HIT in the head: a systematic review of cerebral venous sinus thrombosis in classical and autoimmune heparin-induced thrombocytopenia

Paradoxical Worsening of Cerebral Venous Sinus Thrombosis Due to Heparin-Induced Thrombocytopenia: A Case Report and Literature Review

Development of cerebral venous sinus thrombosis (CVST) is a rare manifestation of heparin-induced thrombocytopenia (HIT). Herein, we present a case in which heparin administration for primary CVST caused paradoxical worsening of CVST secondary to HIT. A 53-year-old woman diagnosed with CVST was provided with intravenous unfractionated heparin therapy. After 12 days, the patient presented tonic convulsive seizures (TCS). Subsequent magnetic resonance image (MRI) scans revealed an exacerbation of cerebral edema with a subcortical hemorrhage on the left parietal lobe. Laboratory test results revealed a significant decline in platelet count. Heparin was immediately discontinued and replaced with argatroban. The definitive diagnosis of HIT was made through the presence of HIT antibodies. The present case, in which HIT caused the secondary CVST exacerbation, is distinctly rare. Our case provides an instructive example by highlighting the potential of TCS as the first sign of HIT development during CVST treatment.

Platelet factor 4(PF4) and its multiple roles in diseases

Platelet factor 4 (PF4) combines with heparin to form an antigen that could produce IgG antibodies and participate in heparin-induced thrombocytopenia (HIT). PF4 has attracted wide attention due to its role in novel coronavirus vaccine-19 (COVID-9)-induced immune thrombotic thrombocytopenia (VITT) and cognitive impairments. The electrostatic interaction between PF4 and negatively charged molecules is vital in the progression of VITT, which is similar to HIT. Emerging evidence suggests its multiple roles in hematopoietic and angiogenic inhibition, platelet coagulation interference, host inflammatory response promotion, vascular inhibition, and antitumor properties. The emerging pharmacological effects of PF4 may help deepen the exploration of its mechanism, thus accelerating the development of targeted therapies. However, due to its pleiotropic properties, the development of drugs targeting PF4 is at an early stage and faces many challenges. Herein, we discussed the characteristics and biological functions of PF4, summarized PF4-mediated signaling pathways, and discussed its multiple roles in diseases to inform novel approaches for successful clinical translational research.

Autoimmune Heparin-Induced Thrombocytopenia

Autoimmune thrombocytopenia (aHIT) is a severe subtype of heparin-induced thrombocytopenia (HIT) with atypical clinical features caused by highly pathological IgG antibodies ("aHIT antibodies") that activate platelets even in the absence of heparin. The clinical features of aHIT include: the onset or worsening of thrombocytopenia despite stopping heparin ("delayed-onset HIT"), thrombocytopenia persistence despite stopping heparin ("persisting" or "refractory HIT"), or triggered by small amounts of heparin (heparin "flush" HIT), most cases of fondaparinux-induced HIT, and patients with unusually severe HIT (e.g., multi-site or microvascular thrombosis, overt disseminated intravascular coagulation [DIC]). Special treatment approaches are required. For example, unlike classic HIT, heparin cessation does not result in de-escalation of antibody-induced hemostasis activation, and thus high-dose intravenous immunoglobulin (IVIG) may be indicated to interrupt aHIT-induced platelet activation; therapeutic plasma exchange may be required if high-dose IVIG is ineffective. Also, aHIT patients are at risk for treatment failure with (activated partial thromboplastin time [APTT]-adjusted) direct thrombin inhibitor (DTI) therapy (argatroban, bivalirudin), either because of APTT confounding (where aHIT-associated DIC and resulting APTT prolongation lead to systematic underdosing/interruption of DTI therapy) or because DTI inhibits thrombin-induced protein C activation. Most HIT laboratories do not test for aHIT antibodies, contributing to aHIT under-recognition.

Cerebral venous thrombosis in patients with autoimmune disease, hematonosis or coronavirus disease 2019: Many familiar faces and some strangers

BACKGROUND

Cerebral venous thrombosis, a rare stroke, is characterized by neurological dysfunction caused by bleeding and/or infarction resulting from venous sinus thrombosis, the so-called venous stroke. Current guidelines recommend anticoagulants as first-line therapy in the treatment of venous stroke. With complicated causes of cerebral venous thrombosis, treatment is difficult, especially when combined with autoimmune diseases, blood diseases, and even COVID-19.

AIMS

This review summarizes the pathophysiological mechanisms, epidemiology, diagnosis, treatment, and clinical prognosis of cerebral venous thrombosis combined with autoimmune diseases, blood diseases, or infectious diseases such as COVID-19.

CONCLUSION

A systematic understanding of particular risk factors that should not be neglected when unconventional cerebral venous thrombosis occurs and for a scientific understanding of pathophysiological mechanisms, clinical diagnosis, and treatment, thus contributing to knowledge on special types of venous stroke.

Antibodies against platelet factor 4 and the risk of cerebral venous sinus thrombosis in patients with vaccine-induced immune thrombotic thrombocytopenia

BACKGROUND

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare complication of adenoviral vector-based vaccines against SARS-CoV-2. This syndrome is caused by antibodies against platelet factor 4 (PF4; CXCL4) that lead to platelet activation and is characterized by thrombocytopenia and thrombosis in unusual locations, including cerebral venous sinus thrombosis (CVST). VITT can be classified based on anti-PF4 antibodies properties in vitro: those that require PF4 to activate platelets (PF4-dependent) and those that can activate platelets without additional PF4 (PF4-independent) in the serotonin release assay.

OBJECTIVES

We aim to characterize the relationship of VITT platelet-activating profiles with CVST.

METHODS

We conducted a retrospective cohort study involving patients with confirmed VITT who were tested between March and June 2021. Data were collected with an anonymized form and cases were identified as VITT with high clinical suspicion according to platelet activation assays. Anti-PF4 antibody binding regions on PF4 were further characterized with alanine scanning mutagenesis.

RESULTS

Of the patients with confirmed VITT (n = 39), 17 (43.6%) had PF4-dependent antibodies and 22 (56.4%) had PF4-independent antibodies. CVST occurred almost exclusively in PF4-independent patients (11 of 22 vs 1 of 17; P < .05). Additionally, PF4-independent antibodies bound to 2 distinct epitopes on PF4, the heparin-binding region and a site typical for heparin-induced thrombocytopenia antibodies, whereas PF4-dependent antibodies bound to only the heparin-binding region.

CONCLUSION

These findings suggest that VITT antibodies that cause PF4-independent platelet activation represent a unique subset of patients more likely to be associated with CVST, possibly due to the 2 different types of anti-PF4 antibodies.

Vaccine-induced immune thrombotic thrombocytopenia: what do we know hitherto?

Vaccine-induced immune thrombotic thrombocytopenia (VITT), also known as thrombosis with thrombocytopenia syndrome, is a catastrophic and life-threatening reaction to coronavirus disease 2019 (COVID-19) vaccines, which occurs disproportionately in response to vaccination with non-replicating adenovirus vector (AV) vaccines. The mechanism of VITT is not well defined and it has not been resolved why cases of VITT are predominated by vaccination with AV vaccines. However, virtually all VITT patients have positive platelet-activating anti-platelet factor 4 (PF4) antibody titers. Subsequently, platelets are activated and depleted in an Fcγ-receptor IIa (FcγRIIa or CD32a)-dependent manner, but it is not clear why or how the anti-PF4 response is mounted. This review describes the pathogenesis of VITT and provides insight into possible mechanisms that prompt the formation of a PF4/polyanion complex, which drives VITT pathology, as an amalgam of current experimental data or hypotheses.

Decompressive craniectomy for intracranial hypertension in vaccine-induced immune thrombotic thrombocytopaenia: a case series

BACKGROUND

Vaccines have been key in preventing COVID-19 infections and the AstraZeneca (AZ) vaccine has been widely used. However, increased rates of thromboembolic events were identified in recipients and, subsequently, a syndrome of vaccine-induced immune thrombotic thrombocytopaenia (VITT) was described whereby recipients presented with venous sinus thromboses, haemorrhagic infarctions, and - consequently - raised intracranial pressure. National guidance recommended decompressive craniectomies for refractory intracranial hypertension. We describe our neurosurgical experience in managing a cohort of patients with VITT.

CLINICAL PRESENTATION

Four patients were included (three females and one male); median age was 46 years. All patients presented with a constellation of headache, focal neurological deficit(s), altered consciousness, and/or seizure at a median 11 d post-vaccine. Pre-operatively, median GCS was 7 and the median platelet count was 28 × 109/L. Mean craniectomy size was 13 cm × 10 cm. All four cases tested positive for anti-PF4 antibodies. Median length of stay was 9 d (range: 2-25). Of the four who were operated upon, two survived to hospital discharge, and one of these subsequently died at a peripheral hospital.

CONCLUSIONS

VITT-related sinus thromboses and associated infarcts are rare complications of the AZ vaccine. Neurosurgical management involves treating intracranial hypertension however survival outcomes in our cohort were poor. In our series, decompression was performed in deteriorating patients however prophylactic decompression, in the presence of extensive venous sinus thrombosis, should be considered on a case-by-case basis. As vaccination programmes accelerate across the world, neurosurgeons are likely to be increasingly involved in managing intracranial hypertension in patients with VITT-related sinus thromboses.

A Rare Case of Extensive Cerebral Venous Sinus Thrombosis Complicated by Heparin-Induced Thrombocytopenia

Cerebral venous sinus thrombosis (CVST) is a rare but potentially life-threatening cause of stroke. Several risk factors have been identified including hypercoagulable state, malignancy, use of oral contraceptives, pregnancy, head injury, infection, and prothrombotic states such as heparin-induced thrombocytopenia (HIT). HIT is a prothrombotic state leading to thrombosis in several distinct locations including CVST requiring prompt discontinuation of heparin and initiation of nonheparin anticoagulation to prevent catastrophic consequences. Very rarely, HIT can complicate the ongoing CVST leading to worsening thrombosis and clinical deterioration. We here report an exceedingly rare case of CVST complicated by HIT in a 22-year-old female patient who showed remarkable clinical improvement after discontinuation of heparin and initiation of argatroban.

Early recognition and treatment of pre-VITT syndrome after adenoviral vector-based SARS-CoV-2 vaccination may prevent from thrombotic complications: review of published cases and clinical pathway

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but highly morbid complication after adenoviral vector-based SARS-CoV-2 vaccination. The pre-VITT syndrome is defined as vaccine-induced immune thrombocytopenia without thrombosis typically presenting with new-onset headache. This review aims to identify at-risk patients before complications such as cerebral venous sinus thrombosis occur. We review previously published reports of 19 patients (median age 35 years, range 23-74; 16 females) who met the diagnostic criteria for a pre-VITT syndrome. Seven patients progressed to VITT, 12 patients did not. Patients who experienced VITT received delayed treatment. The median interval between the onset of headache and VITT-treatment (i.e. anticoagulation, immune globulins, or corticosteroids) was 5 days (range 1-8 days) compared with 2 days (0-5 days) in those without subsequent VITT (P = 0.033). The interval from onset of headache to anticoagulation was longer in patients with VITT (median 7 vs. 2 days; range 3-9 vs. 0-7 days; P = 0.01). Anticoagulation was safe in all patients with a pre-VITT syndrome as no haemorrhagic complications occurred after anticoagulation was started despite low platelets. The transient decline of platelet count after admission was significantly more pronounced in patients who progressed to VITT (median 67 vs. 0 × 10³/µL; range 0-77 × 10³/µL vs. 0-10 × 10³/µL; P = 0.005). d-dimers did not differ between groups. Pre-VITT syndrome is a 'red flag' and allows to identify and preemptively treat patients at-risk of further progression to VITT. However, it must be distinguished from post-vaccination immune thrombocytopenia.

Spontaneous Reporting to Regulatory Authorities of Suspected Adverse Drug Reactions to COVID-19 Vaccines Over Time: The Effect of Publicity

Introduction

The UK Medicines and Healthcare products Regulatory Agency (MHRA) has published frequent summaries of spontaneous reports of suspected adverse drug reactions (ADRs) (Yellow Cards) to vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The EudraVigilance database has provided similar data for the European Economic Area.

Objective

Our objective was to characterize the evolution over time of spontaneous reports of suspected ADRs to coronavirus disease 2019 (COVID-19) vaccines and to observe the effect of a publicized reaction (cerebral venous and sinus thrombosis [CVST]) on reporting rates.

Methods

We used publicly available data on reports of suspected ADRs and doses of vaccine administered, published by the MHRA, EudraVigilance, and the European Centre for Disease Prevention and Control to calculate reporting rates.

Results

Approximately 4814 Yellow Card reports (23 fatal) per million doses of ChAdOx1 nCoV-19 (AstraZeneca) and 2890 (13 fatal) per million doses of tozinameran (Pfizer/BioNTech) have been lodged. Between 15 March and 31 October 2021, cumulative European reports of CVST rose from 0 to 443 (183 with thrombocytopenia, 72 fatal) with ChAdOx1 nCoV-19 and from 2 to 315 (9 with thrombocytopenia, 28 fatal) with tozinameran. European cases of retinal vein occlusion and thrombosis rose from 0 to 168 with ChAdOx1 nCoV-19 and from 1 to 220 with tozinameran; four of the ChAdOx1 nCoV-19 cases were associated with thrombocytopenia.

Conclusion

Reports of fatal adverse reactions to coronavirus vaccines are very rare. Reports of CVST have been made in relation to both vaccines. Most were submitted after the reaction had been publicized. Thrombocytopenia occurred in a minority of cases. Reports linked both vaccines to cases of retinal vein thrombosis, just four cases with thrombocytopenia. This suggests two different mechanisms of thrombosis associated with the vaccines.

Thrombosis with Thrombocytopenia Syndrome After Administration of AZD1222 or Ad26.COV2.S Vaccine for COVID-19: A Systematic Review

BACKGROUND

Cases of thrombosis with thrombocytopenia syndrome (TTS) have been reported following vaccination with AZD1222 or Ad26.COV2.S. This review aimed to explore the pathophysiology, epidemiology, diagnosis, management, and prognosis of TTS.

METHODS

A systematic review was conducted to identify evidence on TTS till 4th September 2021. Case reports and series reporting patient-level data were included. Descriptive statistics were reported and compared across patients with different sexes, age groups, vaccines, types of thrombosis, and outcomes.

FINDINGS

Sixty-two studies reporting 160 cases were included from 16 countries. Patients were predominantly females with a median age of 42.50 (22) years. AZD1222 was administered to 140 patients (87·5%). TTS onset occurred in a median of 9 (4) days after vaccination. Venous thrombosis was most common (61.0%). Most patients developed cerebral venous sinus thrombosis (CVST; 66.3%). CVST was significantly more common in female vs male patients (p = 0·001) and in patients aged <45 years vs ≥45 years (p = 0·004). The mortality rate was 36.2%, and patients with suspected TTS, venous thrombosis, CVST, pulmonary embolism, or intraneural complications, patients not managed with non-heparin anticoagulants or IVIG, patients receiving platelet transfusions, and patients requiring intensive care unit admission, mechanical ventilation, or inpatient neurosurgery were more likely to expire than recover.

INTERPRETATION

These findings help to understand the pathophysiology of TTS while also recommending diagnostic and management approaches to improve prognosis in patients.

FUNDING

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.