The work described in this thesis had two objectives, specifically focusing on people aged 70 years and older: first, we aimed to investigate the associations between several thrombosis-related... Show moreThe work described in this thesis had two objectives, specifically focusing on people aged 70 years and older: first, we aimed to investigate the associations between several thrombosis-related risk factors described in young and middle-aged populations and the risk of venous thrombosis (VT) in the elderly; second, we aimed to provide insight into several long-term consequences (i.e., health-related quality of life (HRQoL) and long-term risk of mortality) after a first VT at old age. Show less
Lower-leg cast immobilization and (elective) knee arthroscopy are associated with increased risk of symptomatic venous thrombosis, i.e., 2% and 0.6%, respectively. Currently applied... Show moreLower-leg cast immobilization and (elective) knee arthroscopy are associated with increased risk of symptomatic venous thrombosis, i.e., 2% and 0.6%, respectively. Currently applied thromboprophylaxis strategy, with low-molecular weight heparin, were found to be not optimal in both patient groups. In order to improve this, knowledge about underlying mechanisms for hypercoagulability following lower-leg cast application and knee arthroscopy is indispensable. However, as yet, this is not well understood. In this thesis, we established the effect of lower-leg trauma and knee arthroscopy on the coagulation system. We found that lower-leg trauma induces endothelial activation, hyperinflammation and a shift of the haemostatic balance towards a hypercoagulable state. Endothelial activation and hypercoagulability after lower-leg trauma are associated with the risk of venous thrombosis in the first three months. For knee arthroscopy, on the other hand, we did not detect any changes in plasma which point in the direction of thrombus formation. It becomes clear that in both situations, different mechanistic pathways of the development of venous thrombosis are involved. The knowledge provided by this thesis can be considered as the first step in the exploration of novel prevention targets for venous thrombosis and potential biomarkers for prediction of venous thrombosis in both patient populations. Show less
Munsch, G.; Goumidi, L.; Vlieg, A.V.; Ibrahim-Kosta, M.; Bruzelius, M.; Deleuze, J.F.; ... ; Trégouët, D.A. 2023
BackgroundIn studies of time-to-events, it is common to collect information about events that occurred before the inclusion in a prospective cohort. When the studied risk factors are independent of... Show moreBackgroundIn studies of time-to-events, it is common to collect information about events that occurred before the inclusion in a prospective cohort. When the studied risk factors are independent of time, including both pre- and post-inclusion events in the analyses, generally referred to as relying on an ambispective design, increases the statistical power but may lead to a selection bias. In the field of venous thromboembolism (VT), ABO blood groups have been the subject of extensive research due to their substantial effect on VT risk. However, few studies have investigated their effect on the risk of VT recurrence. Motivated by the study of the association of genetically determined ABO blood groups with VT recurrence, we propose a methodology to include pre-inclusion events in the analysis of ambispective studies while avoiding the selection bias due to mortality.MethodsThis work relies on two independent cohorts of VT patients, the French MARTHA study built on an ambispective design and the Dutch MEGA study built on a standard prospective design. For the analysis of the MARTHA study, a weighted Cox model was developed where weights were defined by the inverse of the survival probability at the time of data collection about the events. Thanks to the collection of information on the vital status of patients, we could estimate the survival probabilities using a delayed-entry Cox model on the death risk. Finally, results obtained in both studies were then meta-analysed.ResultsIn the combined sample totalling 2,752 patients including 993 recurrences, the A1 blood group has an increased risk (Hazard Ratio (HR) of 1.18, p = 4.2 x 10(-3)) compared with the O1 group, homogeneously in MARTHA and in MEGA. The same trend (HR = 1.19, p = 0.06) was observed for the less frequent A2 group.ConclusionThe proposed methodology increases the power of studies relying on an ambispective design which is frequent in epidemiologic studies about recurrent events. This approach allowed to clarify the association of ABO blood groups with the risk of VT recurrence. Besides, this methodology has an immediate field of application in the context of genome wide association studies. Show less
Patients with lower leg cast immobilization or who had knee arthroscopy have an increased risk of venous thrombosis. Because of this increased risk, thromboprophylaxis was given to the majority of... Show morePatients with lower leg cast immobilization or who had knee arthroscopy have an increased risk of venous thrombosis. Because of this increased risk, thromboprophylaxis was given to the majority of these patients in the Netherlands, despite insufficient evidence for its effect. In this thesis, two large randomized controlled trials (including 1500 patients each, in which half of patients were randomized to prophylaxis with Low Molecular Weight Heparin (LMWH) and half of patients to no treatment) are described. Despite having an increased VTE risk, routine thromboprophylaxis with low dose LMWH did not decrease VTE risk in these patients. Therefore, we recommend no routine thromboprophylaxis with anticoagulants to these patients. Identification of high-risk patients and selective treatment of patients can be beneficial. Therefore, prediction models for the development of VTE in these patients were developed. The prediction models had good predictive value and were validated in two other studies. Hence, identification of high-risk patient can help to optimize prophylactic treatment: providing a higher dose or longer duration of anticoagulant treatment to patients with an additionally increased risk, whilst patients with a low risk will not be needlessly exposed to the burden and risk of anticoagulants. Show less
Cancer patients have a four- to sevenfold increased risk of developing cancer-associated thrombosis (CAT), which is associated with a strong increase in morbidity and mortality. Not all cancer... Show moreCancer patients have a four- to sevenfold increased risk of developing cancer-associated thrombosis (CAT), which is associated with a strong increase in morbidity and mortality. Not all cancer patients receive thromboprophylaxis as this may lead to adverse events in a cancer population that is already at increased risk for major bleedings. Different risk prediction models have been developed to identify cancer patients at high risk of developing CAT that may be selected for thromboprophylaxis. However, risk models using the currently established biomarkers and clinical parameters perform poorly, particularly when validated in independent cohorts. Discovery of new and better biomarkers are therefore urgently needed. This review describes how aberrations in the genetic profile of the tumor and host influence a hypercoagulable state, and explores how these can be used as novel biomarker to improve CAT risk prediction. Show less
Background: The adipocyte-derived hormone leptin has been associated with altered blood coagulation in in vitro studies. However, it is unclear whether this association is relevant in vivo and to... Show moreBackground: The adipocyte-derived hormone leptin has been associated with altered blood coagulation in in vitro studies. However, it is unclear whether this association is relevant in vivo and to what extent this association is influenced by total body fat. Therefore, we aimed to examine the association between serum leptin and blood coagulation while taking total body fat into account in a population-based cohort study.Methods: We performed a cross-sectional analysis with baseline measurements of 5797 participants of the Netherlands Epidemiology of Obesity (NEO) study, a population-based cohort of middle-aged men and women. We examined associations between serum leptin concentration and coagulation factor concentrations and parameters of platelet activation in linear regression analyses. All analyses were adjusted for multiple covariates, including total body fat.Results: In multivariable adjusted analyses a 1 mu g/L higher serum leptin concentration was associated with a 0.22 IU/dL (95% CI: 0.11, 0.32) higher FVIII concentration and a 0.20 IU/dL (95% CI: 0.14, 0.27) higher FIX concentration (3.5 IU/dL FVIII and 3.2 IU/dL FIX per SD leptin). Serum leptin concentration was not associated with FXI, fibrinogen, platelet count, mean platelet volume and platelet distribution width in multivariable adjusted analyses.Discussion: This study showed that serum leptin concentration was associated with higher concentrations of FVIII and FIX in an observational study, which could be clinically relevant. Show less
During my research project we mainly focussed on studying the pathophysiology of venous and arterial thrombosis in mice. When we transiently lowered plasma protein levels of natural anticoagulants... Show moreDuring my research project we mainly focussed on studying the pathophysiology of venous and arterial thrombosis in mice. When we transiently lowered plasma protein levels of natural anticoagulants antithrombin and protein C using RNA interference, mice developed venous thrombosis in the head. In contrast to other mouse models for venous thrombosis where surgery is required for provoking the disease, mice injected with RNA interference against the mRNA of Serpinc1 and Proc (antithrombin and protein C, respectively) developed venous thrombosis without additional handlings. In this unique form of venous thrombosis, we studied the roles of platelets, neutrophils, and coagulation factor XII. These factors have been shown to be indispensable in experimental venous thrombosis in other mouse models, and they have been introduced as novel therapeutic targets. For the second part of my thesis we again used the RNA interference approach, to lower natural anticoagulation in atherosclerotic mice. When we lowered protein C in these mice, they developed atherothrombosis in the aortic root without any additional intervention. This unique form of atherothrombosis has been showed in multiple independent experiments, and we aimed to further characterize the process to learn more about prevention atherothrombosis in atherosclerotic mice and the role of protein C. Show less
In this thesis the risk factors of venous thrombosis will be discussed in the general and particularly the elderly population. The goal of this thesis is to provide insights on risk factors of... Show moreIn this thesis the risk factors of venous thrombosis will be discussed in the general and particularly the elderly population. The goal of this thesis is to provide insights on risk factors of thrombosis in the elderly population, in order to advance our basic understanding of physiological age-related changes that increase the risk of venous thrombosis and which may ultimately lead to improved personalized interventions. In this chapter firstly background information will be provided on risk factors for venous thrombosis, focussing specifically on age as a risk factor. Secondly, the role of veins and venous valves in the development of venous thrombosis will be discussed and thirdly, global assays as a potential tool to identify patients at high risk for venous thrombosis will be considered. The study populations used in this thesis will discussed, and an outline of this thesis will be provided. Show less
Several studies during the past decade have shown that patients with venous thrombosis have an increased risk of subsequent arterial thrombosis, thus suggesting a link between the two diseases. The... Show moreSeveral studies during the past decade have shown that patients with venous thrombosis have an increased risk of subsequent arterial thrombosis, thus suggesting a link between the two diseases. The aim of this thesis was to investigate the associations of traditional cardiometabolic risk factors with risk of a first and recurrent venous thrombosis. We showed that levels of major lipids, i.e. total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides, were not associated with a first venous thrombosis. In contrast, low levels of apolipoproteins B and A1 were associated with an increased risk of a first event. Regarding recurrence, tests for lipid levels, glucose levels and hematologic variables did not identify patients at an increased risk of recurrent venous thrombosis, and these tests should not be done for this indication nor influence decisions on duration of anticoagulant treatment. In this thesis, we further searched for associations between lipids and hemostatic factors, and found that levels of vitamin K-dependent factors (VKDFs), including factor IX, were associated with triglyceride levels. We hypothesized that this association could be explained by common mechanisms, regulating levels of both VKDFs and triglycerides. Show less
Charmet, R.; Vlieg, A.V.; Germain, M.; Roussel, R.; Marre, M.; Debette, S.; ... ; Tregouet, D.A. 2017
Patients with deep vein thrombosis or pulmonary embolism remain at risk for recurrent venous thrombosis. This risk is pronounced in the first months after the acute episode and declines in... Show morePatients with deep vein thrombosis or pulmonary embolism remain at risk for recurrent venous thrombosis. This risk is pronounced in the first months after the acute episode and declines in subsequent years. Although the existence of an extensive list of risk factors may seem reassuring, it does not come close to give us all the answers: many people have several of these risk factors but never develop thrombosis; others suffer from thrombosis but have none. Therefore, the challenge that we are facing today is not to just add more risk factors to this list but rather to integrate them all in a causal model that allows us to understand how and when thrombotic disease develops. The idea behind “the thrombosis potential model” is that an individual is at risk for venous thrombosis throughout life, which is reflected in the ‘thrombosis potential’ and that each risk factor contributes to increase the potential. Only when the combination of thrombosis risk factors reach a certain potential, venous thrombosis will occur. In this thesis, the thrombosis potential model will be applied to several known risk factors for venous thrombosis to better understand why first and recurrent venous thrombosis can develop in an individual patient. Show less
Secondary prevention of recurrent venous can be achieved in two ways, either by elimination of modifiable risk factors or by extending the anticoagulant treatment period in patients at high risk... Show moreSecondary prevention of recurrent venous can be achieved in two ways, either by elimination of modifiable risk factors or by extending the anticoagulant treatment period in patients at high risk of recurrence. The aim of this thesis was to identify modifiable risk factors for as well as factors that might be able to predict recurrent venous thrombotic events. This thesis reports on an increased risk of recurrences in women who continue or start using hormonal contraceptives after a first venous thrombotic event, suggesting that refraining from this modifiable risk factor decreases the risk of recurrence. Furthermore, this thesis describes several factors, male sex, unprovoked first event, levels of coagulation factor VIII and antibiotic use to be associated with recurrent venous thrombosis. These factors should eventually be taken together and used to build a prognostic model, which will be able to predict recurrences at a refined and individual level. Show less
In this thesis we show the results of the AT-AGE study, a two-center, population based case-control study in Leiden, the Netherlands and Burlington, Vermont, US, in which consecutive patients aged... Show moreIn this thesis we show the results of the AT-AGE study, a two-center, population based case-control study in Leiden, the Netherlands and Burlington, Vermont, US, in which consecutive patients aged 70 years and older with deep venous thrombosis (DVT) in the leg or a pulmonary embolism (PE), were identified. The AT-AGE study was specifically designed to optimise the participation-rate in the older population. Therefore, we performed home visits to all participants. We showed that conventional risk factors such as immobilisation due to hospital admission, and also immobility at home, due to for instance infection and minor injury, increase the risk of venous thrombosis. Also genetic risk factors, such as Factor V Leiden (FVL, rs6025) and the prothrombin 20210A mutation (PT20210, rs1799963) increase the risk of venous thrombosis. We report the presence of age-specific risk factors: functional impairment, low hand grip strength and venous insufficiency, such as varicose veins and leg oedema. Also we identified new high risk groups in older people, e.g., recent hospital discharge in which preventive measures could be of special interest. Show less
This thesis aimed to identify possible risks associated with erythropoiesis-simulating agent (ESA) use. First, trends in anemia management are described, showing less ESA use in Swedish patients... Show moreThis thesis aimed to identify possible risks associated with erythropoiesis-simulating agent (ESA) use. First, trends in anemia management are described, showing less ESA use in Swedish patients with chronic kidney disease (CKD) and less ESA-treated patients had a hemoglobin above 12 g/dL. Furthermore it is shown that ESA- treated pre-dialysis patients in the Netherlands received more antihypertensive agents than patients without ESA, confirming the hypertensive effect of ESA. However, no relevant difference in routinely measured blood pressure was observed between patients with and without ESA treatment, thus the hypertensive effect of ESAs could be controlled in clinical practice. In addition, no excess of thrombotic events was shown in ESA-treated dialysis patients compared to patients without ESA treatment. In contrast, a higher risk of cardiovascular events with ESA use was indicated in Danish patients with multiple myeloma and myelodyslastic syndrome. Also, with two analytical approaches, a harmful effect of high ESA doses on mortality was indicated in Dutch dialysis patients. Last, it was shown that ESA resistance was associated with mortality in both hemodialysis and peritoneal dialysis patients. To conclude, treatment with high ESA doses was associated with a higher risk of mortality, but the mechanism is largely unknown. Show less
