Autoimmune heparin-induced thrombocytopenia of delayed onset: a clinical challenge

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.

Cerebral Venous Thrombosis in Patients With Heparin-Induced Thrombocytopenia a Systematic Review

BACKGROUND

Cerebral venous thrombosis (CVT) has recently been reported as a common thrombotic manifestation in association with vaccine-induced thrombotic thrombocytopenia, a syndrome that mimics heparin-induced thrombocytopenia (HIT) and occurs after vaccination with adenovirus-based SARS-CoV-2 vaccines. We aimed to systematically review the incidence, clinical features, and prognosis of CVT occurring in patients with HIT.

METHODS

The study protocol was registered with PROSPERO (CRD42021249652). MEDLINE, EMBASE and Cochrane CENTRAL were searched up to June 1, 2021 for HIT case series including >20 patients, or any report of HIT-related CVT. Demographic, neuroradiological, clinical, and mortality data were retrieved. Meta-analysis of proportions with random-effect modeling was used to derive rate of CVT in HIT and in-hospital mortality. Pooled estimates were compared with those for CVT without HIT and HIT without CVT, to determine differences in mortality.

RESULTS

From 19073 results, we selected 23 case series of HIT (n=1220) and 27 cases of HIT-related CVT (n=27, 71% female). CVT developed in 1.6% of 1220 patients with HIT (95% CI,1.0%-2.5%, I²=0%). Hemorrhagic brain lesions occurred in 81.8% of cases of HIT-related CVT and other concomitant thrombosis affecting other vascular territory was reported in 47.8% of cases. In-hospital mortality was 33.3%. HIT-related CVT carried a 29% absolute increase in mortality rate compared with historical CVT controls (33.3% versus 4.3%, P<0.001) and a 17.4% excess mortality compared with HIT without CVT (33.3% versus 15.9%, P=0.046).

CONCLUSIONS

CVT is a rare thrombotic manifestation in patients with HIT. HIT-related CVT has higher rates of intracerebral hemorrhage and a higher mortality risk, when compared with CVT in historical controls. The recently reported high frequency of CVT in patients with vaccine-induced thrombotic thrombocytopenia was not observed in HIT, suggesting that additional pathophysiological mechanisms besides anti-platelet factor-4 antibodies might be involved in vaccine-induced thrombotic thrombocytopenia-related CVT.

Delayed-Onset Heparin-Induced Thrombocytopenia With Cerebral Venous Sinus Thrombosis Following Total Knee Arthroplasty: Case Report

Heparin-induced thrombocytopenia (HIT) is a prothrombotic state caused by autoantibodies against platelet factor 4 (PF4)-heparin complexes. Although HIT typically presents 5-10 days after the initiation of heparin, thrombosis and thrombocytopenia may occur up to several weeks following heparin withdrawal, so-called delayed-onset HIT. Although rare, there have been isolated reports of HIT-induced cerebral venous sinus thrombosis (CVST), which carry high rates of morbidity and mortality. There is a need to further characterize the etiology, clinical presentation, treatment paradigms, and outcomes of patients with HIT-induced CVST. Here, we present the case of a 57-year old female who presented to the emergency department with a headache and seizure 11 days following a right total knee arthroplasty for which she received 3 post-operative doses of enoxaparin. Work-up demonstrated acute intracerebral hemorrhage (ICH), CVST, and thrombocytopenia. Intravenous heparin resulted in rapidly deteriorating platelet count and subsequent serologic testing confirmed the diagnosis of HIT. Treatment with bivalirudin was initiated, the HIT resolved, and the patient was discharged home on hospital day 19 with long-term anticoagulation mediated by warfarin. At 3-month follow up, the patient had mild upper motor neuron pattern weakness and was living independently. This case depicts a rare case of delayed-onset HIT and CVST, highlights the importance of establishing a fluid treatment plan for managing HIT-induced CVST, and illustrates the importance of employing rapid anticoagulation despite acute ICH to achieve a desirable clinical outcome.

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

Heparin-induced thrombocytopenia (HIT) causes thrombosis and thrombocytopenia, usually due to prior heparin exposure, so-called classical HIT. However, in the autoimmune form, the signs and symptoms of HIT occur without prior heparin exposure. Development of cerebral venous sinus thrombosis (CVST) secondary to HIT is a rare occurrence, with relatively few reports in the literature. There is a need to better understand the clinical presentation and treatment paradigms in these rare cases. Therefore, we present the first systematic review of CVST occurring in classical and autoimmune HIT. Cases of HIT-induced CVST were identified through a systematic search of Pubmed from the date of inception to March 2021. Literature search revealed 21 cases of HIT and associated CVST with six cases (28.6%) of autoimmune HIT. Patients presented with signs and symptoms consistent with increased intracranial pressure, intracerebral hemorrhage (ICH), and/or focal neurologic deficits. Headache was the most common symptom with 12 patients (60.0%) presenting as such. 10 patients (47.6%) included in the study developed ICH. Non-heparin anticoagulants, especially direct thrombin inhibitors, were the first-line treatment for the majority of patients (55.6%). Intravenous immunoglobulin (IVIG) was used as treatment for select patients (16.7%) with autoimmune HIT. Few patients received surgical intervention for CVST (14.3%) or ICH (30.0%). Four patients had a full recovery, four patients had residual deficits, and seven patients ultimately expired. Symptoms of HIT-induced CVST are often related to CNS dysfunction. Non-heparin anticoagulants are important to treat CVST, even when patients have concomitant ICH, and may be supplemented with IVIG if treating autoimmune HIT. Rapid identification and treatment of HIT-induced CVST is imperative in order to prevent morbidity and mortality.

Autoimmune heparin-induced thrombocytopenia and venous limb gangrene after aortic dissection repair: in vitro and in vivo effects of intravenous immunoglobulin

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder characterized by heparin-dependent antibodies that activate platelets (PLTs) via PLT FcγIIa receptors. "Autoimmune" HIT (aHIT) indicates a HIT subset where thrombocytopenia progresses or persists despite stopping heparin; aHIT sera activate PLTs strongly even in the absence of heparin (heparin-independent PLT-activating properties). Affected patients are at risk of severe complications, including dual macro- and microvascular thrombosis leading to venous limb gangrene. High-dose intravenous immunoglobulin (IVIG) offers an approach to interrupt heparin-independent PLT-activating effects of aHIT antibodies.

CASE REPORT

A 78-year-old male who underwent cardiopulmonary bypass for aortic dissection developed aHIT, disseminated intravascular coagulation, and deep vein thrombosis; progression to venous limb gangrene occurred during partial thromboplastin time (PTT)-adjusted bivalirudin infusion (underdosing from "PTT confounding"). Thrombocytopenia recovered with high-dose IVIG, although the PLT count increase began only after the third dose of a 5-day IVIG regimen (0.4 g/kg/day × 5 days). We reviewed case reports and case series of IVIG for treating HIT, focusing on various IVIG dosing regimens used.

RESULTS

Patient serum-induced PLT activation was inhibited in vitro by IVIG in a dose-dependent fashion; inhibition of PLT activation by IVIG was much more marked in the absence of heparin versus the presence of heparin (0.2 U/mL). Our literature review indicated 1 g/kg × 2 IVIG dosing as most common for treating HIT, usually associated with rapid PLT count recovery.

CONCLUSION

Our clinical and laboratory observations support dose-dependent efficacy of IVIG for decreasing PLT activation and thus correcting thrombocytopenia in aHIT. Our case experience and literature review suggests dosing of 1 g/kg IVIG × 2 for patients with severe aHIT.

Use of intravenous immunoglobulin G to treat spontaneous heparin-induced thrombocytopenia

BACKGROUND

Spontaneous heparin-induced thrombocytopenia (HIT) is a rare but serious prothrombotic syndrome characterized by thrombosis, thrombocytopenia, and strong platelet-activating HIT antibodies in the absence of heparin exposure, and is frequently characterized by a suboptimal response to standard therapies. Here, we present the first report of intravenous immunoglobulin G (IVIG) use in a patient with spontaneous HIT.

STUDY DESIGN AND METHODS

Patient information, including demographic, clinical, and laboratory results, were obtained from the electronic medical record. Laboratory testing was performed in the serotonin release assay, platelet factor 4 (PF4)-dependent P-selectin expression assay, and PF4/polyvinylsulfonate enzyme-linked immunosorbent assay to study the impact of IVIG on HIT antibody-mediated platelet activation. The patient was also genotyped for a polymorphism in the IgG receptor on platelets, FcγRIIa, at amino acid position 131.

RESULTS

A 30-year-old man had a thrombotic stroke and thrombocytopenia and strong HIT serologies in the absence of proximate heparin use. Direct thrombin inhibitor therapy was not associated with a prompt response. Due to severity and extent of thrombosis and persistent thrombocytopenia, he was treated with high-dose IVIG. This treatment was associated with rapid and sustained normalization of platelet counts and a gradual improvement in thrombotic complications. Platelet activation induced by HIT antibodies in the PF4-dependent P-selectin expression assay (low PF4) was significantly lower after IVIG treatment, correlating well with platelet rise. Consistent with the severity of thrombosis, the patient was found to possess the 131HR polymorphism in FcγRIIa.

CONCLUSION

These results suggest that IVIG may be a useful adjunctive therapy in spontaneous HIT.