Continuous intravenous heparin compared with intermittent subcutaneous heparin in the initial treatment of proximal-vein thrombosis

Time to Target Anti-Xa Level in Obese Vs Nonobese Patients Using an Adjusted Body Weight Heparin Infusion Protocol for the Treatment of Venous Thromboembolism

BACKGROUND

Unfractionated heparin (UFH) is a first-line option for the acute treatment of venous thromboembolism (VTE). Weight-based dosing protocols have demonstrated a decreased time to therapeutic anticoagulation, however, there are limited data on their utilization in obese patients, including the type of weight used.

OBJECTIVE

The purpose of this study was to determine equivalency in time to reach target antifactor-Xa (anti-Xa) for obese and nonobese patients using the same adjusted body weight (AdjBW)-based UFH infusion protocol.

METHODS

This was a single-center retrospective study of patients aged 18 years or older receiving an infusion of UFH for the treatment of VTE. The primary outcome was the median time to first target anti-Xa. Secondary outcomes included the percentage of first anti-Xa levels at 6 hours that were within, below, or above the target range and the median time to the second consecutive anti-Xa level within the target range. The safety outcome of evidence of major bleed was also evaluated.

RESULTS

Of the 166 patients assessed (75 obese and 91 nonobese), there was no observed difference in median time to first target anti-Xa in obese vs nonobese patients when using an AdjBW UFH protocol (12.45 vs 13.03 hours, P = 0.49). The percentage of patients achieving a target anti-Xa at first evaluation did not differ between obese and nonobese groups (32.0% vs 34.07%, P = 0.78). A total of 14 patients across groups experienced evidence of major bleed, with no observed difference between obese and nonobese groups (8.00% vs 8.89%, P = 0.84).

CONCLUSIONS AND RELEVANCE

There was no observed difference in median time to first target anti-Xa in obese vs nonobese patients when using an AdjBW heparin infusion protocol, with no observed difference in evidence of major bleed. Our findings support the use of AdjBW in weight-based UFH dosing.

Anticoagulants: From chance discovery to structure-based design

Taking a historical perspective, we review the discovery, pharmacology, and clinical evaluation of the old and new anticoagulants that have been approved for clinical use. The drugs are discussed chronologically, starting in the 1880s, and progressing through to 2024. The innovations in technology used to develop novel anticoagulants came in fits and starts and reflected the advances in science and technology over these decades, whereas the shift from anecdote to evidence-based use of anticoagulants was delayed until the principles of epidemiology and biostatistics were introduced into clinical trial design and to the approval process. Hirudin, heparin, and vitamin K antagonists were discovered by chance, and were used clinically before their mechanism of action was elucidated and before their net clinical benefits were evaluated in randomized clinical trials. Subsequent anticoagulants were designed based on a better understanding of the structure and function of coagulation proteins, including antithrombin, thrombin, and factor Xa, and underwent more rigorous preclinical and clinical evaluation before regulatory approval. By simplifying oral anticoagulation, the direct oral anticoagulants have revolutionized anticoagulation care and have enhanced the uptake of anticoagulation, but bleeding has not been eliminated and there is a need for more effective and convenient anticoagulants for thrombosis triggered by the contact pathway of coagulation. The newly developed factor XIa and XIIa inhibitors have the potential to address these unmet clinical needs and are undergoing clinical evaluation for several indications. SIGNIFICANCE STATEMENT: Anticoagulant therapy is the cornerstone of treatment and prevention of thrombosis, which remains a leading cause of morbidity and mortality worldwide. Elucidation of the structure and function of coagulation enzymes, their cofactors, and inhibitors, coupled with advances in structure-based design led to the discovery of more convenient, safer, and more effective anticoagulants that have revolutionized the management of thrombotic disorders.

Tinzaparin, an alternative to subcutaneous unfractionated heparin, in patients with severe and end-stage renal impairment: a retrospective observational single-center study

BACKGROUND

Tinzaparin could be easier to manage than unfractionated heparin in patients with severe renal impairment. However, clinical and pharmacologic data regarding its use in such patients are lacking.

OBJECTIVES

The aims of this study were to determine, in patients with estimated glomerular filtration rate (eGFR) of <30 mL.min⁻1, tinzaparin pharmacokinetics (PK) parameters using a population PK approach and bleeding and thrombotic complications.

METHODS

We performed a retrospective observational single-center study, including in-patients with eGFR of <30 mL.min⁻1 receiving prophylactic (4500 IU.d⁻1) or therapeutic (175 IU.kg⁻1.d⁻1) tinzaparin. Measured anti-Xa levels were analyzed using a nonlinear mixed-effects modeling approach. Individual predicted tinzaparin exposure markers at steady state were calculated for each patient and dosing regimen. The PK was also evaluated through Monte Carlo simulations based on the final covariate model parameter estimates.

RESULTS

Over a 22-month period, 802 tinzaparin treatment periods in 623 patients were analyzed: two-thirds received a prophylactic dose, 66% had an eGFR of <20 mL.min⁻1, and 25% were on renal replacement therapy. In patients for whom anti-Xa measurements were performed (n = 199; 746 values), PK parameters, profiles, and maximum plasma concentrations were comparable with those in patients without renal impairment or in healthy volunteers. In the whole population, major bleeding occurred in 2.4% and 3.5% of patients receiving prophylactic and therapeutic doses over a median 9- and 7-day treatment period, respectively. No patients had thrombotic complications.

CONCLUSION

Tinzaparin PK parameters and profiles were not affected by renal impairment. This suggests that tinzaparin, at therapeutic or prophylactic dose, could be an alternative to unfractionated heparin in hospitalized patients with severe renal impairment.

Management of Therapeutic-intensity Unfractionated Heparin: A Narrative Review on Critical Points

Nowadays, unfractionated heparin (UFH) use is limited to selected patient groups at high risk of both bleeding and thrombosis (patients in cardiac surgery, in intensive care unit, and patients with severe renal impairment), rendering its management extremely challenging, with many unresolved questions despite decades of use. In this narrative review, we revisit the fundamental concepts of therapeutic anticoagulation with UFH and address five key points, summarizing controversies underlying the use of UFH and discussing the few recent advances in the field: (1) laboratory tests for UFH monitoring have significant limitations; (2) therapeutic ranges are not well grounded; (3) the actual influence of antithrombin levels on UFH's anticoagulant activity is not well established; (4) the concept of UFH resistance lacks supporting data; (5) scarce data are available on UFH use beyond acute venous thromboembolism. We therefore identified key issues to be appropriately addressed in future clinical research: (1) while anti-Xa assays are often considered as the preferred option, we call for a vigorous action to improve understanding of the differences between types of anti-Xa assays and to solve the issue of the usefulness of added dextran; (2) therapeutic ranges for UFH, which were defined decades ago using reagents no longer available, have not been properly validated and need to be confirmed or reestablished; (3) UFH dose adjustment nomograms require full validation.

Anti-factor Xa as the preferred assay to monitor heparin for the treatment of pulmonary embolism

INTRODUCTION

The mainstay of acute pulmonary embolism (PE) treatment is anticoagulation. Timely anticoagulation correlates with decreased PE-associated mortality, but the ability to achieve a therapeutic activated partial thromboplastin time (aPTT) with unfractionated heparin (UFH) remains limited. Although some institutions have switched to a more accurate and reproducible test to assess for heparin's effectiveness, the anti-factor Xa (antiXa) assay, data correlating a timely therapeutic antiXa to PE-associated clinical outcomes remains scarce. We evaluated time to a therapeutic antiXa using intravenous heparin after PE response team (PERT) activation and assessed clinical outcomes including bleeding and recurrent thromboembolic events.

METHODS

This was a retrospective cohort study at NYU Langone Health. All adult patients ≥18 years with a confirmed PE started on IV UFH with >2 antiXa levels were included. Patients were excluded if they received thrombolysis or alternative anticoagulation. The primary endpoint was the time to a therapeutic antiXa level of 0.3-0.7 units/mL. Secondary outcomes included recurrent thromboembolism, bleeding and PE-associated mortality within 3 months.

RESULTS

A total of 330 patients with a PERT consult were identified with 192 patients included. The majority of PEs were classified as sub massive (64.6%) with 87% of patients receiving a bolus of 80 units/kg of UFH prior to starting an infusion at 18 units/kg/hour. The median time to the first therapeutic antiXa was 9.13 hours with 93% of the cohort sustaining therapeutic anticoagulation at 48 hours. Recurrent thromboembolism, bleeding and mortality occurred in 1%, 5% and 6.2%, respectively. Upon univariate analysis, a first antiXa <0.3 units/ml was associated with an increased risk of mortality [27.78% (5/18) vs 8.05% (14/174), p = 0.021].

CONCLUSION

We observed a low incidence of recurrent thromboembolism or PE-associated mortality utilizing an antiXa titrated UFH protocol. The use of an antiXa based heparin assay to guide heparin dosing and monitoring allows for timely and sustained therapeutic anticoagulation for treatment of PE.

Addressing the rising trend of high-risk pulmonary embolism mortality: Clinical and research priorities

BACKGROUND

Deaths from high-risk pulmonary embolism (PE) appear to have increased in the US over the last decade. Modifiable risks contributing to this worrisome trend present opportunities for physicians, researchers, and healthcare policymakers to improve care.

METHODS

We sought to contextualize contemporary, high-risk PE epidemiology and examine clinical trials, quality improvement opportunities, and healthcare policy initiatives directed at reducing mortality.

RESULTS

We observed significant and modifiable excess mortality due to high-risk PE. We identified several opportunities to improve care including: (1) rapid translation of forthcoming data on reperfusion strategies into clinical practice; (2) improved risk stratification tools; (3) quality improvement initiatives to address presumptive anticoagulation practice gaps; and (3) adoption of health policy initiatives to establish pulmonary embolism response teams and address the social determinants of health.

CONCLUSION

Addressing knowledge and practice gaps in intermediate and high-risk PE management must be prioritized and informed by forthcoming high-quality data. Implementation efforts are needed to improve acute PE management and resolve treatment disparities.

Association between venous thromboembolism rates and different prophylactic anticoagulation regimens in patients undergoing free flap reconstruction of the head and neck region

BACKGROUND

Venous Thromboembolism (VTE) is a serious complication after free tissue transfer to the head and neck (H&N). However, an optimal antithrombotic prophylaxis protocol is not defined in the literature. Enoxaparin 30 mg twice daily (BID) and heparin 5000 IU three times daily (TID) are among the most commonly used regimens for chemoprophylaxis. However, no studies compare these two agents in the H&N population.

METHODS

A cohort study of patients who underwent free tissue transfer to H&N from 2012 to 2021 and received either enoxaparin 30 mg BID or Heparin 5000 IU TID postoperatively. Postoperative VTE and hematoma events were recorded within 30 days of index surgery. The cohort was divided into two groups based on chemoprophylaxis. VTE and hematoma rates were compared between the groups.

RESULTS

Out of 895 patients, 737 met the inclusion criteria. The mean age and Caprini score were 60.6 [SD 12.5] years and 6.5 [SD 1.7], respectively. 234 [31.88%] were female. VTE and hematoma rates among all patients were 4.47% and 5.56%, respectively. The mean Caprini score between the enoxaparin (n = 664) and heparin (n = 73) groups was not statistically significant (6.5 ± 1.7 vs.6.3 ± 1.3, p = 0.457). The VTE rate in the enoxaparin group was significantly lower than in the heparin group (3.9% vs. 9.6%; OR: 2.602, 95% CI: 1.087-6.225). Hematoma rates were similar between the two groups (5.5% vs. 5.6%; OR: 0.982, 95% CI: 0.339-2.838).

CONCLUSIONS

Enoxaparin 30 mg BID was associated with a lower VTE rate while maintaining a similar hematoma rate compared to heparin 5000 units TID. This association may support the use of enoxaparin over heparin for VTE chemoprophylaxis in H&N reconstruction.

Evaluation of anti-Xa levels in patients with venous thromboembolism within the first 48 h of anticoagulation with unfractionated heparin

Background: A 2019 study by Prucnal and colleagues found that the majority of patients treated with unfractionated heparin for pulmonary embolism did not maintain therapeutic activated partial thromboplastin time levels during the first 48 h of therapy. Objective: The purpose of this study was to evaluate the ability of an institution's unfractionated heparin dosing protocol to achieve and maintain therapeutic anti-Xa levels within the first 48 h of therapy in patients with venous thromboembolism. Methods: This retrospective study included 205 patients from May 2016 through September 2020. Patients were divided into two cohorts: bolus plus infusion (N = 89) and infusion only (N = 116). The primary objective was to determine the number of patients who achieved at least one therapeutic level. Results: Overall, 200 patients (97.6%) had at least one therapeutic level with no statistically significant difference between cohorts (p = 0.65). No more than 60% of patients achieved a therapeutic level at any of the 6-h intervals throughout the timeframe. The median time to the first therapeutic level in the overall group was 12.8 h with no statistically significant difference between the bolus plus infusion and infusion-only cohorts (13.3 h versus 12.7 h, respectively, p = 0.48). Conclusions: Most patients were able to achieve at least one therapeutic level within the first 48 h, but fewer were able to maintain therapeutic levels. Further studies are warranted to determine whether alternative dosing strategies would yield consistent achievement of therapeutic levels and affect patient-oriented outcomes.

Clinical Studies with Anticoagulants that Have Changed Clinical Practice

Anticoagulant therapy is the cornerstone of treatment and prevention of arterial and venous thromboembolism. Taking a historical perspective, starting in the 1960s, and progressing through to 2022, we discuss key clinical trials of anticoagulants that have changed clinical practice, and examine obstacles encountered in bringing these anticoagulants to the clinic. The design of some of the early studies that shaped clinical practice was poor by current standards, but their results were influential because nothing better was available. Both heparin and vitamin K antagonists had been in clinical use for several decades before well-designed trials in the 1980s optimized their dosing and enhanced their safety and efficacy. Low-molecular-weight heparin then replaced unfractionated heparin because it had a more predictable dose-response and a longer half-life, thereby allowing it to be used conveniently in out-of-hospital settings. More recently, direct oral anticoagulants became the oral anticoagulants of choice for most indications because they were shown to be at least as safe and effective as vitamin K antagonists when used in fixed doses without the need for laboratory monitoring. The design of the trials that led to the approval of the direct oral anticoagulants was excellent, but further studies are required to optimize their dosing in selected patients who were underrepresented in these trials.

Between a Rock and a Hard Place: Anticoagulating an Adolescent with Post-Tonsillectomy Massive PE: A Case Report

OBJECTIVES

To report a case of a morbidly obese 17-year-old boy who presented 4 days post-tonsillectomy with acute deep venous thromboses and a massive pulmonary embolism. To describe a protocol and decision-making tree for providing anticoagulation in the immediate post-tonsillectomy period.

METHODS

A chart review and review of the literature.

RESULTS

The patient ultimately did well and had no bleeding from the tonsil beds or further thromboembolic complications. A review of the literature revealed no available data regarding the safety of anticoagulation in the immediate post-tonsillectomy period.

CONCLUSIONS

We propose that if anticoagulation is needed within 14 days of tonsillectomy, submaximal anticoagulation with a reversible and titratable anticoagulant may be optimal. A multidisciplinary team approach is needed for these complex cases. Future reporting and investigation of anticoagulation post-tonsillectomy is needed.

Application of anti-Xa assay in monitoring unfractionated heparin therapy in contemporary antithrombotic management

INTRODUCTION

Unfractionated heparin remains the most widely used agent in the prevention and acute treatment of thrombosis. Pharmacological complexities of this intriguing agent mandate frequent monitoring of its anticoagulant properties to maintain safe and effective hematological outcomes. Although activated partial thromboplastin time has been the standard test to monitor unfractionated heparin therapy for many decades, the anti-Xa assay has emerged as a substitute or adjunct in many institutions.

AREAS COVERED

This brief report outlines the key features of anti-Xa assay in monitoring unfractionated heparin in acute management of thrombosis in various contemporary settings, with emphasis on evidence for clinical outcomes. PubMed.gov database was utilized to obtain the pertinent literature.

EXPERT OPINION

The anti-Xa activity is primarily a reflection of UFH concentration and does not account for other hematological variables frequently present in contemporary anticoagulation management. The advantage of the anti-Xa assay in monitoring UFH therapy is predicated upon its limitations to account for global physiological hemostasis. There are significant disease and drug interactions that may potentially result in false in-vitro analysis of anti-Xa activity. Routine application of the anti-Xa assay is not evidence-based at this time.

Effectiveness of Venous Stenting for the Treatment of Lower Extremity Chronic Thrombotic Venous Obstruction

BACKGROUND

Patients with venous hypertension (HTN) have significant morbidity and poor quality of life. Deep venous thrombosis (DVT) and congenital defects that led to chronic outflow blockage are frequent causes of venous HTN. It is known that the venovenous bypass has been the standard method used in the treatment of chronic iliofemoral vein occlusions. Percutaneous recanalization has earlier been shown to be technically possible. With venoplasty and stenting, we used an aggressive endovascular strategy to treat the iliofemoral venous thrombotic occlusion.

METHODS

From May 2019 to April 2021, the medical records were reviewed for 63 patients diagnosed with symptomatic iliofemoral thrombotic occlusive disease and treated with venous stenting. The procedures' results were analyzed at Al-Azhar University Hospitals.

RESULTS

The medical records of 63 cases (44 women with a median age of 49.52 years), with chronic outflow block of iliofemoral vein segment that were treated with endovascular venous stenting, were reviewed retrospectively. Optimal success was obtained in 56 cases (88.9%). The twelve-month primary, assisted primary, and secondary patency rates were 76.8%, 80.4%, and 87.5%, respectively, while it was 73.2%, 80.4%, and 87.5%, respectively, after 2 years. The procedure-related complication rate was 6.3%. Puncture site hematoma was observed in 2 patients (3.2%). Early (30 days) stent thrombosis occurred in 2 patients (3.2%). Most importantly, there was no procedure-related mortality.

CONCLUSIONS

Endovascular treatment with balloon angioplasty and stenting of chronic venous thrombotic occlusions is an effective and safe procedure associated with a high technical rate of success and excellent patency rates. Accordingly, it should be considered the first line in the treatment of symptomatic iliofemoral vein occlusion.

Development of Selective FXIa Inhibitors Based on Cyclic Peptides and Their Application for Safe Anticoagulation

Coagulation factor XI (FXI) has emerged as a promising target for the development of safer anticoagulation drugs that limit the risk of severe and life-threatening bleeding. Herein, we report the first cyclic peptide-based FXI inhibitor that selectively and potently inhibits activated FXI (FXIa) in human and animal blood. The cyclic peptide inhibitor (K_i = 2.8 ± 0.5 nM) achieved anticoagulation effects that are comparable to that of the gold standard heparin applied at a therapeutic dose (0.3-0.7 IU/mL in plasma) but with a substantially broader estimated therapeutic range. We extended the plasma half-life of the peptide via PEGylation and demonstrated effective FXIa inhibition over extended periods in vivo. We validated the anticoagulant effects of the PEGylated inhibitor in an ex vivo hemodialysis model with human blood. Our work shows that FXI can be selectively targeted with peptides and provides a promising candidate for the development of a safe anticoagulation therapy.

Administration of Direct Oral Anticoagulant Immediately after Unfractionated Heparin Bolus for the Treatment of Intermediate-High-Risk Pulmonary Thromboembolism

Objective: This study aims to evaluate the efficacy and safety of direct oral anticoagulants (DOACs) after unfractionated heparin (UFH) bolus for the treatment of intermediate-high-risk pulmonary embolism. Materials and Methods: On the basis of initial treatment, 81 patients were divided into two groups: DOAC after UFH bolus infusion group (group D; n=32) and conventional therapy group (group C; n=49). The frequency of recurrence of venous thromboembolism (VTE) and bleeding within 6 months were compared. In addition, hospitalization length and thrombus reduction rate in the pulmonary artery on computed tomography (CT) at the chronic phase were assessed. Results: Recurrence of VTE was found in one (3.1%) and three patients (6.1%) (P=1.00) in groups D and C, respectively, whereas no bleeding events was found in group D and 8.2% of patients in group C (P=0.15). Group D showed shorter hospitalization (7.2±2.3 days) than group C (15.7±9.9 days; P<0.001). In the subset of patients with serial CT assessment (group D, n=20; group C, n=38), almost all thrombus of pulmonary artery were disappeared and the thrombus reduction rates were similar between the two groups (group D, 99.5%; group C, 97.1%; P=0.59). Conclusion: DOAC administration immediately after UFH bolus treatment has the same efficacy and safety, whereas hospitalization days were significantly shorter than the conventional treatment group.

Incidence and risk factors for PTT prolongation in patients receiving low-dose unfractionated heparin thromboprophylaxis

Low-dose unfractionated heparin (LDUH) prophylaxis decreases the incidence of venous thromboembolism (VTE) in hospitalized patients, but increases the risk of bleeding events. Patients who develop a prolonged activated partial thromboplastin time (aPTT) while on LDUH may be at higher risk for bleeding complications. To determine the incidence and risk factors for aPTT prolongation in hospitalized patients receiving LDUH thromboprophylaxis, we performed a retrospective pharmacoepidemiologic cohort study of adult patients admitted to an academic medical center from September 2013 through September 2015. Among 3857 patients with at least one aPTT checked within 24 h of LDUH administration, aPTT prolongation > 1.5 times the upper limit of normal occurred in 131 (3.4%). Age 68-78 years (OR 1.6, 95% CI 1.01-2.4), age > 78 years (OR 1.9, 95% CI 1.3-2.9), female gender (OR 1.9, 95% CI 1.4-2.5), black race (OR 1.6, 95% CI 1.1-2.3), low BMI (OR 1.8, 95% CI 1.3-2.5), being admitted to a surgical service (OR 0.5, 95% CI 0.3-0.8), and receipt of high-dose (> 10,000 units in a day) unfractionated heparin prophylaxis (OR 1.4, 95% CI 1.003-2.0), were independently associated with aPTT prolongation after LDUH exposure. LDUH VTE prophylaxis is associated with aPTT prolongation in 3.4% of general hospitalized patients. We demonstrated several factors independently associated with aPTT prolongation. Monitoring aPTT levels may be indicated for select patients on LDUH thromboprophylaxis who are at high risk or consequence of bleeding and for aPTT prolongation.

Bleeding and Thrombotic Risk in Low Dose Heparin Infusion as Compared to Standard Dose Heparin Infusion

Intravenous unfractionated heparin (UFH) remains one of the most commonly used anticoagulants in the hospital setting. The optimal protocol for initiation and maintenance of UFH has been difficult to determine. Over the past two decades, weight-based nomogram protocols have gained favor. Herein, we present a retrospective study of 377 patients at a single tertiary academic center treated with low intensity (LI) and standard intensity (SI) UFH protocols for therapeutic anticoagulation. UFH levels are measured by anti-Xa assay activity with therapeutic levels of 0.30 to 0.70 IU/mL for SI and 0.25 to 0.35 IU/mL for LI.  Patients treated on the LI protocol were more likely to have had a previous history of bleeding and lower baseline hemoglobin. Incidence of new or worsening thrombus while on UFH was comparable between both protocols (odds ratio (OR) 0.93, 95% confidence interval (CI) 0.29-2.98, p=0.899). Patients on LI protocol had higher incidence of bleeding while on UFH (OR 1.21, 95% CI 0.51-2.89, p=0.667). Our study thus suggests that the LI protocol may have comparable efficacy to the SI protocol in treating venous thromboembolism (VTE) and that target anti-Xa levels of 0.25 to 0.35 IU/mL may be more optimal in high-risk patients.

Thirty-day outcomes in patients with proximal deep vein thrombosis who discontinued anticoagulant therapy prematurely

INTRODUCTION

In patients receiving anticoagulation for deep vein thrombosis (DVT), a variety of reasons (including active bleeding or high-risk for bleeding) may lead into premature discontinuation of therapy (prior to completing 90 days). The relative frequency and clinical consequences of premature discontinuation in contemporary patients remain unknown.

METHODS

We used the data from RIETE, an international registry of patients with venous thromboembolism (VTE), to identify patients with proximal (above knee) lower limb DVT who prematurely discontinued anticoagulation. We assessed the incidence of the composite outcome: pulmonary embolism (PE)-related death, sudden death, or recurrent VTE within the subsequent 30 days after discontinuation and compared the risk of these events vs. the risk in patients without premature discontinuation, once adjusted for demographics and clinical factors.

RESULTS

Of 26,335 patients with proximal DVT recruited from 2001 to 2018, 1322 (5.02%) prematurely discontinued anticoagulation. Thirty days after discontinuation, 12 (0.91%) patients suffered fatal PE (n = 8) or sudden death (n = 4) and 33 (2.50%) had non-fatal recurrent VTE (PE = 15; recurrent DVT = 18). In patients with premature discontinuation, the 30-day incidence of the composite outcome was 1.62 per 1000 patient-days (95%CI: 0.00-3.80). During the first week after discontinuation, the incidence rate was 4.09 per 1000 patient-days (95%CI: 0.65-7.52). The adjusted odds of the composite outcome was 7.88 times (95%CI: 6.39-9.72) higher in patients who discontinued prematurely than in those without premature discontinuation.

CONCLUSION

Premature discontinuation of anticoagulation occurred in 5% of patients with proximal DVT, and was associated an 8-fold increased odds for the composite outcome.

Antithrombin During Extracorporeal Membrane Oxygenation in Adults: National Survey and Retrospective Analysis

The impact of antithrombin replacement during extracorporeal membrane oxygenation (ECMO) in adults remains unclear. This work comprises a survey, showing that antithrombin is routinely supplemented in many Italian ECMO-Centers, and a retrospective analysis on 66 adults treated with veno-venous ECMO and unfractionated heparin at our Institution. Twenty-four to 72 h after the beginning of ECMO, antithrombin activity was ≤70% in 47/66 subjects and activated partial thromboplastin time (aPTT) ratio was <1.5 in 20/66 subjects. Activated partial thromboplastin time ratio <1.5 was associated not with lower antithrombin activity (61 ± 17 vs. 63 ± 22%; p = 0.983) but with higher circulating level of C-reactive protein (23 ± 8 vs. 11 ± 9 mg/dl; p < 0.001). In 34 subjects who received antithrombin concentrate, antithrombin activity increased (from 54 ± 9 to 84 ± 13%; p < 0.001); the proportion of subjects with aPTT ratio ≥1.5 increased (from 21/34 [62%] to 31/34 [91%]; p = 0.004); heparin dosage remained constant (from 19 ± 7 to 19 ± 6 IU/kg/h; p = 0.543); and C-reactive protein decreased (from 17 ± 10 to 13 ± 9 mg/dl; p = 0.013). Among those with aPTT ratio <1.5, aPTT ratio remained <1.5 in 3 out of 13 subjects. Antithrombin is frequently supplemented during veno-venous ECMO although low antithrombin activity does not constantly impede, and antithrombin replacement does not constantly ensure, reaching the target aPTT ratio. Inflammation possibly affects the individual response to heparin.

Anticoagulation Management and Antithrombin Supplementation Practice during Veno-venous Extracorporeal Membrane Oxygenation

Background

There is a lack of consensus on how to manage anticoagulation during veno-venous extracorporeal membrane oxygenation, including antithrombin monitoring and supplementation. The authors’ aim was to determine current practice in a large number of extracorporeal membrane oxygenation centers around the world.

Methods

This was an electronic survey disseminated in 2018 to directors and coordinators of extracorporeal membrane oxygenation centers as well as to extracorporeal membrane oxygenation experts. Participating centers were classified according to some covariates that may affect practice, including 2017 gross national income per capita, primary patient population, and annual extracorporeal membrane oxygenation patient volume.

Results

The authors analyzed 273 unique responses from 50 countries. Systemic anticoagulation was routinely prescribed in 264 (96.7%) centers, with unfractionated heparin being the drug of choice in 255 (96.6%) of them. The preferred method to monitor anticoagulation was activated partial thromboplastin time in 114 (41.8%) centers, activated clotting time in 82 (30.0%) centers, and anti-factor Xa activity in 62 (22.7%) centers. Circulating antithrombin activity was routinely monitored in 133 (48.7%) centers. Antithrombin supplementation was routinely prescribed in 104 (38.1%) centers. At multivariable analyzes, routine antithrombin supplementation was associated with national income, being less likely in lower- than in higher-income countries (odds ratio, 0.099 [95% CI, 0.022 to 0.45]; P = 0.003); with primary patient population being more frequent in mixed (odds ratio, 2.73 [1.23 to 6.0]; P = 0.013) and pediatric-only centers (odds ratio, 6.3 [2.98 to 13.2]; P &lt; 0.001) than in adult-only centers; but not with annual volume of extracorporeal membrane oxygenation cases, being similarly common in smaller and larger centers (odds ratio, 1.00 [0.48 to 2.08]; P = 0.997).

Conclusions

There is large practice variation among institutions regarding anticoagulation management and antithrombin supplementation during veno-venous extracorporeal membrane oxygenation. The paucity of prospective studies and differences across institutions based on national income and primary patient population may contribute to these findings.

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Fifty years of research on antithrombotic therapy: Achievements and disappointments

The achievements with antithrombotic therapy over the past 50 years have been monumental and the disappointments relatively few. In this review, we will discuss, chronologically, the major developments of the two recognized classes of antithrombotics - anticoagulants and antiplatelet agents.

Unfractionated heparin infusion for treatment of venous thromboembolism based on actual body weight without dose capping

Controversy exists regarding the use of dose capping of weight-based unfractionated heparin (UFH) infusions in obese and morbidly obese patients. The primary objective of this study was to compare time to first therapeutic activated partial thromboplastin time (aPTT) in hospitalized patients receiving UFH for acute venous thromboembolism (VTE) among three body mass index (BMI) cohorts: non-obese (< 30 kg/m2), obese (30–39.9 kg/m2), and morbidly obese (⩾ 40 kg/m2). In this single-center, retrospective cohort study, patients were included if they ⩾ 18 years of age, had a documented VTE, and were on an infusion of UFH for at least 24 hours. Weight-based UFH doses were calculated using actual body weight. A total of 423 patients met the inclusion criteria, with 230 (54.4%), 146 (34.5%), and 47 (11.1%) patients in the non-obese, obese, and morbidly obese cohorts, respectively. Median times to therapeutic aPTT were 16.4, 16.6, and 17.1 hours in each cohort. Within 24 hours, the cumulative incidence rates for therapeutic aPTT were 70.7% for the non-obese group, 69.9% for the obese group, and 61.7% for the morbidly obese group (obese vs non-obese: HR = 1.02, 95% CI: 0.82–1.26, p = 0.88; morbidly obese vs non-obese: HR = 0.87, 95% CI: 0.62–1.21, p = 0.41). There was no significant difference in major bleeding events between BMI groups (obese vs non-obese, p = 0.91; morbidly obese vs non-obese, p = 0.98). Based on our study, heparin dosing based on actual body weight without a dose cap is safe and effective.

Perioperative management of laparoscopic surgery in a patient with protein S deficiency complications: A case report

Patients with protein S deficiency are prone to developing thrombosis. During laparoscopic surgery in patients with protein S deficiency, there is a risk of deep venous thromboembolism. In the present case, the patient was a 66-year-old man. He was diagnosed with colon cancer, and surgery was planned. Because of the presence of protein S deficiency, he required careful perioperative management for laparoscopic surgery. Surgery was successfully performed. On postoperative assessment, no thrombi were observed. Our approach of perioperative management might help in the treatment of patients with protein S deficiency.

Effect of Inferior Vena Cava Filter on Venous Thromboembolism Mortality in Japan - JROAD and JROAD-DPC Registry Analysis

Background: Previous randomized clinical studies have raised concerns about whether inferior vena cava filter (IVCF) can benefit patients with venous thromboembolism (VTE). The present study therefore investigated whether IVCF are associated with in-hospital mortality in Japan.

Methods and Results: This study was based on the Diagnosis Procedure Combination database in the Japanese Registry of All Cardiac and Vascular Datasets (JROAD-DPC). Of 2,368,165 patients included in JROAD-DPC, we identified 28,238 who were hospitalized with VTE between 2012 and 2014. We compared in-hospital mortality rates between patients with or without IVCF using propensity score (PS) matching. PS were estimated using logistic regression models in which IVCF was the dependent variable. The other variables consisted of age, sex, Charlson comorbidity index, anti-thrombotic agents and clinical disease status. Patients were aged 68±16 years, and 59.7% were female. Of 28,238 patients, 6,937 (24.5%) were treated with an IVCF. The overall in-hospital mortality was 4.3%. On PS-matched analysis in-hospital mortality was significantly lower with, than without, IVCF (3.1% vs. 4.4%, P<0.001; OR, 0.65; 95% CI: 0.54–0.79).

Conclusions: Having an IVCF was independently associated with lower in-hospital mortality in Japanese patients with VTE. This is in sharp contrast to the benefits of IVCF in other countries. The reasons for this difference require further investigation.

Accuracy, reproducibility and costs of different laboratory assays for the monitoring of unfractionated heparin in clinical practice: a prospective evaluation study and survey among Swiss institutions

OBJECTIVES

To investigate the accuracy, reproducibility and costs of different laboratory assays for the monitoring of unfractionated heparin (UFH) in clinical practice and to study test utilisation in Switzerland.

DESIGN

Prospective evaluation study and survey among Swiss hospitals and laboratories.

SETTING

Secondary care hospital in rural Switzerland (evaluation study); all Swiss hospitals and laboratories (survey).

PARTICIPANTS

All consecutive patients, monitored for treatment with UFH during two time periods, were included (May to July 2014 and January to February 2015; n=254).

OUTCOME MEASURES

Results of activated partial thromboplastin time (aPTT), thrombin time (TT), prothrombinase-induced clotting time (PiCT) and anti-Xa activity with respect to UFH concentration RESULTS: Spearman's correlation coefficient (r_s) with regard to anti-Xa activity was 0.68 (95% CI 0.60 to 0.75) for aPTT, 0.79 (0.69 to 0.86) for TT and 0.94 (0.93 to 0.95) for PiCT. The correlation (r_s) between anti-Xa activity and heparin concentration as determined by spiking plasma samples was 1.0 (1.0 to 1.0). The coefficient of variation was at most 5% for PiCT and anti-Xa activity (within-run as well as day-to-day variability). The total costs per test in Swiss Francs (SFr) were SFr23.40 for aPTT, SFr33.30 for TT, SFr15.70 for PiCT and SFr24.15 for anti-Xa activity. The various tests were employed in Swiss institutions with the following frequencies: aPTT 53.2%, TT 21.6%, anti-Xa activity 7.2%, PiCT 1.4%; 16.6% of hospitals performed more than one test.

CONCLUSIONS

The accuracy and reproducibility of PiCT and anti-Xa activity for monitoring of UFH was superior, and analytical costs were equivalent to or lower than aPTT and TT.

Thromboembolism prophylaxis in orthopaedics: an update

Venous thromboembolism (VTE) is a serious complication during and after hospitalization, yet is a preventable cause of in-hospital death.

Without VTE prophylaxis, the overall VTE incidence in medical and general surgery hospitalized patients is in the range of 10% to 40%, while it ranges up to 40% to 60% in major orthopaedic surgery. With routine VTE prophylaxis, fatal pulmonary embolism is uncommon in orthopaedic patients and the rates of symptomatic VTE within three months are in the range of 1.3% to 10%.

VTE prophylaxis methods are divided into mechanical and pharmacological. The former include mobilization, graduated compression stockings, intermittent pneumatic compression device and venous foot pumps; the latter include aspirin, unfractionated heparin, low molecular weight heparin (LMWH), adjusted dose vitamin K antagonists, synthetic pentasaccharid factor Xa inhibitor (fondaparinux) and newer oral anticoagulants. LMWH seems to be more efficient overall compared with the other available agents. We remain sceptical about the use of aspirin as a sole method of prophylaxis in total hip and knee replacement and hip fracture surgery, while controversy still exists regarding the use of VTE prophylaxis in knee arthroscopy, lower leg injuries and upper extremity surgery.

Cite this article: EFORT Open Rev 2018;3:136-148. DOI: 10.1302/2058-5241.3.170018

Anticoagulation in venous Thrombosis

Major studies addressing various aspects of the treatment of deep vein thrombosis are reviewed. It has lately been demonstrated that heparin should be dosed according to body weight and is preferably given as subcutaneous injections twice daily. Alternatively, low-molecular-weight heparins may be given in a fixed dose once daily, which does not require monitoring. Oral anticoagulation should be started concomitantly with heparin and targeted at an international normalized ratio of 2.0-3.0. This treatment should continue for a longer duration than previously accepted, in many cases for 6 months. For patients with contraindications to oral anticoagulation, secondary prophylaxis with a low-molecular-weight heparin is also effective and safe.

Below-knee deep vein thrombosis (DVT): diagnostic and treatment patterns

Background

Guidelines are lacking for isolated below-knee deep vein thrombosis (BKDVT). The American College of Chest Physicians (ACCP) suggests anticoagulation only if symptoms are severe, otherwise surveillance with follow-up ultrasound in 2 weeks is recommended. Yet clinical practice remains highly variable. Little is known about the natural history of BKDVT and how to best manage these patients.

Methods

A retrospective analysis was conducted of medical records from 2014-2016. Risk factors were assessed such as age, gender, malignancy, recent surgery, and history of DVT. Treatment decisions and outcomes were identified. Radiology reports were graded for clarity. Chi-square and logistic regression were used to correlate risk factors with outcomes and determine odds of treatment.

Results

New isolated BKDVT was identified in 102 patients. Patients were symptomatic or had previous pulmonary embolism (PE) or DVT in all cases. Eighteen were positive for PE at diagnosis (17.6% of all patients or 62.1% with chest CT). Malignancy was independently associated with PE (P=0.015); no other risk factors were significant. Treatment was not associated with clinical risk factors. The language used for radiology reports was highly variable and was associated with the decision to treat with anticoagulation. One hundred percent were treated (n=24) when the report stated "positive DVT" and 89.2% (n=58) were treated after an objective description without the word "DVT" (P=0.01). Treatment was much less likely if the report described BKDVT anatomically but was said to be "negative for DVT" (P<0.001). A total of 86.3% (n=88) of all patients were treated, compared to 46.2% (n=6) of patients in this group (n=13). IVC filters were placed in 3 patients. Of the 14 untreated patients, 5 received surveillance, 3 developed new proximal DVT, and none developed PE.

Conclusions

About 90% of patients diagnosed with BKDVT received anticoagulation after the initial diagnosis. Surveillance was not commonly recommended and is likely underutilized. Radiology reporting was highly variable and correlated with clinical treatment decisions, whereas other clinical risk factors did not. Describing BKDVT findings only in terms of being "positive" or "negative" for DVT may be inadequate.

Parenteral anticoagulants in heart disease: Current status and perspectives (Section II)

Anticoagulants are a mainstay of cardiovascular therapy, and parenteral anticoagulants have widespread use in cardiology, especially in acute situations. Parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins, the synthetic pentasaccharides fondaparinux, idraparinux and idrabiotaparinux, and parenteral direct thrombin inhibitors. The several shortcomings of unfractionated heparin and of low-molecular-weight heparins have prompted the development of the other newer agents. Here we review the mechanisms of action, pharmacological properties and side effects of parenteral anticoagulants used in the management of coronary heart disease treated with or without percutaneous coronary interventions, cardioversion for atrial fibrillation, and prosthetic heart valves and valve repair. Using an evidence-based approach, we describe the results of completed clinical trials, highlight ongoing research with currently available agents, and recommend therapeutic options for specific heart diseases.

Therapeutic monitoring of unfractionated heparin - trials and tribulations

INTRODUCTION

Heparin is one of the oldest biological medicines with an established role in prevention and treatment of arterial and venous thromboembolism. Published therapeutic ranges for unfractionated heparin (UFH) mostly precede the large increase in the number of activated partial thromboplastin time (APTT) reagent/instrument combinations that now show wide variability. Areas covered: This paper explores the use of UFH, the development of heparin therapeutic ranges (HTRs), and the strengths and limitations of the methods used to monitor heparin's anticoagulant effect. Expert commentary: Despite longstanding use of UFH for management of thromboembolic conditions, the optimal test for monitoring UFH remains undetermined. Although used extensively for monitoring UFH, routine APTT-derived HTRs are based on limited science that may have little relevance to current laboratory practice. Anti-FXa levels may provide better and more reliable HTRs; however, even these levels show considerable inter-laboratory variation, and there are insufficient clinical studies proving improved clinical efficacy. Alternative tests for monitoring UFH reported over time have not been proven effective nor feasible, secondary to technical or cost issues, or lack of general adoption. Thus, despite limited evidence of clinical utility, an uncomfortable marriage of convenience represented by heparin laboratory monitoring is unlikely to be terminated in the immediate future.

Description and Evaluation of the Implementation of a Weight-Based, Nurse-Driven Heparin Nomogram in a Tertiary Academic Medical Center

Weight-based, nurse-driven heparin nomograms are reported in the medical literature to improve the time it takes to reach a minimum threshold for anticoagulation without compromising patient safety in specific indications or patient populations. This is the first report in the literature of an institution-wide protocol implementation and evaluation of effectiveness with simultaneous transition to an electronic health record. The purpose of implementing this practice change at our institution was to standardize practice, improve time to reach therapeutic anticoagulation, and improve patient safety. We conducted a retrospective analysis utilizing a pre/postimplementation design to compare outcomes. The primary end point evaluated was the time to reach minimum threshold value for therapeutic anticoagulation. Additionally, we assessed the percentage of patients who reached minimum threshold therapeutic anticoagulation within 24 hours, the percentage of patients with a critically supratherapeutic activated partial thromboplastin time (aPTT) value (≥120 seconds) during therapy, and a description of heparin titration for the first 4 aPTT results with nomogram use. Overall time to therapeutic anticoagulation decreased from a mean 18.7 to 11.7 hours (hazard ratio [HR] 1.59; 95% confidence interval 1.22-2.08; P < .0005). Percentage of patients receiving therapeutic anticoagulation within 24 hours increased from 74.4 to 88.5 (odds ratio [OR 2.97, P = .002) and the percentage of patients with an aPTT ≥120 seconds remained constant at 49.9 versus 46.8 (OR 0.92, P = .73). This practice change reduced time to therapeutic anticoagulation without an increase in the proportion of patients with a critically supratherapeutic aPTT at our institution.

Inhaled Heparin: Therapeutic Efficacy and Recent Formulations

Heparin is well known for its anticoagulant and anti-inflammatory properties. Inhaled heparin regimens are increasingly being used to manage lung disease. It has been used to treat cystic fibrosis, thromboembolism, and pulmonary fibrosis, as well as bronchial asthma and asthma-induced airway hypersensitivity. Several preclinical studies attained some useful effects of heparin-administered, parenterally and through inhalation, treatment of lung disease. Besides, recent clinical trials suggest that inhaled heparin for lung diseases is beneficial and safe, but such data remain to be limited. In 2005, the orphan designation was granted by the European Commission for heparin sodium (inhalation use) for the treatment of cystic fibrosis. The positive results of heparin in the pulmonary route necessitate a focus on the preparation and evaluation of heparin in advanced drug delivery systems, namely nano/microparticles and liposomes. Through this pulmonary delivery, heparin is protected from enzymatic degradation within the airway. Heparin is thus passively targeted into the lungs, and long-lasting localized treatment is achieved. On the other hand, these systems have encountered several problems as follows: (1) polymers, such as poly-L-lactide-glycolic acid, poly (lactic acid), and chitosan, used to prepare heparin-loaded microparticle/nanoparticle (MP/NP) systems have not been granted approval for lung application by the FDA and (2) liposomal and NP formulation stability is the main problem of formulation design. We propose that additional in vitro and in vivo research is necessary to assess the clinical applicability of this treatment strategy. The present article discusses heparin treatments for lung diseases and the use of heparin and/or heparin-loaded drugs in advanced delivery systems through the pulmonary route.

Subcutaneous unfractionated heparin for the initial treatment of venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) is a prevalent and serious condition. Its medical treatment requires anticoagulation, usually with either unfractionated or low molecular weight heparin (LMWH). Administration of unfractionated heparin (UFH) is usually intravenous (IV) but can be subcutaneous as well. This is an update of a review first published in 2009.

OBJECTIVES

To assess the effects of subcutaneous UFH versus intravenous UFH, subcutaneous LMWH or any other anticoagulant drug for the initial treatment of venous thromboembolism.

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Specialised Register (last searched 30 November 2016) and CENTRAL (2016, Issue 10). The Cochrane Vascular Information Specialist also searched trials registries for details of ongoing or unpublished studies.

SELECTION CRITERIA

Randomised controlled trials comparing subcutaneous UFH to control, such as subcutaneous LMWH, continuous intravenous UFH or other anticoagulant drugs in participants with acute venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Two review authors (JS and LR) independently extracted data and assessed the risk of bias in the trials. We used meta-analyses when we considered heterogeneity low. The primary outcomes were symptomatic recurrent venous thromboembolism (deep vein thrombosis and/or pulmonary embolism), VTE-related mortality, adverse effects of treatment including major bleeding, and all-cause mortality. We calculated all outcomes using an odds ratio (OR) with a 95% confidence interval (CI).

MAIN RESULTS

We included one additional study in this update, bringing the total number of studies in the review to 16 randomised controlled trials, with a total of 3593 participants (1745 participants in the intervention group and 1848 participants in the control group). Eight trials used intravenous UFH as the control treatment, seven trials used LMWH, and one trial had three arms with both drugs as the controls. We did not identify trials comparing subcutaneous UFH with other anticoagulant drugs. We downgraded the quality of the evidence to low due to lack of blinding in studies, which led to a risk of performance bias, and also for imprecision, as reflected by the wide confidence intervals.When comparing subcutaneous versus IV UFH, there was no difference in the incidence of symptomatic recurrent VTE at three months (odds ratio (OR) 1.66, 95% confidence interval (CI) 0.89 to 3.10; 8 studies; N = 965; low-quality evidence), symptomatic recurrent deep vein thrombosis (DVT) at three months (OR 3.29, 95% CI 0.64 to 17.06; 1 study; N = 115; low-quality evidence), pulmonary embolism (PE) at three months (OR 1.44, 95% CI 0.73 to 2.84; 9 studies; N = 1161; low-quality evidence), VTE-related mortality at three months (OR 0.98, 95% CI 0.20 to 4.88; 9 studies; N = 1168; low-quality evidence), major bleeding (OR 0.91, 95% CI 0.42 to 1.97; 4 studies; N = 583; low-quality evidence) or all-cause mortality (OR 1.74, 95% CI 0.67 to 4.51; 8 studies; N = 972; low-quality evidence). There were no episodes of asymptomatic VTE occurring within three months of the commencement of treatment.When comparing subcutaneous UFH versus LMWH, there was no difference in the incidence of recurrent VTE at three months (OR 1.01, 95% CI 0.63 to 1.63; 5 studies; N = 2156; low-quality evidence), recurrent DVT at three months (OR 1.38, 95% CI 0.73 to 2.63; 3 studies; N = 1566; low-quality evidence), PE (OR 0.84, 95% CI 0.36 to 1.96; 5 studies, N = 1819; low-quality evidence), VTE-related mortality (OR 0.53, 95% CI 0.17 to 1.67; 8 studies; N = 2469; low-quality evidence), major bleeding (OR 0.72, 95% CI 0.43 to 1.20; 5 studies; N = 2300; low-quality evidence) or all-cause mortality (OR 0.73, 95% CI 0.50 to 1.07; 7 studies; N = 2272; low-quality evidence). There were no episodes of asymptomatic VTE occurring within three months of the commencement of treatment.

AUTHORS' CONCLUSIONS

There is no evidence of a difference between subcutaneous versus intravenous UFH for preventing VTE recurrence, VTE-related or all-cause mortality, and major bleeding. According to GRADE criteria, the quality of the evidence was low. There is also no evidence of a difference between subcutaneous UFH and LMWH for preventing VTE recurrence, VTE-related or all-cause mortality or major bleeding.

Aspirin plus tirofiban inhibit the thrombosis induced by Russell's viper venom

Background

Thrombosis and coagulopathy are the commonest hematological manifestations of envenomation of Russell’s viper venom (RVV). Factor X is activated by a factor X-activating enzyme from Russell’s viper venom (RVV-X) to start the coagulation cascade. We established an animal model with local ischemic effects induced by RVV. We tried to treat RVV envenomation with antiplatelets and anticoagulants without recourse to antivenom.

Methods

RVV was injected into the foot pad of mice. We observed the effects at different intervals and compared local changes in ischemia with drug treatment after 30 min.

Results

A combination of aspirin plus tirofiban could prevent the ischemic change induced by RVV. The antithrombotic effects of single-use of aspirin or tirofiban were better than single-use of heparin or clopidogrel.

Conclusion

The aspirin + tirofiban group had a better outcome with respect to prevention of tissue ischemia and gangrene. This indicates that the activation and aggregation of platelets is the major cause of thrombosis induced by RVV.

Diagnosis and Treatment of Lower Extremity Deep Vein Thrombosis: Korean Practice Guidelines

Lower extremity deep vein thrombosis is a serious medical condition that can result in death or major disability due to pulmonary embolism or post-thrombotic syndrome. Appropriate diagnosis and treatment are required to improve symptoms and salvage the affected limb. Early thrombus clearance rapidly resolves symptoms related to venous obstruction, restores valve function and reduces the incidence of post-thrombotic syndrome. Recently, endovascular treatment has been established as a standard method for early thrombus removal. However, there are a variety of views regarding the indications and procedures among medical institutions and operators. Therefore, we intend to provide evidence-based guidelines for diagnosis and treatment of lower extremity deep vein thrombosis by multidisciplinary consensus. These guidelines are the result of a close collaboration between interventional radiologists and vascular surgeons. The goals of these guidelines are to improve treatment, to serve as a guide to the clinician, and consequently to contribute to public health care.