American Society of Hematology 2018 guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia

Successful Treatment With the Oral Factor Xa Inhibitor Edoxaban in Heparin-Induced Thrombocytopenia With Thrombosis

Heparin-induced thrombocytopenia with thrombosis (HITT) is a rare immune reaction to the drug heparin that causes increased blood clotting, putting patients at risk for arterial and venous thromboembolism which can have severe consequences. We present a case of HITT successfully treated with the direct oral anticoagulant (DOAC), edoxaban. A 56-year-old man had surgery to remove a colorectal mass. After discharge, he developed chest discomfort, shortness of breath, and low oxygen levels and was diagnosed with a right-sided lobar pulmonary embolism. His platelet count dropped, his tests confirmed a diagnosis of HITT, and he was initially treated with fondaparinux. After showing clinical and laboratory improvement, he was switched to edoxaban. Despite being diagnosed with colonic adenocarcinoma during follow-up, the patient's platelet count returned to normal, and he did not experience any more blood clots or serious bleeding events. The use of DOACs like edoxaban as potential therapies for HITT is promising; further research is being conducted to evaluate their effectiveness, safety, and potential benefits for treating this acquired high-risk thrombophilia.

Preliminary insights into monitoring bivalirudin anticoagulation: A retrospective cohort study of aPTT versus a chromogenic anti-IIa assay

BACKGROUND

Bivalirudin infusions are traditionally monitored with activated partial thromboplastin time (aPTT) despite the poor correlation with bivalirudin dose-response curves. This discordance may lead to over or under-anticoagulation, predisposing patients to bleeding or thrombosis and repeated dose adjustments. While a chromogenic bivalirudin-specific anti-IIa assay, which measures bivalirudin plasma concentrations, is available, the extent to which this test may improve clinical monitoring and patient outcomes remains unclear. Accordingly, we aimed to retrospectively assess the correlation between the bivalirudin dose and the anti-IIa assay and to establish a therapeutic range. We then performed a retrospective comparative cohort study assessing the impact of anti-IIa monitoring compared to aPTT on patient outcomes.

METHODS

Plasma samples from adults receiving bivalirudin anticoagulation were analyzed to assess the correlation between bivalirudin dose, aPTT, and the anti-IIa assay. A retrospective comparative analysis was then conducted to evaluate operational and clinical outcomes in patients monitored with aPTT versus the anti-IIa assay.

RESULTS

Analysis of 127 samples from 11 bivalirudin-anticoagulated adults showed a very weak correlation between bivalirudin dose and aPTT (r2 = 0.08), while a strong correlation was seen with the anti-IIa assay (r2 = 0.65). The dose-response slope's coefficient of variation (CV) for the aPTT and anti-IIa assay were 31 % and 6.6 %, respectively. Patients monitored with the anti-IIa assay had significantly higher time in therapeutic range than those monitored with aPTT (92.1 % vs. 26 %, p < 0.001).

CONCLUSIONS

These findings suggest that the anti-IIa assay provides more reliable bivalirudin monitoring than aPTT, with a significant reduction in minor bleeding.

Evaluation of a rapid immunochromatographic diagnostic test for heparin-induced thrombocytopenia: validation of delayed test and whole blood test

Heparin-induced thrombocytopenia (HIT) is a rare, iatrogenic condition, characterized by its potential severity and diagnostic difficulties. There are rapid diagnostic tests for suspected HIT. Among these, the STic Expert® HIT has a good sensitivity to detect HIT. However, it must be performed within 2 h after sampling. The aim of this study was to evaluate a delayed STic Expert® HIT test in plasma and whole blood. Thirty-six patients were prospectively included for HIT testing delayed analysis and 64 for whole blood analysis. For any request for HIT testing, an analysis by STic Expert® HIT was performed within 2 h and 8 h post-sampling. Any positive result was confirmed by a functional test, platelet aggregation with heparin, release of 14C-serotonin assay (SRA), and immunological assay for anti-platelet factor 4 IgG antibodies. Among the 36 patients for delayed analysis, 20 had an initially positive STic Expert® HIT test. Among the 64 patients for whole blood analysis, 20 had an initially positive STic Expert® HIT test, and 24 positives in whole blood. For the test performed at T0, Se = 100 %, Sp = 68.4 %, PPV = 73.9 %, and NPV = 100 %. The Chi-square (X2) = 18.2 with p < 0.001. For the test performed at T = 8 h, Se = 100 %, Sp = 68.4 %, PPV = 73.9 %, and NPV = 100 %. The X2 = 18.2 with p < 0.001. For the test performed in whole blood, Se = 100 %, Sp = 74.4 %, PPV = 37.5 %, and NPV = 100 %. The X2 = 18.6 with p < 0.001. In conclusion, we have demonstrated that the STic Expert® can be used to perform an HIT diagnostic test 8 h after sampling and on whole blood. However, this study needs to be confirmed on a larger number of samples.

Catastrophic Thrombosis: A Narrative Review

Catastrophic thrombosis is a severe condition characterized by a hypercoagulable tendency, leading to multiple thromboembolic events in different blood vessels, usually within a short timeframe. Several conditions have been associated with the development of catastrophic thrombosis, including the catastrophic antiphospholipid syndrome, thrombotic anti-platelet factor 4 immune disorders, thrombotic microangiopathies, cancers, the hyper-eosinophilic syndrome, pregnancy, infections, trauma, and drugs. Thrombotic storm represents a medical emergency whose management represents a serious challenge for physicians. Besides the prompt start of anticoagulation, a patient's prognosis depends on early recognition and possible treatment of the underlying condition. In this narrative review, we summarize the main characteristics of catastrophic thrombosis, analyzing the various conditions triggering such life-threatening complication. Finally, an algorithm with the diagnostic workup and the initial management of patients with catastrophic thrombosis is presented.

Occlusive cutaneous vasculopathies: rare differential diagnoses

In addition to erythematous plaques, nodules, ulcerations, and necrosis, retiform purpura and livedo racemosa are indications of occlusive cutaneous vasculopathies. In contrast to cutaneous vasculitis, occlusive cutaneous vasculopathies primarily lead to vascular occlusion of the skin and only secondarily to signs of vascular inflammation. The lower legs are typically affected, but especially in the presence of acral skin changes, occlusive cutaneous vasculopathies should also be considered. Various stimuli can trigger occlusive cutaneous vasculopathies, including systemic or vascular coagulopathies, emboli, platelet or erythrocyte aggregates, cold-dependent gelling and agglutination of immunoglobulins, or, less commonly, medications.

Refractory autoimmune heparin-induced thrombocytopenia following cardiac surgery

Autoimmune heparin-induced thrombocytopenia (aHIT) is a severe subtype of heparin-induced thrombocytopenia characterized by persistent thrombocytopenia and prothrombotic condition, even though anticoagulation with heparin has been discontinued. Here, we report on a patient with a previous history of aHIT where reexposure to heparin during cardiac surgery resulted in recurrent aHIT with pulmonary embolism. Alternative anticoagulants, as well as high-dose intravenous immunoglobulin, were ineffective, and only multiple cycles of therapeutic plasma exchange restored platelet counts and prevented further thrombosis progression. The therapy was guided by an ex vivo model of antiplatelet factor 4 (PF4)-mediated thrombosis that showed accurate performance in predicting the clinical outcome. Most importantly, the ability to induce thrombus formation was mainly caused by anti-PF4 (heparin-independent) antibodies. Our paper provides the first description of recurrent aHIT with translational evidence that pathogenic heparin-independent anti-PF4 antibodies can be specifically targeted by therapeutic plasma exchange, emphasizing the clinical use in refractory cases of aHIT.

Acute Intracerebral Hemorrhage Associated with Extensive Venous Thrombosis Due to Spontaneous Heparin-Induced Thrombocytopenia After Total Knee Replacement: A Case Report

INTRODUCTION

Heparin-induced thrombocytopenia (HIT) is an autoimmune life-threatening prothrombotic syndrome associated with low platelet count after heparin exposure. Spontaneous heparin-induced thrombocytopenia (S-HIT) is an even less frequent variant of HIT, with only a handful of reports available in the literature, where unexplained thrombocytopenia and/or thrombosis without recent heparin exposure occurs in the setting of positive anti-PF4 antibodies.

CASE PRESENTATION

We report a case of S-HIT associated with pulmonary artery embolism, left internal jugular vein, and cerebral vein sinus thrombosis complicated with ipsilateral acute intracerebral hemorrhage.

DISCUSSION

It is important to highlight that in patients with otherwise unexplained thrombocytopenia and prior exposure to an inflammatory process, S-HIT should be on the differential.

CONCLUSIONS

Recognition and avoidance of heparin exposure is the most important aspect of S-HIT, as the management is otherwise similar to HIT.

Safe and effective anticoagulation use: case studies in anticoagulation stewardship

Anticoagulant use is prevalent and associated with significant potential for harm. Anticoagulation stewardship practice has emerged to address care gaps and promote safe, effective, and cost-conscious anticoagulation use across health care systems. We present 4 patient cases describing common challenges in anticoagulation management: inappropriate dosing of direct oral anticoagulants, the diagnosis and management of heparin-induced thrombocytopenia, periprocedural anticoagulation management, and heavy menstrual bleeding on anticoagulation. We discuss available examples of successful stewardship programs that can address the challenges of each case, demonstrating how an investment in anticoagulation stewardship can improve patient outcomes.

Direct Oral Anticoagulants Versus Warfarin in Patients With Isolated Heparin-Induced Thrombocytopenia or Heparin-Induced Thrombocytopenia With Thrombosis

No existing studies compare oral anticoagulants to treat heparin-induced thrombocytopenia with or without thrombosis (HIT/HITT). This retrospective study evaluated thrombotic and bleeding outcomes in adults treated for HIT/HITT with a direct oral anticoagulant (DOAC) or warfarin between 2012 and 2023 within the Ochsner Health System. Patients with mechanical heart valves, valvular atrial fibrillation, antiphospholipid syndrome, active malignancy, or venous thromboembolism (VTE) within the previous 6 months were excluded. The primary outcome was a composite of new or progressive VTE or arterial thromboembolism. Secondary outcomes included major and clinically relevant non-major bleeding, duration of hospitalization, time to platelet recovery, and incidence of skin necrosis, gangrene, and amputation. Forty-nine patients receiving a DOAC and 30 patients receiving warfarin were included. Baseline characteristics were similar between cohorts. There were non-statistically significant increased rates of both the primary outcome (8.9% vs. 4.3%, p = 0.65) and the composite bleeding outcome (32.7% vs. 23.3%, p = 0.37) in the DOAC cohort. Larger, prospective studies are needed to confirm these findings.

Intravenous immunoglobulin prevents thrombosis in an endothelialized disease model of heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin, associated with increased risk of thromboembolic complications. Intravenous immunoglobulins (IVIGs) have been used as a therapeutic for HIT and are believed to alleviate thrombocytopenia and reduce thrombosis risk. Yet the antithrombotic effects of IVIG in HIT remain underexplored.

OBJECTIVE

To investigate the effect of IVIG on thrombus formation in an ex vivo model of HIT-IgG-induced thrombosis.

METHODS

Microfluidic channels were coated with a confluent monolayer of human umbilical vein endothelial cells that were primed with TNF-α to induce an activated, inflammatory state. Whole blood was exposed to unfractionated heparin, with or without IVIG before subjecting to treatment with a monoclonal HIT-like antibody (K070), or HIT-patient-IgG. Recalcified blood was perfused over human umbilical vein endothelial cells at venous shear stress. Thrombus structure and dynamics were investigated by immunofluorescence microscopy.

RESULTS

HIT-patient-IgGs and K070 induced thrombus formation in the presence of prophylactic heparin exposure, over TNF-α treated, inflamed endothelial cells. HIT thrombi were enriched in fibrin, phosphatidylserine-bearing platelets, and leukocyte aggregates. We observed thrombi being formed on adherent platelets, which gradually recruited leukocytes into a three-dimensional thrombus structure. Pretreatment of blood with IVIG significantly reduced cellular adhesions and prevented thrombus formation.

CONCLUSION

Our endothelialized ex vivo flow chamber system effectively recapitulates the immunothrombotic phenotype of HIT and offers a reliable tool to urgently validate the efficacy of IVIG intervention against HIT-IgG-induced thrombosis in patients.

Anti-platelet Factor 4 Antibody-Mediated Disorders: An Updated Narrative Review

Anti-platelet factor 4 (PF4) antibody-mediated disorders are a heterogeneous group of diseases characterized by the presence of highly pathogenic immunoglobulins G directed against PF4 and/or PF4/heparin complexes. These antibodies are able to activate platelets, neutrophils, and monocytes, thus resulting in thrombocytopenia and a hypercoagulable state. Five different forms of anti-PF4 antibody-mediated disorders have been identified: (1) classic heparin-induced thrombocytopenia (HIT) mediated by heparin and certain polyanionic drugs; (2) autoimmune HIT characterized by the presence of anti-PFA/polyanion antibodies that can strongly activate platelets even in the absence of heparin; (3) spontaneous HIT characterized by thrombocytopenia and thrombosis without proximate exposure to heparin, with two subtypes: (a) post-total knee arthroplasty and cardiac surgery using cardiopulmonary bypass or extracorporeal membrane oxygenation and (b) postinfections; (4) vaccine-induced immune thrombotic thrombocytopenia (VITT) characterized by thrombocytopenia, arterial and venous thrombosis, or secondary hemorrhage after receiving adenoviral vector vaccines for coronavirus disease 2019; (5) VITT-like disorders triggered by adenoviral infections. Although extremely rare and largely unknown, there has been growing interest in the VITT syndrome in recent years due to its clinical relevance. Timely detection of these antibodies is crucial for the diagnosis and treatment of anti-PF4 antibody-mediated disorders, via anti-PF4 antibody immunoassays using several antibody capture systems (e.g., enzyme-linked immunosorbent assay-based, particle gel, turbidimetry) and functional assays (e.g., serotonin release assay or heparin-induced platelet activation). We aimed to present the latest on laboratory findings, clinical characteristics, and therapeutic approaches for anti-PF4 antibody-mediated disorders.

"Keep HIT in Mind and Take Care". Multiple Tips From a Single Patient

Introduction

Heparin-induced thrombocytopenia (HIT) is a relatively rare condition burdened by a high rate of complications and mortality. Cardiac surgery is a high risk setting for this condition. But in this area, some particularities can make both diagnosis and treatment difficult. Warfarin is often needed after valvular surgery but may be dangerous if HIT is ongoing. Danaparoid is the only anticoagulant whose mechanism of action has been demonstrated to counteract the pathogenesis of HIT. However, the 24-hour half-life challenges its use after surgery.

Case Presentation

Here, we present a case in which HIT occurred six days after cardiac surgery. Warfarin was initiated two days after surgery but was stopped five days later, given the high risk of bleeding due to concomitant thrombocytopenia. HIT probability was initially underestimated, because a misleading diagnosis of endocarditis was made. When redo surgery was performed, no infectious masses were found, but a large thrombus was removed from the left atrium. Bivalirudin and danaparoid were used as alternative anticoagulants during the subsequent postoperative course.

Conclusion

HIT should always be kept in mind after cardiac surgery, even if a more plausible cause of thrombocytopenia is present. Discontinuation of warfarin could lead to catastrophic consequences if an unrecognized HIT is ongoing, and an alternative anticoagulant is not started. Bivalirudin and danaparoid were used after the diagnosis of HIT, adapting anticoagulant therapy to the needs of recent surgery.

The dynamic range of immunoassays for heparin-induced thrombocytopenia

BACKGROUND

Following the current guidelines, immunoassays for the diagnosis of heparin-induced thrombocytopenia (HIT) are interpreted dichotomously, with test results categorized as either positive or negative. However, the extent to which test results hold diagnostic significance across the entire dynamic range remains unclear.

OBJECTIVES

We utilized data from the prospective towards precise and rapid diagnosis of heparin-induced thrombocytopenia study, comprising 1393 consecutive patients with suspected HIT, to assess the diagnostic significance of 2 heparin/platelet factor 4 immunoassay test results across their respective dynamic ranges: HemoSil Acustar HIT IgG (chemiluminescence immunoassay [CLIA]) and Lifecodes PF4 immunoglobulin G (enzyme-linked immunosorbent assay [ELISA]).

METHODS

HIT diagnosis was determined by a washed platelet heparin-induced platelet activation assay. For each measurement point in the dataset, we computed likelihood ratios (LRs), sensitivities, and specificities. To provide posttest probabilities for individual test results, we calculated interval-specific LRs and integrated them into a web-based calculator.

RESULTS

The prevalence of HIT was 8.5% (n = 119). An LR of ≥10 was first achieved at 0.3% of the dynamic range (0.4 U/mL; CLIA) and then at 16% (0.64 optical density; ELISA). An LR of ≥100 was present at 9.4% (12 U/mL; CLIA) and 75.0% (3.0 optical density; ELISA). The slope of the linear regression line (LR ∼ dynamic range) was 9.5 (CLIA) and 0.9 (ELISA).

CONCLUSION

Despite both immunoassays showing an association between results and diagnostic significance, the strength of the association varies by assay. CLIA has a larger increase per measurement unit. Posttest probabilities for individual patients can be estimated using a web-based calculator: https://pcd-research.shinyapps.io/BayesianCalculator/.

Guidance-Based Appropriateness of Hemostasis Testing in the Acute Setting

In this review, we aim to highlight the extent of inappropriate hemostasis testing and provide practical guidance on how to prevent it. We will focus on the acute setting, including but not limited to the emergency department and intensive care unit. To this end, we will first discuss the significance of inappropriateness, in the general context of laboratory medicine. This includes acknowledging the importance of the phenomenon and attempting to define it. Next, we describe the harmful consequences of inappropriate testing. Finally, we focus on the inappropriate use of hemostasis testing in the acute setting. The second section describes how interventions-in particular, the implementation of guidance for testing-can efficiently reduce inappropriateness. In the third section, we summarize the available recommendations for rational use of hemostasis testing (platelet count, activated partial thromboplastin time, prothrombin time/international normalized ratio, fibrinogen, thrombin time, D-dimer, anti-Xa assay, antithrombin, ADAMTS13 activity, antiheparin-PF4 antibodies, viscoelastometric tests, coagulation factors, and platelet function testing), as supported by guidelines, recommendations, and/or expert opinions. Overall, this review is intended to be a toolkit in the effort to promote the appropriate use of hemostasis testing. Hopefully, the new In Vitro Diagnostic Medical Device Regulation (EU) 2017/746 (IVDR) should help in improving the availability of evidence regarding clinical performance of hemostasis assays.

Anti-Platelet factor 4 immunothrombosis-not just heparin and vaccine triggers

Derailments at the tightly regulated interface of blood coagulation and innate inflammatory immune responses can lead to pathologic immunothrombosis. A special subset of immunothrombosis is caused by antibodies against platelet-factor 4 (PF4). Anti-PF4 antibodies triggered by heparin treatment in heparin-induced thrombocytopenia (HIT) are known for more than 50 years. Interest in anti-PF4 disorders rekindled when first cases of vaccine-induced immune thrombocytopenia and thrombosis (VITT) occurred during the worldwide COVID-19 vaccination campaign. During this time new diagnostic procedures were established to identify affected patients and to differentiate between different kinds of anti-PF4 antibodies. This review article gives an overview about the current knowledge of HIT and VITT with concepts of the underlying pathogenesis. In addition to heparin and vaccination as known triggers for HIT and VITT, concepts for other clinical cases with anti-PF4 antibodies are described in more detail. Anti-PF4 antibodies in atypical HIT-like syndromes could be triggered by presentation of various polyanions, eg, in settings of orthopedic surgery or bacterial infections. Anti-PF4 antibodies in acute VITT-like disorders can occur after viral infections. Chronic VITT-like anti-PF4 antibodies causing recurrent thrombosis and thrombocytopenia are often linked to monoclonal gammopathies. For all disorders with anti-PF4 antibodies, timely identification in patients with thrombocytopenia with or without thrombosis is crucial for successful therapy.

Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (fifth edition)

Hemorrhagic complications associated with regional anesthesia are extremely rare. The fifth edition of the American Society of Regional Anesthesia and Pain Medicine's Evidence-Based Guidelines on regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy reviews the published evidence since 2018 and provides guidance to help avoid this potentially catastrophic complication.The fifth edition of the American Society of Regional Anesthesia and Pain Medicine's Evidence-Based Guidelines on regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy uses similar methodology as previous editions but is reorganized and significantly condensed. Therefore, the clinicians are encouraged to review the earlier texts for more detailed descriptions of methods, clinical trials, case series and pharmacology. It is impossible to perform large, randomized controlled trials evaluating a complication this rare; therefore, where the evidence is limited, the authors continue to maintain an 'antihemorrhagic' approach focused on patient safety and have proposed conservative times for the interruption of therapy prior to neural blockade. In previous versions, the anticoagulant doses were described as prophylactic and therapeutic. In this version, we will be using 'low dose' and 'high dose,' which will allow us to be consistent with other published guidelines and more accurately describe the dose in the setting of specific patient characteristics and indications. For example, the same 'high' dose may be used in one patient as a treatment for deep venous thrombosis (DVT) and in another patient as prophylaxis for recurrent DVT. Due to the increasing ability to obtain drug-specific assays, we have included suggestions for when ordering these tests may be helpful and guide practice. Like previous editions, at the end of each recommendation the authors have clearly noted how the recommendation has changed from previous editions.

High-dose intravenous immunoglobulin G and usual heparin anticoagulation for urgent cardiac surgery in a patient with severe autoimmune heparin-induced thrombocytopenia

A 56-year-old woman required urgent cardiac surgery for Streptococcus mitis mitral valve infective endocarditis complicated by severe autoimmune heparin-induced thrombocytopenia (aHIT). We reasoned that the combination of high-dose intravenous immunoglobulin G (IVIG; to mitigate aHIT antibody-mediated platelet activation in the presence of heparin) together with the high concentrations of heparin attained during cardiac surgery (which typically produces less platelet activation in vitro vs usual therapeutic heparin concentrations) might prove effective. Accordingly, our patient underwent cardiac surgery with heparin following high-dose IVIG (1 g/kg × 2) without intra- or postoperative thrombosis. Serial serotonin release assays, using blood obtained pre-/post-IVIG, showed minimal platelet activation (∼30% serotonin release) post-IVIG at heparin concentrations typically obtained during cardiac surgery (2-5 U/mL) and significantly less than pre-IVIG serum in heparin's absence (∼85% serotonin release). In the setting of urgent cardiac surgery, preoperative high-dose IVIG appears to be a reasonable strategy to reduce platelet-activating effects of heparin-induced thrombocytopenia (including aHIT) antibodies, permitting safe use of standard intraoperative heparin dosing.

Relevance of anti-platelet factor 4/heparin antibodies and platelet activation in systemic inflammatory diseases and thrombosis disorders: insight from the COVID-19 pandemic

Background

The increased interest in anti-platelet factor 4 (PF4)-heparin complex (anti-PF4/H) antibodies following the COVID-19 pandemic has established them as crucial players in immunothrombosis.

Objectives

We aimed to investigate the involvement of anti-PF4/H antibodies during COVID-19 and after vaccination, particularly in patients with systemic inflammatory disease (SID).

Methods

This retrospective study analyzed the presence of anti-PF4/H antibodies and their ability to induce platelet activation in COVID-19 patients with and without suspected heparin-induced thrombocytopenia (HIT), vaccine-induced immune thrombotic thrombocytopenia (VITT) patients, and in controls and SID patients following COVID-19 vaccination.

Results

No significant increase in anti-PF4/H antibody levels was observed during COVID-19 regardless of disease severity. Despite a 2-fold increase in HIT suspicion observed during the pandemic, there was no corresponding increase in HIT diagnoses. Additionally, no significant increase in anti-PF4/H levels was noted after vaccination, even in SID patients. None of the positive anti-PF4/H antibodies detected in COVID-19 or vaccination cohorts induced platelet activation, measured by soluble P-selectin levels and flow cytometry-based on platelet microvesicle generation. Finally, in VITT patients, unlike in HIT patients, anti-PF4/H levels were strongly associated with platelet microvesicle assay and moderately with soluble P-selectin levels.

Conclusion

Our study found no significant increase in anti-PF4/H antibodies in COVID-19 or after vaccination, including in SID patients. However, in VITT patients, but not in HIT patients, these antibodies were correlated with platelet activation. This finding suggests that anti-PF4/H antibodies play a different role in the pathophysiology of VITT but that their interest is limited outside clear contexts of HIT/VITT suspicion.

Suspected heparin-induced thrombocytopaenia in pulmonary thromboendarterectomy: retrospective cohort

OBJECTIVES

Heparin is given for anticoagulation during and after pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension. Our objective was to add to the limited data available on the incidence, management and outcomes of suspected heparin-induced thrombocytopaenia after pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension.

METHODS

This retrospective single-centre study included consecutive patients with suspected heparin-induced thrombocytopaenia after pulmonary thromboendarterectomy done in 2005-2018. Confirmed heparin-induced thrombocytopaenia was defined as positive findings from both the antibody test and the platelet aggregation test. Patients with versus without confirmed heparin-induced thrombocytopaenia were compared, as well as patients with versus without heparin replacement therapy within the group with unconfirmed heparin-induced thrombocytopaenia. The platelet counts over time were compared to those in controls without suspected heparin-induced thrombocytopaenia.

RESULTS

Heparin-induced thrombocytopaenia was suspected in 86 (6.3%) of 1360 patients and confirmed in 16 (16/86, 19%), all of whom received heparin replacement therapy and survived to intensive care unit discharge. Of the remaining 70 patients, 28 (40%) received heparin replacement therapy and less often experienced bleeding compared to the other 42 (3.6% vs 21.4%, P = 0.043). Intensive care unit mortality was 17/70 (24.3%) and was lower in the subgroup given heparin replacement therapy (10.7% vs 33.3%; P = 0.046). Confirmed heparin-induced thrombocytopaenia was associated with a sharp platelet-count drop on Day 5. In unconfirmed suspected heparin-induced thrombocytopaenia, the early platelet-count decline was similar to that in the controls without suspected heparin-induced thrombocytopaenia, but the baseline count was lower.

CONCLUSIONS

Clinical features suggesting heparin-induced thrombocytopaenia after pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension were associated with excess mortality. Relay heparin replacement therapy was associated with lower mortality and fewer bleeding events.

Warfarin and heparin monitoring in antiphospholipid syndrome

Anticoagulation is central to the management of antiphospholipid syndrome (APS), an acquired thrombo-inflammatory disorder characterized by thrombosis (venous, arterial, or microvascular) or pregnancy morbidity, in association with persistent antiphospholipid antibodies (aPL; ie, 1 or more of lupus anticoagulant [LA], anticardiolipin, anti-beta-2- glycoprotein I, IgG, or IgM antibodies). The mainstay of anticoagulation in patients with thrombotic APS is warfarin or an alternative vitamin K antagonist (VKA) and, in certain situations, low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH). Accurate assessment of anticoagulation intensity underpins optimal anticoagulant dosing for thrombus treatment or primary/secondary prevention. In patients with APS on warfarin, the international normalized ratio (INR) may not be representative of anticoagulation intensity due to an interaction between LA and the thromboplastin reagent used in the INR determination. In this review, we summarize the use of warfarin/VKA in patients with APS, along with venous and point-of-care INR monitoring. We also discuss the role and monitoring of LMWH/UFH, including in the anticoagulant refractory setting and during pregnancy.

Practical guide to the diagnosis and management of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an immune reaction to heparin associated with thrombocytopenia, thrombotic risk, and a high risk of morbidity and mortality. Given the frequent use of heparin and the common occurrence of thrombocytopenia in hospitalized patients, the diagnosis and management of HIT is a recurrent challenge in everyday inpatient care. This article presents practical guidance and tools to support the individual clinician providing evidence-based care to patients with suspected or confirmed HIT. The optimal diagnostic evaluation requires the stepwise use of risk-stratification tools and laboratory assays. Management requires the selection and use of nonheparin anticoagulation in these complex patients with both increased thrombotic risk and possible concurrent increased bleeding risk due to thrombocytopenia. Each step in the diagnostic and management process has important nuances and complexities, many of which vary based on patient characteristics and institutional resources. Given the many challenges of HIT care, truly practical management is best achieved when tools are implemented to support the delivery of consistent, high quality, and cost-effective care across health systems.

Inflammatory and vaso-occlusive ulcers: Part II - Management

In the second part of this CME, we present an approach for the management of inflammatory and vaso-occlusive ulcers and highlight the need for further research in this field. The 3 overarching principles for management are etiology-specific treatment, ulcer care, and consideration of patient comorbidities and risk factors for poor healing. Both etiology-specific treatment and management of patient comorbidities and risk factors often require collaboration with providers from other specialties. Ulcer care is governed by tissue debridement, infection control, management of moisture imbalance, and epithelial edge advancement. As wound healing is a dynamic process, management should be adapted to changes in the status of the ulcer.

Efficacy of Therapeutic Plasma Exchange or Cangrelor as an Adjunctive Strategy to Facilitate Cardiopulmonary Bypass in Patients with Heparin-Induced Thrombocytopenia: A Systematic Review and Meta-Analysis

OBJECTIVE

Conduct a systematic review and meta-analysis of the efficacy of therapeutic plasma exchange (TPE) or intravenous cangrelor to prevent thromboembolism in patients with heparin-induced thrombocytopenia (HIT) who undergo cardiopulmonary bypass (CPB) with heparin.

DESIGN

Systematic review and meta-analysis.

SETTING

N/A.

PARTICIPANTS

Adults having cardiac surgery with a history of HIT who received preoperative or intraoperative TPE or intravenous cangrelor as an adjunct to CPB with heparin.

INTERVENTIONS

None MEASUREMENTS AND MAIN RESULTS: A systematic review was performed using MEDLINE, PubMed, and Google Scholar. The primary outcome was avoidance of thromboembolism (venous or arterial) during or after CPB. Proportional meta-analysis with a random effects model was used to calculate a weighted-pooled proportion/efficacy for the study's primary outcome. Fifty-seven patients in 17 reports received TPE as an adjunctive treatment to prevent HIT-related thrombosis related to heparinization during CPB and 3 (5.3%) experienced thrombosis. Proportional meta-analysis suggested a weighted-pooled freedom from perioperative thromboembolism rate of 91.0% (95% CI 82.6%-96.9%). Fifteen patients in 6 reports received intravenous cangrelor as an adjunctive treatment to prevent HIT-related thrombosis related to heparinization during CPB and 2 (13.3%) experienced thrombosis. Proportional meta-analysis suggested a weighted-pooled freedom from perioperative thromboembolism rate of 83.0% (95% CI 61.2%- 97.6%).

CONCLUSIONS

TPE and cangrelor are feasible strategies to prevent thromboembolism in adults with HIT who require CPB with heparin. Given the relatively small number of cases in the published literature and a high likelihood for publication and detection biases, prudence remains warranted when using these strategies.

Inflammatory and vaso-occlusive ulcers: Part I - Clinical presentation and diagnosis

In this CME, we review 2 specific categories of ulcers: inflammatory (where inflammation is the primary pathologic process leading to ulceration) and vaso-occlusive (where occlusion is the primary process). Inflammatory ulcers include pyoderma gangrenosum and vasculitides, whereas livedoid vasculopathy, calciphylaxis, and Martorell ulcers are vaso-occlusive ulcers. Determining the causes of ulcers in these conditions may require laboratory evaluation, biopsy, and imaging.

Danaparoid-Consensus Recommendations on Its Clinical Use

(1) Background: Danaparoid sodium is a heparinoid antithrombotic that has been used for over 40 years for prophylaxis of DVT in non-HIT patients and for the treatment of heparin-induced thrombocytopenia (HIT) with and without thrombosis. This update summarises current information on its pharmacology and reviews danaparoid dose management in a broad spectrum of clinical situations, including off-label indications. (2) Methods: Evidence from published clinical studies, case reports, compassionate use of danaparoid, and spontaneously reported serious adverse events is summarised and analysed by an interdisciplinary expert group to develop a consensus on dosing regimens of danaparoid for complex clinical situations, including vulnerable patient populations. (3) Results: Dosing regimens are proposed, together with monitoring recommendations and target anti-factor Xa ranges. (4) Conclusion: In a comprehensive summary detailed interdisciplinary dosing recommendations are described to provide a basis for safe and effective use of danaparoid.

Limitations of a platelet count-based clinical decision support system to facilitate diagnosis of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a rare complication of heparin exposure with potential for significant morbidity and mortality. Early identification and treatment can prevent catastrophic thrombosis. Herein, we report the performance of a platelet count-based clinical decision support system (CDSS) where providers received a notification when a patient had a platelet count decline of ≥50 %. In the 90-day study period, the CDSS sent 302 notifications on 270 patients. Notifications were frequently inappropriate; 25 % had an expected platelet count decline (organ donation, stem cell transplant), an inaccurate count, or no heparin exposure. Patient testing for HIT prompted by the CDSS was not in accordance with best practice guidelines in most circumstances. For example, 36 % had a low probability 4Ts score, while 42 % with an intermediate or high probability 4Ts score were not tested. Due to concern for lack of efficacy, the CDSS was discontinued. Analysis of an 8-month period before and after discontinuation showed a significant decrease in the number of enzyme immunoassays ordered (547 vs. 386) without a change in the number of patients with HIT identified (13 vs. 13) or the rate of thrombosis in those with confirmed HIT (62 % vs. 62 %). In conclusion, a CDSS based on platelet count decline contributed to "alert fatigue" via inappropriate notification and did not improve evidence-based HIT testing. In addition, its removal did not decrease or delay HIT identification. Additional efforts are needed to better define how CDSS can support the rapid diagnosis and appropriate treatment of patients with HIT.

International Clinical Practice Guideline Recommendations for Acute Pulmonary Embolism: Harmony, Dissonance, and Silence

Despite abundant clinical innovation and burgeoning scientific investigation, pulmonary embolism (PE) has continued to pose a diagnostic and management challenge worldwide. Aging populations, patients living with a mounting number of chronic medical conditions, particularly cancer, and increasingly prevalent health care disparities herald a growing burden of PE. In the meantime, navigating expanding strategies for immediate and long-term anticoagulation, as well as advanced therapies, including catheter-based interventions for patients with more severe PE, has become progressively daunting. Accordingly, clinicians frequently turn to evidence-based clinical practice guidelines for diagnostic and management recommendations. However, numerous international guidelines, heterogeneity in recommendations, as well as areas of uncertainty or omission may leave the readers and clinicians without a clear management pathway. In this review of international PE guidelines, we highlight key areas of consistency, difference, and lack of recommendations (silence) with an emphasis on critical clinical and research needs.

Bivalirudin as an anticoagulation strategy for acute hemodialysis in children: Two cases with a summary of recent literature

Unfractionated heparin is the most used anticoagulative agent for extracorporeal settings in children, including acute hemodialysis modalities. In certain situations, such as heparin-induced thrombocytopenia, alternatives must be applied. The direct thrombin inhibitor bivalirudin has come forth as an attractive substitute. Bivalirudin is currently only approved for adult use in specific percutaneous coronary intervention settings. However, it has a growing off-label popularity in different contexts for both adult and pediatric patients. Experience with bivalirudin in children is mainly limited to extracorporeal membrane oxygenation, ventricular assist devices and during cardiopulmonary bypass surgery. Literature about its use as anticoagulation strategy for pediatric hemodialysis is very scarce. Here, we present two pediatric cases where bivalirudin was used during acute hemodialysis, followed by a short summary of recent literature.

Heparin-induced thrombocytopenia requiring VA-ECMO management during percutaneous coronary intervention for acute coronary syndrome: A case report

Heparin-induced thrombocytopenia (HIT) is an immune-mediated disease with severe thromboembolic complications. HIT during percutaneous coronary intervention (PCI) can be fatal without prompt treatment. We report an unusual case of HIT observed during PCI for acute coronary syndrome (ACS). A 74-year-old female with a history of pulmonary embolism managed with unfractionated heparin (UFH) 2 years previously presented with intermittent chest pain. Coronary angiography revealed total occlusion of the mid-right coronary artery. Before and during the primary PCI, 14000 UFH units were administered. However, abundant thrombus formation in the non-culprit lesion was refractory to repeated thrombus aspiration. We suspected HIT, discontinued UFH, and administered argatroban. Despite repeated thrombus aspirations and balloon dilatation, coronary obstruction persisted; consequently, ventricular fibrillation refractory to multiple cardioversions occurred. Therefore, veno-arterial extracorporeal membrane oxygenation (VA-ECMO) was required. Platelet counts rapidly decreased to <50 % of the baseline value, and serum was highly positive for IgG-specific antiplatelet factor 4/heparin antibodies. The patient was discharged with independent gait and no major neurological disorders. This is a clinically noteworthy case of rapidly developing HIT during primary PCI for ACS, requiring VA-ECMO management, with no major neurological complications. HIT may occur immediately after re-exposure to heparin long after the first exposure.

Learning objective

Without prompt treatment, heparin-induced thrombocytopenia (HIT) during percutaneous coronary intervention (PCI) can be fatal. It may lead to refractory coronary obstruction, which may need to be managed by veno-arterial extracorporeal membrane oxygenation (VA-ECMO). We present a clinically noteworthy case of rapidly developing HIT during primary PCI for acute coronary syndrome, requiring VA-ECMO management, with no major neurological complications. Physicians must be mindful that HIT may occur immediately after re-exposure to heparin long after the first exposure.

Venous Thromboembolism Prevention in Rehabilitation: A Review and Practice Suggestions

ABSTRACT

Venous thromboembolism is a frequent complication of acute hospital care, and this extends to inpatient rehabilitation. The timely use of appropriate thromboprophylaxis in patients who are at risk is a strong, evidence-based patient safety priority that has reduced clinically important venous thromboembolism, associated mortality and costs of care. While there has been extensive research on optimal approaches to venous thromboembolism prophylaxis in acute care, there is a paucity of high-quality evidence specific to patients in the rehabilitation setting, and there are no clinical practice guidelines that make recommendations for (or against) thromboprophylaxis across the broad spectrum of rehabilitation patients. Herein, we provide an evidence-informed review of the topic with practice suggestions. We conducted a series of literature searches to assess the risks of venous thromboembolism and its prevention related to inpatient rehabilitation as well as in major rehabilitation subgroups. Mobilization alone does not eliminate the risk of venous thromboembolism after another thrombotic insult. Low molecular weight heparins and direct oral anticoagulants are the principal current modalities of thromboprophylaxis. Based on the literature, we make suggestions for venous thromboembolism prevention and include an approach for consideration by rehabilitation units that can be aligned with local practice.

When Anticoagulation Backfires - Heparin-Induced Thrombocytopenia and Acute Stent Thrombosis following Endovascular Therapy for Deep Vein Thrombosis: A Case Report

We report a rare case of heparin-induced thrombocytopenia with thrombosis (HITT) following treatment for May-Thurner syndrome complicated by deep vein thrombosis (DVT), which resulted in venous stent thrombosis. A 27-year-old male with acute left lower-limb DVT successfully underwent thrombolysis and stenting for May-Thurner syndrome. However, the patient developed recurrent thrombosis and thrombocytopenia 3 days post-procedure. HITT was confirmed by a positive antiplatelet factor 4-heparin antibody test. After discontinuing heparin, the patient was successfully treated with fondaparinux, followed by repeat thrombectomy and thrombolysis, and then transitioned to warfarin. This is the second reported case of venous stent thrombosis due to HITT in May-Thurner syndrome. This case underscores the importance of early recognition and prompt management of HITT using alternative anticoagulants like fondaparinux to prevent complications such as venous limb gangrene. Further randomized controlled trials are required to evaluate the safety and efficacy of fondaparinux in HITT.

The efficacy and safety of direct oral anticoagulants in the treatment of the acute phase of heparin-induced thrombocytopenia: A systematic review

PURPOSE

To investigate the safety and efficacy of direct oral anticoagulants (DOACs) in the treatment of the acute phase of heparin-induced thrombocytopenia (HIT).

SUMMARY

A systematic review of the literature was conducted on PubMed, MEDLINE, Embase, and Web of Science Core Collection through July 2023. Search terms included "heparin-induced thrombocytopenia AND direct-oral-anticoagulants" in addition to a list of oral anticoagulants. Adult patients who used direct oral anticoagulants as the initial treatment for the acute phase of HIT were included. A total of 1,188 articles were initially identified, with 770 articles reviewed following removal of duplicates. Following the application of inclusion and exclusion criteria, 12 articles were ultimately included. Rivaroxaban was the most-utilized DOAC (28 patients), followed by apixaban (7 patients) and dabigatran (1 patient). All patients with thrombocytopenia demonstrated successful platelet recovery, with two patients presenting with normal platelet counts. One patient developed a deep venous thrombosis with no other new or recurrent thromboses. There were no reported clinically significant adverse events in any patient. Obstacles and deterrents to the use of the standards of care in the acute phase of HIT exist. Argatroban and bivalirudin require intravenous infusion and require close aPTT monitoring and dose adjustment. Fondaparinux requires injection and is contraindicated with body weight <50kg. DOACs would offer the novel ability for an oral treatment in the treatment of the acute phase HIT and allow for minimal monitoring and consistent dosing strategies. Therefore, DOACs are an intriguing choice for the treatment of the acute phase of HIT.

CONCLUSION

Data from 12 publications and across 36 patients suggests that the use of DOACs in the acute phase of HIT may be a safe and efficacious treatment option with favorable ease of monitoring and management.

Combination of 2 Quantitative Immunoassays and Clinical Score Algorithm to Reduce False-Negative Results in Heparin-Induced Thrombocytopenia: Prevalence Study of Mauriziano Hospital in Turin, Italy

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious adverse effect of heparin treatment caused by platelet-activating anti-platelet factor 4 (PF4)/heparin antibodies. Accurate diagnosis of HIT is essential but remains challenging. The aim of our study was to explore the performance of our optimized diagnostic laboratory algorithm, based on Chemiluminescence (CliA) and ELISA immunoassays, on suspected HIT patients. The study compared the prevalence of HIT diagnosis in A.O. Mauriziano with the literature.

METHODS

163 consecutive patients were investigated for suspected HIT with CliA HemosIL Acustar HIT-IgG, Werfen. HIT was ruled out in all patients with CliA <0.13 U/mL. All patients with CliA >0.13 U/mL were further investigated with Zymutest-HIA anti-PF4 IgG ELISA immunoassay. In these patients, HIT was ruled out on the combination of CliA between 0.13 and 1.0 U/mL followed by ELISA assay <0.300 OD. HIT was ruled in patients whose plasma tested positive or doubtful with CliA and positive with ELISA immunoassay and confirmed positive with a platelet aggregation test (PAT). Suspicion of HIT was revealed with clinical 4Ts score or recent suggestive anamnestic history.

RESULTS

Our diagnostic algorithm ruled out HIT diagnosis in 144/163 patients (88%) and predicted a positive PAT in 5/19 (26%) of CliA positive (4/5) or ELISA positive and CliA doubtful (1/5) patients.

CONCLUSIONS

Our prevalence was 3.1%, comparable with the literature. The approach combining 2 quantitative immunoassays' (CliA and ELISA) results and 4Ts score probability was able to rule out the diagnosis within 1 h in 66% of patients with suspected HIT and within 24 h in 88% of patients. In the remaining 12% of cases, management decisions have to be based on individualized judgment while awaiting functional confirming results (48-72 h).

Heparin-induced thrombocytopenia: a rare presentation with skin necrosis

Heparin-induced thrombocytopenia is the most clinically relevant non-hemorrhagic complication of heparin and is characterized by the presence of anti-platelet factor 4 (PF4)/heparinimmunoglobulin G (IgG) antibodies. The circulating PF4/heparinIgG immune complex binds to platelets via their FcyIIa receptors, activating them and promoting their aggregation, with consequent platelet consumption, thrombocytopenia, and thrombotic phenomena. Despite thrombocytopenia, this condition is not typically associated with bleeding complications. Instead, thrombosis is the most serious complication of heparin-induced thrombocytopenia, contributing to increased morbidity and mortality. Thrombotic events can be venous and arterial, such as deep vein thrombosis, pulmonary embolism, myocardial infarction, and thrombotic stroke. Skin necrosis at the site of heparin injections is a rare but well-described manifestation of heparin-induced thrombocytopenia. We report a case of heparin-induced thrombocytopenia presented as skin necrosis, highlighting the importance of recognizing this potentially fatal condition and the need for an immediate cessation of all sources of heparin and its replacement by other anticoagulants.

Anticoagulant therapy in renal insufficiency theme: Anticoagulation in complex situations

Many patients with impaired renal function have concurrent indications for anticoagulant therapy, including atrial fibrillation and venous thromboembolism. For mild chronic kidney disease, data from clinical trials and existing guidelines can be applied to clinical management. The benefits and harms of anticoagulation therapy in patients with more advanced renal impairment are nuanced, as both thrombotic and bleeding risk are increased. Until recently, data regarding anticoagulants in severe renal impairment were primarily observational, but emerging evidence includes a few small clinical trials and the emergence of novel agents hypothesized to have improved efficacy and safety in this population. In this review, we summarize existing data on anticoagulation in patients with chronic kidney disease. We suggest a framework for anticoagulation decision-making in the burgeoning worldwide population of patients with chronic kidney disease.

Association of Metal Cations with the Anti-PF4/Heparin Antibody Response in Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an antibody-mediated immune response against complexes of heparin and platelet factor 4 (PF4). The electrostatic interaction between heparin and PF4 is critical for the anti-PF4/heparin antibody response seen in HIT. The binding of metal cations to heparin induces conformational changes and charge neutralization of the heparin molecule, and cation-heparin binding can modulate the specificity and affinity for heparin-binding partners. However, the effects of metal cation binding to heparin in the context of anti-PF4/heparin antibody response have not been determined. Here, we utilized inductively coupled plasma mass spectrometry (ICP-MS) to quantify 16 metal cations in patient plasma and tested for correlation with anti-PF4/heparin IgG levels and platelet count after clinical suspicion of HIT in a cohort of heparin-treated patients. The average age of the cohort (n = 32) was 60.53 (SD = 14.31) years old, had a mean anti-PF4/heparin antibody optical density [OD405] of 0.93 (SD = 1.21) units, and was primarily female (n = 23). Patients with positive anti-PF4/heparin antibody test results (OD405 ≥ 0.5 units) were younger, had increased weight and BMI, and were more likely to have a positive serotonin release assay (SRA) result compared to antibody-negative patients. We observed statistical differences between antibody-positive and -negative groups for sodium and aluminum and significant correlations of anti-PF4/heparin antibody levels with sodium and silver. While differences in sodium concentrations were associated with antibody-positive status and correlated with antibody levels, no replication was performed. Additional studies are warranted to confirm our observed association, including in vitro binding studies and larger observational cohorts.

Heparin-induced thrombocytopenia with very high antibody titer is associated with slower platelet recovery and higher risk of thrombosis

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder mediated by platelet-activating antibodies targeting platelet factor 4 (PF4) and heparin complex. A higher antibody titer is reflected in a higher optical density (OD) by enzyme-linked immunosorbent assay for heparin-PF4 antibodies. This single-institution retrospective study of 116 HIT patients examined the effect of heparin-PF4 OD on time to platelet recovery, vascular thrombosis, and in-hospital mortality. Patients were divided into 3 cohorts based on heparin-PF4 OD: cohort 1 had an OD ≥ 2 and ≤ 2.4, cohort 2 had an OD > 2.4 and ≤ 2.8, and cohort 3 had an OD > 2.8. A higher OD titer was associated with significantly increased time to platelet recovery when compared between cohorts 1 versus 2 (HR = 0.599, p = 0.0221) and 1 versus 3 (HR = 0.515, p = 0.0014), as well as an increased risk of thrombosis (79.4%-cohort 3 vs 53.8%-cohort 2 vs 46.1%-cohort 1, p = 0.04), but had no impact on mortality (2.62-alive vs 2.65-deceased, p = 0.7432). A higher OD titer can inform risk assessment and support decision-making in HIT patients; however, prospective studies are needed to further clarify the impact of heparin-PF4 OD on outcomes.

Heparin Induced Thrombocytopenia Testing

This article provides a comprehensive overview of Heparin-Induced Thrombocytopenia (HIT) with an emphasis on laboratory testing and advantages of automation. HIT is a critical condition arising from heparin exposure, leading to a contradictory combination of thrombocytopenia with an increased thrombosis risk. The article discusses HIT's history, clinical presentation, laboratory diagnosis, and management strategies. It highlights the importance of interdisciplinary collaboration for effective diagnosis and treatment, underscoring advancements in technology and targeted therapies that are shaping future approaches to HIT management.

Management of Heparin-Induced Thrombocytopenia: A Contemporary Review

Heparin-induced thrombocytopenia (HIT) is a life- and limb-threatening immune-mediated emergency classically associated with heparin therapy. This review focuses on type II HIT, characterized by the development of antibodies against platelet-factor 4 (PF4) bound to heparin after exposure, causing life-threatening thrombocytopenia, arterial thrombosis, and/or venous thrombosis. The high morbidity and mortality rates emphasize the need for early recognition and urgent intervention with discontinuation of heparin and initiation of non-heparin anticoagulation. We discuss the management of HIT with an emphasis on recent developments: (i) incorporating the phases of HIT (i.e., suspected, acute, subacute A and B, and remote) into its management, categorized according to platelet count, immunoassay, and functional assay results and (ii) direct-acting oral anticoagulants (DOACs), which are increasingly used in appropriate cases of acute HIT (off-label). In comparison to parenteral options (e.g., bivalirudin and danaparoid), they are easier to administer, are more cost-effective, and obviate the need for transition to an oral anticoagulant after platelet recovery. We also identify the knowledge gaps and suggest areas for future research.

An ISHLT consensus statement on strategies to prevent and manage hemocompatibility related adverse events in patients with a durable, continuous-flow ventricular assist device

Life expectancy of patients with a durable, continuous-flow left ventricular assist device (CF-LVAD) continues to increase. Despite significant improvements in the delivery of care for patients with these devices, hemocompatability-related adverse events (HRAEs) are still a concern and contribute to significant morbility and mortality when they occur. As such, dissemination of current best evidence and practices is of critical importance. This ISHLT Consensus Statement is a summative assessment of the current literature on prevention and management of HRAEs through optimal management of oral anticoagulant and antiplatelet medications, parenteral anticoagulant medications, management of patients at high risk for HRAEs and those experiencing thrombotic or bleeding events, and device management outside of antithrombotic medications. This document is intended to assist clinicians caring for patients with a CF-LVAD provide the best care possible with respect to prevention and management of these events.

Flow cytometry vs conventional methods for the evaluation of anti-PF4/heparin antibodies: a single center study

Aim: Heparin-induced thrombocytopenia (HIT) is a rare, life-threatening, immune-mediated adverse effect of heparin administration. This study compares frequently used laboratory assays in terms of their effectiveness in HIT diagnosis.Materials & methods: Fifty patients with suspected HIT were tested by gel immunoassay and solid phase PF4/heparin antibody ELISA. On positive results, platelet activation markers P-selectin and Annexin V were assayed using flow cytometry.Results: Thirty/50 patients were negative for both immunoassays. Flow cytometry was performed in the 20 immunoassay positive patients. Platelet activation was observed in 7/20 in the presence of low heparin concentration (0.2 IU/ml).Conclusion: The results are in accordance with the currently available literature and flow cytometry seems a promising alternative in HIT laboratory investigation.

DrugRepoBank: a comprehensive database and discovery platform for accelerating drug repositioning

In recent years, drug repositioning has emerged as a promising alternative to the time-consuming, expensive and risky process of developing new drugs for diseases. However, the current database for drug repositioning faces several issues, including insufficient data volume, restricted data types, algorithm inaccuracies resulting from the neglect of multidimensional or heterogeneous data, a lack of systematic organization of literature data associated with drug repositioning, limited analytical capabilities and user-unfriendly webpage interfaces. Hence, we have established the first all-encompassing database called DrugRepoBank, consisting of two main modules: the 'Literature' module and the 'Prediction' module. The 'Literature' module serves as the largest repository of literature-supported drug repositioning data with experimental evidence, encompassing 169 repositioned drugs from 134 articles from 1 January 2000 to 1 July 2023. The 'Prediction' module employs 18 efficient algorithms, including similarity-based, artificial-intelligence-based, signature-based and network-based methods to predict repositioned drug candidates. The DrugRepoBank features an interactive and user-friendly web interface and offers comprehensive functionalities such as bioinformatics analysis of disease signatures. When users provide information about a drug, target or disease of interest, DrugRepoBank offers new indications and targets for the drug, proposes new drugs that bind to the target or suggests potential drugs for the queried disease. Additionally, it provides basic information about drugs, targets or diseases, along with supporting literature. We utilize three case studies to demonstrate the feasibility and effectiveness of predictively repositioned drugs within DrugRepoBank. The establishment of the DrugRepoBank database will significantly accelerate the pace of drug repositioning. Database URL:  https://awi.cuhk.edu.cn/DrugRepoBank.

Electronic consultation to improve care outcomes in patients with suspected and confirmed heparin-induced thrombocytopenia

Background

Heparin-induced thrombocytopenia (HIT) is a complication of heparin exposure associated with high risk for morbidity and mortality. Diagnosis and management are complex due to limitations of laboratory testing and the need for nonheparin anticoagulation.

Objectives

To increase the delivery of evidence-based care of patients with suspected and confirmed HIT via electronic consultation (e-consult).

Methods

We describe the creation and implementation of an e-consult service for patients with concern for HIT at a large academic medical center. Hematology physicians with HIT expertise performed real-time chart review of all patients with a positive screening immunoassay result and provided written recommendations in their electronic health record.

Results

Comparison of outcomes for 1 year before and the year after the e-consult service implementation identified improvements in direct thrombin inhibitor stewardship, increased diagnostic accuracy, and decreased length of stay of patients with confirmed HIT.

Conclusion

The e-consult platform is a novel method for rapid, targeted consultative guidance, and this single-institution pilot demonstrates its feasibility and effectiveness to improve the care of patients with suspected and confirmed HIT.

Heparin-Induced Thrombocytopenia in Patients Suffering Cardiogenic Shock

OBJECTIVES

Cardiogenic shock (CS) is associated with high mortality. Patients treated for CS mostly require heparin therapy, which may be associated with complications such as heparin-induced thrombocytopenia (HIT). HIT represents a serious condition associated with platelet decline and increased hypercoagulability and remains a poorly researched field in intensive care medicine. Primary purpose of this study was to: 1) determine HIT prevalence in CS, 2) assess the performance of common diagnostic tests for the workup of HIT, and 3) compare outcomes in CS patients with excluded and confirmed HIT.

DESIGN

Retrospective dual-center study including adult patients 18 years old or older with diagnosed CS and suspected HIT from January 2010 to November 2022.

SETTING

Cardiac ICU at the Ludwig-Maximilians University hospital in Munich and the university hospital of Bonn.

PATIENTS AND INTERVENTIONS

In this retrospective analysis, adult patients with diagnosed CS and suspected HIT were included. Differences in baseline characteristics, mortality, neurologic and safety outcomes between patients with excluded and confirmed HIT were evaluated.

MEASUREMENTS AND MAIN RESULTS

In cases of suspected HIT, positive screening antibodies were detected in 159 of 2808 patients (5.7%). HIT was confirmed via positive functional assay in 57 of 2808 patients, corresponding to a prevalence rate of 2.0%. The positive predictive value for anti-platelet factor 4/heparin screening antibodies was 35.8%. Total in-hospital mortality (58.8% vs. 57.9%; p > 0.999), 1-month mortality (47.1% vs. 43.9%; p = 0.781), and 12-month mortality (58.8% vs. 59.6%; p > 0.999) were similar between patients with excluded and confirmed HIT, respectively. Furthermore, no significant difference in neurologic outcome among survivors was found between groups (Cerebral Performance Category [CPC] score 1: 8.8% vs. 8.8%; p > 0.999 and CPC 2: 7.8% vs. 12.3%; p = 0.485).

CONCLUSIONS

HIT was a rare complication in CS patients treated with unfractionated heparin and was not associated with increased mortality. Also, HIT confirmation was not associated with worse neurologic outcome in survivors. Future studies should aim at developing more precise, standardized, and cost-effective strategies to diagnose HIT and prevent complications.

Cost-Effectiveness and Return on Investment Analysis of an In-house HemosIL Heparin-Induced Thrombocytopenia Antibody Assay at a Mid-Sized Institution

CONTEXT.—

Laboratories face the challenge of providing quality patient care while managing costs and turnaround times (TATs). To this end, we brought the heparin-induced thrombocytopenia (HIT) antibody test in-house with the goal of reducing costs and the time to diagnosis.

OBJECTIVES.—

To determine the cost-effectiveness and return on investment of our in-house HIT antibody test by comparing it to send-out assays with TATs of 2, 3, or 4 days.

DESIGN.—

We performed a retrospective chart review of all patients with a HIT antibody assay and analysis of laboratory financial records. Analysis included the percentage of patients receiving alternative treatment, cost of treatment, startup costs of bringing the test in-house, and average TAT of the in-house test.

RESULTS.—

We found significant reductions in the cost of treatment for patients and the overall cost to the health care system. The in-house assay became cost-effective at between 8 and 20 tests, with a return on investment of up to 298%.

CONCLUSIONS.—

Bringing the HIT antibody assay in-house becomes cost-effective at a very low test volume with excellent return on investment. This novel analysis can provide a framework for other laboratory medicine professionals to analyze the benefits of bringing this and other assays in-house.

Limb Ischemic Necrosis Secondary to Microvascular Thrombosis: A Brief Historical Review

Ischemic limb injury can be broadly classified into arterial (absent pulses) and venous/microvascular (detectable pulses); the latter can be divided into two overlapping disorders-venous limb gangrene (VLG) and symmetrical peripheral gangrene (SPG). Both VLG and SPG feature predominant acral (distal) extremity ischemic necrosis, although in some instances, concomitant nonacral ischemia/skin necrosis occurs. Historically, for coagulopathic disorders with prominent nonacral ischemic necrosis, clinician-scientists implicated depletion of natural anticoagulants, especially involving the protein C (PC) system. This historical review traces the recognition of natural anticoagulant depletion as a key feature of nonacral ischemic syndromes, such as classic warfarin-induced skin necrosis, neonatal purpura fulminans (PF), and meningococcemia-associated PF. However, only after several decades was it recognized that natural anticoagulant depletion is also a key feature of predominantly acral ischemic microthrombosis syndromes-VLG and SPG-even when accompanying nonacral thrombosis is not present. These acquired acral limb ischemic syndromes typically involve the triad of (a) disseminated intravascular coagulation, (b) natural anticoagulant depletion, and (c) a localizing explanation for microthrombosis occurring in one or more limbs, either deep vein thrombosis (helping to explain VLG) or circulatory shock (helping to explain SPG). In most cases of VLG or SPG there are one or more events that exacerbate natural anticoagulant depletion, such as warfarin therapy (e.g., warfarin-associated VLG complicating heparin-induced thrombocytopenia or cancer hypercoagulability) or acute ischemic hepatitis ("shock liver") as a proximate factor predisposing to severe depletion of hepatically synthesized natural anticoagulants (PC, antithrombin) in the setting of circulatory shock.

Heparin-Induced Thrombocytopenia After Revascularization of Gustilo-Anderson Type IIIC Open Lower Leg Fracture: A Case Report of Subsequent Ischemic Limb Salvage Failure

BACKGROUND Heparin-induced thrombocytopenia (HIT) is a disease in which the immune response elicited by heparin results in a state of hypercoagulability and platelet activation, leading to thrombocytopenia and thromboembolism. Gustilo-Anderson type IIIC open fractures of the extremities are defined as open fractures presenting with arterial injuries that require repair and result in treatment challenges and complications. The diagnosis of HIT can be difficult in patients with severe trauma with consumptive thrombocytopenia associated with heavy bleeding and the use of heparin after vascular anastomosis. CASE REPORT A 48-year-old man was injured in a car accident, pinching his right lower leg and sustaining a Gustilo-Anderson type IIIc open fracture, for which he underwent emergency revascularization surgery. Heparin was administered continuously immediately after the surgery. On postoperative day 9, ischemic changes were observed in the right foot, and we performed suture re-anastomosis; however, the blood circulation in the right lower leg did not resume, and right lower leg amputation was performed due to ischemic necrosis with the onset of HIT. Postoperatively, the patient was switched to edoxaban after the recovery of his platelet count. Thereafter, the patient experienced no new thrombus occlusion or wound trouble, and was able to walk on a prosthetic leg and return to daily life. CONCLUSIONS It is important to consider the possibility of HIT as soon as thrombocytopenia appears in patients with Gustilo-Anderson type IIIC open fracture who are receiving heparin after vascular anastomosis, as a delayed diagnosis of HIT can make it difficult to save the limb.