Effects of dabigatran, rivaroxaban, and apixaban on fibrin network permeability, thrombin generation, and fibrinolysis.

INTRODUCTION: There are important pharmacological differences between direct oral anticoagulants (DOAC) and a deeper knowledge of how they influence different aspects of hemostasis in patients on treatment is desirable. MATERIALS AND METHODS: Blood samples from patients on dabigatran (n = 23), rivaroxaban (n = 26), or apixaban (n = 20) were analyzed with a fibrin network permeability assay, a turbidimetric clotting and lysis assay, the calibrated automated thrombogram (CAT), plasma levels of thrombin-antithrombin complex (TAT) and D-dimer, as well as DOAC concentrations, PT-INR and aPTT. As a comparison, we also analyzed samples from 27 patients on treatment with warfarin. RESULTS: Patients on dabigatran had a more permeable fibrin network, longer lag time (CAT and turbidimetric assay), and lower levels of D-dimer in plasma, compared with patients on rivaroxaban- and apixaban treatment, and a more permeable fibrin network than patients on warfarin. Clot lysis time was slightly longer in patients on dabigatran than in patients on rivaroxaban. Warfarin patients formed a more permeable fibrin network than patients on apixaban, had longer lag time than patients on rivaroxaban (CAT assay), and lower peak thrombin and ETP compared to patients on treatment with both FXa-inhibitors. CONCLUSIONS: Results from this study indicate dabigatran treatment is a more potent anticoagulant than apixaban and rivaroxaban. However, as these results are not supported by clinical data, they are probably more related to the assays used and highlight the difficulty of measuring and comparing the effect of anticoagulants.

Rotational thromboelastometry results are associated with care level in COVID-19.

High prevalence of thrombotic events in severely ill COVID-19 patients have been reported. Pulmonary embolism as well as microembolization of vital organs may in these individuals be direct causes of death. The identification of patients at high risk of developing thrombosis may lead to targeted, more effective prophylactic treatment. The primary aim of this study was to test whether rotational thromboelastometry (ROTEM) at admission indicates hypercoagulopathy and predicts the disease severity, assessed as care level, in COVID-19 patients. The study was designed as a prospective, observational study where COVID-19 patients over 18 years admitted to hospital were eligible for inclusion. Patients were divided into two groups depending on care level: (1) regular wards or (2) wards with specialized ventilation support. Conventional coagulation tests, blood type and ROTEM were taken at admission. 60 patients were included; age 61 (median), 67% men, many with comorbidities (e.g. hypertension, diabetes). The ROTEM variables Maximum Clot Firmness (EXTEM-/FIBTEM-MCF) were higher in COVID-19 patients compared with in healthy controls (p < 0.001) and higher in severely ill patients compared with in patients at regular wards (p < 0.05). Our results suggest that hypercoagulopathy is present early in patients with mild to moderate disease, and more pronounced in severe COVID-19 pneumonia. Non-O blood types were not overrepresented in COVID-19 positive patients. ROTEM variables showed hypercoagulopathy at admission and this pattern was more pronounced in patients with increased disease severity. If this feature is to be used to predict the risk of thromboembolic complications further studies are warranted.

Management of rivaroxaban- or apixaban-associated major bleeding with prothrombin complex concentrates: a cohort study.

There is uncertainty regarding the effectiveness and occurrence of thromboembolic events in patients treated with prothrombin complex concentrates (PCCs) for the management of major bleeding events (MBEs) on rivaroxaban or apixaban. We investigated the effectiveness of PCCs given for the management of MBEs in patients on rivaroxaban or apixaban. Between 1 January 2014 and 1 October 2016, we prospectively included patients on rivaroxaban or apixaban treated with PCCs for the management of MBEs. The effectiveness of PCCs was assessed by using the International Society of Thrombosis and Hemostasis Scientific and Standardization Subcommittee criteria for the assessment of the effectiveness of major bleeding management. The safety outcomes were thromboembolic events and all-cause mortality within 30 days after treatment with PCCs. A total of 84 patients received PCCs for the reversal of rivaroxaban or apixaban due to a MBE. PCCs were given at a median (interquartile range) dose of 2000 IU (1500-2000 IU). Intracranial hemorrhage (ICH) was the most common site of bleeding requiring reversal (n = 59; 70.2%), followed by gastrointestinal bleeding in 13 (15.5%) patients. Management with PCCs was assessed as effective in 58 (69.1%) patients and ineffective in 26 (30.9%) patients. Most patients with ineffective hemostasis with PCCs had ICH (n = 16; 61.5%). Two patients developed an ischemic stroke, occurring 5 and 10 days after treatment with PCC. Twenty-seven (32%) patients died within 30 days after a MBE. The administration of PCCs for the management of MBEs associated with rivaroxaban or apixaban is effective in most cases and is associated with a low risk of thromboembolism. Our findings are limited by the absence of a control group in the study.

Relative effects of plasma, fibrinogen concentrate, and factor XIII on ROTEM coagulation profiles in an in vitro model of massive transfusion in trauma.

Massive traumatic haemorrhage is aggravated through the development of trauma-induced coagulopathy, which is managed by plasma transfusion and/or fibrinogen concentrate administration. It is yet unclear whether these treatments are equally potent in ensuring adequate haemostasis, and whether additional factor XIII (FXIII) administration provides further benefits. In this study, we compared ROTEM whole blood coagulation profiles after experimental massive transfusion with different transfusion regimens in an in vitro model of dilution- and transfusion-related coagulopathy. Healthy donor blood was mixed 1 + 1 with six different transfusion regimens. Each regimen contained RBC, platelet concentrate, and either fresh frozen plasma (FFP) or Ringer's acetate (RA). The regimens were further augmented through addition of a low- or medium-dose fibrinogen concentrate and FXIII. Transfusion with FFP alone was insufficient to maintain tissue-factor activated clot strength, coincidental with a deficiency in fibrin-based clot strength. Fibrinogen concentrate conserved, but did not improve coagulation kinetics and overall clot strength. Only combination therapy with FFP and low-dose fibrinogen concentrate improved both coagulation kinetics and fibrin-based clot strength. Administration of FXIII did not result in an improvement of clot strength. In conclusion, combination therapy with both FFP and low-dose fibrinogen concentrate improved clotting time and produced firm clots, representing a possible preferred first-line regimen to manage trauma-induced coagulopathy when RBC and platelets are also transfused. Further research is required to identify optimal first-line transfusion fluids for massive traumatic haemorrhage.

Strategies and outcomes of periprocedural bridging therapy with low-molecular-weight heparin in patients with mechanical heart valves.

Patients with mechanical heart valves (MHV) undergoing invasive procedures often receive periprocedural bridging with low-molecular-weight heparin (LMWH). The bridging strategies used in real-life and the predictors for bleeding and thrombosis are not well studied. We retrospectively assessed patients with MHV that underwent invasive procedures requiring vitamin K antagonist interruption and LMWH bridging. Thromboembolic and bleeding events occurring up to 30 days after the procedures were recorded. Predictors of major bleeding events (MBEs) were analyzed with logistic regression. We evaluated 547 patients with MHV who underwent 275 procedures during a 6.5-year period. Bridging with LMWH was used in 185 procedures in a total of 117 patients. Combined pre- and post-operative bridging was the most frequently employed (63 %). Doses of LMWH were prophylactic in 96 (52 %) of the procedures and therapeutic in 89 (48 %). The procedure-related bleeding risk was evaluated as high in 70 (38 %) and low in 115 (62 %) of the procedures. There was a trend to more frequent use of prophylactic doses (61 %) in high-risk surgery, and more therapeutic doses (53 %) in low-risk ones. There were 36 bleeding episodes, 21 (11 % of procedures) of which were classified as MBEs, but there were no thromboembolic events. Most MBEs (n = 14; 67 %) occurred in surgeries with high bleeding risk. In the multivariate analysis, the bleeding risk of the surgery itself was the only independent predictor for MBEs. For patients with MHV receiving perioperative bridging with LMWH, the major predictor for MBE is the bleeding risk of the surgery.

TEG® functional fibrinogen analysis may overestimate fibrinogen levels.

Fibrinogen is of crucial importance in patients with ongoing bleeding. In this study, we compared fibrinogen concentration measured by thrombelastography (TEG®) with fibrinogen plasma concentration determined by Clauss. Sixty-three surgical patients and 38 healthy controls were included. For the whole group (patients and controls, n = 101), TEG® functional fibrinogen was on average 1.0 g/L higher than the plasma fibrinogen concentration (3.5 vs 2.5 g/L, 95% confidence interval for difference 0.8 to 1.2 g/L, P < 0.0001). Similar patterns were observed when patients and healthy controls were analysed separately. The fibrinogen level may be overestimated when assessed using TEG® compared with the fibrinogen plasma concentration measured by the conventional method.

Life-Threatening Thrombosis After Large Amounts of Nitrous Oxide Use.

This case report highlights the development of severe, life-threatening thrombotic complications after chronic recreational use of large quantities of nitrous oxide in a 21-year-old patient. In young patients presenting with thromboembolism and nitrous oxide abuse, swift identification of symptoms and management is critical.

Thromboelastography (TEG®) compared to conventional coagulation tests in surgical patients--a laboratory evaluation.

BACKGROUND: Several methods exist for evaluation of hypocoagulation in patients with perioperative bleeding, e.g. thromboelastography (TEG(®)) and conventional methods (platelet count, aPTT, INR and fibrinogen). Considering the vast experience of conventional methods it is important to investigate how well the methods correspond. METHODS: Sixty surgical patients were included prospectively and blood samples were taken perioperatively. TEG(®) and conventional parameters were analyzed simultaneously. An assessment of coagulopathy, based on a synthesis of the conventional methods, was done by two experienced coagulation specialists, blinded from the results of TEG(®) and from the results of each other. Hypocoagulation, defined by TEG(®) parameters; reaction time (R-time), angle, maximal amplitude (MA) and fibrinolysis, was evaluated according to a commonly used algorithm. RESULTS: To detect a platelet count below 150 × 10(9) L(-1), the sensitivity of TEG was 17% (95% CI, 7-36%) with angle and 25% (95% CI, 11-45%) with MA. The sensitivity to detect fibrinogen below 2 g/L was 11% (95% CI, 3-29%) with angle and 21% with MA (95% CI, 8-43%). To detect aPTT more than 40 s and INR more than 1.2 with R-time, the sensitivity was 19% (95% CI, 8-37%) and 0% (95% CI, 0-69%) respectively. The agreement of the evaluator's assessments of hypocoagulation was 100%, but the agreement with the overall TEG(®) analysis was poor with a sensitivity of 33% and a specificity of 95%. CONCLUSION: The agreement between conventional laboratory tests and TEG is poor, but it remains uncertain which type of coagulation tests that best reflects the actual bleeding risk.

Rapid Detection of Apixaban by a ROTEM-Based Approach and Reversibility with Andexanet Alfa or DOAC-Stop.

Background A rapid test to detect apixaban treatment would be useful in acute situations such as major bleeding, urgent surgery, or in acute thrombosis. Objective This article aims to study if the viscoelastic test rotational thromboelastometry (ROTEM) can rapidly detect apixaban in whole blood using modified triggers based on factor Xa (FXa) or Russell viper venom (RVV). Method ROTEM clotting time (CT) was measured in samples from 40 patients on apixaban treatment, and in vitro in samples spiked with apixaban (20-500 ng/mL). Commercially available trigger Ex-tem was compared with modified triggers based on FXa or RVV. Reversibility of apixaban in the samples was studied; CT was measured with and without addition of DOAC-Stop or andexanet alfa, respectively, and the difference in CT was calculated (CT diff ). Results Using FXa as trigger, we detected apixaban concentrations at 20 ng/mL and above with 100% sensitivity and 100% specificity in patient samples and in vitro. Corresponding data for Ex-tem were 92% sensitivity and 100% specificity in patients, and 94% sensitivity and 100% specificity in vitro, and for RVV 97% sensitivity and 94% specificity in patients, and 97% sensitivity and 100% specificity in vitro, respectively. CT diff data were similar. Patient sample data were obtained within 20 minutes from sampling. Conclusion Apixaban at low therapeutic concentrations was detected within 20 minutes, and with high sensitivity and specificity. A trigger based on FXa outperformed the commercial trigger Ex-tem and a trigger based on RVV. ROTEM with a FXa-based trigger is a promising method to detect apixaban bedside in acute settings.

Fibrinogen and albumin synthesis rates in major upper abdominal surgery.

Plasma fibrinogen and albumin concentrations initially decrease after abdominal surgery. On postoperative days 3-5 fibrinogen concentration returns to the preoperative level or even higher, while albumin stays low. It is not known if these altered plasma concentrations reflect changes in synthesis rate, utilization, or both. In particular a low albumin plasma concentration has often been attributed to a low synthesis rate, which is not always the case. The objective of this study was to determine fibrinogen and albumin quantitative synthesis rates in patients undergoing major upper abdominal surgery with and without intact liver size. Patients undergoing liver or pancreatic resection (n = 9+6) were studied preoperatively, on postoperative days 1 and 3-5. De novo synthesis of fibrinogen and albumin was determined; in addition, several biomarkers indicative of fibrinogen utilization were monitored. After hemihepatectomy, fibrinogen synthesis was 2-3-fold higher on postoperative day 1 than preoperatively. On postoperative days 3-5 the synthesis level was still higher than preoperatively. Following major liver resections albumin synthesis was not altered postoperatively compared to preoperative values. After pancreatic resection, on postoperative day 1 fibrinogen synthesis was 5-6-fold higher than preoperatively and albumin synthesis 1.5-fold higher. On postoperative days 3-5, synthesis levels returned to preoperative levels. Despite decreases in plasma concentrations, de novo synthesis of fibrinogen was markedly stimulated on postoperative day 1 after both hemihepatectomies and pancreatectomies, while de novo albumin synthesis remained grossly unchanged. The less pronounced changes seen following hepatectomies were possibly related to the loss of liver tissue.

Hypercoagulation Detected by Rotational Thromboelastometry Predicts Mortality in COVID-19: A Risk Model Based on a Prospective Observational Study.

Background Severe disease due to the novel coronavirus disease 2019 (COVID-19) has been shown to be associated with hypercoagulation. The aim of this study was to assess the Rotational Thromboelastometry (ROTEM) as a marker of coagulopathy in hospitalized COVID-19 patients. Methods This was a prospective, observational study where patients hospitalized due to a COVID-19 infection were eligible for inclusion. Conventional coagulation tests and ROTEM were taken after hospital admission, and patients were followed for 30 days. A prediction model, including variables ROTEM EXTEM-MCF (Maximum Clot Firmness) which in previous data has been suggested a suitable marker of hypercoagulation, age, and respiratory frequency, was developed using logistic regression to evaluate the probability of death. Results Out of the 141 patients included, 18 (13%) died within 30 days. In the final prediction model, the risk of death within 30 days for a patient hospitalized due to COVID-19 was increased with increased EXTEM-MCF, age, and respiratory frequency. Longitudinal ROTEM data in the severely ill subpopulation showed enhanced hypercoagulation. In an in vitro analysis, no heparin effect on EXTEM-coagulation time (CT) was observed, supporting a severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) effect on prolonged initiation of coagulation. Conclusion Here, we show that hypercoagulation measured with ROTEM predicts 30-day mortality in COVID-19. Longitudinal ROTEM data strengthen the hypothesis of hypercoagulation as a driver of severe disease in COVID-19. Thus, ROTEM may be a useful tool to assess disease severity in COVID-19 and could potentially guide anticoagulation therapy.

Platelet thrombus formation in patients with end-stage renal disease before and after hemodialysis as measured by the total thrombus-formation analysis system.

BACKGROUND: Patients with end-stage renal disease (ESRD) receiving hemodialysis (HD) often experience bleeding. However, mechanisms behind this bleeding tendency are incompletely understood but may involve platelet dysfunction. We, therefore, studied platelet-dependent thrombus formation in flowing whole blood inside a microchip coated with collagen, and its association with circulating von Willebrand factor (VWF). METHODS: Blood samples were obtained in 22 patients before and after HD. The area under the 10 min flow pressure curve in a microchip (AUC10) reflecting total platelet thrombogenicity was measured, using the Total Thrombus-formation Analysis System (T-TAS01). AUC10 < 260 indicates platelet dysfunction. VWF activity and antigen in plasma were also assayed. RESULTS: VWF levels were moderately elevated and increased further after HD (P < 0.01 or lower). In contrast, AUC10 before and after HD was < 260 in 17/22 patients and < 130 in 15/22 patients, with no statistically significant difference in pre- vs post-HD measurements, indicating reduced platelet thrombogenicity, but with some variability as 5/22 patients showed normal platelet responsiveness. AUC10 and VWF activity or antigen levels in plasma were not correlated, either before or after HD. CONCLUSIONS: Most ESRD patients display moderate-to-severe platelet dysfunction as assessed by shear-induced platelet-dependent thrombus formation with T-TAS01. HD does not influence platelet function despite HD-induced elevations in VWF. T-TAS01 should be further evaluated as a tool in the assessment of bleeding risk in patients on HD.

Neutrophil extracellular traps in patients with liver cirrhosis and hepatocellular carcinoma.

Neutrophil extracellular traps (NETs) are web-like structures consisting of DNA, histones and granule proteins, released from neutrophils in thrombus formation, inflammation, and cancer. We asked if plasma levels of the NET markers myeloperoxidase (MPO)-DNA and citrullinated histone H3 (H3Cit)-DNA, are elevated in liver cirrhosis and hepatocellular carcinoma (HCC) and if the levels correlate with clinical parameters. MPO-DNA, H3Cit-DNA, and thrombin-antithrombin (TAT) complex, as a marker of coagulation activity, were measured using ELISA in plasma from 82 patients with HCC, 95 patients with cirrhosis and 50 healthy controls. Correlations were made to clinical parameters and laboratory data and patients were followed for a median of 22.5 months regarding thrombosis development. H3Cit-DNA was significantly (p < 0.01) elevated in plasma from cirrhosis (66.4 ng/mL) and HCC (63.8 ng/mL) patients compared to healthy controls (31.8 ng/mL). TAT levels showed similar pattern (3.1, 3.7, and 0.0 µg/mL respectively, p < 0.01). MPO-DNA was significantly (p < 0.01) elevated in cirrhosis patients (0.53 O.D.) as compared to controls (0.33 O.D.). Levels of MPO-DNA and H3Cit-DNA correlated positively with Child-Pugh and MELD score. TAT was increased in all Child-Pugh and MELD groups. In multivariable logistic regression, Child B and C liver cirrhosis were independent predictors of elevated H3Cit-DNA in plasma. Levels of MPO-DNA and H3Cit-DNA were similar in patients with or without history of thrombosis, or thrombus formation during follow-up. In conclusion, plasma markers of NET formation are elevated in liver cirrhosis and correlate to the degree of liver dysfunction in patients with liver cirrhosis and/or HCC. The presence of HCC did not further increase the plasma levels of NET markers as compared to patients with cirrhosis only.

Platelet Count Rose While D-Dimer Levels Dropped as Deaths and Thrombosis Declined-An Observational Study on Anticoagulation Shift in COVID-19.

BACKGROUND: High levels of D-dimer and low platelet counts are associated with poor outcome in coronavirus disease 2019 (COVID-19). As anticoagulation appeared to improve survival, hospital-wide recommendations regarding higher doses of anticoagulation were implemented on April 9, 2020. OBJECTIVES: To investigate if trends in D-dimer levels and platelet counts were associated with death, thrombosis, and the shift in anticoagulation. METHODS: Retrospective cohort study of 429 patients with COVID-19 at Karolinska University Hospital. Information on D-dimer levels and platelet counts was obtained from laboratory databases and clinical data from medical records. RESULTS: Thirty-day mortality and thrombosis rates were 19% and 18%, respectively. Pulmonary embolism was common, 65/83 (78%). Increased D-dimer levels in the first week in hospital were significantly associated with death and thrombosis (odds ratio [OR]: 6.06; 95% confidence interval [CL]: 2.10-17.5 and 3.11; 95% CI: 1.20-8.10, respectively). If platelet count increased more than 35 × 109/L per day, the mortality and thrombotic risk decreased (OR: 0.16; 95% CI: 0.06-0.41, and OR: 0.36; 95% CI: 0.17-0.80). After implementation of updated hospital-wide recommendations, the daily mean significantly decreased regarding D-dimer levels while platelet counts rose; -1.93; 95% CI: -1.00-2.87 mg/L FEU (fibrinogen-equivalent unit) and 65; 95% CI: 54-76 ×109/L, and significant risk reductions for death and thrombosis were observed; OR: 0.48; 95% CI: 0.25-0.92 and 0.35; 95% CI: 0.17-0.72. CONCLUSION: In contrast to D-dimer levels, increase of platelet count over the first week in hospital was associated with improved survival and reduced thrombotic risk. The daily mean levels of D-dimer dropped while the platelet counts rose, coinciding with increased anticoagulation and a decline in thrombotic burden and mortality.

Thromboembolism, Hypercoagulopathy, and Antiphospholipid Antibodies in Critically Ill Coronavirus Disease 2019 Patients: A Before and After Study of Enhanced Anticoagulation.

To determine the prevalence of thrombotic events, functional coagulation tests, inflammatory biomarkers, and antiphospholipid antibodies before and after enhanced anticoagulation in critically ill coronavirus disease 2019 patients. DESIGN: Retrospective. SETTING: Tertiary intensive care unit. PATIENTS: Two cross-sectional cohorts of ICU-treated coronavirus disease 2019 patients were included before (cohort 1, n = 12) and after (cohort 2, n = 14) enhanced prophylactic anticoagulation strategy. INTERVENTIONS: Before and after study of enhanced anticoagulation. MEASUREMENTS AND MAIN RESULTS: Thromboelastometry point-of-care coagulation tests were performed by thromboelastography (Tem International GmbH, Munich, Germany), standard blood tests were extracted from patient charts, and presence of antiphospholipid antibodies in plasma was measured. All patients were males on mechanical ventilation. In cohort 1 (low-molecular-weight heparin dose: 129 ± 53 U/kg/24 hr), 50% had pulmonary embolism, and thromboelastography analysis revealed hypercoagulation in a majority of patients and greater than 80% had detectable antiphospholipid antibodies. In the second cohort (enhanced low-molecular-weight heparin dose: 200 ± 82 U/kg/24 hr; p = 0.04 vs cohort 1), we found a nonsignificantly lower prevalence of pulmonary embolism (21%; p = 0.22), lower fibrinogen (6.3 ± 2.5 vs 8.7 ± 2.0; p = 0.02), reduced fibrinogen-dependent thromboelastography (p < 0.001), and lower inflammatory markers. CONCLUSIONS: In these two cross-sectional cohorts of ICU-treated coronavirus disease 2019 patients, thromboembolic complications, hypercoagulation, and antiphospholipid antibodies were common. A more aggressive anticoagulation regime was associated with a reduction in inflammatory biomarkers including plasma fibrinogen and a reduction in fibrinogen-dependent hypercoagulation, as indicated by thromboelastography analyses.

A retrospective register study comparing fibrinogen treated trauma patients with an injury severity score matched control group.

BACKGROUND: Fibrinogen concentrate (FC) is frequently used to treat bleeding trauma patients, although the clinical effects are not well known. In this study we describe demographic and clinical outcome data in a cohort of trauma patients receiving FC, compared to a matched control group, who did not receive FC. METHODS: This retrospective, single-center, observational study included adult trauma patients admitted to a level 1-trauma center in Sweden between January 2013 and June 2015. The study population consisted of patients to whom FC was administrated within 24 h (n = 138, "Fib+"). Patients with Injury Severity Score (ISS) > 49 and/or deceased within 1 h from arrival were excluded (n = 30). Controls (n = 108) were matched for age, gender and ISS ("Fib-"). Primary outcome was mortality (24 h-/30 days-/1 year-), and secondary outcomes were blood transfusions, thromboembolic events and organ failure. RESULTS: The Fib+ group, despite having similar ISS as Fib-, had higher prevalence of penetrating trauma and lower Glasgow Coma Scale (GCS), indicating more severe injuries. Patients receiving FC had a higher mortality after 24 h/ 30 days/ 1 year compared to controls (Fib-). However, in a propensity score matched model, the differences in mortality between Fib+ and Fib- were no longer significant. Blood transfusions were more common in the Fib+ group, but no difference was observed in thromboembolic events or organ failure. In both groups, low as well as high P-fibrinogen levels at arrival were associated with increased mortality, with the lowest mortality observed at P-fibrinogen values of 2-3 g/l. CONCLUSIONS: Despite equal ISS, patients receiving FC had a higher mortality compared to the control group, presumably associated to the fact that these patients were bleeding and physiologically deranged on arrival. When applying a propensity score matching approach, the difference in mortality between the groups was no longer significant. No differences were observed between the groups regarding thromboembolic events or organ failure, despite higher transfusion volumes in patients receiving FC.

Correlation of thromboelastography and thrombin generation assays in warfarin-treated patients.

Venous thromboembolism (VTE) affects approximately 1 per 1000 persons annually. Although patients are increasingly treated with direct oral anticoagulants, many patients continue to be anticoagulated with vitamin K antagonists (VKA). The most important adverse events during VKA treatment, bleeding and the risk of recurrent VTE, are difficult to predict. Global haemostatic assays, such as thrombin generation assays and the viscoelastic whole blood tests thromboelastography (TEG) and thromboelastometry (ROTEM), allow a comprehensive assessment of haemostasis and could potentially predict such side effects. In the present study we compared results from thrombin generation (Calibrated Automated Thrombogram and Innovance ETP assays) and TEG and ROTEM in 84 warfarin-treated patients with primary or recurrent VTE and 87 healthy controls. VKA treatment lead to lagtime prolongation and a lower overall thrombin production, which correlated strongly with INR (Pearson r = 0.89 and r = -0.85, respectively). The reduced thrombin generation of VKA-treated patients was accurately reflected by tissue-factor activated ROTEM (EXTEM) clotting time prolongation (vs. CAT lagtime, r = 0.87). Clot strength or clot formation kinetics were only weakly affected by thrombin generation. Intrinsic pathway activated TEG or ROTEM (INTEM) were not sensitive to the reduced thrombin generation. In conclusion, patients anticoagulated with VKA after VTE showed a reduced plasma thrombin generation that was accurately reflected by tissue factor activated ROTEM. ROTEM provided additional information to thrombin generation, including clot formation kinetics and strength.

Laboratory evidence of hyperfibrinolysis in association with low plasminogen activator inhibitor type 1 activity.

Low activity of plasminogen activator inhibitor type 1 (PAI-1) has been associated with bleeding complications in surgery. We earlier reported a higher prevalence of low PAI-1 activity among patients with bleeding tendency as compared with normal control individuals. The present study evaluated whether low PAI-1 activity actually is associated with markers of increased fibrinolytic activity in plasma from patients with a history of bleeding. PAI-1 activity, plasmin-antiplasmin complex (PAP) and D-dimer were analyzed in plasma samples from 424 consecutive patients referred to the Coagulation Unit for investigation of bleeding symptoms. The median PAI-1 activity was 4.0 U/ml [interquartile range (IQR), 1-10 U/ml], the median PAP level was 1.59 mg/l (IQR, 1.40-1.91 mg/l) and the median D-dimer level was 71 microg/l (IQR, 46-111 microg/l). The median PAP concentration for patients with PAI-1 less than 1.0 U/ml was 1.73 mg/l (IQR, 1.53-2.30 mg/l), and that for PAI-1 of at least 1.0 U/ml was 1.54 mg/l (IQR, 1.36-1.83 mg/l) (P < 0.0001). There was also a significant difference between the PAP levels in patients with normal PAI-1 (1-15 U/ml) versus elevated PAI-1 (> 15 U/ml) (P = 0.024). The level of D-dimer did not correlate with PAI-1 activity. In conclusion, the activation of plasminogen measured as PAP was higher in patients with bleeding symptoms in combination with PAI-1 activity less than 1.0 U/ml than in those with PAI-1 activity of at least 1.0 U/ml. The coagulation activity under normal conditions, as measured by D-dimer, did not differ between the two patient subsets. The results support our previous definition of low PAI-1 as activity below 1.0 U/ml.