Factors influencing Multiplate whole blood Impedance Platelet Aggregometry measurements, during aspirin treatment in acute ischemic stroke: a pilot study

Monitoring antiplatelet therapy: where are we now?

Single antiplatelet therapy represents the cornerstone of thrombosis prevention in atherosclerotic cardiovascular disease. Dual antiplatelet therapy (DAPT), consisting of aspirin plus a P2Y 12 inhibitor, is the standard of care for patients with acute coronary syndrome or undergoing both coronary and peripheral percutaneous interventions. Recent data suggest the efficacy of DAPT also after minor stroke. In this setting, a large body of evidence has documented that genetic and acquired patients' characteristics may affect the magnitude of platelet inhibition induced by antiplatelet agents. The implementation of tools allowing the identification and prediction of platelet inhibition has recently been shown to improve outcomes, leading to an optimal balance between antithrombotic efficacy and bleeding risk. We are therefore clearly moving towards tailored antiplatelet therapy. The aim of this paper is to summarize the available evidence on the evaluation of platelet inhibition in patients with coronary, peripheral, or cerebrovascular atherosclerosis. We will here focus on antiplatelet therapy based on both aspirin and P2Y 12 inhibitors. In addition, we provide practical insights into the clinical settings in which it appears reasonable to implement antiplatelet therapy monitoring.

Factors Associated with Aspirin Resistance in Hong Kong Chinese Patients with Stable Coronary Heart Disease Using the Multiplate® Analyzer and Serum Thromboxane B2

Introduction: Aspirin resistance may be associated with various conditions. We measured serum thromboxane B2 (TXB2) and platelet function using the Multiplate® Analyzer with arachidonic acid (ASPI) in patients on long term aspirin therapy to identify aspirin resistance and associated factors. Materials and Methods: Chinese patients with stable coronary heart disease had samples for serum TXB2 and ASPI measurement taken before and 1 h after taking a morning dose of 80 mg aspirin. Results: In 266 patients with mean age 66.6 ± 10.7 years, 17% were female and 55% were current or previous smokers. TXB2 and ASPI measurements were significantly higher before the dose than at 1 h post dose, with 46% of subjects having high ASPI values (AUC > 300 AU*min) pre dose compared with 27% at 1 h post dose. TXB2 and ASPI measures of platelet aggregation showed weak correlations, which were only significant before the dose (r = 0.219, p = 0.001). Increased ASPI measurements were associated with white blood cell (WBC) count, haematocrit, platelet count and heart rate at 24 h post dose but only with WBC count, smoking history and heart rate at 1 h post dose. Diabetes was not associated with reduced platelet response to aspirin. The WBC count associated with aspirin resistance was over 6.55 × 109/L by receiver operating characteristic analysis. Conclusions: The antiplatelet response to aspirin was reduced in a large proportion of patients. Patients with higher WBC count within the normal range appear to be at increased risk of aspirin resistance. Higher or more frequent doses of aspirin may be needed in many patients.

The Importance of Platelets Response during Antiplatelet Treatment after Ischemic Stroke-Between Benefit and Risk: A Systematic Review

Ischemic stroke is a disease related to abnormal blood flow that leads to brain dysfunction. The early and late phases of the disease are distinguished. A distinction is made between the early and late stages of the disease, and the best effect in treating an ischemic stroke is usually achieved within the first hours after the onset of symptoms. This review looked at studies platelet activity monitoring studies to determine the risks and benefits of various approaches including antiplatelet therapy. A study was conducted on recently published literature based on PRISMA. This review includes 32 research articles directly addressing the importance of monitoring platelet function during antiplatelet therapy (dual or monotherapy) after ischemic stroke. In patients with transient ischemic attack or ischemic stroke, antiplatelet therapy can reduce the risk of stroke by 11–15%, assuming that patients respond well. Secondary prevention results are dependent on platelet reactivity, meaning that patients do not respond equally to antiplatelet therapy. It is very important that aspirin-resistant patients can benefit from the use of dual antiplatelet therapy. The individualized approach to secondary stroke prevention is to administer the most appropriate drug at the correct dose and apply the optimal therapeutic procedure to the individual patient.

The Effect of Enhanced External Counterpulsation on Platelet Aggregation in Patients with Coronary Heart Disease

BACKGROUND

Resistance to antiplatelet therapy, especially aspirin or clopidogrel, triggers other therapies for patients with coronary heart disease (CHD). Enhanced external counterpulsation (EECP) is a noninvasive, pneumatic technique that provides beneficial effects for patients with CHD. However, the physiological effects of EECP have not been fully studied, and the role of EECP on platelet function remains poorly understood.

METHODS

A total of 168 patients with CHD were finally selected from the Second Xiangya Hospital and randomly assigned to either a control group or EECP group. The control group accepted only standard medical treatment, while the EECP group accepted standard medical treatment and EECP treatment. Blood samples were collected from patients at baseline and after EECP, and platelet aggregation was assessed. Changes in platelet aggregation were compared before and after treatment.

RESULTS

There was no difference in the basal levels of arachidonic acid (AA) induced platelet maximum aggregation ratio (MAR) between the two groups. The AA-induced platelet MAR was significantly decreased after EECP therapy. The logistic analysis showed that low HDL-C was not favorable for the decrease in platelet aggregation.

CONCLUSION

EECP therapy is favorable for lowering platelet aggregation in patients with CHD, especially the AA-induced platelet aggregation ratio.

Higher neutrophil-to-lymphocyte ratio (NLR) increases the risk of suboptimal platelet inhibition and major cardiovascular ischemic events among ACS patients receiving dual antiplatelet therapy with ticagrelor

BACKGROUND

Neutrophil to lymphocyte ratio (NLR) has emerged as a useful and easy-to-assess prognostic tool and biomarker of cardiovascular risk. However, few studies have evaluated its role on platelet inhibition among patients on dual antiplatelet therapy (DAPT), and especially in the settings of acute coronary syndromes (ACS). We aimed at assessing the impact of NLR on platelet reactivity and the risk of major ischemic events at long-term follow-up among ACS patients on DAPT with ticagrelor.

METHODS

Patients on dual antiplatelet therapy with ASA + ticagrelor (90 mg/twice a day) after percutaneous coronary revascularization for ACS were scheduled for platelet function assessment 30-90 days post-discharge. Aggregation tests were performed by Multiple Electrode Aggregometry (MEA). Suboptimal platelet inhibition (HRPR-high residual platelet reactivity was defined if above the lower limit of normality (417 AU*min). The primary study endpoint was defined as the occurrence of major cardiovascular events (a composite of cardiovascular death, recurrent acute coronary syndrome, target vessel revascularization) at longest available follow-up.

RESULTS

We included 397 patients, that were divided according to NLR tertiles. Patients with higher NLR were older (p < .001), less frequently smokers (p = .03), with higher rates of renal failure (p = .001), previous bypass surgery (p = .05) and use of statins (p = .03) and diuretics (p = .01). Higher white blood cells count and C-reactive protein (p < .001) and lower haemoglobin (p = .001) were associated with NLR. Mean platelet reactivity and the prevalence of high platelet reactivity (HRPR) on ticagrelor were significantly associated to higher NLR tertiles values (7% vs 12% vs 14.3%, p = .04), with a significant relationship between NLR and platelet reactivity being confirmed for all the different activating stimuli. At a mean follow-up of 939 ± 581.4 days, 21.2% of the patients experienced the primary composite endpoint, with a trend for a higher risk of events across NLR tertiles (15.4% vs 24.2% vs 24.4%, p = .09), that became statistically significant after correction for baseline confounders (adjusted HR[95%CI] = 1.13[1.008-1.26], p = .036). Moreover, NLR was significantly associated to overall mortality and recurrent ACS (adjusted p = .008, p = .06 and p = .02 respectively).

CONCLUSIONS

In the present study we found that among ACS patients treated with ASA and ticagrelor after PCI, suboptimal platelet inhibition despite DAPT was significantly increased for higher values of Neutrophil-to-Lymphocyte Ratio. Moreover, mortality and the risk of recurrent major ischemic events at long-term were associated to NLR.

Homocysteine levels and platelet reactivity in coronary artery disease patients treated with ticagrelor

BACKGROUND AND AIM

Recurrent atherothrombotic events have been reported in certain higher risk subsets of patients even with ticagrelor, a potent first-line antiplatelet agent for the management of patients with acute coronary syndrome (ACS). Hyperhomocysteinemia is a known determinant of platelet function abnormalities. Therefore, the aim of our study was to evaluate the impact of homocysteine (Hcy) levels on platelet reactivity in patients receiving Ticagrelor.

METHODS AND RESULTS

Patients with ACS undergoing percutaneous coronary revascularization and on dual antiplatelet therapy with ASA + Ticagrelor (90mg/twice a day) were scheduled for platelet function assessment 30-90 days post-discharge. Aggregation tests were performed by Multiple Electrode Aggregometry (MEA). Suboptimal platelet inhibition HRPR-high residual platelet reactivity was defined if above the lower limit of normality (417 AU*min). We included 432 patients, divided according to Hcy tertiles. Higher Hcy levels were associated with age, renal failure, creatinine levels and use diuretics (p < 0.001). Patients with higher Hcy levels displayed a higher platelet reactivity at COL test (p = 0.002), and ADP test (p = 0.04), with a linear relationship between Hcy and platelet aggregation after stimulation with collagen (r = 0.202, p < 0.001), thrombin receptor peptide (r = 0.104, p = 0.05) and ADP (r = 0.145, p = 0.006). However, Hcy levels did not significantly affect the rate of HRPR with Ticagrelor (9.9% vs 13.7% vs 10.7%, p = 0.89; adjusted OR [95% CI] = [0.616-1.51], p = 0.99).

CONCLUSIONS

Among patients with ACS, despite the elevated platelet reactivity associated to hyperhomocysteinemia, DAPT with ticagrelor could overcome such phenomenon, achieving an adequate platelet inhibition in the majority of the patients.

Intake of aspirin prior to metamizole does not completely prevent high on treatment platelet reactivity

PURPOSE

Metamizole can sterically inhibit aspirin (ASA) from binding to cyclooxygenase 1 (COX1). It is recommended that ASA should be taken 30 min prior to metamizole to maintain the irreversible inhibition of arachidonic acid (AA)-induced platelet aggregation. We aimed to analyse the inhibitory effect of ASA and metamizole on AA-induced platelet aggregation over the course of the day.

METHODS

We analysed hospitalized patients who ingested ASA at least 30 min prior to metamizole (recommended dosing group, n = 15), metamizole prior or simultaneously with ASA (not recommended dosing group, n = 16) and patients with unknown or mixed intake (mixed dosing group, n = 5). AA-induced light transmission (LTA) and impedance aggregometry (IA) were measured before, 1-2 and 5-6 h after the intake of ASA ± metamizole.

RESULTS

Maximum AA-induced LTA prior to the intake of ASA was significantly lower and the rate of high on treatment platelet reactivity (HTPR) higher in the recommended compared with the not recommended dosing group (19.6% vs. 46.9%, p = 0.011 and 4/15 vs. 12/16 patients, p = 0.017). There was no difference when IA was used. Maximum AA-induced LTA after the intake of ASA ± metamizole was lower in patients in the not recommended but not in the recommended dosing group. All patients with HTPR in the recommended dosing group had regular inhibition of AA-induced LTA after discontinuation of metamizole.

CONCLUSION

Co-medication of ASA and metamizole significantly influences platelet inhibition with variations during the day and can cause HTPR in patients taking ASA prior to metamizole or simultaneously.

Response to aspirin therapy in patients with myeloproliferative neoplasms depends on the platelet count

Patients with myeloproliferative neoplasms (MPN) are at an increased risk of thrombotic events even during antiplatelet therapy with aspirin. In the current study, we sought to investigate the association of the platelet count with the inhibitory potential of antiplatelet therapy in MPN. We determined arachidonic acid (AA)- and adenosine diphosphate (ADP)-inducible platelet reactivity by multiple electrode aggregometry in 93 patients with essential thrombocythemia, polycythemia vera or primary myelofibrosis. In patients without aspirin therapy (n = 44), the platelet count did not correlate with platelet aggregation. In aspirin-treated patients (n = 49), we observed a moderate correlation of residual AA-inducible platelet aggregation with the platelet count (r = 0.49; P < 0.001). Further, patients with high on-treatment residual platelet reactivity to AA (HRPR AA) had a significantly higher platelet count than patients without HRPR AA (547 × 10⁹/L [340 - 644 × 10⁹/L] vs 358 × 10⁹/L [242 - 501 × 10⁹/L], P = 0.01). Receiver-operating characteristic curve analysis revealed a platelet count of ≥317 × 10⁹/L as best threshold to distinguish between patients without and with HRPR AA (area under the curve: 0.73). After adding the direct ADP P2Y₁₂ inhibitor cangrelor to blood samples from all 93 patients in vitro, residual ADP-inducible platelet reactivity correlated weakly with the platelet count (r = 0.26, P = 0.01), but the platelet count did not differ significantly between patients with and without HRPR ADP (396 × 10⁹/L [316 - 644 × 10⁹/L] vs 340 × 10⁹/L [241 - 489 × 10⁹/L]; P = 0.2). In conclusion, our findings suggest that the extent of platelet inhibition by aspirin in patients with MPN at least in part depends on their individual platelet count.

High-sensitive C-reactive protein and dual antiplatelet in intracranial arterial stenosis

Objective

To determine the relationship of high-sensitive C-reactive protein (hsCRP) and the efficacy and safety of dual antiplatelet therapy in patients with and without intracranial arterial stenosis (ICAS) in the Clopidogrel in High-Risk Patients with Acute Non-disabling Cerebrovascular Events (CHANCE) trial.

Methods

A subgroup of 807 patients with both magnetic resonance angiography images and hsCRP measurement was analyzed. Cox proportional hazards models were used to assess the interaction of hsCRP levels with the effects of dual and single antiplatelet therapy.

Results

A total of 358 (44.4%) patients had ICAS and 449 (55.6%) did not. The proportion of patients with elevated hsCRP levels was higher in the ICAS group than in the non-ICAS group (40.2% vs 30.1%, p = 0.003). There was significant interaction between hsCRP and the 2 antiplatelet therapy groups in their effects on recurrent stroke after adjustment for confounding factors in the patients with ICAS (p = 0.012), but not in those without (p = 0.256). Compared with aspirin alone, clopidogrel plus aspirin significantly reduced the risk of recurrent stroke only in the patients with ICAS and nonelevated hsCRP levels (adjusted hazard ratio 0.27; 95% confidence interval 0.11 to 0.69; p = 0.006). Similar results were observed for composite vascular events. No significant difference in bleeding was found.

Conclusions

Presence of both ICAS and nonelevated hsCRP levels may predict better response to dual antiplatelet therapy in reducing new stroke and composite vascular events in minor stroke or high-risk TIA patients. Further large-scale randomized and controlled clinical trials are needed to confirm this finding.

Acetylsalicylic acid in critically ill patients: a cross-sectional and a randomized trial

BACKGROUND

Despite decades of clinical use, the pharmacokinetics and the effects of acetylsalicylic acid (ASA) in critically ill patients remain ill-defined. We aimed to investigate the pharmacokinetics and the effects of different ASA formulations during critical illness.

DESIGN

A cross-sectional study and a randomized, parallel-group trial were performed. Critically ill patients under chronic oral ASA treatment (100 mg enteric-coated) were screened for high 'on-treatment' platelet reactivity (HTPR) according to arachidonic acid-induced whole-blood aggregometry. Thirty patients with HTPR were randomized to receive 100 mg ASA intravenously, 100 mg enteric-coated ASA bid (bis in die) or 81 mg chewable ASA (n = 10 per group). Serum thromboxane B2 (TXB2) levels, ASA and salicylic acid levels were quantified.

RESULTS

Of 66 patients, 85% (95% confidence intervals 74-93%) had HTPR. Compared to baseline infusion of 100 mg, ASA significantly reduced platelet aggregation after 24 h to median 80% (Quartiles: 66-84%). Intake of 81 mg chewable ASA significantly reduced platelet aggregation to 75% (54-86%) after four hours, but increased it to 117% after 24 h (81-163%). Treatment with 100 mg enteric-coated ASA bid decreased platelet aggregation after 24 h to median 56% (52-113%). Baseline TXB2 levels were median 0·35 ng/mL (0·07-0·94). Infusion of ASA or intake of 100 mg ASA bid reduced TXB2 levels to 0·07-0·18 ng/mL after 24 h, respectively. Chewable ASA reduced TXB2 levels only transiently. Pharmacokinetic analysis revealed highly variable absorption patterns of oral ASA formulations.

CONCLUSION

There is a very high prevalence of HTPR in critically ill patients on peroral ASA therapy, caused by an incomplete suppression of TXB2 and/or by impaired absorption of ASA.

Homocysteine Levels Influence Platelet Reactivity in Coronary Artery Disease Patients Treated With Acetylsalicylic Acid

BACKGROUND

Suboptimal platelet inhibition with antiplatelet treatments is associated with a severe prognosis in patients with coronary artery disease (CAD), and the identification of its determinants is still challenging. Homocysteine elevation has emerged as a prothrombotic factor, influencing coagulative status and endothelial function and potentially modulating platelet aggregation. We therefore aimed to evaluate the effects of homocysteine (Hcy) levels on platelet reactivity in patients receiving acetylsalicylic acid (ASA) with or without ADP antagonists.

METHODS

Patients undergoing coronary angiography and receiving ASA (100-160 mg daily) for >7 days, with or without ADP antagonists, were included. Aggregation tests were performed by multiple electrode aggregometry. Suboptimal platelet inhibition was defined as on-treatment aggregation above the lower limit of normality.

RESULTS

Our population is represented by 508 ASA-treated patients, 406 (80.1%) of whom on dual antiplatelet therapy (ASA and ADP antagonists). Hcy levels above the median (15.1 nmol/mL) were associated with male gender (P = 0.04), hypertension (P = 0.004), hypercholesterolemia (P = 0.03), aging, renal failure (P < 0.001, respectively), previous coronary bypass grafting (P = 0.04), therapy with calcium antagonists (P = 0.04) and diuretics (P = 0.001), and multivessel CAD (P = 0.03). Higher Hcy is directly related with serum creatinine and uric acid (P < 0.001). Suboptimal platelet inhibition was found in 16 patients (3.2%) for ASA and for ADP antagonists in 80 patients (19.7%). Hcy levels significantly affected suboptimal response to ASA, but not to ADP-mediated aggregation. In fact, a linear relationship was found between homocysteine and platelet reactivity after stimulation with arachidonic acid (r = 0.14, P = 0.004) and collagen (r = 0.12, P = 0.02), but not with ADP (r = 0.02, P = 0.77). Moreover, after correction for baseline differences, Hcy above the median was confirmed as an independent predictor of impaired ASA response [adjusted odds ratio (95% confidence interval) = 3.7 (1.08-12.4), P = 0.04].

CONCLUSIONS

Among patients with CAD, elevated homocysteine is an independent predictor of suboptimal response to ASA, but not to ADP antagonists.

The role of point-of-care assessment of platelet function in predicting postoperative bleeding and transfusion requirements after coronary artery bypass grafting

OBJECTIVE

OBJECTIVE platelet function assessment after cardiac surgery can predict postoperative blood loss, guide transfusion requirements and discriminate the need for surgical re-exploration. We conducted this study to assess the predictive value of point-of-care testing platelet function using the Multiplate® device.

METHODS

Patients undergoing isolated coronary artery bypass grafting were prospectively recruited ( n = 84). Group A ( n = 42) patients were on anti-platelet therapy until surgery; patients in Group B ( n = 42) stopped anti-platelet treatment at least 5 days preoperatively. Multiplate® and thromboelastography (TEG) tests were performed in the perioperative period. Primary end-point was excessive bleeding (>2.5 ml/kg/h) within first 3 h postoperative. Secondary end-points included transfusion requirements, re-exploration rates, intensive care unit and in-hospital stays.

RESULTS

Patients in Group A had excessive bleeding (59% vs. 33%, P = 0.02), higher re-exploration rates (14% vs. 0%, P < 0.01) and higher rate of blood (41% vs. 14%, P < 0.01) and platelet (14% vs. 2%, P = 0.05) transfusions. On multivariate analysis, preoperative platelet function testing was the most significant predictor of excessive bleeding (odds ratio [OR]: 2.3, P = 0.08), need for blood (OR: 5.5, P < 0.01) and platelet transfusion (OR: 15.1, P < 0.01). Postoperative "ASPI test" best predicted the need for transfusion (sensitivity - 0.86) and excessive blood loss (sensitivity - 0.81). TEG results did not correlate well with any of these outcome measures.

CONCLUSIONS

Peri-operative platelet functional assessment with Multiplate® was the strongest predictor for bleeding and transfusion requirements in patients on anti-platelet therapy until the time of surgery.

Plasma viscosity, functional fibrinogen, and platelet reactivity in vascular surgery patients

BACKGROUND

Platelet reactivity changes with shear stress, which in turn depends on whole blood and plasma viscosity (PV). Platelets interact with fibrinogen during thrombus formation, and fibrinogen is a determinant of PV. The respective role of PV and fibrinogen on platelet function is still unclear.

METHODS

30 patients undergoing vascular surgery were admitted to this study. In each patient we measured PV using a cone-on-plate viscosimeter, functional fibrinogen using thromboelastometry, and platelet reactivity to thrombin receptor activating peptide (TRAP) stimulation using multi-electrode aggregometry. Routine coagulation parameter were measured.

RESULTS

At the univariate analysis, platelet reactivity was positively associated with mean platelet volume (R2 = 0.15, P = 0.033) and PV (R2 = 0.35, P = 0.0006), and negatively associated with serum bilirubin (R2 = 0.20, P = 0.013) and international normalized ratio (INR) (R2 = 0.19, P = 0.017). At the multivariable analysis, only PV (P = 0.001) and INR (P = 0.019) remained independent predictors of platelet reactivity.

CONCLUSION

PV is directly and independently associated with platelet reactivity, whereas functional fibrinogen is not. Aspirin treatment is inadequate to correct thrombin-induced platelet aggregation. In presence of hyperviscosity, patients at high cardiovascular risk, may benefit from more aggressive anti-platelet treatments.