune response at peripheral sites.

Paraoxonase-1 Q192R polymorphism and antiplatelet effects of clopidogrel in patients undergoing elective coronary stent placement.

Background— Recently published data indicate that the paraoxonase-1 (PON1) Q192R genotype—and not as previously shown activity of cytochrome P450 (CYP) 2C19—is the major determinant of metabolic bioactivation of clopidogrel and thereby variability of antiplatelet effect of clopidogrel. We sought to investigate whether the PON1 Q192R gene polymorphism affects platelet reactivity in patients undergoing elective coronary stent placement. Methods and Results— The study included 760 consecutive patients undergoing elective coronary stent placement after loading with clopidogrel 600 mg. Platelet function was assessed by adenosine diphosphate-induced (ADP 5 and 20 &mgr;mol/L) platelet aggregation and by flow-cytometric analysis of platelet surface protein expression before clopidogrel, at the time of coronary stent placement, and before discharge after coronary stent placement. PON1 Q192R genotype [NM_000446.5:c.575A>G single nucleotide polymorphism (rs662)] was analyzed by TaqMan polymerase chain reaction. Residual platelet aggregation (ADP 5 &mgr;mol/L) at predischarge was 8.0% (3.0% to 17.0%) [median (interquartile range)] in PON1 QQ192 patients (n=384), 8.0% (3.0% to 15.0%) in PON1 QR192 (n=304), and 11.0% (3.0% to 18.0%) in PON1 RR192 (n=72; P=0.603). By multivariable linear regression, residual platelet aggregation was not associated with PON1 QQ192/QR192 (partial &eegr;2<0.001, P=0.728) but with CYP2C19*2 loss-of-function allele (partial &eegr;2=0.045, P<0.001) as well as any CYP2C19*17 gain-of-function allele (partial &eegr;2=0.012, P=0.004). All other platelet assays also showed no significant association between PON1 Q192R genotype and antiplatelet effect of clopidogrel. The 1-year incidence of death and myocardial infarction did not differ between PON1 Q192R genotypes. Conclusions— On-treatment platelet reactivity in patients undergoing coronary stent placement after loading with clopidogrel 600 mg was not associated with PON1 Q192R genotype. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00457236.

Cellular damage, platelet activation, and inflammatory response after pulmonary vein isolation: a randomized study comparing radiofrequency ablation with cryoablation.

BACKGROUND Experimental data suggest that use of cryoablation in pulmonary vein isolation (PVI) is associated with less cell damage and less thrombus formation compared to radiofrequency (RF) energy. OBJECTIVE The purpose of this study was to test the hypothesis that cryoablation significantly reduces markers of cell damage, platelet activation, and inflammation in patients undergoing PVI for treatment of atrial fibrillation (AF). METHODS Sixty patients with symptomatic drug-resistant AF (age 56 ± 9 years, 48 males, 38 with paroxysmal AF) were randomly assigned to undergo PVI using either an open irrigated-tip RF catheter or a cryoballoon. Markers of cell damage (high-sensitive troponin T [hs-TnT], microparticles), platelet activation (platelet reactivity by aggregometry, expression of platelet surface proteins P-selectin and activated glycoprotein [GP] IIb/IIIa), and inflammatory response (high-sensitive C-reactive protein [hs-CRP]) were determined before and up to 48 hours after the procedure. RESULTS PVI resulted in a significant rise in hs-TnT, microparticles, markers of platelet activation, and hs-CRP over time, with distinct temporal patterns for each parameter. However, after Bonferroni correction for repeated measurements, no significant differences were noted in these parameters between patients treated with cryoablation or RF energy. Procedural time was significantly shorter in patients treated with cryoballoon (177 ± 30 minutes vs 200 ± 46 minutes, P = .03), with no differences in fluoroscopic time, periprocedural complications, or success rate. CONCLUSION Cryoablation and RF energy result in a comparable rise of markers of cell damage, platelet activation and inflammatory response. The data do not support the concept of an improved safety profile for cryoablation in PVI.

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.

Impact of cytochrome P450 3A4-metabolized statins on the antiplatelet effect of a 600-mg loading dose clopidogrel and on clinical outcome in patients undergoing elective coronary stent placement

Early studies suggested interactions between statins and clopidogrel. Based on the outcome and platelet data, there is now huge evidence of no interactions between statins and 75 to 300 mg clopidogrel; however, data with 600-mg loading are lacking. In a pre-specified analysis of the EXCELSIOR cohort, we investigated the interaction between statins, especially cytochrome P4503A4-metabolized atorvastatin and simvastatin, and the antiplatelet effects of a 600-mg loading dose of clopidogrel. We analyzed 1,395 patients scheduled for coronary angiography (CA). Patients received clopidogrel 600 mg at least two hours before CA and 75 mg daily thereafter in case of percutaneous coronary intervention (PCI). Statin medication on admission was continued unaltered until discharge. Platelet function was assessed by optical aggregometry and flow cytometry of adenosine diphosphate (ADP)-stimulated surface expression of CD62P, CD63 and PAC-1 before clopidogrel and immediately before CA. Residual platelet aggregation (RPA) after addition of ADP 5 muM was similar irrespective of statin treatment at baseline (p = 0.968). RPA at CA was 46.2 +/- 16.8% in patients without statin (n = 682), 45.5 +/- 17.0% in patients with atorvastatin (n = 255), 45.8 +/- 16.3% with simvastatin (n = 335), 47.3 +/- 14.9% with fluvastatin (n = 42) and 45.9 +/- 16.2% with pravastatin (n = 81; p = 0.962). Consistent results were obtained by flow cytometry. In patients with PCI (n = 553), the one-year incidence of death, myocardial infarction and target lesion reintervention did not differ between cohorts stratified according to statin co-medication (p = 0.645). Thus, peri-interventional atorvastatin and simvastatin had no effect on the antiplatelet activity of a loading dose of clopidogrel 600 mg and did not affect clinical outcome after PCI.

Micro-array profiling exhibits remarkable intra-individual stability of human platelet micro-RNA

Platelets play an important role in haemostasis and thrombus formation. Latest research identified platelets harbouring so called microRNAs (miRNA). MiRNAs are short single-stranded RNAs modulating gene expression by targeting mRNAs. Limited data exist on inter-individual variability of platelet miRNA profile while no data are available on intra-individual variability. We assessed platelet miRNA profile in five volunteers at five time points over a time course of 10 days; 24 hours prior to the last blood sampling, subjects took 500 mg acetylsalicylic acid (ASA). Platelet miRNA was isolated from leucocyte-depleted platelet-rich plasma, and miRNA array-analysis was performed. Temporal patterns and ASA effect were explored by a linear mixed effects model for each miRNA. For the 20 most abundantly expressed platelet miRNAs, target gene search was performed and an annotation network was created. MiRNA expression profiling of 1,281 human miRNAs revealed relevant expression of 221 miRNAs consistently expressed in all samples at all time points. Correlation of platelet miRNA ranks was highly significant to other studies. Global distribution of miRNA expression was relatively similar in all subjects. No miRNA exhibited a significant effect of time at level 0.05. After 24 hours, no significant effect of ASA was found. Concerning functional implications of the 20 most abundantly expressed miRNAs, we found six functional themes. In conclusion, platelet miRNA profile is remarkably stable over the time period studied. Single-point analysis of platelet miRNA profile is reasonable when inter-individual differences are studied. The functional annotation network points toward extra-platelet effects of platelet miRNAs.

Antiplatelet response to the 150-mg maintenance dose of clopidogrel in patients with insufficient platelet inhibition after clopidogrel loading for elective coronary stent placement.

AIMS Our prospective study sought to investigate whether inadequate platelet responses to clopidogrel can be corrected by increasing the daily maintenance dose from 75 mg to 150 mg. METHODS AND RESULTS In 117 patients with elective PCI after loading with 600 mg clopidogrel, we determined residual platelet aggregation in response to 5 micromol/l ADP (RPA) by optical aggregometry after the first 75 mg maintenance dose (baseline), and at days 14 and 28. In patients with RPA >14% at baseline, we increased the daily dose to 150 mg. Fifty-seven additional patients without dose adjustment served as historic control. In 39 patients with baseline RPA >14%, the increase in maintenance dose to 150 mg reduced median RPA significantly (P<0.001) from 24% [interquartile range: 18-32%] at baseline to 14% [8-20%1 at 14 days without any further significant change. In patients with RPA < or = 14%, who continued on 75 mg clopidogrel, RPA increased during the first 14 days by 4.5% (0-14%; P<0.001). At 14 days, the study group with selective dose adjustment had a significantly lower RPA than the control group without dose adjustment (10.0% [4-20%1 versus 17.0% [9-32%], P<0.001). CONCLUSIONS In patients with a low initial response to clopidogrel, platelet inhibition can be improved by increasing the maintenance dose to 150 mg.

High-sensitivity cardiac troponin for risk prediction in patients with and without coronary heart disease☆ , ☆☆

BACKGROUND In stable patients with unknown coronary anatomy, higher levels of cardiac troponin are associated with an increased risk of cardiovascular events. It was supposed that this association might be explained by the ability of cardiac troponin to detect minor myocardial necrosis which might be caused by subclinical coronary atherosclerosis. Thus, this analysis tested if the predictive value of high-sensitivity troponin T (hsTnT) in stable patients is dependent of the presence or absence of angiographically documented coronary heart disease. METHODS Stable patients undergoing elective coronary angiography were enrolled (n=2046). HsTnT was determined before diagnostic procedures. The patients were followed for up to seven years. Primary endpoint was all-cause mortality or non-fatal myocardial infarction. All endpoints were adjudicated by independent physicians. Results were adjusted to a clinical model including independent clinical predictors of the primary endpoint. RESULTS Out of the 2046 patients enrolled, 1236 (60%) had a diagnosis of obstructive coronary heart disease. HsTnT predicted independently the primary endpoint (adjusted HR 1.33, 95%-CI 1.21-1.46, P<0.001). The use of hsTnT in addition to the clinical model significantly improved discrimination (c-statistic: 0.751 to 0.773, P<0.001) as well as reclassification of the primary endpoint (NRI=0.362, P<0.001). This significant improvement persisted across various subsets and was independent of the presence of clinically detectable coronary heart disease and other variables. CONCLUSION The use of hsTnT in addition to clinical variables significantly improves discrimination and reclassification of patients with respect to all-cause mortality or non-fatal myocardial infarction irrespective of the presence of clinically detectable coronary heart disease. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov (Identifier: NCT00457236).