A.C. Bouman

Markers of coagulation, fibrinolysis and inflammation in relation to post-thrombotic syndrome.

Summary.  Background:  Post‐thrombotic syndrome (PTS) occurs in 20–50% of patients after a deep venous thrombosis (DVT). It is difficult to accurately predict which patients will develop PTS. Biomarkers could be a valuable tool for PTS risk assessment.

Biomarkers for post thrombotic syndrome: A case-control study

INTRODUCTION There is limited knowledge on the etiology of post thrombotic syndrome (PTS), although several mechanisms have been proposed. The objectives are to explore the role of different pathogenic mechanisms for PTS, through measurement of an elaborate panel of biomarkers in patients with and without PTS. MATERIALS AND METHODS Patients with a history of deep vein thrombosis (DVT) with PTS (cases) and without PTS after minimal 2years follow-up (controls), were selected from the outpatient clinic of two Dutch hospitals. As a reference to the normal population healthy individuals (HI) without a history of venous thromboembolism were invited to participate. The population consisted of: 26 cases, 27 controls, and 26 HI. A panel of predefined biomarkers was measured in venous blood. RESULTS D-dimer showed a decreasing trend from cases to controls to HI; p=0.010. Thrombin/antithrombin complex levels were significantly higher in cases than in controls; p=0.032, and HI; p=0.017. APC-ratio was significantly lower in cases compared to controls; p=0.032, and HI; p=0.011. A significant trend of increasing proTAFI from cases, to controls, and HI; p=0.002 was found. There were no differences in inflammatory markers (CRP, Interleukin-6, Interleukin-8). Thrombomodulin, tissue-plasminogen activator, and von Willebrand factor were higher in patients compared to HI. There was a significant trend of decreasing sVCAM, from cases, to controls, and HI; p=0.029. CONCLUSIONS Patients with PTS displayed increased coagulation activity, an altered pattern of fibrinolytic marker expression, and increased endothelial activation. We found no evidence of systemic inflammation in patients with PTS at 63months since the last DVT.

The IDEAL DVT study, individualised duration elastic compression therapy against long-term duration of therapy for the prevention of post-thrombotic syndrome: protocol of a randomised controlled trial

Introduction Post-thrombotic syndrome (PTS) is a serious complication of deep vein thrombosis (DVT) of the leg that affects 20–50% of patients. Once a patient experiences PTS there is no treatment that effectively reduces the debilitating complaints. Two randomised controlled trials showed that elastic compression stocking (ECS) therapy after DVT for 24 months can reduce the incidence of PTS by 50%. However, it is unclear whether all patients benefit to the same extent from ECS therapy or what the optimal duration of therapy for individual patients should be. ECS therapy is costly, inconvenient, demanding and sometimes even debilitating. Tailoring therapy to individual needs could save substantial costs. The objective of the IDEAL DVT study, therefore, is to evaluate whether tailoring the duration of ECS therapy on signs and symptoms of the individual patient is a safe and effective method to prevent PTS, compared with standard ECS therapy. Methods and analysis A multicentre, single-blinded, allocation concealed, randomised, non-inferiority trial. A total of 864 consecutive patients with acute objectively documented proximal DVT of the leg are randomised to either standard duration of 24 months or tailored duration of ECS therapy following an initial therapeutic period of 6 months. Signs and symptoms of PTS are recorded at regular clinic visits. Furthermore, quality of life, costs, patient preferences and compliance are measured. The primary outcome is the proportion of patients with PTS at 24 months. Ethics and dissemination Based on current knowledge the standard application of ECS therapy is questioned. The IDEAL DVT study will address the central questions that remain unanswered: Which individual patients benefit from ECS therapy and what is the optimal individual treatment duration? Primary ethics approval was received from the Maastricht University Medical Centre. Results Results of the study will be disseminated via peer-reviewed publications and presentations at scientific conferences. Trial registration number NCT01429714 and NTR 2597.

Eliciting patients' preferences for elastic compression stocking therapy after deep vein thrombosis: potential for improving compliance

Essentials Elastic compression stocking (ECS) therapy is used to prevent post‐thrombotic syndrome (PTS). We aimed to elicit patient preferences regarding ECS therapy after deep vein thrombosis. The most valued attributes were PTS risk reduction and the ability to put on the ECS independently. Heterogeneous results with respect to education level stress the importance of proper counselling.

Sample Size Estimation for Non-Inferiority Trials: Frequentist Approach versus Decision Theory Approach

Background Non-inferiority trials are performed when the main therapeutic effect of the new therapy is expected to be not unacceptably worse than that of the standard therapy, and the new therapy is expected to have advantages over the standard therapy in costs or other (health) consequences. These advantages however are not included in the classic frequentist approach of sample size calculation for non-inferiority trials. In contrast, the decision theory approach of sample size calculation does include these factors. The objective of this study is to compare the conceptual and practical aspects of the frequentist approach and decision theory approach of sample size calculation for non-inferiority trials, thereby demonstrating that the decision theory approach is more appropriate for sample size calculation of non-inferiority trials. Methods The frequentist approach and decision theory approach of sample size calculation for non-inferiority trials are compared and applied to a case of a non-inferiority trial on individually tailored duration of elastic compression stocking therapy compared to two years elastic compression stocking therapy for the prevention of post thrombotic syndrome after deep vein thrombosis. Results The two approaches differ substantially in conceptual background, analytical approach, and input requirements. The sample size calculated according to the frequentist approach yielded 788 patients, using a power of 80% and a one-sided significance level of 5%. The decision theory approach indicated that the optimal sample size was 500 patients, with a net value of €92 million. Conclusions This study demonstrates and explains the differences between the classic frequentist approach and the decision theory approach of sample size calculation for non-inferiority trials. We argue that the decision theory approach of sample size estimation is most suitable for sample size calculation of non-inferiority trials.

Timing and duration of compression therapy after deep vein thrombosis

After deep vein thrombosis (DVT) 20-50%, of patients develop post thrombotic syndrome (PTS). Up till now, there is no effective treatment for PTS and prevention is therefore of major importance. Compression therapy after DVT, with elastic compression stockings (ECS), is the only available preventive measure for PTS. However, the usefulness, timing, and duration of compression therapy are matters of debate. The effect of early compression on the long-term development of PTS is still unclear as studies performed so far have conflicting outcomes.16–19 The effectiveness of ECS therapy initiated in the sub-acute phase was assessed in three large randomized controlled trials. Kahn et al could not reproduce the large risk reduction found in the trials by Brandjes and Prandoni et al.20–22 Also for the optimal duration of ECS therapy, a certain conclusion has yet to be drawn. Therefore identification of patients who most likely will benefit from ECS therapy as well as the optimal ECS treatment strategy remain subjects for further study.

Platelet dysfunction in thrombosis patients treated with vitamin K antagonists and recurrent bleeding.

Background Recurrent bleeding can complicate the treatment of thrombosis patients with vitamin K antagonists (VKA), even at a well-regulated level of anticoagulation. In this proof-of-principle study, we investigated whether alterations in platelet function or von Willebrand factor (vWf) contribute to a bleeding phenotype in these patients. Methods In this case-control study 33 well-regulated patients without bleeding events (controls) and 33 patients with recurrent bleeding (cases) were retrospectively included. Thrombin generation and vWf were determined in plasma. Platelet function was assessed by light transmission aggregometry and flow cytometry using a validated panel of agonists. Results Thrombin generation was similarly reduced in controls and cases, in comparison to normal plasma. Plasma vWf level was above the normal range in 85% of controls and 67% of the cases. vWf activity was similarly increased in all patients in comparison to healthy volunteers. Platelet aggregation was in the normal range for almost all patients irrespective of the type of agonist. However, in response to a low collagen dose, platelets from 21% of controls and 27% of cases showed diminished responses. Agonist-induced secretion of alpha- and dense-granules or integrin αIIbβ3 activation were affected in platelets from neither controls nor cases. Conclusion Recurrent bleeding in well-controlled patients on VKA therapy is not explained by anti-hemostatic changes in platelet or vWf function.

Theme 3: Non-invasive management of (recurrent) venous thromboembolism (VTE) and post thrombotic syndrome (PTS)

a Maastricht University Medical Center, Laboratory for Clinical Thrombosis and Hemostasis, Cardiovascular Research Institute Maastricht (CARIM), Netherlands b Thrombosis Center, USA c McMaster University and Thrombosis and Atherosclerosis Research Institute, Canada d Vanderbilt University, Department of Pathology, Microbiology and Immunology, Nashville, USA e University of Groningen, University Medical Center Groningen, Department of Hematology, Netherlands f University of Leeds, Division of Cardiovascular and Diabetes Research, The LIGHT Labs, Leeds, UK g University of Amsterdam, Academic Medical Center, Department of Vascular Medicine, Netherlands h Erasmus University Medical Center, Rotterdam, Department of Hematology, Netherlands

Toll-like receptor 9 gene expression in the post-thrombotic syndrome, residual thrombosis and recurrent deep venous thrombosis: A case-control study

OBJECTIVE Animal models suggest that toll-like receptor 9 (TLR9) promotes thrombus resolution after acute deep venous thrombosis (DVT). We hypothesized that TLR9 expression is lower in patients with post-thrombotic syndrome (PTS) and investigated the role of TLR9 in residual thrombosis (RT) and recurrence. METHODS Patients with a history of DVT with PTS (cases, n=30) and without PTS after minimal 24 months follow-up (controls, n=30) were selected. Healthy individuals (HI, n=29) without DVT were included as reference. TLR9 mRNA expression in leukocytes was determined by qPCR and normalized to the housekeeping succinate dehydrogenase subunit A gene using the ΔCt method. Sub analyses were performed to explore the TLR9 expression in patients with and without RT and multiple DVT episodes. RESULTS The median TLR9 expression was 0.45 (interquartile range 0.31 to 0.93), 0.39 (0.25 to 0.69) and 0.62 (0.32 to 0.75) in cases, controls and HI respectively (p=0.61). The median TLR9 expression was 0.39 (0.26 to 0.51) in patients with RT compared to 0.55 (0.30 to 0.86, p=0.13) in those without. The median TLR9 expression was significantly lower in patients who had one DVT compared to patients with recurrent DVT, 0.37 (0.23 to 0.63) versus 0.55 (0.43 to 0.96) respectively (p<0.01). CONCLUSION No significant difference in TLR9 expression was found between cases, controls and HI. However TLR9 expression seems lower in individuals with DVT and RT, albeit not significant. Interestingly, TLR9 might play a role in recurrent DVT, as the TLR9 expression was significantly higher in patients with recurrent DVT.