Residual platelet reactivity is preferred over platelet inhibition rate in monitoring antiplatelet efficacy: insights using thrombelastography

Changes in platelet function and coagulation after transcatheter aortic valve implantation evaluated with thromboelastography

Introduction

The possibility of hypercoagulability during the perioperative period of transcatheter aortic valve implantation (TAVI) has been noted; however, there is still a controversy regarding the appropriate perioperative antithrombotic therapy. The study investigated coagulation and platelet functions during the TAVI perioperative period using thromboelastography (TEG) 6s platelet mapping.

Methods

A prospective observational study was conducted on 25 patients undergoing TAVI. TEG platelet mapping was performed at three time points: on admission to the operating room (before heparinisation), on postoperative day (POD) 1 and on POD 3. Perioperative changes observed included: maximum clot strength (MA_HKH), clot strength without platelet function (MA_ActF), time to initiation of clots formation by coagulation factors (R_HKH) and platelet function (G_p). G_p is activated by thrombin, and not affected by antiplatelet agents. It is calculated as [(5000×MA_HKH)/(100 – MA_HKH)] − [(5000×MA_ActF)/(100 – MA_ActF)]. Finally, MA_ADP/AA and G_ADP/AA, which reflect clot strength and platelet aggregation mediated by ADP/thromboxane A₂ receptors, respectively, were also examined using the same method as for G_p.

Results

MA_HKH continued to decrease until POD 3, indicating antithrombotic change after TAVI. G_p continuously decreased for 3 days after TAVI, while MA_ActF increased significantly on POD 3. Furthermore, R_HKH shortened on POD 1 and POD 3, suggesting increased coagulation capacity after TAVI. Finally, G_ADP in clopidogrel-naive patients was reduced for 3 days after TAVI, while G_AA in aspirin-naive patients showed no significant change perioperatively.

Conclusions

In this study involving TEG platelet mapping, coagulation capacity increased while platelet function decreased, resulting in antithrombotic change for 3 days after TAVI. The ADP receptor system may be implicated in the decreased platelet function. These results may be useful for considering optimal perioperative antithrombotic therapy in TAVI.

The predictive value of Thromboelastography (TEG) parameters in vascular complications in patients with type 2 diabetes mellitus

AIMS

The purpose of this research was to explore the association of TEG parameters (Reaction time, R; Clot kinetics, K; Alpha angle, α-angle; Maximum amplitude, MA) with vascular complications of type 2 diabetes mellitus (T2DM), and assess whether TEG parameters could predict T2DM patients with vascular complications.

METHODS

A total of 68 healthy controls (HC), 57 T2DM patients without vascular complications (NC), 18 T2DM patients with only microvascular complications (MIC), 196 T2DM patients with only macrovascular complications (MAC), and 94 T2DM patients with both microvascular and macrovascular complications (MIC+MAC) were recruited in this study. Participants' clinical information and TEG parameters were recorded. TEG parameters were analyzed by the Jonckheere-Terpstra trend test, assuming the vascular complication was progressing from HC → NC → MIC → MIC+MAC or HC → NC → MAC → MIC+MAC. Receiver operating characteristic (ROC) was performed to explore the diagnostic accuracy of TEG parameters in T2DM with vascular complications.

RESULTS

Shorter TEGK, higher TEG-α-angle, and higher TEG-MA were found in T2DM patients with both microvascular and macrovascular complications (MIC+MAC) group compared with healthy controls (HC) group and T2DM patients without vascular complications (NC) group (P < 0.05). Trend analysis showed that TEG-R/K decreased, but TEG-α-angle/MA increased gradually as the vascular complication progressed (P < 0.001). With stratification of urine microalbumin/creatinine ratio (UACR), diabetic nephropathy with macroalbuminuria (grade A3) behaves shorter TEGK, higher TEG-α-angle/MA compared with normal to mildly increased albuminuria (grade A1) and microalbuminuria (grade A2) (P < 0.05). ROC curves implied that TEGK, TEG-α-angle, and TEG-MA have moderate diagnostic values in T2DM without vascular complications (K-AUC: 0.780, α-angle-AUC: 0.773, and MA-AUC: 0.740) as well as T2DM with both microvascular and macrovascular complications (K-AUC: 0.778, α-angle-AUC: 0.757, and MA-AUC: 0.800).

CONCLUSION

TEG parameters are associated with the progression of vascular complications in T2DM, and it could be a diagnostic indicator for T2DM without vascular complications or with advanced vascular complications.

The Use of Thromboelastography in Percutaneous Coronary Intervention and Acute Coronary Syndrome in East Asia: A Systematic Literature Review

Dual antiplatelet therapy (DAPT), alongside percutaneous coronary intervention (PCI), is central to the prevention of ischemic events following acute coronary syndrome (ACS). However, response to therapy can vary due to several factors including CYP2C19 gene variation, which shows increased prevalence in East Asian populations. DAPT responsiveness can be assessed using techniques such as light transmission aggregometry (LTA), VerifyNow^® and thromboelastography with the PlateletMapping^® assay, and there is increasing focus on the utility of platelet function testing to guide individualized treatment. This systematic literature review of one English and three Chinese language databases was conducted to evaluate the evidence for the utility of thromboelastography in ACS/PCI in East Asia. The search identified 42 articles from the English language and 71 articles from the Chinese language databases which fulfilled the pre-determined inclusion criteria, including 38 randomized controlled trials (RCTs). The identified studies explored the use of thromboelastography compared to LTA and VerifyNow in monitoring patient responsiveness to DAPT, as well as predicting ischemic risk, with some studies suggesting that thromboelastography is better able to detect low DAPT response than LTA. Other studies, including one large RCT, described the use of thromboelastography in guiding the escalation of DAPT, with some evidence suggesting that such protocols reduce ischemic events without increasing the risk of bleeding. There was also evidence suggesting that thromboelastography can be used to identify individuals with DAPT hyporesponsiveness genotypes and could potentially guide treatment by adjusting therapy in patients depending on responsiveness.

Prediction of residual ischemic risk in ticagrelor-treated patients with acute coronary syndrome

BACKGROUND

Despite strong antiplatelet therapy with ticagrelor, serious ischemic events still occur in patients with acute coronary syndrome (ACS). The predictability of platelet reactivity to the residual risk of ischemic events during ticagrelor treatment remains uncertain.

OBJECTIVES

We aimed to investigate the predictability of the thromboelastography (TEG)-measured adenosine disphosphate (ADP)-induced platelet inhibition rate (ADP%) to the ischemic events in ticagrelor-treated patients with ACS.

METHODS

A cohort of ticagrelor-treated patients with ACS were consecutively recruited. ADP% was measured by TEG after 3 days of ticagrelor maintenance treatment. The primary ischemic event was defined as rehospitalization for unstable angina (UA) within 1 year, and the secondary ischemic event was a composite of the primary ischemic event plus all-cause death, nonfatal myocardial infarction (MI), stent thrombosis, stroke, and unplanned revascularization within 1 year.

RESULTS

A total of 751 eligible patients with ACS were included in the analysis, with 336 patients randomly assigned to the derivation group and 415 to the validation group. The overall rates of primary and secondary ischemic events were 14.51% (n = 109) and 16.91% (n = 127), respectively. Compared to the patients without ischemic events, those with ischemic events had a significantly lower ADP% both in the derivation group (for primary ischemic events: 66.05% vs. 92.80%, p < 0.001; for secondary ischemic events: 66.05% vs. 93.20%, p < 0.001) and in the validation group (for primary ischemic events: 66.40% vs. 89.20%, p < 0.001; for secondary ischemic events: 66.90% vs. 89.20%, p < 0.001). Receiver operating characteristic curve (ROC) analysis showed that an ADP% < 76% was the optimal cut-off value for predicting 1-year primary ischemic events, with an area under the curve (AUC) of 0.80 (95% CI: 0.72-0.86, p < 0.001) in the derivation group and 0.77 (95% CI: 0.69-0.85, p < 0.001) in the validation group. The multivariate Cox regression hazard analysis consistently identified an ADP% < 76% as an independent predictor of primary ischemic events in the derivation group (HR: 8.21, 95% CI: 4.82-13.99, p < 0.001) and in the validation group (HR: 6.34 95% CI: 3.32-12.11, p < 0.001). There was also a strong association between an ADP% < 76 and the occurrence of secondary ischemic events in the derivation group (HR: 7.33, 95% CI: 4.47-12.00, p < 0.001) and in the validation group (HR: 4.76, 95% CI: 2.73-8.32, p < 0.001).

CONCLUSION

The ADP-induced platelet inhibition rate measured by TEG could predict ischemic events in ticagrelor-treated patients with ACS.

Development and Validation of a Novel Tool for the Prediction of Clopidogrel Response in Chinese Acute Coronary Syndrome Patients: The GeneFA Score

Aim: Growing evidence indicated that CYP2C19 genotypes could only explain a fraction of the pharmacodynamic response to clopidogrel, while a number of clinical factors also have contributing roles. Our objective was to develop a new risk score to improve prognostication of ischemic events in Chinese patients treated with clopidogrel. Methods: A new risk score was developed and internally validated in 445 patients with acute coronary syndrome (ACS) undergoing coronary stenting. The final score was named the GeneFA score based on the inclusion of CYP2C19 genotype, fibrinogen, and age. External validation of the GeneFA score and comparison with the ABCD-GENE score were performed in an independent ACS cohort. Results: Based on the observed frequencies of high platelet reactivity (HRPR) in relation to the GeneFA risk score, a relatively higher clinical HRPR was observed in the upper quintile with a representative score of 3 (52.90%) and 4 (59.10%), whereas it was found less frequently in groups with scores 0 (6.70%), 1 (15.10%), and 2 (16.70%). Participants with a GeneFA score >2 had an increased risk of HRPR (54.3 vs. 14.7%, p < 0.001) and ischemic recurrence (20.7 vs. 5.4%, p < 0.001). The GeneFA score exhibited a better prediction for high HRPR patients as compared to the ABCD-GENE score (p < 0.001). In the validation population, GeneFA illustrated a similarly high prognostic value for HRPR incidence (C-statistic: 0.855 for GeneFA and 0.843 for ABCD-GENE) and ischemic recurrence (C-statistic: 0.726 for GeneFA and 0.724 for ABCD-GENE) on clopidogrel as compared to ABCD-GENE. Conclusion: The GeneFA risk score had a moderate predictive ability for HRPR on clopidogrel for CAD patients in Chinese populations. The predictive value of the GeneFA score was consistent with the ABCD-GENE score for HRPR identification.

Platelet Function Tests Predicting the Efficacy and Safety of Aspirin Secondary Prevention

OBJECTIVE

To precisely prevent stroke, we evaluated three platelet function tests and their associations with clinical outcomes in ischemic stroke patients.

METHODS

On-treatment platelet reactivity of acute minor stroke patients taking aspirin plus clopidogrel was tested by light transmittance aggregometry (LTA), thromboelastography (TEG) and platelet function analyzer (PFA). Mann-Whitney U tests and receiver operating characteristic (ROC) curve analysis were used to assess their associations with recurrent events and clinical outcome prediction.

RESULTS

127 acute minor stroke patients were stringently selected and followed for 13 months. Eight patients (6.3%) self-reported the recurrence and 13 (10.2%) patients self-reported bleeding. Recurrent patients displayed significantly higher on-treatment platelet reactivity when measured with LTA (p = 0.030) and PFA (p < 0.001). Further ROC analysis demonstrated that LTA and PFA had modest-to-fair ability to predict stroke recurrence (LTA: area under the curve [AUC], 0.765; 95% CI, 0.584-0.945, PFA: AUC, 0.832; 95% CI, 0.658-1.000). However, TEG (measured by the platelet inhibition rate) could not detect the difference between recurrent patients and non-recurrent patients (p = 0.515) and predict recurrent events (AUC, 0.569; 95% CI, 0.368-0.770). None of the tests were associated with bleeding except for PFA (p < 0.001), with AUC of PFA reaching 0.772 (0.726-0.818).

CONCLUSIONS

Of the three tests assessed, the predictive accuracies of PFA and LTA were satisfying for aspirin secondary prevention, while TEG's performance was poor. Only PFA could provide accurate prognostic information for bleeding.

The role of viscoelastic testing in assessing peri-interventional platelet function and coagulation

We carried out a literature search in MEDLINE (PubMed) and EMBASE literature databases to provide a concise review of the role of viscoelastic testing in assessing peri-interventional platelet function and coagulation. The search identified 130 articles that were relevant for the review, covering the basic science of VHA and VHA in clinical settings including cardiac surgery, cardiology, neurology, trauma, non-cardiac surgery, obstetrics, liver disease, and COVID-19. Evidence from these articles is used to describe the important role of VHAs and platelet function testing in various peri-interventional setups. VHAs can help us to comprehensively assess the contribution of platelets and coagulation dynamics to clotting at the site-of-care much faster than standard laboratory measures. In addition to standard coagulation tests, VHAs are beneficial in reducing allogeneic transfusion requirements and bleeding, in predicting ischemic events, and improving outcomes in several peri-interventional care settings. Further focused studies are needed to confirm their utility in the peri-interventional case.

Thromboelastography predicts dual antiplatelet therapy-related hemorrhage in patients with acute ischemic stroke

Background

Stratification of the risk of hemorrhage in patients with acute ischemic stroke following dual antiplatelet therapy (DAPT) is challenging. It remains unclear whether thromboelastography (TEG) can be used to predict DAPT-related hemorrhagic events.

Objective

The present study aims to discover predictors for hemorrhage events after DAPT based on parameters such as TEG.

Methods

A total of 859 patients with acute ischemic stroke who received DAPT were recruited consecutively. Demographic, clinical, and neuroimaging characteristics were evaluated at baseline; TEG parameters were obtained 7 days later after DAPT. Hemorrhagic events were monitored about 1 month after the stroke.

Results

Of the patients, 61 (7.1%) had hemorrhagic events. Patients in the hemorrhage group had a lower adenosine diphosphate (ADP)-induced platelet-fibrin clot maximum amplitude and a higher ADP inhibition rate (ADP%) than those in the non-hemorrhage group (p<0.05). ADP% was confirmed as an independent predictor of hemorrhagic events with an optimal cut-off point of 83.3% (area under the curve (AUC) = 0.665, 95% CI 0.573 to 0.767, p<0.01). We constructed a logistic model based on D-dimer, National Institutes of Health Stroke Scale scores, and ADP% to predict hemorrhagic events in patients with acute ischemic stroke during DAPT (AUC=0.720, 95% CI 0.625 to 0.858, p<0.01), with a sensitivity of 72.1% and a specificity of 76.5%.

Conclusions

Monitoring changes of TEG parameters helps to guide personalized DAPT for patients with ischemic stroke. A 30–82.3% range of ADP% is recommended for DAPT treatment.

Impact of renal function on residual platelet reactivity and clinical outcomes in patients with acute coronary syndrome treated with clopidogrel

BACKGROUND

Chronic kidney disease (CKD) is a common comorbidity in patients with acute coronary syndrome (ACS) and may potentially influence platelet function.

HYPOTHESIS

We explored the influence of renal function on platelet reactivity to investigate whether high residual platelet reactivity (HRPR) is associated with cardiovascular events.

METHODS

ACS patients treated with aspirin and clopidogrel were prospectively enrolled. Patients were categorized into two groups on the basis of baseline estimated glomerular filtration rate (eGFR): non-CKD (eGFR ≥60 mL/min/1.73 m2 ) and CKD (eGFR <60 mL/min/1.73 m2 ). Platelet function was measured by thromboelastography ≥5 days after maintenance dual antiplatelet therapy. Major adverse clinical events (MACEs) were collected at 1 year after discharge.

RESULTS

There were 282 non-CKD patients and 212 CKD patients. A significant difference in median MAADP value was observed between the two groups (15.0 mm vs. 31.3 mm, p < .001). HRPR was more prevalent in the CKD group than the non-CKD group (27.4% vs 9.6%, p < .001). At 1-year follow-up, the incidence of MACEs was significantly higher for those with both CKD and HRPR compared with those with either CKD or HRPR (37.9% vs. 18.5%, p < .001). The relationship between HRPR and MACEs was consistent across CKD strata without evidence of interaction. Adding platelet reactivity to eGFR improved the model with area under the curve increasing from 0.703 to 0.734.

CONCLUSION

In patients with ACS, the risk of HRPR increased with declining eGFR. Both CKD and HRPR were associated with MACEs at 1-year follow-up.

Net platelet clot strength of thromboelastography platelet mapping assay for the identification of high on-treatment platelet reactivity in post-PCI patients

High-on treatment platelet reactivity (HTPR) leads to more prevalence of thrombotic event in patients undergoing percutaneous coronary interventions (PCI). Dual antiplatelet therapy with aspirin in addition to one P2Y₁₂ inhibitor is commonly administrated to reduce HTPR. However, ‘one size fits all’ antiplatelet strategy is widely implemented due to lacking benefits with tailored strategy. One reason for the failure of tailored treatment might be less specificity of the current indicators for HTPR. Therefore, searching for specific indicators for HTPR is critical. Thromboelastograph with platelet mapping (TEGpm) assay has been explored for identifying HTRP. Variables of TEGpm assay, including maximum amplitude (MA) induced by thrombin (MAthrombin), R time, platelet aggregation rate induced by ADP (TEGaradp) and MA induced by ADP (MAadp) have been demonstrated to be able to identify HTPR in post-PCI patients. However, these variables for HTPR might be less specific. Thus, in the present study, a novel variable nMAadp was derived by removing fibrin contribution from MAadp and analyzed for its usefulness in determining HTPR. In addition, MAthrombin, R time, MAadp and TEGaradp were also examined for determining HTPR. In conclusion, nMAadp and TEGaradp were demonstrated to be independent indicators for HTPR; nMAadp had the strongest power to identify HTPR with cutoff value of 26.3 mm; MAthrombin and R time were not significantly different between patients with and without HTPR; combination of TEGaradp and nMAadp further improved the ability to identify HTPR with an AUC of 0.893.

Viscoelastic Haemostatic Assays in Cardiovascular Critical Care

The initiation and management of anticoagulation is a fundamental practice for a wide variety of indications in cardiovascular critical care, including the management of patients with acute MI, stroke prevention in patients with AF or mechanical valves, as well as the prevention of device thrombosis and thromboembolic events with the use of mechanical circulatory support and ventricular assist devices. The frequent use of antiplatelet and anticoagulation therapy, in addition to the presence of concomitant conditions that may lead to a propensity to bleed, such as renal and liver dysfunction, present unique challenges. The use of viscoelastic haemostatic assays provides an additional tool allowing clinicians to strike a delicate balance of attaining adequate anticoagulation while minimising the risk of bleeding complications. In this review, the authors discuss the role that viscoelastic haemostatic assay plays in cardiac populations (including cardiac surgery, heart transplantation, extracorporeal membrane oxygenation, acute coronary syndrome and left ventricular assist devices), and identify areas in need of further study.

Establishment of thromboelastography reference intervals by indirect method and relevant factor analyses

Thromboelastography (TEG) as a global coagulation test has been continuously developed for many decades in either research or clinical practice. The versatility of TEG test leads to difficulty in standardization and result interpretation. Reference intervals (RIs) of TEG may be one of the most controversial factors that influence its wide applications. RIs establishment with the traditional method is time‐consuming and laborious as well as beyond general laboratory capability. Indirect method using stored data and with statistical calculation and small cost is emerging as an alternative approach for RIs determination. Gender, age, or both affect RIs and must be taken into account before RIs estimation. The present study retrospectively collected a total of 930 TEG results as subjects and established RIs with indirect method for Kaolin‐activated TEG, including the parameters of R, K, αAngle, MA, and CI. Furthermore, gender, age, and gender‐dependent age subsets analyses were performed to determine their effects on RIs of TEG. In this study, we found that TEG parameters showed more hypercoagulability in female than male, most of the measured TEG variables were significantly associated with aging, but only in male statistical significance was found among different age stratification and 60‐year‐old could be considered as cutting point to differentiate coagulation ability in male. In addition, RIs of TEG were estimated by indirect method suitably and verified to be valid in our study. Finally, the RIs of TEG by indirect method were basically significantly different to the RIs recommended by manufacturer, but the consistent percentage is relatively high in the most of measured parameters. In conclusion, it is suggestive that the indirect method for RIs establishment is feasible, but relevant factors, such as gender and age, specifically gender‐dependent age effect, should be considered before RIs determinations.