Anna Maria Gori

Cardiovascular Death and Nonfatal Myocardial Infarction in Acute Coronary Syndrome Patients Receiving Coronary Stenting Are Predicted by Residual Platelet Reactivity to ADP Detected by a Point-of-Care Assay A 12-Month Follow-Up

Background— The clinical impact of platelet aggregation assessed by point-of-care assays is unknown. We sought to evaluate whether high residual platelet reactivity (RPR) to ADP during clopidogrel therapy, measured by a point-of-care assay, predicts adverse clinical events in acute coronary syndrome patients undergoing percutaneous coronary intervention. Methods and Results— We used the VerifyNow P2Y12 assay (Accumetrics Inc, San Diego, Calif) to determine RPR to ADP in 683 patients with acute coronary syndrome undergoing dual-antiplatelet therapy who underwent percutaneous coronary intervention with bare-metal or drug-eluting stent implantation. All patients received a single 600-mg clopidogrel loading dose followed by 75 mg of clopidogrel daily and 100 to 325 mg of aspirin daily. The end points of the study at follow-up of 12 months were cardiovascular death, nonfatal myocardial infarction (MI), and target-vessel revascularization. At a 12-month follow-up, we found 51 ischemic events (24 cardiovascular deaths [3.5%], 27 nonfatal MIs [3.9%]) and 40 target-vessel revascularizations (5.8%). By receiver operating characteristic curve (ROC) analysis, the optimal cutoff value in predicting 12-month cardiovascular death and nonfatal MI was P2Y12 reaction unit values ≥240. RPR, defined in the presence of P2Y12 reaction unit values above this cutoff, was found to be a significant and independent predictor of cardiovascular death and nonfatal MI in a model that adjusted for cardiovascular risk factors, renal failure, reduced left ventricular ejection fraction, multivessel disease, total stent length, bifurcation lesions, number of lesions treated, type of stent, and use of glycoprotein IIb/IIIa inhibitors (cardiovascular death: hazard ratio 2.55, 95% CI 1.08 to 6.07, P=0.034; nonfatal MI: hazard ratio 3.36, 95% CI 1.49 to 7.58, P=0.004). No significant association was found between high RPR and the risk of target-vessel revascularization. Conclusions— RPR to ADP with clopidogrel therapy, measured by the point-of-care assay VerifyNow P2Y12, is able to detect acute coronary syndrome patients at risk of 12-month cardiovascular death and nonfatal MI. The optimal cutoff value was identified as being 240 P2Y12 reaction units.

High Residual Platelet Reactivity After Clopidogrel Loading and Long-term Cardiovascular Events Among Patients With Acute Coronary Syndromes Undergoing PCI

CONTEXT High residual platelet reactivity (HRPR) in patients receiving clopidogrel has been associated with high risk of ischemic events after percutaneous coronary intervention (PCI). OBJECTIVE To test the hypothesis that HRPR after clopidogrel loading is an independent prognostic marker of risk of long-term thrombotic events in patients with acute coronary syndromes (ACS) undergoing an invasive procedure and antithrombotic treatment adjusted according to the results of platelet function tests. DESIGN, SETTING, AND PATIENTS Prospective, observational, referral center cohort study of 1789 consecutive patients with ACS undergoing PCI from April 2005 to April 2009 at the Division of Cardiology of Careggi Hospital, Florence, Italy, in whom platelet reactivity was prospectively assessed by light transmittance aggregometry. INTERVENTIONS All patients received 325 mg of aspirin and a loading dose of 600 mg of clopidogrel followed by a maintenance dosage of 325 mg/d of aspirin and 75 mg/d of clopidogrel for at least 6 months. Patients with HRPR as assessed by adenosine diphosphate test (≥70% platelet aggregation) received an increased dose of clopidogrel (150-300 mg/d) or switched to ticlopidine (500-1000 mg/d) under adenosine diphosphate test guidance. MAIN OUTCOME MEASURES The primary end point was a composite of cardiac death, myocardial infarction, any urgent coronary revascularization, and stroke at 2-year follow-up. Secondary end points were stent thrombosis and each component of the primary end point. RESULTS The primary end point event rate was 14.6% (36/247) in patients with HRPR and 8.7% (132/1525) in patients with low residual platelet reactivity (absolute risk increase, 5.9%; 95% CI, 1.6%-11.1%; P = .003). Stent thrombosis was higher in the HRPR group compared with the low residual platelet reactivity group (6.1% [15/247] vs 2.9% [44/1525]; absolute risk increase, 3.2%; 95% CI, 0.4%-6.7%; P = .01). By multivariable analysis, HRPR was independently associated with the primary end point (hazard ratio, 1.49; 95% CI, 1.08-2.05; P = .02) and with cardiac mortality (hazard ratio, 1.81; 95% CI, 1.18-2.76; P = .006). CONCLUSION Among patients receiving platelet reactivity-guided antithrombotic medication after PCI, HRPR status was significantly associated with increased risk of ischemic events at short- and long-term follow-up. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01231035.

Cytochrome P450 2C19 loss-of-function polymorphism, but not CYP3A4 IVS10 + 12G/A and P2Y12 T744C polymorphisms, is associated with response variability to dual antiplatelet treatment in high-risk vascular patients.

Objectives The aim of this study was to evaluate the effect of polymorphisms affecting the clopidogrel metabolism (CYP3A4 IVS10+12G/A and CYP2C19*2) and the P2Y12 receptor (P2Y12 T744C) on modulating platelet function in acute coronary syndrome patients on dual antiplatelet treatment. Background Residual platelet reactivity (RPR) phenomenon on antiplatelet therapy requires clarification. P2Y12 T744C, CYP3A4 IVS10+12G/A and, in healthy individuals only, CYP2C19*2 polymorphisms have been investigated; however, the influence on platelet reactivity in a large population of high-risk vascular patients on dual antiplatelet treatment has not yet been elucidated. Methods A total of 1419 acute coronary syndrome patients on dual antiplatelet treatment were studied. Platelet function was evaluated by platelet-rich plasma aggregation. Electronic nanochips and restriction-fragment length polymorphism were used for analysis of polymorphisms. Results Only CYP2C19*2, out of the three investigated polymorphisms, is associated with higher platelet reactivity. Carriers of the *2 allele had significantly higher platelet aggregation values after arachidonic acid (AA; P=0.043), 2 μmol/l adenosine 5′ diphosphate (ADP; P<0.0001) and 10 μmol/l ADP (P=0.001) stimuli. The genotype distribution of CYP2C19*2 polymorphism significantly differed between patients with and without RPR, as evaluated by 10-μmol/l ADP-induced platelet aggregation (P=0.002) and by AA-induced platelet aggregation (P=0.045). At the multivariate linear regression analysis, the CYP2C19*2 polymorphism remained a significant and independent risk factor for dual antiplatelet treatment variability. Conclusions This study demonstrates, for the first time, that the *2 CYP2C19 allele is associated with higher platelet aggregability and RPR in high-risk vascular patients on dual antiplatelet treatment. These findings can have a significant impact on the future design of pharmacogenetic antiaggregant strategies for high-risk vascular patients on dual antiplatelet treatment.

Transient intermittent lymphocyte activation is responsible for the instability of angina.

BackgroundBlood clotting activation is an important component of the inflammatory response; the outbursts of unstable angina are usually associated with increased thrombin formation and coronary mural thrombosis. Methods and ResultsTo investigate 1) whether monocyte activation is responsible for the enhanced thrombin formation during bursts of unstable angina and 2) what mechanism(s) might be responsible for monocyte activation, we studied patients with unstable angina (n=31), stable effort angina (n=23), left endoventricular thrombosis (n=8), and control subjects (n=44), measuring plasma fibrinopeptide A (FPA) levels and the capacity of monocytes to express procoagulant activity (PCA) and of lymphocytes to modulate this expression. Patients with unstable angina and patients with endoventricular thrombosis had significantly (p<0.0001) higher FPA plasma levels than patients with effort angina and control subjects. However, only monocytes from unstable angina patients expressed significantly increased PCA characterized as tissue factor-like activity (units/105 monocytes, median and range; 120, 1.1–463.2 versus 10.8, 0.8–39.1 in control subjects; p<0.0001 versus the other groups). When 14 patients with unstable angina were restudied 8–12 weeks later, they showed neither elevated plasma FPA levels nor monocyte PCA. In unstable angina patients, there was a correlation between FPA and PCA (r=0.56, p<0.001). For expression of PCA by monocytes, both an incubation of at least 2 hours with lymphocytes and direct monocyte-lymphocyte contact were needed. In reconstitution and cross-mixing experiments, only lymphocytes from patients with active unstable angina induced the expression ofPCA by monocytes from both control and patient groups. ConclusionsThe results demonstrate that the increased thrombin formation in unstable angina patients is due to the expression of tissue factor-like activity by activated monocytes. The monocyte activation appears to be a part of a lymphocytic cell-instructed response intermittently triggered by unknown factors.

Acute T-cell activation is detectable in unstable angina.

BACKGROUND Recent studies suggest a role for inflammation in the pathophysiology of unstable angina. This study was designed to investigate whether circulating lymphocytes are involved in the inflammatory reaction associated with the episodes of unstable angina. METHODS AND RESULTS Twenty-nine patients with proven unstable angina, 36 with stable angina, and 30 healthy subjects were studied. Both early and short-lived (interleukin-2 receptor [IL-2R], alpha-chain CD25, and transferrin receptor CD71) and late antigen (HLA-DR) expression were investigated by flow cytometric analysis. Soluble IL-2R (sIL-2R) was also measured in plasma by ELISA. Lymphocyte activation was studied at day 1 of hospital admission and after 7, 15, 30, 60, and 90 days. In patients with unstable angina, the number of HLA-DR+ CD3 lymphocytes and levels of sIL-2R were higher (P < .001) than in patients with stable angina and control subjects. Both CD4+ and CD8+ lymphocytes expressed HLA-DR antigens. No differences were found among the different groups of subjects in regard to the expression of CD25 and CD71. Lymphocyte activation was more marked in patients with urgent revascularization. No relationships were found between the number of HLA-DR+ lymphocytes and either the severity of coronary angiographic lesions or the number of ischemic episodes. Observations over time showed a gradual decrease in the number of HLA-DR+ lymphocytes and sIL-2R levels from weeks 3 through 8 to 12. CONCLUSIONS The present results indicate that (1) CD4+ and CD8+ circulating lymphocytes are activated in patients with unstable angina, and their activation state lasts 6 to 8 weeks; and (2) activation of lymphocytes is not a consequence of myocardial ischemia. These results support the immune system-mediated inflammatory nature of unstable angina.

Clopidogrel non-responsiveness and risk of cardiovascular morbidity: an updated meta-analysis

We performed this meta-analysis to update the clinical evidences on the relation between clopidogrel non-responsiveness and clinical outcomes in patients with coronary artery disease (CAD) who underwent percutaneous coronary intervention. An electronic literature search through MEDLINE, EMBASE, Web of Science, and the Cochrane Library and bibliographies of retrieved articles up to January, 2009 was conducted. Studies were included if they had a cohort prospective design, if they analysed clopidogrel responsiveness in CAD patients in relation to death and/or occurrence of adverse coronary events during follow-up, and if they reported an adequate statistical analysis. Fourteen studies, totalling 4,564 CAD patients followed for a time ranging from 14 days to one year, were included. The cumulative analysis reported that residual platelet reactivity despite clopidogrel treatment was significantly associated with an increased risk of death and/or thrombotic recurrences (odds ratio [OR] 5.67, 95% confidence interval [CI] 2.97 to 10.84; p<0.00001). However, four studies contributed to a consistent heterogeneity of the model and evidenced a significant risk of publication bias, so were excluded from the analysis. This exclusion, however, did not influence the overall result, by confirming the increased risk of cardiovascular recurrences for patients with a poor response to clopidogrel treatment (OR 3.58, 95%CI 2.54 to 5.05; p<0.00001). The present updated meta-analysis documents a significant association between residual platelet reactivity under clopidogrel treatment and recurrent cardiovascular events, so suggesting the relevance of ongoing interventional studies aimed at tailoring the antithrombotic therapy in CAD patients.

Genome-wide Association Study of Vitamin B6, Vitamin B12, Folate, and Homocysteine Blood Concentrations

The B vitamins are components of one-carbon metabolism (OCM) that contribute to DNA synthesis and methylation. Homocysteine, a by-product of OCM, has been associated with coronary heart disease, stroke and neurological disease. To investigate genetic factors that affect circulating vitamin B6, vitamin B12, folate and homocysteine, a genome-wide association analysis was conducted in the InCHIANTI (N = 1175), SardiNIA (N = 1115), and BLSA (N = 640) studies. The top loci were replicated in an independent sample of 687 participants in the Progetto Nutrizione study. Polymorphisms in the ALPL gene (rs4654748, p = 8.30 x 10(-18)) were associated with vitamin B6 and FUT2 (rs602662, [corrected] p = 2.83 x 10(-20)) with vitamin B12 serum levels. The association of MTHFR, a gene consistently associated with homocysteine, was confirmed in this meta-analysis. The ALPL gene likely influences the catabolism of vitamin B6 while FUT2 interferes with absorption of vitamin B12. These findings highlight mechanisms that affect vitamin B6, vitamin B12 and homocysteine serum levels.

Different methodologies for evaluating the effect of clopidogrel on platelet function in high-risk coronary artery disease patients.

Summary.  Background: Two point‐of‐care (POC) systems have been recently proposed as rapid tools with which to evaluate residual platelet reactivity (RPR) in coronary artery disease (CAD) patients. Objectives and Methods: We compared Platelet Function Analyzer‐100 (PFA‐100) closure times (CTs) by collagen/adenosine 5´‐diphosphate (ADP) (C/ADP CT) cartridge and the VerifyNow P2Y12 Assay (VerifyNow) with light transmission aggregation (LTA) induced by 2 and 10 μmol L–1 ADP in 1267 CAD patients on dual antiplatelet therapy who underwent percutaneous coronary intervention. We also performed the vasodilator‐stimulated phosphoprotein (VASP) phosphorylation assay by cytofluorimetric analysis in a subgroup of 115 patients. Results: Cut‐off values for identifying RPR were: ≥ 54% and ≥ 66% for LTA induced by 2 and 10 μmol L–1 ADP respectively, and ≥ 264 P2Y12 Reaction Units (PRU) for VerifyNow. The cut‐off for PFA‐100 C/ADP CT was ≥ 68 s. RPR was detected in 25.1% of patients by 2 μmol L–1 ADP‐induced LTA (ADP‐LTA), in 23.2% by 10 μmol L–1 ADP‐LTA, in 24.4% by PFA‐100, and in 24.7% by VerifyNow. PFA‐100 results did not parallel those obtained with LTA. VerifyNow showed a significant correlation (ρ = 0.62, P < 0.001) and significant agreement (k = 0.34, P < 0.001) with LTA induced by 2 μmol L–1 ADP. The correlation was similar but the agreement was better between VerifyNow and 10 μmol L–1 ADP‐LTA (ρ =  0.64, P < 0.0001; k = 0.43, P < 0.001). Significant relationships were found between VASP platelet reactivity index and both ADP‐LTA and VerifyNow. PFA‐100 C/ADP CT did not significantly correlate with any of the other assays. Conclusions: Our results show a significant correlation between LTA and VerifyNow but not the PFA‐100 C/ADP assay. Clinical validation studies for POC systems are necessary.

Cytochrome P450 2C19 * 2 polymorphism and cardiovascular recurrences in patients taking clopidogrel: a meta-analysis

Several polymorphisms in genes that encode platelet components (receptors or enzymes), or cytochrome P450 enzyme isoforms, involved in clopidogrel metabolism, have been proposed as possible mechanisms for nonresponsiveness to clopidogrel. Among them, a great deal of attention has been focused on the loss-of-function CYP2C19*2 (or 681 G>A) polymorphism. We performed a meta-analysis of all the prospective studies that have been published, which analyze the role of such a polymorphism in recurrent cardiovascular events in patients with coronary artery disease (CAD) being treated with clopidogrel. Studies were searched in MedLine, Embase, Web of Science, The Cochrane Systematic Review Database, Google Scholar and bibliographies of retrieved articles up to January 2010. The principal underlying hypothesis was that the presence of the *2 variant allele of the polymorphism would be associated with an increased risk of clinical recurrence. Data were available for a total of 8043 patients from seven cohort prospective studies, who were followed for a period of time ranging from 6 months to 8.3 years. The summary risk ratios (RRs) for the prospective cohort studies included showed a significant association between the CYP2C19*2 polymorphism and an increased risk of major adverse cardiovascular events in the follow-up (RR: 1.96 (1.14–3.37); P=0.02). When studies evaluating stent thrombosis (n=4) for a total of 4975 patients were considered, the presence of the variant allele was associated with an increased risk of stent thrombosis (RR: 3.82 (2.23–6.54); P=0.0001). The current meta-analysis, carried out on nearly 8000 patients with CAD undergoing clopidogrel treatment, shows that the CYP2C19*2 polymorphism is associated with an increased risk of major adverse cardiovascular events and stent thrombosis.

Relationship between high platelet turnover and platelet function in high-risk patients with coronary artery disease on dual antiplatelet therapy

A high platelet turnover rate produce a population of immature reticulated platelets (RP) that could confer, despite of antiplatelet drugs, a residual platelet reactivity (RPR) in coronary artery disease (CAD) patients. To assess the influence of RP on platelet reactivity in CAD patients on dual antiplatelet therapy we measured RP in 372 patients by using the Sysmex XE-2100 haematology analyzer and platelet function by optical platelet aggregometry (PA) on platelet-rich-plasma induced by 1 mmol arachidonic acid (AA-PA) and 10 microM ADP (ADP-PA). RPR was defined as either AA-PA>20% or ADP-PA>70%. RP were expressed as a percentage of RP of the total optical platelet count (immature platelet fraction; IPF) and as the percentage of RP highly fluorescent (highly fluorescent immature platelet fraction; H-IPF). Moderate but significant positive correlations between PA, IPF, H-IPF, and mean platelet volume (MPV) were found. According to tertiles of IPF, H-IPF and MPV, a significant trend for an increase of platelet aggregation by AA and ADP was evidenced. Furthermore, a significant difference for IPF, H-IPF and MPV between patients with and without RPR was observed. A linear regression analysis showed that IPF, H-IPF and MPV significantly affected PA measured by AA and ADP. At multivariate linear regression analysis these associations were confirmed. Moreover, a logistic regression analysis demonstrated that IPF, H-IPF and MPV significantly influenced the risk of RPR, and in the multivariate model these results remained significant. This study indicates that a high rate of platelet turnover is a new mechanism associated with platelet reactivity in high risk CAD patients on dual antiplatelet therapy.