Heparin-Induced Thrombocytopenia: A Comprehensive Clinical Review

Inhaled heparin: Past, present, and future

While heparin has traditionally served as a key anticoagulant in clinical practice for nearly a century, recent years have witnessed a growing interest in its role as a potent antiinflammatory and antiviral agent, as well as an anticancer agent. To address challenges with injection-based delivery, exploring patient-friendly routes such as oral and pulmonary delivery is crucial. This review specifically highlights the multiple therapeutic benefits of inhaled heparin. In summary, this review serves as a valuable source of information, providing deep insights into the diverse therapeutic advantages of inhaled heparin and its potential applications within clinical contexts.

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.

Heparin-induced thrombocytopenia in extracorporeal membrane oxygenation-supported patients: a systematic review and meta-analysis

BACKGROUND

In recent years, extracorporeal membrane oxygenation (ECMO) has been increasingly used in critically ill patients with respiratory or cardiac failure. Heparin is usually used as anticoagulation therapy during ECMO support. However, heparin-induced thrombocytopenia (HIT) in ECMO-supported patients, which results in considerable morbidity and mortality, has not yet been well described. This meta-analysis and systematic review aimed to thoroughly report the incidence of HIT on ECMO, as well as the characteristics and outcomes of HIT patients.

METHODS

We searched the PubMed, Embase, Cochrane Library, and Scopus databases for studies investigating HIT in adult patients supported by ECMO. All studies conforming to the inclusion criteria were screened from 1975 to August 2023. Nineteen studies from a total of 1,625 abstracts were selected. The primary outcomes were the incidence of HIT and suspected HIT.

RESULTS

The pooled incidence of HIT in ECMO-supported patients was 4.2% (95% CI: 2.7-5.6; 18 studies). A total of 15.9% (95% CI: 9.0-22.8; 12 studies) of patients on ECMO were suspected of having HIT. Enzyme-linked immunosorbent assay (ELISA) is the most commonly used immunoassay. The median optical density (OD) of the ELISA in HIT-confirmed patients ranged from 1.08 to 2.10. In most studies, the serotonin release assay (SRA) was performed as a HIT-confirming test. According to the subgroup analysis, the pooled incidence of HIT in ECMO patients was 2.7% in studies whose diagnostic mode was functional assays, which is significantly lower than the incidence in studies in which the patients were diagnosed by immunoassay (14.5%). Argatroban was most commonly used as an alternative anticoagulation agent after the withdrawal of heparin. Among confirmed HIT patients, 45.5% (95% CI: 28.8-62.6) experienced thrombotic events, while 50.1% (95% CI: 24.9-75.4) experienced bleeding events. Overall, 46.6% (95% CI: 30.4-63.1) of patients on ECMO with HIT died.

CONCLUSION

According to our study, the pooled incidence of HIT in ECMO-supported patients is 4.2%, and it contributes to adverse outcomes. Inappropriate diagnostic methods can easily lead to misdiagnosis of HIT. Further research and development of diagnostic algorithms and laboratory assays are warranted.

Bivalirudin as a substitute for heparin in neurointervention for patients with heparin-induced thrombocytopenia

OBJECTIVES

Heparin-induced thrombocytopenia is a known complication of heparin exposure with potentially life-threatening sequelae. Direct thrombin inhibitors can be substituted for heparin in patients with heparin-induced thrombocytopenia that require anticoagulation. However, the use of direct thrombin inhibitors as a substitute for heparin has not been widely reported in the neuroendovascular literature.

MATERIALS AND METHODS

Here we report the first use of the direct thrombin inhibitor bivalirudin in a neuroendovascular procedure as a substitute for heparin in a patient with a ruptured pseudoaneurysm and heparin-induced thrombocytopenia, and review the literature on the use of bivalirudin and argatroban for such patients.

RESULTS

Bivalirudin was safely and effectively used in the case reported, with no thrombotic or hemorrhagic complications. Our literature review revealed a paucity of studies on the use of heparin alternatives, including bivalirudin, in neuroendovascular procedures in patients with heparin-induced thrombocytopenia.

CONCLUSIONS

Heparin-induced thrombocytopenia is an important iatrogenic disease process in patients undergoing neuroendovascular procedures, and developing protocols to diagnose and manage heparin-induced thrombocytopenia is important for healthcare systems. While further research needs to be done to establish the full range of anticoagulation options to substitute for heparin, our case indicates bivalirudin as a potential candidate.

Anti-PF4 ELISA-Negative, SRA-Positive Heparin-Induced Thrombocytopenia

Heparin products are frequently used in the inpatient setting to prevent and treat venous thromboembolism, but they simultaneously put patients at risk of developing heparin-induced thrombocytopenia (HIT). The 4Ts score determines the pretest probability of HIT. Diagnosis is made with a screening antiplatelet factor (PF4) immunoassay and the serotonin-release assay (SRA) as a confirmatory test. Anti-PF4 assays have high sensitivity (98%) but lower specificity (50%) and result in frequent false-positive tests. We present a rare case from our institution of a patient with anti-PF4-Polyanion ELISA-negative, SRA-positive HIT and describe the challenges in making a timely diagnosis in this case.

An Updated Comprehensive Pharmacovigilance Study of Drug-Induced Thrombocytopenia Based on FDA Adverse Event Reporting System Data

Drug-induced thrombocytopenia (DIT) deserves both clinical and research attention for the serious clinical consequences and high prevalence of the condition. The current study aimed to perform a comprehensive pharmacovigilance analysis of DIT reported in the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) database, with a particular focus on drugs associated with thrombocytopenia events. A disproportionality analysis of DIT was conducted using reports submitted to FARES from January 2004 to December 2022. Both the information component (IC) and reporting odds ratio (ROR) algorithms were applied to identify an association between target drugs and DIT events. A total of 15,940,383 cases were gathered in FAERS, 168,657 of which were related to DIT events. The top 50 drugs ranked by number of cases and ranked by signal strength were documented. The top 5 drugs ranked by number of cases were lenalidomide (10,601 cases), niraparib (3726 cases), ruxolitinib (3624 cases), eltrombopag (3483 cases), and heparin (3478 cases). The top 5 drugs ranked by signal strength were danaparoid (ROR 37.61, 95%CI 30.46-46.45), eptifibatide (ROR 34.75, 95%CI 30.65-39.4), inotersen (ROR 34.00, 95%CI 29.47-39.23), niraparib (ROR 30.53, 95%CI 29.42-31.69), and heparin (ROR 28.84, 95%CI 27.76-29.97). The top 3 involved drug groups were protein kinase inhibitors, antimetabolites, and monoclonal antibodies and antibody-drug conjugates. The current comprehensive pharmacovigilance study identified more drugs associated with thrombocytopenia. Although the mechanisms of DIT have been elucidated for some drugs, others still require further investigation.

In situ formed depot of elastin-like polypeptide-hirudin fusion protein for long-acting antithrombotic therapy

Thrombosis, induced by abnormal coagulation or fibrinolytic systems, is the most common pathology associated with many life-threatening cardio-cerebrovascular diseases. However, first-line anticoagulant drugs suffer from rapid drug elimination and risk of hemorrhagic complications. Here, we developed an in situ formed depot of elastin-like polypeptide (ELP)-hirudin fusion protein with a prodrug-like feature for long-term antithrombotic therapy. Highly secretory expression of the fusion protein was achieved with the assistance of the Ffu312 tag. Integration of hirudin, ELP, and responsive moiety can customize fusion proteins with properties of adjustable in vivo retention and controllable recovery of drug bioactivity. After subcutaneous injection, the fusion protein can form a reservoir through temperature-induced coacervation of ELP and slowly diffuse into the blood circulation. The biological activity of hirudin is shielded due to the N-terminal modification, while the activated key proteases upon thrombus occurrence trigger the cleavage of fusion protein together with the release of hirudin, which has antithrombotic activity to counteract thrombosis. We substantiated that the optimized fusion protein produced long-term antithrombotic effects without the risk of bleeding in multiple animal thrombosis models.

Acute coronary thrombosis due to heparin-induced thrombocytopenia following improved COVID-19 pneumonia: A case report

A 45-year-old male with anteroseptal myocardial infarction was referred to our hospital. The patient was previously admitted to another hospital with coronavirus disease-2019 pneumonia for 2 weeks; he was discharged 2 weeks before presentation to our institution. He received conventional treatment for coronavirus disease-2019, including administration of heparin. A moderate decrease in platelet count was observed on admission, and emergent angiography was performed under a definitive diagnosis of acute coronary syndrome. The angiography revealed occlusion of the left anterior descending artery. Percutaneous coronary intervention was performed; however, the occlusion did not improve owing to persistent thrombosis in the distal left anterior descending artery. Therefore, we induced intra-aortic balloon pumping to improve coronary blood flow and obtained Thrombolysis in Myocardial Infarction grade 2 flow. Following percutaneous coronary intervention, we detected a further decrease in platelets and positivity for heparin-induced thrombocytopenia antibody, leading to the diagnosis of heparin-induced thrombocytopenia. Subsequently, oral anticoagulation was introduced, and the symptoms did not recur.

Learning objective

Treatment with heparin is indicated for patients with coronavirus disease-2019 (COVID-19) because of derangement of the coagulation system. However, this approach contributes to the development of heparin-induced thrombocytopenia (HIT). We report a case of acute coronary syndrome due to HIT with COVID-19. HIT is commonly reported in patients with COVID-19. Thus, attentive monitoring of the platelet count and considering the possibility of HIT are indispensable when treating acute coronary syndrome in patients with previous history of COVID-19.

Heparin-Induced Thrombocytopenia After Cardiac Surgery-A Statewide Review of Health Care Utilization

BACKGROUND

Despite its severe consequences, clinical and economic impacts of heparin-induced thrombocytopenia (HIT) after cardiac operations have not been well characterized. This study assessed statewide incidence, outcomes, and resource consumption associated with HIT after cardiac operations.

METHODS

This was a retrospective investigation of cardiac surgery patients using the Maryland Health Services Cost Review Commission's database from 2012 to 2020. Health care costs, utilization, and outcomes for those who experienced postoperative HIT were compared with propensity score-matched controls.

RESULTS

Of 33 583 cardiac surgery patients, 184 (0.55%) were diagnosed with postoperative HIT. Compared with non-HIT patients, HIT patients were significantly more likely to be in the oldest age group (>80 years; P < .001) and to have greater severity of illness at admission (P < .001). HIT was associated with a longer hospitalization (21 vs 7 days; P < .001), greater mortality (13.6% vs 2.3%; P < .001), and greater hospital charges ($123 160 vs $45 303; P < .001), even after propensity score matching. Readmission rates were not significantly different, however, and readmission hospital charges did not significantly differ between HIT and non-HIT patients.

CONCLUSIONS

In addition to worse outcomes, HIT was associated with higher costs during index admissions but not during readmissions of cardiac surgery patients. Strategies to minimize HIT could yield better outcomes and reduced costs, particularly relevant for health care systems seeking improved value-based care while reducing unnecessary hospitalizations.

Untoward immune effects of modern medication

Immune-related adverse events (irAEs) represent an increasingly concerning challenge in the assessment of biopharmaceutical products. In contrast to historically rare allergic reactions associated with small chemical drugs, contemporary biotherapeutics exhibit a significantly higher morbidity of irAEs, because of their complex structure and comprehensive mechanisms of action. While the immunogenicity of protein-based compounds is associated with the induction of anti-drug antibodies, the pathogenesis of irAEs in advanced biologics, such as cell and gene therapy, remains to be further delineated. In the current study, I present an updated profile regarding the untoward immune effects of medications, covering various material categories systematically, with the underlying mechanisms to inspire risk mitigation in biopharmaceutical development and application.

Bivalirudin anticoagulation for cardiopulmonary bypass during cardiac surgery

INTRODUCTION

Heparin is the primary anticoagulant for cardiopulmonary bypass (CPB) support during cardiac surgery. While widely used, ∼2% of cardiac surgery patients develop heparin-induced thrombocytopenia (HIT) and 4-26% develop heparin resistance. Bivalirudin is an alternative anticoagulant mainly used for percutaneous coronary interventions. Given the challenges associated with heparin anticoagulation, we conducted a review to explore the use of bivalirudin for CPB surgery.

METHODS

PubMed and Embase scoping review included 2 randomized controlled trials, a retrospective comparison study, 3 pilot studies, and 30 case reports. To provide a contemporary series, we searched for articles published from 2010 to 2023. Our review included studies from both adult and pediatric populations.

RESULTS

While data is limited, bivalirudin seems to supply similar effectiveness and safety as heparin for CPB anticoagulation. Across the three comparative studies, the heparin cohorts had a 0-9% mortality rate and 0-27% rate of major bleeding/reoperation compared to a 0-3% mortality and 0-6% major bleeding/reoperation rate for the bivalirudin cohorts. Bivalirudin was successfully used as an anticoagulant in a wide range of CPB surgeries (e.g., heart transplants, ventricular assisted device placements, and valve repairs). Successful patient outcomes were reported with bivalirudin infusion of ∼2 mg/kg/hour, activated clotting time monitoring (target >400 s or 2.5× baseline), use of cardiotomy suctions, minimization of stagnant blood, and post-bypass modified ultrafiltration.

CONCLUSION

Bivalirudin is a safe and effective anticoagulant for CPB, especially for patients with HIT or heparin resistance. Further comparative research is called for to optimize bivalirudin utilization for CPB during cardiac surgery.

The Impact of an Antithrombotic Stewardship Program on Heparin-Induced Thrombocytopenia Management

Background: An antithrombotic stewardship program was implemented to reduce IV DTI use and increase fondaparinux and direct oral anticoagulant (DOAC) use for suspected or confirmed Heparin-induced thrombocytopenia (HIT). Objectives: This study evaluated the impact of an antithrombotic stewardship program on IV DTI utilization in patients with HIT. Methods: A retrospective analysis of adults receiving IV DTIs or fondaparinux from July 2016 to July 2017 (pre-stewardship) and October 2017 to July 2019 (post-stewardship) was conducted. Results: The median duration of IV DTI administration was not significantly different in HIT-negative patients between the pre- and post-stewardship cohorts (1.6 days (25th percentile (p25), 75th percentile (p75): .5, 3.3) vs 1.7 days (p25, p75: .9, 3.9), P = .31). The median duration of IV DTI administration in HIT-positive patients was 9.9 days (p25, p75: 7.6, 21.0) pre-stewardship and 7.3 days (p25, p75: 4.8, 16.5) post-stewardship (P = .18). For HIT-positive patients, the time from HIT diagnosis to discharge was 12.8 days (p25, p75: 8.9, 24.9) and 9.2 days (p25, p75: 4.0, 18.1) in the pre- and post-stewardship cohorts, respectively (P = .07). Fondaparinux and DOAC prescribing rates were 40.7% and 62.2% in the pre- and post-stewardship cohorts, respectively (P = .09). The percentage of patients with no contraindications to IV DTI alternatives receiving these agents increased from 31.2% to 78.6% (P = .01) following stewardship implementation. Conclusions: Intravenous DTI alternative utilization increased significantly after stewardship implementation. Stewardship implementation was associated with a non-statistically significant trend towards decreased IV DTI utilization and decreased length of stay for HIT-positive patients.

A Functional Assay for the Determination of Heparin-Induced Thrombocytopenia via Flow Cytometry

Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin therapy (both unfractionated heparin and low-molecular-weight heparin). In our study, we examined a group of 122 patients with suspected HIT. The samples of all patients were analyzed in the first step using an immunoassay (ID-PaGIA Heparin/PF4, Hemos1L-Acustar HIT IgG, ZYMUTEST HIA Monostrip IgG) to detect the presence of antibodies against heparin-PF4 complexes (platelet factor 4). When the immunoassay was positive, the sample was subsequently analyzed for HIT with a functional flow cytometry assay, the HITAlert kit, the purpose of which was to demonstrate the ability of the antibodies present to activate platelets. A diagnosis of HIT can be made only after a positive functional test result. In this article, we present an overview of our practical experience with the use of the new functional method of analysis, HIT, with flow cytometry. In this work, we compared the mutual sensitivity of two functional tests, SRA and the flow cytometry HITAlert kit, in patients perceived as being at risk for HIT. This work aims to delineate the principle, procedure, advantages, pitfalls, and possibilities of the application of the functional test HITAlert using flow cytometry.

Bivalirudin in acute coronary syndromes

INTRODUCTION

Bivalirudin, a bivalent direct thrombin inhibitor, has been developed to reduce bleeding without any trade-off in thrombotic events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI).

AREAS COVERED

Despite showing a superior safety profile compared with unfractionated heparin (UFH), bivalirudin is not considered the anticoagulant of choice in ACS patients undergoing PCI, mainly because of an increased rate of acute stent thrombosis (ST) shown by several randomized controlled trials (RCTs), in addition to limited availability in certain countries and increased costs. However, RCTs on bivalirudin have been characterized by several confounding factors hindering the interpretation of its safety and efficacy compared with UFH among the spectrum of ACS patients. Furthermore, a significant body of evidence has demonstrated that the risk of acute ST can be mitigated by a full-dose infusion regimen following PCI, without compromising the favorable safety profile compared to UFH.

EXPERT OPINION

In light of the increased understanding of the prognostic relevance of bleeding events and the excellent safety profile of bivalirudin, recent trial evidence may allow for this anticoagulant agent to reemerge and have a more prominent role in the management of ACS patients undergoing PCI.

Prevalence and outcomes of heparin-induced thrombocytopenia in hospitalized patients with venous thromboembolic disease: Insight from national inpatient sample

OBJECTIVE

The mainstay of therapy for patients with venous thromboembolic disease (VTE) is anticoagulation. In the inpatient setting, majority of these patients are treated with heparin or low molecular weight heparin. The prevalence and outcomes of heparin-induced thrombocytopenia (HIT) in hospitalized patients with venous thromboembolic disease (VTE) is unknown.

METHODS

This nationwide study identified patients with VTE from the National Inpatient Sample database between January 2009 and December 2013. Among these patients, we compared in-hospital outcomes of patients with and without HIT using a propensity score-matching algorithm. The primary outcome was in-hospital mortality. Secondary outcomes included rates of blood transfusions, intracranial hemorrhage, gastrointestinal bleed, length of hospital stay, and total hospital charges.

RESULTS

Among 791,932 hospitalized patients with VTE, 4948 patients (0.6%) were noted to have HIT (mean age, 62.9 ±16.2 years; 50.1% female). Propensity-matched comparison showed higher rates of in-hospital mortality (11.01% vs 8.97%; P < .001) and blood transfusions (27.20% vs 20.23%; P < .001) in patients with HIT compared with those without HIT. No significant differences were noted in intracranial hemorrhage rates (0.71% vs 0.51%; P > .05), gastrointestinal bleed (2.00% vs 2.22%; P > .05), length of hospital stay (median, 6.0 days; interquartile range [IQR], 3.0-11.0 vs median, 6.0 days; IQR, 3.0-10.0 days; P > .05), and total hospital charges (median, $36,325; IQR, $17,798-$80,907 vs median, $34,808; IQR, $17,654-$75,624; P > .05).

CONCLUSIONS

This nationwide observational study showed that 0.6% of hospitalized patients with VTE in the United States have HIT. The presence of HIT was associated with higher in-hospital mortality and blood transfusion rates compared with those without HIT.

Heparin-based versus bivalirudin-based anticoagulation in pediatric extracorporeal membrane oxygenation: A systematic review

Introduction

Optimal anticoagulation therapy is essential for the prevention of thrombotic and hemorrhagic complications in pediatric patients supported with extracorporeal membrane oxygenation (ECMO). Recent data have demonstrated bivalirudin has the potential to surpass and replace heparin as the anticoagulant of choice.

Methods

We conducted a systematic review comparing the outcomes of heparin-based versus bivalirudin-based anticoagulation in pediatric patients supported on ECMO to identify the preferred anticoagulant to minimize bleeding events, thrombotic complications, and associated mortality. We referenced the PubMed, Cochrane Library, and Embase databases. These databases were searched from inception through October 2022. Our initial search identified 422 studies. All records were screened by two independent reviewers using the Covidence software for adherence to our inclusion criteria, and seven retrospective cohort studies were identified as appropriate for inclusion.

Results

In total, 196 pediatric patients were anticoagulated with heparin and 117 were anticoagulated with bivalirudin while on ECMO. Across the included studies, it was found that for patients treated with bivalirudin, trends were noted toward lower rates of bleeding, transfusion requirements, and thrombosis with no difference in mortality. Overall costs associated with bivalirudin therapy were lower. Time to therapeutic anticoagulation varied between studies though institutions had different anticoagulation targets.

Conclusion

Bivalirudin may be a safe, cost-effective alternative to heparin in achieving anticoagulation in pediatric ECMO patients. Prospective multicenter studies and randomized control trials with standard anticoagulation targets are needed to accurately compare outcomes associated with heparin versus bivalirudin in pediatric ECMO patients.

Ventricular septal rupture after acute myocardial infarction in a patient with venous thromboembolism complicated by thrombocytopenia: A case report

A woman that suffered burns previously presented with leg swelling and was diagnosed with venous thromboembolism. Heparin was given until she suddenly developed myocardial infarction. Ventricular septal rupture was detected and managed by transcatheter closure. She developed massive bleeding and extensive thrombosis that made treatment paradoxical and eventually died.

How to Solve the Conundrum of Heparin-Induced Thrombocytopenia during Cardiopulmonary Bypass

Heparin-induced thrombocytopenia (HIT) is a major issue in cardiac surgery requiring cardiopulmonary bypass (CPB). HIT represents a severe adverse drug reaction after heparin administration. It consists of immune-mediated thrombocytopenia paradoxically leading to thrombotic events. Detection of antibodies against platelets factor 4/heparin (anti-PF4/H) and aggregation of platelets in the presence of heparin in functional in vitro tests confirm the diagnosis. Patients suffering from HIT and requiring cardiac surgery are at high risk of lethal complications and present specific challenges. Four distinct phases are described in the usual HIT timeline, and the anticoagulation strategy chosen for CPB depends on the phase in which the patient is categorized. In this sense, we developed an institutional protocol covering each phase. It consisted of the use of a non-heparin anticoagulant such as bivalirudin, or the association of unfractionated heparin (UFH) with a potent antiplatelet drug such as tirofiban or cangrelor. Temporary reduction of anti-PF4 with intravenous immunoglobulins (IvIg) has recently been described as a complementary strategy. In this article, we briefly described the pathophysiology of HIT and focused on the various strategies that can be applied to safely manage CPB in these patients.

Heparin-Induced Thrombocytopenia in Patients Undergoing Venoarterial Extracorporeal Membrane Oxygenation

Background: Heparin-induced thrombocytopenia (HIT) is a serious, immune-mediated adverse drug reaction to unfractionated heparin (UFH) affecting also patients undergoing venoarterial extracorporeal membrane oxygenation (VA-ECMO). Although the association between VA-ECMO support and the development of thrombocytopenia has long been known and discussed, HIT as one underlying cause is still insufficiently understood. Therefore, the purpose of this study was to further investigate the epidemiology, mortality, diagnosis, and clinical management of HIT occurring in VA-ECMO patients treated with UFH. Methods: We conducted a retrospective single-center study including adult patients (≥18 years) with VA-ECMO support in the cardiac intensive care unit (ICU) of the University Hospital of Munich (LMU) between January 2013 and May 2022, excluding patients with a known history of HIT upon admission. Differences in baseline characteristics and clinical outcome between excluded HIT (positive anti-platelet factor 4 (PF4)/heparin antibody test but negative functional assay) and confirmed HIT (positive anti-PF4/heparin antibody test and positive functional assay) VA-ECMO patients as well as diagnosis and clinical management of HIT were analysed. Results: Among the 373 patients included, anti-PF4/heparin antibodies were detected in 53/373 (14.2%) patients. Functional HIT testing confirmed HIT in 13 cases (3.5%) and excluded HIT in 40 cases (10.7%), corresponding to a prevalence of confirmed HIT of 13/373 (3.5%) [1.6, 5.3] and a positive predictive value (PPV) of 24.5% for the antibody screening test. The platelet course including platelet recovery following argatroban initiation was similar between all groups. One-month mortality in patients with excluded HIT was 14/40 (35%) and 3-month mortality 17/40 (43%), compared to 5/13 (38%) (p > 0.999), and 6/13 (46%) (p > 0.999) in patients with confirmed HIT. Neurological outcome in both groups measured by the cerebral performance category of survivors on hospital discharge was similar, as well as adverse events during VA-ECMO therapy. Conclusions: With a prevalence of 3.5%, HIT is a non-frequent complication in patients on VA-ECMO and was not associated with a higher mortality rate. HIT was ultimately excluded by functional essay in 75% of VA-ECMO patients with clinical suspicion of HIT and positive anti-PF4/heparin antibody test. Argatroban seems to be an appropriate and safe therapeutic option for confirmed HIT-positive patients on VA-ECMO support.

Optical Detection of Heparin in Whole Blood Samples Using Nanosensors Embedded in an Agarose Hydrogel

Point-of-care quantification of the anticoagulant heparin still remains a significant clinical challenge as the reference method (colorimetric anti-factor Xa assay) cannot be performed in whole blood. Our group recently put forth the novel optical nanosensing principle using an ionic solvatochromic dye as a signal transducer. These nanosensors demonstrated significantly improved selectivity and sensitivity compared to ion-exchange-type polyion nanosensors and enabled protamine/heparin quantification in blood plasma samples. However, because the readout is absorbance-based, they are still not suitable for whole blood measurements. To overcome the background absorbance of blood, the nanosensors were here embedded in an agarose hydrogel capable of filtering out red blood cells while allowing plasma components to diffuse into the gel. Calibration curves for both protamine and heparin were successfully obtained in buffer, undiluted plasma, and undiluted whole blood using different colorimetric image analysis methods and a simple experimental setup.

Anticoagulation Strategies during Extracorporeal Membrane Oxygenation: A Narrative Review

The development of extracorporeal life support technology has added a new dimension to the care of critically ill patients who fail conventional treatment options. Extracorporeal membrane oxygenation (ECMO)—specialized temporary life support for patients with severe cardiac or pulmonary failure—plays a role in bridging the time for organ recovery, transplant, or permanent assistance. The overall patient outcome is dependent on the underlying disease, comorbidities, patient reaction to critical illness, and potential adverse events during ECMO. Moreover, the contact of the blood with the large artificial surface of an extracorporeal system circuit triggers complex inflammatory and coagulation responses. These processes may further lead to endothelial injury and disrupted microcirculation with consequent end-organ dysfunction and the development of adverse events like thromboembolism. Therefore, systemic anticoagulation is considered crucial to alleviate the risk of thrombosis and failure of ECMO circuit components. The gold standard and most used anticoagulant during extracorporeal life support is unfractionated heparin, with all its benefits and disadvantages. However, therapeutic anticoagulation of a critically ill patient carries the risk of clinically relevant bleeding with the potential for permanent injury or death. Similarly, thrombotic events may occur. Therefore, different anticoagulation strategies are employed, while the monitoring and the balance of procoagulant and anticoagulatory factors is of immense importance. This narrative review summarizes the most recent considerations on anticoagulation during ECMO support, with a special focus on anticoagulation monitoring and future directions.

Pulmonary Embolism (PE) in Transit in Heparin-Induced Thrombocytopenia (HIT) With Negative Serotonin-Release Assay (SRA)

Pulmonary embolism (PE) is a potentially lethal condition, although frequently diagnosed, and is rarely associated with transit on initial presentation. Heparin-induced thrombocytopenia (HIT) can cause both arterial thrombus formation and venous thromboembolism. The two forms of HIT must be differentiated in order to guide management. We present a complex and unique case of PE in transit secondary to HIT diagnosed in a patient with a negative serotonin assay.

Kounis syndrome leading to triple-vessel coronary artery ischaemia due to simultaneous coronary spasm, plaque erosion, and multiple stent thrombosis: a case report

Background

Kounis syndrome (KS) is an acute coronary syndrome (ACS) induced by allergic reactions. Currently, there are three variants of KS based on the mechanism and onset of ACS. We report a rare case of KS, wherein ACS was caused by all KS variants.

Case summary

A 68-year-old man with a history of percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction of the left anterior descending artery 16 days ago underwent a staged PCI for the mid-left circumflex artery (LCx) stenosis under optical coherence tomography (OCT) guidance using low-molecular-weight dextran (LMWD). During OCT examination, the LMWD induced an anaphylactic reaction. The patient was immediately administered medications to manage the anaphylaxis; however, he complained of chest discomfort. Coronary angiography and subsequent intravascular ultrasound revealed a newly developed coronary thrombus in the proximal LCx. Furthermore, coronary spasm or multiple stent thromboses occurred sequentially in all coronary arteries, resulting in triple-vessel coronary artery ischaemia. Balloon angioplasty was performed under intra-aortic balloon pumping, which could rescue the patient. The patient was discharged without any complications 11 days post-KS, under a 7-day anti-histamine regimen. No further cardiovascular events had occurred by 1-year follow-up.

Discussion

This case documented the clinical course of KS caused by LMWD, wherein all KS variants occurred sequentially. Early recognition of KS and appropriate management with anaphylaxis medication and balloon angioplasty under mechanical circulatory support effectively prevent vascular morbidity. Interventionalists should be aware of this rare and serious complication of PCI.

Homozygous Factor V Leiden Complicated by Heparin-Induced Thrombocytopenia: A Case Report

Homozygous factor V Leiden (FVL) is a rare condition, occurring in 0.2% of the white population. This disease's rarity and aggressive pathophysiology can represent a challenge even to the most experienced clinicians. We report a case of a 35-year-old white man, who presented to the emergency department with a 1-week history of bilateral thigh swelling and pain. His past medical history included homozygous FVL mutation complicated by multiple venous thromboembolic events in the last decade, recent inferior vena cava (IVC) filter placement, diabetes mellitus type 2, and hypertension. Despite being trialed for different anticoagulation therapies over 10 years, including warfarin (international normalized ratio (INR) goal 2 - 3), rivaroxaban, and dalteparin, he continued to thrombose. On admission, while on a therapeutic dose of dalteparin, he was diagnosed with extensive acute deep vein thrombosis involving the bilateral femoral and iliac veins, extending proximally to his IVC filter to the renal veins, and pulmonary embolisms in the bilateral lower lobes and right middle lobe. A heparin drip was initiated, and he developed progressive thrombocytopenia over 96 h. Heparin was discontinued, and he was switched to argatroban. He was diagnosed with heparin-induced thrombocytopenia (HIT) with positive anti-platelet factor 4 (PF4)/heparin antibodies and a serotonin release assay. His platelets trended up to normal levels 5 days after heparin discontinuation. He underwent multiple thrombectomies, thrombolysis, and angioplasty of the abdominal and lower extremity veins. The IVC filter was removed. Secondary thrombophilia workup was remarkable for a positive lupus anticoagulant, which had been negative in the past. The patient was bridged to warfarin, discharged with a higher INR goal of 3 - 3.5, and continuously monitored factor II activity (goal 15-30%). This case illustrates a patient with recurrent episodes of thromboembolic events because of homozygous FVL. This condition's pathophysiology and therapeutic approach has been well studied in heterozygous carriers; however, homozygous individuals represent <1% of cases. Given the rareness of the disease, there are no well-established therapeutic guidelines, and long-term anticoagulation remains the therapeutic cornerstone. This case emphasizes the challenges in managing patients with homozygous FVL and complications that can occur due to this gap in the literature. We suggest further case reports and research studies to shed light on this serious condition and its lifetime complications.

Hemostatic Management in Extracorporeal Membrane Oxygenation

The use of extracorporeal membrane oxygenation (ECMO) for acute cardiac and/or respiratory failure has grown exponentially in the past several decades. Systemic anticoagulation is a fundamental element of caring for ECMO patients. Hemostatic management during ECMO walks a fine line to balance the risk of safe and effective anticoagulant delivery to mitigate thromboembolic complications and minimizing hemorrhagic sequelae. This review discusses the pharmacology, monitoring parameters, and special considerations for anticoagulation in patients requiring ECMO.

A journey through anticoagulant therapies in the treatment of left ventricular thrombus in post-COVID-19 heparin-induced thrombocytopenia: a case report

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse drug reaction associated with thrombosis. Clinical scoring systems and the presence of anti-platelet factor 4 (anti-PF4)/heparin antibodies determine the diagnosis.

CASE PRESENTATION

A 57-year-old man who was treated with acenocoumarol due to a chronic left ventricular thrombus was admitted to the hospital for severe SARS-CoV-2 pneumonia and pulmonary embolism. The patient was started on bemiparin and discharged. Left lower limb acute arterial ischemia and thrombocytopenia were diagnosed 18 days later. Computed tomography angiography revealed a large left ventricular thrombus and multiple arterial thrombi. Left femoral-popliteal thromboembolectomy was performed. Anti-PF4/heparin antibodies confirmed an HIT diagnosis. Fondaparinux (7.5 mg/24 h) was initiated, but cardiac surgery was necessary. Bivalirudin was used during surgery, with an initial load (1.25 mg/kg) and maintenance infusion (2.5 mg/kg/h). The cardiac thrombus was extracted, but the patient experienced a postsurgical myocardial infarction. Percutaneous cardiovascular intervention (PCI) required a bivalirudin load (0.75 mg/kg) and maintenance infusion (1.75 mg/kg/h). No coronary lesions were detected, and argatroban was started afterwards (0.5 µg/kg/min). When the platelet count exceeded 100 × 10⁹/L, acenocoumarol was initiated. Thereupon, acetylsalicylic acid (100 mg/24 h) was added. No other complications have been reported to date.

CONCLUSION

The clinical presentation of intraventricular and multiple arterial thrombi is remarkable. SARS-CoV-2 infection likely contributed to a hypercoagulable state. The management of patients with HIT undergoing cardiac surgery is challenging. If surgery cannot be delayed, then treatment with bivalirudin is recommended. Additionally, this drug is recommended for PCI. Bivalirudin is safe and well-tolerated in both procedures.

Case Report: Heparin-Induced Thrombocytopenia Treated With Plasmapheresis Before Living-Donor Kidney Transplantation

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious adverse effect of heparin. Additionally, although heparin can affect kidney transplantation, there only have been a few reports on this condition. Here, we report a case wherein surgery was safely performed with preoperative plasmapheresis in a patient with HIT.

CASE PRESENTATION

The patient was a 48-year-old woman who was on dialysis because of immunoglobulin A nephropathy. Immediately after the initiation of dialysis, the patient experienced repeated arteriovenous fistula occlusion and thrombocytopenia and had a positive HIT antibody test result. Subsequently, she received an ABO-incompatible living-donor kidney transplantation from her spouse. The surgery was performed without using anticoagulants because HIT antibodies disappeared with preoperative plasmapheresis. Eighteen months after surgery, her kidney function remained stable, and there was no recurrence of HIT.

CONCLUSION

Preoperative plasmapheresis is useful for patients with HIT.

Heparin-Induced Thrombocytopenia: A Management Review for Nurses

Heparin-induced thrombocytopenia (HIT) is a life-threatening adverse drug reaction that relies on quick assessment and treatment by the health care team to prevent poor outcomes. Nurses can play a critical role in recognizing disease, advocating for patients, and facilitating treatment by being familiar with current guideline recommendations and risk stratification approaches. The purpose of this article is to review management of HIT including pathogenesis, clinical presentation, current guideline recommendations for risk assessment, laboratory testing, and treatment, as well as discuss nonheparin anticoagulation options that may be ordered when HIT is suspected.

Guideline No. 417: Prevention of Venous Thromboembolic Disease in Gynaecological Surgery

OBJECTIVE

The primary objective of this clinical practice guideline is to provide gynaecologists with an algorithm and evidence to guide the use of thromboprophylaxis in gynaecological surgery.

TARGET POPULATION

All patients undergoing gynaecological surgery for benign or malignant indications.

BENEFITS, HARMS, AND COSTS

The implementation of this guideline will benefit patients undergoing gynaecological surgery and provide physicians with a standard algorithm for the use of perioperative thromboprophylaxis.

EVIDENCE

The following search terms were entered into MEDLINE, Google Scholar, and Cochrane in 2017 and 2018: VTE, PE, DVT, thromboprophylaxis, gynaecological surgery, heparin, graduated compression stocking, intermittent pneumatic stocking, obesity, pediatrics, minimally invasive surgery, heparin induced thrombocytopenia, regional anesthesia). Articles included were randomized controlled trials, meta-analyses, systematic reviews, and observational studies. Additional publications were identified from the reference lists of these articles. There were no date limits, but search results were limited to English language articles only. Searches were updated and incorporated into the guideline up to September 2018.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations).

INTENDED USERS

Gynaecologists and other members of the surgical team. RECOMMENDATIONS (GRADE RATINGS IN PARENTHESES).

Prothrombotic Phenotype in COVID-19: Focus on Platelets

COVID-19 infection is associated with a broad spectrum of presentations, but alveolar capillary microthrombi have been described as a common finding in COVID-19 patients, appearing as a consequence of a severe endothelial injury with endothelial cell membrane disruption. These observations clearly point to the identification of a COVID-19-associated coagulopathy, which may contribute to thrombosis, multi-organ damage, and cause of severity and fatality. One significant finding that emerges in prothrombotic abnormalities observed in COVID-19 patients is that the coagulation alterations are mainly mediated by the activation of platelets and intrinsically related to viral-mediated endothelial inflammation. Beyond the well-known role in hemostasis, the ability of platelets to also release various potent cytokines and chemokines has elevated these small cells from simple cell fragments to crucial modulators in the blood, including their inflammatory functions, that have a large influence on the immune response during infectious disease. Indeed, platelets are involved in the pathogenesis of acute lung injury also by promoting NET formation and affecting vascular permeability. Specifically, the deposition by activated platelets of the chemokine platelet factor 4 at sites of inflammation promotes adhesion of neutrophils on endothelial cells and thrombogenesis, and it seems deeply involved in the phenomenon of vaccine-induced thrombocytopenia and thrombosis. Importantly, the hyperactivated platelet phenotype along with evidence of cytokine storm, high levels of P-selectin, D-dimer, and, on the other hand, decreased levels of fibrinogen, von Willebrand factor, and thrombocytopenia may be considered suitable biomarkers that distinguish the late stage of COVID-19 progression in critically ill patients.

An indicator displacement assay-based optical chemosensor for heparin with a dual-readout and a reversible molecular logic gate operation based on the pyranine/methyl viologen

We have reported an optical indicator displacement assay (IDA) for heparin with a UV-vis absorbance and fluorescence dual-readout based on pyranine/methyl viologen (MV²⁺). Upon introducing heparin, pyranine/MV²⁺ shows a clearly observable increase in UV-vis absorbance and a turn-on of the fluorescence signal. We have demonstrated that the ionic nature of buffers significantly affects the pyranine displacement and the zwitterionic HEPES was most suitable for heparin sensing. After careful screening of experimental conditions, the pyranine/MV²⁺-based optical chemosensor exhibits a fast, sensitive, and selective response toward heparin. It shows dynamic linear concentration of heparin in the ranges of 0.1-40 U·mL^-1 and 0.01-20 U·mL^-1 for the absorptive and fluorescent measurements, respectively, which both cover the clinically relevant levels of heparin. As with the animal experiments, the optical chemosensor has been demonstrated to be selective and effective for heparin level qualification in rat plasma. The chemosensor is readily accessible, cost-effective, and reliable, which holds a great promise for potential application on clinical and biological studies. Furthermore, this IDA system can serve as an IMPLICATION logic gate with a reversible and switchable logical manner.

The Relative Early Decrease in Platelet Count Is Associated With Mortality in Post-cardiotomy Patients Undergoing Venoarterial Extracorporeal Membrane Oxygenation

Background: The relationship between the magnitude of platelet count decrease and mortality in post-cardiotomy cardiogenic shock (PCS) patients undergoing venoarterial extracorporeal membrane oxygenation (VA-ECMO) has not been well-reported. This study was designed to evaluate the association between the relative decrease in platelet count (RelΔplatelet) at day 1 from VA-ECMO initiation and in-hospital mortality in PCS patients.

Methods: Patients (n = 178) who received VA-ECMO for refractory PCS between January 2016 and December 2018 at the Beijing Anzhen Hospital were reviewed retrospectively. Multivariable logistic regression analyses were performed to assess the association between RelΔplatelet and in-hospital mortality.

Results: One hundred and sixteen patients (65%) were weaned from VA-ECMO, and 84 patients (47%) survived to hospital discharge. The median [interquartile range (IQR)] time on VA-ECMO support was 5 (3–6) days. The median (IQR) RelΔ platelet was 41% (26–59%). Patients with a RelΔ platelet ≥ 50% had an increased mortality compared to those with a RelΔ platelet < 50% (57 vs. 37%; p < 0.001). A large RelΔplatelet (≥50%) was independently associated with in-hospital mortality after controlling for potential confounders (OR 8.93; 95% CI 4.22–18.89; p < 0.001). The area under the receiver operating characteristic curve for RelΔ platelet was 0.78 (95% CI, 0.71–0.85), which was better than that of platelet count at day 1 (0.69; 95% CI, 0.61–0.77).

Conclusions: In patients receiving VA-ECMO for post-cardiotomy cardiogenic shock, a large relative decrease in platelet count in the first day after ECMO initiation is independently associated with an increased in-hospital mortality.

Refractory Heparin-Induced Thrombocytopenia in a Patient With Subarachnoid Hemorrhage-A Clinical Conundrum

Heparin induced thrombocytopenia (HIT) often resolves with discontinuation of heparin/ heparinoid products. Severe HIT with platelet counts <20,000/µL and disseminated intravascular coagulation is frequently associated with consumptive coagulopathy and systemic thrombosis. Management of severe HIT in patients who fail to improve on discontinuing heparinoid products and argatroban infusion is not well established. We describe a patient admitted with aneurysmal subarachnoid hemorrhage (SAH) who developed severe autoimmune HIT, failed conventional anticoagulation therapy with argatroban and progressed to develop extensive deep venous thrombosis and limb ischemia. She was successfully treated using bivalirudin, immunomodulation with 2 cycles of intravenous immunoglobulin and immunosuppression with methylprednisolone. Refractory severe HIT among SAH patients is rare and pose several therapeutic challenges. We report successful treatment using alternate anticoagulant and immune suppression and modulation.

The roles of platelets in COVID-19-associated coagulopathy and vaccine-induced immune thrombotic thrombocytopenia

In coronavirus disease 2019 (COVID-19), multiple thromboinflammatory events contribute to the pathophysiology, including coagulation system activation, suppressed fibrinolysis, vascular endothelial cell injury, and prothrombotic alterations in immune cells such as macrophages and neutrophils. Although thrombocytopenia is not an initial presentation as an infectious coagulopathy, recent studies have demonstrated the vital role of platelets in COVID-19-associated coagulopathy SARS-CoV-2 and its spike protein have been known to directly or indirectly promote release of prothrombotic and inflammatory mediators that lead to COVID-19-associated coagulopathy. Although clinical features of vaccine-induced immune thrombotic thrombocytopenia include uncommon locations of thrombosis, including cerebral venous sinus, we speculate coronavirus spike-protein-initiated prothrombotic pathways are involved in the pathogenesis of vaccine-induced immune thrombotic thrombocytopenia, as current evidence suggests that the spike protein is the promotor and other cofactors such as perturbed immune response and inflammatory reaction enhance the production of anti-platelet factor 4 antibody.

An Update on COVID-19 Vaccine Induced Thrombotic Thrombocytopenia Syndrome and Some Management Recommendations

The thrombotic thrombocytopenia syndrome (TTS), a complication of COVID-19 vaccines, involves thrombosis (often cerebral venous sinus thrombosis) and thrombocytopenia with occasional pulmonary embolism and arterial ischemia. TTS appears to mostly affect females aged between 20 and 50 years old, with no predisposing risk factors conclusively identified so far. Cases are characterized by thrombocytopenia, higher levels of D-dimers than commonly observed in venous thromboembolic events, inexplicably low fibrinogen levels and worsening thrombosis. Hyper fibrinolysis associated with bleeding can also occur. Antibodies that bind platelet factor 4, similar to those associated with heparin-induced thrombocytopenia, have also been identified but in the absence of patient exposure to heparin treatment. A number of countries have now suspended the use of adenovirus-vectored vaccines for younger individuals. The prevailing opinion of most experts is that the risk of developing COVID-19 disease, including thrombosis, far exceeds the extremely low risk of TTS associated with highly efficacious vaccines. Mass vaccination should continue but with caution. Vaccines that are more likely to cause TTS (e.g., Vaxzevria manufactured by AstraZeneca) should be avoided in younger patients for whom an alternative vaccine is available.

Incidence of Heparin-Induced Thrombocytopenia in Patients With Newly Implanted Mechanical Circulatory Support Devices

BACKGROUND

Heparin exposure and device-related thrombocytopenia complicate the diagnosis of heparin-induced thrombocytopenia (HIT) in patients receiving mechanical circulatory support (MCS). To improve anticoagulation management for patients with newly implanted MCS devices, incidence of confirmed HIT needs to be further characterized.

OBJECTIVES

The purpose of this study is to describe the incidence of HIT and clinical utility of the 4Ts score in patients with newly implanted MCS devices.

METHODS

This is a retrospective analysis of MCS patients receiving unfractionated heparin from 2014 to 2017. The primary end point was incidence of laboratory-confirmed HIT. Strong positive, likely positive, low probability, and negative HIT categories were established based on heparin-induced platelet antibody (HIPA) and serotonin release assay (SRA). Secondary end points include characterization of platelet trends, argatroban use, incidence of HIT among each of the MCS devices, and utility of 4Ts score.

RESULTS

A total of 342 patient encounters met inclusion criteria, of which 68 HIPA tests and 25 SRAs were ordered. The incidence of HIT was 0.88% (3/342) and 4.4% (3/68) in patients with suspected HIT. Of the 68 HIPA tests, 3 (4.4%) were considered strong positive and 3 of the 25 SRAs were positive. Median 4Ts score was 4 [2.5-4] and optical density 0.19 [0.11-0.54]. The positive predictive value for the 4Ts score was 0.15 (CI = 0.03-0.46) and negative predictive value, 0.93 (CI = 0.82-0.98).

CONCLUSION AND RELEVANCE

HIT occurs infrequently with newly implanted MCS devices. The 4Ts score appears to have a high negative predictive value for ruling out HIT.

Can Heparin-Coated ECMO Cannulas Induce Thrombocytopenia in COVID-19 Patients?

Extracorporeal membrane oxygenation (ECMO) is often used in the management of COVID-19-related severe respiratory failure. We report the first case of a patient with COVID-19-related ARDS on ECMO support who developed symptoms of heparin-induced thrombocytopenia (HIT) in the absence of heparin therapy. A low platelet count of 61 G/L was accompanied by the presence of circulating HIT antibodies 12 days after ECMO initiation. Replacement of the ECMO system including cannulas resulted in the normalization of the platelet count. However, the clinical situation did not improve, and the patient died 9 days later. Careful consideration of anticoagulant therapy and ECMO circuit, as well as routine HIT antibody testing, may prevent a fatal course in ECMO-supported COVID-19 patients.

Mechanisms of Immunothrombosis in Vaccine-Induced Thrombotic Thrombocytopenia (VITT) Compared to Natural SARS-CoV-2 Infection

Herein, we consider venous immunothrombotic mechanisms in SARS-CoV-2 infection and anti-SARS-CoV-2 DNA vaccination. Primary SARS-CoV-2 infection with systemic viral RNA release (RNAaemia) contributes to innate immune coagulation cascade activation, with both pulmonary and systemic immunothrombosis - including venous territory strokes. However, anti-SARS-CoV-2 adenoviral-vectored-DNA vaccines -initially shown for the ChAdOx1 vaccine-may rarely exhibit autoimmunity with autoantibodies to Platelet Factor-4 (PF4) that is termed Vaccine-Induced Thrombotic Thrombocytopenia (VITT), an entity pathophysiologically similar to Heparin-Induced Thrombocytopenia (HIT). The PF4 autoantigen is a polyanion molecule capable of independent interactions with negatively charged bacterial cellular wall, heparin and DNA molecules, thus linking intravascular innate immunity to both bacterial cell walls and pathogen-derived DNA. Crucially, negatively charged extracellular DNA is a powerful adjuvant that can break tolerance to positively charged nuclear histone proteins in many experimental autoimmunity settings, including SLE and scleroderma. Analogous to DNA-histone interactons, positively charged PF4-DNA complexes stimulate strong interferon responses via Toll-Like Receptor (TLR) 9 engagement. A chain of events following intramuscular adenoviral-vectored-DNA vaccine inoculation including microvascular damage; microbleeding and platelet activation with PF4 release, adenovirus cargo dispersement with DNA-PF4 engagement may rarely break immune tolerance, leading to rare PF4-directed autoimmunity. The VITT cavernous sinus cerebral and intestinal venous territory immunothrombosis proclivity may pertain to venous drainage of shared microbiotal-rich areas of the nose and in intestines that initiates local endovascular venous immunity by PF4/microbiotal engagement with PF4 autoantibody driven immunothrombosis reminiscent of HIT. According to the proposed model, any adenovirus-vectored-DNA vaccine could drive autoimmune VITT in susceptible individuals and alternative mechanism based on molecular mimicry, vaccine protein contaminants, adenovirus vector proteins, EDTA buffers or immunity against the viral spike protein are secondary factors. Hence, electrochemical DNA-PF4 interactions and PF4-heparin interactions, but at different locations, represent the common denominator in HIT and VITT related autoimmune-mediated thrombosis.

HIT-It or Quit It: Heparin-Induced Thrombocytopenia Testing Appropriateness Using 4T Scoring and Inappropriate Testing Cost Analysis

OBJECTIVES

The American Society of Hematology's 4T scoring system is a validated tool to assess a patient's probability of having heparin-induced thrombocytopenia (HIT) before testing is performed. There is no benefit to testing patients with a low probability 4T score for HIT. This study aimed to assess for inappropriate HIT testing at our institution based on 4T scoring.

METHODS

We retrospectively reviewed 201 patient charts and calculated 4T scores and testing costs to assess for inappropriate testing and the economic impact of such testing.

RESULTS

HIT testing often occurred in the least appropriate patients and resulted in tens of thousands of dollars of waste for unnecessary testing.

CONCLUSIONS

Inappropriate testing for HIT is still a prevalent issue despite literature supporting the 4T score for guidance in testing appropriateness.

Anti-neutrophil cytoplasmic antibody-associated vasculitis accompanied by type II heparin-induced thrombocytopenia resulting in asymptomatic cerebral infarction: a case report

Background

Heparin-induced thrombocytopenia (HIT) involves platelet activation and aggregation caused by heparin or HIT antibodies associated with poor survival outcomes. We report a case of HIT that occurred after hemodialysis was started for rapidly progressive glomerulonephritis (RPGN), which was caused by anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV), and ultimately resulted in asymptomatic cerebral infarction.

Case presentation

A 76-year-old Japanese man was urgently admitted to our hospital for weight loss and acute kidney injury (serum creatinine: 12 mg/dL). Hemodialysis therapy was started using heparin for anticoagulation. Blood testing revealed elevated titers of myeloperoxidase anti-neutrophil cytoplasmic antibodies, and renal biopsy revealed crescentic glomerulonephritis with broad hyalinization of most of the glomeruli and a pauci-immune staining pattern. These findings fulfilled the diagnostic criteria for microscopic polyangiitis, and the patient was diagnosed with RPGN caused by AAV. Steroid pulse therapy, intermittent pulse intravenous cyclophosphamide, and oral steroid therapy failed to improve the patient’s renal function, and maintenance dialysis was started. However, on day 15, his platelet count had decreased to 47,000/µL, with clotting observed in the hemodialysis catheter. Magnetic resonance imaging of the head identified acute asymptomatic brain infarction in the left occipital lobe, and a positive HIT antibody test result supported a diagnosis of type II HIT. During hemodialysis, the anticoagulant treatment was changed from heparin to argatroban. Platelet counts subsequently normalized, and the patient was discharged. A negative HIT antibody test result was observed on day 622.

Conclusions

There have been several similar reports of AAV and HIT co-existence. However, this is a rare case report on cerebral infarction with AAV and HIT co-existence. Autoimmune diseases are considered risk factors for HIT, and AAV may overlap with other systemic autoimmune diseases. To confirm the relationship between these two diseases, it is necessary to accumulate more information from future cases with AAV and HIT co-existence. If acute thrombocytopenia and clotting events are observed when heparin is used as an anticoagulant, type II HIT should always be considered in any patient due to its potentially fatal thrombotic complications.

Evolution of antithrombotic therapy in patients undergoing percutaneous coronary intervention: a 40-year journey

Since its introduction in 1977, percutaneous coronary intervention has become one of the most commonly performed therapeutic procedures worldwide. Such widespread diffusion, however, would have not been possible without a concomitant evolution of the pharmacotherapies associated with this intervention. Antithrombotic agents are fundamental throughout the management of patients undergoing coronary stent implantation, starting from the procedure itself to the long-term prevention of cardiovascular events. The last 40 years of interventional cardiology have seen remarkable improvements in both drug therapies and device technologies, which largely reflected a progressive understanding of the pathophysiological mechanisms of coronary artery disease, as well as procedure- and device-related adverse events. The purpose of this article is to provide an overview of the important milestones in antithrombotic pharmacology that have shaped clinical practice of today while also providing insights into knowledge gaps and future directions.