High on-treatment platelet reactivity in patients with ischemic cerebrovascular disease: assessment of prevalence and stability over time using four platelet function tests

Review: Flow Diversion for the Treatment of Middle Cerebral Artery Aneurysms

The invention of flow diverting stents (FDS) is a novel milestone in the field of endovascular aneurysm therapy, promoting physiological healing of the vessel segment contrary to prior deconstructive treatment strategies, such as coiling. The effects of FDS are based on changes in flow patterns, segmental wall stabilization, and the growth of a neointima. Although flow diversion is already well established for cerebral aneurysms in proximal segments, peripheral locations remain challenging. Especially the middle cerebral artery (MCA) with its predominance of non-collateralized perforators and functional end arteries that supply the eloquent areas of the brain is of major concern.The literature was reviewed for flow diversion of the MCA and antiplatelet therapy.Resulting from the special anatomical characteristics of the MCA, FDS implantation in this territory is completely different from the proximal vessel segments. Still, flow diversion represents an effective endovascular strategy, especially in otherwise non-accessible or sufficiently treatable lesions. However, the risk of ischemic adverse events might be increased. Special attention to the individual decision regarding device selection, antiplatelet regimen, and exact definition of the proximal and distal landing zone considering the jailed side branches is essential for a good angiographic and clinical outcome. · MCA aneurysms can be sufficiently treated by FDS.. · The anatomic and hemodynamic characteristics of the MCA result in an increased risk of thromboembolism.. · Individual device selection and antiplatelet regimen are essential for treatment success.. · Schüngel M, Wohlgemuth WA, Elolf E et al. Review: Flow Diversion for the Treatment of Middle Cerebral Artery Aneurysms. Fortschr Röntgenstr 2024; DOI 10.1055/a-2343-0046.

Antithrombotic and prohemorrhagic actions of different concentrations of apixaban in patients exposed to single and dual antiplatelet regimens

We evaluated modifications in the hemostatic balance of different concentrations of apixaban (APIX) in 25 healthy donors and 53 patients treated with aspirin (ASA, n = 21), ASA and clopidogrel (ASA + CLOPI, n = 11), or ASA and ticagrelor (ASA + TICA, n = 21). Blood samples from participants were spiked ex vivo with apixaban 0 (APIX0), 40 (APIX40), and 160 ng/mL (APIX160). We assessed the effects of APIX on (1) clot formation, by ROTEM thromboelastometry; (2) thrombin generation primed by platelets; and (3) platelet and fibrin interactions with a thrombogenic surface, in a microfluidic model with circulating blood. APIX caused dose-related prolongations of clotting time with minimal impact on other ROTEM parameters. Thrombin generation was significantly inhibited by APIX160, with ASA + TICA actions showing the strongest inhibition (p < 0.01 vs APIX0). Microfluidic studies showed that APIX160 was more potent at suppressing platelet and fibrin interactions (p < 0.001 vs. APIX0). APIX40 demonstrated a consistent antithrombotic action but with a favorable protective effect on the structural quality of fibrin. APIX potentiated the antithrombotic effects of current antiplatelet regimens. APIX at 40 ng/mL, enhanced the antithrombotic action of single or dual antiplatelet regimens but was more conservative for hemostasis than the 160 ng/mL concentration.

A Systematic Review of Clopidogrel Resistance in Vascular Surgery: Current Perspectives and Future Directions

BACKGROUND

Clopidogrel resistance is a well-described phenomenon that has been linked to adverse cardiovascular events in patients with coronary artery disease. The impact of clopidogrel resistance in patient outcomes after vascular and endovascular surgery is not well-established.

METHODS

Using preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, a literature review with the medical subject headings (MeSH) terms "(clopidogrel resistance) and (vascular)", "(clopidogrel resistance) and (vascular surgery)", "(clopidogrel resistance) and (endovascular)", and "(clopidogrel resistance) and (endovascular surgery)" was performed in PubMed and Cochrane databases, to identify all peer-reviewed studies performed on clopidogrel resistance in vascular and endovascular surgery. Studies written in the English language from inception to 2022 were included. Case reports, studies with limited information, nonhuman studies, and studies not pertaining to vascular or endovascular surgery were excluded from analysis. Each study was independently reviewed by 2 qualified researchers to assess eligibility.

RESULTS

Of the 691 studies identified through the MeSH strategy, 16 studies met the inclusion criteria and were reviewed and summarized. These studies focused on extracranial cerebrovascular disease (n = 5) and peripheral arterial disease (PAD, n = 11), encompassing a total of 1,716 patients. The prevalence of clopidogrel resistance ranged from 0% to 83.3%, depending on the diagnostic assay and cutoff values used. In cerebrovascular disease, clopidogrel resistance may be associated with cerebral embolization, ischemic neurologic events, and vascular-related mortality. In PAD, clopidogrel resistance has been linked to recurrent stent thrombosis, target lesion revascularization, amputation-free survival, and all-cause mortality.

CONCLUSIONS

This systematic review provides an up-to-date summary of clopidogrel resistance in vascular and endovascular surgery. The impact of clopidogrel resistance remains incompletely investigated, and future studies are needed to clarify the role of resistance testing in patients with vascular disease.

Role of platelet function testing in acute coronary syndromes: a meta-analysis

OBJECTIVE

This meta-analysis aimed to evaluate whether using platelet function testing (PFT) in acute coronary syndromes (ACS) to personalise antiplatelet therapy including a P2Y₁₂ antagonist offers any clinical benefits to indicate incorporation into routine practice.

METHODS

A search was conducted on five databases for randomised controlled trials (RCTs) conducted between 1 January 2000 and 17 July 2022, which included an ADP-specific platelet function assays and P2Y₁₂ antagonists as part of dual antiplatelet therapy (DAPT) and have reported the efficacy and/or safety outcomes. The reported event frequencies were used to calculate the risk ratios (RRs) with a 95% CI. The χ² heterogeneity statistical test and sensitivity analysis were used for heterogeneity assessment.

RESULTS

Five RCTs with 7691 patients were included in the analysis. No significant risk reduction was seen in major adverse cardiovascular events (RR=0.95, p=0.42), individual cardiac events (cardiovascular death: RR=0.76, p=0.26; myocardial infarction: RR=0.96, p=0.74; stent thrombosis: RR=0.92, p=0.83; stroke: RR=0.91, p=0.72; target vessel revascularisation: RR=1.06, p=0.47) and overall clinical outcome (RR=0.90, p=0.22). There was also no difference in the rate of bleeding between PFT-guided and standard therapies (major bleeding: RR=0.97, p=0.78, minor bleeding: RR=0.89, p=0.19 and any bleeding: RR=1.04, p=0.33).

CONCLUSION

Compared with standard DAPT with P2Y₁₂ antagonists, using PFT to adjust antiplatelet therapy does not improve clinical outcomes. Therefore, the positions of key guidelines on routine testing in ACS should remain unchanged. In addition, the study highlights the need for well-designed and powered RCTs and standardised testing methodologies to provide reliable findings and definitive conclusions.

Advanced pharmacodynamics of cangrelor in healthy volunteers: a dose-finding, open-label, pilot trial

Background

High on-treatment platelet reactivity (HTPR) remains a major problem in the acute management of ST-elevation myocardial infarction (STEMI), leading to higher rates of stent thrombosis and mortality. We aimed to investigate a novel, prehospital treatment strategy using cangrelor and tested its pharmacodynamic effects in a model using healthy volunteers.

Methods

We conducted a dose-finding, open-label, pilot trial including 12 healthy volunteers and tested three ascending bolus infusions of cangrelor (5 mg, 10 mg and 20 mg) and a bolus infusion followed by a continuous infusion via an intravenous (IV) flow regulator. Platelet function was assessed using multiple electrode aggregometry (MEA), vasodilator-stimulated phosphoprotein phosphorylation assay (VASP-P) and the platelet function analyzer. In an ex vivo experiment, epinephrine was used to counteract the antiplatelet effect of cangrelor.

Results

All cangrelor bolus infusions resulted in immediate and pronounced platelet inhibition. Bolus infusions of cangrelor 20 mg resulted in sufficient platelet inhibition assessed by MEA for 20 min in 90% of subjects. Infusion of cangrelor via the IV flow regulator resulted in sufficient platelet inhibition throughout the course of administration. Ex vivo epinephrine, in concentrations of 200 and 500 ng/mL was able to partially reverse the antiplatelet effect of cangrelor in a dose-dependent manner.

Conclusions

Weight-adapted bolus infusions followed by a continuous infusion of cangrelor via IV flow regulator result in immediate and pronounced platelet inhibition in healthy subjects. Cangrelor given as weight-adapted bolus infusion followed by a continuous infusion using an IV flow regulator may be a viable treatment approach for effective and well controllable prehospital platelet inhibition.

Trial registration

EC (Medical University of Vienna) 1835/2019 and EudraCT 2019-002792-34.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-022-00377-z.

Multifactorial Background for a Low Biological Response to Antiplatelet Agents Used in Stroke Prevention

Effective platelet inhibition is the main goal of the antiplatelet therapy recommended as a standard treatment in the secondary prevention of non-embolic ischemic stroke. Acetylsalicylic acid (aspirin) and clopidogrel are commonly used for this purpose worldwide. A low biological response to antiplatelet agents is a phenomenon that significantly reduces the therapeutic and protective properties of the therapy. The mechanisms leading to high on-treatment platelet reactivity are still unclear and remain multifactorial. The aim of the current review is to establish the background of resistance to antiplatelet agents commonly used in the secondary prevention of ischemic stroke and to explain the possible mechanisms. The most important factors influencing the incidence of a low biological response were demonstrated. The similarities and the differences in resistance to both drugs are emphasized, which may facilitate the selection of the appropriate antiplatelet agent in relation to specific clinical conditions and comorbidities. Despite the lack of indications for the routine assessment of platelet reactivity in stroke subjects, this should be performed in selected patients from the high-risk group. Increasing the detectability of low antiaggregant responders, in light of its negative impact on the prognosis and clinical outcomes, can contribute to a more individualized approach and modification of the antiplatelet therapy to maximize the therapeutic effect in the secondary prevention of stroke.

The Phenomenon of Clopidogrel High On-Treatment Platelet Reactivity in Ischemic Stroke Subjects: A Comprehensive Review

Clopidogrel is increasingly being used for the secondary prevention of ischemic stroke according to the updated guidelines on acute stroke management. Failure to achieve a drug response is referred to as clopidogrel resistance. Similarly, a higher activation of platelets during clopidogrel therapy—high on-treatment platelet reactivity—is equivalent to a reduced effectiveness of a therapy. Clopidogrel resistance is considered to be a common and multifactorial phenomenon that significantly limits the efficacy of antiplatelet agents. The aim of the current study is to review the latest literature data to identify the prevalance and predictors of clopidogrel high on-treatment platelet reactivity among stroke subjects and to establish the potential impact on clinical outcomes and prognosis. Clinical databases were searched by two independent researchers to select relevant papers on the topic, including all types of articles. Several important predictors contributing to clopidogrel resistance were identified, including genetic polymorphisms, the concomitant use of other drugs, or vascular risk factors, in particular nonsmoking and diabetes. Clopidogrel high on-treatment platelet reactivity has a negative impact on the clinical course of stroke, worsens the early- and long-term prognoses, and increases the risk of recurrent vascular events. Platelet function testing should be considered in selected stroke individuals, especially those predisposed to clopidogrel resistance, for whom an improvement in the efficacy of antiplatelet therapy is essential. This particular group may become the greatest beneficiaries of the modification of existing therapy based on platelet function monitoring.

Platelet Reactivity in Patients on Aspirin and Clopidogrel Therapy Measured by a New Bedside Whole-Blood Assay

Various tests are available for measuring on-treatment platelet reactivity. The pharmacologically most specific assays are time-consuming and elaborate. A highly specific and convenient assay would be desirable for clinical routine. In this pilot study, we aimed to examine the ability of a novel bedside whole-blood assay-ROTEM platelet-to evaluate platelet inhibition compared with established assays. Platelet reactivity was investigated in 93 patients. Forty-Seven patients were on permanent aspirin therapy and 46 on dual antiplatelet therapy (DAPT) with aspirin and clopidogrel. We used ROTEM platelet impedance aggregometry (ROTEM-PTL), light transmission aggregometry (LTA), Multiplate electrode aggregometry (MEA) and vasodilator-stimulated phosphoprotein flow cytometry. Receiver operating characteristic (ROC) analyses showed ROTEM-PTL differentiates well between patients on medication and healthy individuals: aspirin: ROCAUC 0.99 (95% confidence interval, 0.97-1.01); P < 0.0001; DAPT treatment: ROCAUC 0.80 (95% confidence interval, 0.69-0.91); P < 0.001. Pearson regression analyses showed moderate correlations between assays. Aspirin: MEA versus ROTEM-PTL r = 0.435, P ≤ 0.001; LTA versus ROTEM-PTL r = 0.048, P = 0.180. DAPT: MEA versus ROTEM-PTL r = 0.398, P = 0.001; LTA versus ROTEM-PTL r = 0.409, P = 0.001; vasodilator-stimulated phosphoprotein versus ROTEM-PTL r = 0.164, P = 0.055. ROTEM platelet distinguished well between treated and healthy individuals but correlated moderately with other assays. Clinical trials are needed to investigate the ability of this new assay to identify patients at risk of adverse events.

The Influence of Inflammation on Fibrinogen Turnover and Redistribution of the Hemostatic Balance to a Prothrombotic State in High On-Treatment Platelet Reactivity-Dual Poor Responder (HTPR-DPR) Patients

Knowledge about the influence of inflammation on platelet function and relocation of hemostatic balance to hypercoagulable state is still unclear. We compared two groups of patients who suffer from acute vs. chronic inflammatory process and additionally present high on-treatment platelet reactivity-dual platelet resistance. We did not found any differences in platelet aggregation between both investigated groups, but patients who suffer from chronic inflammation presented stronger relocation of the hemostatic balance to the hypercoagulability. A high concentration of prothrombin fragment F1+2 together with higher activity of von Willebrand factor in critical limb ischemia shows more exaggerated fibrinogen turnover although the blood concentration of this factor was in normal range. We concluded that high on-treatment platelet reactivity-dual platelet resistance and intensified inflammation are linked with elevated platelet and fibrinogen turnover to counteract proper hemostatic balance in favor of a prothrombotic state.

[A comparative assessment of indicators of platelet aggregation and interleukins in patients with different outcomes of ischemic stroke]

AIM

To compare indicators of platelet aggregation (PA) and the level of interleukins IL-1β, IL-4, IL-6, IL-18 in patients with ischemic stroke (IS).

MATERIAL AND METHODS

A prospective clinical cohort study involved 108 IS patients classified into group 1 (survivors) and group 2 (fatal outcomes). The studies were conducted in the most acute and acute phases of IS. The level of interleukins was measured by enzyme immunoassay method. PA was evaluated by the nephelometric method.

RESULTS AND CONCLUSION

PA, IL-1β and IL-6 indicators in the most acute phase of IS were significantly higher in the 2^nd group compared to the 1^st group. In the 1^st group, there was a reduction in the levels of IL-1β and IL-6, and an increase in the level of IL-4 in the acute phase compared to the most acute period of IS, whereas patients of the 2^nd group showed further increase in IL-1β and IL-6, and reduction of IL-4 levels. In surviving acute IS patients, the reduction in PA and the level of pro-inflammatory interleukins IL-1b, IL-6 and IL-18, and the increase in the level of anti-inflammatory interleukin IL-4 were accompanied with improvements in the clinical condition, whereas the negative dynamics of the aforementioned indicators was recorded in deceased patients.

Platelet Aggregation and Interleukins Indicators Impacting the Outcomes of Ischemic Stroke

AIM

Relative assessment and relationship between of platelet aggregation and the level of interleukins IL-1β, IL-4, IL-6, and IL-18 among ischemic stroke (IS) patients.

METHODS

A prospective clinical cohort study involved 108 IS patients, classified into group 1-surviving (93; 86.1%) and group 2-lethal outcomes (15; 13.9%). The studies were conducted in the most acute (first day of hospitalization) and acute (7 days of hospitalization) phases of IS. The level of interleukins was defined by enzyme immunoassay method. The platelet aggregation research was performed by the nephelometric method.

RESULTS

In the acute phase of the IS the first group, patients showed reduction in the level of IL-1β and IL-6, and increase in the level of IL-4, compared to the most acute period, whereas in patients of the second group further increase in IL-1β and IL-6, and reduction of IL-4 levels were recorded. Both in the most acute and acute phases of the IS, in parallel to the aggravation of platelet aggregation (PA) disturbances, the lethal outcome probability grew. The latter also grew together with increase in the synthesis of IL-1β and IL-6, in the most acute phase of the IS. In the acute phase of the IS, lethal outcome was recorded in all patients with high values of IL-1β and IL-6, and all patients with low values of IL-1β showed improvement.

CONCLUSIONS

Vivid disturbances of PA, IL-1β, IL-6, and IL-18 synthesis, in the most acute phase of the IS, signal higher probability of lethal outcome. Reduction in the levels of IL-1β, IL-6, and IL-18, and increase of IL-4 in the acute phase, means improvement in conditions.

Assessment of a flow cytometry technique for studying signaling pathways in platelets: Monitoring of VASP phosphorylation in clinical samples

A recently released kit (PerFix EXPOSE) was reported to improve the measurement of the degree of phosphorylation of proteins in leukocytes by flow cytometry. We tested its adaptation for platelets to monitor vasodilator-stimulated phosphoprotein (VASP) phosphorylation, which is the basis of a currently used test for the assessment of the pharmacological response to P2Y12 antagonists (PLT VASP/P2Y12). The PerFix EXPOSE kit was compared to the PLT VASP/P2Y12 kit by using blood samples drawn at 24 h post clopidogrel dose from 19 patients hospitalized for a non-cardio-embolic ischemic stroke and treated with clopidogrel monotherapy for at least five days in an observational study. The platelet PerFix method was based on adaptation of the volume of the sample, the centrifugation speed and the incubation temperature. Poor agreement between prevention by adenosine diphosphate (ADP) of PGE₁-induced cAMP-mediated VASP phosphorylation and ADP induced aggregation assessed by Light Transmittance Aggregometry was found. We found a significant correlation between the PLT VASP/P2Y12 kit and the PerFix EXPOSE kit. The PerFix EXPOSE kit may also be helpful to monitor adverse effects of second-generation tyrosine kinase inhibitors on platelets.

[Prognostic significance of indices of platelets aggregation and interleukin-1β in the acute period of ischemic stroke]

AIM

To determine the prognostic significance of indices of platelet aggregation (PA) and the level of interleukin IL-1β in the outcome of ischemic stroke (IS).

MATERIAL AND METHODS

One hundred and eight patients were studied. According to disease outcome, two groups of patients were identified: survivors (group 1) and patients with fatal outcome (group 2). Patients were examined in the very early stage (the 1^st day of hospitalization) and in the early stage (the 7^th day of hospitalization) of IS. The level of interleukin IL-1β in blood serum was defined by enzyme immunoassay method. PA was measured by nephelometric method.

RESULTS AND CONCLUSION

According to PA indices, a posteriori prognosis of fatal outcome was 10%, but according to IL-1β indices, it was 0.90%. Consequently, the prognostic significance of PA indices with regard to fatal outcome of IS patients in the acute period is higher than that of IL-1b indices. Taking into consideration the expenses of both methods of diagnosis, the authors conclude that with regard to economic availability, PA measurement as a prognostic-diagnostic method is more acceptable in clinical practice.

Predictive value of high residual platelet reactivity by flow cytometry for outcomes of ischemic stroke patients on clopidogrel therapy

High residual platelet reactivity (HRPR) assessed by multiple tests has been associated with worse clinical outcomes. However, the clinical impact of HRPR assessed by flow cytometry is unknown. The aim of this study was to validate the predictive value of HRPR measured by flow cytometry for clinical outcomes in ischemic stroke patients during clopidogrel therapy. Overall, 198 consecutive patients with ischemic stroke taking clopidogrel underwent platelet function testing on flow cytometer including adenosine diphosphate (ADP)-induced platelet aggregation (PAg) and platelet activation markers (CD62P, CD63, and PAC-1). Poor outcome was defined as poor prognosis and ischemic events during 12-month follow-up. By receiver operating characteristic curve analysis, residual platelet reactivity assessed by flow cytometry was able to distinguish between patients with and without poor outcomes, when platelet inhibition was evaluated with ADP-PAg (area under the curve [AUC], .77; 95% confidence interval [CI], .69-.84; P < .001), CD62P (AUC, .73; 95% CI, .64-.81; P < .001), CD63 (AUC, .72; 95% CI, .64-.80; P < .001), and PAC-1 (AUC, .70; 95% CI, .62-.78; P < .001). The prevalence of HRPR was 25.8% for ADP-PAg, 32.8% for CD62P, 41.4% for CD63, and 56.1% for PAC-1. The multiple logical regression analysis demonstrated that HRPR was an independent predictor of poor outcomes (ADP-PAg: odds ratio [OR] 13.03, 95% CI 5.66-29.98, P < .001; CD62P: OR 8.55, 95% CI 3.94-18.57, P < .001; CD63: OR 8.74, 95% CI 3.89-19.64, P < .001; PAC-1: OR 4.23, 95% CI 1.98-9.08). In conclusion, HRPR, assessed by flow cytometry, is able to detect ischemic stroke patients at increased risk of 12-month poor outcomes on clopidogrel treatment.