Total Thrombus-formation Analysis System Predicts Periprocedural Bleeding Events in Patients With Coronary Artery Disease Undergoing Percutaneous Coronary Intervention

The Utility of Total Thrombus-Formation Analysis System (T-TAS) in the Thrombosis and Hemostasis Field: A Scoping Review

BACKGROUND

A wide variety of laboratory hemostasis tests is available, but the majority is plasma-based, static and unable to assess platelet function and fibrin formation simultaneously. The Total Thrombus-Formation Analysis System (T-TAS) is a microchip-based flow chamber system that simulates in vivo conditions for evaluating whole blood thrombogenicity.

AIM

A comprehensive overview of its applicability in different thrombosis and hemostasis related clinical situations is lacking and therefore this scoping review was performed.

MATERIALS & METHODS

A literature search was done using the electronic databases PubMed, Scopus and Embase on January 7, 2024. Original studies assessing the usefulness of the T-TAS in thrombosis and hemostasis related clinical situations were eligible for this scoping review.

RESULTS

A total of 28 studies were included; six studies investigating the role of the T-TAS in congenital bleeding disorders, five studies using the T-TAS to assess 1-year bleeding risk in patients on antiplatelet or anticoagulant medications, four studies investigating the effects of thrombocytopenia and hemodialysis on thrombus formation as measured by the T-TAS, 11 studies testing the applicability of the T-TAS in the monitoring of anticoagulant and antiplatelet therapies and eventually two studies on the ability of the T-TAS to assess the thrombogenicity in different disease entities.

DISCUSSION & CONCLUSION

The T-TAS method is an interesting technology that mimics the complex biological coagulation process using shear forces, creating a "blood vessel component on a chip". More research is needed, but it could eventually function as a screening test for platelet function and coagulation. Moreover, it could be used to detect the presence of anticoagulant and/or antiplatelet medication.

Total Thrombus-Formation System in Patients with Peripheral Artery Disease

The Total Thrombus-formation Analysis System (T-TAS) is an automated device using coated microchips to assess thrombus formation under flow conditions. Its value to monitor coagulation function in patients under antiplatelet therapy awaits further clarification. This study evaluated T-TAS to detect response to dual antiplatelet therapy (DAPT) in patients with peripheral artery disease (PAD).T-TAS using the platelet-chip (PL-chip) and atheroma-chip (AR-chip) was performed in 60 patients with PAD on the day after lower extremity revascularization. Results were compared with light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA, ADP- and ASPI-test). To determine T-TAS reference ranges, 30 healthy blood donors were enrolled.The area under the curve of the PL-chip (AUC-PL) was outside the reference range in 91.2% and AUC-AR in 21.1% of the PAD patients. Low responders in MEA ASPI, MEA ADP or both tests and low responders in LTA induced by ADP had a significantly higher AUC-PL compared to responders (204 vs 70, p = .016 and 140 vs 32, p < .001), respectively. Median AUC-PL in low responders in LTA and MEA, LTA or MEA and in responders in LTA and MEA was 301, 104 and 32 (p = .001), respectively. Our results suggest that the PL-chip can continuously assess the level of response to DAPT and might be helpful to monitor PAD patients.

Electronic Cigarette Vaping with Nicotine Causes Increased Thrombogenicity and Impaired Microvascular Function in Healthy Volunteers: A Randomised Clinical Trial

Electronic cigarette (EC) vaping is increasingly popular, despite growing evidence of adverse health effects. To further evaluate the impact of EC use on vascular health, we investigated the effects of brief EC inhalation on flow-dependent thrombus formation and microcirculation in healthy volunteers. The study was performed with a randomised double-blind crossover design. Twenty-two healthy subjects aged between 18 and 45 years with occasional tobacco use were recruited. Subjects inhaled 30 puffs of EC aerosol with and without nicotine on two occasions separated by a wash-out period of at least 1 week. Blood samples were collected at baseline and at 15 and 60 min following exposure and analysed with the Total-Thrombus-formation analysis system evaluating fibrin-rich thrombus formation and platelet thrombus formation in whole blood under flow. Microvascular function was assessed at baseline and 30 min after exposure by laser speckle contrast imaging and iontophoresis of acetylcholine and sodium nitroprusside (SNP) to evaluate the endothelium-dependent and independent pathways of vasodilation. Compared with nicotine free EC aerosol, exposure to EC aerosol with nicotine significantly increased platelet thrombus formation and fibrin-rich thrombus formation at 15 min (p = 0.017 and p = 0.037, respectively) with normalisation after 60 min. Peak SNP-mediated microvascular perfusion, i.e. endothelium-independent vasodilation, was reduced following EC vaping with nicotine compared with baseline (p = 0.006). Thirty puffs of EC aerosol with nicotine increased platelet and fibrin-dependent thrombus formation and reduced microvascular dilatation capacity. No compelling effects of EC vaping without nicotine were observed, indicating nicotine as the main effector. Trial registration: ClinicalTrials.gov Identifier: NCT04175457 URL: https://clinicaltrials.gov/ct2/show/NCT04175457.

Japanese high bleeding risk criteria status predicts low thrombogenicity and bleeding events in patients undergoing percutaneous coronary intervention

Although the Japanese high bleeding risk criteria (J-HBR) were established to predict bleeding risk in patients undergoing percutaneous coronary intervention (PCI), the thrombogenicity in the J-HBR status remains unknown. Here, we examined the relationships among J-HBR status, thrombogenicity and bleeding events. This study was a retrospective analysis of 300 consecutive patients who underwent PCI. Blood samples obtained on the day of PCI were used in the total thrombus-formation analysis system (T-TAS) to investigate the thrombus-formation area under the curve (AUC; PL₁₈-AUC₁₀ for platelet chip; AR₁₀-AUC₃₀ for atheroma chip). The J-HBR score was calculated by adding 1 point for any major criterion and 0.5 point for any minor criterion. We assigned patients to three groups based on J-HBR status: a J-HBR-negative group (n = 80), a low score J-HBR-positive group (positive/low, n = 109), and a high score J-HBR-positive group (positive/high, n = 111). The primary end point was the 1-year incidence of bleeding events defined by the Bleeding Academic Research Consortium types 2, 3, or 5. Both PL₁₈-AUC₁₀ and AR₁₀-AUC₃₀ levels were lower in the J-HBR-positive/high group than the negative group. Kaplan-Meier analysis showed worse 1-year bleeding event-free survival in the J-HBR-positive/high group compared with the negative group. In addition, both T-TAS levels in J-HBR positivity were lower in those with bleeding events than in those without bleeding events. In multivariate Cox regression analyses, the J-HBR-positive/high status was significantly associated with 1-year bleeding events. In conclusion, the J-HBR-positive/high status could reflect low thrombogenicity as measured by T-TAS and high bleeding risk in patients undergoing PCI.

Malnutrition-associated high bleeding risk with low thrombogenicity in patients undergoing percutaneous coronary intervention

BACKGROUND AND AIMS

Although antithrombotic treatments are established for coronary artery disease (CAD), they increase the bleeding risk, especially in malnourished patients. The total thrombus-formation analysis system (T-TAS) is useful for the assessment of thrombogenicity in CAD patients. Here, we examined the relationships among malnutrition, thrombogenicity and 1-year bleeding events in patients undergoing percutaneous coronary intervention (PCI).

METHODS AND RESULTS

This was a retrospective analysis of 300 consecutive CAD patients undergoing PCI. Blood samples obtained on the day of PCI were used in the T-TAS to compute the thrombus formation area under the curve. We assigned patients to two groups based on the geriatric nutritional risk index (GNRI): 102 patients to the lower GNRI group (≤98), 198 patients to the higher GNRI group (98<). The primary endpoint was the incidence of 1-year bleeding events defined by Bleeding Academic Research Consortium criteria types 2, 3, or 5. The T-TAS levels were lower in the lower GNRI group than in the higher GNRI group. Kaplan-Meier analysis showed worse 1-year bleeding event-free survival in the lower GNRI group compared with the higher GNRI group. The combined model of the GNRI and the Academic Research Consortium for High Bleeding Risk (ARC-HBR) had good calibration and discrimination for bleeding risk prediction. In addition, having a lower GNRI and ARC-HBR positivity was associated with 1-year bleeding events.

CONCLUSION

A lower GNRI could reflect low thrombogenicity evaluated by the T-TAS and determine bleeding risk in combination with ARC-HBR positivity.

Cardiovascular risk factors are associated with augmented thrombogenicity in healthy individuals: analysis using the Total Thrombus-formation Analysis System

BACKGROUND

Rupture of an atherosclerotic plaque and subsequent exposure of the subendothelial prothrombotic matrix to blood cause arterial thrombosis. Circulating platelets play an indispensable role in the growth of arterial thrombi partially owing to their unique ability to adhere to the subendothelial matrix and to aggregate to each other under flow conditions. Recently, the Total Thrombus-formation Analysis System (T-TAS) was developed for ex vivo analysis of the thrombogenic potential of whole blood samples under flow conditions. Despite the potential clinical utility of the T-TAS in assessing the risk for thrombosis and bleeding, reference intervals for T-TAS analysis in healthy individuals have not been determined.

METHODS

In total, 122 whole blood samples were collected from healthy volunteers ranging in age from 25 to 45 years. T-TAS analysis and hematological, physiological, and lifestyle assessments were conducted in these subjects. Whole blood samples anticoagulated with hirudin were perfused into a collagen-coated microchip (PL chip). The time to 10 kPa and the area under the flow pressure curve up to 10 min (AUC₁₀) were analyzed as representative variables for thrombogenic potential. Reference intervals, which were defined as 2.5-97.5 percentiles, were determined. Additionally, univariate and multivariate analyses were performed to identify factors associated with the AUC₁₀ in the T-TAS.

RESULTS

The time to 10 kPa and the AUC₁₀ widely varied, even in healthy volunteers. The reference intervals were 1.50-4.02 min and 223.4-456.8, respectively, at a shear rate of 1500 s^- 1. Univariate and multivariate analyses showed that platelet counts were most significantly associated with the AUC₁₀ of the T-TAS. The presence of one or more cardiovascular risk factors of a high body mass index, a high pulse pressure, high fasting serum glucose levels, high low-density lipoprotein-cholesterol levels, a history of smoking, and no habitual exercise, had the second largest effect on the AUC₁₀ of the T-TAS.

CONCLUSIONS

Healthy volunteers who had any cardiovascular risk factors showed augmented thrombogenicity, even in artificial uniform capillaries, compared with those without any risk factors in the T-TAS.

The Use of Total Thrombus Formation Analysis System as a Tool to Assess Platelet Function in Bleeding and Thrombosis Risk-A Systematic Review

BACKGROUND

Today there are many devices that can be used to study blood clotting disorders by identifying abnormalities in blood platelets. The Total Thrombus Formation Analysis System is an automated microchip flow chamber system that is used for the quantitative analysis of clot formation under blood flow conditions. For several years, researchers have been using a tool to analyse various clinical situations of patients to identify the properties and biochemical processes occurring within platelets and their microenvironment.

METHODS

An investigation of recent published literature was conducted based on PRISMA. This review includes 52 science papers directly related to the use of the Total Clot Formation Analysis System in relation to bleeding, surgery, platelet function assessment, anticoagulation monitoring, von Willebrand factor and others.

CONCLUSION

Most available studies indicate that The Total Thrombus Formation Analysis System may be useful in diagnostic issues, with devices used to monitor therapy or as a significant tool for predicting bleeding events. However, T-TAS not that has the potential for diagnostic indications, but allows the direct observation of the flow and the interactions between blood cells, including the intensity and dynamics of clot formation. The device is expected to be of significant value for basic research to observe the interactions and changes within platelets and their microenvironment.

The Total Thrombus Formation (T-TAS) platelet (PL) assay, a novel test that evaluates whole blood platelet thrombus formation under physiological conditions

Dual antiplatelet therapy (DAPT, aspirin, and a P2Y₁₂ inhibitor) reduces thrombotic events in patients with coronary artery disease (CAD). The T-TAS PL assay uses arterial shear flow over collagen surface, better mimicking in vivo conditions compared to conventional agonist-based platelet function assays, to evaluate platelet function. Here, the platelet function in patients taking DAPT is evaluated with the T-TAS PL assay. In 57 patients with CAD, taking DAPT ≥7 days (n = 22 for clopidogrel, n = 15 for prasugrel, n = 20 for ticagrelor), T-TAS PL assessments were performed in duplicate, and expressed as area under the flow pressure curve within a 10-minute period (AUC10). The duplicate measurements were strongly correlated (r = 0.90, p < .001), with an intra-assay coefficient of variation (CV) of 11,5%. For clopidogrel, the median AUC10 was 11.5 (IQR5.9-41.8), for prasugrel 28.8 (IQR10.3-37.6), and for ticagrelor 8.9 (IQR 6.4-10.9). All measurements were below the AUC10 cutoff of 260 measured in healthy volunteers, suggesting excellent discrimination of DAPT-treated and untreated persons. The new T-TAS PL assay demonstrated complete discrimination of platelet function in patients on DAPT based on an established cutoff. Ticagrelor showed lower levels of platelet function and a more uniform response compared to prasugrel and clopidogrel.

Hemodialysis-related low thrombogenicity measured by total thrombus-formation analysis system in patients undergoing percutaneous coronary intervention

BACKGROUND

Established antithrombotic therapies can increase bleeding risk, especially in hemodialysis (HD) patients. The Total Thrombus-formation Analysis System (T-TAS) is useful for evaluating thrombogenicity. The aim of this study was to examine the relationship between HD and thrombogenicity, or bleeding events in patients undergoing percutaneous coronary intervention (PCI).

METHODS

In this retrospective cohort study, 300 patients undergoing elective PCI were enrolled between April 2017 and March 2019. Blood samples obtained on the day of PCI were analyzed with T-TAS to compute the thrombus formation area under the curve (AUC; PL₁₈-AUC₁₀ for platelet chip; AR₁₀-AUC₃₀ for atheroma chip). The patients were divided into three groups according to estimated glomerular filtration rate (eGFR): 33 HD patients, 124 non-HD patients with eGFR <60 mL/min/1.73m², and 143 non-HD patients with eGFR ≥60. We examined the thrombogenicity and spontaneous bleeding events within 1-year post-PCI.

RESULTS

HD was significantly associated with both low PL₁₈-AUC₁₀ and AR₁₀-AUC₃₀ levels determined by T-TAS. Bleeding events defined by the Bleeding Academic Research Consortium criteria types 2, 3, or 5 occurred during follow-up in 27 patients (9.0%): 7 in HD, 10 in non-HD with eGFR <60, and 10 in non-HD with eGFR ≥60. Both T-TAS parameters in the patients with bleeding were lower compared with those in the patients without bleeding, and HD was significantly associated with 1-year bleeding events.

CONCLUSIONS

The results suggested that HD patients undergoing PCI might be a predictor for low thrombogenicity measured by T-TAS and 1-year bleeding risk.

Development and assessment of total thrombus-formation analysis system-based bleeding risk model in patients undergoing percutaneous coronary intervention

BACKGROUND

Antithrombotic therapy is established for the treatment of various cardiovascular events. However, it has been shown to increase the bleeding risk. Total Thrombus-formation Analysis System (T-TAS) is reported to be useful for evaluating thrombogenicity. Here, we estimated whether T-TAS is useful for predicting bleeding events risk in patients undergoing percutaneous coronary intervention (PCI).

METHODS

This was a retrospective, observational study at Kumamoto University Hospital between April 2017 and March 2019. Blood samples obtained on the day of PCI were used in T-TAS to compute the thrombus formation area under the curve (AUC) (AR₁₀-AUC₃₀, AUC for AR chip). We divided the study population into 2 groups according to the Academic Research Consortium for High Bleeding Risk (ARC-HBR) (182 patients in ARC-HBR positive, 118 in ARC-HBR negative). The primary endpoint was 1-year bleeding events that were defined by Bleeding Academic Research Consortium type2, 3, or 5.

RESULTS

The AR₁₀-AUC₃₀levels were significantly lower in the ARC-HBR positive group than in the ARC-HBR negative group (median [interquartile range] 1571.4 [1277.0-1745.3] vs. 1726.2 [1567.7-1799.6], p < 0.001). The combination of ARC-HBR and AR₁₀-AUC₃₀ could discriminate the bleeding risk, and improved predictive capacity compared with ARC-HBR by c-statistics. Decision-curve analysis also revealed that combining AR₁₀-AUC₃₀ with ARC-HBR ameliorated bleeding risk-prediction. In multivariate Cox hazards analyses, combining ARC-HBR with lower AR₁₀-AUC₃₀ levels was significantly associated with 1-year bleeding events.

CONCLUSIONS

The results highlight that AR₁₀-AUC₃₀ evaluated by T-TAS could be a potentially useful marker for predicting high bleeding risk in patients undergoing PCI.

Advances in Platelet Function Testing-Light Transmission Aggregometry and Beyond

Platelet function testing is essential for the diagnosis of hemostasis disorders. While there are many methods used to test platelet function for research purposes, standardization is often lacking, limiting their use in clinical practice. Light transmission aggregometry has been the gold standard for over 60 years, with inherent challenges of working with live dynamic cells in specialized laboratories with independent protocols. In recent years, standardization efforts have brought forward fully automated systems that could lead to more widespread use. Additionally, new technical approaches appear promising for the future of specialized hematology laboratories. This review presents developments in platelet function testing for clinical applications.

Detection of acquired von Willebrand syndrome after ventricular assist device by total thrombus-formation analysis system

AIMS

Bleeding is a serious complication in patients with continuous-flow left ventricular assist device (CF-LVAD). Acquired von Willebrand syndrome (AVWS; type 2A) develops because of high shear stress inside the pumps and is a cause of bleeding complication. Although von Willebrand factor (vWF) multimer analysis is useful for diagnosing AVWS, it is only performed in specialized research institutes. A novel microchip flow chamber system, the total thrombus-formation analysis system (T-TAS), is a point-of-care system to evaluate the thrombus-formation process and useful for monitoring platelet thrombus-formation capacity in patients receiving antiplatelet therapy and the diagnosis and evaluation of the clinical severity of von Willebrand disease type 1. However, little is known about the association between AVWS and platelet thrombus-formation capacity evaluated by T-TAS in patients with CF-LVAD. We aimed to evaluate the utility of T-TAS for easy detection of AVWS in patients with CF-LVAD.

METHODS AND RESULTS

We simultaneously evaluated the vWF large multimers and T-TAS parameters in four consecutive patients with axial-type CF-LVAD and eight control patients treated with aspirin and warfarin. vWF large multimer index was defined as the proportion of large multimers in total vWF derived from a normal control plasma. T-TAS analyses different thrombus-formation processes using two microchips with different thrombogenic surfaces. PL₂₄ -AUC₁₀ levels in the platelet (PL) chip are highly sensitive for platelet functions, while AR₁₀ -AUC₃₀ levels in the atheroma (AR) chip allow the assessment of the overall haemostatic ability. vWF large multimer index and T-TAS parameters were decreased in all patients with CF-LVAD. The mean PL₂₄ -AUC₁₀ level (5.4 ± 2.9 vs. 219 ± 67; P < 0.01), AR₁₀ -AUC₃₀ level (338 ± 460 vs. 1604 ± 160; P < 0.01) and vWF large multimer index (49 ± 11% vs. 112 ± 27%; P < 0.01) were significantly lower in the patients with CF-LVAD than in control patients. One patient showed changes in T-TAS levels before and after implantation of CF-LVAD. PL₂₄ -AUC₁₀ and AR₁₀ -AUC₃₀ levels decreased from 438.1 to 5.0 and from 1667.9 to 1134.3, respectively.

CONCLUSIONS

In patients with CF-LVAD, the platelet thrombus-formation capacity was extremely impaired because of AVWS, and T-TAS parameters could detect the presence of AVWS. T-TAS can be used for easy detection of AVWS as a point-of-care testing. Further studies with a large sample size are needed to validate our results in several LVAD models and evaluate the prognostic value of bleeding complications and thromboembolism in patients with LVAD.

A New Preprocedural Score to Predict Bleeding Complications of Endovascular Interventions for Peripheral Artery Disease

Purpose: To investigate the bleeding complications associated with endovascular therapy (EVT) for peripheral artery disease (PAD) and develop a dedicated peripheral bleeding score (PBS). Materials and Methods: This prospective, single-center study enrolled 530 patients (mean age 67.6±9.8 years; 396 men) undergoing endovascular procedures between August 2016 and July 2018 for chronic PAD. Primary endpoints were the incidence of 30-day bleeding complications [minor and major (prolonging hospitalization, causing permanent sequelae, or resulting in death)], the identification of factors associated with bleeding events, and the development of a dedicated PBS based on univariate and multivariate analysis. Hazard ratios (HR) and 95% confidence intervals (CI) are reported. The HAS-BLED score was compared with the PBS. Results: The overall peripheral bleeding complication rate was 3.8% (20/530), of which 3.2% (17/530) were major and included 4 (0.7%) active retroperitoneal bleeding events and 13 (2.4%) pseudoaneurysms. The annualized incidences of overall bleeding and major bleeding complications were 1.9% and 1.6%, respectively. Multivariable regression analysis identified age ≥75 as a correlate of significantly increased bleeding risk (HR 3.32, 95% CI 1.12 to 9.80, p<0.02). Male gender (HR 0.193, 95% CI 0.49 to 0.75, p<0.001) and statin therapy (HR 0.245, 95% CI 0.08 to 0.71, p=0.01) were correlated with a significantly decreased bleeding risk. Based on the regression analysis findings an 8-point PBS was developed, demonstrating 75.0% sensitivity and 78.4% specificity in detecting bleeding complications. The HAS-BLED score failed to identify 30-day bleeding events. Conclusion: The annualized incidence of bleeding complications associated with peripheral EVT was low. Advanced age and female sex were correlated with increased bleeding risk. The PBS demonstrated satisfactory statistical performance and could be considered for inclusion in the preprocedural endovascular checklist to help optimize intra- and postprocedural care.

Total Thrombus-Formation Analysis System can Predict 1-Year Bleeding Events in Patients with Coronary Artery Disease

Aims: The assessment of bleeding risk in patients with coronary artery disease (CAD) is clinically important. We recently developed the Total Thrombus-Formation Analysis System (T-TAS) for the quantitative analysis of thrombus formation using microchips with thrombogenic surfaces. Here, we assessed the utility of T-TAS parameters in predicting 1-year bleeding events in patients with CAD.

Methods: The study subjects were 561 consecutive patients who underwent coronary angiography (CAG) between August 2013 and September 2016 for suspected CAD. Blood samples collected at the time of CAG were used for T-TAS to compute the area under the curve (AUC) (AR₁₀-AUC₃₀) in the AR chip. Patients were divided into three groups according to AR₁₀-AUC₃₀ (low: ≤ 1603, intermediate, and high: > 1765, n = 187 each). One-year bleeding events were defined by the Platelet Inhibition and Patient Outcomes criteria.

Results: Bleeding occurred in 21 (3.7%) patients and was classified as major (8 [1.4%]) and minor (13 [2.3%]). The AR₁₀-AUC₃₀ levels were significantly lower in the bleeding group than the non-bleeding group (median [interquartile range] 1590 [1442–1734] vs. 1687 [1546–1797], p = 0.04). Univariate Cox regression analysis demonstrated that low AR₁₀-AUC₃₀, high prothrombin time-international normalized ratio levels, and diabetes correlated with bleeding events. Multivariate Cox regression analysis identified low AR₁₀-AUC₃₀ levels as a significant determinant of bleeding events. Kaplan-Meier survival curves showed a higher rate of bleeding events in the low than the high AR₁₀-AUC₃₀ group (p = 0.007).

Conclusions: The results highlight the potential usefulness of the AR₁₀-AUC₃₀ levels in the prediction of 1-year bleeding events in patients with CAD treated with various antithrombotic therapies.

Reduction in thrombogenic activity and thrombocytopenia after transcatheter aortic valve implantation - The ATTRACTIVE-TTAS study

Introduction

Bleeding complications after transcatheter aortic valve implantation (TAVI) is a major problem in clinical practice. However, there is few information on thrombogenicity after TAVI. The aim of this study was to establish a monitoring of total thrombogenicity in perioperative TAVI using the Total Thrombus-formation Analysis System (T-TAS), a microchip-based flow chamber system for analysis of thrombus formation under flow condition.

Methods

Twenty-three patients with severe aortic stenosis who underwent TAVI between August 2017 and March 2018 at Kumamoto university hospital were enrolled. After exclusion, data of 21 patients were analyzed. Blood samples were obtained before, 2, 7, and 30 days after TAVI. Thrombogenicity were assessed by the T-TAS to compute the area under the curve (AUC) (AR₁₀-AUC₃₀) in the AR chip. We also measured platelet count, high-molecular-weight von Willebrand factor (HMW-vWF) multimers, and plasma thrombopoietin. Computational fluid dynamics (CFD) analysis was performed to calculate the wall shear stress (WSS).

Results

The AR₁₀-AUC₃₀ levels and platelet counts were significantly lower at 2 days post-TAVI, and then increased gradually. HMW-vWF multimers, and plasma thrombopoietin, were significantly higher at 2 days post-TAVI, compared with before TAVI. CFD analysis showed that WSS of the aortic valve and posterior ascending aortic wall were significantly lower after TAVI than before-TAVI. Multivariate analysis identified max velocity measured by echocardiography, platelet count, and D-dimer as significant determinants of AR₁₀-AUC₃₀, representing total thrombogenicity.

Conclusions

Although HMW-vWF multimers improved earlier after TAVI, total thrombogenic activity evaluated by T-TAS remained relatively low followed by improvement in thrombogenic activity at 30 days after TAVI.Clinical Trial Registration: https://clinicaltrials.gov. Unique identifiers: NCT03248232.

Inhibitory mechanisms of very low-dose rivaroxaban in non-ST-elevation myocardial infarction

Very low-dose (VLD) factor Xa (FXa) inhibition, in combination with acetylsalicylic acid (ASA) and clopidogrel, is associated with improved outcomes in patients with acute coronary syndrome (ACS) with a tolerable bleeding risk profile. To date, there are no data documenting platelet inhibition and the anticoagulatory effects of VLD FXa inhibition on top of guideline-adherent dual-antiplatelet therapy (DAPT) in patients with ACS. Patients with non-ST-elevation myocardial infarction (NSTEMI) receiving oral DAPT (ASA + clopidogrel, n = 20; or ASA + ticagrelor, n = 20) were prospectively enrolled in a nonrandomized study. Coagulation- and platelet-dependent thrombin generation (TG), measured by means of the calibrated automated thrombogram, were significantly decreased after in vitro and in vivo addition of rivaroxaban. As shown by a total thrombus-formation analysis approach, rivaroxaban treatment led to a significantly decreased coagulation-dependent (AR-chip) thrombus formation in patients treated with ASA plus P2Y₁₂ inhibitor (clopidogrel/ticagrelor), whereas the pure platelet-dependent (PL-chip) thrombus formation was not affected at all. Adjunctive rivaroxaban therapy was not associated with significant differences in platelet aggregation assessed by light-transmission aggregometry (LTA). Nevertheless, according to fluorescence-activated cell sorter analysis, VLD rivaroxaban treatment resulted in a significantly reduced expression of platelet HMGB-1, whereas P-selectin exposure was not affected. Furthermore, an enhanced effect of rivaroxaban on total thrombus formation and TG was observed in particular in clopidogrel nonresponder patients defined as adenosine 5'-diphosphate-induced LTA ≥40%. VLD rivaroxaban reduces thrombus formation and platelet-dependent TG in patients with ACS receiving DAPT, which can be of potential ischemic benefit. This trial was registered at www.clinicaltrials.gov as #NCT01417884.

Microfluidics contrasted to thrombelastography: perplexities in defining hypercoagulability

BACKGROUND

Elevated clot strength (maximum amplitude [MA]) measured by thrombelastography (TEG) is associated with thrombotic complications. However, it remains unclear how MA translates to thrombotic risks, as this measurement is independent of time, blood flow, and clot degradation. We hypothesize that under flow conditions, increased clot strength correlates to time-dependent measurements of coagulation and resistance to fibrinolysis.

MATERIALS AND METHODS

Surgical patients at high risk of thrombotic complications were analyzed with TEG and total thrombus-formation analysis system (T-TAS). TEG hypercoagulability was defined as an r <10.2 min, angle >59, MA >66 or LY30 <0.2% (based off of healthy control data, n = 141). The T-TAS AR and PL chips were used to measure clotting at arterial shear rates. T-TAS measurements include occlusion start time, occlusion time (OT), occlusion speed (OSp), and total clot generation (area under the curve). These measurements were correlated to TEG indices (R time, angle, MA, and LY30). Both T-TAS and TEG assays were challenged with tissue plasminogen activator (t-PA) to assess clot resistance to fibrinolysis.

RESULTS

Thirty subjects were analyzed, including five controls. TEG-defined hypercoagulability by MA was detected in 52% of the inflammatory bowel disease/cancer patients; 0% was detected in the controls. There were no TEG measurements that significantly correlated with T-TAS AR and PL chip. However, in the presence of t-PA, T-TAS AR determined OSp to have an inverse relationship with TEG angle (-0.477, P = 0.012) and LY30 (-0.449, P = 0.019), and a positive correlation with R time (0.441 P = 0.021). In hypercoagulability determined by TEG MA, T-TAS PL had a significantly reduced OT (4:07 versus 6:27 min, P = 0.043). In hypercoagulability defined by TEG LY30, T-TAS PL had discordant findings, with a significantly prolonged OT (6:36 versus 4:30 min, P = 0.044) and a slower OSp (10.5 versus 19.0 kPa/min, P = 0.030).

CONCLUSIONS

Microfluidic coagulation assessment with T-TAS has an overall poor correlation with most TEG measurements in a predominantly hypercoagulable patient population, except in the presence of t-PA. The one anticipated finding was an elevated MA having a shorter time to platelet-mediated microfluidic occlusion, supporting the role of platelets and hypercoagulability. However, hypercoagulability defined by LY30 had opposing results in which a low LY30 was associated with a longer PL time to occlusion and slower OSp. These discordant findings warrant ongoing investigation into the relationship between clot strength and fibrinolysis under different flow conditions.

Coronary blood flow volume change is negatively associated with platelet aggregability in patients with non-obstructive ischemic heart disease who have no anti-platelet agents

BACKGROUND

Thrombus formation is one of the main pathogeneses of acute coronary syndrome with atherosclerotic rupture. Previous studies have reported that atherosclerosis increases platelet aggregability and that vascular endothelial dysfunction reflects early change of atherosclerosis. However, the relationship between coronary endothelial dysfunction and platelet reactivity remains unclear. Therefore, in this study, we investigated the relationship between them in non-obstructive ischemic heart disease (IHD) patients.

METHODS

Three hundred sixty-eight consecutive stable patients with suspected angina presenting non-obstructive coronary arteries (<50% diameter) in coronary angiography were investigated with the intracoronary acetylcholine provocation test and measured adenosine triphosphate-induced coronary flow reserve. Finally, 25 non-obstructive IHD patients who had no anti-platelet agents were assessed for the relationship between coronary blood flow volume (CBFV) change and platelet aggregability as P2Y12 reaction unit (PRU) by VerifyNow P2Y12 assay system.

RESULTS

CBFV change by intracoronary 20 μg/kg per minute acetylcholine provocation showed a significant negative correlation with platelet aggregability as PRU (r = 0.44, P = 0.03). Conversely, there was no significant correlation between PRU and endothelial function as coronary flow reserve. Furthermore, multivariable linear regression analysis indicated that an incremental CBFV change was independently associated with PRU (β = 0.63, P < 0.001) in non-obstructive IHD patients.

CONCLUSIONS

In patients with non-obstructive IHD, CBFV change was significantly associated with platelet aggregability, indicating that coronary endothelial dysfunction might mediate higher platelet aggregability.

Elastomeric microvalve geometry affects haemocompatibility

This paper reports on the parameters that determine the haemocompatibility of elastomeric microvalves for blood handling in microfluidic systems. Using a comprehensive investigation of blood function, we describe a hierarchy of haemocompatibility as a function of microvalve geometry and identify a "normally-closed" v-gate pneumatic microvalve design that minimally affects blood plasma fibrinogen and von Willebrand factor composition, minimises effects on erythrocyte structure and function, and limits effects on platelet activation and aggregation, while facilitating rapid switching control for blood sample delivery. We propose that the haemodynamic profile of valve gate geometries is a significant determinant of platelet-dependent biofouling and haemocompatibility. Overall our findings suggest that modification of microvalve gate geometry and consequently haemodynamic profile can improve haemocompatibility, while minimising the requirement for chemical or protein modification of microfluidic surfaces. This biological insight and approach may be harnessed to inform future haemocompatible microfluidic valve and component design, and is an advance towards lab-on-chip automation for blood based diagnostic systems.

Edoxaban Enhances Thromboprophylaxis by Physiotherapy After Total Knee Arthroplasty - The Randomized Controlled ESCORT-TKA Trial

BACKGROUND

The pharmacological advantage of combining physiotherapy with anticoagulants for the prevention of venous thromboembolism (VTE) after total knee arthroplasty (TKA) is not fully known. Herein we investigated the potential benefit of this combination therapy in patients undergoing TKA.

METHODS AND RESULTS

The 38 patients were randomly assigned to a physiotherapy group (n=19) or a physiotherapy plus 30 mg/day edoxaban group (n=19). The occurrence of VTE was evaluated, as were serial changes in parameters measured by the Total Thrombus-formation Analysis System, a novel system for quantitatively analyzing thrombus formation using microchips with thrombogenic surfaces (collagen plus tissue factor, atheroma [AR]-chip). Combination therapy significantly reduced the incidence of VTE after TKA compared with monotherapy (P=0.038). The area under the curve (AUC) of thrombus formation for the AR-chip (AR10-AUC30) was significantly lower in the combination group (P=0.001) on Day 7 after TKA than before TKA, but no significant change was observed with monotherapy (P=0.809). In 13 VTE-positive patients, AR10-AUC30was significantly lower in the combination group (n=3) than in the monotherapy group (n=10) on Day 7 (P=0.045).

CONCLUSIONS

The combination of physiotherapy and edoxaban significantly reduced the incidence of VTE after TKA compared with physiotherapy alone. However, it is possible that VTE occurrence after TKA is not only associated with thrombogenicity, but also rheological factors.