Rita Paniccia

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.

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.

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.

Cardiac Growth Factors in Human Hypertrophy Relations With Myocardial Contractility and Wall Stress

The aim of the present study was to investigate whether and which cardiac growth factors are involved in human hypertrophy, whether growth factor synthesis is influenced by overload type and/or by the adequacy of the hypertrophy, and the relationships between cardiac growth factor formation and ventricular function. Cardiac growth factor formation was assessed by measuring aorta-coronary sinus concentration gradient in patients with isolated aortic stenosis (n=26) or regurgitation (n=15) and controls (n=12). Gene expression and cellular localization was investigated in ventricular biopsies using reverse transcriptase-polymerase chain reaction and in situ hybridization. Cardiac hypertrophy with end-systolic wall stress <90 kdyne/cm2 was associated with a selective increased formation of insulin-like growth factor (IGF)-I in aortic regurgitation and of IGF-I and endothelin (ET)-1 in aortic stenosis. mRNA levels for IGF-I and preproET-1 were elevated and mainly expressed in cardiomyocytes. At stepwise analysis, IGF-I formation was correlated to the mean velocity of circumferential fiber shortening (r=0.86, P<0.001) and ET-1 formation to relative wall thickness (r=0.82, P<0. 001). When end-systolic wall stress was >90 kdyne/cm2, IGF-I and ET-1 synthesis by cardiomyocytes was no longer detectable, and only angiotensin (Ang) II was generated, regardless of the type of overload. The mRNA level for angiotensinogen was high, and the mRNA was exclusively expressed in the interstitial cells. Ang II formation was positively correlated to end-systolic stress (r=0.89, P<0.001) and end-diastolic stress (r=0.84, P<0.001). Multivariate stepwise analysis selected end-systolic stress as the most predictive variable and left ventricular end-diastolic pressure as the independent variable for Ang II formation (r=0.93, P<0.001). In conclusion, the present results indicate that the course of human left ventricular hypertrophy is characterized by the participation of different cardiac growth factors that are selectively related both to the type of hemodynamic overload and to ventricular function.

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.

Platelet function tests: a comparative review

In physiological hemostasis a prompt recruitment of platelets on the vessel damage prevents the bleeding by the rapid formation of a platelet plug. Qualitative and/or quantitative platelet defects promote bleeding, whereas the high residual reactivity of platelets in patients on antiplatelet therapies moves forward thromboembolic complications. The biochemical mechanisms of the different phases of platelet activation – adhesion, shape change, release reaction, and aggregation – have been well delineated, whereas their complete translation into laboratory assays has not been so fulfilled. Laboratory tests of platelet function, such as bleeding time, light transmission platelet aggregation, lumiaggregometry, impedance aggregometry on whole blood, and platelet activation investigated by flow cytometry, are traditionally utilized for diagnosing hemostatic disorders and managing patients with platelet and hemostatic defects, but their use is still limited to specialized laboratories. To date, a point-of-care testing (POCT) dedicated to platelet function, using pertinent devices much simpler to use, has now become available (ie, PFA-100, VerifyNow System, Multiplate Electrode Aggregometry [MEA]). POCT includes new methodologies which may be used in critical clinical settings and also in general laboratories because they are rapid and easy to use, employing whole blood without the necessity of sample processing. Actually, these different platelet methodologies for the evaluation of inherited and acquired bleeding disorders and/or for monitoring antiplatelet therapies are spreading and the study of platelet function is strengthening. In this review, well-tried and innovative platelet function tests and their methodological features and clinical applications are considered.

Assessment of platelet function on whole blood by multiple electrode aggregometry in high-risk patients with coronary artery disease receiving antiplatelet therapy.

This study sought to compare Multiplate impedance platelet aggregometry (IPA) with light transmission aggregometry (LTA) and the PFA-100 for determining the prevalence of residual platelet reactivity (RPR) by the Multiplate IPA in 297 patients with acute coronary syndrome receiving dual antiplatelet therapy. Aggregations were induced by adenosine-5 diphosphate (ADP), arachidonic acid, and collagen. PFA-100 closure times were measured by collagen and ADP and epinephrine (CEPI) cartridges. Significant correlations were observed between Multiplate IPA and LTA after all stimulations (P < .0001) and between Multiplate IPA (arachidonate and collagen) and PFA-100 CEPI closure time (P < .0001 for both). Cutoff values of Multiplate IPA (for all stimulations) were calculated for the identification of RPR. Between the Multiplate IPA and LTA good agreement was found with all 3 agonists (P < .0001 for all). Multiplate IPA might represent a reliable, handy, rapid tool to monitor antiplatelet therapy in clinical practice and for clinical investigations.

Selective Upregulation of Cardiac Endothelin System in Patients With Ischemic but Not Idiopathic Dilated Cardiomyopathy: Endothelin-1 System in the Human Failing Heart

Only scarce information is available on the activity and modifications of the cardiac endothelin (ET)-1 system in heart failure due to ischemic (ICM) or idiopathic dilated (DCM) cardiomyopathy. The activity of the ET-1 system was investigated by measuring cardiac ET-1 and big ET-1 formation and quantifying cardiac mRNA for prepro-ET-1 (ppET-1), ET-converting enzyme-1, and ET(A) and ET(B) receptors both in myocardium and in isolated myocytes using Northern blot, reverse transcription-polymerase chain reaction, and in situ hybridization in 22 patients with DCM and 20 with ICM who underwent cardiac transplantation and in 7 potential heart transplant donors (nonfailing hearts). Notwithstanding a similar increase of plasma ET-1 in the 2 groups, cardiac ET formation, mRNA levels for ppET-1, and ET(A) and ET(B) receptors were higher on both the myocardium and isolated myocytes from ICM than on those from DCM hearts (P<0.001 for all). ppET-1 and ET-converting enzyme-1 mRNAs were expressed on myocytes and endothelial and interstitial cells in ICM, whereas in DCM and nonfailing hearts they were mainly expressed on nonmyocyte cells. In both ICM and DCM, the ET(A) mRNA signal was expressed on both myocytes and nonmyocyte cells, whereas ET(B) mRNA was almost exclusively localized on nonmyocyte cells. ET(A)- and ET(B)-specific receptor binding was increased on both myocytes and cardiac membranes, showing a positive correlation with left ventricular ejection fraction in ICM (r=0.78 and 0.70) but not in DCM patients. The present results show that human ventricular myocytes express all of the components of the ET-1 system, which is selectively upregulated in ICM patients and appears to be functionally important in the maintenance of cardiac function.

Effect of Medium-term Supplementation with a Moderate Dose of n-3 Polyunsaturated Fatty Acids on Blood Pressure in Mild Hypertensive Patients

Several studies have shown that n-3 polyunsaturated fatty acids (n-3 PUFA) are able to lower blood pressure (BP) in humans, but large doses of fish oils have been often used. Moreover, most of the studies available in the literature were not able to evaluate the specific effects of n-3 PUFA because they employed fish oils which contain, together with n-3 PUFA, many other different components. The aim of this preliminary study was to evaluate if medium-term supplementation with a moderate dose of highly purified eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) ethyl esters is able to reduce BP in mild hypertensive patients. Sixteen mild essential hypertensive (diastolic BP: 95-104 mm Hg), non-diabetic, normolipidemic male outpatients and 16 normotensive male controls were recruited to participate in the study. Both hypertensive and control subjects were randomly assigned to receive either EPA and DHA ethyl esters (2.04 g EPA and 1.4 g DHA) as active treatment or olive oil (4 g/day) as a placebo for a period of 4 months. These subjects were followed up with 24-hour ambulatory BP monitoring and blood chemistry analyses at 2 and 4 months of treatment and 2 months after its discontinuation. The intake of n-3 PUFA was checked by red blood cell (RBC) phosphatidylcholine (PC) fatty acid composition. The effect of n-3 PUFA on BP in the active group was maximum after 2 months. Both systolic (-6 mm Hg, p<0.05) and diastolic (-5 mm Hg, p<0.05) BP significantly decreased during the n-3 PUFA ethyl ester supplementation. No further effect was observed at 4 months with a return to baseline values during the recovery period. These data indicate that 4 g/day of highly purified EPA + DHA ethyl esters are able to favorably affect BP in mild hypertensives.

Evaluation of Clotting and Fibrinolytic Activation after Protracted Physical Exercise

The behavior of hemostatic system activation during protracted physical exercise is well known, but the duration of its modification is not yet defined. In order to evaluate the time of hemostatic system activation after prolonged strenuous endurance physical exercise (typical marathon race: 42.195 km, v=15.35 km/h; mean length of time run 2.45+/-0.15 hours) 12 well-trained long-distance male runners (mean age: 35+/-7, range 25-47 years) were investigated. Blood samples were drawn in the morning on the day before the performance, immediately after the race, and 24 hours and 48 hours after the end of run. With respect of baseline, immediately after the race, a significant decrease of fibrinogen (-25%) and significant increases of prothrombin fragment 1+2 (+633%) and thrombin-antithrombin complex (+848%) were observed. A significant acceleration of euglobulin lysis time (-41%), and rises of plasma levels of tissue plasminogen activator antigen (+361%), plasminogen activator inhibitor type 1 antigen (+235%), d-dimer (+215%), and plasma fibrinogen degradation products (+1200%) were also found. Only a slight, yet not significant, decrease in plasminogen activator inhibitor type 1 activity was observed. One day after the end of marathon different parameters were still unchanged. Forty-eight hours after the competition all parameters investigated returned to baseline values. These results indicate a persistence of clotting as well as fibrinolysis activation up to 24 hours after the end of the race.