Long term risk of symptomatic recurrent venous thromboembolism after discontinuation of anticoagulant treatment for first unprovoked venous thromboembolism event: systematic review and meta-analysis

Risk of recurrence after discontinuing anticoagulation in patients with COVID-19- associated venous thromboembolism: a prospective multicentre cohort study

Background

The clinical relevance of recurrent venous thromboembolism (VTE) after discontinuing anticoagulation in patients with COVID-19-associated VTE remains uncertain. We estimated the incidence rates and mortality of VTE recurrences developing after discontinuing anticoagulation in patients with COVID-19-associated VTE.

Methods

A prospective, multicenter, non-interventional study was conducted between March 25, 2020, and July 26, 2023, including patients who had discontinued anticoagulation after at least 3 months of therapy. All patients from the registry were analyzed during the study period to verify inclusion criteria. Patients with superficial vein thrombosis, those who did not receive at least 3 months of anticoagulant therapy, and those who were followed for less than 15 days after discontinuing anticoagulation were excluded. Outcomes were: 1) Incidence rates of symptomatic VTE recurrences, and 2) fatal PE. The rate of VTE recurrences was defined as the number of patients with recurrent VTE divided by the patient-years at risk of recurrent VTE during the period when anticoagulation was discontinued.

Findings

Among 1106 patients with COVID-19-associated VTE (age 62.3 ± 14.4 years; 62.9% male) followed-up for 12.5 months (p25-75, 6.3-20.1) after discontinuing anticoagulation, there were 38 VTE recurrences (3.5%, 95% confidence interval [CI]: 2.5-4.7%), with a rate of 3.1 per 100 patient-years (95% CI: 2.2-4.2). No patient died of recurrent PE (0%, 95% CI: 0-7.6%). Subgroup analyses showed that patients with diagnosis in 2021-2022 (vs. 2020) (Hazard ratio [HR] 2.86; 95% CI 1.45-5.68) or those with isolated deep vein thrombosis (vs. pulmonary embolism) (HR 2.31; 95% CI 1.19-4.49) had significantly higher rates of VTE recurrences.

Interpretation

In patients with COVID-19-associated VTE who discontinued anticoagulation after at least 3 months of treatment, the incidence rate of recurrent VTE and the case-fatality rate was low. Therefore, it conceivable that long-term anticoagulation may not be required for many patients with COVID-19-associated VTE, although further research is needed to confirm these findings.

Funding

Sanofi and Rovi, Sanofi Spain.

2023 ISTH update of the 2022 ISTH guidelines for antithrombotic treatment in COVID-19

Based on emerging evidence from the COVID-19 pandemic, the International Society on Thrombosis and Haemostasis (ISTH) guidelines for antithrombotic treatment in COVID-19 were published in 2022. Since then, at least 16 new randomized controlled trials have contributed additional evidence, which necessitated a modification of most of the previous recommendations. We used again the American College of Cardiology Foundation/American Heart Association methodology for assessment of level of evidence (LOE) and class of recommendation (COR). Five recommendations had the LOE upgraded to A and 2 new recommendations on antithrombotic treatment for patients with COVID-19 were added. Furthermore, a section was added to answer questions about COVID-19 vaccination and vaccine-induced immune thrombotic thrombocytopenia (VITT), for which studies have provided some evidence. We only included recommendations with LOE A or B. Panelists agreed on 19 recommendations, 4 for nonhospitalized, 5 for noncritically ill hospitalized, 3 for critically ill hospitalized, and 2 for postdischarge patients, as well as 5 for vaccination and VITT. A strong recommendation (COR 1) was given for (a) use of prophylactic dose of low-molecular-weight heparin or unfractionated heparin in noncritically ill patients hospitalized for COVID-19, (b) for select patients in this group, use of therapeutic-dose low-molecular-weight heparin/unfractionated heparin in preference to prophylactic dose, and (c) for use of antiplatelet factor 4 enzyme immunoassays for diagnosing VITT. A strong recommendation was given against (COR 3) the addition of an antiplatelet agent in hospitalized, noncritically ill patients. These international guidelines provide recommendations for countries with diverse healthcare resources and COVID-19 vaccine availability.

Overall haemostatic potential assay for prediction of outcomes in venous and arterial thrombosis and thrombo-inflammatory diseases

Thromboembolic diseases including arterial and venous thrombosis are common causes of morbidity and mortality globally. Thrombosis frequently recurs and can also complicate many inflammatory conditions through the process of 'thrombo-inflammation,' as evidenced during the COVID-19 pandemic. Current candidate biomarkers for thrombosis prediction, such as D-dimer, have poor predictive efficacy. This limits our capacity to tailor anticoagulation duration individually and may expose lower risk individuals to undue bleeding risk. Global coagulation assays, such as the Overall Haemostatic Potential (OHP) assay, that investigate fibrin generation and fibrinolysis, may provide a more accurate and functional assessment of hypercoagulability. We present a review of fibrin's critical role as a central modulator of thrombotic risk. The results of our studies demonstrating the OHP assay as a predictive biomarker in venous thromboembolism, chronic renal disease, diabetes mellitus, post-thrombotic syndrome, and COVID-19 are discussed. As a comprehensive and global measurement of fibrin generation and fibrinolytic capacity, the OHP assay may be a valuable addition to future multi-modal predictive tools in thrombosis.

The Role of Hereditary Thrombophilia Testing in Management of First-Time Pulmonary Embolism

AIM

Hereditary thrombophilia (HT) testing is frequently conducted during the evaluation of patients with pulmonary embolism (PE). However, the utility of routine HT testing in this setting is unclear. We sought to assess the association of HT with risk of recurrent venous thromboembolism (VTE) following first-time PE.

METHODS

We conducted a multi-hospital retrospective study. Two hundred and ninety (290) patients with a first-time PE, who had been tested for HT, completed at least 3 months of therapeutic anticoagulation (AC), subsequently discontinued AC, and were followed for at least 36 months thereafter, were included.

RESULTS

HT was present in 48 of the 290 included patients (17%). Median follow-up after discontinuing AC was 61 months (interquartile range, 43-79 months). The overall recurrence rate of VTE during follow-up was 58 per 290 (20%). A total of 47 of 242 patients (19%) in the HT-absent group had a recurrent VTE, compared with 11 of 48 (22%) in the HT-present group. There was no significant difference in VTE-free survival between groups on Kaplan-Meier analysis; the hazard ratio (HR) for VTE recurrence for those with HT compared to those without (HR HT-present: HT-absent) was 1.240 (95% confidence interval [CI] 0.614-2.502; p=0.548). On multivariable analysis, HT was not associated with risk of recurrent VTE (HR 1.262; 95% CI 0.640-2.488), and the only variable associated with VTE recurrence was unprovoked PE (HR 2.954; 95% CI 1.64-5.314).

CONCLUSIONS

These findings demonstrate that the presence of HT is not associated with the risk of recurrent VTE following first PE, and support limiting the use of HT testing among patients with first PE.

Tailored anticoagulant treatment after a first venous thromboembolism: protocol of the Leiden Thrombosis Recurrence Risk Prevention (L-TRRiP) study - cohort-based randomised controlled trial

INTRODUCTION

Patients with a first venous thromboembolism (VTE) are at risk of recurrence. Recurrent VTE (rVTE) can be prevented by extended anticoagulant therapy, but this comes at the cost of an increased risk of bleeding. It is still uncertain whether patients with an intermediate recurrence risk or with a high recurrence and high bleeding risk will benefit from extended anticoagulant treatment, and whether a strategy where anticoagulant duration is tailored on the predicted risks of rVTE and bleeding can improve outcomes. The aim of the Leiden Thrombosis Recurrence Risk Prevention (L-TRRiP) study is to evaluate the outcomes of tailored duration of long-term anticoagulant treatment based on individualised assessment of rVTE and major bleeding risks.

METHODS AND ANALYSIS

The L-TRRiP study is a multicentre, open-label, cohort-based, randomised controlled trial, including patients with a first VTE. We classify the risk of rVTE and major bleeding using the L-TRRiP and VTE-BLEED scores, respectively. After 3 months of anticoagulant therapy, patients with a low rVTE risk will discontinue anticoagulant treatment, patients with a high rVTE and low bleeding risk will continue anticoagulant treatment, whereas all other patients will be randomised to continue or discontinue anticoagulant treatment. All patients will be followed up for at least 2 years. Inclusion will continue until the randomised group consists of 608 patients; we estimate to include 1600 patients in total. The primary outcome is the combined incidence of rVTE and major bleeding in the randomised group after 2 years of follow-up. Secondary outcomes include the incidence of rVTE and major bleeding, functional outcomes, quality of life and cost-effectiveness in all patients.

ETHICS AND DISSEMINATION

The protocol was approved by the Medical Research Ethics Committee Leiden-Den Haag-Delft. Results are expected in 2028 and will be disseminated through peer-reviewed journals and during (inter)national conferences.

TRIAL REGISTRATION NUMBER

NCT06087952.

Safety profile of rivaroxaban in first-time users treated for venous thromboembolism in four European countries

BACKGROUND

The European rivaroxaban post-authorization safety study evaluated bleeding risk among patients initiated on rivaroxaban or vitamin K antagonists for the treatment and secondary prevention of venous thromboembolism in routine clinical practice.

METHODS

Cohorts were created using electronic healthcare databases from the UK, the Netherlands, Germany and Sweden. Patients with a first prescription of rivaroxaban or vitamin K antagonist during the period from December 2011 (in the UK, January 2012) to December 2017 (in Germany, December 2016) for venous thromboembolism indication, with no record of atrial fibrillation or recent cancer history, were observed until the occurrence of each safety outcome (hospitalization for intracranial, gastrointestinal, urogenital or other bleeding), death or study end (December 2018; in Germany, December 2017). Crude incidence rates of each outcome per 100 person-years were computed.

RESULTS

Overall, 44 737 rivaroxaban and 45 842 vitamin K antagonist patients were enrolled, mean age, 59.9-63.8 years. Incidence rates were similar between rivaroxaban and vitamin K antagonist users with some exceptions, including higher incidence rates for gastrointestinal bleeding in rivaroxaban users than in vitamin K antagonist users. Among rivaroxaban users, mortality and bleeding risk generally increased with age, renal impairment and diabetes.

CONCLUSIONS

This study provides further data from routine clinical practice that broadly support safety profile of rivaroxaban for VTE indication and complement findings from previous randomized clinical trials.

Secondary Prophylaxis of Venous Thromboembolism (VTE) with Low Dose Apixaban or Rivaroxaban: Results from a Patient Population with More than 2 Years of Median Follow-up

Background

Direct oral anticoagulants (DOACs) are widely used for the treatment and secondary prophylaxis of venous thromboembolism (VTE). Nowadays, DOACs represent the gold standard for long-term anticoagulation, with low-intensity DOACs administration becoming increasingly used worldwide in such scenario. Albeit low-intensity apixaban and rivaroxaban are approved for clinical usage as secondary VTE prophylaxis, there are few literature data regarding their efficacy and safety with a long follow-up.

Objectives

The aim of our study was to evaluate the efficacy and safety of low-dose DOACs for VTE secondary prophylaxis in patients at high risk of VTE recurrence.

Methods

We retrospectively evaluated patients who required long-term anticoagulant secondary prophylaxis to prevent recurrent VTE, treated with apixaban 2.5 mg BID or rivaroxaban 10 mg daily with a follow-up ≥ 12 months.

Results

The examined patients were 323. The median low-dose DOAC administration time was 25.40 months (IQR 13.93-45.90). Twelve (3.7%) VTE recurrences were observed; 21 bleeding events were registered (6.5%), including one episode of Major bleeding (MB) (0.3%), 8 Clinically relevant nonmajor bleeding (CRNMB) (2.5%) and 12 minor bleeding (3.7%). No statistically significant difference in the rate of VTE recurrence and/or bleeding events emerged between the rivaroxaban and apixaban groups. Patients included in the study for multiple episodes of VTE presented a significantly higher risk of a new VTE recurrence during low-intensity DOAC.

Conclusions

Our data suggest that low-dose DOACs may be effective and safe in secondary VTE prophylaxis in patients at high risk of VTE recurrence; however, attention might be needed in their choice in such a scenario for patients who experienced multiple episodes of VTE.

Long-Term Outcomes in Two-Year Follow-Up after Primary Treatment in Patients with a Prior Venous Thromboembolic Event: A Prospective, Observational, Real-Life Study

BACKGROUND

Patients with acute venous thromboembolism (VTE) need anticoagulation (AC) therapy for at least 3/6 months (primary treatment); after that period, they should receive a decision on the duration of therapy.

METHODS

This study examined the complications occurring during two years of follow-up (FU) in patients with a first VTE who were recruited in 20 clinical centers and had discontinued or prolonged AC. They were included in the START2-POST-VTE prospective observational study.

RESULTS

A total of 720 patients (53.5% males) who, after the completion of primary treatment, had received the decision to continue (n = 281, 39%; 76.1% with a DOAC) or discontinue (n = 439, 61%) AC were followed up for 2 years (total FU = 1318 years). The decision to prolong or suspend AC was made in similar proportions in patients with unprovoked or provoked index events. Courses of sulodexide treatment or Aspirin (100 mg daily) were prescribed to 20.3% and 4.5%, respectively, of the patients who discontinued AC. The bleeding rate was significantly higher in patients who extended AC (1.6% pt/y) than in those who stopped AC (0.1% pt/y; p = 0.001) and was higher in patients using standard-dose DOACs (3.1% pt/y) than in those using reduced-dose DOACs (0.4% pt/y). The recurrent VTE rates were similar between the two groups (2.2% pt/y during AC vs. 3% pt/y off AC).

CONCLUSION

Physicians' decisions about AC duration were independent of the unprovoked/provoked nature of the index event. The bleeding rate was higher in patients who continued AC using standard-dose DOACs. Surprisingly, the rate of thrombotic recurrence was not different between those who continued or discontinued AC. Randomized studies comparing different procedures to decide on the duration of AC after a first VTE are needed.

Electronic adaptation and danish cross-cultural translation of PEmb-QoL and VEINES-QoL/Sym for patients with venous thromboembolism

PURPOSE

Most patient-reported outcome (PROs) used in thrombosis research and clinical practice are delivered using technology like online questionnaires. However, only few have undergone formal electronic adaptation from paper to digital versions, threatening the validity and reliability of the PROs. The present study aimed to perform an electronic adaption and cross-cultural translation of two PROs measuring health-related quality of life in a Danish cohort of patients with venous thrombosis (VTE), specifically the VEINES-QoL/Sym questionnaire and the PEmb-QoL questionnaire.

METHODS

The electronic adaption and cross-cultural translation processes followed the international guidelines recommended by ISPOR. The migration of the questionnaires from paper to electronic versions was conducted in the Research Electronic Data Capture (REDCap). Following approval of the electronically adapted and translated versions, a pretest of the questionnaires was performed by cognitive interviewing patients with VTE recruited from a hospital setting.

RESULTS

Nine men and ten women between the age of 19 and 73 years participated in cognitive interviews. The questionnaires were successfully adapted from paper to electronic versions, and during the migration process only a few modifications to the content and format were made. Most comments were related to technicalities, e.g. touch functions and checkboxes. The cross-cultural translation of both questionnaires was satisfactory, as only minor rephrasing was required.

CONCLUSIONS

The original and Danish version of VEINES-QoL/Sym and PEmb-QoL were successfully adapted into electronic versions and are ready to share for REDCap users. Furthermore, the Danish versions of the two questionnaires have shown satisfactory face validity.

Qualitative experiences, values, and decisional needs of patients with unprovoked venous thromboembolism who suffer bleeding-"This pill will keep you alive tonight"

Background

Contemporary guidelines recommend extended-duration anticoagulation among patients with a first unprovoked venous thromboembolism (VTE). Little is known about whether this recommendation aligns with patient values after a bleeding complication.

Objectives

To explore the experiences, values, and decisional needs of patients with unprovoked VTE related to extended-duration treatment after an anticoagulant-associated bleed.

Methods

In this descriptive, qualitative study, face to face online semistructured interviews were conducted with patients with unprovoked VTE who had experienced bleeding and continued anticoagulant treatment in one academic hospital in Canada. Data were analyzed using directed content analysis to identify themes. Themes were mapped onto the Ottawa Decisional Support Framework to identify decisional needs.

Results

Between September and December 2021, 14 patients were interviewed (age 41-69 years; 9 females). Many patients were not aware of the option to stop anticoagulation and had limited understanding of the decision about treatment duration. Despite the negative quality-of-life impact of clinically relevant bleeding during VTE treatment, the majority continued anticoagulation due to emotional trauma of VTE diagnosis, a perception that bleeding would be more manageable than VTE recurrence, a desire to maintain a connection to subspecialty care or non-VTE related benefits (eg, cancer diagnosis, protection from COVID-19). Patients' decisional needs included lack of choice awareness, inadequate support for participation, lack of personalized risk stratification, and inadequate information on monitoring and managing heavy menstrual bleeding.

Conclusion

Despite the impact of anticoagulant-associated bleeding on quality of life, patients preferred continuing with anticoagulation for reasons extending beyond secondary VTE prevention. Effective decision-support interventions are needed to address unmet decisional needs.

Effects of Deep Venous Thrombosis Treatments on Early and Long-term Quality of Life: Medical Therapy vs. Systemic Thrombolysis vs. Pharmacomechanical Thrombolysis

OBJECTIVES

The present study aimed to compare the effects of medical therapy (MT), systemic thrombolysis (ST), and pharmacomechanical thrombolysis (PMT) methods used in our clinic for the treatment of deep venous thrombosis (DVT) on symptom reduction, the incidence of post-thrombotic syndrome (PTS) development, and quality of life.

METHODS

Data from160 patients diagnosed with acute DVT between January 2012 and May 2021 and treated and followed up in our clinic were retrospectively analyzed. The patients were divided into three groups according to treatment method. The patients who received MT treatment were defined as Group 1, anticoagulant treatment after ST as Group 2, and anticoagulant treatment after PMT as Group 3. The patients were called to the outpatient clinic, informed consent was obtained, EuroQol-5D-3 L (EQ-5D-3 L) scoring and Villalta scoring were performed, and anamnesis was taken.

RESULTS

A total of 160 patients were included, with 71 (44.4%) patients in Group 1, 45 (28.1%) in Group 2, and 44 (27.5%) in Group 3. The mean age was 48.9 ± 14.9 years for Group 1, 42.2 ± 10.8 for Group 2, and 29.0 ± 7.2 for Group 3. When the time to return to normal life and the EQ-5D-3 L score index were compared, the differences between Groups 1 and 2 and between Groups 1 and 3 were statistically significant (P = .000 and P = .000, respectively). However, the differences between Groups 2 and 3 were statistically insignificant (P = .213 andp = .074, respectively). When Villalta scores and EQ Visual Analogue Scale (EQ-VAS) scores were compared between groups, the difference between all groups was statistically significant (P = .000).

CONCLUSIONS

The medical treatment alone was observed to be insufficient in terms of symptomatic improvement, development of PTS, quality of life, and long-term complications. When the ST and PMT groups were compared, it was determined that PMT treatment was more advantageous in terms of EQ-VAS score and PTS development, although there was no statistical difference regarding complications, such as return to normal life and long-term quality of life, the incidence of recurrent DVT development, and pulmonary thromboembolism incidence.

Balancing risks of recurrent venous thromboembolism and bleeding with extended anticoagulation: a decision analysis

Background

A decision to stop or continue anticoagulation after 3 months of anticoagulation for venous thromboembolism (VTE) should be made by weighing individual risks of recurrence and bleeding.

Objectives

To determine the optimal ratio of recurrence risk reduction to increase the risk of bleeding in terms of maximizing quality-adjusted life years (QALYs) gained.

Methods

Using a microsimulation model, outcomes within 5 years were simulated after assigning extended treatment if absolute recurrence risk reduction outweighed absolute increase in clinically relevant bleeding risk (International Society on Thrombosis and Haemostasis definition), weighted by a certain ratio. Data were simulated based on the Bleeding Risk Study, a prospective cohort including patients after ≥3 months of anticoagulation for unprovoked VTE or provoked VTE with history of VTE. The VTE-PREDICT risk score was used to estimate 5-year risks of recurrent VTE and clinically relevant bleeding.

Results

Among 10,000 individuals (mean age, 60.2 years, 36% female), the ratio of 0.90 (95% CI, 0.51-3.40; ie, bleeding is considered 0.90 the severity of recurrent VTE), with 99% of patients assigned extended anticoagulation, was considered optimal and resulted in 93 (95% CI, -23 to 203) additional QALYs compared with the least favorable ratio (5.10, 0% extended anticoagulation). At the optimal ratio, treatment based on VTE-PREDICT yielded 44 (95% CI, -69 to 157) additional QALYs versus standard of care.

Conclusion

With the current evidence, the optimal ratio between relevant bleeding risk and absolute recurrence risk reduction remains uncertain. Our results confirm that clinical equipoise exists regarding the decision to stop or continue anticoagulation after initial VTE treatment, emphasizing the importance of shared decision-making.

The Vienna Prediction Model for identifying patients at low risk of recurrent venous thromboembolism: a prospective cohort study

BACKGROUND AND AIMS

Patients with unprovoked venous thromboembolism (VTE) have a high recurrence risk, and guidelines suggest extended-phase anticoagulation. Many patients never experience recurrence but are exposed to bleeding. The aim of this study was to assess the performance of the Vienna Prediction Model (VPM) and to evaluate if the VPM accurately identifies these patients.

METHODS

In patients with unprovoked VTE, the VPM was performed 3 weeks after anticoagulation withdrawal. Those with a predicted 1-year recurrence risk of ≤5.5% were prospectively followed. Study endpoint was recurrent VTE over 2 years.

RESULTS

A total of 818 patients received anticoagulation for a median of 3.9 months. 520 patients (65%) had a predicted annual recurrence risk of ≤5.5%. During a median time of 23.9 months, 52 patients had non-fatal recurrence. The recurrence risk was 5.2% [95% confidence interval (CI) 3.2-7.2] at 1 year and 11.2% (95% CI 8.3-14) at 2 years. Model calibration was adequate after 1 year. The VPM underestimated the recurrence risk of patients with a 2-year recurrence rate of >5%. In a post-hoc analysis, the VPM's baseline hazard was recalibrated. Bootstrap validation confirmed an ideal ratio of observed and expected recurrence events. The recurrence risk was highest in men with proximal deep-vein thrombosis or pulmonary embolism and lower in women regardless of the site of incident VTE.

CONCLUSIONS

In this prospective evaluation of the performance of the VPM, the 1-year rate of recurrence in patients with unprovoked VTE was 5.2%. Recalibration improved identification of patients at low recurrence risk and stratification into distinct low-risk categories.

The dos, don'ts, and nuances of thrombophilia testing

Considerable progress has been made in elucidating genetic and biologic risk factors for venous thromboembolism (VTE). Despite being able to identify heritable defects in a substantial proportion of patients with VTE, testing has not, in general, proven useful in management. Despite efforts to reduce inappropriate testing, it often falls to the hematologist to consult on patients having undergone thrombophilia testing. Through a series of cases, we discuss how D-dimer testing can be helpful in VTE recurrence risk stratification in younger women as well as how to approach patients with persistently elevated D-dimer levels in the absence of thrombosis. While elevated factor VIII coagulant activity levels are a significant risk factor for a first episode of VTE, its biologic basis is not fully understood, and studies have not shown it to be a useful predictor of recurrence. Abnormal results of genetic tests for methylene tetrahydrofolate reductase or plasminogen activator 1 promoter polymorphisms may be encountered, which carry little if any thrombotic risk and should never be ordered. We also discuss protein S deficiency, the most difficult of the hereditary thrombophilias to diagnose due to a wider "normal" range in the general population as compared with protein C, the presence of both free and bound forms in plasma, and the characteristics of the various assays in use. We also present a rare type of protein C deficiency that can be missed by functional assays using an amidolytic rather than a clotting end point.

Provoked vs minimally provoked vs unprovoked VTE: does it matter?

Venous thromboembolism (VTE) is a multifactorial disease, and its risk depends on exposure to risk factors and predisposing conditions. Based on their strength of association with a VTE episode, risk factors are classified as major or minor and determined using a temporal pattern to be transient or persistent. All patients with VTE should receive anticoagulant treatment for at least 3 months in the absence of an absolute contraindication. Beyond this period, selected patients may be candidates for an extended phase of anticoagulation aimed at secondary VTE prevention. The risk of recurrent VTE if anticoagulation is discontinued is probably the main driver of decision-making regarding extended treatment. The risk of recurrence after VTE associated with major risk factors is low if the risk factor is no longer present. In this case, treatment can be discontinued. If the major risk factor is persistent, anticoagulation should be continued. After VTE occurring in the absence of risk factors, anticoagulation should probably be continued indefinitely if the risk for bleeding is low and preferably with minimal effective doses of anticoagulants. VTE occurring after exposure to minor risk factors is probably the most challenging situation, especially if the clinical manifestation was acute pulmonary embolism. Understanding the actual role of minor risk factors in the occurrence of VTE helps in estimating the risk of recurrence and avoiding the dangers associated with unnecessary anticoagulation. The availability of safer strategies for anticoagulation could allow personalized strategies for secondary prevention of VTE.

Trajectories of Oral Anticoagulation Adherence and Associated Clinical Outcomes During Long-Term Anticoagulation Among Medicare Beneficiaries With Venous Thromboembolism

BACKGROUND

Little is known about anticoagulation medication nonadherence patterns impacting effectiveness and safety outcomes in clinical practice.

OBJECTIVE

We identified adherence trajectories of extended therapy with direct-acting oral anticoagulants (DOACs) and warfarin after 6 months initial anticoagulant therapy among Medicare beneficiaries with venous thromboembolism (VTE). We further assessed the associated recurrent VTE and major bleeding risks.

METHODS

Using group-based trajectory models, this retrospective cohort study identified distinct beneficiary subgroups with similar adherence patterns of extended-phase anticoagulant treatment (DOACs or warfarin) for patients with VTE who completed 6 months of initial anticoagulant treatment. We examined associations between adherence trajectories and risks of recurrent VTE and major bleeding using inverse probability treatment weighted Cox proportional hazards models.

RESULTS

Compared with no extended treatment, consistently high DOAC adherence was associated with decreased recurrent VTE risk (hazard ratio [HR] = 0.33, 95% confidence interval [CI] = 0.21-0.51) without increased major bleeding risk, and consistently high warfarin adherence was associated with decreased recurrent VTE risk (HR = 0.62, 95% CI = 0.40-0.95) and increased major bleeding risk (HR = 1.64, 95% CI = 1.12-2.41). Gradually declining adherence to DOACs (HR = 1.80, 95% CI = 1.07-3.03) or warfarin (HR = 2.34, 95% CI = 1.57-3.47) was associated with increased bleeding risk with no change in recurrent VTE risk.

CONCLUSION AND RELEVANCE

This real-world evidence suggests persistently adhering to extended DOAC therapy is associated with lower recurrent VTE risk without increasing major bleeding among Medicare beneficiaries with VTE. Persistently adhering to extended warfarin therapy was associated with lower recurrent VTE risk but higher major bleeding risk.

Association of type of oral anticoagulation with risk of bleeding in 45,114 patients with venous thromboembolism during initial and extended treatment-A nationwide register-based study

BACKGROUND

Safety data for different anticoagulant medications in venous thromboembolism (VTE) are scarce, in particular for extended treatment.

OBJECTIVES

To compare major bleeding rates depending on the choice of anticoagulation during initial (first 6 months) and extended treatment (6 months up to 5 years).

METHODS

A nationwide register-based study including cancer-free patients with a first-time VTE between 2014 and 2020. Cox proportional hazards models were used to compare bleeding rates.

RESULTS

We included 6558 patients on warfarin, 18,196 on rivaroxaban, and 19,498 on apixaban. At 6 months, 4750 (72.4%) remained on warfarin, 11,366 (62.5%) on rivaroxaban, and 11,940 (61.2%) on apixaban. During initial treatment, major bleeding rates were 3.86 (95% CI 3.14-4.58), 2.93 (2.55-3.31), and 1.95 (1.65-2.25) per 100 patient-years for warfarin, rivaroxaban, and apixaban, respectively, yielding adjusted hazard ratios (aHRs) of 0.89 (95% CI 0.71-1.12) for rivaroxaban versus warfarin, 0.55 (0.43-0.71) for apixaban versus warfarin, and 0.62 (0.50-0.76) for apixaban versus rivaroxaban. During extended treatment, major bleeding rates were 1.55 (1.19-1.91), 1.05 (0.85-1.26), and 0.96 (0.78-1.15) per 100 patient-years for warfarin, rivaroxaban, and apixaban, respectively, with aHRs of 0.72 (0.53-0.99) for rivaroxaban versus warfarin, 0.60 (0.44-0.82) for apixaban versus warfarin, and 0.85 (0.64-1.12) for apixaban versus rivaroxaban. Previous bleeding and increasing age were risk factors for bleeding both during initial and extended treatment.

CONCLUSION

Apixaban had a lower bleeding risk than warfarin or rivaroxaban during initial treatment. During extended treatment, bleeding risk was similar for apixaban and rivaroxaban, and higher with warfarin.

Anticoagulation strategies and long-term recurrence in patients with venous thromboembolism in the era of direct oral anticoagulants

BACKGROUND

There has been limited data on anticoagulation strategies and long-term recurrence in patients with venous thromboembolism (VTE) in the era of direct oral anticoagulant (DOAC).

METHODS

The COMMAND VTE Registry-2 is a multicenter retrospective cohort study enrolling 5197 consecutive patients with acute symptomatic VTE between January 2015 and August 2020 among 31 centers in Japan. In this primary report, the entire cohort was divided into 5 groups; major transient risk factors (N = 475, 9.1%), minor transient risk factors (N = 788, 15%), unprovoked (N = 1913, 37%), non-malignant persistent risk factors (N = 514, 9.9%), and active cancer (N = 1507, 29%) groups.

RESULTS

DOACs were administered in 79% of patients who received oral anticoagulants. Discontinuation of anticoagulant at 1 year was most frequent in the major transient risk factors group (57.2%, 46.3%, 29.1%, 32.0%, and 45.6%). The cumulative 5-year incidence of recurrent VTE was lowest in the major transient risk factors group (2.6%, 6.4%, 11.0%, 12.1%, and 10.1%, P < 0.001). The cumulative 5-year incidence of major bleeding was highest in the active cancer group (9.8%, 11.4%, 11.0%, 15.5%, and 20.4%, P < 0.001). After discontinuation of anticoagulation therapy, the cumulative 5-year incidence of recurrent VTE was highest in the unprovoked group (3.3%, 11.0%, 24.9%, 17.5%, and 11.8%, P < 0.001).

CONCLUSIONS

In this large real-world VTE registry, anticoagulation strategies and long-term recurrence widely differed depending on the baseline characteristics. Detailed risk stratifications of recurrent VTE could be useful for decision-making of anticoagulation strategies, whereas the bleeding-risk assessment might be especially important in the era of DOAC.

CLINICAL TRIAL REGISTRATION

URL: http://www.umin.ac.jp/ctr/index.htm Unique identifier: UMIN000044816.

Serial D-dimers after anticoagulant cessation in unprovoked venous thromboembolism: Data from the REVERSE cohort study

INTRODUCTION

While several risk stratification tools have been developed to predict the risk of recurrence in patients with an unprovoked venous thromboembolism (VTE), only 1 in 4 patients are categorized as low-risk. Rather than a one-time measure, serial D-dimer assessment holds promise to enhance the prediction of VTE recurrence after oral anticoagulant (OAC) cessation.

METHODS

Using the REVERSE cohort, we compared VTE recurrence among patients with normal D-dimer levels (<490 ng/mL among males under age 70, <500 ng/mL in others) at OAC cessation and 1-month follow-up, to those with an elevated D-dimer level at either timepoint. We also evaluated VTE recurrence based on absolute increase in D-dimer levels between the two timepoints (e.g., ∆D-dimer) according to quartiles.

RESULTS

Among 214 patients with serial D-dimer levels measured at OAC cessation and 1-month follow-up, an elevated D-dimer level at either timepoint was associated with a numerically higher risk of recurrent VTE than patients with normal D-dimer levels at both timepoints (6.9 % vs. 4.2 % per year, hazard ratio 1.6; 95 % CI 0.9-2.7). Among women with <2 HERDOO2 criteria, a normal D-dimer level at both timepoints predicted a very low risk of recurrent VTE during follow-up (0.8 % per year, 95 % CI 0.1-2.8). Irrespective of baseline value, recurrent VTE risk was only 3 % per year (95 % CI 1.4-5.6) among patients in the lowest ∆D-dimer quartile.

CONCLUSION

Serial normal D-dimer levels have the potential to identify patients at a low risk of recurrent VTE. In addition, ∆D-dimer, irrespective of its elevation above cutoff threshold, may predict recurrent VTE.

Subsegmental Pulmonary Embolism

Subsegmental pulmonary embolism (SSPE) is increasingly diagnosed with the growing use and technological advancements of multidetector computed tomography pulmonary angiography. Its diagnosis is challenging, and some presumed SSPE may actually represent imaging artifacts. Indirect evidence and results from small observational studies suggest that SSPE may be more benign than more proximal pulmonary embolism, and may thus not always require treatment. Therefore, guidelines suggest to consider a management strategy without anticoagulation in selected patients with SSPE at low risk of recurrent venous thromboembolism (VTE), in whom proximal deep vein thrombosis is excluded. Recently, a large prospective study among low-risk patients with SSPE who were left untreated showed a higher VTE recurrence risk than initially deemed acceptable by the investigators, and thus was prematurely interrupted after recruitment of 97% of the target population. However, the risk-benefit ratio of anticoagulation for low-risk patients with SSPE remains unclear, and results from randomized trials are needed to answer the question about their optimal management.

Small-Area Analysis of Treatment and Clinical Outcomes in Patients with Venous Thromboembolism in Denmark: A Nationwide Cohort Study

OBJECTIVES

 To investigate geographical variation in initiation and extended treatment with anticoagulants and clinical outcomes among patients hospitalized with first-time venous thromboembolism (VTE) in Denmark between 2007 and 2018.

METHODS

 Using nationwide health care registries, we identified all patients with a first-time VTE hospital diagnosis supported by imaging data from 2007 to 2018. Patients were grouped according to residential region (5) and municipality (98) at the time of VTE diagnosis. Cumulative incidence of initiation of and extended (beyond 365 days) anticoagulation treatment as well as clinical outcomes, including recurrent VTE, major bleeding, and all-cause death, were assessed. Sex- and age-adjusted relative risks (RRs) of the outcomes were computed when comparing across individual regions and municipalities. Overall geographic variation was quantified by computing the median RR.

RESULTS

 We identified 66,840 patients with a first-time VTE hospitalization. A difference in initiation of anticoagulation treatment of more than 20 percentage points between regions was observed (range: 51.9-72.4%, median RR: 1.09, 95% confidence interval [CI]: 1.04-1.13). Variation was also observed for extended treatment (range: 34.2-46.9%, median RR: 1.08, 95% CI: 1.02-1.14). The cumulative incidence of recurrent VTE ranged from 3.6 to 5.3% at 1 year (median RR: 1.08, 95% CI: 1.01-1.15). The difference remained after 5 years, and variation was also observed for major bleeding (median RR: 1.09, 95% CI: 1.03-1.15), whereas it appeared smaller for all-cause mortality (median RR: 1.03, 95% CI: 1.01-1.05).

CONCLUSION

 Substantial geographical variation in anticoagulation treatment and clinical outcomes occurs in Denmark. These findings indicate a need for initiatives to ensure uniform high-quality care for all VTE patients.

The risk of recurrent venous thromboembolism after discontinuation of anticoagulant therapy in patients with cancer-associated thrombosis: a systematic review and meta-analysis

Background

The optimal duration of anticoagulation in patients with active cancer and venous thromboembolism (VTE) is unknown. Current clinical guidelines advocate anticoagulant therapy for 3-6 months and to continue anticoagulant therapy for as long as the cancer is active. However, an adequate systematic review on the rate of recurrent VTE after discontinuation of anticoagulant therapy has not been performed.

Methods

For this systemic review and meta-analysis, we searched Embase.com, Medline (Ovid), Web of Science, Cochrane Library, and Google Scholar, from database inception to February 16, 2023, for studies on anticoagulant therapy in patients with cancer and the recurrence of venous thromboembolism after discontinuation of this therapy. We included randomised controlled trials and cohort studies published in English that reported on patients who met the following: cancer and a first VTE, completed at least 3 months of anticoagulant therapy, were followed after discontinuation of anticoagulant therapy, and with symptomatic recurrent VTE as an outcome during follow-up. Study-level data were requested from study authors. The primary outcome was the rate of recurrent VTE after discontinuation of anticoagulant therapy. A Bayesian random-effects meta-analysis was used to estimate the rate of recurrent VTE per 100 person-years for the pooled studies at different time intervals after discontinuation of anticoagulation therapy. We also calculated the cumulative VTE recurrence rate at different time intervals. Forest plots were mapped and the results were summarized by the median and 95% credible interval (CIs). This study was registered with PROSPERO, CRD42021249060.

Findings

Of 3856 studies identified in our search, 33 studies were identified for inclusion. After requesting study-level data, 14 studies involving 1922 patients with cancer-associated thrombosis were included. The pooled rate of recurrent VTE per 100 person-years after discontinuation of anticoagulant therapy was 14.6 events (95% credible interval 6.5-22.8) in the first three months, decreasing to 1.1 events (95% CI 0.3-2.1) in year 2-3, and 2.2 events (95% CI 0.0-4.4) in year 3-5 after discontinuation of anticoagulant therapy. The cumulative VTE recurrence rate was 28.3% (95% CI 15.6-39.6%) at 1 year; 31.1% (95% CI 16.5-43.8%) at 2 years; 31.9% (95% CI 16.8-45.0%) at 3 years; and 35.0% (95% CI 16.8-47.4%) at 5 years after discontinuation of anticoagulant therapy.

Interpretation

This meta-analysis demonstrates a high rate of recurrent VTE over time after discontinuation of anticoagulant therapy in patients with cancer-associated thrombosis. Our results support the current clinical guidelines to continue anticoagulant therapy in patients with active cancer.

Funding

Erasmus MC.

Thrombin Generation Is Associated with Venous Thromboembolism Recurrence, but Not with Major Bleeding and Death in the Elderly: A Prospective Multicenter Cohort Study

It is currently unknown whether thrombin generation is associated with venous thromboembolism (VTE) recurrence, major bleeding, or mortality in the elderly. Therefore, our aim was to prospectively study the association between thrombin generation and VTE recurrence, major bleeding, and mortality in elderly patients with acute VTE. Consecutive patients aged ≥65 years with acute VTE were followed for 2 years, starting from 1 year after the index VTE. Primary outcomes were VTE recurrence, major bleeding, and mortality. Thrombin generation was assessed in 551 patients 1 year after the index VTE. At this time, 59% of the patients were still anticoagulated. Thrombin generation was discriminatory for VTE recurrence, but not for major bleeding and mortality in non-anticoagulated patients. Moreover, peak ratio (adjusted subhazard ratio 4.09, 95% CI, 1.12-14.92) and normalized peak ratio (adjusted subhazard ratio 2.18, 95% CI, 1.28-3.73) in the presence/absence of thrombomodulin were associated with VTE recurrence, but not with major bleeding and mortality after adjustment for potential confounding factors. In elderly patients, thrombin generation was associated with VTE recurrence, but not with major bleeding and/or mortality. Therefore, our study suggests the potential usefulness of thrombin generation measurement after anticoagulation completion for VTE to help identify among elderly patients those at higher risk of VTE recurrence.

Assessing outcomes after thrombectomy with or without iliac vein stenting for young provoked DVT patients with iliac vein stenosis

BACKGROUND

This study aimed to assess the outcomes of thrombectomy with/without iliac vein stenting for young and transiently provoked DVT patients with iliac vein stenosis.

METHODS

This is a retrospective analysis of a prospectively collected multicenter database. Acute, transiently provoked DVT patients between 18 and 45 years old with iliac vein stenosis were included. All patients underwent thrombectomy. Outcomes including the Villalta score, the VEINES-QOL score, and adverse events were evaluated.

RESULTS

The data of 522 patients were collected of whom 75 were included, 58 underwent thrombectomy alone (nonstenting group) and 17 underwent thrombectomy and stenting (stenting group). Within 6 months, the Villalta score of patients in stenting group is lower than that of patients in nonstenting group (6 mo: 0.73 ± 0.77 vs. 1.41 ± 0.56, p = .0004), and the VEINES-QOL score of stenting group is higher than that of nonstenting group (6 mo: 89.00 ± 2.94 vs. 87.47 ± 3.72, p = .2141). At the following follow-ups, the Villalta score (12 mo: 0.56 ± 0.49 vs. 0.60 ± 0.58, p = .8266) and VEINES-QOL score (12 mo: 88.36 ± 2.29 vs. 88.31 ± 3.36, p = .9604) between the two groups are similar.

CONCLUSION

The stenting group had better efficacy within 6 months after intervention, while there was no significant difference in the symptom, signs, and quality of life between two groups after 6 months within a 2-year follow-up.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Trial Registry (Registration Number: ChiCTR2200056073).

Unprovoked Venous Thromboembolism: The Search for the Cause

Venous thromboembolism (VTE) is a common vascular disorder encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE). There is no data on global estimates of VTE prevalence and incidence. Most patients with unprovoked VTE require secondary thromboprophylaxis upon the completion of the primary treatment phase if they have no high bleeding risk. Risk prediction models can help identify patients at low VTE recurrence risk who may discontinue anticoagulation upon the completion of the primary treatment phase.

Inflammasome Signaling, Thromboinflammation, and Venous Thromboembolism

Venous thromboembolism (VTE) remains a major health burden despite anticoagulation advances, suggesting incomplete management of pathogenic mechanisms. The NLRP3 (NACHT-, LRR- and pyrin domain-containing protein 3) inflammasome, interleukin (IL)-1, and pyroptosis are emerging contributors to the inflammatory pathogenesis of VTE. Inflammasome pathway activation occurs in patients with VTE. In preclinical models, inflammasome signaling blockade reduces venous thrombogenesis and vascular injury, suggesting that this therapeutic approach may potentially maximize anticoagulation benefits, protecting from VTE occurrence, recurrence, and ensuing post-thrombotic syndrome. The nonselective NLRP3 inhibitor colchicine and the anti-IL-1β agent canakinumab reduce atherothrombosis without increasing bleeding. Rosuvastatin reduces primary venous thrombotic events at least in part through lipid-lowering independent mechanisms, paving the way to targeted anti-inflammatory strategies in VTE. This review outlines recent preclinical and clinical evidence supporting a role for inflammasome pathway activation in venous thrombosis, and discusses the, yet unexplored, therapeutic potential of modulating inflammasome signaling to prevent and manage VTE.

The Role of Biomarkers, Metabolomics, and COVID-19 in Venous Thromboembolism-A Review of Literature

In recent years, the field of venous thromboembolism has undergone numerous innovations, starting from the recent discoveries on the role of biomarkers, passing through the role of metabolomics in expanding our knowledge on pathogenic mechanisms, which have opened up new therapeutic targets. A variety of studies have contributed to characterizing the metabolic phenotype that occurs in venous thromboembolism, identifying numerous pathways that are altered in this setting. Among these pathways are the metabolism of carnitine, tryptophan, purine, and fatty acids. Furthermore, new evidence has emerged with the recent COVID-19 pandemic. Hypercoagulability phenomena induced by this viral infection appear to be related to altered von Willebrand factor activity, alteration of the renin-angiotensin-aldosterone system, and dysregulation of both innate and adaptive immunity. This is the first literature review that brings together the most recent evidence regarding biomarkers, metabolomics, and COVID-19 in the field of venous thromboembolism, while also mentioning current therapeutic protocols.

The vascular system and associated disorders

The vascular system, also called the circulatory system, is made up of the vessels that carry blood and lymph fluid through the body. The arteries and veins carry blood all over the body, sending oxygen and nutrients to the body tissues and taking away waste materials. This is a complex system in the body and can be affected by diseases with different pathogenic mechanisms. This article describes the pathophysiology of the main diseases of arteries and the venous system.

Optimal length of oral anticoagulant treatment for maximum benefit within 5 years after discontinuation of oral anticoagulants in patients with acute pulmonary embolism who require secondary thromboprophylaxis

BACKGROUND

Extended oral anticoagulant (OA) use is recommended in patients with acute pulmonary embolism (PE) who require secondary thromboprophylaxis. Nevertheless, the optimal length of OA use for the maximum long-term benefit in this patient population has been undefined to date.

METHODS

A retrospective study was performed to explore the role of different length of overall OA use (group 1 (≥1 year of OA use and <2 years of OA use), group 2 (≥2 years of OA use and <3 years of OA use), group 3 (≥ 3 years of OA use)) in outcomes within 5 years after OA discontinuation in patients with acute PE, who required secondary thromboprophylaxis. The primary outcome was mortality rates. The secondary outcomes comprised venous thromboembolism (VTE) recurrence, major bleeding during OA use and net clinical benefit. Net clinical benefit was defined as the composite of recurrent VTE and major bleeding.

RESULTS

For a total of 385 patients in group 1 (n=220), group 2 (n=110) and group 3 (n=55), the PE-related mortality in group 1 was higher than that in group 2 (p=0.034) and 3 (p=0.040), respectively, whereas were similar between groups 2 and 3 (p=1.000). The net clinical benefit in group 1 was less than that in group 2 (p=0.024), whereas similar with that in group 3 (p=0.526). The net clinical benefit was comparable between groups 2 and 3 (p=0.716). The length of OA use was positively associated with major bleeding (HR, 2.510 (0.293 to 3.485), p=0.001), whereas negatively associated with PE-related mortality (HR, 0.668 (0.196 to 2.832), p=0.025) and VTE recurrence (HR, 0.694 (0.174 to 2.300), p=0.036), respectively. The sensitivity and specificity of the length of OA use for the tendency of PE-related mortality was 70.2% and 46.2%, respectively. The area under the curve (AUC) was 0.654 (0.514 to 0.793) (p=0.029). The sensitivity and specificity of the length of OA use for the tendency of net clinical benefit was 86.8% and 64.3%, respectively. The AUC was 0.628 (0.565 to 0.690) (p<0.001) CONCLUSIONS: For patients with acute PE who require secondary thromboprophylaxis, 2 to 3 years (30 months preferred) of overall OA use after a diagnosis of acute PE could be an optimal length to achieve maximum benefit within 5 years after OA discontinuation.

Treatment-free survival after discontinuation of immune checkpoint inhibitors in mNSCLC: a systematic review and meta-analysis

Background

Recent research has suggested that patients with metastatic non-small cell lung cancer (mNSCLC) can achieve ongoing response after discontinuation of immune checkpoint inhibitor (ICI), but the best time to discontinue and the factors influencing efficacy remain unknown.

Method

A systematic search was performed for prospective clinical trials in patients with mNSCLC treated with ICIs published up to July 10, 2022. Eligible studies reported treatment-free survival (TFS) after discontinuation of ICI in partial objective responders. We calculated objective response rate (ORR) and TFS using random-effects models with respective 95% confidence intervals (Cis), and performed subgroup analyses to discuss the specific associations between ORR and TFS and the associated influencing factors.

Results

Across the 26 cohorts (3833 patients) included, the weighted mean ORR for all patients was 29.30% (95% CI 24.28% to 34.57%), with ICI plus chemotherapy (48.83%, 95% CI 44.36% to 53.30%) significantly higher than monotherapy (23.40%, 95% CI 18.53% to 28.62%). 395 patients were all patients who were complete or partial responders in the study, 194 discontinued ICI treatment, and nearly 35.5% achieved a durable response. No significant differences in TFS were found between subgroups according to the ICI regimen classification. Four cohorts of patients who completed 35 courses of treatment showed high levels of pooled TFS at 6 (80.18%, 95% CI 53.03% to 97.87%) and 12 months (66.98%, 95% CI 46.90% to 84.47%). Three cohorts of patients discontinued ICI treatment due to treatment-related adverse events (TRAEs) with the TFS rates at 6 (76.98%, 95% CI 65.79% to 86.65%) and 12 months (64.79%, 95% CI 50.20% to 78.19%).

Conclusion

Patients with mNSCLC were able to achieve ongoing responses after discontinuation of ICI. In conclusion, the results of this meta-analysis indicate that different treatment regimens, different drugs or different treatment durations may have an impact on TFS.

Influence of the 4G/5G polymorphism of plasminogen activator inhibitor-1 gene in acute unprovoked deep vein thrombosis and residual vein thrombosis

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is an important inhibitor of plasminogen activator, but the role of the PAI-1 4G/5G polymorphism in deep vein thrombosis (DVT) has been contradictory. In this study, we investigated the distribution of the PAI-1 4G/5G genotype in Chinese patients with DVT compared with healthy controls and the association between the PAI-1 4G/5G genotype and the persistence of residual venous occlusion (RVO) after different treatments.

METHODS

The PAI-1 4G/5G genotype was determined by fluorescence in situ hybridization in 108 patients with unprovoked DVT and 108 healthy controls. The patients with DVT were treated with catheter-based therapy or anticoagulation only. RVO was assessed by duplex sonography during the follow-up.

RESULTS

Thirty-two patients (29.6%) were homozygous for 4G (4G/4G), 62 patients (57.4%) were heterozygous for 4G/5G, and 14 patients (13%) were homozygous for 5G (5G/5G). No significant difference in genotype frequency was found between patients with DVT and controls. A total of 86 patients completed follow-up of ultrasound examination with a mean follow-up of 13.4 ±7.2 months. The results of patients with RVO were significantly different between homozygous 4G carriers (76.9%), heterozygous 4G/5G (58.3%), and homozygous carriers of 5G (33.3%) (P <.05) at the end of follow-up. Catheter-based therapy showed a better result in patients who were noncarriers of 4G (P = .045).

CONCLUSIONS

The PAI-1 4G/5G genotype was not a relevant predictor for DVT in Chinese patients, but is a risk factor for persistent RVO after idiopathic DVT.

Indefinite Anticoagulant Therapy for First Unprovoked Venous Thromboembolism : A Cost-Effectiveness Study

BACKGROUND

Clinical practice guidelines recommend indefinite anticoagulation for a first unprovoked venous thromboembolism (VTE).

OBJECTIVE

To estimate the benefit-harm tradeoffs of indefinite anticoagulation in patients with a first unprovoked VTE.

DESIGN

Markov modeling study.

DATA SOURCES

Systematic reviews and meta-analyses for the long-term risks and case-fatality rates of recurrent VTE and major bleeding. Published literature for costs, quality of life, and other clinical events.

TARGET POPULATION

Patients with a first unprovoked VTE who have completed 3 to 6 months of initial anticoagulant treatment.

TIME HORIZON

Lifetime.

PERSPECTIVE

Canadian health care public payer.

INTERVENTION

Indefinite anticoagulation with direct oral anticoagulants.

OUTCOME MEASURES

Recurrent VTE events, major bleeding events, costs in 2022 Canadian dollars (CAD), and quality-adjusted life-years (QALYs).

RESULTS OF BASE-CASE ANALYSIS

When compared with discontinuing anticoagulation after initial treatment in a hypothetical cohort of 1000 patients aged 55 years, indefinite anticoagulation prevented 368 recurrent VTE events, which included 14 fatal pulmonary emboli, but induced an additional 114 major bleeding events, which included 30 intracranial hemorrhages and 11 deaths from bleeding. Indefinite anticoagulation cost CAD $16 014 more per person and did not increase QALYs (-0.075 per person).

RESULTS OF SENSITIVITY ANALYSIS

Model results were most sensitive to the case-fatality rate of major bleeding and the annual risk for major bleeding during extended anticoagulation.

LIMITATION

The model assumed that risks for recurrent VTE and major bleeding measured in clinical trials at 1 year remained constant during extended anticoagulation.

CONCLUSION

Clinicians should use shared decision making to incorporate individual patient preferences and values when considering treatment duration for unprovoked VTE.

PRIMARY FUNDING SOURCE

Canadian Institutes of Health Research.

Comparison of Presentation, Treatment, and Outcomes of Venous Thromboembolism in Long-Term Immobile Patients Based on Age

BACKGROUND

Chronic immobility is prevalent, especially as people age. However, little is known about venous thromboembolism (VTE) outcomes in this population.

OBJECTIVE

To compare the presentation, treatment, and outcomes in chronically immobile (>8 weeks) patients older vs. younger than 75 who presented with VTE.

DESIGN

An observational international registry of patients with VTE.

PARTICIPANTS

Patients with acute VTE from the "Registro Informatizado Enfermedad TromboEmbolica" (RIETE) registry who were chronically immobile.

MAIN MEASURES

Baseline characteristics, presenting signs and symptoms, treatment and outcomes including major bleeding, recurrent VTE, and mortality.

KEY RESULTS

Among 4612 immobile patients (mean age 75.7 years, 34% male), 2127 (46%) presented with pulmonary embolism (PE). Patients >75 years presented more often with dyspnea (44% vs. 38%) or altered mental status (23% vs. 8.1%) and less often with chest pain (13% vs. 18%). The median duration of anticoagulation was shorter in older compared with younger patients [126 vs. 169 days]. During the first 90 days of anticoagulation, major bleeding (4.0% vs. 2.2%), PE-related death (2.5% vs. 1.1%), and bleeding-related death (0.78% vs. 0.26%) occurred more frequently among older patients. In 3550 patients who received anticoagulation beyond 90 days, older patients had more major bleeding [4.23 vs. 2.21 events per 100 patient years]. After anticoagulation discontinuation, recurrent VTE and major bleeding occurred in 11.8 and 9.25 and 1.49 and 0.69 events per 100 patient years, respectively, both in similar rates in both groups. In multivariable analysis, after stopping anticoagulation, VTE recurrence was inversely associated with long-term facility residence [OR 0.51 (0.28-0.92)], anemia [OR 0.63 (0.42-0.95)], and anticoagulation duration < 90 days [OR 0.38 (0.27-0.54)].

CONCLUSIONS

Chronically immobilized patients older than 75 years presenting with VTE experience a high rate of adverse events including major bleeding and recurrent VTE. When considering treatment beyond 90 days, we should account for bleeding, recurrence risk, and associated mortality.

Venous thromboembolism recurrence among one-and-done direct oral anticoagulant users: a retrospective longitudinal study

BACKGROUND

Direct oral anticoagulants (DOACs) are the American Society of Hematology guideline-recommended treatment for venous thromboembolism (VTE) in the United States (US).

AIM

To compare risk of VTE recurrence between patients who, following the first fill, discontinued ("one-and-done") versus those who continued ("continuers") DOACs.

METHOD

Open source US insurance claims data (04/1/2017 to 10/31/2020) were used to select adult patients with VTE initiated on DOACs (index date). Patients with only one DOAC claim during the 45-day landmark period (starting on the index date) were classified as one-and-done and the remaining as continuers. Inverse probability of treatment weighting was used to reweight baseline characteristics between cohorts. VTE recurrence based on the first post-index deep vein thrombosis or pulmonary embolism event was compared using weighted Kaplan-Meier and Cox proportional hazard models from landmark period end to clinical activity or data end.

RESULTS

27% of patients initiating DOACs were classified as one-and-done. After weighting, 117,186 and 116,587 patients were included in the one-and-done and continuer cohorts, respectively (mean age 60 years; 53% female; mean follow-up 15 months). After 12 months of follow-up, the probability of VTE recurrence was 3.99% and 3.36% in the one-and-done and continuer cohorts; the risk of recurrence was 19% higher in the one-and-done cohort (hazard ratio [95% confidence interval] = 1.19 [1.13, 1.25]).

CONCLUSION

Substantial proportion of patients discontinued DOAC therapy after the first fill, which was associated with significantly higher risk of VTE recurrence. Early access to DOACs should be encouraged to reduce the risk of VTE recurrence.

Clinical profile and outcome of isolated pulmonary embolism: a systematic review and meta-analysis

Background

Isolated pulmonary embolism (PE) appears to be associated with a specific clinical profile and sequelae compared to deep vein thrombosis (DVT)-associated PE. The objective of this study was to identify clinical characteristics that discriminate both phenotypes, and to characterize their differences in clinical outcome.

Methods

We performed a systematic review and meta-analysis of studies comparing PE phenotypes. A systematic search of the electronic databases PubMed and CENTRAL was conducted, from inception until January 27, 2023. Exclusion criteria were irrelevant content, inability to retrieve the article, language other than English or German, the article comprising a review or case study/series, and inappropriate study design. Data on risk factors, clinical characteristics and clinical endpoints were pooled using random-effects meta-analyses.

Findings

Fifty studies with 435,768 PE patients were included. In low risk of bias studies, 30% [95% CI 19-42%, I ² = 97%] of PE were isolated. The Factor V Leiden [OR: 0.47, 95% CI 0.37-0.58, I ² = 0%] and prothrombin G20210A mutations [OR: 0.55, 95% CI 0.41-0.75, I ² = 0%] were significantly less prevalent among patients with isolated PE. Female sex [OR: 1.30, 95% CI 1.17-1.45, I ² = 79%], recent invasive surgery [OR: 1.31, 95% CI 1.23-1.41, I ² = 65%], a history of myocardial infarction [OR: 2.07, 95% CI 1.85-2.32, I ² = 0%], left-sided heart failure [OR: 1.70, 95% CI 1.37-2.10, I ² = 76%], peripheral artery disease [OR: 1.36, 95% CI 1.31-1.42, I ² = 0%] and diabetes mellitus [OR: 1.23, 95% CI 1.21-1.25, I ² = 0%] were significantly more frequently represented among isolated PE patients. In a synthesis of clinical outcome data, the risk of recurrent VTE in isolated PE was half that of DVT-associated PE [RR: 0.55, 95% CI 0.44-0.69, I ² = 0%], while the risk of arterial thrombosis was nearly 3-fold higher [RR: 2.93, 95% CI 1.43-6.02, I ² = 0%].

Interpretation

Our findings suggest that isolated PE appears to be a specific entity that may signal a long-term risk of arterial thrombosis. Randomised controlled trials are necessary to establish whether alternative treatment regimens are beneficial for this patient subgroup.

Funding

None.

Venous Thromboembolism Recurrence Among Patients Who Abandon Oral Anticoagulant Therapy in the USA: A Retrospective Longitudinal Study

INTRODUCTION

Among patients with venous thromboembolism (VTE), direct oral anticoagulants (DOACs) are recommended for preventing thromboembolic recurrence, complications, and mortality. This study compared the risk of VTE recurrence among patients who abandoned their first DOAC fill ("abandoners") relative to patients who did not ("non-abandoners").

METHODS

Adults with VTE who were prescribed DOACs were selected from Symphony Health, an ICON plc Company, PatientSource®, April 1, 2017 to October 31, 2020. Patients who abandoned their first (index) DOAC fill were classified as abandoners and patients with an approved index DOAC fill as non-abandoners. Baseline characteristics were balanced between cohorts using inverse probability of treatment weighting. VTE recurrence based on the first post-index VTE event (deep vein thrombosis or pulmonary embolism) was ascertained and compared between cohorts using weighted Kaplan-Meier and Cox proportional hazard models during the follow-up period (i.e., index DOAC fill date to end of clinical activity or data availability).

RESULTS

After weighting, 152,443 and 153,931 patients comprised the abandoner and non-abandoner cohorts, respectively (mean age 60 years; 53% female; mean follow-up duration 15 months). After 3 months of follow-up, the probability of VTE recurrence was 7.74% in the abandoner cohort and 4.65% in the non-abandoner cohort; the risk of recurrence was 72% higher in the abandoner versus non-abandoner cohort (hazard ratio [95% confidence interval] 1.72 [1.64, 1.82]; p < 0.0001). At 12 months, the probability of recurrence was 9.91% in the abandoner cohort and 6.89% in the non-abandoner cohort; the risk of recurrence was 53% higher in the abandoner versus non-abandoner cohort (1.53 [1.46, 1.61]; p < 0.0001).

CONCLUSION

Patients abandoning the first DOAC fill had significantly higher risk of VTE recurrence compared to patients who did not abandon the first fill. Ensuring proper access and encouraging early and continuous use of DOACs may help prevent severe and fatal complications among patients with VTE.

Exploring the Clinical Efficacy of Venous Thromboembolism Management in Saudi Arabian Hospitals: An Insight into Patient Outcomes

Venous thromboembolism (VTE) is a common condition that can recur, leading to multiple therapeutic strategies to prevent it. The aim of this study was to explore the clinical efficacy of VTE management in Saudi Arabian hospitals and to gain insights into patient outcomes. A retrospective single-center study was conducted that retrieved the data of all patients with VTE registered from January 2015 to December 2017. Patients of all age groups were included if they attended the thrombosis clinic at KFMC during the data collection period. The study analyzed the various therapeutic strategies used for VTE and their effect on patient outcomes. The results showed that 14.6% of the patients had provoked VTE, with a higher incidence among females and younger patients. The most commonly prescribed treatment was combination therapy, followed by warfarin, oral anticoagulants, and factor Xa inhibitor. Despite being prescribed treatment, 74.9% of the patients experienced recurrence of VTE. There was no associated risk factor for recurrence in 79.9% of the patients. Thrombolytic therapy and catheter-directed thrombolysis were found to be associated with a lower risk of VTE recurrence, while anticoagulation therapy, including oral anticoagulants, was associated with a higher risk. Vitamin K antagonist (warfarin) and factor Xa inhibitor (rivaroxaban) had a significant positive association with VTE recurrence, while the use of a direct thrombin inhibitor (dabigatran) showed a lower risk, but it was not statistically significant. The results of the study highlight the need for further research to determine the most effective therapeutic strategy for VTE management in Saudi Arabian hospitals. The findings also suggest that anticoagulation therapy, including oral anticoagulants, may increase the risk of VTE recurrence, while thrombolytic therapy and catheter-directed thrombolysis may lower the risk.

Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE): Outcomes at 12 months

OBJECTIVE

To determine the safety and effectiveness of vena cava filters (VCFs).

METHODS

A total of 1429 participants (62.7 ± 14.7 years old; 762 [53.3% male]) consented to enroll in this prospective, nonrandomized study at 54 sites in the United States between October 10, 2015, and March 31, 2019. They were evaluated at baseline and at 3, 6, 12, 18, and 24 months following VCF implantation. Participants whose VCFs were removed were followed for 1 month after retrieval. Follow-up was performed at 3, 12, and 24 months. Predetermined composite primary safety (freedom from perioperative serious adverse events [AEs] and from clinically significant perforation, VCF embolization, caval thrombotic occlusion, and/or new deep vein thrombosis [DVT] within 12-months) and effectiveness (composite comprising procedural and technical success and freedom from new symptomatic pulmonary embolism [PE] confirmed by imaging at 12-months in situ or 1 month postretrieval) end points were assessed.

RESULTS

VCFs were implanted in 1421 patients. Of these, 1019 (71.7%) had current DVT and/or PE. Anticoagulation therapy was contraindicated or had failed in 1159 (81.6%). One hundred twenty-six (8.9%) VCFs were prophylactic. Mean and median follow-up for the entire population and for those whose VCFs were not removed was 243.5 ± 243.3 days and 138 days and 332.6 ± 290 days and 235 days, respectively. VCFs were removed from 632 (44.5%) patients at a mean of 101.5 ± 72.2 days and median 86.3 days following implantation. The primary safety end point and primary effectiveness end point were both achieved. Procedural AEs were uncommon and usually minor, but one patient died during attempted VCF removal. Excluding strut perforation greater than 5 mm, which was demonstrated on 31 of 201 (15.4%) patients' computed tomography scans available to the core laboratory, and of which only 3 (0.2%) were deemed clinically significant by the site investigators, VCF-related AEs were rare (7 of 1421, 0.5%). Postfilter, venous thromboembolic events (none fatal) occurred in 93 patients (6.5%), including DVT (80 events in 74 patients [5.2%]), PE (23 events in 23 patients [1.6%]), and/or caval thrombotic occlusions (15 events in 15 patients [1.1%]). No PE occurred in patients following prophylactic placement.

CONCLUSIONS

Implantation of VCFs in patients with venous thromboembolism was associated with few AEs and with a low incidence of clinically significant PEs.

Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE): Outcomes at 12 months

OBJECTIVE

To determine the safety and effectiveness of vena cava filters (VCFs).

METHODS

A total of 1429 participants (62.7 ± 14.7 years old; 762 [53.3% male]) consented to enroll in this prospective, nonrandomized study at 54 sites in the United States between October 10, 2015, and March 31, 2019. They were evaluated at baseline and at 3, 6, 12, 18, and 24 months following VCF implantation. Participants whose VCFs were removed were followed for 1 month after retrieval. Follow-up was performed at 3, 12, and 24 months. Predetermined composite primary safety (freedom from perioperative serious adverse events [AEs] and from clinically significant perforation, VCF embolization, caval thrombotic occlusion, and/or new deep vein thrombosis [DVT] within 12-months) and effectiveness (composite comprising procedural and technical success and freedom from new symptomatic pulmonary embolism [PE] confirmed by imaging at 12-months in situ or 1 month postretrieval) end points were assessed.

RESULTS

VCFs were implanted in 1421 patients. Of these, 1019 (71.7%) had current DVT and/or PE. Anticoagulation therapy was contraindicated or had failed in 1159 (81.6%). One hundred twenty-six (8.9%) VCFs were prophylactic. Mean and median follow-up for the entire population and for those whose VCFs were not removed was 243.5 ± 243.3 days and 138 days and 332.6 ± 290 days and 235 days, respectively. VCFs were removed from 632 (44.5%) patients at a mean of 101.5 ± 72.2 days and median 86.3 days following implantation. The primary safety end point and primary effectiveness end point were both achieved. Procedural AEs were uncommon and usually minor, but one patient died during attempted VCF removal. Excluding strut perforation greater than 5 mm, which was demonstrated on 31 of 201 (15.4%) patients' computed tomography scans available to the core laboratory, and of which only 3 (0.2%) were deemed clinically significant by the site investigators, VCF-related AEs were rare (7 of 1421, 0.5%). Postfilter, venous thromboembolic events (none fatal) occurred in 93 patients (6.5%), including DVT (80 events in 74 patients [5.2%]), PE (23 events in 23 patients [1.6%]), and/or caval thrombotic occlusions (15 events in 15 patients [1.1%]). No PE occurred in patients following prophylactic placement.

CONCLUSIONS

Implantation of VCFs in patients with venous thromboembolism was associated with few AEs and with a low incidence of clinically significant PEs.

Economic Evaluation of Direct Oral Anticoagulants Compared to Warfarin for Venous Thromboembolism in Thailand: A Cost-Utility Analysis

BACKGROUND

Direct oral anticoagulants (DOACs) have been used for venous thromboembolism (VTE) in Thailand. However, they have not been listed in the National List of Essential Medicines (NLEM). A cost-effectiveness analysis is needed to aid policymakers in deciding whether DOACs should be listed in the NLEM. This study aimed to assess the cost-effectiveness of DOACs for patients with VTE in Thailand.

METHODS

A cohort-based state transition model was constructed from a societal perspective with a lifetime horizon. All available DOACs, including apixaban, rivaroxaban, edoxaban, and dabigatran, were compared with warfarin. A 6-month cycle length was used to capture all costs and health outcomes. The model consisted of nine health states, including VTE on treatment, VTE off treatment, recurrent VTE, clinically relevant non-major bleeding, gastrointestinal bleeding, intracranial bleeding, post-intracranial bleeding, chronic thromboembolic pulmonary hypertension, and death. All inputs were based on a comprehensive literature review. The model outcomes included total cost and quality-adjusted life-years (QALYs) with a 3% annual discount rate. A fully incremental cost-effectiveness analysis and the incremental cost-effectiveness ratio (ICER) per QALY gained were calculated at a willingness-to-pay (WTP) of THB 160,000/QALY ($5003). The robustness of the findings was assessed using deterministic and probabilistic sensitivity analyses.

RESULTS

All DOACs were associated with a decreased risk of VTE recurrence and intracranial hemorrhage. In the base-case analysis, apixaban could increase 0.16 QALYs compared with warfarin. An ICER for apixaban was 269,809 Thai baht (THB)/QALY ($8437/QALY). Rivaroxaban had a better QALY than warfarin at 0.09 QALYs with an ICER of 757,363 THB/QALY ($23,682/QALY). Edoxaban and dabigatran could also increase by 0.10 QALYs with an ICER of 709,945 THB ($22,200) and 707,145 THB ($22,122)/QALY, respectively. Our probabilistic sensitivity analyses indicated that warfarin had a 99.8% possibility of being cost-effective, while apixaban had a 0.2% possibility of being cost-effective at the current WTP. Other DOACs had no possibility of being cost-effective.

CONCLUSIONS

All DOACs were not cost-effective for VTE treatment at the current WTP in Thailand. Apixaban is likely to be the best option among DOACs.

Residual pulmonary vascular obstruction and recurrence after acute pulmonary embolism: a systematic review and meta-analysis of individual participant data

We aimed to assess the relationship between residual pulmonary vascular obstruction (RPVO) on planar lung scan after completion of at least 3 months of anticoagulant therapy for acute pulmonary embolism (PE) and the risk of recurrent venous thromboembolism (VTE) or death due to PE one year after treatment discontinuation. The systematic review was registered with the International Prospective Registry of Systematic Reviews (PROSPERO: CRD42017081080). The primary outcome measure was to generate a pooled estimate of the rate of recurrent VTE at one year in patient with RPVO diagnosed on planar lung scan after discontinuation of at least 3 months of anticoagulant treatment for an acute PE. Individual data were obtained for 809 patients. RPVO (ie, obstruction >0%) was found in 407 patients (50.3%) after a median of 6.6 months of anticoagulant therapy for a first acute PE. Recurrent VTE or death due to PE occurred in 114 patients (14.1%), for an annual risk of 6.4% (95% confidence interval, 4.7%-8.6%). Out of the 114 recurrent events, 63 occurred within one year after discontinuation of anticoagulant therapy corresponding to a risk of 8.1% (6.4%-9.8%) at 1 year. The risk of recurrent VTE at one year was 5.8% (4.4-7.2) in participants with RPVO <5%, vs 11.7% (9.5-13.8) in participants with RPVO ≥5%. RPVO is a significant predictor of the risk of recurrent venous thromboembolism. However, the risk of recurrent events remains too high in patients without residual perfusion defect for it to be used as a stand-alone test to decide on anticoagulation discontinuation.

Role of factor VIII, IX, and XI in venous thrombosis recurrence risk in adults and children: A systematic review

Background

Predicting recurrent venous thromboembolic events (VTEs) is challenging in clinical practice for both adults and children, but it is relevant for clinical management. Identifying laboratory risk factors for VTE recurrence may aid in clinical decision-making.

Objective

The goal of this systematic review is to investigate the predictive role of FVIII, IX, or XI in recurrent VTE in adult and pediatric patients with a first VTE.

Methods

A systematic review of the published literature was conducted in databases MEDLINE In-Process, Other Nonindexed Citations, MEDLINE Epub Ahead of Print, EMBASE Classic + EMBASE (OvidSP), and Cochrane (Wiley). We included observational and interventional studies that comprised adults or children with a first VTE, FVIII, FIX, and/or FXI and objectively confirmed VTE recurrence. The quality in prognosis studies tool was used to assess the risk of bias.

Results

We identified 2177 unique studies, of which 19 were included (18 for adults and 1 for children). The risk of bias was overall low to moderate. The studies were heterogenous with regards to population (provoked/unprovoked primary VTE), exposure (type of assay and cut-off values), and statistical analysis results (measures of association and modeling strategy). In adults, contradictory evidence was found for FVIII and FXI as outcome predictors, while no research could establish if FIX predicts VTE recurrence. Data in pediatrics were limited. Given the extensive heterogeneity of the literature, a meta-analysis was not performed.

Conclusions

Overall, there is contradictory evidence that FVIII, FIX, or FXI predict recurrent VTE in adults and children. Addressing heterogeneity is a relevant aspect to consider in future studies investigating prognostic factors for VTE recurrence.

Recurrences and bleeding during extended treatment of patients with venous thromboembolism: results of the international, prospective, observational WHITE study

BACKGROUND

Little data are available on real-life long-term treatments after a venous thromboembolism (VTE), and on recurrent VTE or bleeds events during treatments.

METHODS

We investigated the complications occurring during follow-up (FU) in VTE patients who had received the treatment decisions given by the clinical centers, active in 7 countries (China, Czechia, Poland, Portugal, Russia, Slovakia, Tunisia), which participated in the international, prospective, observational WHITE study.

RESULTS

FU information was collected in 1004 patients, recruited by 62 clinical centers (17 centers did not participate in FU collection). Extended treatments were proposed to 811 patients: direct oral anticoagulants (DOACs) (475), sulodexide (202), antiplatelet agents (73), vitamin K antagonists (VKAs) (45), low molecular weight heparin (LMWH) (16). All specific treatments were stopped in the remaining 193 patients. Patients who during FU used treatments different than those prescribed by the local investigators (263) or for other causes (26) were excluded from analysis. 50 primary events occurred throughout 1044 years FU in 715 patients, 4.8 incidence (×100 patient-years) [3.8 for recurrences, and 0.96 for bleeding (major or clinically relevant)]. Primary event incidence differed according to treatments (LMWH=33.3, antiplatelets =7.6, VKAs = 6.1, DOACs = 4.7, sulodexide = 4.2, all treatment stopped = 2.5), and differed across the involved countries.

CONCLUSIONS

DOACs were the most used drugs for extended treatments. Overall, the rate of primary events during FU was low. The investigators identified patients at low risk of recurrence and high bleeding risk. Sulodexide use for secondary prevention deserves further studies.

Protocol for a modelling study to assess the clinical and cost-effectiveness of indefinite anticoagulant therapy for first unprovoked venous thromboembolism

INTRODUCTION

Deciding whether to stop or extend anticoagulant therapy indefinitely after completing at least 3 months of initial treatment for a first unprovoked venous thromboembolism (VTE) remains a challenge for clinicians, patients and policy makers. Guidelines suggest an indefinite duration of anticoagulant therapy in these patients, yet its benefits, harms and costs have not been formally assessed. The aim of this proposed modelling study is to assess the differences in clinical benefits, harms and costs of stopping versus continuing anticoagulant therapy indefinitely for a first unprovoked VTE.

METHODS AND ANALYSIS

We will develop a probabilistic Markov model, adopting a 1-month cycle length and a lifetime horizon, to estimate life-years, quality-adjusted life-years, costs and the incremental cost-effectiveness ratios for a simulated population of patients with a first unprovoked VTE who will receive indefinite duration of anticoagulant therapy versus a population who will not receive extended treatment after completing 3 months of initial anticoagulant therapy. The economic evaluation will adopt a third-party payer perspective relating to a Canadian publicly funded healthcare system. Estimates for the probability of relevant clinical events will be informed by systematic reviews and meta-analyses, while costs and utility values will be obtained from published Canadian sources. Stratified analyses based on sex, age and site of initial VTE will also be performed to identify subgroups of patients with a first unprovoked VTE in whom continuing anticoagulant therapy indefinitely might prove to be clinically beneficial and cost-effective over stopping treatment. We will also conduct sensitivity and scenario analyses to assess robustness of study findings to changes in individual or groups of key parameters.

ETHICS AND DISSEMINATION

Ethical approval is not applicable for this study. The results will be disseminated through presentations at relevant conferences and in a manuscript that will be submitted to a peer-reviewed journal.