Resonant Acoustic Rheometry to Measure Coagulation Kinetics in Hemophilia A and Healthy Plasma: A Novel Viscoelastic Method.

Compared with conventional coagulation tests and factor-specific assays, viscoelastic hemostatic assays (VHAs) can provide a more thorough evaluation of clot formation and lysis but have several limitations including clot deformation. In this proof-of-concept study, we test a noncontact technique, termed resonant acoustic rheometry (RAR), for measuring the kinetics of human plasma coagulation. Specifically, RAR utilizes a dual-mode ultrasound technique to induce and detect surface oscillation of blood samples without direct physical contact and measures the resonant frequency of the surface oscillation over time, which is reflective of the viscoelasticity of the sample. Analysis of RAR results of normal plasma allowed defining a set of parameters for quantifying coagulation. RAR detected a flat-line tracing of resonant frequency in hemophilia A plasma that was corrected with the addition of tissue factor. Our RAR results captured the kinetics of plasma coagulation and the newly defined RAR parameters correlated with increasing tissue factor concentration in both healthy and hemophilia A plasma. These findings demonstrate the feasibility of RAR as a novel approach for VHA, providing the foundation for future studies to compare RAR parameters to conventional coagulation tests, factor-specific assays, and VHA parameters.

Nonhematologic and Hematologic Factors in Spontaneous Intracerebral Hemorrhage.

Spontaneous intracerebral hemorrhage is defined as nontraumatic bleeding into the brain without vascular malformations or presence of tumor. It occurs in about a third of all strokes and has a high mortality and morbidity. Risk factors that determine the outcome are incompletely understood. Known factors include older age, male gender, Asian ethnicity, hypertension, and comorbidity such as inherited or acquired bleeding diathesis and use of antithrombotic drugs. Likewise, the clinical characteristics of the hematoma such as location and volume of the hematoma and other imaging features are also important. Hematoma extension or expansion is a complication with an unfavorable outcome. Recognition of risk factors for hematoma expansion and measures to prevent it, such as blood pressure lowering, will improve the outcome. Enhanced diagnostic methods, especially in imaging techniques developed over the past decade, have not only led to a better understanding of the pathophysiology of spontaneous intracerebral hemorrhage but also of the factors that influence hematoma expansion. An improved knowledge is essential to better management, minimizing hematoma expansion and leading to a healthier outcome.

The Choice between Plasma-Based Common Coagulation Tests and Cell-Based Viscoelastic Tests in Monitoring Hemostatic Competence: Not an either-or Proposition.

There has been a significant interest in the last decade in the use of viscoelastic tests (VETs) to determine the hemostatic competence of bleeding patients. Previously, common coagulation tests (CCTs) such as the prothrombin time (PT) and partial thromboplastin time (PTT) were used to assist in the guidance of blood component and hemostatic adjunctive therapy for these patients. However, the experience of decades of VET use in liver failure with transplantation, cardiac surgery, and trauma has now spread to obstetrical hemorrhage and congenital and acquired coagulopathies. Since CCTs measure only 5 to 10% of the lifespan of a clot, these assays have been found to be of limited use for acute surgical and medical conditions, whereby rapid results are required. However, there are medical indications for the PT/PTT that cannot be supplanted by VETs. Therefore, the choice of whether to use a CCT or a VET to guide blood component therapy or hemostatic adjunctive therapy may often require consideration of both methodologies. In this review, we provide examples of the relative indications for CCTs and VETs in monitoring hemostatic competence of bleeding patients.

Relative Hypercoagulopathy of the SARS-CoV-2 Beta and Delta Variants when Compared to the Less Severe Omicron Variants Is Related to TEG Parameters, the Extent of Fibrin Amyloid Microclots, and the Severity of Clinical Illness.

Earlier variants of SARS-CoV-2 have been associated with hypercoagulability and an extensive formation of fibrin amyloid microclots, which are considered to contribute to the pathology of the coronavirus 2019 disease (COVID-19). The newer omicron variants appear to be far more transmissible, but less virulent, even when taking immunity acquired from previous infections or vaccination into account. We here show that while the clotting parameters associated with omicron variants are significantly raised over those of healthy, matched controls, they are raised to levels significantly lower than those seen with more severe variants such as beta and delta. We also observed that individuals infected with omicron variants manifested less extensive microclot formation in platelet-poor plasma compared with those harboring the more virulent variants. The measurement of clotting effects between the different variants acts as a kind of "internal control" that demonstrates the relationship between the extent of coagulopathies and the virulence of the variant of interest. This adds to the evidence that microclots may play an important role in reflecting the severity of symptoms observed in COVID-19.

The Role of Fibrinolytic System in Health and Disease.

The fibrinolytic system is composed of the protease plasmin, its precursor plasminogen and their respective activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), counteracted by their inhibitors, plasminogen activator inhibitor type 1 (PAI-1), plasminogen activator inhibitor type 2 (PAI-2), protein C inhibitor (PCI), thrombin activable fibrinolysis inhibitor (TAFI), protease nexin 1 (PN-1) and neuroserpin. The action of plasmin is counteracted by α2-antiplasmin, α2-macroglobulin, TAFI, and other serine protease inhibitors (antithrombin and α2-antitrypsin) and PN-1 (protease nexin 1). These components are essential regulators of many physiologic processes. They are also involved in the pathogenesis of many disorders. Recent advancements in our understanding of these processes enable the opportunity of drug development in treating many of these disorders.

The Central Role of Fibrinolytic Response in COVID-19-A Hematologist's Perspective.

The novel coronavirus disease (COVID-19) has many characteristics common to those in two other coronavirus acute respiratory diseases, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). They are all highly contagious and have severe pulmonary complications. Clinically, patients with COVID-19 run a rapidly progressive course of an acute respiratory tract infection with fever, sore throat, cough, headache and fatigue, complicated by severe pneumonia often leading to acute respiratory distress syndrome (ARDS). The infection also involves other organs throughout the body. In all three viral illnesses, the fibrinolytic system plays an active role in each phase of the pathogenesis. During transmission, the renin-aldosterone-angiotensin-system (RAAS) is involved with the spike protein of SARS-CoV-2, attaching to its natural receptor angiotensin-converting enzyme 2 (ACE 2) in host cells. Both tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) are closely linked to the RAAS. In lesions in the lung, kidney and other organs, the two plasminogen activators urokinase-type plasminogen activator (uPA) and tissue plasminogen activator (tPA), along with their inhibitor, plasminogen activator 1 (PAI-1), are involved. The altered fibrinolytic balance enables the development of a hypercoagulable state. In this article, evidence for the central role of fibrinolysis is reviewed, and the possible drug targets at multiple sites in the fibrinolytic pathways are discussed.

The Central Role of Fibrinolytic Response in Trauma-Induced Coagulopathy: A Hematologist's Perspective.

Severe trauma is the leading cause of death globally. Though improved resuscitation, particularly early initiation, has reduced the 24-hour mortality rate, the overall morbidity and 30-day mortality remain high mostly due to massive hemorrhage and head injury in the early stages and sepsis and multiorgan failure later on. With recent clinical trials of antifibrinolytic treatment with tranexamic acid, and with the observations that fibrinolytic activity varies widely among the injured patients, the role of the fibrinolytic system in trauma has become a major focus of investigations in trauma-induced coagulopathy. Most of the body's response to trauma involves the endothelium, tissue factor release, and platelet activation. In addition, there are inflammatory and immune responses. All these events directly or indirectly affect the fibrinolytic system. A full understanding of these mechanisms has translational implications on the management of these patients. In this article, the multifaceted responses of fibrinolysis following injury are reviewed.

Passive Immunity for Coronavirus Disease 2019: A Commentary on Therapeutic Aspects Including Convalescent Plasma.

In the ongoing pandemic of coronavirus disease 2019 (COVID-19), the novel virus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is infecting a naïve population. The innate immunity of the infected patient is unable to mount an effective defense, resulting in a severe illness with substantial morbidity and mortality. As most treatment modalities including antivirals and anti-inflammatory agents are mostly ineffective, an immunological approach is needed. The mechanism of innate immunity to this viral illness is not fully understood. Passive immunity becomes an important avenue for the management of these patients. In this article, the immune responses of COVID-19 patients are reviewed. As SARS-CoV-2 has many characteristics in common with two other viruses, SARS-CoV that cause severe acute respiratory syndrome (SARS) and MERS-CoV (Middle East respiratory syndrome coronavirus) that causes Middle East respiratory syndrome (MERS), the experiences learned from the use of passive immunity in treatment can be applied to COVID-19. The immune response includes the appearance of immunoglobulin M followed by immunoglobulin G and neutralizing antibodies. Convalescent plasma obtained from patients recovered from the illness with high titers of neutralizing antibodies was successful in treating many COVID-19 patients. The factors that determine responses as compared with those seen in SARS and MERS are also reviewed. As there are no approved vaccines against all three viruses, it remains a challenge in the ongoing development for an effective vaccine for COVID-19.

Whole Blood for Civilian Urban Trauma Resuscitation: Historical, Present, and Future Considerations.

Whole blood (WB) has been used for more than a century for far-forward combat resuscitation. Following the Iraq/Afghanistan combat, maritime, and austere environment use of WB for the resuscitation of severely hemorrhaging patients, there has been an increasing use of WB for the civilian urban resuscitation environment population. The impetus for this was not just improved outcomes in far-forward hospitals, which had different populations and different needs than the civilian urban population, but also an application of the lessons suggested by recent 1:1:1 plasma:platelets:packed red cells fixed-ratio studies for patients with massive transfusion needs. Mechanistic, logistic, and standardization concerns have been addressed and are evolving as the WB project advances. A small number of studies have been published on WB in the civilian urban trauma population. In addition, European experience with viscoelastic testing and resuscitation with fibrinogen and prothrombin complex concentrate has provided another viewpoint regarding the choice of resuscitation strategies for severely bleeding trauma patients in urban civilian environments. There are randomized controlled trials in process, which are testing the hypothesis that WB may be beneficial for the civilian urban population. Whether WB will improve mortality significantly is now a matter of intense study, and this commentary reviews the history, mechanistic foundations, and logistical aspects for the use of WB in the civilian trauma population.

Fibrin and Fibrinolysis in Cancer.

In 1878, Billroth discovered that tumor cells invest themselves in a fibrin thrombus, and he hypothesized that fibrin promotes tumor growth and invasion. Since then, many observations have supported this concept, showing that many hemostatic factors including fibrinogen, fibrin, and components of the fibrinolytic system have indeed a complex interaction with cancer growth and metastasis. Fibrin promotes cell migration by providing a matrix for tumor cell migration and by interactions with adhesive molecules and integrins. Fibrin-containing vascular endothelial growth factor promotes angiogenesis. Fibrin interacts with platelets and leukocytes, and promotes their respective carcinogenic properties. Fibrinolytic components exert different effects on tumors. Plasmin activates latent growth factors, and breaks down extracellular matrix (ECM), while urokinase plasminogen activator (uPA) and the uPA receptor (uPAR) form complexes with vitronectin and integrins to promote tumor cells to adhere to the ECM. This complex also binds the epidermal growth factor receptor on the tumor cell membrane, and signals the RAF-MEK-ERK pathway. The complex also binds to the G protein-coupled receptors leading to cell proliferation. Plasminogen activator inhibitor 1 (PAI-1) inhibits apoptosis, and increases tumor cell survival. PAI-1 also enhances cell senescence, leading to production of tumorigenic cytokines by the senescence secretome. The presence of uPA/uPAR and PAI-1 represents a strong biomarker for tumor aggressiveness and poor prognosis. Multiple attempts by blocking various carcinogenic steps have shown tumor-suppressing effects in experimental animals, but human responses are uncertain without clinical trials.

The Role of Abnormal Hemostasis and Fibrinolysis in Morbidity and Mortality of Acute Promyelocytic Leukemia.

Despite the improved therapeutic advances in the management of acute promyelocytic leukemia (APL), a significant early mortality during induction, also referred to as early death (ED), remains an obstacle for further improvement in outcome. Hemorrhagic complications are the most common cause of morbidity and mortality. Perturbed hemostatic dysfunction is present as the result of abnormalities in both the coagulation and the fibrinolytic systems. The activation of coagulation is distinct from the classical disseminated intravascular coagulation. Multiple abnormalities in the fibrinolytic system have recently been identified. The most significant change is increased production of tissue plasminogen activator (tPA) and its receptor annexin A2 by the APL promyelocytes. Among the hemorrhagic complications, intracranial hemorrhage predominates. The pathogenesis of this catastrophic event is elucidated by new evidence of adverse effect of tissue plasminogen activator (tPA) on the brain, including both the plasmin-dependent and plasmin-independent pathways. In order to address the hemorrhagic complications, a thorough understanding of the hemostatic dysfunction is essential. In this article, our current concept of the abnormal hemostasis in APL is reviewed. The failure to reduce the early death rate, despite the introduction of effective therapy, will also be discussed.

Complications of Implanted Nonbiologic Devices-An Overview.

Under physiologic conditions, blood is contained within the vascular space lined with smooth endothelial cells. When various devices made of nonbiologic material are implanted, blood will be exposed to a foreign surface. A series of events ensue and may lead to many complications, including thrombosis, hemolysis, thrombocytopenia, bleeding, infection, and malfunction of the device. The incidence, manifestations, and special characteristics of these complications vary with different types of implanted devices. However, they have in common an important pathogenic pathway that of an exposure to a foreign surface. Despite the development of improved versions of these devices, more research on the causative factors of these complications is needed to take preventive and corrective measures, particularly those that enhance the process of healing by re-endothelialization of the foreign surface. This article is a brief review of the complications encountered in blood-contacting devices.

Microparticles and Fibrinolysis.

Microparticles (MPs) are submicronic vesicles which are formed by budding of the cellular membrane of virtually any cell type in response to cell activation or apoptosis. Both circulating MPs and MPs generated within tissues harbor molecules with a large repertoire of biological activities and transfer material to target cells. Depending on their cellular origin, the stimuli triggering their formation, or their localization, they may participate in the maintenance of organ or vascular homeostasis as well as inducing dysfunction. MPs have mostly been described as having procoagulant properties. However, the fact that some MP subsets are able to efficiently generate plasmin suggests that the role of MPs in hemostasis is more complex than initially thought. In this review, we summarize key findings showing that MPs provide a heterogeneous catalytic surface for plasmin generation, according to their cellular origin. We further address the specific features of the MP-dependent fibrinolytic system. Potential consequences of this MP-associated fibrinolytic activity in pathology are illustrated in cancer.

Risk Factors, Diagnosis, Management, and Outcome of Splanchnic Vein Thrombosis: A Retrospective Analysis.

OBJECTIVES: This study aims to determine the risk factors, diagnostic methods employed, treatment modalities, and outcome in patients with splanchnic vein thrombosis (SVT). METHODS: A retrospective chart review of patients, age 18 to 90 years, diagnosed with SVT at a single institution from January 1, 2010 to November 10, 2012. They were grouped as portal vein thrombosis (PVT)-including those combined with splenic vein thrombosis (SPVT) or mesenteric vein thrombosis (MVT)-and Budd-Chiari syndrome (BCS). RESULTS: Overall 246 SVT patients were identified, including 225 PVT and 21 BCS. Risk factors were liver disease, upper abdominal (regional) cancer and surgery, pancreatitis, and hereditary thrombophilia. The most common symptom was abdominal pain and most patients had abnormal liver function. Among those tested, the JAK2 V617F mutation was present in only 20% of the patients with PVT and 14% of the patients with BCS. Most patients were diagnosed by computed tomography. Anticoagulants were given to 30% of the patients with PVT and to 60% of the patients with BCS, with recurrence of SVT in 15% of the patients with PVT and 24% of the patients with BCS, regardless of anticoagulation. CONCLUSION: As compared with published literature on SVT, we found a higher incidence of regional cancer and surgery and a lower incidence of the JAK2 V617F mutation.

The new or non-vitamin K antagonist oral anticoagulants: what have we learned since their debut.

One of the major advances in the management of thrombosis is arguably the introduction of the new non-vitamin K antagonist oral anticoagulants (NOACs). These are small molecules, designed to directly inhibit specific steps in the coagulation pathway, with dabigatran (Pradaxa), inhibiting thrombin and rivaroxaban (Xarelto), apixiban (Eliquis), edoxaban (Lixiana), and betrixaban being factor Xa inhibitors. They have several advantages over vitamin K antagonists such as warfarin, with more predictable bioavailability, fewer drug interactions, and improved safety, especially intracranial hemorrhage. Yet, since their debut, several issues have arisen with their increasing usage, with concerns over monitoring and reversal, being predominant. Issues addressed in this article include their efficacy, bleeding risk, and the recognition of a vulnerable population where monitoring is needed. The current approach to reversing the drug action is updated. The change in the approach to future drug design is also discussed.