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
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
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
