Antiplatelet Effect of Aspirin in Ischemic Stroke: A Hospital-based Study

Introduction: Aspirin is widely used for the treatment of stroke. Therefore aspirin resistance can lead to a significant increase in the burden of stroke. Platelet aggregation studies can evaluate platelet function, and this may help to detect anti-platelet resistance. Methods: This is a hospital-based study of the antiplatelet effect of aspirin in ischemic stroke, during a duration of one year. All first-time ischemic stroke patients >18 years of age were included. Platelet aggregometry test was done by LTA (Light transmission optical aggregometer), after starting the patients on oral aspirin. Results: A total of 113 ischemic stroke patients were included for the antiplatelet effect of the aspirin study. Aspirin resistance was found in 18.58% of patients. Patients with aspirin resistance had higher mortality, and less improvement on follow-up, as compared to aspirin-sensitive patients. They had more incidence of smoking, alcohol abuse, diabetes mellitus, and dyslipidemia, as compared to the aspirin-sensitive group. The results reveal that there is a non-statistically significant trend in both mortality and prognosis between the two study groups compared: aspirin-resistant versus aspirin-sensitive patients. Conclusion: Aspirin resistance can lead to loss of functional improvement and more mortality than aspirin-sensitive patients. However, further study for drug interactions, adequate risk factor control, the genetic profile of the population is needed, to come to a definite conclusion.

Protease-Activated Receptor-Mediated Platelet Aggregation In Patients With Type 2 Diabetes On Potent P2Y12 Inhibitors

Background: Dual antiplatelet therapy is a cornerstone in the secondary prevention of ischemic events following percutaneous coronary intervention (PCI) with stent implantation. The new, more potent adenosine diphosphate (ADP) P2Y12 receptor inhibitors prasugrel and ticagrelor have been shown to improve patients’ outcomes. Whether or not these drugs have equal efficacy in diabetic as in non-diabetic individuals is disputed. Furthermore, platelets can be activated by thrombin, which is, at least in part, independent of ADP-inducible activation. Protease-activated receptor (PAR)-1 and -4 are thrombin receptors on human platelets activated by the agonists SFLLRN and AYPGKF, respectively. In the current study, we sought to compare the in vitro efficacy of prasugrel (n=121) and ticagrelor (n=99) to inhibit PAR-mediated platelet activation in patients with type 2 diabetes (n=55).Materials and Methods: We compared P2Y12-, PAR-1- and PAR-4-mediated platelet aggregation as assessed by multiple electrode platelet aggregometry between prasugrel- and ticagrelor-treated patients without and with type 2 diabetes who underwent acute PCI. Results: There were no significant differences of on-treatment platelet aggregation in response to ADP, SFLLRN and AYPGKF between patients on prasugrel or on ticagrelor. Diabetic and non-diabetic patients responded equally. There was no significant correlation between either; ADP-, SFLLRN-, or AYPGKF-inducible platelet aggregation and levels of HbA1c or the body mass index. However, we observed patients with high residual platelet reactivity to SFLLRN and AYPGKF in all cohorts.Conclusion: Prasugrel and ticagrelor inhibit platelet aggregation in diabetic and non-diabetic patients to a similar extent.

Why Me? To Be an Ultra-Responder to Antiplatelet Therapy: A Case Report

Background: Platelet function testing is a valid tool to investigate the clinical response to antiplatelet therapy in different clinical settings; in particular, it might supply helpful information in patients with cerebrovascular disease. Oral antiplatelet treatment, such as Aspirin (ASA) and Clopidogrel, is the gold standard in secondary stroke prevention of non-cardiogenic ischemic stroke; conversely, its application as a primary prevention therapy is not routinely recommended in patients with vascular risk factors. Multiple electrode platelet aggregometry (MEA) impedance aggregometer is a validated device to test platelet inhibition induced by ASA or Clopidogrel.Case Report: We report the case of a 78-year-old patient without relevant clinical history, taking ASA as primary prevention strategy, who was admitted for sudden onset of dysarthria and left facial hyposthenia during physical effort. Brain CT revealed two small subcortical bilateral spontaneous intracranial hemorrhages. Platelet aggregometry with MEA performed upon admission revealed a very strong platelet inhibition induced by ASA (result of the ASPI Test was 5 U, consistent with an ultra-responsiveness to ASA, and the cutoff value of correct responsiveness is <40 U). MRI at longitudinal follow-up revealed the presence of two small cavernous angioma underlying hemorrhagic spots.Conclusion: The evaluation of platelet reactivity in stroke patients undergoing antiplatelet therapies, not commonly performed in clinical practice, could be useful to optimize prevention strategies; the verification of the biological effectiveness of ASA or Clopidogrel could be a valid tool in the definition of each patient's risk profile, particularly in patients with cerebrovascular disease known to be at increased risk for both hemorrhagic and thrombotic complications.

Mild Therapeutic Hypothermia Alters Hemostasis in ST Elevation Myocardial Infarction Patients

Background and Rationale: Mild therapeutic hypothermia (MTH) is a concept to reduce infarct size and improve outcome after ST-segment elevation myocardial infarction (STEMI). In the STATIM trial, we investigated MTH as an additional therapy for STEMI patients. In the intention-to-treat set, 101 patients were included. No difference in primary and secondary endpoints measured by cardiac magnetic resonance imaging was found. Platelet activation and plasmatic coagulation are key in the pathophysiology of STEMI. In the present study, we investigated the effect of MTH on primary and secondary hemostasis in STEMI patients.Methods and Results: Platelet function and morphology were assessed by routine blood count, aggregometry testing, and flow cytometry. Soluble platelet markers were determined by enzyme-linked immunosorbent assay (ELISA) testing. Plasmatic coagulation was measured throughout the study. Platelet count remained unchanged, irrespective of treatment, whereas platelet size decreased in both patient groups. Platelet aggregometry indicated increased platelet reactivity in the MTH group. Furthermore, higher adenosine diphosphate (ADP) plasma levels were found in MTH patients. Expression of glycoprotein IIb/IIIa was increased on platelets of STEMI patients treated with MTH. Lower patient temperatures correlated with longer clotting times and resulted in reduced pH. Lower pH values were positively correlated with longer clotting times.Conclusion: Present data indicate longer clotting times and higher platelet reactivity in STEMI patients treated with MTH. These changes did not correspond to clinical bleeding events or larger infarct size.

Determination of reference ranges for automated platelet aggregometry on Sysmex CS‑5100 analyzer

Measurement of platelet function by light transmission aggregometry (LTA) using a special device – an aggregometer requires significant time and is time-consuming. In this study, an automated LTA procedure was evaluated to establish the reference ranges. On the Sysmex CS-5100 analyzer, aggregation measurements were performed using several agonists at a certain concentration: ADP (2 µmol/L); arachidonic acid (1 mmol/L); collagen (2 µg/ml); ristocetin (1.2 mg/ml); epinephrine (5 µmol/L). For each agonist, the maximum and final aggregation, the Lag phase and the Area under the aggregation curve were measured. Reference ranges for a standard panel of activators were determined on 40 samples of healthy subjects in the concentrations recommended by the International Society on Thrombosis and Haemostasis. A standard panel of agonists can be used on Sysmex CS series analyzers: ADP, arachidonic acid; collagen; ristocetin, epinephrine, so these devices can replace specialized aggregometers or perform platelet aggregation where this investigation is not currently performed.

A genetic polymorphism in P2RY1 impacts response to clopidogrel in cats with hypertrophic cardiomyopathy

Clopidogrel is converted to its active metabolite by cytochrome P450 isoenzymes and irreversibly inhibits platelet activation by antagonizing the adenosine-diphosphate (ADP) receptor. It is frequently used in cats with hypertrophic cardiomyopathy (HCM) to prevent thromboembolic complications. However, significant interpatient variability of the response to clopidogrel therapy has been suspected. In this study, we assessed the impact of single nucleotide polymorphisms (SNPs) within ADP receptor (P2RY1, P2RY12) and cytochrome P450 isoenzyme (CYP2C41) genes on platelet inhibition by clopidogrel administration in cats with HCM. Forty-nine cats completed the study, and blood samples were obtained before and after clopidogrel therapy to assess the degree of platelet inhibition based on flow cytometry and whole blood platelet aggregometry. Plasma concentrations of clopidogrel metabolites were measured after the last dose of clopidogrel. Whole blood platelet aggregometry revealed a significant reduction of platelet inhibition by clopidogrel in cats with the P2RY1:A236G and the P2RY12:V34I variants. The association with the P2RY1:A236G variant and clopidogrel resistance remained significant after adjustment for multiple comparisons. This study demonstrated that a genetic polymorphism in the P2RY1 gene altered response to clopidogrel therapy and suggests that clinicians may consider alternative or additional thromboprophylactic therapy in cats with the P2RY1:A236G variant.

Hypercoagulopathy, acquired coagulation disorders and anticoagulation before, during and after extracorporeal membrane oxygenation in COVID-19: a case series

Background: Thromboembolism and bleeding contribute to Coronavirus disease 2019 (COVID-19)’s morbidity and mortality and are also frequent complications of venovenous extracorporeal membrane oxygenation (vvECMO). As the interaction of the underlying pathologies caused by vvECMO in COVID-19 is barely understood, we designed this study to better differentiate coagulation disorders in COVID-19 patients before, during and after vvECMO-support. Methods: Observational case series, six consecutive patients with Coronavirus acute respiratory distress syndrome supported with vvECMO treated in the anaesthesiologic ICU in a third level University ECMO-centre. We measured routine coagulation parameters and assessed coagulation factors. We also conducted advanced von Willebrand factor (VWF) multimer analysis, platelet aggregometry and immunological screening. Results: We identified various phases of coagulation disorders: Initially, intensely activated coagulation with highly increased VWF and factor VIII activity in acute COVID-19, then severe acquired von Willebrand syndrome and platelet dysfunction during vvECMO leading to spontaneous bleeding and finally, hypercoagulopathy after vvECMO explantation. Five of six patients developed immunological abnormalities enhancing coagulation. Conclusions: Coronavirus-induced coagulopathy and bleeding disorders during vvECMO cannot be discriminated via ‘routine’ coagulation tests. Precise and specific analyses followed by the appropriate treatment of coagulation disorders may help us develop tailored therapeutic concepts to better manage the phases described above.

Genetic Polymorphisms Impact Response to Clopidogrel in Feline Hypertrophic Cardiomyopathy

Clopidogrel is converted to its active metabolite by cytochrome P450 isoenzymes and irreversibly inhibits platelet activation by antagonizing the adenosine-diphosphate (ADP) receptor. It is frequently used in cats with hypertrophic cardiomyopathy (HCM) to prevent thromboembolic complications. However, significant interpatient variability of the response to clopidogrel therapy has been suspected. In this study, we assessed the impact of single nucleotide polymorphisms (SNPs) within ADP receptor (P2RY1, P2RY12) and cytochrome P450 isoenzyme (CYP2C41) genes on platelet inhibition by clopidogrel administration in cats with HCM. Forty-nine cats completed the study, and blood samples were obtained before and after clopidogrel therapy to assess the degree of platelet inhibition based on flow cytometry and whole blood platelet aggregometry. Plasma concentrations of clopidogrel metabolites were measured after the last dose of clopidogrel. Whole blood platelet aggregometry revealed a significant reduction of platelet inhibition by clopidogrel in cats with the P2RY1:A236G and the P2RY12:V34I variants. The association with the P2RY1:A236G variant and clopidogrel resistance remained significant after adjustment for multiple comparisons. This study demonstrated that a genetic polymorphism in the P2RY1 gene altered response to clopidogrel therapy and suggests that clinicians may consider alternative or additional thromboprophylactic therapy in cats with the P2RY:A236G variant.