Multiplate Research Articles

Aspirin resistance in patients with acute coronary events: Risk factors and prevalence as determined by whole blood multiple electrode aggregometry

To determine the prevalence of aspirin resistance and associated risk factors based on biochemical parameters using whole blood multiple electrode aggregometry. The study was conducted at the outpatients cardiology clinic of the Universiti Kebangsaan Malaysia Medical Centre (UKMMC) from August 2011 to February 2012. Subjects on aspirin therapy were divided into two groups; first-ever coronary event and recurrent coronary event. Aspirin resistance was measured by a Multiplate(®) platelet analyser. A total of 74 patients (63 male, 11 female), with a mean age of 57.93 ± 74.1years were enrolled in the study. The patients were divided into two groups -first-ever coronary event group (n=52) and recurrent coronary event group (n=22). Aspirin resistance was observed in 12 out of 74 (16%) of the study patients, which consisted of 11 patients from the first-ever coronary event group and one patient from the recurrent coronary event group. There were significant correlations between aspirin resistance and age (r = -0.627; p = 0.029), total cholesterol (r = 0.608; p = 0.036) and LDL (r = 0.694; p = 0.012). LDL was the main predictor for area under the curve (AUC) for aspirin resistance. However, there was no association between aspirin resistance and cardiovascular events in both groups in this study. Aspirin resistance was observed in 16% of the study population. LDL was the major predictor of aspirin resistance. No association was found in the study between aspirin resistance with recurrent coronary events.

Reversal strategy in antagonizing the P2Y12‐inhibitor ticagrelor

Patients on antiplatelet therapy have a higher incidence of bleeding complications. Reversal of antiplatelet drug effects is an important issue at trauma or emergency departments. For old and conventional anticoagulants, reversal strategies are established. While the effects of ticagrelor are reversible, developing a method to restore platelet function in patients is of importance due to its longer half-life (approximately 8h), compared with other P2Y12 -inhibitors. We report an ex vivo model to reverse the effects of the novel and highly effective P2Y12 -inhibitor ticagrelor in 20 healthy volunteers. To normalize platelet reactivity, we added increasing amounts of autologous platelet-rich plasma (PRP) to whole blood which was obtained 3h after the intake of 180mg of ticagrelor. Platelet aggregation was assessed by whole blood multiple electrode aggregometry (MEA), which is based on impedance aggregometry. The basal ADP-induced platelet aggregation averaged 71±16U (Units). Ticagrelor decreased ADP-induced platelet aggregation to 16±8U. A clear dose-response was obtained after spiking whole blood with increasing amounts of PRP. It is estimated that ≥2 units of apheresis platelet concentrates will be necessary to completely restore baseline platelet aggregation in the majority of patients after ticagrelor. Platelets dose dependently improve ex vivo platelet aggregation of subjects after a loading dose of 180mg of ticagrelor, making transfusion of platelet concentrates potentially useful in bleeding patients and those who need to undergo emergency surgery.

Impact of antiplatelet therapy and cardiopulmonary bypass on platelet function in patients undergoing coronary artery bypass grafting using multiple electrode aggregometry

Results Group of patients exposed to ASA preoperatively had lower values of ASPI test (P<0.001) comparing to patients not receiving ASA. However, we registered 28.6% ASA resistant patients. Both ASPI (P<0.001) and ADP (P<0.001) test values increased significantly at POD 4, suggesting postoperative platelet hyperactivity. Postoperatively, we registered 33.3% ASA resistant patients despite higher ASA dosing regimen. Conclusion MEA can recognize patients with ASA resistance during the both the pre- and post- CABG period. Postoperatively, ASA 300mg did not sufficiently inhibit platelet aggregation in 33.3% patients. In this subgroup, dual antiplatelet therapy with ASA and clopidogrel could be useful for maintaining graft patency, and preventing adverse ischemic events.

Defining predictive values using three different platelet function tests for CYP2C19 phenotype status on maintenance dual antiplatelet therapy after PCI

Published data suggests that the presence of CYP2C19*2 or *3 loss of function (LOF) alleles is indicative of increased platelet aggregation and a higher risk of adverse cardiovascular events after clopidogrel administration. We sought to determine cut-off values using three different assays for prediction of the CYP2C19 phenotype in Korean percutaneous coronary intervention (PCI) patients. We enrolled 244 patients with drug-eluting stent implantation who were receiving clopidogrel and aspirin maintenance therapy for one month or more. Platelet reactivity was assessed with light transmittance aggregometry (LTA), multiple electrode aggregometry (MEA) and the VerifyNow P2Y12 assay (VN). The CYP2C19 genotype was analyzed by polymerase chain reaction (PCR) and snapshot method. The frequency of CYP2C19 LOF allele carriers was 58.6%. The cut-off values from LTA, MEA and VerifyNow for the identification of LOF allele carriers were as follows: 10 µM ADP-induced LTA ≥ 48 %, VN > 242 PRU and MEA ≥ 37 U. Between the three tests, correlation was higher between LTA vs. VN assays (r = 0.69) and LTA vs. MEA (r = 0.56), with moderate agreement (κ = 0.46 and κ = 0.46), but between VN assay and MEA, both devices using whole blood showed a lower correlation (r = 0.42) and agreement (κ = 0.3). Our results provide guidance regarding cut-off levels for LTA, VerifyNow and MEA assays to detect the CYP2C19 LOF allele in patients during dual antiplatelet maintenance therapy.

Use of ROTEM and MEA in a cardiac surgical patient with ITP

To the Editor: Perioperative management of idiopathic thrombocytopenic purpura (ITP) is challenging because the platelet count does not directly indicate platelet function. We report the use of rotation thromboelastometry (ROTEM; Tem International, Munich, Germany) and multiple electrode aggregometry (MEA) using a Multiplate analyzer (Dynabyte Medical, Munich, Germany) (Supplemental Fig. 1) to manage a 71-year-old man with an 8-year history of ITP who required an aortic valve replacement. ITP is characterized by the formation of antiplatelet antibodies that target platelet membrane glycoproteins, resulting in accelerated platelet destruction. After induction of anesthesia, the maximum clot firmness (MCF) was low in the EXTEM test but was normal in the FIBTEM test, and MEA measurements were all below the normal range, which are independent of activators (Supplemental Tables 1, 2). These results indicated a reduction in the platelet component as reflected by MCFextem–MCFfibtem [1] and slower and less dense occupation of the sensor wires on MEA, decreasing the aggregation velocity and the maximum aggregation [2]. During cardiopulmonary bypass, the MCF was reduced in EXTEM and FIBTEM tests, and these results together with all MEA measurements indicated hemodilution, coagulation factor depletion, and platelet dysfunction (Supplemental Tables 1, 2). According to the ROTEM-based algorithm, 30 U platelets and 5 U fresh frozen plasma were transfused, which normalized the ROTEM data and the unsatisfactorily corrected MEA data (Supplemental Tables 1, 2). These results reflected reduced platelet aggregation because of apheresis and storage. MEA has been reported to be useful for assessment of platelet responsiveness to antiplatelet therapy. As ROTEM is unable to evaluate primary hemostasis, use of ROTEM and MEA together might be functionally complementary. However, the patient did not require any more blood products, and the results of MEA did not affect the transfusion decision.

Obesity is associated with poor response to clopidogrel and an increased susceptibility to protease activated receptor-1 mediated platelet activation

Obesity is associated with a prothrombotic state resulting from increased thrombin generation, platelet hyper-reactivity, and decreased fibrinolysis. Data on the influence of obesity on clopidogrel-mediated platelet inhibition are conflicting and limited to platelet function tests. Moreover, there are no data on thrombin-inducible platelet activation in obese patients. We therefore investigated response to clopidogrel therapy and protease activated receptor (PAR)-1 mediated platelet activation in obese and nonobese patients undergoing angioplasty and stenting for cardiovascular disease. The vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, multiple electrode aggregometry (MEA) with adenosine diphosphate (ADP), and surface expressions of P-selectin and activated glycoprotein (GP) IIb/IIIa in response to ADP and thrombin receptor activating peptide (TRAP)-6 were assessed in 71 obese and 245 nonobese patients. Obesity was independently associated with higher residual platelet reactivity by the VASP assay and MEA ADP, and with platelet surface expressions of P-selectin and activated GPIIb/IIIa in response to ADP (all P ≤ 0.04). Further, high on-treatment residual ADP-inducible platelet reactivity by the VASP assay and by MEA ADP were significantly more frequent in obese patients compared with nonobese patients (both P ≤ 0.04). Finally, PAR-1 mediated platelet activation as assessed by expression of P-selectin and activated GPIIb/IIIa in response to TRAP-6 was significantly more pronounced in obese patients than in patients without obesity (both P ≤ 0.02). In conclusion, obese patients undergoing angioplasty and stenting exhibit a diminished response to clopidogrel and an increased susceptibility to TRAP-6 inducible platelet activation.

Multiple electrode aggregometry in antiplatelet-related intracerebral haemorrhage

As the population ages, antiplatelet agents are increasingly used in patients with cardiovascular diseases. Due to impaired platelet activity, these patients are at increased risk for bleeding complications and this is of particular importance in patients with intracerebral haemorrhage. The multiple electrode aggregometry analyser Multiplate (Roche Diagnostics, Mannheim, Germany) was introduced in 2006 to monitor the effectiveness of antiplatelet drugs in interventional cardiology. As a point-of-care device, it allows bedside assessment of platelet activity within minutes through analysis of a sample of whole blood. In patients treated with antiplatelet medication and in need of urgent cardiac surgery, these devices allow prediction of intraoperative blood loss and their use was implemented within respective guidelines to direct transfusion strategies. We used the Multiplate analyser for rapid assessment of antiplatelet activity in a patient who developed an intracerebral haemorrhage after administration of aspirin and clopidogrel. Antiplatelet activity was assessed within 10minutes while the patient was transferred to the operating room and after transfusion of platelet concentrates and administration of desmopressin and tranexamic acid, repeated Multiplate analysis demonstrated nearly normalized platelet activity. In our view, there is great potential for this device to improve treatment in neurosurgery and especially the treatment of antiplatelet-related intracerebral haemorrhage. Instant assessment of antiplatelet activity or effectiveness of haemostatic measures is facilitated and furthermore, patients with normal platelet activity despite a positive history of antiplatelet medication intake can be identified. In these patients, empiric administration of haemostatic substances would unnecessarily increase the risk of thromboembolic events.

Thienopyridines resistance and recovery of platelet function after discontinuation of thienopyridines in cardiac surgery patients

Patients who undergo cardiac operations under the effects of thienopyridines have a greater risk of major postoperative bleeding, transfusions and surgical revision due to bleeding. Discontinuation of thienopyridine is suggested but an adequate recovery period following discontinuation is still under debate, with opinions ranging from 3 to 7 days. The aim of this study was to assess the rate of recovery of thienopyridine-resistant patients and the time taken for resumption of platelet function after discontinuation of thienopyridine, in the setting of patients scheduled for cardiac operations. This was a retrospective study, based on 344 patients screened for platelet aggregation before cardiac operations. All the patients received thienopyridines within 7 days prior to the test. Multiple electrode aggregometry adenosine diphosphate test was used to assess platelet aggregation before the operation. Thienopyridine resistance rate was 28%. Patients receiving clopidogrel had a significantly higher rate (32%) of resistance, compared with those receiving ticlopidine (14%) and thienopyridine resistance was significantly associated with platelet count (P = 0.006). The time taken to recover platelet function after thienopyridine discontinuation was variable between individuals; the only factor associated with a faster recovery time was the serum bilirubin value (P = 0.002). Platelet aggregation values high enough to avoid major bleeding were reached 3 days after discontinuation (95% confidence interval: 2-4 days); however, a complete recovery of platelet function was reached only after 8 days (95% confidence interval: 7-9 days). Patient-specific factors determine the effectiveness of thienopyridine treatment and platelet function recovery rate. Among these, platelet count (for thienopyridine resistance) and serum bilirubin values (for platelet function recovery rate) should be considered.

Impact of the proton pump inhibitors and CYP2C19*2 polymorphism on platelet response to clopidogrel as assessed by four platelet function assays

Previous studies suggested a possible negative interference of proton pump inhibitors (PPIs) on clopidogrel's antiplatelet effect because of the competitive inhibition of the CYP 2C19 isoenzyme. Moreover, carriers of the loss-of-function allele of CYP2C19 polymorphism (CYP2C19*2) display significantly lower responses to clopidogrel. In this study, we investigated the association between CYP2C19*2 genotype, PPI intake and clopidogrel resistance in patients with coronary artery disease (CAD) and their effect on clinical outcome. We recruited 95 patients with CAD receiving chronic clopidogrel therapy in combination with aspirin. Platelet reactivity was simultaneously assessed by INNOVANCE PFA-100 P2Y, ADP-induced light transmission aggregometry (LTA), flow-cytometric vasodilator-stimulated phosphoprotein (VASP)-phosphorylation assay and multiple electrode aggregometry (Multiplate). Cardiovascular outcomes were recorded during 1-year follow-up period. Only platelet reactivity assessed by measuring platelet phosphorylated-VASP demonstrated a significant higher platelet reactivity in carriers of CYP2C19*2 (p=0.023). The other methods displayed higher - but not statistically significant - platelet reactivity in patients carrying the CYP2C19*2 variant as compared with non-carriers. Patients on PPIs demonstrated almost similar suppression of platelet reactivity in comparison with those not treated with PPIs by all platelet function assays. In logistic regression analysis none of the platelet function assays measurements were related with clinical outcomes. Similarly neither CYP2C19*2 genetic variant nor PPI treatment were associated with adverse clinical events. PPI co-administration did not influence clopidogrel's antiplatelet effect on laboratory testing by all platelet function assays used. On the contrary, patients carrying CYP2C19*2 genotype had significantly higher residual platelet reactivity as estimated by VASP-phosphorylation assay.

Assessment of the performances of AcuStar HIT and the combination with heparin-induced multiple electrode aggregometry: A retrospective study

Early diagnosis of immune heparin-induced thrombocytopenia (HIT) is challenging. HemosIL® AcuStar HIT and heparin-induced multiple electrode aggregometry (HIMEA) were recently proposed as rapid diagnostic methods. We conducted a study to assess performances of AcuStar HIT-IgG (PF4-H) and AcuStar HIT-Ab (PF4-H). The secondary objective was to compare the performances of the combination of Acustar HIT and HIMEA with standardised clinical diagnosis. Sera of 104 suspected HIT patients were retrospectively tested with AcuStar HIT. HIMEA was performed on available sera (n=81). The clinical diagnosis was established by analysing in a standardized manner the patient's medical records. These tests were also compared with PF4-Enhanced®, LTA, and SRA in subsets of patients. Thresholds were determined using ROC curve analysis with clinical outcome as reference. Using the recommended thresholds (1.00AU), the negative predictive value (NPV) of HIT-IgG and HIT-Ab were 100.0% (95% CI: 95.9%-100.0% and 95.7%-100.0%). The positive predictive value (PPV) were 64.3% (95% CI: 35.1%-87.2.2%) and 45.0% (95% CI: 23.2%-68.6%), respectively. Using our thresholds (HIT-IgG: 2.89AU, HIT-Ab: 9.41AU), NPV of HIT-IgG and HIT-Ab were 100.0% (95% CI: 96.0%-100.0% and 96.1%-100.0%). PPV were 75.0% (95% CI: 42.7%-94.5%) and 81.8% (95% CI: 48.3%-97.7%), respectively. Of the 79 patients with a medium-high pretest probability score, 67 were negative using HIT-IgG (PF4-H) test at our thresholds. HIMEA was performed on HIT-IgG positive patients. Using this combination, only one patient on 79 was incorrectly diagnosed. Acustar HIT showed good performances to exclude the diagnosis of HIT. Combination with HIMEA improves PPV.

Platelet Inhibition by Abciximab Bolus-Only Administration and Oral ADP Receptor Antagonist Loading in Acute Coronary Syndrome Patients: The Blocking and Bridging Strategy

IntroductionCurrent guidelines still recommend the bolus and infusion administration of glycoprotein IIbIIIa inhibitors in patients with high-risk acute coronary syndrome undergoing percutaneous coronary intervention. We sought to evaluate the extent of platelet inhibition by a blocking and bridging strategy with intracoronary abciximab bolus-only administration and oral loading of adenosine diphosphate receptor antagonists. Patients and methodsFifty-six consecutive high-risk acute coronary syndrome patients with bolus-only abciximab administration (0.25mg/kg i.c.) and loading with 600mg clopidogrel (55%) or 60mg prasugrel (45%) were included in this study. Platelet aggregation induced by thrombin receptor-activating peptide and adenosine diphosphate was measured by multiple electrode aggregometry up to 7days. ResultsThrombin receptor-activating peptide induced platelet aggregation was significantly suppressed for a minimum of 48h (45±17U) and returned to a normal range (>84U) after 6days (90±26U; p<0.001). Co-medication with prasugrel significantly reduced adenosine diphosphate-induced (p=0.002) and thrombin receptor-activating peptide-induced (p=0.02) platelet aggregation compared with clopidogrel throughout the observation period. No stent thrombosis or repeat myocardial infarction occurred at 30-day follow-up. ConclusionsImmediate blocking of platelet aggregation in high-risk acute coronary syndrome patients by intracoronary abciximab bolus-only administration and bridging to prolonged inhibition via oral blockade of ADP receptors effectively inhibited overall platelet reactivity for at least 48h, questioning the value of continuous abciximab infusion. Co-medication with prasugrel vs. clopidogrel synergistically augmented platelet inhibition.

Pneumatic tube transport affects platelet function measured by multiplate electrode aggregometry

Multiple electrode aggregometry (MEA) is used to measure platelet function. Pneumatic tube transport systems (PTS) for delivery of patient samples to a central laboratory are often used to reduce turnaround time for vital analyses. We evaluated the effects of PTS transport on platelet function as measured by MEA.Duplicate samples were collected from 58 individuals. One sample was sent using PTS and the other was carried by personnel to the lab. Platelet function was measured by means of a Multiplate® analyzer using the ADP test, ASPI test, COL test, RISTO test and TRAP test.Samples transported using PTS showed a reduction of AUC-values of up to a 100% of the average as compared to samples carried by personnel and a majority showed reductions of AUC-values greater than 20% of the average. Bias±95% limits of agreement for the ADP test were 26±56% of the average. Bias±95% limits of agreement for the ASPI test were 16±58% of the average. Bias±95% limits of agreement for the COL test were 20±54% of the average. Bias±95% limits of agreement for the RISTO were 14±79% of the average. Bias±95% limits of agreement for the TRAP test were 19±45% of the average.We conclude that PTS transport affect platelet activity as measured by MEA. We advise against clinical decisions regarding platelet function on the basis of samples sent by PTS in our hospital settings.

Assessment of blood clot formation and platelet receptor function ex vivo in patients with primary Sjögren's syndrome

ObjectivesPrimary Sjögren's syndrome (pSS) shares clinical features and pathogenetic mechanisms with systemic lupus erythematosus (SLE). SLE is associated with an increased thromboembolic risk; however, it is unclear whether pSS patients...

Mechanism of Cancer Cell Death Induced by Hydrogen Discharged from Palladium Base Hydrogen Storage Alloy

The mechanism of cancer cell death induced by hydrogen discharged from Pd-5at.% Ni hydrogen storage alloy has been investigated. Cancer cell (HeLa : cervical cancer cell) death was observed in the limited region within ~ 3 mm from the sample. The measurement of surviving fraction of cells revealed that almost all the cancer cells in the well of 96-well multi plate, 6.2 mm in diameter were extinct (p &lt; 0.01), while no detectable influence was observed in the normal cells. From the fluorescent imaging experiment, it was indicated that the cell death induced by discharged hydrogen was due to the “Apoptosis” and hydrogen peroxide was detected in both intracellular and extracellular regions. Furthermore, the generation of hydrogen radical and hydroxyl radical was observed in the ESR measurement. From the results obtained, the mechanism of cancer cell death is proposed.

Response to antiplatelet therapy is independent of endogenous thrombin generation potential

BackgroundThrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy. Patients and methodsThrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting. ResultsPeak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p=0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR. ConclusionResponse to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.

Preserved thrombin‐inducible platelet activation in thienopyridine‐treated patients

Abundant thrombin generation may be a major reason for subsequent thromboembolic events in patients with cardiovascular disease receiving dual antiplatelet therapy. We therefore investigated the susceptibility of thienopyridine responders and nonresponders to thrombin receptor-activating peptide (TRAP)-6- and adenosine diphosphate (ADP)-inducible platelet activation. Response to clopidogrel or prasugrel was determined by the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay and multiple electrode aggregometry (MEA) in 317 patients undergoing angioplasty and stenting for cardiovascular disease. Baseline, TRAP-6-, and ADP-inducible P-selectin expression, activated glycoprotein IIb/IIIa (GPIIb/IIIa) and monocyte-platelet aggregate (MPA) formation were measured as sensitive parameters of platelet activation. In patients with high on-treatment residual ADP-inducible platelet reactivity (HRPR), baseline P-selectin expression, GPIIb/IIIa and MPA formation were similar to those in patients without HRPR (all P > 0.05). After platelet activation with TRAP-6 or ADP, patients with HRPR by both assays exhibited significantly higher levels of P-selectin expression, GPIIb/IIIa and MPA formation than patients with an adequate thienopyridine-mediated platelet inhibition (all P ≤ 0.02). However, high levels of TRAP-6-inducible P-selectin, GPIIb/IIIa and MPA formation also occurred in 20.4%, 19.1% and 20.1% of the good responders by the VASP assay, and in 19.6%, 16.6% and 20.6% of the good responders by MEA, respectively. Thienopyridine nonresponders are more susceptible to thrombin- and ADP-inducible platelet activation than patients with good platelet inhibition. However, even patients with adequate thienopyridine-mediated platelet inhibition often show a preserved responsiveness to thrombin. These patients may benefit from additional thrombin receptor blockage or inhibition of thrombin generation.

Non-Responders to Antiplatelet Therapy in Patients with Left Ventricular Assist Devices

Purpose Thromboembolic complications are a deleterious adverse event after left ventricular assist device (LVAD) implantation. Because of individual responsiveness to antiplatelet treatment with the COX-inhibitor aspirin and P2Y12-inhibitors as clopidogrel and prasugrel, personalized treatment based on platelet function testing may significantly reduce thromboembolic complications in LVAD patients. The present study was designed to define the frequency of aspirin and clopidogrel resistence in LVAD patients. Methods and Materials Responsiveness to antiplatelet treatment was prospectively assessed by multiple electrode aggregometry in 39 (mean age 52±11yrs., ischemic cardiomyopathy 56.4%) LVAD outpatients (HVAD® n=30, HeartMate II® n=9). Twenty-five patients received the standard daily dose of 100mg aspirin, four were treated with 200mg aspirin, one patient with 75mg clopidogrel and three with a combination of 100mg aspirin and either 75mg clopidogrel (n=2) or 10mg prasugrel. The daily aspirin dosage was doubled in non-responders and patients were tested again after two weeks. Results Multiple electrode aggregometry revealed non-responsiveness to the initial antiplatelet regimen in three patients (7.7%) and only moderate responsiveness in one patient (2.6%). The remaining 35 patients (89.7%) showed a good in vitro efficacy of the antiplatelet therapy. An adaption of the antiplatelet therapy by doubling the daily aspirin dosage led to adequate platelet inhibition, as revealed by multiple electrode aggregrometry, two weeks after change of treatment. Conclusions As shown by objective measures, non-responsiveness to antiplatelet therapy is a common finding in patients after left ventricular assist device implantation. Therefore, personalized treatment according to the platelet function testing may reduce the incidence of thromboembolic complications.

Platelet Activation and Inhibition iN Sickle cell disease (PAINS) study

Platelet activation/aggregation in sickle cell disease (SCD) may promote tissue ischemia, suggesting that antiplatelet therapy may be useful. However, the assessment of platelet function and the effect of antiplatelet therapy in blood from SCD patients may be confounded by hemolysis with the release of adenosine 5′-diphosphate (ADP). Here we evaluate the levels of platelet activation markers in SCD adolescents vs. normal controls and compare, by multiple methods, the effect of in vitro blockade of the platelet ADP receptor P2Y12 by prasugrel's active metabolite, R-138727. Platelet activation markers in blood from SCD adolescents (n = 15) and healthy adults (n = 10), and the effect of R-138727 (0.1–10 µM) added in vitro, were evaluated with and without ADP stimulation. The circulating levels of platelet–monocyte and platelet–neutrophil aggregates were significantly higher (p < 0.01) in SCD patients than in healthy controls. R-138727, in a concentration-dependent manner, inhibited platelet function in both SCD patients and healthy subjects as judged by ADP-stimulated light transmission aggregation, VerifyNow® P2Y12 assay, multiple electrode aggregometry, and flow cytometric analysis of platelet vasodilator-stimulated phosphoprotein, activated GPIIb-IIIa and P-selectin. The R-138727 IC50s for each assay were not significantly different in SCD vs. healthy subjects. In summary: (1) The high circulating levels of platelet–monocyte and platelet–neutrophil aggregates demonstrate in vivo platelet activation in SCD and may be useful as markers of the in vivo pharmacodynamic efficacy of antiplatelet therapy in SCD. (2) The similar in vitro R-138727 IC50s in SCD and healthy subjects suggest that the prasugrel dose-dependence for platelet inhibition in SCD patients will be similar to that previously observed in healthy subjects.

Pain-associated Respiratory Failure in Chest Trauma

Pain-associated Respiratory Failure in Chest Trauma

Role of VASP Phosphorylation Assay in Monitoring the Antiplatelet Therapy

Abstract Dual antiplatelet treatment with clopidogrel and aspirin represents standard regimen in prevention of thromboembolic events in patients with ischemic heart disease undergoing percutaneous coronary intervention (PCI). One of the greatest pitfalls of clopidogrel treatment is large inter-individual variability in response. Large amount of patients does not respond adequately and therefore are not „protected“ even in spite of receiving the therapy. Poor responders are exposed to three-fold increased risk of myocardial infarction, stent thrombosis and cardiac death. Clopidogrel is an antiplatelet prodrug, whose active metabolite inhibits platelet function by irreversible binding to the (adenosine diphosphate) platelet receptor P2Y12. Receptor P2Y12 plays primal role in ADP-mediated platelet activation, and also in mechanism of action of ADP inhibitors such as clopidogrel, prasugrel etc. Reasons stated above, raised the necessity for implementing reliable laboratory test in order to identify the unprotected patients. In an ideal scenario, such test would serve to adjust the dose and guide the individual tailored treatment. Vasodilator Stimulated Phosphoprotein (VASP) is an intracellular platelet protein which is non phosphorylated at basal state. Since its relation in cascade with P2Y12 receptor, VASP phosphorylation corerlates with inhibition of P2Y12 which is the receptor of prime importance in ADP mediated activation of platelets and as is primary target of ADP inhibitors action. Outcome of the assay is represented as the value of platelet reactivity index (PRI), where PRI values above 50% are considered inadequate response to treatment and signal exposure to increased risk of myocardial infarction, post-PCI stent thrombosis and cardiac death. VASP-P flow cytometric assay is emerging into the spotlight as the promising method, mostly for its specificity for ADP inhibitors, better outlook for standardising results and lesser sample manipulation compared to multiple electrode aggregometry.