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Selvadurai MV, Favaloro EJ, Chen VM. Mechanisms of Thrombosis in Heparin-Induced Thrombocytopenia and Vaccine-Induced Immune Thrombotic Thrombocytopenia. Semin Thromb Hemost 2023. [PMID: 36706782 DOI: 10.1055/s-0043-1761269] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Heparin-induced thrombocytopenia (HIT) and vaccine-induced immune thrombotic thrombocytopenia (VITT) are rare, iatrogenic immune-mediated conditions with high rates of thrombosis-related morbidity and mortality. HIT is a long-recognized reaction to the administration of the common parenterally administered anticoagulant heparin (or its derivatives), while VITT is a new, distinct syndrome occurring in response to adenovirus-based vaccines against coronavirus disease 2019 and potentially other types of vaccines. A feature of both HIT and VITT is paradoxical thrombosis despite a characteristic low platelet count, mediated by the presence of platelet-activating antibodies to platelet factor 4. Several additional factors have also been suggested to contribute to clot formation in HIT and/or VITT, including monocytes, tissue factor, microparticles, endothelium, the formation of neutrophil extracellular traps, complement, procoagulant platelets, and vaccine components. In this review, we discuss the literature to date regarding mechanisms contributing to thrombosis in both HIT and VITT and explore the pathophysiological similarities and differences between the two conditions.
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Affiliation(s)
- Maria V Selvadurai
- The Alfred Hospital, Melbourne, VIC, Australia.,ANZAC Research Institute, University of Sydney, Sydney, NSW, Australia
| | - Emmanuel J Favaloro
- Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Sydney Centres for Thrombosis and Haemostasis, NSW Health Pathology, Westmead Hospital, Westmead, NSW, Australia.,School of Dentistry and Medical Sciences, Faculty of Science and Health, Charles Sturt University, Wagga Wagga, NSW, Australia.,School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Westmead Hospital, Westmead, NSW, Australia
| | - Vivien M Chen
- ANZAC Research Institute, University of Sydney, Sydney, NSW, Australia.,Department of Haematology, Concord Repatriation General Hospital and NSW Health Pathology, Sydney, NSW, Australia
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Gaunt ER, Mabbott NA. The clinical correlates of vaccine-induced immune thrombotic thrombocytopenia after immunisation with adenovirus vector-based SARS-CoV-2 vaccines. IMMUNOTHERAPY ADVANCES 2021; 1:ltab019. [PMID: 34557868 PMCID: PMC8385946 DOI: 10.1093/immadv/ltab019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/04/2021] [Accepted: 08/16/2021] [Indexed: 12/13/2022] Open
Abstract
We are at a critical stage in the COVID-19 pandemic where vaccinations are being rolled out globally, in a race against time to get ahead of the SARS-CoV-2 coronavirus and the emergence of more highly transmissible variants. A range of vaccines have been created and received either emergency approval or full licensure. To attain the upper hand, maximum vaccine synthesis, deployment, and uptake as rapidly as possible is essential. However, vaccine uptake, particularly in younger adults is dropping, at least in part fuelled by reports of rare complications associated with specific vaccines. This review considers how vaccination with adenovirus vector-based vaccines against the SARS-CoV-2 coronavirus might cause rare cases of thrombosis and thrombocytopenia in some recipients. A thorough understanding of the underlying cellular and molecular mechanisms that mediate this syndrome may help to identify methods to prevent these very rare, but serious side effects. This will also help facilitate the identification of those at highest risk from these outcomes, so that we can work towards a stratified approach to vaccine deployment to mitigate these risks.
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Affiliation(s)
- Eleanor R Gaunt
- The Roslin Institute & Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
| | - Neil A Mabbott
- The Roslin Institute & Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
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LeVine DN, Cianciolo RE, Linder KE, Bizikova P, Birkenheuer AJ, Brooks MB, Salous AK, Nordone SK, Bellinger DA, Marr H, Jones SL, Fischer TH, Deng Y, Mazepa M, Key NS. Endothelial alterations in a canine model of immune thrombocytopenia. Platelets 2017; 30:88-97. [PMID: 29182425 DOI: 10.1080/09537104.2017.1378807] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Bleeding heterogeneity amongst patients with immune thrombocytopenia (ITP) is poorly understood. Platelets play a role in maintaining endothelial integrity, and variable thrombocytopenia-induced endothelial changes may influence bleeding severity. Platelet-derived endothelial stabilizers and markers of endothelial integrity in ITP are largely underexplored. We hypothesized that, in a canine ITP model, thrombocytopenia would lead to alterations in the endothelial ultrastructure and that the Von Willebrand factor (vWF) would serve as a marker of endothelial injury associated with thrombocytopenia. Thrombocytopenia was induced in healthy dogs with an antiplatelet antibody infusion; control dogs received an isotype control antibody. Cutaneous biopsies were obtained prior to thrombocytopenia induction, at platelet nadir, 24 hours after nadir, and on platelet recovery. Cutaneous capillaries were assessed by electron microscopy for vessel thickness, the number of pinocytotic vesicles, the number of large vacuoles, and the number of gaps between cells. Pinocytotic vesicles are thought to represent an endothelial membrane reserve that can be used for repair of damaged endothelial cells. Plasma samples were assessed for vWF. ITP dogs had significantly decreased pinocytotic vesicle numbers compared to control dogs (P = 0.0357) and the increase in plasma vWF from baseline to 24 hours correlated directly with the endothelial large vacuole score (R = 0.99103; P < 0.0001). This direct correlation between plasma vWF and the number of large vacuoles, representing the vesiculo-vacuolar organelle (VVO), a permeability structure, suggests that circulating vWF could serve as a biomarker for endothelial alterations and potentially a predictor of thrombocytopenic bleeding. Overall, our results indicate that endothelial damage occurs in the canine ITP model and variability in the degree of endothelial damage may account for differences in the bleeding phenotype among patients with ITP.
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Affiliation(s)
- Dana N LeVine
- a Department of Veterinary Clinical Sciences , Iowa State University , Ames , IA , USA.,b Department of Clinical Sciences , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA.,h Department of Pathology and Laboratory Animal Medicine , University of North Carolina , Chapel Hill , NC , USA
| | - Rachel E Cianciolo
- c Department of Veterinary Biosciences , The Ohio State University , Columbus , OH , USA
| | - Keith E Linder
- d Department of Population Health and Pathobiology , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA
| | - Petra Bizikova
- b Department of Clinical Sciences , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA
| | - Adam J Birkenheuer
- b Department of Clinical Sciences , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA
| | - Marjory B Brooks
- e Department of Population Medicine and Diagnostic Sciences , Cornell University, College of Veterinary Medicine , Ithaca , NY , USA
| | - Abdelghaffar K Salous
- f Division of Cardiovascular Medicine , The Gill Heart Institute, University of Kentucky , Lexington , KY , USA
| | - Shila K Nordone
- g Department of Molecular Biomedical Sciences , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA
| | - Dwight A Bellinger
- h Department of Pathology and Laboratory Animal Medicine , University of North Carolina , Chapel Hill , NC , USA
| | - Henry Marr
- b Department of Clinical Sciences , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA
| | - Sam L Jones
- b Department of Clinical Sciences , North Carolina State University, College of Veterinary Medicine , Raleigh , NC , USA
| | - Thomas H Fischer
- h Department of Pathology and Laboratory Animal Medicine , University of North Carolina , Chapel Hill , NC , USA
| | - Yu Deng
- i Department of Biostatistics , University of North Carolina , Chapel Hill , NC , USA
| | - Marshall Mazepa
- h Department of Pathology and Laboratory Animal Medicine , University of North Carolina , Chapel Hill , NC , USA
| | - Nigel S Key
- h Department of Pathology and Laboratory Animal Medicine , University of North Carolina , Chapel Hill , NC , USA.,j Department of Medicine , University of North Carolina , Chapel Hill , NC , USA
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Abstract
Thrombocytopenia is common in critically ill patients and increases morbidity and mortality. A diagnosis of heparin-induced thrombocytopenia (HIT) is frequently considered in any ICU patient who develops thrombocytopenia in the context of ongoing heparin exposure. As the usual tests to diagnose HIT are often neither specific nor sensitive enough to be confirmatory, the intensivist must largely rely on clinical judgment in treatment decisions. Patients in the ICU may also develop thrombocytopenia resulting from non-HIT immune mechanisms, nonimmune platelet consumption, and from decreased platelet production due to preexisting disorders or as a result of their critical illness and/or drug therapy.
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Affiliation(s)
- Robert I Parker
- Department of Pediatrics, Stony Brook University School of Medicine, Pediatric Hematology/Oncology, Stony Brook Long Island Children's Hospital, Stony Brook, NY 11794-8111, USA.
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Hall A, Thachil J, Martlew V. Heparin-Induced Thrombocytopenia in the Intensive Care Unit. J Intensive Care Soc 2010. [DOI: 10.1177/175114371001100107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Heparin-induced thrombocytopenia (HIT) occurs following an immune reaction to the administration of heparin, which results in increased platelet activation and thrombocytopenia, and lead to arterial and venous thrombosis in untreated cases. It may be considered as an idiosyncratic, drug-induced reaction in which heparin injections result in the formation of complexes with platelet factor 4 (PF4), triggering an antibody-mediated reaction in certain individuals. Low platelet count in this instance is secondary to platelet aggregation and can lead to thrombotic complications by vascular occlusion and other mechanisms. Early recognition of this complication is essential to prevent life- and limb-threatening thrombosis. Therefore, it is important that intensive care physicians who administer heparin in different forms are aware of this potential adverse event and follow a regular plan in monitoring the platelet count while the patient is on heparin. In a patient whose platelet count falls while on heparin, when no other diagnostic possibilities can easily explain it, immediate withdrawal of any form of heparin and commencement of an alternative anticoagulant is necessary until the diagnosis of HIT is confirmed or excluded. At the same time, it is important that over-diagnosis of HIT is not made to avoid unwanted bleeding complications from the alternative anticoagulants. This review outlines the pathophysiology, diagnosis and management of HIT with a focus on the intensive care setting.
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Affiliation(s)
- Alison Hall
- Specialist Registrar, Department of Anaesthesia and Critical Care, University of Liverpool
| | - Jecko Thachil
- Specialist Registrar, Department of Haematology, University of Liverpool
| | - Vanessa Martlew
- Consultant, Department of Haematology, Royal Liverpool University Hospital
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Heparin-induced thrombocytopenia: some working hypotheses on pathogenesis, diagnostic strategies and treatment. Curr Opin Hematol 2008; 15:456-64. [PMID: 18695368 DOI: 10.1097/moh.0b013e32830b84a2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW The present contribution will illustrate some evolving concepts on the pathogenesis and clinical management of heparin-induced thrombocytopenia (HIT) and describe how we approach patients with suspected HIT at our institution. RECENT FINDINGS HIT is caused by an autoimmune reaction leading to the formation of antibodies directed against platelet factor 4. Conditions favoring the development of anti-platelet factor 4/heparin antibodies differ from those required for the formation of macromolecular ternary complexes (HIT antibody/platelet factor 4/heparin), which are able to activate platelets and induce clinical HIT. HIT can be diagnosed by combining its pretest probability with the quantitative result of rapid HIT-antibody assays. Treatment of acute HIT requires inhibition of in-vivo thrombin generation by means of alternative nonheparin anticoagulant drugs, whose effective dosage appears to be significantly lower than the official recommendations. As HIT antibodies are transient, HIT patients can be re-exposed to heparin, provided that previous heparin treatment is remote and that anti-platelet factor 4/heparin antibodies are undetectable. SUMMARY In recent years, there has been a continuing elucidation of pathogenic and clinically relevant issues, which are intellectually rewarding to follow and should enable us to offer a steadily improving treatment to the HIT patients we are in charge of.
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