Principles of Dielectric Blood Coagulometry as a Comprehensive Coagulation Test

Pathophysiology of acute graft-versus-host disease from the perspective of hemodynamics determined by dielectric analysis

BACKGROUND

Numerous reports have demonstrated that the pathophysiology of graft-versus-host disease (GVHD) during hematopoietic stem cell transplantation (HSCT) is closely related to vascular endothelial disorders and coagulation abnormalities. We previously presented the discovery of a principle and the development of a novel instrument for measuring whole blood coagulation. This was achieved by assessing the variations in the dielectric properties of whole blood.

AIM

To investigate how GVHD affects the changes of dielectric properties of whole blood in patients with HSCT.

METHODS

We examined the changes of dielectric properties of whole blood and erythrocyte proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis sequentially in patients with HSCT and compared it with clinical symptoms and inflammatory parameters of GVHD.

RESULTS

During severe GVHD, the dielectric relaxation strength markedly increased and expression of band3 decreased. The dielectric relaxation strength normalized with the improvement of GVHD. In vitro analysis confirmed that the increase of relaxation strength was associated with severe erythrocyte aggregates, but not with decreased expression of band3.

CONCLUSION

Severe erythrocyte aggregates observed in GVHD may cause coagulation abnor malities and circulatory failure, which, together with the irreversible erythrocyte dysfunction we recently reported, could lead to organ failure.

Edoxaban eliminates hypercoagulability evoked by transient temperature changes in human whole blood

Background

Thrombosis is a common critical complication relating to radiofrequency catheter ablation and cryoablation. There is a possibility that high-temperature stimulation during radiofrequency ablation or low-temperature stimulation during cryoablation may affect the coagulability of blood. In this study, we aimed to determine the impacts of transient temperature stimulations on the coagulability of whole blood and to clarify if edoxaban suppressed the hypercoagulability.

Methods

Citrated blood samples were drawn from 41 healthy subjects. Some blood samples were mixed with tissue factor (TF) and several concentrations of edoxaban (50, 100, and 200 ng/mL). Blood samples were exposed to several temperature stimulations for 1 min: heat stimulation (50°C) or cryostimulation (-20°C), and compared with control (37°C). Repeated cryostimulations or sequential cryo- and heat stimulation were also applied. Coagulability of whole blood was measured using a dielectric blood coagulometry. As an index of coagulability, the end of acceleration time (EAT) was used.

Results

Both heat- and cryostimulations significantly shortened the EAT compared to the control, indicating that hypercoagulability was induced by temperature stimulations. Application of TF enhanced and extended the hypercoagulability after the temperature stimulations. Sequential application of cryo- followed by heat stimulation further enhanced the hypercoagulability of blood. Application of edoxaban increased the EAT in a concentration-dependent manner in control condition. Edoxaban at 100 or 200 ng/mL completely suppressed the shortening of EAT evoked by these temperature stimulations.

Conclusion

Transient temperature stimulations evoked hypercoagulability regardless of cryo- or heat stimulation. Edoxaban with 100 ng/mL or more eliminated this temperature-stimulated hypercoagulability.

A Multichannel Portable Platform With Embedded Thermal Management for Miniaturized Dielectric Blood Coagulometry

This article presents a standalone, multichannel, miniaturized impedance analyzer (MIA) system for dielectric blood coagulometry measurements with a microfluidic sensor termed ClotChip. The system incorporates a front-end interface board for 4-channel impedance measurements at an excitation frequency of 1 MHz, an integrated resistive heater formed by a pair of printed-circuit board (PCB) traces to keep the blood sample near a physiologic temperature of 37 °C, a software-defined instrument module for signal generation and data acquisition, and a Raspberry Pi-based embedded computer with 7-inch touchscreen display for signal processing and user interface. When measuring fixed test impedances across all four channels, the MIA system exhibits an excellent agreement with a benchtop impedance analyzer, with rms errors of ≤0.30% over a capacitance range of 47-330 pF and ≤0.35% over a conductance range of 2.13-10 mS. Using in vitro-modified human whole blood samples, the two ClotChip output parameters, namely, the time to reach a permittivity peak (Tpeak) and maximum change in permittivity after the peak (Δϵr,max) are assessed by the MIA system and benchmarked against the corresponding parameters of a rotational thromboelastometry (ROTEM) assay. Tpeak exhibits a very strong positive correlation (r = 0.98, p < 10-6, n = 20) with the ROTEM clotting time (CT) parameter, while Δϵr,max exhibits a very strong positive correlation (r = 0.92, p < 10-6, n = 20) with the ROTEM maximum clot firmness (MCF) parameter. This work shows the potential of the MIA system as a standalone, multichannel, portable platform for comprehensive assessment of hemostasis at the point-of-care/point-of-injury (POC/POI).

Bioimpedance Analysis as Early Predictor for Clot Formation Inside a Blood-Perfused Test Chamber: Proof of Concept Using an In Vitro Test-Circuit

Clot formation inside a membrane oxygenator (MO) due to blood-to-foreign surface interaction represents a frequent complication during extracorporeal membrane oxygenation. Since current standard monitoring methods of coagulation status inside the MO fail to detect clot formation at an early stage, reliable sensors for early clot detection are in demand to reduce associated complications and adverse events. Bioimpedance analysis offers a monitoring concept by integrating sensor fibers into the MO. Herein, the feasibility of clot detection via bioimpedance analysis is evaluated. A custom-made test chamber with integrated titanium fibers acting as sensors was perfused with heparinized human whole blood in an in vitro test circuit until clot formation occurred. The clot detection capability of bioimpedance analysis was directly compared to the pressure difference across the test chamber (ΔP-TC), analogous to the measurement across MOs (ΔP-MO), the clinical gold standard for clot detection. We found that bioimpedance measurement increased significantly 8 min prior to a significant increase in ΔP-TC, indicating fulminant clot formation. Experiments without clot formation resulted in a lack of increase in bioimpedance or ΔP-TC. This study shows that clot detection via bioimpedance analysis under flow conditions in a blood-perfused test chamber is generally feasible, thus paving the way for further investigation.

Evaluation of fibrinogen concentration by clot firmness using a dielectric blood coagulation test system

PURPOSE

To determine if fibrinogen concentration can be evaluated by dielectric permittivity changes in dielectric blood coagulation testing (DBCM) during cardiovascular surgery with cardiopulmonary bypass (CPB).

METHODS

We performed a single-center prospective observational study at a university hospital. One hundred patients undergoing cardiovascular surgery with CPB were enrolled. Whole-blood samples were obtained after weaning from CPB, and dielectric clot strength (DCS) was measured by intrinsic pathway testing with or without heparinase in DBCM. The FIBTEM test was performed during rotational thromboelastometry using the same samples, and maximum clot firmness (MCF) was evaluated. Spearman's correlation analysis was performed, and receiver operating characteristics (ROC) curve analyses were used to evaluate the performance of hypofibrinogenemia detection.

RESULTS

DCS showed a strong positive correlation with plasma fibrinogen concentration (Rs = 0.76, P < 0.0001). The area under the ROC curve for evaluating plasma fibrinogen concentration < 200 mg/dL was 0.91 (95% confidence interval (CI) 0.85-0.97) for DCS, compared with 0.88 (95% CI 0.81-0.94) for FIBTEM MCF. The optimal cutoff value of DCS was 17.0 (sensitivity 94%, specificity 80%).

CONCLUSIONS

DCS variables showed a significantly strong correlation with plasma fibrinogen concentration, and the diagnostic performance for hypofibrinogenemia was comparable to that for FIBTEM MCF. This novel methodology has the potential to provide a point-of-care test with sufficient accuracy for the detection of perioperative hypofibrinogenemia during cardiovascular surgery with CPB.

Blood clot contraction: Mechanisms, pathophysiology, and disease

A State of the Art lecture titled "Blood Clot Contraction: Mechanisms, Pathophysiology, and Disease" was presented at the International Society on Thrombosis and Haemostasis (ISTH) Congress in 2022. This was a systematic description of blood clot contraction or retraction, driven by activated platelets and causing compaction of the fibrin network along with compression of the embedded erythrocytes. The consequences of clot contraction include redistribution of the fibrin-platelet meshwork toward the periphery of the clot and condensation of erythrocytes in the core, followed by their deformation from the biconcave shape into polyhedral cells (polyhedrocytes). These structural signatures of contraction have been found in ex vivo thrombi derived from various locations, which indicated that clots undergo intravital contraction within the blood vessels. In hemostatic clots, tightly packed polyhedrocytes make a nearly impermeable seal that stems bleeding and is impaired in hemorrhagic disorders. In thrombosis, contraction facilitates the local blood flow by decreasing thrombus obstructiveness, reducing permeability, and changing susceptibility to fibrinolytic enzymes. However, in (pro)thrombotic conditions, continuous background platelet activation is followed by platelet exhaustion, refractoriness, and impaired intravital clot contraction, which is associated with weaker thrombi predisposed to embolization. Therefore, assays that detect imperfect in vitro clot contraction have potential diagnostic and prognostic values for imminent or ongoing thrombosis and thrombotic embolism. Collectively, the contraction of blood clots and thrombi is an underappreciated and understudied process that has a pathogenic and clinical significance in bleeding and thrombosis of various etiologies. Finally, we have summarized relevant new data on this topic presented during the 2022 ISTH Congress.

Assessment of fibrinolytic status in whole blood using a dielectric coagulometry microsensor

Rapid assessment of the fibrinolytic status in whole blood at the point-of-care/point-of-injury (POC/POI) is clinically important to guide timely management of uncontrolled bleeding in patients suffering from hyperfibrinolysis after a traumatic injury. In this work, we present a three-dimensional, parallel-plate, capacitive sensor - termed ClotChip - that measures the temporal variation in the real part of blood dielectric permittivity at 1 MHz as the sample undergoes coagulation within a microfluidic channel with <10 μL of total volume. The ClotChip sensor features two distinct readout parameters, namely, lysis time (LT) and maximum lysis rate (MLR) that are shown to be sensitive to the fibrinolytic status in whole blood. Specifically, LT identifies the time that it takes from the onset of coagulation for the fibrin clot to mostly dissolve in the blood sample during fibrinolysis, whereas MLR captures the rate of fibrin clot lysis. Our findings are validated through correlative measurements with a rotational thromboelastometry (ROTEM) assay of clot viscoelasticity, qualitative/quantitative assessments of clot stability, and scanning electron microscope imaging of clot ultrastructural changes, all in a tissue plasminogen activator (tPA)-induced fibrinolytic environment. Moreover, we demonstrate the ClotChip sensor ability to detect the hemostatic rescue that occurs when the tPA-induced upregulated fibrinolysis is inhibited by addition of tranexamic acid (TXA) - a potent antifibrinolytic drug. This work demonstrates the potential of ClotChip as a diagnostic platform for rapid POC/POI assessment of fibrinolysis-related hemostatic abnormalities in whole blood to guide therapy.

Simultaneous electrical online estimation of changes in blood hematocrit and temperature in cardiopulmonary bypass

Two equations have been developed from multi-frequency measurements of blood impedance Z_b for a simultaneous electrical online estimation of changes in blood hematocrit ΔH [%] and temperatures ΔT [K] in cardiopulmonary bypass (CPB). Z_b of fixed blood volumes at varying H and T were measured by an impedance analyzer and changes in blood conductivity σ_b and relative permittivity ε_b computed. Correlation analysis were based on changes in σ_b with H or T at f = 1 MHz while H and T equations were developed by correlating changes in ε_b with H and T at dual frequencies of f = 1 MHz and f = 10 MHz which best capture blood plasma Z_p and red blood cell cytoplasm Z_cyt impedances respectively. Results show high correlations between σ_b and H (R² = 0.987) or σ_b and T (R² = 0.9959) indicating dependence of the electrical parameters of blood on its H and T. Based on computed ε_b, changes in blood hematocrit ΔH and temperature ΔT at a given time t are estimated as ΔH(t) = 1.7298Δε_b (f = 1 MHz) - 1.0669Δε_b (f = 10 MHz) and ΔT(t) = -2.186Δε_b (f = 1 MHz) + 2.13Δε_b (f = 10 MHz). When applied to a CPB during a canine mitral valve plasty, ΔH and ΔT had correlations of R² = 0.9992 and R² = 0.966 against H and T respectively as measured by conventional devices.

Simultaneous multiparameter whole blood hemostasis assessment using a carbon nanotube-paper composite capacitance sensor

Rapid and accurate clinical assessment of hemostasis is essential for managing patients who undergo invasive procedures, experience hemorrhages, or receive antithrombotic therapies. Hemostasis encompasses an ensemble of interactions between the cellular and non-cellular blood components, but current devices assess only partial aspects of this complex process. In this work, we describe the development of a new approach to simultaneously evaluate coagulation function, platelet count or function, and hematocrit using a carbon nanotube-paper composite (CPC) capacitance sensor. CPC capacitance response to blood clotting at 1.3 MHz provided three sensing parameters with distinctive sensitivities towards multiple clotting elements. Whole blood-based hemostasis assessments were conducted to demonstrate the potential utility of the developed sensor for various hemostatic conditions, including pathological conditions, such as hemophilia and thrombocytopenia. Results showed good agreements when compared to a conventional thromboelastography. Overall, the presented CPC capacitance sensor is a promising new biomedical device for convenient non-contact whole-blood based comprehensive hemostasis evaluation.

Dielectric Blood Coagulometry for the Early Detection of Sepsis-Induced Disseminated Intravascular Coagulation: A Prospective Observational Study

OBJECTIVES

To evaluate the utility of dielectric blood coagulometry for early sepsis-induced disseminated intravascular coagulation diagnosis.

DESIGN

Single-center, prospective observational study.

SETTING

Patients with sepsis or septic shock at the Tokyo Medical and Dental University Hospital of Medicine between September 2019 and September 2020.

PATIENTS

The patients were divided into three groups according to the timing of disseminated intravascular coagulation diagnosis based on the Disseminated Intravascular Coagulation score by the Japanese Association for Acute Medicine: 1) no disseminated intravascular coagulation group, 2) late-diagnosed disseminated intravascular coagulation group: not diagnosed with disseminated intravascular coagulation on day 1 but diagnosed within 48 hours after admission, and 3) disseminated intravascular coagulation group: diagnosed with disseminated intravascular coagulation on day 1. The study evaluated 80 patients (no disseminated intravascular coagulation, 31 [38.8%]; late-diagnosed disseminated intravascular coagulation, 34 (42.5%); disseminated intravascular coagulation, 15 [18.8%]).

MEASUREMENTS AND MAIN RESULTS

We compared the clinical severity scores and mortality of the groups and assessed the correlation between the dielectric blood coagulometry-derived coagulation marker, thrombin levels, and Disseminated Intravascular Coagulation score using Spearman rank correlation. The mortality rate was 0% (0/31) in the no disseminated intravascular coagulation group, 35.3% (12/34) in the late-diagnosed disseminated intravascular coagulation group, and 33.3% (5/15) in the disseminated intravascular coagulation group. Although the Disseminated Intravascular Coagulation score on day 1 did not reflect disseminated intravascular coagulation in approximately 70% of patients who developed disseminated intravascular coagulation by day 2, dielectric clot strength measured by dielectric blood coagulometry on day 1 strongly correlated with disseminated intravascular coagulation development by day 2 (Spearman ρ = 0.824; p < 0.05) and with thrombin level on day 1 (Spearman ρ = 0.844; p < 0.05).

CONCLUSIONS

Dielectric blood coagulometry can be used to detect early-phase disseminated intravascular coagulation in patients with sepsis and is strongly correlated with thrombin levels. Larger studies are needed to verify our results for developing clinical applications.

Connector sensors for permittivity-based thrombus monitoring in extracorporeal life support

Extracorporeal circulation is vital in cardiovascular surgery, but thrombus formation at connector interface is a major threat. Optical coherence tomography (OCT) is presently used to monitor thrombogenesis at connectors, but it is expensive to install and complex to use. This study fabricated and evaluated a connector sensor for real-time permittivity-based thrombus monitoring at tube-connector interface. Computational simulations were initially done to pre-evaluate the applicability of connector sensor. The sensor was fabricated by incorporating two stainless steel electrodes on acrylic tube for measuring permittivity changes at the tube-connector interface. OCT images were also taken from the interface at intervals for comparisons. Results show that the sensor was able to detect thrombus formation at the interface in form of sudden rise in permittivity after time t = 9 min. The permittivity changes were confirmed by OCT images which showed thrombus formation after time t = 14 min implying that permittivity changes were due to regional aggregation of red blood cells. The connector sensor is therefore envisioned as an affordable alternative to OCT for real-time permittivity-based monitoring of thrombogenesis at tube-connector interface.

Electrochemical Impedance Characterization of Blood Cell Suspensions. Part 1: Basic Theory and Application to Two-Phase Systems

Electrochemical impedance spectra of composite materials contain information on the topological arrangement, volume fraction, and shape of particles, as well as the dielectric properties of the matrix and particles. The objective of this study is to investigate how these parameters affect the dielectric spectrum and what reliable information can be extracted from experimental data. The main attention was focused on systems with dielectric behavior similar to that of human blood. Mostly plasma and erythrocytes determine the dielectric properties of whole blood. Erythrocytes suspended in plasma can be considered as three-phase systems with single-shelled particles. A theoretical approach based on the effective medium theory is developed for calculating the effective permittivity and conductivity of three-phase composites at a wide frequency range (from 0 to 1 GHz). A finite-difference method is applied to model three-dimensional periodic structures. A special case of two-phase materials is used to demonstrate the influence of the shape and arrangement of particles on dielectric properties. Theoretical and numerical approaches are applied to two-phase composites with spherical, spheroidal and biconcave particles and are compared with each other and with published data. It is shown that two-phase composites exhibit only β-dispersion. In contrast to the quasi-static limit, the wide-bandwidth impedance spectroscopy makes it possible to distinguish between disordered and regular arrangements of spheroidal and biconcave particles. The results can be used to analyze the dielectric properties of blood, which is very promising for various medical applications. This study of two-phase composites can be further extended to three-phase composites.

Differential Assessment of Factor Xa Activity and Global Blood Coagulability Utilizing Novel Dielectric Coagulometry

An easy-to-use assessment for activated factor X (FXa) is lacking despite its pivotal role in the coagulation. Dielectric blood coagulometry (DBCM) was recently invented as a novel assessment tool for determining the whole blood coagulability by measuring the temporal change in the permittivity of blood. We previously reported that it could evaluate the global blood coagulability. This study aimed to apply the DBCM for assessing FXa activity and its inhibition by anticoagulants. We performed the DBCM analysis along with measurement of the FXa activity by a fluorometric assay in samples from healthy subjects, and identified a new index named maximum acceleration time (MAT) that had a correlation to the FXa activity. Next the DBCM analysis was performed using blood samples mixed with anticoagulants (unfractionated heparin, dalteparin, and edoxaban). Blood samples with three anticoagulants had different profiles of the temporal change in the permittivity, reflecting their different selectivity for FXa. We compared the MAT with the anti-FXa activity assay, and found that the prolongation of MAT was similarly correlated with the anti-FXa activity regardless of the type of anticoagulants. In conclusion, the DBCM has the possibility for evaluating the innate FXa activity and effect of anticoagulants focusing on their FXa inhibition.

Assessment of whole blood coagulation with a microfluidic dielectric sensor

Essentials ClotChip is a novel microsensor for comprehensive assessment of ex vivo hemostasis. Clinical samples show high sensitivity to detecting the entire hemostatic process. ClotChip readout exhibits distinct information on coagulation factor and platelet abnormalities. ClotChip has potential as a point-of-care platform for comprehensive hemostatic analysis.

SUMMARY

Background Rapid point-of-care (POC) assessment of hemostasis is clinically important in patients with a variety of coagulation factor and platelet defects who have bleeding disorders. Objective To evaluate a novel dielectric microsensor, termed ClotChip, which is based on the electrical technique of dielectric spectroscopy for rapid, comprehensive assessment of whole blood coagulation. Methods The ClotChip is a three-dimensional, parallel-plate, capacitive sensor integrated into a single-use microfluidic channel with miniscule sample volume (< 10 μL). The ClotChip readout is defined as the temporal variation in the real part of dielectric permittivity of whole blood at 1 MHz. Results The ClotChip readout exhibits two distinct parameters, namely, the time to reach a permittivity peak (Tpeak ) and the maximum change in permittivity after the peak (Δεr,max ), which are, respectively, sensitive towards detecting non-cellular (i.e. coagulation factor) and cellular (i.e. platelet) abnormalities in the hemostatic process. We evaluated the performance of ClotChip using clinical blood samples from 15 healthy volunteers and 12 patients suffering from coagulation defects. The ClotChip Tpeak parameter exhibited superior sensitivity at distinguishing coagulation disorders as compared with conventional screening coagulation tests. Moreover, the ClotChip Δεr,max parameter detected platelet function inhibition induced by aspirin and exhibited strong positive correlation with light transmission aggregometry. Conclusions This study demonstrates that ClotChip assesses multiple aspects of the hemostatic process in whole blood on a single disposable cartridge, highlighting its potential as a POC platform for rapid, comprehensive hemostatic analysis.

Simultaneous assessment of blood coagulation and hematocrit levels in dielectric blood coagulometry

BACKGROUND

In a whole blood coagulation test, the concentration of any in vitro diagnostic agent in plasma is dependent on the hematocrit level but its impact on the test result is unknown.

OBJECTIVE

The aim of this work was to clarify the effects of reagent concentration, particularly Ca2+, and to find a method for hematocrit estimation compatible with the coagulation test.

METHODS

Whole blood coagulation tests by dielectric blood coagulometry (DBCM) and rotational thromboelastometry were performed with various concentrations of Ca2+ or on samples with different hematocrit levels. DBCM data from a previous clinical study of patients who underwent total knee arthroplasty were re-analyzed.

RESULTS

Clear Ca2+ concentration and hematocrit level dependences of the characteristic times of blood coagulation were observed. Rouleau formation made hematocrit estimation difficult in DBCM, but use of permittivity at around 3 MHz made it possible. The re-analyzed clinical data showed a good correlation between permittivity at 3 MHz and hematocrit level (R2=0.83).

CONCLUSIONS

Changes in the hematocrit level may affect whole blood coagulation tests. DBCM has the potential to overcome this effect with some automated correction using results from simultaneous evaluations of the hematocrit level and blood coagulability.

ClotChip: A Microfluidic Dielectric Sensor for Point-of-Care Assessment of Hemostasis

This paper describes the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy of human whole blood during coagulation. The sensor, termed ClotChip, employs a three-dimensional, parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Interfaced with an impedance analyzer, the ClotChip measures the complex relative dielectric permittivity, ϵ_r , of human whole blood in the frequency range of 40 Hz to 100 MHz. The temporal variation in the real part of the blood dielectric permittivity at 1 MHz features a time to reach a permittivity peak, , as well as a maximum change in permittivity after the peak, , as two distinct parameters of ClotChip readout. The ClotChip performance was benchmarked against rotational thromboelastometry (ROTEM) to evaluate the clinical utility of its readout parameters in capturing the clotting dynamics arising from coagulation factors and platelet activity. exhibited a very strong positive correlation ( r = 0.99, p < 0.0001) with the ROTEM clotting time parameter, whereas exhibited a strong positive correlation (r = 0.85,  p < 0.001) with the ROTEM maximum clot firmness parameter. This paper demonstrates the ClotChip potential as a point-of-care platform to assess the complete hemostatic process using <10 μL of human whole blood.

The use of dielectric blood coagulometry in the evaluation of coagulability in patients with peripheral arterial disease

Background

Platelets and coagulation proteins contribute to the development of peripheral arterial disease, especially atherosclerotic disease. Several experimental studies have proven a significant correlation between hypercoagulability and atherosclerosis. We used dielectric blood coagulometry, which was initially designed to evaluate the coagulable status, to examine the coagulability of peripheral arterial disease patients, and investigated the factors that were significantly correlated with the results.

Methods

We performed dielectric blood coagulometry in 49 peripheral arterial disease patients. In addition, we recorded the patients’ demographic information, including the presence of comorbidities, hemodynamic status, and laboratory findings. To investigate coagulability, we calculated the T_max value, which indicates the time from recalcification to maximum normalized permittivity.

Results

The T_max values of diabetes mellitus patients were significantly lower than those of non-diabetic patients (1 MHz, P = 0.010; 10 MHz, 0.011). Furthermore, the T_max value was statistically correlated with the activated partial thromboplastin time (1 MHz, ρ = 0.286, P = 0.048; 10 MHz, ρ = 0.301, P = 0.037).

Conclusions

Dielectric blood coagulometry detected the hypercoagulable status in diabetes mellitus patients, and reflected their level of coagulability, which was also evaluated by the activated partial thromboplastin time.

Effect of circulating tissue factor on hypercoagulability in type 2 diabetes mellitus studied by rheometry and dielectric blood coagulometry

BACKGROUND

Hypercoagulability in type 2 diabetes mellitus (T2DM) patients increases their risk of cardiovascular diseases.

OBJECTIVE

The aim of this work was to investigate the hypercoagulation mechanism in T2DM patients in terms of circulating tissue factor (TF).

METHODS

Whole blood coagulation tests by damped oscillation rheometry and dielectric blood coagulometry (DBCM) were performed.

RESULTS

The average coagulation time was significantly shorter for T2DM patients than for healthy controls. In vitro addition of either anti-TF or anti-activated factor VII (FVIIa) antibody to hypercoagulable blood samples prolonged coagulation times for one group of patients, while coagulation times remained short for another group. The levels of circulating TF were estimated in the former group by measuring the coagulation times for blood samples from healthy subjects with addition of various concentrations of TF and comparing them with the coagulation times for the group. The results indicated that the levels of circulating TF were on the order of subpicomolar at most.

CONCLUSIONS

Circulating TF is at least partially responsible for a hypercoagulable group of T2DM patients, while an abnormality in the intrinsic coagulation pathway probably occurs in the other group.

Dielectric permittivity change detects the process of blood coagulation: Comparative study of dielectric coagulometry with rotational thromboelastometry

BACKGROUND

Intravascular thrombus formation causes various cardiovascular diseases. To monitor coagulation is important for screening native status, prevention from bleeding and maintaining it within its therapeutic range. The prothrombin time and the activated partial thromboplastin time are widely used for assessment and recognized as the conventional methods. Prothrombin time methods employ enhancement of coagulation with thromboplastin. Since the laboratory data depend on the production lot and/or the manufacturer, the accurate methods are required for evaluation. Rotational thromboelastometry (ROTEM) is a method based on detection of the change in resistance to rotational movement during blood clotting, while dielectric blood coagulometry (DBCM) is a novel method for assessment of clotting by measuring the change of electrical permittivity. These methods are thus based on the technology for observation of different physical phenomena. The aim of this study was to compare parameters such as the clotting time obtained by ROTEM and DBCM to evaluate their clinical usefulness.

METHODS AND RESULTS

ROTEM and DBCM parameters were measured in 128 patients. The ROTEM clotting time showed a significant positive correlation with the DBCM coagulation time (R=0.707, p<0.001). Comparison of the DBCM coagulation time between patients with and without anticoagulant therapy (including novel oral anticoagulants) revealed a significant difference (43.8±11.9min in the anticoagulant group vs 29.4±8.3min in the control group, p<0.001). Evaluation of coagulation was equivalent with DBCM and ROTEM.

CONCLUSIONS

The present study suggested that DBCM, a novel method for measuring blood clotting, could provide the detail assessment for the status of anticoagulant therapy.

Novel Dielectric Coagulometer Identifies Hypercoagulability in Patients with a High CHADS2 Score without Atrial Fibrillation

Background

Recent reports showed that the CHADS₂ score predicted the risk of strokes in patients without atrial fibrillation (AF). Although the hypercoagulability may contribute to the thrombogenesis, it has not been fully investigated due to a lack of a sensitive evaluation modality. Recently a novel dielectric blood coagulometry (DBCM) was invented for evaluating the coagulability by measuring the temporal change in whole blood dielectric permittivity.

Objective

We evaluated the utility of the DBCM for identifying the coagulability.

Patients/Methods

For fundamental experiments, 133 citrated blood samples were drawn from subjects with or without heparin administration. A DBCM analysis was performed to find the adequate coagulation index, and to delineate its measurement range by adding recombinant human tissue factor (TF) or heparin. Then the coagulability was assessed by DBCM and conventional coagulation assays in 84 subjects without AF, who were divided into 3 groups by their CHADS₂ score. Another 17 patients who received warfarin were also assessed by DBCM to evaluate the effect of anticoagulants.

Results and Conclusions

We calculated the derivative of the dielectric permittivity change after recalcification, and extracted the end of acceleration time (EAT) as a novel index. The EAT showed a dose-dependent shortening with the addition of serial dilutions of TF (×10−² to ×10−⁴), and a dose-dependent prolongation with the addition of heparin (0.05 to 0.15 U/ml). The EAT was significantly shorter in the higher CHADS₂ score group (19.8 ± 4.8, 18.6 ± 3.1, and 16.3 ± 2.7 min in the CHADS₂ = 0, 1, and ≥2 groups, respectively, p = 0.0065 by ANOVA). Patients receiving warfarin had a significantly more prolonged EAT than those without warfarin (18.6±4.2 vs. 25.8±7.3 min, p <0.001). DBCM detected the whole blood coagulability with a high sensitivity. Subjects with higher CHADS₂ scores exhibited hypercoagulability without AF.