Thrombin generation in patients after acute deep-vein thrombosis

Thrombin generation measurement may be of value for assessing the risk of venous thromboembolism, but its long term profile has not been assessed in patients. We evaluated thrombin generation by Calibrated Automated Thrombogram (CAT) in plasma during follow up of 104 consecutive patients after an acute episode of deep venous thrombosis. Blood was drawn three times over the course of 24 months. Thrombin generation was measured in absence and presence of thrombomodulin and compared to a reference range derived from thrombin generation curves in 137 healthy volunteers. Thrombin generation of patients showed significantly higher endogenous thrombin potential (ETP) and peak height compared to the reference population. Differences were more pronounced in assays triggered with 1 pM TF. Inhibition by thrombomodulin was attenuated in patients off anticoagulants as compared to the reference population (21% vs. 42.2%, p < 0.0001); inhibition in patients on anticoagulant treatment was less pronounced (9.7%, p < 0.0001). Protein C activity, protein S antigen as well as free protein S showed highly negative correlation with ETP in all patients. A significant negative relation was found between FVIII levels and thrombomodulin induced reduction of ETP and peak height. In conclusion, thrombin generation by CAT reflects changes in coagulation status in patients following a thromboembolic event and is most sensitive at CAT analysis triggered with 1 pM TF. A role for factor VIII as an important attributable cause of hypercoagulability is reflected by the reduced inhibitory effect of thrombomodulin at high factor VIII levels.     

Apixaban decreases brain thrombin activity in a male mouse model of acute ischemic stroke

Factor Xa (FXa) plays a critical role in the coagulation cascade by generation of thrombin. During focal ischemia thrombin levels increase in the brain tissue and cause neural damage. This study examined the hypothesis that administration of the FXa inhibitor, apixaban, following focal ischemic stroke may have therapeutic potential by decreasing brain thrombin activity and infarct volume. Male mice were divided into a treated groups that received different doses of apixaban (2, 20, 100 mg/kg administered I.P.) or saline (controls) immediately after blocking the middle cerebral artery (MCA). Thrombin activity was measured by a fluorescence assay on fresh coronal slices taken from the mice brains 24 hr following the MCA occlusion. Infarct volume was assessed using triphenyltetrazolium chloride staining. A high dose of apixaban (100 mg/kg) significantly decreased thrombin activity levels in the ipsilateral hemisphere compared to the control group (Slice#5, p = .016; Slice#6, p = .016; Slice#7, p = .016; Slice#8, p = .036; by the nonparametric Mann–Whitney test). In addition, treatment with apixaban doses of both 100 mg/kg (32 ± 8% vs. 76 ± 7% in the treatment vs. control groups respectively; p = .005 by the nonparametric Mann–Whitney test) and 20 mg/kg (43 ± 7% vs. 76 ± 7% in the treatment vs. control groups respectively; p = .019 by the nonparametric Mann–Whitney test) decreased infarct volumes in areas surrounding the ischemic core (Slices #3 and #8). No brain hemorrhages were observed either in the treated or control groups. In summary, I.P. administration of high dose of apixaban immediately after MCA occlusion decreases brain thrombin activity and reduces infarct size.     

Low level of factor V is associated with development of deep-vein thrombosis in Japanese patients

Background

Factor V, having two functions (procoagulant and anticoagulant), is a key factor in blood coagulation, and low plasma levels of factor V may be a risk factor for thrombosis.

Objective

The levels of plasma factor V antigen (FV:Ag), and the phospholipid binding capability of Factor V (FV:PL-bound) were evaluated in patients with deep-vein thrombosis (DVT).

Methods

Levels of FV:Ag, and FV:PL-bound were expressed as a percentage of the normal level found in pooled plasma from control subjects. One hundred and twenty-three Japanese patients with deep-vein thrombosis (DVT) were included, with 100 age and sex-matched healthy control subjects.

Results

The FV:Ag, and FV:PL-bound values were significantly lower in DVT patients than in healthy subjects (p < 0.05 and p < 0.005, respectively). Among the 123 patients, 30 for FV:Ag (24.4%), and 32 for FV:PL (26%) had less than the arbitrary cutoff point (set at the 5th percentile of the value for FV:Ag and FV:PL-bound from healthy subjects), and the odds ratios (ORs) were 6.1 (95% confidence interval [CI], 2.3-16.5) and 6.7 (95%CI, 2.5-17.9), respectively. When patients with a deficiency of natural anticoagulants (antithrombin, protein C, and protein S) were excluded from the analysis, the ORs increased for all patients (6.6 for FV:Ag (95%CI, 2.4-18.3) and 7.4 for FV:PL-bound (95%CI, 2.7-20.3). Moreover, twenty-one (17%) of the 123 DVT patients, and 1 (1%) of 100 control subjects had values below the cutoff points for both FV:Ag and FV:PL-bound, and the OR was 21.6 (95%CI, 2.85-163.1).

Conclusions

These results suggest that low levels of factor V are associated with development of DVT, and may be a predictor for DVT.     

Failure of computerized impedance plethysmography in the diagnostic management of patients with clinically suspected deep-vein thrombosis

Before a new diagnostic modality can be introduced in clinical medicine, the validity of both a normal and abnormal test result have to be assessed prospectively in an appropriate patient group. We have evaluated the clinical validity of a new computerized impedance plethysmography (CIP) in the diagnostic management of 381 consecutive patients with clinically suspected venous thrombosis. In patients with serially normal CIP results, the diagnosis of venous thrombosis was refuted and, consequently, they were not treated with anticoagulant therapy and all were followed up for a period of 6 months to estimate the occurrence of symptomatic venous thromboembolism. The study was prematurely terminated by the safety monitoring committee because of an unacceptably high incidence of confirmed venous thromboembolism (10 patients, 3.2%; 95% confidence interval: 1.6% to 6%), including 4 episodes of fatal pulmonary embolism. In a subsequent explanatory study using ultrasonography in 29 other symptomatic patients who had at least 2 repeated normal CIP test results, the failure of CIP to detect proximal vein thrombosis was confirmed in 4 patients (14%). The reasons for this failure are probably related to the use of a modified device to measure impedance in the CIP apparatus, resulting in a lower ability to separate patients without venous thrombosis from those with the disease. We concluded that CIP is insensitive for the detection of proximal vein thrombosis and, therefore, not clinically useful in the diagnostic management of patients with suspected venous thrombosis.     

Hereditary and acquired thrombophilia in patients with upper extremity deep-vein thrombosis. Results from the MAISTHRO registry

The prevalence of coagulation disorders in patients with upper extremity deep-vein thrombosis (UE-DVT) is unknown due to only a few observational studies of limited size reporting varying results. Therefore, we aimed to evaluate the prevalence of thrombophilia in patients with UE-DVT compared to patients with lower extremity deep vein thrombosis (LE-DVT). One hundred fifty consecutive patients (15 to 91 years of age) with UE-DVT were recruited from the MAISTHRO (MAin-ISar-THROmbosis) registry. Three hundred LE-DVT patients matched for gender and age served as controls. Thrombophilia screening included tests for the factor V Leiden mutation, the prothrombin G20210A mutation, antiphospholipid antibodies and factor VIII (FVIII), protein C, protein S and antithrombin activities. At least one thrombophilia was present in 34.2% of UE-DVT and 39.2% in UE-DVT that was unrelated to venous catheters relative to 55.3% in LE-DVT patients (p < 0.001). In particular, a persistently elevated FVIII is less likely to be found in UE-DVT patients than in those with LE-DVT and is the only thrombophilia that is differentially expressed after controlling for established VTE risk factors [OR 0.46, (95% CI 0.25-0.83)]. Although less prevalent than in LE-DVT patients, thrombophilia is a common finding in patients with UE-DVT, especially in those with thrombosis that is unrelated to venous catheters.     

Subcutaneous administration of heparin a randomised comparison with intravenous administration of heparin to patients with deep-vein thrombosis

One-hundred and forty-one patients with clinical signs of acute deep venous thrombosis (DVT) in the legs were randomly allocated to recieve heparin either as two daily subcutaneous injections (s.c.) or as continuous intravenous infusion (i.v.). The thrombi extended into the popliteal or femoral veins in 83% of the patients. Verification of diagnosis and evaluation of therapy was performed by phlebography, plethysmography and thermography.

The results showed that heparin administered s.c. twice daily was as efficient as continuous i.v. infusion in preventing extension of the thrombus. In two patients the s.c. administration was stopped due to local haematomas at the injection sites. Retroperitoneal or intramuscular bleedings occurred in four patients, two in each group. Two major, non-fatal pulmonary emboli occurred, one in each group.     

Different characteristics and prognostic impact of deep-vein thrombosis / pulmonary embolism and intraabdominal venous thrombosis in colorectal cancer patients

This study was performed to determine the incidence, risk factors, and prognostic implications of venous thromboembolism (VTE) in Asian patients with colorectal cancer (CRC). Differences in clinical characteristics and prognostic impact between extremity venous thrombosis (or deep-vein thrombosis; DVT)/pulmonary embolism (PE) and intra-abdominal venous thrombosis (IVT) were also evaluated. For this study, consecutive CRC patients (N = 2,006) were enrolled and analyses were conducted retrospectively. VTEs were classified into two categories (DVT/PE and IVT). Significant predictors of developing VTEs were advanced stage and an increased number of co-morbidities. The two-year cumulative incidence of DVT/PE was 0.3%, 0.9% and 1.4% in stages 0~1, 2 and 3, respectively; this incidence range of DVT/PE in Asian patients with loco-regional CRC was lower than in Western patients. However, the two-year incidence (6.4%) of DVT/PE in Asian patients with distant metastases was not lower than in Western patients. Although 65.2% of patients with DVT/PE were symptomatic, only 15.7% of patients with IVT were symptomatic. During chemotherapy, DVT/PE developed more frequently than IVT. Only DVT/PE had a negative effect on survival; IVT had no prognostic significance. In conclusion, despite the low incidence of DVT/PE in Asian patients with loco-regional CRC, the protective effect of Asian ethnicity on VTE development disappears as tumour stage increases in patients with distant metastases. Considering different clinical characteristics and prognostic influences between DVT/PE and IVT, the treatment approach should be also different.     

Application of a diagnostic clinical model for the management of hospitalized patients with suspected deep-vein thrombosis

The purpose of this study was to evaluate whether the determination of pretest probability using a simple clinical model and the SimpliRED D-dimer could be used to improve the management of hospitalized patients with suspected deep-vein thrombosis. Consecutive hospitalized patients with suspected deep-vein thrombosis, had their pretest probability determined using a clinical model and had a SimpliRED D-dimer assay. Patients at low pretest probability underwent a single ultrasound test. A negative ultrasound excluded the diagnosis of deep-vein thrombosis whereas a positive ultrasound was confirmed by venography. Patients at moderate pretest probability with a positive ultrasound were treated for deep-vein thrombosis whereas patients with an initial negative ultrasound underwent a single follow-up ultrasound one week later. Patients at high pretest probability with a positive ultrasound were treated whereas those with negative ultrasound underwent venography. All patients were followed for three months for the development of venous thromboembolic complications. Overall, 28% (42/150), and 10% (5/50), 21% (14/71) and 76% (22/29) of the low, moderate and high pretest probability patients. respectively, had deep vein thrombosis. Two of 111 (1.8%; 95% CI = 0.02% to 6.4%) patients considered to have deep vein thrombosis excluded had events during three-month follow-up. Overall 13 of 150 (8.7%) required venography and serial testing was limited to 58 of 150 (38.7%) patients. The negative predictive value of the SimpliRED D-dimer in patients with low pretest probability was 96.2%, which is not statistically different from the negative predictive value of a negative ultrasound result in low pretest probability patients (97.8%). Management of hospitalized patients with suspected deep-vein thrombosis based on clinical probability and ultrasound of the proximal deep veins is safe and feasible.     

Inconsistencies in the planning of the duration of anticoagulation among outpatients with acute deep-vein thrombosis. Results from the OTIS-DVT Registry

Three-month anticoagulation is recommended to treat provoked or first distal deep-vein thrombosis (DVT), and indefinite-duration anticoagulation should be considered for patients with unprovoked proximal, unprovoked recurrent, or cancer-associated DVT. In the prospective Outpatient Treatment of Deep Vein Thrombosis in Switzerland (OTIS-DVT) Registry of 502 patients with acute objectively confirmed lower extremity DVT (59% provoked or first distal DVT; 41% unprovoked proximal, unprovoked recurrent, or cancer-associated DVT) from 53 private practices and 11 hospitals, we investigated the planned duration of anticoagulation at the time of treatment initiation. The decision to administer limited-duration anticoagulation therapy was made in 343 (68%) patients with a median duration of 107 (interquartile range 91-182) days for provoked or first distal DVT, and 182 (interquartile range 111-184) days for unprovoked proximal, unprovoked recurrent, or cancer-associated DVT. Among patients with provoked or first distal DVT, anticoagulation was recommended for < 3 months in 11%, ≥ 3 months in 63%, and for an indefinite period in 26%. Among patients with unprovoked proximal, unprovoked recurrent, or cancer-associated DVT, anticoagulation was recommended for < 6 months in 22%, 6-12 months in 38%, and for an indefinite period in 40%. Overall, there was more frequent planning of indefinite-duration therapy from hospital physicians as compared with private practice physicians (39% vs. 28%; p=0.019). Considerable inconsistency in planning the duration of anticoagulation therapy mandates an improvement in risk stratification of outpatients with acute DVT.     

CBS 844ins68, MTHFR TT677 and EPCR 4031ins23 genotypes in patients with deep-vein thrombosis

The role of methylenetetrahydrofolate reductase (MTHFR) TT677 genotype, cystathionine beta-synthase (CBS) 844ins68 mutation and endothelial cell protein C receptor (EPCR) 4031ins23 in the development of deep-vein thrombosis (DVT) was investigated in 300 consecutive DVT patients and 410 healthy blood donors. MTHFR TT677 was found in 40 (13.3%) patients and in 59 (14.4%) controls (OR 0.92; 95% C.I. 0.54-1.41); CBS 844ins68 in 20 (6.7%) patients and in 56 (13.7%) control subjects (OR 0.45; 95% C.I. 0.27-0.77); and the combination of MTHFR TT677 with CBS 844ins68 in 4 (1.3%) patients and in 7 (1.7%) controls (OR 0.78; 95% C.I. 0.23-2.68). Logistic regression analysis did not show a further increase of risk for MTHFR TT677 or CBS 844ins68 in combination with the factor V Leiden or the prothrombin gene G20210A mutations. The EPCR 4031ins23 was observed in 2 patients (0.66%) and none of the controls. In conclusion, MTHFR TT677 does not appear to be an important risk factor for DVT, EPCR 403ins23 seems to be very rare, its role in the development of DVT unclear. A putative protective effect of CBS 844ins68 should be further investigated.     

Enoxaparin vs heparin for prevention of deep-vein thrombosis in acute ischaemic stroke: a randomized,double-blind study

OBJECTIVES: To compare the efficacy, safety, and overall risk-benefit profile of enoxaparin and unfractionated heparin (UFH) prophylaxis of venous thromboembolic complications in patients with acute ischaemic stroke. METHODS: Patients with ischaemic stroke resulting in lower-limb paralysis lasting for at least 24 h and necessitating bedrest, were randomized within 48 h of the onset of stroke, and treated with enoxaparin (40 mg subcutaneously once daily) or UFH (5000 IU subcutaneously thrice daily) for 10 +/- 2 days. Main outcome measures were deep-vein thrombosis, pulmonary embolism (PE), death from any cause, intracranial haemorrhage including haemorrhagic infarction, or any other major bleeding. RESULTS: Outcome events occurred within 3 months of stroke in 40/106 patients treated with enoxaparin (37.7%) and 52/106 patients treated with UFH (49.1%, P=0.127). Fewer patients treated with enoxaparin (14, 13.2%) than with UFH (20, 18.9%) had evidence of haemorrhagic transformation of ischaemic stroke. CONCLUSIONS: Enoxaparin administered subcutaneously once daily was as safe and effective as subcutaneous UFH given thrice daily in the prevention of thromboembolic events in patients with lower limb paralysis caused by acute ischaemic stroke.     

Factor VII-activating protease in patients with acute deep venous thrombosis

Factor VII-activating protease (FSAP) is involved in haemostasis and inflammation. FSAP cleaves single chain urokinase-type plasminogen activator (scu-PA). The 1601GA genotype of the 1601G/A polymorphism in the FSAP gene leads to the expression of a FSAP variant with reduced ability to activate scu-PA, without affecting the ability to activate coagulation Factor VII (FVII). Previous studies have investigated the association of the 1601GA genotype with incidence and progression of carotid stenosis and deep venous thrombosis (DVT). The present study is the first to evaluate the potential association between the FSAP phenotype and DVT.We studied the association between the 1601G/A polymorphism, FSAP activity, FSAP antigen, Factor VIIa (FVIIa), prothrombin fragment 1 + 2 (F1 + 2), and C-reactive protein (CRP) in plasmas of 170 patients suspected for DVT. FSAP genotypes were equally distributed in patients with (n = 64) and without DVT (n = 106), (P = 0.94). The 1601GA genotype was associated with significant reduction of FSAP activity (P < 0.001) and FSAP antigen levels (P = 0.04). Patients with DVT showed significantly higher FSAP activity (P = 0.008), FSAP antigen (P = 0.003), and F1 + 2 levels (P < 0.001) than patients without DVT. The association between the FSAP measures and DVT disappeared when adjusted for CRP levels. F1 + 2 correlated positively to FSAP antigen (P = 0.01), while FVIIa-levels were comparable in patients with and without DVT.We conclude that even though FSAP measures are significantly increased in patients with acute DVT, alterations in the scu-PA activating properties of FSAP are presumably not markedly involved in the development of acute DVT, and that the association between FSAP and DVT disappears after adjustment for CRP.     

Patients with severe factor XI deficiency have a reduced incidence of deep-vein thrombosis

Factor XI (FXI) plays a dual role in haemostasis and thrombosis. It contributes to thrombin generation and promotes inhibition of fibrinolysis. Severe FXI deficiency was shown to confer protection against arterial and venous thrombosis in animal models without compromising haemostasis. We have previously shown that patients with severe FXI deficiency have a low incidence of ischaemic stroke, but display the usual incidence of myocardial infarction. In the present study, we compared the incidence of deep-vein thrombosis (DVT) in 219 unrelated patients with severe FXI deficiency aged 20-94 to the incidence in a large population-based study. No cases of DVT were observed in the FXI-deficient cohort, a result that is significantly lower than the expected number (4.68) computed from the population-based study. The low incidence remains statistically significant when compared to three other population-based studies. These data suggest that severe FXI deficiency provides protection against DVT.     

Randomized controlled study of heparin and low molecular weight heparin for prevention of deep-vein thrombosis in medical patients

166 patients aged 40-80 years were included in a controlled, randomized, double-blind study to determine the efficacy and safety of a single daily injection of a low molecular weight (LMW) heparin for prevention of deep-vein thrombosis compared to low dose conventional heparin. Patients received 1 x 1.500 aPTT units of a LMW heparin fraction (plus 2 x placebo injection) or 3 x 5.000 IU of an unfractionated heparin. During 10 days of treatment, patients underwent repeated clinical investigation, serial impedance plethysmography, and Doppler sonography for detection of thrombosis of the lower limbs. Combined application of these methods revealed evidence of thrombosis in 4.5% of patients on unfractionated heparin and 3.6% of patients on LMW heparin. Subcutaneous hematomas were significantly smaller in diameter upon treatment with LMW heparin (p less than 0.001). Antithrombin III levels were significantly higher at the end of the observation period in the LMW heparin group (p less than 0.005). Thrombocyte count, transaminases, creatinine, and haemoglobin did not change in either group. The results indicate that LMW heparin administered by a single s.c. dose daily may be as effective as low dose heparin in prevention of deep venous thrombosis in medical inpatients.     

Optimisation of the diagnostic strategy for suspected deep-vein thrombosis in primary care

Recently, a diagnostic score was developed to safely exclude deep-vein thrombosis (DVT) in primary care. A large prospective study, in which general practitioners used this diagnostic score to decide which patients needed referral, revealed that the number of referrals for ultrasound measurements was reduced by almost 50%, at the cost of an acceptably low risk (1.4%, 95% confidence interval [CI] 0.6% to 2.9%) of venous thromboembolic events in non-referred patients. However, simple adjustments to the diagnostic score (so-called updating) might further improve the accuracy; i.e. reduce the proportion of missed diagnoses (safety) or increase the proportion of patients who do not need to be referred (efficiency). We applied two updating methods to determine whether adjusting the weights of the predictors or adding new predictors could further improve the accuracy of the diagnostic score. The weights of the predictors did not need to be adjusted, but inclusion of 'history of DVT' and 'prolonged travelling' significantly added predictive value (p-values 0.014 and 0.023, respectively). However, adding these predictors to the diagnostic score did not improve the safety and efficiency: at equal safety (1.4% missed diagnoses among the non-referred patients), the efficiency was lower (43.5%, 95% CI 40.4% to 46.6% compared to 49.4%, 95% CI 46.3% to 52.5%). The diagnostic score for excluding DVT in primary care has good accuracy in its original form and could not be improved by including additional predictors. This suggests that the original diagnostic score can be used to safely exclude clinically suspected DVT in primary care.     

Factor VII hyperactivity in acute myocardial thrombosis. A relation to the coagulation activation

It has been shown that coagulation factor VII (FVII) has an increased coagulant activity (FVIIc) in cardiovascular high risk patients and that it is a important risk factor for the development of ischaemic heart disease (IHD) and cardiovascular death. In this study, we measured FVII coagulant (FVIIc) and immunological (FVIIag) activities during the acute phase of unstable angina (UA) and acute uncomplicated and complicated myocardial infarction (AMI). We have also studied its changes in relation to thrombin formation and coagulation activation, as assessed by determination of thrombin-antithrombin circulating complexes (T-AT) at the same time. Our results show a marked increase in FVIIc in all patients, with highest significant levels in complicated AMI. In fact, this increase was also different between groups, complicated AMI showing a significant degree of increase in FVIIc in relation to UA and uncomplicated AMI. FVIIag did not vary between groups and controls, implicating a progressive activation of FVII. As expected, we found comparable levels of T-AT in UA and in AMI patients, suggesting that a common thrombotic process is involved in both situations. FVIIc was strongly correlated to T-AT in all patients (r = 0. 750; p less than 0.001) and also within groups. This study underlines the important positive contribution of FVIIc to IHD and to the prognosis of its thrombotic acute events, and shows that the increase in FVII activity is associated with an increase of a thrombotic marker (thrombin-antithrombin). Further studies are needed to evaluate if FVII activation is the cause or the consequence of the thrombotic processes.