ADAMTS13 activity to antigen ratio in physiological and pathological conditions associated with an increased risk of thrombosis

Hereditary TTP/Upshaw-Schulman syndrome: the ductus arteriosus controls newborn survival

Hereditary TTP (hTTP), termed Upshaw-Schulman syndrome, is an ultra-rare disorder caused by a severe deficiency of plasma ADAMTS13 activity that allows circulation of ultra-large von Willebrand factor (UL-VWF) multimers. The greatest risk for hTTP is in their first days after birth, when 35-50% of patients will have severe hemolysis, jaundice, and thrombocytopenia. It is often fatal without effective treatment. In utero, fetal blood flowing from the pulmonary artery through the ductus arteriosus (DA) to the aorta is under low-shear-force. At birth, blood flow through the DA reverses to a left-to-right shunt, and the diameter of the DA begins to decrease due to hyper-oxygenated blood and decreased plasma prostaglandin E2. This causes turbulent circulation that unfolds UL-VWF, allowing platelet aggregation. If the DA closes promptly, hTTP newborns survive, but if it remains patent, turbulent circulation persists, triggering microvascular thrombosis. hTTP is commonly diagnosed as hemolytic disease of the fetus and newborn (HDFN) caused by anti-red cell antibodies and treated with exchange blood transfusion, which prevents kernicterus even when the diagnosis of hTTP is missed. The diagnosis of newborn-onset hTTP should be considered because HDFN does not cause severe thrombocytopenia, which might be effectively treated with recombinant ADAMTS13.

REVIEWING THE DYSREGULATION OF ADAMTS13 AND VWF IN SEPSIS

ABSTRACT

Sepsis is defined as a life-threatening organ dysfunction caused by excessive host response to infection, and represents the most common cause of in-hospital deaths. Sepsis accounts for 30% of all critically ill patients in the intensive care unit (ICU), and has a global mortality rate of 20%. Activation of blood coagulation during sepsis and septic shock can lead to disseminated intravascular coagulation, which is characterized by microvascular thrombosis. Von Willebrand factor (VWF) and ADAMTS13 are two important regulators of blood coagulation that may be important links between sepsis and mortality in the ICU. Herein we review our current understanding of VWF and ADAMTS13 in sepsis and other critical illnesses and discuss their contribution to disease pathophysiology, their use as markers of severe illness, and potential targets for new therapeutic development.

The Role of the von Willebrand Factor Collagen-Binding Assay (VWF:CB) in the Diagnosis and Treatment of von Willebrand Disease (VWD) and Way Beyond: A Comprehensive 36-Year History

The von Willebrand factor (VWF) collagen binding (VWF:CB) assay was first reported for use in von Willebrand diagnostics in 1986, by Brown and Bosak. Since then, the VWF:CB has continued to be used to help diagnose von Willebrand disease (VWD) (correctly) and also to help assign the correct subtype, as well as to assist in the monitoring of VWD therapy, especially desmopressin (DDAVP). However, it is important to recognize that the specific value of any VWF:CB is predicated on the use of an optimized VWF:CB, and that not all VWF:CB assays are so optimized. There are some good commercial assays available, but there are also some "not-so-good" commercial assays available, and these may continue to give the VWF:CB "a bad reputation." In addition to VWD diagnosis and management, the VWF:CB found purpose in a variety of other applications, from assessing ADAMTS13 activity, to investigation into acquired von Willebrand syndrome (especially as associated with use of mechanical circulatory support or cardiac assist devices), to assessment of VWF activity in disease states in where an excess of high-molecular-weight VWF may accumulate, and lead to increased (micro)thrombosis risk (e.g., coronavirus disease 2019, thrombotic thrombocytopenic purpura). The VWF:CB turns 37 in 2023. This review is a celebration of the utility of the VWF:CB over this nearly 40-year history.

Von Willebrand factor processing in patients with advanced chronic liver disease and its relation to portal hypertension and clinical outcome

BACKGROUND AND AIMS

Endothelial dysfunction and portal hypertension (PH) are reflected by increased von Willebrand factor antigen (VWF-Ag) levels in advanced chronic liver disease (ACLD). This study investigated VWF release and cleavage and their association with PH and clinical outcomes.

METHODS

Levels of VWF-Ag, VWF-N (VWF-propeptide), and VWF-A (VWF processed by the main VWF-cleaving protease ADAMTS13) were assessed in 229 patients with clinically stable ACLD (hepatic venous pressure gradient [HVPG] ≥ 6 mmHg; absence of bacterial infections or acute decompensation) undergoing HVPG-measurement. Liver-healthy individuals served as controls (n = 24).

RESULTS

VWF-Ag and VWF-N were similarly accurate for the identification of clinically significant PH (CSPH; HVPG ≥ 10 mmHg) in compensated ACLD (AUROC: VWF-Ag 0.748; VWF-N 0.728). ADAMTS13 activity was similar between patients with ACLD and controls and did not correlate with PH and disease severity, whereas VWF cleavage decreased in patients with CSPH (i.e., VWF-Ag/-A-ratio increased). In vitro VWF activity strongly reflected VWF-Ag levels (Spearman's r = 0.874, p < 0.001), but decreased (vs. controls) in patients with CSPH when normalized to VWF-Ag levels (VWF-activity/-Ag-ratio). VWF-Act/-Ag ratio correlated negatively with ADAMTS13 activity (r =- 0.256, p < 0.001). ADAMTS13 activity was independently predictive for (i) portal vein thrombosis (PVT) and (ii) hepatic decompensation or liver-related death.

CONCLUSIONS

VWF-Ag levels and its propeptide are similarly suitable surrogates of PH in patients with compensated ACLD. ADAMTS13-Act was not linked to disease and PH severity, however, when normalized to VWF-Ag, both VWF cleavage and VWF activity were decreased in patients with CSPH, as compared to liver-healthy individuals. Low ADAMTS13-Act was associated with presumably more procoagulant VWF and adverse outcomes.

CLINICAL TRIAL NUMBER

NCT03267615.

Dynamic and functional linkage between von Willebrand factor and ADAMTS-13 with aging: an Atherosclerosis Risk in Community study

BACKGROUND

von Willebrand factor (VWF) is a multimeric glycoprotein critically involved in hemostasis, thrombosis, and inflammation. VWF function is regulated by its antigen levels, multimeric structures, and the state of enzymatic cleavage. Population studies in the past have focused almost exclusively on VWF antigen levels in cross-sectional study designs.

OBJECTIVE

To identify subjects in the Atherosclerosis Risk in Community study who had persistently low and high VWF antigen over 10 years and to quantify longitudinal changes in the biological activities and cleavage of VWF in these subjects.

METHODS

We measured VWF antigen, propeptide, adhesive activities, and cleavage by ADAMTS-13 quantified using a mass spectrometry method that detected the cleaved VWF peptide EQAPNLVY, as well as coagulation factor VIII activity.

RESULTS

We determined the mean subject-specific increase in VWF to be 22.0 International Units (IU)/dL over 10 years, with 95% between -0.3 and 59.7 IU/dL. This aging-related increase was also detected in VWF propeptide levels, ristocetin cofactor activity, and VWF binding to collagen. We identified 4.1% and 25.0% of subjects as having persistently low (<50 IU/dL) and high (>200 IU/dL) VWF antigen, respectively. Subjects with persistently low VWF had enhanced ristocetin cofactor activity, whereas those with persistently high VWF had elevated levels of ADAMTS-13, resulting in a comparable rate of VWF cleavage between the 2 groups.

CONCLUSIONS

These results provide new information about the effects of aging on VWF antigens and adhesive activity and identify a functional coordination between VWF and the rate of its cleavage by ADAMTS-13.

Microvascular Thrombosis and Liver Fibrosis Progression: Mechanisms and Clinical Applications

Fibrosis is an unavoidable consequence of chronic inflammation. Extracellular matrix deposition by fibroblasts, stimulated by multiple pathways, is the first step in the onset of chronic liver disease, and its propagation promotes liver dysfunction. At the same time, chronic liver disease is characterized by alterations in primary and secondary hemostasis but unlike previously thought, these changes are not associated with an increased risk of bleeding complications. In recent years, the role of coagulation imbalance has been postulated as one of the main mechanisms promoting hepatic fibrogenesis. In this review, we aim to investigate the function of microvascular thrombosis in the progression of liver disease and highlight the molecular and cellular networks linking hemostasis to fibrosis in this context. We analyze the predictive and prognostic role of coagulation products as biomarkers of liver decompensation (ascites, variceal hemorrhage, and hepatic encephalopathy) and liver-related mortality. Finally, we evaluate the current evidence on the application of antiplatelet and anticoagulant therapies for prophylaxis of hepatic decompensation or prevention of the progression of liver fibrosis.

Impact of the von Willebrand factor-ADAMTS-13 axis on the risk of future venous thromboembolism

BACKGROUND

von Willebrand factor (VWF) and its cleaving protease, ADAMTS-13, form a pivotal axis that regulates hemostasis. However, the role of the VWF-ADAMTS-13 axis in the risk of future venous thromboembolism (VTE) is unknown.

OBJECTIVES

To investigate whether plasma ADAMTS-13 levels and an imbalance with VWF levels, assessed as the VWF/ADAMTS-13 ratio, are associated with the risk of future VTE.

PATIENTS/METHODS

A population-based nested case-control study, comprising 383 incident VTE cases and 780 age- and sex-matched controls, was derived from the Tromsø study cohort (1994-2007). Antigen levels of ADAMTS-13 and VWF were measured in plasma samples obtained at cohort baseline. Odds ratios (ORs) with 95% CIs were estimated according to quartile cutoffs of ADAMTS-13 and VWF/ADAMTS-13 ratio determined in controls.

RESULTS

In age- and sex-adjusted analysis, ADAMTS-13 levels were inversely associated with the VTE risk, with an OR of 1.40 (95% CI, 0.99-1.99) for the lowest vs highest quartiles. The VWF/ADAMTS-13 ratio was linearly associated with the VTE risk (P for trend = .001), with an OR of 1.70 (95% CI, 1.19-2.43) for the highest vs lowest quartiles, and the association was particularly pronounced for unprovoked VTE (OR, 2.81; 95% CI, 1.65-4.81). The ORs were only slightly attenuated after additional adjustments for body mass index and C-reactive protein.

CONCLUSIONS

Lowered ADAMTS-13 levels and an imbalance between ADAMTS-13 and VWF levels, reflected by an increased VWF/ADAMTS-13 ratio, were associated with an increased risk of future VTE. Our findings suggest that the VWF-ADAMTS-13 axis is involved in the pathogenesis of VTE.

Immune thrombotic thrombocytopenic purpura: Spotlight on long-term outcomes and survivorship

Advances in diagnosis and treatment have dramatically improved survival of acute immune thrombotic thrombocytopenic purpura (iTTP) and iTTP has evolved from an acute fatal condition to a chronic relapsing disorder. In addition to the risk of iTTP relapse, iTTP survivors are at risk of multiple adverse health outcomes including higher than expected rates of all-cause mortality, increased rates of stroke and other cardiovascular disease, and higher rates of morbidities such as obesity, hypertension, and autoimmune disorders. iTTP survivors also report neurocognitive impairment, depression, and reduced quality of life. Women with iTTP are at risk for recurrent iTTP, preeclampsia, and other maternal and fetal complications in subsequent pregnancies. ADAMTS13 activity during clinical remission has emerged as an important targetable risk factor for iTTP relapse and other outcomes including stroke and all-cause mortality. This review summarizes current literature regarding the epidemiology and potential mechanisms for adverse long-term sequelae of iTTP, outlines current best practices in iTTP survivorship care, and highlights a research agenda to improve long-term iTTP outcomes.

An update on the pathogenesis and diagnosis of thrombotic thrombocytopenic purpura

INTRODUCTION

Severe ADAMTS13 deficiency defines thrombotic thrombocytopenic purpura (TTP). ADAMTS13 is responsible for VWF cleavage. In the absence of this enzyme, widespread thrombi formation occurs, causing microangiopathic anemia and thrombocytopenia and leading to ischemic organ injury. Understanding ADAMTS13 function is crucial to diagnose and manage TTP, both in the immune and hereditary forms.

AREAS COVERED

The role of ADAMTS13 in coagulation homeostasis and the consequences of its deficiency are detailed. Other factors that modulate the consequences of ADAMTS13 deficiency are explained, such as complement system activation, genetic predisposition, or the presence of an inflammatory status. Clinical suspicion of TTP is crucial to start prompt treatment and avoid mortality and sequelae. Available techniques to diagnose this deficiency and detect autoantibodies or gene mutations are presented, as they have become faster and more available in recent years.

EXPERT OPINION

A better knowledge of TTP pathophysiology is leading to an improvement in diagnosis and follow-up, as well as a customized treatment in patients with TTP. This scenario is necessary to define the role of new targeted therapies already available or coming soon and the need to better diagnose and monitor at the molecular level the evolution of the disease.

ADAMTS-13/von Willebrand factor ratio: A prognostic biomarker for portal vein thrombosis in compensated cirrhosis. A prospective observational study

BACKGROUND AND AIMS

In cirrhosis, decreased portal flow velocity, thrombophilia factors, and portal hypertension are considered risk factors for portal vein thrombosis (PVT). In cirrhosis, the transformation of the stellate cells causes a progressive decrease of ADAMTS-13, while VWF multimers secretion by endothelial cells is strongly enhanced. This imbalance leads to an accumulation of ultra-large VWF multimers that in sinusoidal circulation could favor PVT both in intra- and extra-hepatic branches, mostly in decompensated cirrhosis. This prospective study was aimed at identifying possible clinical, biochemical, and hemostatic factors predictive for non-tumoral PVT in a cohort of patients with compensated cirrhosis.

METHODS

Seventynine compensated cirrhosis patients were prospectively followed for 48 months, receiving a periodic Doppler-ultrasound liver examination associated with an extensive evaluation of clinical, biochemical, and hemostatic profile.

RESULTS

Five patients developed PVT (cumulative prevalence = 6.3%), occurring 4-36 months after enrollment. In logistic regression analysis, the ADAMTS-13/VWF:GpIbR ratio < 0.4 was the only independent variable significantly associated with PVT (OR 14.6, 95% C.I.:1.36-157.2, p = 0.027). A Cox-regression-analysis confirmed this finding (HR = 7.7, p = 0.027).

CONCLUSIONS

The ADAMTS-13/VWF ratio < 0.4 measured in compensated cirrhosis could be a reliable predictive biomarker for PVT development, paving the way to novel therapeutic strategies to prevent and treat PVT in this clinical setting.

Diabetes mellitus and diabetic nephropathy: a review of the literature on hemostatic changes in coagulation and thrombosis

Vascular complications lead to morbidity and mortality in patients with diabetes. Diabetic nephropathy (DN) is one of the main life-threatening problems for these patients, as it is the main cause of end-stage renal disease. This study aimed to measure the clinical effects of diabetes in patients with diabetes and in patients with diabetic nephropathy. Improved hypoglycemic control in patients with diabetes could impressively reduce platelet hyperreactivity, and oxidative stress alters the levels of many coagulation and thrombosis factors, resulting in an abnormal hemostasis and impaired levels of numerous serum markers. Most studies have revealed that coagulation factor levels are high in patients with diabetes and nephrodiabetes. Serum inflammatory factors, and coagulation and endothelial functions are good predictors of diabetic nephropathy. This literature review was conducted with access to scholarly databases and Google Scholar through Qassim University, and it analyzes studies from early 2010 until November 2020. Many studies have inferred that diabetes severely affects hemostasis and increases the risk of cardiovascular disease.

TTP: From empiricism for an enigmatic disease to targeted molecular therapies

The 100th anniversary of the first description of Thrombotic Thrombocytopenic Purpura (TTP) as a disease by Dr. Eli Moschcowitz approaches. For many decades, TTP remained mostly a mysterious fatal condition, where diagnosis was often post-mortem. Initially a pentad of symptoms was identified, a pattern that later revealed to be fallible. Sporadic observations led to empiric interventions that allowed for the first impactful breakthrough in TTP treatment, almost 70 years after its first description: the introduction of plasma exchange and infusions as treatments. The main body of knowledge within the field was gathered in the latest three decades: patient registries were set and proved crucial for advancements; the general mechanisms of disease have been described; the diagnosis was refined; new treatments and biomarkers with improvements on prognosis and management were introduced. Further changes and improvements are expected in the upcoming decades. In this review, we provide a brief historic overview of TTP, as an illustrative example of the success of translational medicine enabling to rapidly shift from a management largely based on empiricism to targeted therapies and personalized medicine, for the benefit of patients. Current management options and present and future perspectives in this still evolving field are summarized.

The Role of von Willebrand Factor Antigen in Predicting Survival of Patients with HBV-Related Cirrhosis

OBJECTIVE

The model for end-stage liver disease (MELD) scoring system cannot be used to assess the deterioration of patients with liver cirrhosis caused by infection and portal hypertension. Elevated von Willebrand factor antigen (vWF-Ag) in plasma is associated with portal pressure and complications in patients with liver cirrhosis. We aimed to evaluate whether the addition of vWF-Ag can improve the risk prediction ability of the MELD scoring system.

METHODS

A total of 228 patients with hepatitis B virus (HBV)-related liver cirrhosis were eligible for inclusion in this retrospective study. The vWF-Ag level was assessed by enzyme-linked immunosorbent assay (ELISA). The endpoint of this study was defined as the time to liver transplantation or death. Univariate and multivariate analyses were performed to assess the risk factors associated with transplant-free mortality. Receiver operating characteristic (ROC) curve analysis was used to assess potential discriminatory variables for transplant-free mortality.

RESULTS

During a median follow-up interval of 30.23 months, 124 patients (54.4%) reached the endpoint of this study. Patients who died or underwent liver transplantation had elevated levels of MELD and vWF-Ag. Moreover, vWF-Ag and MELD showed comparable predictive potential for transplant-free survival (area under the curve [AUC], vWF-Ag = 0.71; AUC, MELD = 0.73). Ultimately, vWF-Ag can significantly improve the predictive potential of MELD in determining transplant-free mortality (AUC, MELD-vWF-Ag = 0.79, P = 0.006).

CONCLUSION

An elevated vWF-Ag level was independently associated with transplant-free mortality in patients with liver cirrhosis. The inclusion of vWF-Ag in the MELD scoring system can improve mortality predictions in patients with liver cirrhosis.

Reduced ADAMTS13 Activity in Correlation with Pathophysiology, Severity, and Outcome of COVID-19: A Retrospective Observational Study

BACKGROUND

Low ADAMTS13 activity has been suggested to be an interplaying factor in the pathogenesis of COVID-19, considering that it is a thromboinflammatory disease with high risk of microthrombosis.

OBJECTIVES

The study aimed to explore the correlation between ADAMTS13 activity and the pathophysiological pathway of COVID-19.

METHODS

We carried out a retrospective observational study of 87 patients with COVID-19 in NMC Royal Hospital, Abu Dhabi, UAE. ADAMTS13 activity was measured and compared with patients' characteristics and clinical outcomes.

RESULTS

Low ADAMTS13 activity was associated with pneumonia (p = 0.007), severity of COVID-19 (p <0.001), and mechanical ventilation rates (p = 0.018). Death was more frequently observed among patients (5 patients) with low ADAMTS13 activity compared with normal activity (1 patient), as well as inflammatory markers. Decreased ADAMTS13 activity increased with the risk of pneumonia, severity of COVID-19, need for mechanical ventilation, and use of anticoagulants ([OR = 4.75, 95% CI 1.54-18.02, p = 0.011], [OR = 6.50, 95% CI 2.57-17.74; p <0.001], [OR = 4.10, 95% CI 1.29-15.82; p = 0.024], [OR = 8.00, 95% CI 3.13-22.16; p <0.001], respectively). The low ADAMTS13 activity group had a slightly longer time to viral clearance than the normal ADAMTS13 activity group, but it was not statistically significant (20 days, 95% CI 16-27 days vs 17 days, 95% CI 13-22 days; p = 0.08; Log rank = 3.1).

CONCLUSIONS

Low ADAMTS13 activity has been linked to pneumonia, COVID-19 severity, use of anticoagulants, and need for mechanical ventilation but not to mortality. We propose rADAMTS13 as a novel treatment for severe COVID-19.

Evolution of Nonmalignant Portal Vein Thrombosis in Liver Cirrhosis: A Pictorial Review

Portal vein thrombosis (PVT) is a common complication in liver cirrhosis, especially in advanced cirrhosis. It may be related to a higher risk of liver-related events and liver function deterioration. Imaging examinations can not only provide an accurate diagnosis of PVT, such as the extent of thrombus involvement and the degree of lumen occupied, but also identify the nature of thrombus (i.e., benign/malignant and acute/chronic). Evolution of PVT, mainly including development, recanalization, progression, stability, and recurrence, could also be assessed based on the imaging examinations. This article briefly reviews the pathophysiology, diagnosis, classification, and evolution of PVT with an emphasis on their computed tomography imaging features.

The hemostatic and thrombotic complications of liver disease

Hepatic cirrhosis leads to numerous hematologic derangements resulting in a complex and tenuously rebalanced hemostatic milieu. The utility of common hematologic tests including the INR and aPTT in assessing hemostatic and thrombotic risk in patients with cirrhosis is limited, and consensus on transfusion thresholds and proper management of thrombotic complications continues to evolve. This review summarizes the pathophysiology of key derangements of hemostasis including those of platelets, von Willebrand factor, pro- and anticoagulation factors, and fibrin. Additionally, the pathogenesis, consequences, optimal management, and prevention of major thrombotic and bleeding complications in cirrhosis arte discussed.

Liver transplantation of a patient with extreme thrombocytopenia - A case report

BACKGROUND

Patients with chronic liver disease (CLD) planned for liver transplantation (LT) often show severe thrombocytopenia, but there is a lack of evidence in deciding the threshold for prophylactic platelet transfusion.

CASE

A 47-year-old female with acute liver failure was referred for LT. Despite daily transfusion of platelets, platelet counts remained under 10,000/µl. During LT, 2 units of single donor platelets (SDP) were transfused. Although platelet counts remained extremely low (3,000-4,000/µl) no diffuse oozing was observed and the blood loss was 860 ml. Postoperatively, there was no sign of active bleeding or oozing, and the patient received only 1 unit SDP transfusion.

CONCLUSIONS

CLD patients may have severe thrombocytopenia. However, primary hemostasis may not be significantly hindered due to the existence of rebalanced hemostasis. Prophylactic platelet transfusion in these patients should not be decided based on platelet counts only, but also take other coagulation tests and clinical signs into consideration.

Prospective Evaluation of the Pre-, Intra-, and Postoperative Kinetics of ADAMTS-13, von Willebrand Factor, and Interleukin-6 in Vascular Surgery

Postoperative thrombotic thrombocytopenic purpura (TTP) shows clinical presentation similar to classical TTP, whereas exact pathophysiological contexts remain unexplained. In this study, we investigated intraoperative and postoperative changes in ADAMTS-13 (a disintegrin and metalloprotease with thrombospondin type 1 motifs, member 13), von Willebrand factor (VWF), large VWF multimers, and interleukin-6 (IL-6) in vascular surgery patients. The objective was to compare the impact of endovascular, peripheral, and aortic surgery on target parameters which are supposed to play a role in surgery-associated TTP. A total of 93 vascular surgery patients were included and divided into 4 groups according to the specific type of intervention they underwent. Blood samples were taken preoperatively, intraoperatively, and postoperatively on days 2 and 4. The ADAMTS-13 activity decreased significantly in 3 of the 4 groups during surgery (from median 81% to 49%, P < .001, in the group undergoing aortoiliacal interventions), whereas the percentage of large VWF multimers increased in all groups of patients. von Willebrand factor antigen increased significantly in all groups on postoperative day 2 and IL-6 increased significantly in the intraoperative and early postoperative period. There was no significant correlation between the intraoperative decrease in ADAMTS-13 and the increase in VWF or IL-6. No patient in this study showed clinical picture of TTP; the precise cause and clinical significance of moderately reduced ADAMTS-13 activity in the perioperative setting have not yet been definitely determined.

Targeting von Willebrand factor in liver diseases: A novel therapeutic strategy?

Acute and chronic liver disease are associated with substantial alterations in the hemostatic system. Evidence from both experimental and clinical studies suggests that anticoagulants slow the progression of liver disease. Efficacy of those anticoagulant drugs is, in part, attributed to a reduction of microthrombi formation within the liver. Although anticoagulant drugs show promising results, bleeding risk associated with these drugs is an obvious drawback, particularly in patients with a complex coagulopathy driven by decreased liver function. Identifying therapies that reduce intrahepatic thrombosis with minimal bleeding risk would significantly advance the field. Among the hemostatic alterations observed in patients are substantially increased levels of the platelet-adhesive protein von Willebrand factor (VWF). In contrast, levels of A Disintegrin and Metalloproteinase with Thrombospondin motifs, the enzyme that regulates VWF activity, are significantly reduced in patients with liver disease. Highly elevated VWF levels are proposed to accelerate intrahepatic thrombus formation and thus be a driver of disease progression. Strong clinical evidence suggesting a link between liver disease and changes in VWF is now being matched by emerging mechanistic data showing a detrimental role for VWF in the progression of liver disease. This review focuses on clinical and experimental evidence supporting a connection between VWF function and the progression of acute and chronic liver diseases. Furthermore, with the recent anticipated approval of several novel therapies targeting VWF, we discuss potential strategies and benefits of targeting VWF as an innovative therapy for patients with liver disease.

Thrombocytopenia and Hemostatic Changes in Acute and Chronic Liver Disease: Pathophysiology, Clinical and Laboratory Features, and Management

Thrombocytopenia, defined as a platelet count <150,000/μL, is the most common complication of advanced liver disease or cirrhosis with an incidence of up to 75%. A decrease in platelet count can be the first presenting sign and tends to be proportionally related to the severity of hepatic failure. The pathophysiology of thrombocytopenia in liver disease is multifactorial, including (i) splenomegaly and subsequently increased splenic sequestration of circulating platelets, (ii) reduced hepatic synthesis of thrombopoietin with missing stimulation both of megakaryocytopoiesis and thrombocytopoiesis, resulting in diminished platelet production and release from the bone marrow, and (iii) increased platelet destruction or consumption. Among these pathologies, the decrease in thrombopoietin synthesis has been identified as a central mechanism. Two newly licensed oral thrombopoietin mimetics/receptor agonists, avatrombopag and lusutrombopag, are now available for targeted treatment of thrombocytopenia in patients with advanced liver disease, who are undergoing invasive procedures. This review summarizes recent advances in the understanding of defective but at low level rebalanced hemostasis in stable cirrhosis, discusses clinical consequences and persistent controversial issues related to the inherent bleeding risk, and is focused on a risk-adapted management of thrombocytopenia in patients with chronic liver disease, including a restrictive transfusion regimen.

Quantification of von Willebrand factor and ADAMTS-13 after traumatic injury: a pilot study

BACKGROUND

Von Willebrand factor (VWF) is an acute phase reactant synthesized in the megakaryocytes and endothelial cells. VWF forms ultra-large multimers (ULVWF) which are cleaved by the metalloprotease ADAMTS-13, preventing spontaneous VWF-platelet interaction. After trauma, ULVWF is released into circulation as part of the acute phase reaction. We hypothesized that trauma patients would have increased levels of VWF and decreased levels of ADAMTS-13 and that these patients would have accelerated thrombin generation.

METHODS

We assessed plasma concentrations of VWF antigen and ADAMTS-13 antigen, the Rapid Enzyme Assays for Autoimmune Diseases (REAADS) activity of VWF, which measure exposure of the platelet-binding A1 domain, and thrombin generation kinetics in 50 samples from 30 trauma patients and an additional 21 samples from volunteers. Samples were analyzed at 0 to 2 hours and at 6 hours from the time of injury. Data are presented as median (IQR) and Kruskal-Wallis test was performed between trauma patients and volunteers at both time points.

RESULTS

REAADS activity was greater in trauma patients than volunteers both at 0 to 2 hours (190.0 (132.0-264.0) vs. 92.0 (71.0-114.0), p<0.002) and at 6 hours (167.5 (108.0-312.5.0) vs. 92.0 (71.0-114.0), p<0.001). ADAMTS-13 antigen levels were also decreased in trauma patients both at 0 to 2 hours (0.84 (0.51-0.94) vs. 1.00 (0.89-1.09), p=0.010) and at 6 hours (0.653 (0.531-0.821) vs. 1.00 (0.89-1.09), p<0.001). Trauma patients had accelerated thrombin generation kinetics, with greater peak height and shorter time to peak than healthy volunteers at both time points.

DISCUSSION

Trauma patients have increased exposure of the VWF A1 domain and decreased levels of ADAMTS-13 compared with healthy volunteers. This suggests that the VWF burst after trauma may exceed the proteolytic capacity of ADAMTS-13, allowing circulating ULVWF multimers to bind platelets, potentially contributing to trauma-induced coagulopathy.

LEVEL OF EVIDENCE

Prospective case cohort study.

Clinical significance of measuring ADAMTS-13, its inhibitor and von Willebrand factor in obstetric and gynecological practice

ADAMTS-13 is a crucial metalloproteinase involved in liberating fragments of von Willebrand factor (vWF) into the plasma as well as regulating its activity by cleaving "ultra-large" multimers into smaller and less active counterparts. Many pathological conditions, including those emerged during pregnancy are characterized by increased level of vWF and decreased ADAMTS-13 activity. In this regard, it is necessary to monitor the levels of vWF and ADAMTS-13 activity to prevent thrombotic thrombocytopenic purpura (Moschcowitz disease) as one of the most severe forms of thrombotic microangiopathy.

 

The heparin-von Willebrand factor interaction and conventional tests of haemostasis - the challenges in predicting bleeding in cardiopulmonary bypass

Bleeding is a significant complication of cardiopulmonary bypass (CPB), despite routine anticoagulation monitoring. This is likely to be multifactorial. In this prospective, single-centre cohort study of 30 patients undergoing CPB surgery, our aim was to characterise the changes in von Willebrand factor (VWF) function, platelet interaction and the global coagulation changes during and after CPB surgery and to determine whether bleeding can be predicted. Samples were taken at six time points before, during and after CPB surgery. We observed a significant rise in VWF antigen (VWF:Ag) throughout surgery, which continued postoperatively. The absolute VWF collagen-binding assays (VWF:CB) and VWF ristocetin cofactor (VWF:RCo) rose significantly but the VWF:CB/VWF:Ag and VWF:Ag/VWF:RCo fell significantly (P = 0·0015 and P = 0·0143), suggesting loss of large multimers. We detected a non-significant trend to loss of VWF:RCo after heparinisation and a significant recovery after protamine reversal which could reflect a direct heparin effect. There was a significant increase in the R and K times with a fall in alpha angle and maximum amplitude after heparin administration, using heparinase-thromboelastography (TEG). The parameters both significantly improved following protamine (P = 0·007 and P = 0·0054). The activated clotting time (ACT) and heparin anti-Xa level correlated poorly; neither predicted clinically significant bleeding. None of these parameters had a relationship with intraoperative blood loss or requirement for blood product replacement.

Rotational thrombelastometry (ROTEM) improves hemostasis assessment compared to conventional coagulation test in ACLF and Non-ACLF patients

Background

Patients with liver cirrhosis typically exhibit abnormal coagulation parameters in conventional coagulation tests (CCTs). Rotational thromboelastometry (ROTEM) is a holistic blood coagulation assay. This method provides an insight into the global hemostatic capabilities and has been suggested to provide a better overview of the coagulation system in liver cirrhosis.

Methods

The goal of this study was to examine hemostasis in patients with stable liver cirrhosis (Non-ACLF) and in acute-on-chronic liver failure (ACLF) by CCT and ROTEM including agreement of both tests and the prospective assessment of test performance based on clinical outcomes in ACLF patients. Therefore, ACLF patients were additionally subgrouped by bleeding events. Fifty-five Non-ACLF patients and twenty-two patients with ACLF were analysed in this prospective cohort study.

Results

Coagulation parameters analysed by CCT were outside the normal range in Non-ACLF and ACLF patients, but were significantly more aberrant in ACLF patients. Non-ACLF patients analysed by ROTEM revealed parameters largely within the normal limits, while significantly more ROTEM parameters in ACLF patients were affected. Maximum clot firmness (MCF) was significantly divergent between both patient groups and correlated well with levels of fibrinogen and platelet count. Using Cohen’s Kappa coefficient κ, the strength of agreement between CCT and ROTEM analyses was determined to be fair for Non-ACLF patients and moderate for ACLF patients. Bleeding events occurred significantly more often in ACLF group with significantly reduced A10 and MCF.

Conclusions

For assessing hemostasis in Non-ACLF and ACLF patients the underlying dataset shows advantages of ROTEM over CCT. A10 and MCF represent suitable prognostic parameters in predicting bleeding events in ACLF group.

Hemostatic Alterations in Patients With Cirrhosis: From Primary Hemostasis to Fibrinolysis

In the setting of liver cirrhosis (LC), profound hemostatic changes occur, which affect primary hemostasis, coagulation, and fibrinolysis. They involve prohemorrhagic and prothrombotic alterations at each of these steps. Patients with cirrhosis exhibit multifactorial thrombocytopenia and in vitro thrombocytopathy, counterbalanced by increased von Willebrand factor. The resultant shift is difficult to assess, but overall these changes probably result in a rebalanced primary hemostasis. Concerning coagulation, the reduced activity of coagulation factors is counterbalanced by an increase in factor VIII (produced by liver sinusoidal endothelial cells), a decrease of the natural anticoagulants, and complex changes, including changes in circulating microparticles, cell-free DNA, and neutrophil extracellular traps. Overall, these alterations result in a procoagulant state. As for fibrinolysis, increased tissue-type and urokinase-type plasminogen activators, a relatively decreased plasminogen activator inhibitor 1, and decreased levels of thrombin-activatable fibrinolysis inhibitor and α2-antiplasmin are counterbalanced by decreased plasminogen and a decreased fibrin clot permeability. Whether and how these changes shift fibrinolysis remains to be determined. Overall, the current consensus is that in patients with cirrhosis, the hemostasis is shifted toward a procoagulant state. We review the published evidence for the concept of LC as a prothrombotic state, discuss discordant data, and highlight the impact of the underlying cause of LC on the resultant imbalance.

Anti-ADAMTS13 autoantibodies in immune-mediated thrombotic thrombocytopenic purpura do not hamper ELISA-based quantification of ADAMTS13 antigen

BACKGROUND

The biological diagnosis of immune-mediated thrombotic thrombocytopenic purpura (iTTP) is based on determination of ADAMTS13 activity (<10%) and anti-ADAMTS13 autoantibodies. ADAMTS13 antigen levels are not routinely measured in iTTP patients, but studies have shown that antigen levels are a valuable prognostic factor.

OBJECTIVES

To (a) report the validation of our in-house developed ADAMTS13 antigen enzyme-linked immunosorbent assay (ELISA) and determine ADAMTS13 antigen in a large cohort of healthy donor and iTTP patient plasma samples; and (b) to investigate whether ADAMTS13 antigen determination is not disturbed by the presence of anti-ADAMTS13 autoantibodies.

METHODS

Our in-house ADAMTS13 antigen ELISA was validated in terms of sensitivity, repeatability, and reproducibility. ADAMTS13 antigen levels were determined in plasma samples from 423 healthy donors and 112 acute iTTP patients. Purified IgGs from iTTP patients were added to normal human plasma to determine whether anti-ADAMTS13 autoantibodies hampered ADAMTS13 antigen determination.

RESULTS

Our in-house ADAMTS13 antigen ELISA has a detection limit of 3% and low intra-assay (coefficient of variation, %CV < 10%) and inter-assay (%CV < 18%) variability. ADAMTS13 antigen levels were significantly reduced (P < .0001) in acute iTTP patients (15 ± 18%) compared to healthy donors (101 ± 18%). The anti-ADAMTS13 autoantibodies in plasma of iTTP patients did not impede ADAMTS13 antigen determinations using our in-house ELISA.

CONCLUSIONS

Our in-house ADAMT13 antigen ELISA is a powerful tool to correctly determine ADAMTS13 antigen levels in iTTP patients, which supports routine ADAMTS13 antigen measurements in these patients to have better insight into disease prognosis.

Levels of TAFI, TFPI and ADAMTS-13 in inflammatory bowel disease

BACKGROUND/AIMS

There is an increased tendency for thrombosis and thromboembolic complications in patients with inflammatory bowel disease (IBD). The aim of the present study was to determine the serum concentrations of thrombin-activatable fibrinolysis inhibitor (TAFI), tissue factor pathway inhibitor (TFPI) and a disintegrin and metalloproteinase with thrombospondin motif-13 (ADAMTS-13) in patients with IBD and to assess their possible role in the etiopathogenesis of the disease.

MATERIALS AND METHODS

Thirty-four patients with IBD (23 ulcerative colitis and 11 Crohn's disease) and 20 healthy controls were included in the present study. TAFI, TFPI, and ADAMTS-13 concentrations were determined by enzyme-linked immunosorbent assay.

RESULTS

Mean TAFI, TFPI, and ADAMTS-13 concentrations in the patient group were 17.75 ng/ml, 72.10 ng/ml, and 14.90 U/l, respectively. In the control group, these values were 117.10 ng/ml, 300 ng/ml, and 191.55 U/l, respectively. TAFI, TFPI, and ADAMTS-13 values were significantly lower in the patient group than in the control group (all p<0.01).

CONCLUSION

TAFI, TFPI, and ADAMTS-13 levels were significantly lower in the patient group. These findings indicate the presence of a clear, multifactorial imbalance in the coagulation-fibrinolytic system in the patient group. It is also possible that this imbalance in the coagulation and fibrinolytic system may play a role in the still unclear etiopathogenesis of the disease.

Liver Diseases and the Hemostasis (Rewiew) Part 1. Non-Cholestatic Diseases of the Liver and Hemostasis

In liver diseases, most commonly in the terminal stage of liver failure, a variety of hemostatic defects affecting almost all parts of the blood coagulation system are developing. This leads to diminishing the capabilities of patients with liver diseases to correctly maintain the hemostatic balance.The severity of hemostatic disorders depends on the nosological form and degree of a liver damage. Depending on the imbalance of the hemostasis system and accumulated clinical/laboratory data, patients with liver diseases can be subdivided into three groups as exhibiting: 1. non-cholestatic liver damage; 2. cholestatic liver damage and 3. liver damage of vascular origin.The first part of the review discusses multiple alterations in the hemostasis system in patients with noncholestatic liver diseases, which are commonly accompanied by hypocoagulation.

Successful plasma exchange in a 34-year-old woman with diabetic ketoacidosis and a thrombotic microangiopathy

Thrombotic microangiopathy (TMA) associated with diabetic ketoacidosis (DKA) is a rare complication reported in the pediatric setting. We report a case of an adult patient with new-onset DM, DKA, and TMA who was treated successfully with therapeutic plasma exchange (TPE). The patient underwent five procedures and experienced quick recovery in her platelet count and a near-normalization of her LDH. Within 3 days, ADAMTS13 activity was reported at 40.7% (>66.8%). After a protracted hospital course, mostly focused on treating the patient's bilateral hemorrhagic chemosis, the patient was discharged on hospital day 30. TMA is associated with a spectrum of diseases such as TTP and sepsis but, to our knowledge, it has not been reported in the setting of DKA in an adult patient. Evidence supports that metabolic alterations associated with DKA and its treatment disrupt basal hemostatic mechanisms and promote a thrombotic state. Although ADAMTS13 activity was only moderately decreased, our patient responded rapidly to TPE, with a striking increase and stabilization of her PLT count that was durable beyond discharge. As reported recently, patients who have TMA with ADAMTS13 activity levels >10% have a range of diagnoses, presentations, and outcomes. Although the underlying microangiopathic process is incompletely understood, these patients may respond well to TPE, as was seen in this case.

Oral Anticoagulation in Patients With Liver Disease

Patients with liver disease are at increased risks of both thrombotic and bleeding complications. Many have atrial fibrillation (AF) or venous thromboembolism (VTE) necessitating oral anticoagulant agents (OACs). Recent evidence has contradicted the assumption that patients with liver disease are "auto-anticoagulated" and thus protected from thrombotic events. Warfarin and non-vitamin K-antagonist OACs have been shown to reduce thrombotic events safely in patients with either AF or VTE. However, patients with liver disease have largely been excluded from trials of OACs. Because all currently approved OACs undergo metabolism in the liver, hepatic dysfunction may cause increased bleeding. Thus, the optimal anticoagulation strategy for patients with AF or VTE who have liver disease remains unclear. This review discusses pharmacokinetic and clinical studies evaluating the efficacy and safety of OACs in patients with liver disease and provides a practical, clinically oriented approach to the management of OAC therapy in this population.

Postsurgical thrombotic microangiopathy: Case series and review of the literature

OBJECTIVES

Describe the clinical presentation, treatment, and outcomes of postsurgical thrombotic microangiopathy (TMA).

METHODS

In this retrospective study, records of individuals diagnosed with TMA developing within 30 days of a surgical procedure at Mayo Clinic from 2000 to 2016 were reviewed. Available literature regarding postsurgical TMA was comparatively reviewed.

RESULTS

Twenty patients were diagnosed with TMA developing within 30 (median 6.5, range (1-28)) days) following a procedure. Preceding procedures included orthopedic (n = 4), vascular (n = 4), abdominal (n = 8), thoracic (n = 2), and other (n = 2). Review of the literature identified 65 patients with postsurgical TMA and cardiovascular procedures were the most common preceding surgery. The majority of patients in the current cohort and literature were treated with therapeutic plasma exchange (TPE). Among the evaluable patients in the current cohort, 100% demonstrated response to TPE; however, 25% required the addition of other therapy including eculizumab to maintain a response 80% of patients in the literature demonstrated a response to TPE.

CONCLUSIONS

Although rare, early recognition and treatment of postsurgical TMA can lead to good outcomes. More research is necessary to determine the underlying pathophysiology and optimal treatment for postsurgical TMA.

von Willebrand factor/ADAMTS-13 interactions at birth: implications for thrombosis in the neonatal period

von Willebrand factor (VWF) and its cleaving protease ADAMTS-13 (A Disintegrin and Metalloproteinase with Thrombospondin type 1 motif, member 13) are essential components to hemostasis. These plasma proteins have also been implicated in a number of disease states, including those affecting children. The best described abnormality is the congenital form of thrombotic thrombocytopenic purpura (TTP) resulting from germline mutations in the ADAMTS-13 gene. The VWF/ADAMTS-13 interaction has more recently emerged as a causative risk factor in the pathogenesis of pediatric stroke and secondary microangiopathies. There is now increasing interest and need to measure these coagulation factors during the neonatal period and throughout childhood. Methods adopted from a multitude of technically diverging studies have been used to understand their role during this period. To date, studies of VWF/ADAMTS-13 in this group of patients have reported conflicting results, which makes interpreting values in the clinical setting especially challenging. In this review we describe the historical evolution of the methodology used to measure VWF/ADAMTS-13 and how it may influence the results obtained during the first days of life. We review the individual assays used to analyze VWF/ADAMTS-13 as well as published reference values. Finally, we bring attention to the potential pathophysiologic role of VWF/ADAMTS-13 in neonatal thrombosis. This has significant implications because the pathologic processes that explain thrombosis in neonates remain poorly characterized and thromboembolism remains a significant source of morbidity and mortality, particularly in sick children.

Thrombotic microangiopathy in a very young infant with mitral valvuloplasty

BACKGROUND

Thrombotic microangiopathies (TMA) are microvascular occlusive disorders characterized by systemic or intrarenal platelet aggregation, thrombocytopenia, and red cell fragmentation. Post-operative TMA mostly occurs in adult patients with cardiovascular surgery, with the distinct pathophysiology from classical thrombotic thrombocytopenic purpura (TTP) although the exact pathophysiology remains unclear.

CASE PRESENTATION

A one-month-old infant developed TMA after the initial surgery of double outlet right ventricle. ADAM metallopeptidase with thrombospondin type 1 motif 13 (ADAMTS13) activity was sustained (64%) with the undetectable inhibitor. Von Willebrand factor (VWF) multimer analyses showed absent high-molecular weight multimers. Echocardiography disclosed severe mitral regurgitation. The mitral valve repair 32 days after the initial valvuloplasty led to prompt resolution of TMA. These suggested that TMA occurred in association with valvulopathy-triggered turbulent shear flow, mechanical hemolysis and endothelial damage. The consumption of large VWF multimers might account for the vascular high shear stress shown in Heyde syndrome.

CONCLUSION

The youngest case of post-operative TMA underscores the critical coagulopathy after the first surgical intervention for congenital heart disease.

Elevated ADAMTS13 Activity is Associated with Poor Postoperative Outcome in Patients Undergoing Liver Resection

Recently, von-Willebrand-Factor (vWF) has been shown to correlate with postoperative liver dysfunction (LD). Accordingly, “disintegrin-like metalloprotease with thrombospondin type1 motif” (ADAMTS13) is known to cleave vWF in less active fragments. Thus, we aimed to evaluate the diagnostic potential of ADAMTS13-activity (ADAMTS13-AC) to identify patients with postoperative LD after hepatectomy. Accordingly 37 patients undergoing hepatectomy for different neoplastic entities were included in this study. Plasma ADAMTS13-AC and vWF-Ag were measured 1 day prior to (preOP), 1 and 5 days (POD1/5) after hepatectomy. In accordance to the ISGLS-criteria LD was prospectively recorded. In this context, perioperative ADAMTS13-AC- and vWF-Ag/ADAMTS13-AC-ratio- levels revealed a significant increase after hepatectomy. Accordingly, elevated vWF-Ag/ADAMTS13-AC-ratio significantly predicted LD (preOP AUC: 0.75, p = 0.02; POD1 AUC: 0.80, p = 0.03). Patients who fulfilled our perioperative vWF-Ag/ADAMTS13-AC-ratio cut-off-levels (preOP: ≥116, POD1: ≥165) suffered from significantly higher incidences of LD (preOP: 70% vs. 30%, p = 0.01; POD1: 83% vs. 17%, p = 0.001). In conclusion, perioperative ADAMTS13-AC measurement may serve as a useful parameter to early detect high-risk patients developing postoperative LD prior to liver resection in patients suffering from hepatic malignancies. Indeed, further investigations have to be performed to consolidate its role as a predictive marker for LD.

Major Changes of von Willebrand Factor Multimer Distribution in Cirrhotic Patients with Stable Disease or Acute Decompensation

Background  There is an unstable balance between pro- and anti-haemostatic processes in patients with cirrhosis. We hypothesized, that in patients with acute decompensation (AD) the major alterations of von Willebrand factor (VWF) could contribute to the pro-thrombotic situation as compared to patients with stable (ST) cirrhosis.

Patients and Methods  We analysed different parameters of VWF, including detailed multimer distribution by densitometry and platelet adhesion, together with ad isintegrin-like a nd m etalloproteinase with t hrombo s pondin type-1 motifs 13 (ADAMTS13) activity and antigen and C-reactive protein (CRP) levels in patients with ST cirrhosis ( n  = 99), with AD ( n  = 54) and controls ( n  = 92).

Results  VWF antigen, ristocetin co-factor as well as collagen-binding activities were elevated in both cirrhotic groups in a stepwise manner. There was a decrease in high and an increase in low molecular weight multimer ratios in the majority of ST cirrhosis. However, in 24 out of 54 AD patients, ultra-large VWF multimers (ultra-large molecular weight multimers [ULMWM]) were found. ADAMTS13 activity in ST and AD patients without ULMWM was similar to controls (median [interquartile range; IQR]%: 98 [67–132] and 91 [60–110] vs. 106 [88–117], respectively). The presence of ULMWM in AD patients was associated with low ADAMTS13 activity [33 (24–49)%] and high CRP level [23 (7.1–83.6) mg/L]. Adhesion of normal platelets showed a stepwise increase in the presence of cirrhotic plasmas, reaching the highest level in AD patients with ULMWM.

Conclusion  Characteristic changes of VWF parameters are seen in ST cirrhosis. In AD patients, highly increased VWF and reduced ADAMTS13 activity could be found, along with the presence of ULMWM, which are possible markers and contributors of the disease progression.

ADAMTS proteins in human disorders

ADAMTS proteins are a superfamily of 26 secreted molecules comprising two related, but distinct families. ADAMTS proteases are zinc metalloendopeptidases, most of whose substrates are extracellular matrix (ECM) components, whereas ADAMTS-like proteins lack a metalloprotease domain, reside in the ECM and have regulatory roles vis-à-vis ECM assembly and/or ADAMTS activity. Evolutionary conservation and expansion of ADAMTS proteins in mammals is suggestive of crucial embryologic or physiological roles in humans. Indeed, Mendelian disorders or birth defects resulting from naturally occurring ADAMTS2, ADAMTS3, ADAMTS10, ADAMTS13, ADAMTS17, ADAMTS20, ADAMTSL2 and ADAMTSL4 mutations as well as numerous phenotypes identified in genetically engineered mice have revealed ADAMTS participation in major biological pathways. Important roles have been identified in a few acquired conditions. ADAMTS5 is unequivocally implicated in pathogenesis of osteoarthritis via degradation of aggrecan, a major structural proteoglycan in cartilage. ADAMTS7 is strongly associated with coronary artery disease and promotes atherosclerosis. Autoantibodies to ADAMTS13 lead to a platelet coagulopathy, thrombotic thrombocytopenic purpura, which is similar to that resulting from ADAMTS13 mutations. ADAMTS proteins have numerous potential connections to other human disorders that were identified by genome-wide association studies. Here, we review inherited and acquired human disorders in which ADAMTS proteins participate, and discuss progress and prospects in therapeutics.

Intensive Care Management of Patients with Cirrhosis

PURPOSE OF REVIEW

Cirrhosis is a major worldwide health problem which results in a high level of morbidity and mortality. Patients with cirrhosis who require intensive care support have high mortality rates of near 50%. The goal of this review is to address the management of common complications of cirrhosis in the ICU.

RECENT FINDINGS

Recent epidemiological studies have shown an increase in hospitalizations due to advanced liver disease with an associated increase in intensive care utilization. Given an increasing burden on the healthcare system, it is imperative that we strive to improve our management cirrhotic patients in the intensive care unit. Large studies evaluating the management of patients in the intensive care setting are lacking. To date, most recommendations are based on extrapolation of data from studies in cirrhosis outside of the ICU or by applying general critical care principles which may or may not be appropriate for the critically ill cirrhotic patient. Future research is required to answer important management questions.

Thrombocytopenia in hospitalized patients: approach to the patient with thrombotic microangiopathy

Thrombotic microangiopathies (TMAs), specifically, thrombotic thrombocytopenic purpura (TTP) and complement-mediated hemolytic uremic syndrome (CM-HUS) are acute life-threatening disorders that require prompt consideration, diagnosis, and treatment to improve the high inherent mortality and morbidity. Presentation is with microangiopathic hemolytic anemia and thrombocytopenia (MAHAT) and variable organ symptoms resulting from microvascular thrombi. Neurological and cardiac involvement is most common in TTP and associated with poorer prognosis and primarily renal involvement in CM-HUS. TTP is confirmed by severe ADAMTS13 deficiency (which can be undertaken in real time) and CM-HUS by an abnormality in complement regulators, confirmed by mutational analysis (in 60% to 70% of cases) or the presence of Factor H antibodies (which may not be available for weeks or months). Plasma exchange (PEX) should be started as soon as possible following consideration of these TMAs. Differentiation of the diagnosis requires specific treatment pathways thereafter (immunosuppression primarily for TTP and complement inhibitor therapy for CM-HUS). As the diagnosis is based on MAHAT, there are a number of other medical situations that need to be excluded and these are discussed within the article. Other differentials presenting as TMAs may also be associated with micro- or macrovascular thrombosis, yet are more likely to be due to direct endothelial damage, many of which do not have a clear therapeutic benefit with PEX.

Elevated preoperative von Willebrand factor is associated with perioperative thrombosis in infants and neonates with congenital heart disease

Essentials Perioperative thrombosis is a major cause of morbidity and mortality in congenital heart disease. Neonates and infants undergoing repair of congenital heart lesions were prospectively followed. Elevated von Willebrand factor (VWF) to ADAMTS-13 activity ratios typified the postoperative period. Thrombosis was associated with preoperative VWF activity and cryoprecipitate transfusion SUMMARY: Background The surgical repair of congenital heart malformations is frequently complicated by perioperative thrombosis of unclear etiology. An imbalance between von Willebrand factor (VWF) and ADAMTS-13 is an emerging variable in thrombosis. Objectives To describe perioperative changes to VWF, ADAMTS-13 and NETosis, and evaluate clinical and biochemical associations with postoperative thrombosis. Methods Neonates and infants undergoing palliation or definitive surgical repair of congenital heart malformations were recruited (n = 133). Preoperative and postoperative plasma levels of VWF, ADAMTS-13 and markers of NETosis were determined. Patients were followed for up to 30 days for the occurrence of thrombosis. Univariate and multivariate logistic regression analyses were conducted to identify variables associated with thrombosis. Results We identified significant postoperative increases in VWF activity, VWF level, DNA-histone complexes and cell-free DNA with an overall decrease in ADAMTS-13 activity. Patients experiencing postoperative thrombotic events (9%) were characterized by surgery performed at a lower intraoperative temperature, higher preoperative lactic acid levels, and higher preoperative VWF activity and level. A multivariate logistic regression model identified preoperative VWF activity (odds ratio (OR) 8.39 per IU mL-1 , 95% confidence interval [CI] 1.73-40.55) and transfusion of cryoprecipitate (OR 1.10 per mL kg-1 , 95% CI 1.03-1.17) as being associated with thrombosis. Conclusions Pediatric patients undergoing surgical repair of congenital heart malformations are exposed to high levels of VWF with diminished or minimal change to ADAMTS-13 in the immediate postoperative period. Elevated preoperative VWF activity is associated with postoperative thrombosis in pediatric congenital heart disease.

Uncertain thrombophilia markers

The development of venous thromboembolism (VTE), which includes deep-vein thrombosis and pulmonary embolism, may be associated with inherited or acquired risk factors that can be measured in plasma or DNA testing. The main inherited thrombophilias include the plasma deficiencies of the natural anticoagulants antithrombin, protein C and S; the gain-of-function mutations factor V Leiden and prothrombin G20210A; some dysfibrinogenaemias and high plasma levels of coagulation factor VIII. Besides these established biomarkers, which usually represent the first-level laboratory tests for thrombophilia screening, a number of additional abnormalities have been less consistently associated with an increased VTE risk. These uncertain causes of thrombophilias will be discussed in this narrative review, focusing on their clinical impact and the underlying pathogenetic mechanisms. Currently, there is insufficient ground to recommend their inclusion within the framework of conventional thrombophilia testing.

Expression of ADAMTS13 in Normal and Abnormal Placentae and Its Potential Role in Angiogenesis and Placenta Development

OBJECTIVE

ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 repeats, member 13) is primarily synthesized in liver. The biosynthesis of ADAMTS13 and its physiological role in placenta are not known.

APPROACH AND RESULTS

We used real-time polymerase chain reaction, immunohistochemistry, and Western blotting analyses, as well as proteolytic cleavage of FRETS (fluorescent resonance energy transfers)-VWF73, to determine ADAMTS13 expression in placenta and trophoblasts obtained from individuals with normal pregnancy and patients with severe preeclampsia. We also determined the role of ADAMTS13 in extravillous trophoblasts using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, wound scratch assay, transwell migration assay, tube formation assay, and tissue outgrowth assays. We showed that full-length and proteolytically active ADAMTS13 was expressed in normal human placenta, primarily in the trophoblasts and villous core fetal vessel endothelium during pregnancy. Placental expression of ADAMTS13 mRNA, protein, and proteolytic activity was at the highest levels during the first trimester and significantly reduced at the term of gestation. Additionally, significantly reduced levels of placental ADAMTS13 expression was detected under hypoxic conditions and in patients with preeclampsia. In addition, recombinant ADAMTS13 protease stimulated proliferation, migration, invasion, and network formation of trophoblastic cells in culture. Finally, knockdown of ADAMTS13 expression attenuated the ability of tube formation in trophoblast (HTR-8/SVNEO) cells and the extravillous trophoblast outgrowth in placental explants.

CONCLUSIONS

Our results demonstrate for the first time the expression of ADAMTS13 mRNA and protein in normal and abnormal placental tissues and its role in promoting angiogenesis and trophoblastic cell development. The findings support the potential role of the ADAMTS13-von Willebrand factor pathway in normal pregnancy and pathogenesis of preeclampsia.

Levels and activities of von Willebrand factor and metalloproteinase with thrombospondin type-1 motif, number 13 in inflammatory bowel diseases

AIM

To evaluate the levels of von Willebrand factor (VWF) and metalloproteinase with thrombospondin type-1 motif, number 13 (ADAMTS13) in inflammatory bowel disease (IBD) and correlate them with the disease activity.

METHODS

Consecutive patients with IBD aged 18 years or older were enrolled in the study. Forty-seven patients with ulcerative colitis (UC), 38 with Crohn’s disease (CD), and 50 healthy controls were included. The white blood cell count, haematocrit, platelet count, fibrinogen, partial activated thromboplastin time, C-reactive protein, albumin, VWF antigen level (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), VWF collagen-binding activity (VWF:CB), and ADAMTS13 antigen level (ADAMTS13:Ag) and activity (ADAMTS13act) were measured. The following ratios were assessed: VWF:RCo/VWF:Ag, VWF:CB/VWF:Ag, VWF:Ag/ADAMTS13act, and ADAMTS13act/ADAMTS13:Ag.

RESULTS

Compared to controls, the odds ratio (OR) of an elevated VWF: Ag > 150% was 8.7 (95%CI: 2.7-28.1) in the UC group and 16.2 (95%CI: 4.8-54.0) in the CD group. VWF:CB was lower in UC patients, and active CD was associated with a higher VWF: RCo (+38%). The ORs of VWF:CB/VWF:Ag < 0.7 (a marker of acquired von Willebrand syndrome) in the UC and CD groups were 11.9 (95%CI: 4.4-32.4) and 13.3 (95%CI: 4.6-38.1), respectively. Active UC was associated with lower ADAMTS13:Ag (-23%) and ADAMTS13act (-20%) compared to UC in remission. Patients with active CD had a 15% lower ADAMTS13act than controls. The activity of UC, but not that of CD, was inversely correlated with ADAMTS13:Ag (r = -0.76) and ADAMTS13act (r = -0.81).

CONCLUSION

Complex VWF-ADAMTS13-mediated mechanisms disturb haemostasis in IBD. A reduced WVF:CB is a risk factor for bleeding, while a lower ADAMTS13 level combined with an elevated VWF:Ag could predispose one to thrombosis.

ADAMTS13 Deficiency Worsens Colitis and Exogenous ADAMTS13 Administration Decreases Colitis Severity in Mice

Background  Inflammatory bowel disease (IBD) affects 1.6 million people in the United States. IBD is associated with an increased risk of thrombosis, which rises with disease activity. The pathogenesis of IBD and its increased thrombotic risk is not completely understood. Ultra large von Willebrand factor (ULVWF) multimers are secreted from activated endothelium, leading to recruitment of platelets and leukocytes. A disintegrin and metalloproteinase with thrombospondin type I repeats motif 13 (ADAMTS13) cleaves highly adhesive ULVWF into smaller, less bioactive, multimers, releasing them into circulation. Mice deficient in ADAMTS13 (ADAMTS13 ^−/− ) have heightened inflammatory and thrombotic responses.

Objectives  We hypothesized that upon colitis induction, ADAMTS13 ^−/− mice would have more severe symptoms compared with wild-type (WT) mice, and rhADAMTS13 administration to mice with colitis would improve their condition.

Results  Dextran sodium sulfate–induced colitis was worse in ADAMTS13 ^−/− mice than WT. ADAMTS13 ^−/− showed increased weight loss, worse anemia, and increased clinical and histologic colitis severity, compared with WT mice. ADAMTS13 ^−/− mice had increased VWF release, with accumulation at inflamed colonic sites. Also, the majority of mice showed one or more submucosal colonic thrombi. ADAMTS13 deficiency worsened colitis and propagated intestinal inflammation, most likely through increased platelet–leukocyte recruitment by VWF. Treatment of WT mice with rhADAMTS13 decreased colitis severity without worsening anemia. Additionally, several immune-mediated chronic murine colitis models, and inflamed colon tissue specimens from IBD patients, showed increased VWF release at inflamed sites, suggesting a generalizability of our findings.

Conclusion  Measuring VWF/ADAMTS13 levels could have clinical utility. When applicable, the administration of ADAMTS13, in addition to primary treatment, may improve outcomes for IBD patients.

Thromboelastometry: Relation to the severity of liver cirrhosis in patients considered for liver transplantation

The severity of liver disease is assessed by scoring systems, which include the conventional coagulation test prothrombin time-the international normalized ratio (PT-INR). However, PT-INR is not predictive of bleeding in liver disease and thromboelastometry (ROTEM) has been suggested to give a better overview of the coagulation system in these patients. It has now been suggested that coagulation as reflected by tromboelastomety may also be used for prognostic purposes. The objective of our study was to investigate whether thrombelastometry may discriminate the degree of liver insufficiency according to the scoring systems Child Pugh and Model for End-stage Liver Disease (MELD).Forty patients with chronic liver disease of different etiologies and stages were included in this observational cross-sectional study. The severity of liver disease was evaluated using the Child-Pugh score and the MELD score, and blood samples for biochemistry, conventional coagulation tests, and ROTEM were collected at the time of the final assessment for liver transplantation. Statistical comparisons for the studied parameters with scores of severity were made using Spearman correlation test and receiver-operating characteristic (ROC) curves.Spearman correlation coefficients indicated that the thromboelastometric parameters did not correlate with Child-Pugh or MELD scores. The ROC curves of the thromboelastometric parameters could not differentiate advanced stages from early stages of liver cirrhosis.Standard ROTEM cannot discriminate the stage of chronic liver disease in patients with severe chronic liver disease.