Effect of different anticoagulants on multiple electrode platelet aggregometry after clopidogrel and aspirin administration in patients undergoing coronary stent implantation: a comparison between citrate and hirudin

Adjunctive Cilostazol in Patients With High Residual Platelet Reactivity After Drug-Eluting Stent Implantation: A Randomized, Open-Label, Single-Center, Prospective Study (ADJUST-HPR)

BACKGROUND

Cilostazol as an adjunct to dual antiplatelet therapy (DAPT) postcoronary stenting may further reduce vascular occlusion risks. The aim of this study was to assess the impact of cilostazol on high residual platelet reactivity (HRPR) in patients undergoing drug-eluting coronary stent implantation.

METHODS

In a randomized, open-label, single-center, prospective study, the degree of platelet inhibition by cilostazol 100 mg twice daily was assessed on top of conventional DAPT compared with standard clopidogrel and low-dose aspirin combination in poststent patients with HRPR. HRPR was defined as P2Y12 units (PRU) > 240 as measured by the VerifyNow P2Y12 assay. In addition, the platelet activity was assessed by light transmittance aggregometry (LTA) and Multiplate electrode analyzer (MEA).

RESULTS

The total of 148 patients were screened, and HRPR was observed in 64 (43.2%). Those were randomized for DAPT versus triple therapy (TAPT). After 30 days, TAPT group exhibited significantly lower rate of HRPR when assessed by all 3 devices (VerifyNow: 40.0 vs. 66.7% P = 0.04, LTA: 6.7 vs. 30.0% P = 0.02, MEA: 10.0 vs. 30.0% P = 0.05 L all vs. DAPT). Also, higher absolute mean difference in TAPT versus DAPT group after 30 days (VerifyNow: 71.3 ± 38.2 vs. 24.6 ± 40.2 P < 0.001, LTA: 23.9 ± 15.1 vs. 9.4 ± 11.8 P < 0.001, MEA: 9.3 ± 12.9 vs. 2.4 ± 17.3 P = 0.08) was observed.

CONCLUSIONS

Cilostazol in addition to standard DAPT reduces the incidence of HRPR and diminishes further platelet activity in poststent patients. Whether this favorable laboratory finding will affect clinical outcomes requires an adequately powered randomized trial.

Atherothrombosis-on-Chip: A Site-Specific Microfluidic Model for Thrombus Formation and Drug Discovery

Atherothrombosis, an atherosclerotic plaque disruption condition with superimposed thrombosis, is the underlying cause of cardiovascular episodes. Herein, a unique design is presented to develop a microfluidic site-specific atherothrombosis-on-chip model, providing a universal platform for studying the crosstalk between blood cells and plaque components. The device consists of two interconnected microchannels, namely main and supporting channels: the former mimics the vessel geometry with different stenosis, and the latter introduces plaque components to the circulation simultaneously. The unique design allows the site-specific introduction of plaque components in stenosed channels ranging from 0% to above 50%, resulting in thrombosis, which has not been achieved previously. The device successfully explains the correlation between vessel geometry and thrombus formation phenomenon as well as the influence of shear rate on platelet aggregation, confirming the reliability and the effectiveness of the design. The device exhibits significant sensitivity to aspirin. In therapeutic doses (50 × 10^-6 and 100 × 10^-6 m), aspirin delays and prevents platelet adhesion, thereby reducing the thrombus area in a dose-dependent manner. Finally, the device is effectively employed in testing the targeted binding of the RGD (arginyl-glycyl-aspartic acid) labeled polymeric nanoparticles on the thrombus, extending the use of the device to examine targeted drug carriers.

Bleeding Complication in a Patient with Concomitant Use of Rivaroxaban and Saffron Supplement: a Case Report

BACKGROUND

Direct oral anticoagulants (DOACs) carry a lower potential risk of food/herb and drug interactions compared with oral vitamin K antagonists. However, as a new class of medications, drug interactions of DOACs have not been fully known.

CASE PRESENTATION

We herein present the case of a 64-year old male with the complaint of acute onset epistaxis and bleeding gums following the concomitant use of rivaroxaban and saffron supplement. It seems that coadministration of DOACs and saffron supplements should be avoided due to the potential drug-herbal interactions and possible risk of subsequent bleeding complications.

CONCLUSION

However, further larger scale surveillance studies are needed to confirm the findings and assess the clinical significance.

The Influence of Prostaglandin E1 and Use of Inhibitor Percentage on the Correlation between the Multiplate and VerifyNow in Patients on Dual Antiplatelet Therapy

Platelet function tests (PFT), such as the Multiple Electrode Analyzer (Multiplate) and VerifyNow, show little concordance in patients using antiplatelet drugs. A major difference between these tests is the use of prostaglandin E1 (PGE1) to inhibit P2Y1-platelet-receptor activation in VerifyNow and is proposed to be of influence in the discrepancy between these tests. We aimed to investigate whether the presence of PGE1 could provide an explanation for the moderate correlation and concordance between Multiplate and VerifyNow by adding PGE1 to the Multiplate ADP assay, also known as the ADP-high sensitivity (ADP-HS) assay. We also aimed to investigate whether the difference in baseline platelet function as measured by the VerifyNow and Multiplate could (partly) explain the moderate correlation between the tests, by plotting ADP assay results against baseline function as measured by the corresponding device, which is expressed as the 'inhibitor percentage.' Fifty-one patients who underwent percutaneous coronary intervention (PCI) received dual antiplatelet therapy and were considered to have a high risk of ischemic or bleeding complications were included. The addition of 20 µl PGE1 in the Multiplate resulted in a significant reduction in Arbitrary Aggregation Units, but did not improve correlation with the VerifyNow. The correlation between VerifyNow and Multiplate inhibitor percentage was moderate. Based on these results, we concluded that neither PGE1 nor the calculation of the inhibitor percentage greatly influenced the correlation between PFTs.

Comparison of factors affecting platelet reactivity in various platelet function tests

Previous studies have reported that various factors affect ADP-induced platelet reactivity during clopidogrel therapy. The aim of this study was to determine whether clinical and laboratory variables for platelet reactivity during dual antiplatelet therapy (DAPT) are dependent on the assay used. We enrolled 904 patients receiving DAPT following coronary intervention. Platelet reactivity was measured using three methods: the VerifyNow P2Y12 assay, multiple electrode aggregometry (MEA) ADP assay, and the light transmittance aggregometry (LTA) ADP assay at 24-48 h following coronary intervention. The VerifyNow results demonstrated a significant inverse correlation with hematocrit value (r = -0.268, p < 0.0001); however, MEA results had no such correlation with hematocrit (r = 0.044, p = 0.188). There was a positive correlation between the MEA results and platelet count (r = 0.255, p < 0.0001). LTA was weakly influenced by hematocrit (r = -0.064, p = 0.057) and platelet count (r = 0.069, p = 0.040). Gender (odds ratio 1.53, 95% CI 1.10-2.14, p = 0.013) and hematocrit (odds ratio 0.91,95% CI 0.88-0.94, p < 0.0001) were the independent variables for HPR by VerifyNow. Smoking (odds ratio 0.38, 95% CI 0.16-0.94, p = 0.036) and platelet count (odds ratio 1.01, 95% CI 1.00-1.01, p < 0.0001) were independent factors for HPR when using the MEA assay, whereas platelet count (odds ratio 1.00, 95% CI 1.00-1.01, p = 0.006) was identified as the only independent variable for HPR when using LTA. The incidence of HPR and the influencing variables involved are dependent on the platelet function test used.

On-treatment platelet reactivity in peripheral and coronary blood in patients undergoing primary PCI for ST-segment elevation myocardial infarction (STEMI)

Dual antiplatelet therapy is recommended in patients undergoing primary percutaneous coronary intervention (p-PCI) for ST-segment elevation myocardial infarction (STEMI). Pre-analytical variables may influence platelet function analysis results. Our aim was to evaluate the on-treatment platelet reactivity in peripheral artery vs coronary blood in patients with STEMI. We enrolled one hundred and nine patients who consecutively underwent p-PCI at Cardiology Unit of Padua University Hospital between June 2014 and June 2015. Before the procedure, all patients received intravenous aspirin 250 mg and either of the thienopyridines; clopidogrel 600 mg, prasugrel 60 mg or ticagrelor 180 mg. ASPI-test and ADP-test using multiple electrode aggregometry (MEA) were performed in samples collected from both a peripheral artery and the culprit coronary artery. 'Low responders' were patients with an ASPI-test or ADP-test value greater than or equal to a pre-established normal range. No significant differences were observed in ASPI-test values between peripheral (19 (median) [3-49 (10-90 percentiles)] U) vs coronary (12 [1-40] U, p = .06) blood and in ADP-test (40 [14-82] U vs 33 [7-79] U, p =.68) blood. In peripheral blood, fifteen (14%) patients were 'low aspirin' and forty-one (38%) 'low thienopyridines' responders. The prevalence of 'low clopidogrel' responders was higher (45%) than prasugrel (36%) and ticagrelor (33%). Similar results were observed in coronary blood. In patients undergoing p-PCI for STEMI, MEA platelet function observed in coronary arteries was consistent with peripheral artery blood's independently of the antiplatelet drug used. The clinical significance of peripheral and coronary on-aspirin/thienopyridines platelet reactivity needs further clarification.

Comparison of four methods to assess high-on platelet reactivity under P2Y12 receptor inhibitor

P2Y12 receptor inhibitors are antiplatelet agents commonly prescribed in the treatment of coronary artery disease. Their efficacy can be limited by high on-treatment platelet reactivity (HPR), which can be evaluated by different biological assays. Most commonly, HPR is evaluated by flow cytometric vasodilator-stimulated phosphoprotein-phosphorylation (VASP-P) assay, which can be time consuming. To evaluate the potential interest of novel technologies, we compared four different assays. Ninety patients receiving P2Y12 inhibitors were included. Four technologies were evaluated: the current standard test measuring VASP-P by flow cytometry, the historical reference test based on light transmittance aggregation (LTA), and two relatively novel techniques: whole blood multiple electrode aggregometry (MEA) and platelet function analyzer (PFA), which are less time consuming. The three latter tests were compared with the VASP-P assay as a reference using receiver operating characteristics (ROC) analysis: LTA has an excellent comparability with the VASP test (ROC AUC > 0.9); the other two tests (multiplate and PFA) have only satisfactory comparability (ROC AUC around 0.7) and therefore may not replace the VASP "gold standard" test, if importance is attached to a quantitative assessment of the substitution parameter of VASP. Nevertheless, if a binary approach of the anti-aggregation result is sought, then one can conclude that the three tests are equivalent since Cohen's kappa coefficients are very close for the three tests (k = 0.548 for LTA; k = 0.554 for MEA; k = 0.570 for PFA/P2Y), and a similar proportion of patients are misclassified (15% for LTA, 14% for MEA, and 13.6% for PFA). Discriminant factor analysis using all the parameters provided by each test did not improve the diagnostic performance of MEA or PFA. In conclusion, only LTA shows a good comparability to the VASP assay using ROC curve analysis, probably because misclassified patients have results close to the cutoff values. All three tests have moderate agreement regarding the classification of patients as responders to P2Y12 inhibition.

Hirudin anticoagulation allows more rapid determination of P2Y12 inhibition by the VerifyNow P2Y12 assay

VerifyNow (VN) P2Y12 is a point-of-care assay used to assess response to P2Y12 inhibitors. Sodium citrate (citrate) is the standard anticoagulant used for this assay but requires a pre-incubation period. Hirudin is an alternative anticoagulant for platelet function studies that maintains physiological divalent cation levels. We investigated whether hirudin anticoagulation might allow more rapid testing of P2Y12 inhibition at the time of percutaneous coronary intervention (PCI). Blood was collected from the arterial sheath of aspirin-treated patients undergoing elective, urgent or emergency coronary angiography ± PCI and aliquots were anticoagulated with either citrate or hirudin. For each anticoagulant, VN P2Y12 was performed both immediately and after 20 minutes. A total of 98 patients were included in this study following pre-treatment with clopidogrel (n = 88), prasugrel (n = 6) or no P2Y12 inhibitor (n = 4). PRU with hirudin immediately (PRU_H_Imm) and PRU with citrate 20 minutes post sampling (PRU_C_20) were very strongly correlated (R = 0.95) though PRU_H_Imm tended to be lower than PRU_C_20 so that optimal correlation was estimated by the equation PRU_H_Imm = 0.95 x PRU_C_20 (p < 0.001). Bland-Altman plots showed good agreement between PRU_H_Imm and (0.95 x PRU_C_20). Platelet reactivity was more stable over the studied time course with hirudin as compared to citrate. We therefore conclude that VN P2Y12 with hirudin anticoagulation can be performed more rapidly and results are strongly correlated with delayed citrate measurements. Further studies are warranted to assess the utility of this method for improving clinical outcomes in patients undergoing PCI.

Determinants of reduced antiplatelet effect of aspirin in patients with stable coronary artery disease

Background

Aspirin is a cornerstone in management of coronary artery disease (CAD). However, considerable variability in the antiplatelet effect of aspirin has been reported.

Aim

To investigate independent determinants of reduced antiplatelet effect of aspirin in stable CAD patients.

Methods

We performed a cross-sectional study including 900 stable, high-risk CAD patients. Among these, 795 (88%) had prior myocardial infarction, 250 (28%) had type 2 diabetes, and 170 (19%) had both. All patients received 75 mg aspirin daily as mono antiplatelet therapy. The antiplatelet effect of aspirin was assessed by measurement of platelet aggregation employing 1) multiple electrode aggregometry (MEA, Multiplate Analyzer) in whole blood anticoagulated with citrate or hirudin using arachidonic acid (AA) or collagen as agonists, and 2) VerifyNow Aspirin Assay. Compliance was assessed by measurement of serum thromboxane B₂.

Results

Platelet count, prior myocardial infarction, type 2 diabetes and body mass index were independent determinants of increased AA-induced MEA platelet aggregation in citrate and hirudin anticoagulated blood (p-values ≤ 0.045). Similar results were found with VerifyNow. Prior coronary artery bypass grafting, age, smoking (MEA, AA/citrate) and female gender (MEA, AA/hirudin) were also independent determinants of increased platelet aggregation (p-values ≤ 0.038). Compliance was confirmed by low serum thromboxane B₂ levels in all patients (median [25%;75%]: 0.97 [0.52;1.97], range 0.02-26.44 ng/ml).

Conclusion

Platelet count, prior myocardial infarction, type 2 diabetes and body mass index were independent determinants of increased platelet aggregation, indicating that these characteristics may be key factors in reduced antiplatelet effect of aspirin in stable CAD patients.

Reference range determination for whole-blood platelet aggregation using the Multiplate analyzer

OBJECTIVES

To develop reference ranges for platelet aggregation using the Multiplate analyzer (Roche Diagnostics, Mannheim, Germany) in blood anticoagulated with sodium citrate (Na-citrate), lithium heparin (Li-heparin), or hirudin.

METHODS

The study was performed at three sites on consented, healthy adults (n = 193) not taking antiplatelet medication. Platelet aggregation was evaluated in response to adenosine-5'-diphosphate, arachidonic acid, collagen, thrombin receptor activating peptide, ristocetin, and adenosine-5'-diphosphate combined with prostaglandin E1. Precision testing was conducted using healthy donors and donors taking aspirin.

RESULTS

Whole-blood platelet aggregation showed anticoagulant-dependent differences in platelet responses to all agonists. Samples collected in Na-citrate demonstrated the lowest responses to all agonists. The highest responses were obtained using Li-heparin. Precision testing revealed high variability in platelet aggregation at lower agonist doses, regardless of anticoagulant. Highest platelet response variations occurred in response to arachidonic acid in blood anticoagulated with hirudin from participants taking aspirin.

CONCLUSIONS

These data demonstrate the importance of establishing locally relevant reference ranges.

Rapid evaluation of platelet function using the Multiplate® Analyzer

Rapid evaluation of platelet function may be advantageous in the setting of surgical and interventional procedures to tailor treatment of ongoing bleeding. We investigated if platelet function testing performed with the Multiplate® Analyzer (Roche Diagnostics, Mannheim, Germany) only 5 minutes after blood sampling yields reliable test results compared to analyses performed 30 minutes after sampling as currently recommended. We included 48 patients with type II diabetes and stable coronary artery disease treated with aspirin 75 mg daily and 50 healthy individuals not taking any medications. Platelet aggregometry by the Multiplate® Analyzer was performed 5 and 30 minutes after blood sampling using arachidonic acid (1.0 mM), collagen (3.2 µg/ml) and adenosine diphosphate (ADP; 6.5 µM) as agonists. Compliance with aspirin was verified by serum thromboxane B2 measurements. Aggregation levels assessed 5 minutes after blood sampling correlated strongly with those assessed after 30 minutes irrespective of the agonist used (r-values 0.75-0.89, p values <0.0001). Aggregation levels were 4-8% lower and displayed a larger standard deviation when measured 5 minutes after sampling, compared to 30 minutes after sampling. Weak, but significant correlations were observed between platelet aggregation and platelet count (r-values = 0.28-0.39; p values <0.01). The currently recommended 30-minute standing time can be omitted, when platelet aggregation is measured using the Multiplate® Analyzer. Platelet aggregation measured 5 minutes after blood sampling correlates strongly with aggregation measured 30 minutes after sampling, but yields slightly lower aggregation levels. The Multiplate® Analyzer enables rapid on-site evaluation of platelet function.