von Willebrand factor (VWF) is a multimeric glycoprotein involved in primary hemostasis, recruiting platelets to the site of damaged vessels and acting as a carrier for factor VIII. Quantitative or... Show morevon Willebrand factor (VWF) is a multimeric glycoprotein involved in primary hemostasis, recruiting platelets to the site of damaged vessels and acting as a carrier for factor VIII. Quantitative or qualitative alterations of VWF cause von Willebrand disease (VWD), an inherited bleeding disorder. Conversely, increased VWF levels have been associated with various thrombotic conditions. In this thesis, we investigated the dual role of VWF in bleeding and thrombosis, focusing on VWD and deep vein thrombosis (DVT). In the first part of the thesis, we demonstrated the utility of in silico tools and heterologous cell systems in proving the disease-causing role of VWF variants thus contributing to the confirmation of patient diagnoses. In the second part, we focused on type 3 VWD, the most severe form of this disorder caused by a lack of VWF. We showed that patients with missense variants had a higher VWF propeptide/VWF antigen ratio than carriers of VWF null alleles. This suggested that secreted VWF is rapidly removed from circulation in these patients. Subsequently, we estimated the prevalence of VWF neutralizing and non-neutralizing antibodies, confirming that they are rare side effects of replacement therapy. We also demonstrated that the detection of epitope-specific VWF inhibitors is affected by the test used. In the last part of the thesis, we evaluated the role of ADAMTS13-VWF equilibrium in the pathogenesis of DVT, showing that a slight decrease in ADAMTS13 activity, particularly when combined with increased VWF levels, increases DVT risk. We then sequenced ADAMTS13, VWF, and F8 genes and confirmed that DVT patients carrying a rare ADAMTS13 variant exhibited lower ADAMTS13 activity than non-carriers. Show less
Aim of this thesis was to evaluate contemporary care and prognosis for patients with acute coronary syndrome and identify pitfalls in its treatment. Complications after coronary stent implantation... Show moreAim of this thesis was to evaluate contemporary care and prognosis for patients with acute coronary syndrome and identify pitfalls in its treatment. Complications after coronary stent implantation were explored and demonstrated that in sirolimus-eluting stents, the benefit of reduced repeat revascularization during one year after primary PCI was not sustained during long-term follow-up. Additionally, an increased risk of very late stent thrombosis was suggested. Late stent malapposition, more commonly observed after this stent type and suspected to be involved in the multifactorial etiology of stent thrombosis, is shown to persist in the greater portion of STEMI patients during long-term follow-up, depending on the degree of vessel wall remodelling and change in plaque burden. Women were identified as a sub-population with poorer prognosis early after STEMI. Identification of high-risk patients, and estimation of infarct size and prognosis, which a single measurement of troponin already may indicate, facilitates individualized treatment and likely results in better outcomes. Although numerous novel treatment modalities emerged in recent years, certain pitfalls become increasingly important. Major bleeding is one of them, responsible for an excess mortality amongst STEMI patients after primary PCI, and should be incorporated in risk stratification models for the choice of treatment strategy. Show less
According to current guidelines, patients with thrombocytopenia due to myelosuppression are supported with platelet concentrates in order to prevent and treat bleeding complications using... Show moreAccording to current guidelines, patients with thrombocytopenia due to myelosuppression are supported with platelet concentrates in order to prevent and treat bleeding complications using algorithms which include the level of thrombocytopenia as well as varying clinical parameters, e.g. concomitant infection, the use of anticoagulant drugs, specific interventions. In the last three decades, mainly driven by safety issues, several platelet product changes were made with leukoreduction in the eighties of the previous century, plasma reduction and the use of additive solution in the nineties and the use of pathogen reduction in the first decade of this century.This thesis is mainly based on two randomised controlled trials testing the clinical efficacy of the use of additive solutions and pathogen reduction, essentially showing a decreased clinical efficacy as well as a decrease in adverse transfusion events. A bette r understanding of the pathophysiology of bleeding, thrombocytopenia and platelet transfusion refractoriness will lead to improvements in supportive care as well as patient survival, the common goal of all physicians. Show less
