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Venon W.D.,GastroHepatology Unit | Ponzo P.,GastroHepatology Unit | Sacco M.,GastroHepatology Unit | Mengozzi G.,Molinette Hospital | And 4 more authors.
European Journal of Gastroenterology and Hepatology | Year: 2015

Objectives The management of patients with liver cirrhosis undergoing invasive procedures is controversial and haemostasis assessment using routine laboratory is inappropriate. We evaluated the following: (a) the ability of thromboelastometry to predict the risk of bleeding in cirrhotic patients undergoing invasive procedures and enable a decision on the prophylactic transfusional strategy; (b) the contribution of platelet adhesion and aggregation tests in the assessment of haemostasis. Patients and methods Seventeen cirrhotic patients undergoing invasive procedures were analyzed retrospectively (training set). To obtain preliminary data, an observational study was carried out in 58 patients (test set). All 75 patients were evaluated by thromboelastometry. Platelet adhesion and aggregation were evaluated in 16 patients using Multiplate, PFA-100 and Light Transmission Aggregometry. Factor VIII was dosed in all patients of the test set. Results In the training set, thromboelastometry confirmed the haemostatic assessment shown by the conventional test only in 6/17 (35%) patients. In the test set, thromboelastometry identified all patients who had a bleeding event. In patients with a high risk of bleeding, the use of thromboelastometry was cost-effective, reducing the platelet infusions by 64%. Platelet adhesion/ aggregation abnormalities were observed in 15/16 (94%) patients, but bleeding events occurred only in 2/15 (13%) patients. Conclusion Thromboelastometry appears to be useful to screen cirrhotic patients undergoing invasive procedures to identify the risk of bleeding and to optimize the transfusional strategy. Adhesion/aggregation tests are not useful in identifying patients at risk of bleeding and their application is not cost-effective. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Source

Lippok S.,Ludwig Maximilians University of Munich | Radtke M.,Free University of Berlin | Obser T.,University of Hamburg | Kleemeier L.,Ludwig Maximilians University of Munich | And 4 more authors.
Biophysical Journal | Year: 2016

Proteolysis of the multimeric blood coagulation protein von Willebrand Factor (VWF) by ADAMTS13 is crucial for prevention of microvascular thrombosis. ADAMTS13 cleaves VWF within the mechanosensitive A2 domain, which is believed to open under shear flow. In this study, we combine fluorescence correlation spectroscopy (FCS) and a microfluidic shear cell to monitor real-time kinetics of full-length VWF proteolysis as a function of shear stress. For comparison, we also measure the Michaelis-Menten kinetics of ADAMTS13 cleavage of wild-type VWF in the absence of shear but partially denaturing conditions. Under shear, ADAMTS13 activity on full-length VWF arises without denaturing agent as evidenced by FCS and gel-based multimer analysis. In agreement with Brownian hydrodynamics simulations, we find a sigmoidal increase of the enzymatic rate as a function of shear at a threshold shear rate γË™1/2 = 5522/s. The same flow-rate dependence of ADAMTS13 activity we also observe in blood plasma, which is relevant to predict hemostatic dysfunction. © 2016 Biophysical Society. Source

Feys H.B.,Catholic University of Leuven | Roodt J.,University of the Free State | Roodt J.,Universitas Hospital | Vandeputte N.,Catholic University of Leuven | And 10 more authors.
Blood | Year: 2010

Thrombotic thrombocytopenic purpura (TTP) is the prototypical microangiopathy characterized by disseminated microthromboses, hemolytic anemia, and ultimately organ dysfunction. A link with deficiency of the von Willebrand factor - cleaving protease (ADAMTS13) has been demonstrated, but additional genetic and/or environmental triggers are thought to be required to incite acute illness. Here we report that 4 days of ADAMTS13 functional inhibition is sufficient to induce TTP in the baboon (Papio ursinus), in the absence of inciting triggers because injections with an inhibitory monoclonal antibody (mAb) consistently (n = 6) induced severe thrombocytopenia (< 12 × 109/L), microangiopathic hemolytic anemia, and a rapid rise in serum lactate dehydrogenase. Immunohistochemical staining revealed the characteristic disseminated platelet- and von Willebrand factor - rich thrombi in kidney, heart, brain, and spleen but not lungs. Prolonged inhibition (14 days, n = 1) caused myocardial ischemic damage and asplenia but not death. Control animals (n = 5) receiving equal doses of a noninhibitory anti-ADAMTS13 mAb remained unaffected. Our results provide evidence for a direct link between TTP and ADAMTS13 inhibition and for a mild disease onset. Furthermore, we present a reliable animal model of this disease as an opportunity for the development and validation of novel treatment strategies. © 2010 by The American Society of Hematology. Source

Wanat M.A.,University of Houston | Hart S.R.,The Methodist Hospital | Putney D.,The Methodist Hospital | Liebl M.G.,The Methodist Hospital | Chandler W.,Coagulation Laboratory
Annals of Pharmacotherapy | Year: 2013

Objective: To report a case of heparin-induced thrombocytopenia (HIT) in a patient with concurrent liver dysfunction and a prolonged baseline activated partial thromboplastin time (aPTT) in whom argatroban therapy was monitored with aPTT and a novel plasma-diluted thrombin assay. Case summary: An 80-year-old man with HIT and liver dysfunction was treated with argatroban, which was initiated at a dose of 0.5 μg/kg/min and gradually decreased to 0.09 μg/kg/min. The patient had a mildly prolonged aPTT at baseline (37.5 seconds). He was concurrently monitored with aPTT, per institution protocol, and plasma-diluted thrombin time. Plasma-diluted thrombin times were consistently lower than aPTTs, but mirrored the trend of the aPTTs. Eleven hours after argatroban was stopped, the aPTT remained elevated (53.9 seconds), while the plasma-diluted thrombin time returned to normal range (26.4 seconds). The patient's therapy was transitioned to warfarin and he had a hospital course with no thrombotic or bleeding complications. Discussion: Plasma-diluted thrombin time is a novel laboratory test consisting of 1 part patient plasma diluted with 3 parts normal plasma. Plasma-diluted thrombin time has been shown to blunt the sensitivity of the thrombin time and may be more accurate for drug monitoring. A MEDLINE search revealed 2 studies using the plasma-diluted thrombin time assay. The first study compared aPTT and plasma-diluted thrombin times in blood samples mixed with argatroban, bivalirudin, or lepirudin at 3 different concentrations. Blood samples contained lupus inhibitors, vitamin k deficiency, or normal baseline aPTTs. The aPTT overestimated drug concentrations in all samples with lupus anticoagulant and vitamin k deficiency, while the plasma-diluted thrombin time correctly estimated drug concentrations in nearly all samples. The second study looked at monitoring dabigatran with plasma-diluted thrombin time and found a linear relationship between the plasma-diluted thrombin time and the dabigatran doseresponse curve. Conclusions: Plasma-diluted thrombin time may be an alternative for direct thrombin inhibitor monitoring in patients with elevated aPTT values at baseline. Further randomized control trials are needed to determine its applicability in clinical practice. © 1967-2013 Harvey Whitney Books Co. All rights reserved. Source

Lippok S.,Ludwig Maximilians University of Munich | Obser T.,University of Hamburg | Muller J.P.,Ludwig Maximilians University of Munich | Stierle V.K.,Ludwig Maximilians University of Munich | And 4 more authors.
Biophysical Journal | Year: 2013

Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications. © 2013 Biophysical Society. Source

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