Etiology and VTE risk factor distribution in patients with inferior vena cava thrombosis

Introduction

Inferior vena cava (IVC) thrombosis is a rare event and data detailing the underlying etiology are scarce.

Materials and methods

Therefore, we reviewed all available cases of IVC thrombosis consecutively registered in the MAISTHRO (MAin-ISar-THROmbosis) database and described the prevalence of VTE risk factors and other conditions contributing to IVC thrombosis development.

Results

53 patients (35 F, 18 M) with IVC thrombosis aged 12 to 79 years were identified. 40 patients (75.5%) developed thrombosis under the age of 45. Local problems, such as IVC anomalies or external venous compression, contributed to the development of thrombosis in 12 cases (22.6%). Lupus anticoagulants (10.9 vs. 2.3%, p = 0.013) and malignoma (17.0 vs. 6.4%, p = 0.023) were more prevalent in IVC thrombosis patients compared to 265 age and sex matched controls with isolated lower extremity DVT. No difference was identified with regard to inherited thrombophilia or other known VTE risk factors. Symptomatic pulmonary embolism (PE) occurred in 32.1% of IVC thrombosis patients compared to 15.2% of controls (p = 0.005).

Conclusions

Local problems such as IVC anomalies and external venous compression, malignancy and the presence of lupus anticoagulants contribute to the risk of IVC thrombosis. The risk of symptomatic pulmonary embolism in the acute setting is high.     

Evaluation of the prevalence of severe hyperhomocysteinemia in adult patients with thrombosis who underwent screening for thrombophilia

Introduction

Treatment with B-vitamins and betaine reduces the high risk of thrombosis in patients with homocystinuria, a metabolic syndrome that is characterized by severe hyperhomocysteinemia (HHcy). In contrast, there is no clear demonstration that B-vitamins reduce the risk of thrombosis in patients with mild HHcy: for this reason, many question the clinical utility of measuring total Hcy (tHcy) in patients with thrombosis. However, thrombosis may be the first clinical manifestation of homocystinuria in patients reaching adulthood without signs and symptoms of the syndrome.

Aim

1) to measure the prevalence of severe, previously undiagnosed, HHcy among patients with thrombosis 2) to profile these patients on the basis of their characteristics.

Methods

Six Italian Thrombosis Centers completed a first questionnaire, reporting tHcy levels in patients with thrombosis who underwent thrombophilia screening, and a second questionnaire, reporting the characteristics of patients with severe HHcy (tHcy > 100 μmol/L).

Results

Of 19,678 cross-sectionally collected patients with thrombosis who underwent thrombophilia screening in the last 12.5 years (median value, range 6-17), 38 had severe HHcy (0.2%). Their median age at diagnosis was 47 years (range 19-83) and the median level of tHcy was 130 μmol/L (range 101-262). Venous thromboembolism (71%) was more frequent than arterial thromboembolism (26%); recurrent thrombosis occurred in 42% of cases.

Conclusions

Measurement of tHcy in adult patients with thrombosis may reveal the presence of severe HHcy. Since treatment of patients with severe HHcy decreases the risk of thrombosis, measurement of tHcy in patients with thrombosis may prove clinically useful.     

Clinical course and predictive factors for complication of inferior vena cava filters

Rationale

The use of inferior vena cava (IVC) filters is associated with various complications. We aimed to elucidate the clinical course and predictive factors for complications of IVC filters, especially IVC penetration

Methods

A retrospective observational study was performed in 45 adult patients with retrievable IVC filters and follow-up computed tomography (CT) between January 2003 and December 2012. Primary outcomes were the prevalence and predictive factors of IVC penetration. Secondary outcome was other complications of IVC filters.

Results

IVC penetration following filter placement occurred in 87.6% of patients, and 57.8% of those involved significant penetration. Embedding of filter tips, suggestive of lateral tilting, was observed in 51.1%. Both Vertebral body erosions and aortic penetrations were seen in 4.4%, but they were asymptomatic. Longer indwelling duration of the IVC filter was significantly associated with a higher grade of IVC penetration, and the risk of significant IVC penetration increased in patients with the filter indwelling time of more than 20 days and an IVC diameter of less than 24.2 mm.

Conclusions

In patients with a retrievable IVC filter, IVC penetration on CT was common, and significant IVC penetration was associated with a longer indwelling time of the IVC filter and a lesser IVC diameter.     

Predictors of attempted inferior vena cava filters retrieval in a tertiary care centre

Background

Retrieval rates of optional recovery inferior vena cava (IVC) filters in US hospitals range from 11 - 70%. We conducted a retrospective study in a Canadian tertiary care centre to determine retrieval rates and predictors of filter removal.

Methods

Consecutive patients who had a retrievable IVC filter inserted or removed between January 2007 and December 2010 were identified. Data collected included baseline demographics, indications for filter insertion and removal, documentation of an IVC filter management plan, reasons for non-retrieval, complications, and death.

Results

275 patients with a median age of 60 years were followed in hospital for a median of 17 patient-days (range 1–876). Indications for filter placement were acute or prior VTE with contraindication to anticoagulation (72.4%), high risk of PE (11.3%) and primary prophylaxis (13.8%). Retrieval was attempted in 165 patients (60%) and was successful in 146 patients (53.1%). The most common reason for failed retrieval was filter thrombus. Predictors of attempted retrieval included documentation of filter plan (odds ratio [OR] 16.7; p < 0.001), surgical indication for IVC filter insertion (OR 4.8; p = 0.002), age ≤ 70 years (OR 3.8; p = 0.001), Hematology service involvement (OR 3.0; p = 0.006), and presence of metastatic cancer (OR 0.2; p = 0.001). Thrombotic complications occurred in 48 patients, including 3 patients who died of fatal PE.

Conclusion

Our filter retrieval rate is suboptimal. Improvements in follow-up documentation or a dedicated clinical service may help increase retrieval rates.     

Increased thrombin generation in splanchnic vein thrombosis is related to the presence of liver cirrhosis and not to the thrombotic event

Introduction

In recent years there have been increasing evidence associating liver disease with hypercoagulability, rather than bleeding. The aim of the study was to evaluate the haemostatic potential in patients with liver disease.

Patients and methods

We measured thrombin generation in the presence and absence of thrombomodulin in patients with portal vein thrombosis (PVT, n = 47), Budd-Chiari syndrome (BCS, n = 15) and cirrhosis (n = 24) and compared the results to those obtained from healthy controls (n = 21). Fifteen patients with PVT and 10 patients with BCS were treated with warfarin and were compared to an equal number of patients with atrial fibrillation matched for prothrombin time-international normalized ratio. We assessed resistance to thrombomodulin by using ratios [marker measured in the presence/absence of thrombomodulin].

Results

There were no differences in thrombin generation between patients on warfarin treatment and their controls. Cirrhotic patients generated more thrombin in the presence of thrombomodulin and exhibited thrombomodulin resistance compared to controls [p = 0.006 for endogenous thrombin potential (ETP) and p < 0.001 for peak thrombin and both ratios ETP and peak] and patients with non-cirrhotic PVT (p = 0.001, p = 0.006, p < 0.001, p < 0.001 for ETP, peak, ratio ETP, ratio peak, respectively). The patients with cirrhotic PVT exhibited higher ETP (p = 0.044) and peak (p = 0.02) in the presence of thrombomodulin than controls, as well as thrombomodulin resistance (ETP and peak ratios: p = 0.001).

Conclusions

Hypercoagulability and thrombomodulin resistance in patients with cirrhosis were independent of the presence of splanchnic vein thrombosis. The hypercoagulability in patients with cirrhotic PVT could have implications for considering longer or more intensive treatment with anticoagulants in this group.     

Enhanced thrombin generation in women with a history of oral contraception-related venous thrombosis

Introduction

In women who suffer venous thrombosis (VT) during oral contraceptive (OC) use, a transient risk factor (OC) is removed during the acute event, while most co-existing forms of thrombophilia persist and presumably continue to maintain hypercoagulability. The aim of this study was to establish if hypercoagulability persists long after OC-related VT and if it could be attributed to thrombophilia.

Materials and Methods

60 women (age 33.0 ± 8.5 years) were investigated 5 – 64 (median 33) months after OC-related VT (patients) and compared to 63 apparently healthy women (controls). All women were tested for thrombophilia, activated partial thromboplastin time (APTT), fibrinogen, D-dimer, P-selectin and C-reactive protein. Thrombin generation was measured by Technothrombin® TGA assay. Overall haemostasis potential (OHP) assay with overall coagulation potential (OCP) and overall fibrinolytic potential (OFP) as supplementary parameters were measured by repeated fibrin formation and degradation registration.

Results

In patients increased endogenous thrombin potential (4205 ± 440 nM x min vs 4015 ± 421 nM x min, p = 0.017), increased OCP (22.6 ± 4.6 Abs-sum vs 20.8 ± 4.1 Abs-sum, p = 0.025), shorter APTT (30.9 ± 3.8 s vs 33.4 ± 3.6 s, p < 0.001) and lower antithrombin activity (99, 93-105% vs 104, 100-109%, p < 0.05) were observed. Thrombophilia was observed in 22/60 (36%) patients and in 5/63 (7.9%, p < 0.001) controls. The only significant difference between thrombophilic and non-thrombophilic patients was higher soluble P-selectin in the former subgroup (22, 20-33 μg/L vs 17, 12-22 μg/L, p = 0.012).

Conclusions

In women with a history of OC-related VT persistent hypercoagulability was observed, which, however was not augmented by the presence of thrombophilia.     

Who are at risk for thromboembolism after arthroplasty? A systematic review and meta-analysis

Background

Thromboembolism, including deep venous thrombosis and pulmonary embolism, is a grave threat to patients undergoing total joint replacement. Using a systematic review and meta-analysis we asked whether gene mutations or polymorphisms could be risk factors for thrombosis after arthroplasty.

Methods

We performed a comprehensive search of Medline, PubMed, Embase, Cochrane databases, China National Knowledge Infrastructure (CNKI), and Google Scholar, and identified 19 studies detailing genetic investigations of patients with thromboembolism following joint replacement.

Results

Our meta-analyses included 5149 patients who underwent arthroplasty surgery. Significant associations with venous thromboembolism were identified for factor G1691A (odds ratio (OR) 1.41, 95% confidence interval (CI) 1.03 - 1.94, p = 0.03), prothrombin G20210A (OR 2.16, 95% CI, 1.27- 3.69, p = 0.005), and MTHFR/C677T/TT (OR 2.36, 95% CI 1.03 - 5.42, p = 0.04) in Caucasian populations. No significant gene mutation was identified in Asian populations.

Conclusion

This study suggests a way to identify patients scheduled for arthroplasty who are at higher risk of thrombosis, enabling individualized treatment.     

Two years outcome of isolated distal deep vein thrombosis

Background

Isolated distal deep vein thrombosis (IDDVT) is frequently found in symptomatic outpatients, but its long term outcome is still uncertain.

Aims

To assess IDDVT long term outcome and the impact of IDDVT characteristics on outcome.

Methods

In a prospective, single center study we enrolled symptomatic outpatients in whom IDDVT was detected by whole-leg compression ultrasonography. Patients with provoked IDDVT were treated with low molecular weight heparins (LMWH) for 30 days while those with unprovoked IDDVT received with vitamin K antagonists (VKA) for three months. The primary end-point was the rate of the composite of pulmonary embolism (PE), proximal deep vein thrombosis (DVT), and IDDVT recurrence/extension during 24 month follow-up.

Results

90 patients (age 61 ± 18, male 48.9%) were enrolled. Risk factors for thrombosis were reduced mobility (34.4%), obesity (25.3%), surgery (15.6%), and previous DVT (15.6%) and cancer in 8 patients (8.9%). Eighty-eight patients were treated (56 with LMWH and 32 with VKA). During follow-up (median 24 ± 2 months), 17 events were recorded, which included 3 PE (two in cancer patients), 4 proximal DVTs (one in cancer patient) and 10 IDDVT. Male sex (HR 4.73 CI95%: 1.55-14.5; p = 0.006) and cancer (HR 5.47 CI95%: 1.76-17.6; p = 0.003) were associated with a higher risk of complications, whereas IDDVT anatomical characteristics, anticoagulant therapy type, and provoked IDDVT were not.

Conclusions

The risk of recurrent venous thromboembolism after IDDVT may be relevant in male patients or in patients with active cancer. Larger studies are needed to address this issue.     

Dose escalation of low molecular weight heparin in patients with recurrent cancer-associated thrombosis

Introduction

Patients with cancer-associated thrombosis are at a high risk of developing recurrent events despite anticoagulant therapy. Escalation of the dose of low molecular weight heparin (LMWH) has been suggested as a potential treatment option to manage these patients. We sought to confirm the benefit and risk of this management strategy in patients with recurrent cancer-associated thrombosis.

Material and Methods

A retrospective cohort study of consecutive cancer outpatients seen for management of a symptomatic recurrent cancer-associated thrombosis while on anticoagulation was undertaken. Objectively confirmed episodes of recurrent thrombosis were treated with either dose escalation of LMWH or initiation of therapeutic dose of LMWH in patients already anticoagulated with LMWH or vitamin K antagonist (VKA) respectively. Included patients were followed for a minimum of 3 months after the index recurrent event.

Results

Fifty-five cancer patients with a recurrent venous thromboembolism (VTE) despite anticoagulation were included. At the time of the recurrence, 89% of patients were on LMWH. The median time between the initial cancer-associated thrombosis to the index recurrent event was 2.3 months (range 0.1 to 30.4 months). Four patients (7.3%; 95% CI: 2.0 to 17.6%) had a second recurrent VTE during the 3-month follow-up period. Three patients (5.5%; 95% CI 1.1 to 15.1%) had major bleeding complications after dose escalation of LMWH. There were no recurrent fatal VTE or major bleeding episodes.

Conclusion

Escalating the dose of LMWH seems effective and safe for managing patients with recurrent cancer-associated thrombosis despite anticoagulant therapy.     

Circulating microparticle tissue factor,thromboembolism and survival in pancreaticobiliary cancers

Background

Tissue factor (TF), the physiologic initiator of coagulation, is over-expressed in pancreatic cancer, and is associated with a pro-coagulant and pro-angiogenic state. We hypothesized that in patients with pancreaticobiliary cancers (PBC), elevated circulating microparticle-associated TF (MP-TF) activity would be associated with thrombosis and worsened survival.

Patients and Methods

Clinical data and plasma were obtained for consecutive patients with PBC seen at Roswell Park Cancer Institute from 2005-08. MP-TF activity levels were measured using a TF-dependent FXa generation assay.

Results

The study population comprised 117 patients, including pancreatic (n = 80), biliary (n = 34) or unknown primary histologically consistent with PBC (n = 3). Of these, 52 patients (44.5%) experienced thromboembolism, including pulmonary embolism (n = 15), deep venous thrombosis (n = 21) and other arterial or venous events (n = 32). Mean TF was 2.15 (range 0.17- 31.01) pg/mL. Median survival was 98.5 days for MP-TF activity ≥ 2.5 pg/mL versus 231 days for MP-TF activity < 2.5 pg/mL (p < 0.0001). In multivariate analysis, elevated MP-TF activity was associated with both VTE (OR 1.4, 95% CI 1.1-1.6) and mortality (HR 2.5, 95% CI 1.4-4.5).

Conclusions

Elevated circulating MP-TF activity is associated with thrombosis and worsened survival in patients with PBC. MP-TF activity as a prognostic biomarker warrants further prospective evaluation.     

Lobectomy and postoperative thromboprophylaxis with enoxaparin improve blood hypercoagulability in patients with localized primary lung adenocarcinoma

Background

Patients with lung adenocarcinoma undergoing surgery are in high risk for VTE and receive routine post-operative thromboprophylaxis with LWMH.

Aim

We investigated markers of hypercoagulability in patients with primary localized adenocarcinoma and the modifications induced by lobectomy and postoperative administration of enoxaparin.

Materials and Methods

Patients suffering from localised primary lung adenocarcinoma (n = 15) scheduled for lobectomy were studied. The control group consisted of 15 healthy age and sex-matched individuals. Blood was collected before anaesthesia induction and after surgery, at several intervals until the 7th post-operative day. Samples were assessed for thrombin generation, phosphatidylserin expressing platelet derived microparticles expressing (Pd-MP/PS⁺), tissue factor activity (TFa), FVIIa and TFPI levels, procoagulant phospholipid dependent clotting time and anti-Xa activity.

Results

At baseline, patients showed increased thrombin generation and Pd-MP/PS⁺. After lobectomy thrombin generation significantly decreased. Administration of enoxaparin attenuated thrombin generation. In about 50% of samples collected post-operatively an increase of thrombin generation occurred despite the presence of the expected anti-Xa activity in plasma. At the 7th post-operative day, 3 out of 15 patients showed a significant increase of thrombin generation.

Conclusion

In patients with localized lung adenocarcinoma, hypercoagulability is characterized by high thrombin generation and increased concentration of Pd-MP/PS⁺. Tumor mass resection is related with attenuation of thrombin generation, which is inhibited by postoperative thromboprophylaxis with enoxaparin. The response to enoxaparin is not predicted by the concentration of the anti-Xa activity in plasma. The assessment of thrombin generation during prophylaxis with enoxaparin allows to identify patients with high residual plasma hypercoagulability.     

Risk factors for arterial thrombosis in antiphospholipid syndrome

Introduction

Antiphospholipid syndrome (APS) is associated with the risk of both arterial and venous thrombosis. However, it is not known which factors might determine the location of thrombosis.

Materials and Methods

To retrospectively characterize factors associated with the risk of arterial thrombosis in a cohort of APS patients. Analysis included laboratory and clinical criteria of APS, together with classical cardiovascular risk factors and the possible role of platelet integrin α₂β₁ (807 C/T) and α_IIbβ₃ (PI A1/2) genetic polymorphisms. We enrolled 163 APS patients (123 women and 40 men aged 21-75; mean age 43 years); 78 suffered from arterial thrombosis.

Results

There were no significant differences in the frequency or titers of different antiphospholipid antibodies with the exception of slightly increased frequency of IgG anticardiolipin antibodies (ACL) in the arterial thrombosis group. Livedo reticularis was observed significantly more often in the arterial thrombosis group, particularly in stroke patients.In univariate analysis arterial thrombosis was associated with male gender (OR-2,201; p = 0,033), arterial hypertension (OR-2,81; p = 0,002) and hypercholesterolemia (OR-3,69; p = 0,001). On multivariate analysis arterial hypertension (OR = 1,78; p = 0,008) and hypercholesterolemia (OR = 2,001; p = 0,002) remained as independent risk factors for arterial thrombosis. Platelet glycoprotein polymorphisms studied did not show any significant associations with arterial thrombosis in APS patients.

Conclusions

Among APS patients those with ACL IgG antibodies, having livedo reticularis, and suffering from hypertension an hypercholesterolemia are at the increased risk of arterial thrombosis.     

oxLDL – the molecule linking hypercoagulability with the presence of cardiovascular disease in hemodialyzed uraemic patients

Introduction

Patients with end-stage renal disease (ESRD) exhibit features of a hypercoagulable state, which may contribute to cardiovascular complications. Data from “in vitro” studies suggest that cell-free plasma lipids and lipoproteins may be capable to support thrombin generation. The aim of this study has been to establish the role of plasma oxidized LDL (oxLDL) in the coagulation activation in hemodialyzed (HD) patients with and without cardiovascular disease (CVD).

Materials and Methods

We examined relationship between a marker of coagulation activation – prothrombin fragments 1 + 2 (F_1 + 2), and plasma oxLDL levels in 60 HD patients with and without CVD and in 20 healthy controls.

Results

F_1 + 2 levels were significantly higher in HD patients than in controls, and they were higher in HD patients with CVD compared to those without CVD (p < 0.001). Conversely, oxLDL levels were similar in HD patients with CVD and healthy controls, whereas this parameter was lower in HD patients without CVD when compared to controls and patients with CVD (both p < 0.01). Close positive and independent association was between F_1 + 2 and oxLDL levels in HD patients. Nitrates treatment and the presence of pyelonephritis were associated with reduced oxLDL as well as hypercoagulability in HD patients with cardiovascular complications.

Conclusion

This study demonstrates the independent association between oxLDL and the marker of coagulation activation - F_1 + 2 in HD patients. This new observation may offer a better understanding of the complex mechanism leading to hypercoagulability, which is markedly intensified in these patients, particularly in those with CVD.     

Interobserver variability in the detection of cerebral venous thrombosis using CT venography with matched mask bone elimination

Objectives

Computed tomography venography (CTV) has proven to be a reliable imaging method in the evaluation of cerebral venous thrombosis with good correlation to magnetic resonance (MR) imaging and digital subtraction angiography (DSA). It is fast and widely accessible, especially in the emergency setting. For better visualization of vascular structures bone is often removed from the images. The purpose of this study was to evaluate the quality of a fully automatic bone removal method, matched mask bone elimination (MMBE), and to assess the interobserver variability of the CTV technique.

Patients and methods

Fifty patients with clinical suspicion of cerebral venous thrombosis underwent multislice CTV with MMBE post-processing. Axial source images and maximum intensity projections were retrospectively evaluated by two neuroradiologists for quality of bone removal and for the presence or absence of thrombosis in nine dural sinuses and five deep cerebral veins. A per sinus/vein and a per patient analysis (thrombosis in at least one sinus or vein) was performed and interobserver agreement was assessed.

Results

Both observers considered bone removal good in all patients (100%). Interobserver agreement per patient was excellent (κ = 0.83), with a full agreement in 47 of 50 patients (94%). The interobserver agreement per sinus or vein was good (κ = 0.76), with a full agreement in 679 of 700 sinuses or veins (97%).

Conclusion

CTV aided with MMBE is a robust technique for visualization of the intracranial venous circulation, removing bone effectively. CTV has high interobserver agreement for presence or absence of cerebral venous thrombosis.     

Superficial vein thrombosis,thrombin generation and activated protein C resistance as predictors of thromboembolic events in lupus and antiphospholipid patients. A prospective cohort study

Introduction

Predicting thrombosis in patients with systemic lupus erythematosus (SLE) and/or antiphospholipid antibodies (aPL) is still challenging. Our objective was to determine risk factors for thrombotic events including activated protein C (APC) resistance proven by a thrombin generation (TG) assay in patients with SLE and/or aPL.

Materials and methods

We performed a prospective cohort study in a French University Hospital and tertiary care center. Ninety-two consecutive patients with SLE and/or aPL without ongoing anticoagulant treatment were enrolled. The outcome was time to thrombotic event. We evaluated clinical and laboratory variables including APC sensitivity ratio (APCsr) determined by TG. An APCsr > 90th percentile of a control population indicated APC resistance.

Results

Patients were followed-up for a median duration of 35 months (inter-quartile range: 26 to 62; 320 patient-years). Thrombosis during follow-up occurred in 18 patients. In univariate analysis, together with history of hypertension, superficial vein thrombosis (SVT) and arterial thrombosis, patients with both aPL and APC resistance had an increased risk for incident thromboembolic events (HR, 3.67[95% confidence interval, 1.31 to 10.31]). In multivariate analysis, only history of hypertension (HR, 10.77 [95% confidence interval, 3.15 to 36.83]), SVT (HR, 7.45 [95% confidence interval, 2.25 to 24.66]) and arterial thrombosis (HR, 3.31 [95% confidence interval, 1.14 to 9.55]) remained independent risk factors.

Conclusions

History of thrombosis including seemingly benign SVT have a higher predictive value for incident thrombotic events in SLE or aPL patients than APC resistance proven by TG.     

Inferior vena cava thrombosis and its relationship with the JAK2V617F mutation and chronic myeloproliferative disease

Background

Splanchnic vein thrombosis (SVT) is a typical manifestation of polycythaemia vera (PV) or essential thrombocythaemia (ET). The recently discovered JAK2V617F somatic mutation is closely associated with chronic myeloproliferative disease (CMD). We investigated whether thrombosis involving the inferior vena cava (IVC) is also related to the JAK2V617F mutation or CMD.

Methods

Blood samples were obtained from 40 IVC thrombosis patients. Fifty-three patients with isolated lower extremity deep vein thrombosis (LE-DVT) and 20 SVT patients served as controls. The presence of the JAK2V617F mutation was assessed by real-time polymerase chain reaction (RT-PCR).

Results

The JAK2V617F allele was not detected in any of the IVC thrombosis patients but was detected in one patient (2%) with isolated LE-DVT. However, the mutation-carrying patient did not exhibit symptoms of CMD. Even after an observation period of 30 months, the patient's complete blood cell count did not exhibit any pathology. In contrast, the JAK2V617F allele was detected in four patients with SVT (20%) and CMD.

Conclusion

According to our data, there is no evidence that IVC thrombosis is associated with the JAK2V617F mutation or the presence of chronic myeloproliferative disease.     

Treatment patterns of venous thromboembolism in a real-world population: The Q-VTE study cohort

Background

Few studies have assessed treatment patterns of acute venous thromboembolism (VTE) in a real-world population. We aimed to describe anticoagulant treatment patterns for acute VTE using healthcare databases of Québec, Canada.

Methods

We used linked healthcare databases of the province of Québec, Canada to identify all incident cases of deep vein thrombosis (DVT) and pulmonary embolism (PE) between 2000 and 2009. We formed two patient cohorts, one with definite cases (definite VTE cohort, N = 40,776) and the other including cases with definite or probable VTE (any VTE cohort, N = 54,803) that were followed until death, end of health coverage, or end of study (December 31, 2009).

Results

In the definite cohort, 73.6% of subjects were dispensed an anticoagulant following the diagnosis of VTE. Of those who were dispensed a vitamin K antagonist (VKA), median duration of use was 61 days (interquartile range 89). VKA initiation was more likely in patients with pulmonary embolism than deep vein thrombosis alone (HR 1.62, 95% CI (1.58-1.66)). Among outpatients, those managed initially in the outpatient setting were less likely to initiate VKA therapy (HR 0.75, 95% CI (0.68-0.77)), while those requiring admission to hospital for VTE management were more likely to initiate (HR 1.81, 95% CI (1.76-1.87)). Findings were similar in the any VTE cohort.

Conclusion

Our study describes VTE treatment patterns in a real-world setting and suggests that there may be important gaps. These may include significant numbers of patients who did not initiate oral anticoagulant therapy, particularly in the outpatient setting, and shorter duration of oral anticoagulant use than recommended.     

Unprovoked proximal venous thrombosis is associated with an increased risk of asymptomatic pulmonary embolism

Introduction

Pulmonary embolism (PE) is common in patients with deep venous thrombosis (DVT). The outcome of DVT with concomitant symptomatic PE is worse than the outcome of isolated DVT. The risk factors for DVT and simultaneous asymptomatic PE have not been systematically studied yet.

Aim

To evaluate the frequency and risk factors for asymptomatic PE in patients with DVT.

Patients/methods

In 155 consecutive patients with a first episode of DVT and no PE symptoms, a ventilation-perfusion lung scan was performed. Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated and concentrations of D-dimer, high-sensitivity CRP (hsCRP), tissue plasminogen activator (t-PA) and troponin were measured. Laboratory tests for thrombophilia were performed.

Results

Asymptomatic PE was present in 36% of patients. No differences in gender, age, BMI and WHR were found between the patients with and without PE. PE was more common in patients with proximal DVT than in those with distal DVT (42% vs. 17%, p < 0.01), and in patients with unprovoked DVT compared to patients with provoked DVT (51% vs. 28%, p < 0.01). The risk of silent PE was the highest in patients with unprovoked proximal DVT (OR, 6.9; 95% CI, 2.3–21.0). Patients with asymptomatic PE had significantly higher values of D-dimer, hsCRP, t-PA and troponin than patients with isolated DVT.

Conclusions

Asymptomatic PE affected more than one third of patients with a first DVT. Unprovoked proximal DVT is the most important risk factor for the occurrence of silent PE.     

Development of a new laboratory test to evaluate antithrombin resistance in plasma

Introduction

We recently reported a variant prothrombin (p.Arg596Leu: prothrombin Yukuhashi) that confers antithrombin resistance to patients with hereditary thrombosis. To detect antithrombin resistance in plasma, we devised a laboratory test analyzing the kinetics of thrombin inactivation using antithrombin.

Materials and Methods

After incubation with prothrombin activator components (phospholipids, CaCl₂, and snake venom), samples were treated with excess antithrombin in the presence or absence of heparin for various time periods. Subsequently, H-D-Phe-Pip-Arg-p-nitoranilide was added and changes in absorbance/min (ΔA/min) were measured at 405 nm.

Results

After 1 min inactivation using antithrombin and heparin, the relative residual thrombin activity of recombinant mutant prothrombin (34.3% ± 2.2%) was higher than that of the wild-type (6.3% ± 1.2 %). After 30 min without heparin, the relative residual thrombin activity of recombinant mutant prothrombin (95.8% ± 0.4%) was higher than that of the wild-type (10.1% ± 1.7%), indicating that this assay could detect antithrombin resistance of the variant 596Leu prothrombin. Moreover, warfarinized plasmas from 2 heterozygous patients with prothrombin Yukuhashi mutation clearly showed higher values of the relative residual thrombin activity than those from 5 thrombosis patients lacking the mutation in the presence or absence of heparin.

Conclusions

We have devised a laboratory test to detect antithrombin resistance in plasma by analyzing the kinetics of thrombin inactivation using antithrombin. This assay may be useful for detecting antithrombin resistance in plasma, even in warfarinized patients.