Analysis of individualized antiplatelet therapy for patients of acute coronary syndrome after percutaneous coronary intervention under the guidance of platelet function: A one-center retrospective cohort study.

ABSTRACT: There is controversy in clinical application of antiplatelet drugs by monitoring platelet function. Therefore, we explored whether early and dynamic medication could bring better clinical outcomes for patients under the guidance of platelet function tests (PFT).In this retrospective cohort study, we analyzed the prognostic events of 1550 patients with acute coronary syndrome (ACS) at Tianjin People's Hospital in China. They received dual antiplatelet therapy (DAPT) after percutaneous coronary intervention (PCI) from January 2017 to December 2018. The primary endpoint was based on the Bleeding Academic Research Consortium (BARC) 3 or 5 major bleeding. Secondary endpoints included MACCE (all-cause death, nonfatal myocardial infarction, stroke, stent thrombosis, and unplanned target vessel reconstruction) and BARC 1 to 2 minor bleeding. The endpoint events within 1 year after PCI were recorded. Patients were divided into a guided group and a control group according to the drug adjustment by PFT results. After the propensity scores matched, the end points of 2 groups were compared, and subgroup analysis was performed on major bleeding events.After propensity score matching, there were 511 cases in the guided group and the control group, respectively. The primary endpoint events occurred in 10 patients (1.96%) in the guided group and 23 patients (4.5%) in the control group (HR: 0.45; 95% CI, 0.21-0.95; P = .037). After the guided group adjusted drug doses, the risk of major bleeding was lower than standard DAPT of the control group. Although some patients in the guided group reduced doses earlier, the incidence of MACCE events did not increase in the guided group compared with the control group (4.89% vs 6.07%; P = .41). There was no statistical difference in BARC 1 to 2 minor bleeding (P = .22). Subgroup analysis showed that PFT was more effective in patients with diabetes and multivessel disease.Early observation of dynamic PFT in ACS patients after PCI can guide individualized antiplatelet therapy to reduce the risk of major bleeding without increasing the risk of ischemia.

Platelet function tests: A 5-year audit of platelet function tests done for bleeding disorders in a tertiary care center of a developing country.

INTRODUCTION: The platelet function disorders remain largely undiagnosed or incompletely diagnosed in developing nations due to lack of availability of tests like lumiaggregometry, granule release assay or molecular testing. We performed a retrospective analysis of all the platelet function test (PFT) carried out in past 5 years by Light transmission aggregometery (LTA) using a panel of agonist. The indications and the test results were analyzed by two hematopathologist with the aim to look into the present diagnostic facilities or lack of it for correct diagnosis. This is essential for better management and genetic counselling. MATERIALS AND METHODS: The PFT was performed both on patients and healthy unrelated age specific controls by light transmission aggregometry on Chronolog platelet aggregometer using platelet rich plasma. The panel of agonists included ADP (10µm/l and 2.0 µm/l), epinephrine (10.0 µm/l), collagen (2µg/ml), arachidonic acid (0.75 mM) and ristocetin (1.25 mg/ml & 0.25 mg/l). RESULTS: The 5 years records of 110 cases were audited, 101 of these were tested for clinical bleeding , 35 adults and 66 children. The adults included 29 women and 6 men, 17 to 82 years of age. The children were 16 years to 3 months of age, 30 girls and 36 boys. Platelet function test abnormality was found in 31.6% (32/101) cases ,a majority remained undiagnosed of these about 21% had clinically significant bleeding.The cases diagnosed included Glanzmann Thromboasthenia-11 , von Willebrand Disease-6, Bernard Soulier'syndrome-1, storage pool disorder-6, mild defect of Epinephrine-3, isolated defect with collagen in1. CONCLUSION: An epidemiologically large proportion of platelet function disorders amongst people living in developing nations remain undiagnosed. This lacunae needs to be highlighted and addressed on larger scale. The options available are to increase the available armamentarium of tests or international collaboration with a specialized laboratory to aid in complete diagnosis.

Postoperative bleeding in coronary artery bypass patients on double antiplatelet therapy: predictive value of preoperative aggregometry.

OBJECTIVES: We tested the possible value of routine aggregometry testing for bleeding prediction following coronary artery bypass grafting in patients who received preoperative double antiplatelet therapy. METHODS: In 226 patients undergoing on-pump isolated coronary artery bypass grafting, aggregometry [adenosine diphosphate (ADP) test and ASPI test] was always prospectively performed by Multiplate® analyser immediately before surgery. We assessed the differences in postoperative bleeding according to the type of double antiplatelet therapy [acetylsalicylic acid plus clopidogrel (ASA+C), or plus ticagrelor (ASA+T)], duration of clopidogrel/ticagrelor withdrawal (0-3 days or ≥ 4 days) and results of aggregometry tests. Multivariable predictors of blood losses were sought by linear regressions (drainage amount at 6, 12 and 24 postoperative hours) and logistic regression (increased bleeding: 75th percentile of blood losses at 6 h, i.e. >450 ml). RESULTS: Overall, postoperative blood losses did not significantly differ between treatment groups (median at 6 h: ASA + C = 335 ml, ASA + T = 300 ml, P = 0.21). With longer withdrawal interval, higher rates of patients with normal ADP-related platelet function were observed in both groups (ASA + C: P = 0.04; ASA + T: P = 0.006) but only in the ASA + T group were blood losses significantly smaller at all 3 time points. Bleeders (>450 ml at 6 h) were significantly less frequent among patients with ADP test showing recovered platelet function (ASA + T: P = 0.002; ASA + C: P = 0.053). The correlation between ADP test result and blood losses amount was stronger in the ASA + T group (e.g. at 6 h: r = -0.6; P < 0.001). In multivariable analyses, the ADP test result independently predicted postoperative bleeding in the ASA + T group and the ASPI test in the ASA + C group. CONCLUSIONS: Aggregometry can help in predicting postoperative bleeding in double antiplatelet therapy patients undergoing coronary artery bypass grafting.

Platelet aggregometry cannot identify uremic platelet dysfunction in heart failure patients prior to cardiac surgery.

BACKGROUND: Patients with heart failure often have concomitant renal disease which can result in uremic platelet dysfunction. Determining whether uremia has affected platelets by platelet aggregometry can be challenging in these patients since they are often on antiplatelet medications. This study was undertaken to determine if platelet aggregation studies could identify heart failure patients at risk for uremic bleeding prior to cardiac surgery. METHODS: Platelet aggregation studies from three groups were studied and compared: 17 heart failure patients with mild to moderate renal impairment, 17 heart failure patients without renal abnormalities and 17 healthy volunteers. RESULTS: Platelet aggregation was severely impaired in both heart failure groups with and without renal abnormalities compared to healthy controls, and there were no significant differences in platelet aggregation in response to any of the agonists. There was a pan-decrease in platelet aggregation to all agonists in all heart failure patients. CONCLUSION: Platelet aggregometry does not appear to be useful in measuring platelet dysfunction in heart failure patients with mild to moderate renal impairment.

Impact of an integrated treatment algorithm based on platelet function testing and clinical risk assessment: results of the TRIAGE Patients Undergoing Percutaneous Coronary Interventions To Improve Clinical Outcomes Through Optimal Platelet Inhibition study.

Assessment of platelet reactivity alone for thienopyridine selection with percutaneous coronary intervention (PCI) has not been associated with improved outcomes. In TRIAGE, a prospective multicenter observational pilot study we sought to evaluate the benefit of an integrated algorithm combining clinical risk and platelet function testing to select type of thienopyridine in patients undergoing PCI. Patients on chronic clopidogrel therapy underwent platelet function testing prior to PCI using the VerifyNow assay to determine high on treatment platelet reactivity (HTPR, ≥230 P2Y12 reactivity units or PRU). Based on both PRU and clinical (ischemic and bleeding) risks, patients were switched to prasugrel or continued on clopidogrel per the study algorithm. The primary endpoints were (i) 1-year major adverse cardiovascular events (MACE) composite of death, non-fatal myocardial infarction, or definite or probable stent thrombosis; and (ii) major bleeding, Bleeding Academic Research Consortium type 2, 3 or 5. Out of 318 clopidogrel treated patients with a mean age of 65.9 ± 9.8 years, HTPR was noted in 33.3 %. Ninety (28.0 %) patients overall were switched to prasugrel and 228 (72.0 %) continued clopidogrel. The prasugrel group had fewer smokers and more patients with heart failure. At 1-year MACE occurred in 4.4 % of majority HTPR patients on prasugrel versus 3.5 % of primarily non-HTPR patients on clopidogrel (p = 0.7). Major bleeding (5.6 vs 7.9 %, p = 0.47) was numerically higher with clopidogrel compared with prasugrel. Use of the study clinical risk algorithm for choice and intensity of thienopyridine prescription following PCI resulted in similar ischemic outcomes in HTPR patients receiving prasugrel and primarily non-HTPR patients on clopidogrel without an untoward increase in bleeding with prasugrel. However, the study was prematurely terminated and these findings are therefore hypothesis generating.

Comparison between urinary 11-dehydrothromboxane B2 detection and platelet Light Transmission Aggregometry (LTA) assays for evaluating aspirin response in elderly patients with coronary artery disease.

Aspirin is widely used in the primary and secondary prevention of cardiovascular diseases. The aim of our study was to compare between two established methods of aspirin response, urinary 11-dehydrothromboxane B2 (11dhTXB2) and platelet Light Transmission Aggregometry (LTA) assays in elderly Chinese patients with coronary artery disease (CAD), and to investigate the clinical significance of both methods in predicting cardiovascular events. Urinary 11dhTxB2 assay and arachidonic acid-induced (AA, 0.5mg/ml) platelet aggregation by Light Transmission Aggregometry (LTAAA) assay were measured to evaluate aspirin responses. High-on aspirin platelet reactivity (HAPR) was defined as urinary 11dhTxB2>1500pg/mg or AA-induced platelet aggregation≥15.22%-the upper quartile of our enrolled population. The two tests showed a poor correlation for aspirin inhibition (r=0.063) and a poor agreement in classifying HAPR (kappa=0.053). With a mean follow-up time of 12months, cardiovascular events occurred more frequently in HAPR patients who were diagnosed by LTA assay as compared with no-HAPR patients (22.5% versus 10.6%, P=0.039, OR=2.45, 95% CI=1.06-5.63). However, the HAPR status, as determined by urinary 11dTXB2 measurement, did not show a significant correlation with outcomes.

Assessment of the efficacy and tolerability of clopidogrel napadisilate in Korean patients with coronary stenting: a multicenter, prospective, open-label, randomized trial.

OBJECTIVE: Clopidogrel is indicated for the treatment and prevention of peripheral vascular, cerebrovascular, and coronary artery diseases. This clinical trial was designed to demonstrate that clopidogrel napadisilate (CN) is not inferior to clopidogrel bisulfate (CB) with respect to its effectiveness in inhibiting platelet aggregation. METHODS: This 4 week multi-center, prospective, open-label, randomized trial was conducted at five clinical centers in South Korea. Patients were randomized into the 75 mg CN group or the 75 mg CB group. Platelet aggregation was assessed by the VerifyNow assay. The primary outcome was the difference of the percentage P2Y12 inhibition and the secondary outcome was the baseline and change in P2Y12 reaction units (PRU). RESULTS: There was no significant difference in the percentage P2Y12 inhibition (CN vs. CB, 34.92 ± 21.33% vs. 30.43 ± 17.90%, p=0.203). The mean difference of the percentage P2Y12 inhibition between groups was 4.49%, their two-sided 95% confidence interval was -2.45% to 11.44%, and the lower bound (-2.45%) was greater than the acceptable non-inferiority margin of -9.0%. The baseline PRU was 96.67 ± 76.76 in the CN group and 216.95 ± 68.86 in the CB group (p=0.121), and the change in the PRU was -3.32 ± 51.71 in the CN group and 10.52 ± 43.31 in the CB group (p=0.106). Four subjects experienced AEs (6.3%, 5 events) in the CN group and 7 subjects (11.11%, 13 events) in the CB group without statistical significance (p=0.364). With respect to serious adverse events, 2 events were reported in 2 subjects, 1 in each group. CONCLUSION: Clopidogrel napadisilate was not inferior to clopidogrel bisulfate in terms of antiplatelet efficacy and tolerability, and there were no clinically significant adverse events.

Does the VerifyNow P2Y12 assay overestimate "therapeutic response" to clopidogrel? Insights using short thrombelastography.

In contrast to short thrombelastography (s-TEG) which utilises adenosine diphosphate (ADP) alone, the VerifyNow P2Y12 assay (VN-P2Y12) additionally uses prostaglandin E1 (PGE1) as agonist to assess response to P2Y12 inhibitors. Based upon previous observations, we hypothesised that VN-P2Y12 overestimates the therapeutic effects of clopidogrel. Simultaneous assay with s-TEG and VN-P2Y12 was performed in 43 healthy volunteers and 170 patients either on or off clopidogrel. Furthermore, in 27 patients on clopidogrel 75 mg we compared the effects of adding 22 nM PGE1 to ADP on platelet aggregation in s-TEG to ADP alone. A higher proportion of individuals had a result indicating high platelet reactivity (HPR) with s-TEG than VN-P2Y12 in (i) 43 clopidogrel naïve volunteers (95.3% vs 81.4%, p = NS); (ii) 28 volunteers loaded with clopidogrel 600 mg (39.3% vs 10.7 %, p = < 0.01); (iii) 123 clopidogrel naïve patients (93.5% vs 78%, p = < 0.0001); (iv) 47 patients on clopidogrel 75 mg (42.6% vs 4.3%, p = < 0.0001). In 59 patients loaded with clopidogrel 600 mg/900 mg, a greater proportion had a "therapeutic response" with VN-P2Y12 compared to s-TEG, regardless of the threshold for defining HPR with VN-PY12 (P2Y12 reaction units ≥ 230 or 208). Furthermore, adding PGE1 to ADP in s-TEG potentiated the anti-aggregatory effects of clopidogrel compared with ADP alone. In conclusion, VN-P2Y12 overestimates the functional effects of clopidogrel in some individuals, possibly because it utilises PGE1 in addition to ADP. This could have implications for the ability of VN-P2Y12 to stratify patients as "responders" or "non-responders" to clopidogrel.

[Cardiology. Platelet function testing for clinicians]. / Cardiologie. Tests de réactivité plaquettaire: mise à jour pour le praticien.

Platelet P2YI2 receptor inhibition with clopidogrel, prasugrel or ticagrelor plays a key role to prevent recurrent ischaemic events after percutaneous coronary intervention in acute coronary syndromes or elective settings. The degree of platelet inhibition depends on the antiplatelet medication used and is influenced by clinical and genetic factors. A concept of therapeutic window exists. On one side, efficient anti-aggregation is required in order to reduce cardio-vascular events. On the other side, an excessive platelet inhibition represents a risk of bleeding complications. This article describes the current knowledge about some platelet function tests and genetic tests and summarises their role in the clinical practice.

Markers of endothelial and platelet activation are associated with high on-aspirin platelet reactivity in patients with stable coronary artery disease.

INTRODUCTION: Aspirin inhibits the cyclooxygenase-1 (COX-1) mediated thromboxane A2 synthesis. Despite COX-1 inhibition, in patients with coronary artery disease (CAD), platelets can be activated through other mechanisms, like activation by thrombin. MATERIALS AND METHODS: At baseline in this cross-sectional substudy of the ASCET trial, 1001 stable CAD patients, all on single aspirin treatment, were classified by the PFA100® method, as having high on-aspirin residual platelet reactivity (RPR) or not. Markers of hypercoagulability, endothelial and platelet activation as related to RPR, were evaluated to explore the potential mechanisms behind high on-aspirin RPR. RESULTS: Altogether, 25.9% (n=259) of the patients were found to have high on-aspirin RPR. S-thromboxane B(2) levels were very low and did not differ between patients having high on-aspirin RPR or not. Patients with high on-aspirin RPR had significantly higher levels of von Willebrand Factor (vWF) (124 vs 100%, p<0.001, platelet count (236 vs 224 × 10(9)/l, p=0.008), total TFPI (68.4 vs 65.5 ng/ml, p=0.005) and ß-thromboglobulin (ß-TG) (33.3 vs 31.3 IU/ml, p=0.041) compared to patients with low on-aspirin RPR. No significant differences between the groups were observed in levels of endogenous thrombin generation (ETP), pro-thrombin fragment 1+2 (F1+2), D-dimer, soluble TF (sTF) or P-selectin (all p>0.05). CONCLUSIONS: The high on-aspirin RPR as defined by PFA100® seems not to be due to increased thrombin activity as evaluated with ETP, sTF, F1+2 or D-dimer. The elevated levels of platelet count, ß-TG, TFPI and especially vWF might be explained by increased endothelial and platelet activation in these patients.

Prevalence of poor biological response to clopidogrel: a systematic review.

The existence of poor biological response to clopidogrel has been shown in some patients. Despite the increasing number of studies, this phenomenon remains difficult to quantify. We performed a systematic review to estimate the prevalence of poor biological response to clopidogrel and investigate the factors known to modulate this. An exhaustive search was performed. Altogether 171 publications were identified, providing data for a total of 45,664 subjects. The estimated prevalence of poor biological response to clopidogrel ranged from 15.9% to 49.5% according to the platelet function assay employed. The assays most frequently used were light transmittance aggregometry (LTA), the vasodilator-stimulated phosphoprotein (VASP) assay and the Verifynow® assay. For all these assays, higher cut-off values were associated with a lower prevalence of poor biological response to clopidogrel. However, when choosing a fixed cut-off point for each assay, the prevalence of poor biological response to clopidogrel was highly variable suggesting that other factors could modulate poor biological response to clopidogrel. Finally, none of the studied factors could apparently explain the variability of poor biological response to clopidogrel. This meta-analysis shows that the prevalence of poor biological response depends on the assay employed, the cut-off value and on various unidentified additional factors.

Vasodilator-stimulated phosphoprotein-phosphorylation assay in patients on clopidogrel: does standardisation matter?

The vasodilator-stimulated phosphoprotein-phosphorylation (VASP-P) flow-cytometric assay is mainly used in clinical trials to measure thienopyridine effects. However, there are remarkable differences in the reported optimal cut-offs, ranging from 48-61% platelet reactivity index (PRI). We therefore investigated whether a lack of standardisation might explain the differences in the cut-offs. We measured VASP-P in 62 individuals. PRI was calculated using the mean, geometric mean and median fluorescence intensities (FI). Stability of the blood-samples (time-to-assay, 0-2 days) and stability of the processed samples (0-120 minutes) within the recommended time-span were tested. Time-to-assay significantly influenced the PRI (p<0.001): the PRI from mean FI after two days was lower compared to values on day 1 (52 ± 22.9 vs. 57.7 ± 24.1, p<0.001). The PRI from the geometric mean FI after two days was lower compared to day 0 as well as day 1 (51.3 ± 23 vs. 58.2 ± 24.2 and vs. 59.1 ± 23.7, both p<0.001). The PRI from median FI was stable over time (day 0: 59.1 ± 25%, day 1: 59.7 ± 24.1% and day 2: 56.4 ± 23.9%, all p=ns). Furthermore, the lag time of the processed samples significantly altered the PRI (all p<0.001) with a maximum difference for PRI based on geometric mean FI after 90 minutes compared to baseline (Δ=3.92%PRI, p<0.001). The differences in the reported cut-offs might be explained by a lack of standardisation. More precise standardisation is inevitable, as the PRI significantly depends on the method of calculation, the time-to-assay as well as on the lag time after processing. Tolerably stable results were obtained for the PRI from the median FI.

Impaired spontaneous thrombolytic activity measured by global thrombosis test in males with metabolic syndrome.

INTRODUCTION: In patients with metabolic syndrome (MetS), activity of the fibrinolytic system is generally surmised to be decreased through increased plasminogen activator inhibitor-1 (PAI-1) generation. However, there have been no detailed reports describing whether the clot lysis activity is more dominant than increased clot formation activity for production of the thrombotic state in MetS. METHODS: The global thrombosis test (GTT) is a novel method designed to test both clot formation and clot lysis activities under physiological conditions by using non-anticoagulated blood samples in vitro. We used the GTT to examine the thrombotic or thrombolytic states in males with MetS. RESULTS: Lysis time, which reflects spontaneous clot lysis activity, was significantly longer in MetS subjects (median, 1494s; range, 865-3596s; n=30) than in control subjects (median 1246s; range, 667-2239s; n=53). There was no significant difference between the two groups in occlusion time, which reflects platelet function. The mean level of PAI-1 was significantly higher in MetS subjects than in controls (mean ± SE, 8.7 ± 1.1 and 5.0 ± 0.5 ng/mL, respectively). PAI-1 level and lysis time were significantly correlated (r=0.400, P<0.01). CONCLUSION: These results suggest that male patients with MetS are more likely than controls to experience a thrombotic state through decreased fibrinolytic activity due to increased PAI-1 generation, and that the GTT is useful for evaluating fibrinolytic activity in vitro.

Are P2Y12 reaction unit (PRU) and % inhibition index equivalent for the expression of P2Y12 inhibition by the VerifyNow assay? Role of haematocrit and haemoglobin levels.

The results of the whole blood VerifyNow P2Y12 assay can be expressed as platelet reaction units (PRU) or % inhibition index (%inh), but an optimal cut-off for the assessment of high on-treatment platelet reactivity (HPR) predictive of clinical events has been validated only for PRU. The aim of the study was to study the influence of haematological variables, such as platelet and leukocyte counts or haematocrit / haemoglobin, within the limits indicated by the manufacturer for assay validity, on the results of the test. We performed a comparison of PRU and %inh in a series 186 samples obtained from a clinical trial on patients under dual antiplatelet therapy. The results show that PRU significantly decreases with increasing haematocrit / haemoglobin, whereas %inh does not, due to a parallel change in PRU and iso-TRAP baseline value. PRU and % inhibition index are not equivalent for the definition of HPR, because of their different sensitivities to haematocrit / haemoglobin.

Cross validation of the Multiple Electrode Aggregometry. A prospective trial in healthy volunteers.

Several test systems exist for assessment of platelet function in patients under clopidogrel or aspirin therapy. The objective was to cross-validate the Multiple Electrode Aggregometry (MEA) with three other methods used for determining platelet reactivity under treatment with clopidogrel and aspirin. Platelet function was assessed by the MEA, Vasodilator Stimulated Phosphoprotein (VASP) phosphorylation assay, Platelet Function Analyzer-100 (PFA-100) and the Cone and Platelet Analyzer. Measurements were performed in blood from nine healthy volunteers at baseline, 2, 4, 6 and 72 hours after clopidogrel and aspirin loading. The apparent effect size for clopidogrel and aspirin was greatest for the MEA: treatment induced a 19-fold difference in the arachidonic acid-induced platelet aggregation and an 11-fold difference in the adenosine diphosphate-induced platelet aggregation before/after treatment. For comparison, aspirin and clopidogrel induced only 2.0- to 2.6 -fold changes in other tests (VASP assay, Cone and Platelet Analyzer and PFA-100). Maximal effects were seen 2 hours after aspirin loading and shorter than 72 hours after clopidogrel loading. In conclusion, aspirin and clopidogrel produce stronger signals in the MEA compared to several other methods.