Prescribing patterns and outcomes of venous thromboembolism prophylaxis in hospitalized medical and cancer patients: Observations from the Ottawa Hospital.

Guidelines suggest broad use of pharmacologic prophylaxis to prevent venous thromboembolism (VTE) in hospitalized medical patients, however little 'real-world' data exists to support this. Our goal was to describe the use of thromboprophylaxis among general medical and cancer patients admitted to hospital, compare VTE and bleeding outcomes according to use of thromboprophylaxis, and to determine what variables influence prescribing patterns and outcomes. Patients admitted to the general medical and oncology services at The Ottawa Hospital between 2010 and 2015 were retrospectively reviewed and classified according to whether they received initial, delayed, or no pharmacologic thromboprophylaxis during their first hospitalization. Patients with an alternate indication for anticoagulation or those admitted with a bleeding event were excluded from analysis. The primary efficacy outcome was any symptomatic VTE during index hospitalization or within 90 days of discharge, and the primary safety outcome was clinically relevant bleeding during the index hospitalization. 17,262 patients were included in our final analysis. General medical patients selected to receive no, initial, or delayed thromboprophylaxis had 0.4%, 0.7%, and 2.4% rates of VTE; and 0.2%, 0.7%, and 1.5% rates of clinically relevant bleeding complications, respectively. Cancer patients had significantly higher rates of VTE: 3.3%, 3.9%, and 5.0%; and 0.9%, 0.7%, and 3.0% rates of clinically relevant bleeding among those selected to receive no, initial, or delayed thromboprophylaxis, respectively. Overall, our study suggests that broad use of pharmacologic thromboprophylaxis may be unnecessary in select low-risk general medical patients and may be less effective in cancer patients in whom new studies are indicated.

Ruling out pulmonary embolism across different subgroups of patients and healthcare settings: protocol for a systematic review and individual patient data meta-analysis (IPDMA).

BACKGROUND: Diagnosing pulmonary embolism in suspected patients is notoriously difficult as signs and symptoms are non-specific. Different diagnostic strategies have been developed, usually combining clinical probability assessment with D-dimer testing. However, their predictive performance differs across different healthcare settings, patient subgroups, and clinical presentation, which are currently not accounted for in the available diagnostic approaches. METHODS: This is a protocol for a large diagnostic individual patient data meta-analysis (IPDMA) of currently available diagnostic studies in the field of pulmonary embolism. We searched MEDLINE (search date January 1, 1995, till August 25, 2016) to retrieve all primary diagnostic studies that had evaluated diagnostic strategies for pulmonary embolism. Two authors independently screened titles, abstracts, and subsequently full-text articles for eligibility from 3145 individual studies. A total of 40 studies were deemed eligible for inclusion into our IPDMA set, and principal investigators from these studies were invited to participate in a meeting at the 2017 conference from the International Society on Thrombosis and Haemostasis. All authors agreed on data sharing and participation into this project. The process of data collection of available datasets as well as potential identification of additional new datasets based upon personal contacts and an updated search will be finalized early 2018. The aim is to evaluate diagnostic strategies across three research domains: (i) the optimal diagnostic approach for different healthcare settings, (ii) influence of comorbidity on the predictive performance of each diagnostic strategy, and (iii) optimize and tailor the efficiency and safety of ruling out PE across a broad spectrum of patients with a new, patient-tailored clinical decision model that combines clinical items with quantitative D-dimer testing. DISCUSSION: This pre-planned individual patient data meta-analysis aims to contribute in resolving remaining diagnostic challenges of time-efficient diagnosis of pulmonary embolism by tailoring available diagnostic strategies for different healthcare settings and comorbidity. SYSTEMATIC REVIEW REGISTRATION: Prospero trial registration: ID 89366.

PO-41 - Rivaroxaban is effective therapy for high risk cancer patients with venous thromboembolic disease.

INTRODUCTION: The standard of care for cancer associated venous thromboembolism (VTE) is generally accepted to be at least six months of therapeutic doses of low molecular weight heparin (LMWH). After six months it is recommended that therapy be continued but no studies have evaluated treatment in this period. Rivaroxaban is a potentially effective therapy given cancer patients were enrolled in the EINSTEIN trial with acceptable safety and efficacy but details on these patients is lacking. AIM: To determine the safety and efficacy of rivaroxaban for the treatment of cancer associated VTE. MATERIALS AND METHODS: We performed a retrospective chart review of all cancer patients seen in our thrombosis program and enrolled patients seen between January 2012 and April 2015. Complete patient identification was accomplished through our hospital data warehouse. We recorded all relevant demographics. Initial diagnoses were all confirmed with objective imaging tests according to standard definitions. Major bleeds, using the ISTH definition, and recurrent VTE events were adjudicated by at least two observers. RESULTS: 237 active cancer patients received treatment with rivaroxaban; 65 (27%) were initiated on rivaroxaban, 30 (12.6%) started between day 8 and 2 months, 75 (32%) started therapy between day 8 and the 6 month point and 97 (41%) started therapy at 6 months or beyond. 26 patients were put on rivaroxaban after failing LMWH. The average duration of rivaroxaban therapy was 297 days; The average age of patients was 61 (SD±13); 41% of patients were male, 59% were female. 47% of patients had metastatic cancer. Of the 65 patients who were initiated on rivaroxaban 24 (37%) had metastatic cancer. Overall 3.8% of patients recurred while on rivaroxaban therapy with no deaths due to PE, and 3 patients had major hemorrhage with 2 deaths. Of the 9 patients who recurred on rivaroxaban, 3 of them were initiated on rivaroxaban, 3 of them were started 8 days-6 months, and 3 of them started after 6 months. The median number of days from initiation of rivaroxaban to VTE recurrence was 113. 26 patients received rivaroxaban after a recurrent event on therapeutic doses of LMWH, none recurred. Of the 65 patients who were initiated on rivaroxaban 3 recurred and of the 97 patients who were started on rivaroxaban after 6 months three recurred 0.580). All patients were treated on an outpatient basis. CONCLUSIONS: Recurrence and major bleeding events on rivaroxaban were low despite the fact almost half the patients had metastatic disease. Rivaroxaban can be considered acceptable therapy for the treatment of cancer associated with venous thromboembolic disease.

Rivaroxaban for treatment of suspected or confirmed heparin-induced thrombocytopenia study.

UNLABELLED: Essentials Heparin-induced thrombocytopenia (HIT) is a thrombogenic condition that is difficult to treat. We evaluated rivaroxaban as a treatment option in patients with suspected or confirmed HIT. One patient had recurrent thrombosis and 9/10 patients with thrombocytopenia had platelet recovery. Rivaroxaban may be an effective and safe treatment option for HIT. SUMMARY: Background Rivaroxaban is a direct oral anti-Xa inhibitor that has the potential to greatly simplify treatment of heparin-induced thrombocytopenia (HIT). Objectives To evaluate the efficacy and safety of rivaroxaban in this patient population, we conducted a multicenter, single-arm, prospective cohort study of patients with suspected or confirmed HIT. Patients/Methods Twenty-two consecutive adults with suspected or confirmed HIT received rivaroxaban 15 mg bid until a local HIT assay result was available. Participants with a positive local assay result continued rivaroxaban 15 mg bid until platelet recovery (or until day 21 if they had acute thrombosis at study entry), then stepped down to rivaroxaban 20 mg daily until day 30. Results and Conclusions The primary outcome measure, incidence of new symptomatic, objectively-confirmed venous and arterial thromboembolism at 30 days, occurred in one HIT-positive participant (4.5%; 95% confidence interval [CI], 0-23.5%) and one HIT-positive participant required limb amputation despite platelet recovery. Platelet recovery was achieved in nine out of 10 HIT-positive patients with thrombocytopenia. Rivaroxaban appears to be effective for treating patients with confirmed HIT, although the small number of patients enrolled limits precision.

Inflammation markers and their trajectories after deep vein thrombosis in relation to risk of post-thrombotic syndrome.

BACKGROUND: Post-thrombotic syndrome (PTS) is a frequent chronic complication of deep vein thrombosis (DVT). OBJECTIVE: In the BioSOX study, we investigated whether inflammation markers predict the risk of PTS after DVT. METHODS: We measured C-reactive protein (CRP), ICAM-1, interleukin (IL)-6, and IL-10, at baseline, and 1 month and 6 months after a first proximal DVT, among 803 participants in the SOX trial. Participants were prospectively followed for 24 months for development of PTS. RESULTS: Median CRP levels at 1 month, ICAM-1 levels at baseline, 1 month and 6 months, IL-6 levels at 1 month and 6 months and IL-10 levels at 6 months were higher in patients who developed PTS than in those who did not. Multivariable regression with the median as a cutoff showed risk ratios (RRs) for PTS of 1.23 (95% confidence interval [CI] 1.05-1.45) and 1.25 (95% CI 1.05-1.48) for ICAM-1 at 1 month and 6 months, respectively, and 1.27 (95% CI 1.07-1.51) for IL-10 at 6 months. Quartile-based analysis demonstrated a dose-response association between ICAM-1 and PTS. ICAM-1 and IL-10 were also associated with PTS severity. Analysis of biomarker trajectories after DVT demonstrated an association between the highest-trajectory group of ICAM-1 and PTS. CONCLUSIONS: In this prospective study, ICAM-1 over time was most consistently associated with the risk of PTS. Further study is required to confirm these findings and assess their potential clinical relevance.

Graduated compression stockings to treat acute leg pain associated with proximal DVT. A randomised controlled trial.

Acute deep venous thrombosis (DVT) causes leg pain. Elastic compression stockings (ECS) have potential to relieve DVT-related leg pain by diminishing the diameter of distended veins and increasing venous blood flow. It was our objective to determine whether ECS reduce leg pain in patients with acute DVT. We performed a secondary analysis of the SOX Trial, a multicentre randomised placebo controlled trial of active ECS versus placebo ECS to prevent the post-thrombotic syndrome.The study was performed in 24 hospital centres in Canada and the U.S. and included 803 patients with a first episode of acute proximal DVT. Patients were randomised to receive active ECS (knee length, 30-40 mm Hg graduated pressure) or placebo ECS (manufactured to look identical to active ECS, but lacking therapeutic compression). Study outcome was leg pain severity assessed on an 11-point numerical pain rating scale (0, no pain; 10, worst possible pain) at baseline, 14, 30 and 60 days after randomisation. Mean age was 55 years and 60% were male. In active ECS patients (n=409), mean (SD) pain severity at baseline and at 60 days were 5.18 (3.29) and 1.39 (2.19), respectively, and in placebo ECS patients (n=394) were 5.38 (3.29) and 1.13 (1.86), respectively. There were no significant differences in pain scores between groups at any assessment point, and no evidence for subgroup interaction by age, sex or anatomical extent of DVT. Results were similar in an analysis restricted to patients who reported wearing stockings every day. In conclusion, ECS do not reduce leg pain in patients with acute proximal DVT.

Exclusion of deep vein thrombosis using the Wells rule in clinically important subgroups: individual patient data meta-analysis.

OBJECTIVE: To assess the accuracy of the Wells rule for excluding deep vein thrombosis and whether this accuracy applies to different subgroups of patients. DESIGN: Meta-analysis of individual patient data. DATA SOURCES: Authors of 13 studies (n = 10,002) provided their datasets, and these individual patient data were merged into one dataset. ELIGIBILITY CRITERIA: Studies were eligible if they enrolled consecutive outpatients with suspected deep vein thrombosis, scored all variables of the Wells rule, and performed an appropriate reference standard. MAIN OUTCOME MEASURES: Multilevel logistic regression models, including an interaction term for each subgroup, were used to estimate differences in predicted probabilities of deep vein thrombosis by the Wells rule. In addition, D-dimer testing was added to assess differences in the ability to exclude deep vein thrombosis using an unlikely score on the Wells rule combined with a negative D-dimer test result. RESULTS: Overall, increasing scores on the Wells rule were associated with an increasing probability of having deep vein thrombosis. Estimated probabilities were almost twofold higher in patients with cancer, in patients with suspected recurrent events, and (to a lesser extent) in males. An unlikely score on the Wells rule (≤ 1) combined with a negative D-dimer test result was associated with an extremely low probability of deep vein thrombosis (1.2%, 95% confidence interval 0.7% to 1.8%). This combination occurred in 29% (95% confidence interval 20% to 40%) of patients. These findings were consistent in subgroups defined by type of D-dimer assay (quantitative or qualitative), sex, and care setting (primary or hospital care). For patients with cancer, the combination of an unlikely score on the Wells rule and a negative D-dimer test result occurred in only 9% of patients and was associated with a 2.2% probability of deep vein thrombosis being present. In patients with suspected recurrent events, only the modified Wells rule (adding one point for the previous event) is safe. CONCLUSION: Combined with a negative D-dimer test result (both quantitative and qualitative), deep vein thrombosis can be excluded in patients with an unlikely score on the Wells rule. This finding is true for both sexes, as well as for patients presenting in primary and hospital care. In patients with cancer, the combination is neither safe nor efficient. For patients with suspected recurrent disease, one extra point should be added to the rule to enable a safe exclusion.

Is thrombophilia associated with placenta-mediated pregnancy complications? A prospective cohort study.

BACKGROUND: Case control studies suggest that genetic thrombophilias increase the risk of placenta-mediated pregnancy complications (pregnancy loss, small for gestational age (SGA), preeclampsia and/or placental abruption). Cohort studies have not supported this association but were underpowered to detect small effects. OBJECTIVE: To determine if factor V Leiden (FVL) or the prothrombin gene mutation (PGM) were associated with placenta-mediated pregnancy complications. PATIENTS/METHODS: A prospective cohort of unselected, consenting pregnant women at three Canadian tertiary care hospitals had blood drawn in the early second trimester and were genotyped for FVL and PGM after delivery. The main outcome measure was a composite of pregnancy loss, SGA < 10th percentile, preeclampsia or placental abruption. RESULTS: Complete primary outcome and genetic data were available for 7343 women. Most were Caucasian (77.7%, n = 5707), mean age was 30.4 (± 5.1) years, and half were nulliparous. There were 507 (6.9%) women with FVL and/or PGM; 11.64% had a placenta-mediated pregnancy complication. Of the remaining 6836 women, 11.23% experienced a complication. FVL and/or PGM was associated with a relative risk of 1.04 (95% CI, 0.81-1.33) for the composite outcome, with similar results after adjustment for important covariates. CONCLUSIONS: Carriers of FVL or PGM are not at significantly increased risk of these pregnancy complications.

Predictors of post-thrombotic syndrome in a population with a first deep vein thrombosis and no primary venous insufficiency.

BACKGROUND: Post-thrombotic syndrome (PTS) is the most frequent complication of deep vein thrombosis (DVT). Its diagnosis is based on clinical characteristics. However, symptoms and signs of PTS are non-specific, and could result from concomitant primary venous insufficiency (PVI) rather than DVT. This could bias evaluation of PTS. METHODS: Using data from the REVERSE multicenter study, we assessed risk factors for PTS in patients with a first unprovoked unilateral proximal DVT 5-7 months earlier who were free of clinically significant PVI (defined as absence of moderate or severe venous ectasia in the contralateral leg). RESULTS: Among the 328 patients considered, the prevalence of PTS was 27.1%. Obesity (odds ratio [OR] 2.6 [95% confidence interval (CI) 1.5-4.7]), mild contralateral venous ectasia (OR 2.2 [95% CI 1.1-4.3]), poor International Normalized Ratio (INR) control (OR per additional 1% of time with INR < 2 during anticoagulant treatment of 1.018 [95% CI 1.003-1.034]) and the presence of residual venous obstruction on ultrasound (OR 2.1 [95% CI 1.1-3.7]) significantly increased the risk for PTS in multivariable analyses. When we restricted our analysis to patients without any signs, even mild, of contralateral venous insufficiency (n = 244), the prevalence of PTS decreased slightly to 24.6%. Only obesity remained an independent predictor of PTS (OR 2.6 [95% CI 1.3-5.0]). Poor INR control and residual venous obstruction also increased the risk, but the results were no longer statistically significant (OR 1.017 [95% CI 0.999-1.035] and OR 1.7 [95% CI 0.9-3.3], respectively). CONCLUSIONS: After a first unprovoked proximal DVT, obese patients and patients with even mild PVI constitute a group at increased risk of developing PTS for whom particular attention should be paid with respect to PTS prevention. Careful monitoring of anticoagulant treatment may prevent PTS.

Clot resolution after 3 weeks of anticoagulant treatment for pulmonary embolism: comparison of computed tomography and perfusion scintigraphy.

INTRODUCTION: Little is known about the natural history of clot resolution in the initial weeks of anticoagulant therapy in patients with acute pulmonary embolism (PE). Clot resolution of acute PE was assessed with either computed tomography pulmonary angiography scan (CT-scan) or perfusion scintigraphy scan (Q-scan) after 3 weeks of treatment. METHODS: This was a predefined safety analysis of the Einstein PE study, including PE patients, randomized to either enoxaparin with vitamin K antagonist (VKA) or rivaroxaban. A similar scan as at baseline was repeated after 3 weeks. The percentage of vascular obstruction (PVO) was calculated on the basis of a weighted semiquantitative estimation of obstruction. Clot resolution was assessed blindly by calculating the relative change after 3 weeks. RESULTS: PE was diagnosed in 264 patients with CT-scan and in 83 with Q-scan. Baseline characteristics were similar. At baseline, the mean PVO assessed with CT-scan (PVO-CT) and the mean PVO assessed with Q-scan (PVO-Q) were both 21% (standard deviation [SD] 13%) (P = 0.9). The mean relative decrease in PVO was 71% (SD 33%) for PVO-CT, and 62% (SD 36%) for PVO-Q (P = 0.02); complete resolution was observed in 44% (116/264; 95% confidence interval [CI] 38-50%) and 31% (26/83; 95% CI 22-42%) with CT-scan and Q-scan, respectively (P = 0.04). No difference in clot resolution between enoxaparin/VKA and rivaroxaban was found. CONCLUSION: In patients with acute PE, only 3 weeks of anticoagulant treatment leads to complete clot resolution in a considerable proportion of patients, and normalization is more often observed with CT-scan than with Q-scan.

Risk of post-thrombotic syndrome after subtherapeutic warfarin anticoagulation for a first unprovoked deep vein thrombosis: results from the REVERSE study.

BACKGROUND: Risk factors for post-thrombotic syndrome (PTS) remain poorly understood. OBJECTIVES: In this multinational multicenter study, we evaluated whether subtherapeutic warfarin anticoagulation was associated with the development of PTS. METHODS: Patients with a first unprovoked deep venous thrombosis (DVT) received standard anticoagulation for 5-7 months and were then assessed for PTS. The time in the therapeutic range was calculated from the international normalized ratio (INR) data. An INR below 2, more than 20% of the time, was considered as subtherapeutic anticoagulation. RESULTS: Of the 349 patients enrolled, 97 (28%) developed PTS. The overall frequency of PTS in patients with subtherapeutic anticoagulation was 33.5%, compared with 21.6% in those with an INR below two for ≤ 20% of the time (P = 0.01). During the first 3 months of therapy, the odds ratio (OR) for developing PTS if a patient had subtherapeutic anticoagulation was 1.78 (95% confidence interval [CI] 1.10-2.87). After adjusting for confounding variables, the OR was 1.84 (95% CI 1.13-3.01). Corresponding ORs for the full period of anticoagulation were 1.83 (95% CI 1.14-3.00) [crude] and 1.88 (95% CI 1.15-3.07) [adjusted]. CONCLUSION: Subtherapeutic warfarin anticoagulation after a first unprovoked DVT was significantly associated with the development of PTS.

Comparison of the Villalta post-thrombotic syndrome score in the ipsilateral vs. contralateral leg after a first unprovoked deep vein thrombosis.

BACKGROUND: Post-thrombotic syndrome (PTS) is the most frequent complication of a deep vein thrombosis (DVT). International guidelines recommend assessing PTS with the Villalta scale, a clinical measure that incorporates venous symptoms and signs in the leg ipsilateral to a DVT. However, these signs and symptoms are not specific for PTS and their prevalence and relevance in the contralateral leg have not previously been studied. METHODS: Using data from the REVERSE prospective multicentre cohort study, we compared the Villalta total score and prevalence of venous signs and symptoms in the ipsilateral vs. contralateral leg in patients with a first, unilateral DVT 5 to 7 months previously. RESULTS: Among the 367 patients analyzed, the mean Villalta score was higher in the ipsilateral than in the contralateral leg (mean ± standard deviation [SD] 3.7 [3.4] vs. 1.9 [2.5], respectively; P<0.0001). Villalta scores in the ipsilateral and contralateral legs were strongly correlated (r=0.68; P<0.0001). Ipsilateral PTS (defined by a Villalta total score >4) was present in 31.6% (n=116) of patients. Among these, 39.7% (n=46) of patients had a Villalta score >4 in the contralateral leg, and the distribution of Villalta symptoms and signs components was similar between the legs. CONCLUSIONS: Villalta scores in the ipsilateral and contralateral legs are strongly correlated. Almost half of cases considered to be PTS might reflect pre-existing symptomatic chronic venous disease. Alternatively, patients with pre-existing chronic venous disease might be more prone to developing PTS after a DVT. Performing a bilateral assessment of Villalta scores at the acute phase of DVT could be of clinical interest from a diagnostic, prognostic and therapeutic point of view.

Baseline imaging after therapy for unprovoked venous thromboembolism: a randomized controlled comparison of baseline imaging for diagnosis of suspected recurrence.

BACKGROUND: After a first unprovoked venous thromboembolism (VTE), many patients have residual pulmonary and/or lower limb vascular obstruction following completion of short-term anticoagulation. Residual vascular obstruction may complicate the diagnosis of recurrent VTE. Whether baseline imaging, conducted after completion of anticoagulation, helps in interpreting diagnostic testing in patients who subsequently have suspected recurrent VTE is unknown. STUDY DESIGN: The REVERSE study is a cohort study whose primary aim was to derive a clinical decision rule to guide the duration of anticoagulation after a first unprovoked VTE. All patients underwent baseline imaging after completing 5-7 months of anticoagulant therapy. We performed a post hoc randomized controlled comparison among 121 patients investigated for a suspected recurrent VTE during follow-up: the decision on recurrent VTE with or without baseline imaging was made available to two independent adjudicators. RESULTS: The proportion of patients not classifiable for recurrent VTE was statistically significantly higher in the group with no baseline imaging than in the group with baseline imaging: one in five as compared with one in 25. The interobserver agreement between the two adjudicators was better in the group with baseline imaging than in the group with no baseline imaging: κ-values were 0.78 and 0.54, respectively. CONCLUSIONS: In patients with a first unprovoked VTE, baseline imaging at completion of anticoagulant therapy helps in interpreting diagnostic tests performed in cases of suspected recurrent VTE.

Residual vein obstruction to predict the risk of recurrent venous thromboembolism in patients with deep vein thrombosis: a systematic review and meta-analysis.

BACKGROUND: Residual vein obstruction (RVO) detected on compression ultrasonography of the leg after a few months of anticoagulation therapy might be able to identify patients with deep vein thrombosis (DVT) at high risk of having a recurrent venous thromboembolism (VTE). AIM: To determine whether RVO is associated with an increased risk of recurrent events in patients with DVT. PATIENTS AND METHODS: A systematic literature search strategy was conducted using MEDLINE, EMBASE, and the Cochrane Register of Controlled Trials. We selected 14 articles (nine prospective cohort studies and five randomized controlled trials) that included patients with DVT who had an assessment for RVO with the use of compression ultrasonography. Two reviewers independently extracted data onto standardized forms. RESULTS: Overall, the presence of RVO was not associated with an increased risk of recurrent VTE (odds ratio [OR] 1.24, 95% confidence interval [CI] 0.9-1.7) in patients with unprovoked DVT who stopped oral anticoagulation therapy at the time of RVO assessment. However, RVO was significantly associated with recurrent VTE in patients with any (unprovoked or provoked) DVT (OR 1.5, 95% CI 1.1-2.0). CONCLUSIONS: RVO was associated with a modestly increased risk of recurrent VTE in patients with DVT (unprovoked and provoked). However, RVO did not seem to be a predictor of recurrent VTE in patients with unprovoked DVT following anticoagulation discontinuation. Further prospective studies are needed to assess the role of RVO in patients with unprovoked DVT.

Residual vein obstruction as a predictor for recurrent thromboembolic events after a first unprovoked episode: data from the REVERSE cohort study.

OBJECTIVES: There is growing interest in using residual vein obstruction (RVO) to guide the duration of oral anticoagulant therapy (OAT) for unprovoked deep vein thrombosis (DVT). We sought to determine if RVO as determined by compression ultrasonography (CUS) after completion of 5-7 months of anticoagulation for unprovoked DVT is associated with an increased risk of recurrent venous thromboembolism (VTE). MATERIALS AND METHODS: This was a multicentre multinational prospective cohort study undertaken in tertiary care centers. Patients with a first 'unprovoked' major VTE were enrolled over a 4-year period and completed a mean 18-month follow-up in September 2006. All 452 patients with DVT had baseline CUS at inclusion to assess any RVO before stopping OAT at 5-7 months. During follow-up off OAT, all episodes of suspected recurrent VTE were independently adjudicated with reference to baseline imaging. RESULTS: Forty-five out of 231 patients with abnormal CUS (19.5%) had recurrent VTE during follow-up, as compared with 32 out of 220 patients with normal CUS (14.6%), and one patient had inadequate CUS. There was no significant association between an abnormal CUS at inclusion and the risk of recurrent VTE: hazard ratio 1.4 (95% confidence interval, 0.9-2.1), P=0.19. None of the different degrees of clot resolution on baseline CUS was statistically significantly associated with the risk of recurrent VTE. CONCLUSION: In our study, the presence of RVO at the time of OAT withdrawal was not associated with a statistically significant higher risk of recurrent VTE. RVO assessment may not be useful to guide duration of anticoagulation.