Baseline Platelet Reactivity as Determined by TRAP-6 Induced Aggregation in Whole Blood Is Related to the Rate of Non-Responsiveness to Clopidogrel

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5362-5362 ◽  
Author(s):  
Michael Spannagl ◽  
Csilla Jambor
Keyword(s):  
Arachidonic Acid ◽  
Whole Blood ◽  
Platelet Reactivity ◽  
Area Under The Curve ◽  
Dual Therapy ◽  
Platelet Inhibition ◽  
Multiple Electrode Aggregometry ◽  
A Minor ◽  
Induced Aggregation ◽  
Multiple Electrode

Abstract Background: Platelet inhibition by clopidogrel is often determined using ADP induced aggregometry. TRAP-6 stimulates platelets via the PAR receptors and is influenced to a much lesser extend by aspirin or clopidogrel. The value of the determination of TRAP-6 induced aggregometry in patients treated with clopidogrel is unknown. We evaluated the relation of clopidogrel non-responsiveness as determined by multiple electrode aggregometry (MEA) (1) vs. TRAP-6 induced aggregation. MEA provides a measurement of platelet aggregation in whole blood by monitoring changes in electrical impedance via disposable test cells each containing two pairs of electrodes (1). Methods: Following IRB approval hirudin-anticoagulated blood (Dynabyte, Munich, Germany) was sampled from 993 patients. Aggregation induced by arachidonic acid (0.5 mM), ADP (6.4 μM) or TRAP-6 (32μM) was determined in whole blood using a new generation impedance aggregometer. The device is called Multiplate analyzer (Dynabyte, Munich, Germany), indicating the multiplicity of channels and sensors per channel of the device. After dilution (1:2 with 0.9% NaCl solution) of hirudin-anticoagulated whole blood and stirring for three minutes in the test cuvettes at 37°C, the activator was added and aggregation was continuously recorded for six minutes. The increase of impedance due to the attachment of platelets to the electrodes is detected for each sensor unit separately and transformed to arbitrary aggregation units. The aggregation is quantified as area under the curve (AUC). Results: 618 patients were on chronic therapy with 100 mg aspirin/d, 295 patients on clopidogrel 75 mg/d (237 on dual therapy). Aspirin therapy had no influence on TRAP-6- induced aggregation (112+−260 vs. 110+−25; mean +− sd; aspirin vs. no aspirin, p> 0.05 Mann-Whitney U-test). In contrast clopidogrel induced a minor but significant reduction of TRAP6-induced aggregation (107+− 277 vs. 113+−246; p<0.05). Patients on clopidogrel had a significantly lower ADP induced aggregation (41+−30 vs. 86 +−33) compared to controls (p<0.05), and patients on aspirin had a significantly lower arachidonic acid induced aggregation compared to controls (23+−28 vs. 94 +− 35, p<0.05). 89 of 295 patients (30%) were stratified as clopidogrel non-responders based on the cut-off presented in (2). Patients were divided into 4 quartiles (q1-4) depending on their TRAP-6 induced aggregation. The rate of non-responsiveness in Q1 was 8.1%, in Q2 20%, in Q3 38% and 54% in Q4. ADPinduced aggregation was significantly higher in Q4 than in any other quartile (p<0.05). Conclusion: A high TRAP-6 induced aggregation is associated with an increased rate of clopidogrel non-responsiveness as determined by multiple electrode aggregometry. TRAP-6 induced aggregometry seems to indicate the global platelet potential and might allow a prediction of clopidogrel responsiveness before the induction of therapy.

Multiple electrode aggregometry: A new device to measure platelet aggregation in whole blood

2006 ◽  
Vol 96 (12) ◽  
pp. 781-788 ◽  
Author(s):  
Andreas Calatzis ◽  
Sandra Penz ◽  
Hajna Losonczy ◽  
Wolfgang Siess ◽  
Orsolya Tóth
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Blood Platelet ◽  
Platelet Inhibition ◽  
New Device ◽  
Platelet Aggregometry ◽  
Spontaneous Platelet Aggregation ◽  
Induced Aggregation ◽  
Blood Platelet Aggregation ◽  
Multiple Electrode

SummarySeveral methods are used to analyse platelet function in whole blood. A new device to measure whole blood platelet aggregation has been developed, called multiple electrode platelet aggregometry (MEA). Our aim was to evaluate MEA in comparison with the single platelet counting (SPC) method for the measurement of platelet aggregation and platelet inhibition by aspirin or apyrase in diluted whole blood. Platelet aggregation induced by different concentrations of ADP, collagen and TRAP-6 and platelet inhibition by apyrase or aspirin were determined in citrateor hirudin-anticoagulated blood by MEA and SPC. MEA indicated that spontaneous platelet aggregation was lower, and stimulated platelet aggregation was higher in hirudin- than citrate-anticoagulated blood. In hirudin-anticoagulated, but not citrate-anticoagulated blood, spontaneous platelet aggregation measured by MEA was inhibited by apyrase. For MEA compared with SPC the dose response-curves of agonist-induced platelet aggregation in citrate- and hirudin-blood showed similar EC50 values for TRAP, and higher EC50 values for ADP (non-significant) and collagen (p<0.05). MEA and the SPC method gave similar results concerning platelet-inhibition by apyrase and aspirin. MEA was more sensitive than SPC to the inhibitory effect of aspirin in collagen-induced aggregation. In conclusion, MEA is an easy, reproducible and sensitive method for measuring spontaneous and stimulated platelet aggregation, and evaluating antiplatelet drugs in diluted whole blood. The use of hirudin as an anticoagulant is preferable to the use of citrate. MEA is a promising technique for experimental and clinical applications.

Monitoring of Clopidogrel Using Multiple Electrode Aggregometry.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 883-883 ◽  
Author(s):  
Andreas Calatzis ◽  
Franz Theisen ◽  
Armin J. Reininger ◽  
Michael Spannagl
Keyword(s):  
Platelet Activation ◽  
Platelet Function ◽  
Whole Blood ◽  
Prostaglandin E1 ◽  
Blood Donors ◽  
Direct Thrombin Inhibitor ◽  
Thrombin Inhibitor ◽  
Multiple Electrode Aggregometry ◽  
Induced Aggregation ◽  
Multiple Electrode

Abstract A control of clopidogrel response is one proposed strategy for an improvement of anti-platelet therapy. Different methods have been evaluated for this indication. We assessed ADP induced aggregation in whole blood in healthy blood donors and patients treated with clopidogrel 75 mg qd using a new monitoring method. Methods: Platelet function was determined using multiple electrode aggregometry (MEA) on the Multiplate analyzer (Dynabyte, Munich, Germany). This device uses a single use test cell with two separate impedance sensors, consisting of a total of 4 electrodes and has 5 channels for parallel tests. Aggregation was triggered using ADP (6.4 μM, ADPtest, Dynabyte) and using a combination of ADP (6.4 μM) and prostaglandin E1 (20 nM) (ADPtest high sensitivity = ADPtest HS, Dynabyte). The combination of ADP + prostaglandin E1 (PGE1) is used to enhance sensitivity for the effects of clopidogrel onto ADP induced platelet activation. PGE1 reduces intracellular calcium mobilisation and therefore platelet activation and acts thus synergistical to the effect of clopidogrel. For the analysis 300 μl of blood are analyzed with the addition of 300 μl of saline. Aggregation was quantified by the area under the curve in arbitrary U (1 U corresponds to 10 AU*min). Following IRB approval venous blood was collected from 120 blood donors without anamnestic intake of platelet inhibitors in the 2 weeks before the analysis and 160 patients taking clopidogrel 75 mg qd using the direct thrombin inhibitor Melagatran in a final concentration of 15 μg/ml as the anticoagulant. Results: The distribution of the aggregation values is shown in Fig. 1. The median (min-max) was 83 (36–143) for the blood donors in the ADPtest and 68 (1–130) in the ADPtest HS. In the patient group the median (mix–max) was 30 (2–147) in the ADPtest and 10 (0–108) in the ADPtest HS. If a non-response rate of 25% is assumed, the cut-off between clopidogrel responders and non-responders would be 51 for the ADPtest and 21 for ADPtest HS. Discussion: The comparison of the results of clopidogrel-treated patients and healthy controls (blood donors) reveals a higher sensitivity of ADPtest HS vs. ADPtest for the effects of clopidogrel onto ADP induced aggregation in whole blood. Due to the use of a direct thrombin inhibitor as the anticoagulant in our study platelet function was determined under physiological levels of ionized calcium. For both test methods a significant proportion of patients does not show adequate reductions in their vitro platelet aggregation. Prospective trials are required to show whether a clopidogrel-non-response in this particular method is associated with an increased occurrence of arterial thromboembolism. Fig. 1 Fig. 1.

Third generation P2Y12 antagonists inhibit platelet aggregation more effectively than clopidogrel in a myocardial infarction registry

2014 ◽  
Vol 111 (02) ◽  
pp. 266-272 ◽  
Author(s):  
Philipp Diehl ◽  
Katharina Schnabel ◽  
Patrick Weik ◽  
Qian Zhou ◽  
Christoph Bode ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Platelet Aggregation ◽  
Whole Blood ◽  
Antiplatelet Agents ◽  
Platelet Inhibition ◽  
Current Standard ◽  
Antiplatelet Effect ◽  
P2y12 Antagonists ◽  
Significant Difference ◽  
Induced Aggregation

SummaryThe current standard of antiplatelet therapy of patients after myocardial infarction includes the P2Y12 receptor antagonists clopidogrel, prasugrel or ticagrelor. This study aimed to compare the antiplatelet effect of clopidogrel, prasugrel and ticagrelor in patients after myocardial infarction. In a single-centre registry the antiplatelet effect of clopidogrel, prasugrel and ticagrelor was investigated by aggregometry in patients after myocardial infarction. To assess the overall capacity of platelet aggregation whole blood was induced with thrombin receptor activating peptide (TRAP; 32 μM). To specifically quantify the effect of P2Y12 antagonists, whole blood was stimulated with 6.4 μM adenosine diphophosphate (ADP). Relative ADP induced aggregation (r-ADP-agg) was defined as the ADP-TRAP ratio to reflect an individual degree of P2Y12-dependent platelet inhibition. Platelet function of 238 patients was analysed [clopidogrel (n=58), prasugrel (n=65), ticagrelor (n=115)]. The r-ADP-agg was 35 ± 14% for patients receiving clopidogrel, 28 ± 10% for patients receiving prasugrel and 26 ± 11% for patients receiving ticagrelor. The r-ADP-agg was significantly lower in patients treated with prasugrel (p=0.0024) or ticagrelor (p<0.0001) compared to clopidogrel. There was no significant difference between patients receiving prasugrel or ticagrelor (p=0.2559). In conclusion, prasugrel and ticagrelor provide a stronger platelet inhibition compared to clopidogrel in patients after myocardial infarction. No significant difference in platelet inhibition was detected between prasugrel and ticagrelor. (registry for patients after Myocardial Infarction Treated with AntiPlatelet agents; DRKS00003146).

scholarly journals Selective and rapid monitoring of dual platelet inhibition by aspirin and P2Y12 antagonists by using multiple electrode aggregometry

2010 ◽  
Vol 8 (1) ◽  
pp. 9 ◽  
Author(s):  
Sandra M Penz ◽  
Isabell Bernlochner ◽  
Orsolya Tóth ◽  
Reinhard Lorenz ◽  
Andreas Calatzis ◽  
...  
Keyword(s):  
Platelet Inhibition ◽  
Multiple Electrode Aggregometry ◽  
P2y12 Antagonists ◽  
Rapid Monitoring ◽  
Multiple Electrode

Effect of Oestrogen Dose on Whole Blood Platelet Activation in Women Taking New Low Dose Oral Contraceptives

1994 ◽  
Vol 72 (06) ◽  
pp. 926-930 ◽  
Author(s):  
Lucy A Norris ◽  
John Bonnar
Keyword(s):  
Arachidonic Acid ◽  
Oral Contraceptive ◽  
Platelet Activation ◽  
Oral Contraceptives ◽  
Whole Blood ◽  
Contraceptive Use ◽  
Blood Platelet ◽  
Individual Treatment ◽  
Oral Contraceptive Use ◽  
Induced Aggregation

SummaryOral contraceptive use is known to cause changes in the haemostatic system. These changes are thought to be related to oestrogen dose and to provide a possible link between the increased risk of thromboembolic disease known to occur in women taking oestrogen containing oral contraceptives. This study measured whole blood platelet activation, serially, in women taking oral contraceptives containing 20 μg and 30 μg ethinyloestradiol combined with desogestrel. Increased levels of ADP and arachidonic acid induced aggregation were observed in women taking the 30 μg ethinyloestradiol combination. Platelet release of β-thromboglobulin (βTG) was also significantly increased. Increased collagen induced aggregation was observed but this failed to reach statistical significance for the individual treatment groups. In women taking the 20 μg ethinyloestradiol combination, a significant increase was only observed when platelets were stimulated with arachidonic acid. Platelet factor 4 (PF4) levels were unchanged in both groups. Significantly higher levels of βTG were observed in women taking the 30 μg ethinyloestradiol combination compared with women taking the 20 μg ethinyloestradiol combination. These results show that oral contraceptive use is associated with platelet activation. Women taking the 20 μg ethinyloestradiol combination show less changes in platelet activation than women taking the 30 μg ethinyloestradiol combination. This lower dose pill may therefore be particularly suitable for high risk women wishing to use oral contraception.

P1930Pharmacodynamic effects of vorapaxar as an add-on antiplatelet therapy in patients with and without diabetes mellitus: the optimizing anti-platelet therapy in diabetes mellitus (OPTIMUS)-5 study

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
F Franchi ◽  
F Rollini ◽  
V Kairouz ◽  
J Rivas ◽  
A Rivas ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Triple Therapy ◽  
Antiplatelet Therapy ◽  
Primary Endpoint ◽  
Platelet Reactivity ◽  
Dual Therapy ◽  
Mean Difference ◽  
Adjunctive Treatment ◽  
Induced Aggregation ◽  
Cox 1

Abstract Background Vorapaxar (Vora) is a protease-activated receptor (PAR)-1 inhibitor which when added to dual antiplatelet therapy (DAPT) in patients with a history of myocardial infarction (MI) or with peripheral arterial (PAD) reduces thrombotic cardiovascular events at the expense of increased bleeding. The efficacy of Vora is enhanced in patients with diabetes mellitus (DM) compared to non-DM. However, the differential pharmacodynamic (PD) effects of Vora in DM vs non-DM patients are unknown. Moreover, although withdrawal of aspirin has emerged as a strategy to reduce bleeding when adjunctive antithrombotic therapies are used, the PD effects of Vora after stopping aspirin in DAPT treated patients is unknown. Purpose To assess the PD effects of Vora in addition to standard DAPT as well as in combination with clopidogrel following aspirin withdrawal in patients with and without DM. Methods This was a prospective parallel-design PD study conducted in post-MI or PAD patients with and without DM. Patients on DAPT with aspirin (81mg/qd) and clopidogrel (75mg/qd) were divided in two groups according to DM status. Each cohort was treated with Vora (2.5mg/qd) in addition to DAPT (i.e., triple therapy) for 30 days and afterwards stopped aspirin and maintained treatment with Vora plus clopidogrel (i.e., dual therapy) for other 30 days. PD testing using 5 different assays was conducted at 3 time-points: baseline (while on DAPT); after 30 days of triple therapy; after 30 days of dual therapy. The primary endpoint was the non-inferiority of CAT (Collagen-ADP-TRAP)-induced aggregation, a marker of global platelet reactivity, of Vora plus clopidogrel (dual therapy) vs Vora plus DAPT (triple therapy). Results The PD population was composed of a total of 64 patients (DM, n=30; non-DM, n=34). Although adding Vora to DAPT significantly reduced CAT-induced aggregation, stopping aspirin was associated with an increase in CAT-induced aggregation in both DM (mean difference=12; 95% CI: 3 to 21; p=0.010) and non-DM (mean difference=10; 95% CI: 4 to 16; p=0.003), thus not meeting the primary endpoint of non-inferiority (Figure). The magnitude of such increase was higher in DM compared with non-DM (p=0.036). Although Vora abolished TRAP-induced aggregation in both DM and non-DM patients, it did not affect markers of clot kinetics including speed of thrombin generation. Aspirin withdrawal was associated with a marked increase in makers sensitive to cyclooxygenase-1 (COX-1) blockade; markers of P2Y12 signaling were higher in DM compared to not DM after aspirin withdrawal. CAT-induced aggregation Conclusion Adjunctive treatment with Vora reduces platelet-mediated thrombogenicity without affecting clot kinetics in both DM and non-DM patients while on DAPT. However, platelet-mediated thrombogenicity is increased after aspirin withdrawal, a phenomenon which is enhanced in DM patients underscoring the pivotal contribution of the COX-1 signaling pathway in these high risk patients. Acknowledgement/Funding The study was supported in part by an investigator initiated study grant from Merck

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