Apixaban for treatment of confirmed heparin-induced thrombocytopenia: a case report and review of literature

Heparin-Induced Thrombocytopenia (HIT) in the Direct Oral Anticoagulants (DOAC) Era

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an uncommon complication of heparin therapy with significant risk for severe morbidity and mortality. We investigated the role and outcome of direct oral anticoagulants (DOACs) for the management of HIT.

METHODS

After institutional review board (IRB) approval, a retrospective review was performed identifying all patients with positive HIT serotonin-release assays between 2020 and 2022 at two hospitals. The demographic and clinical variables were collected as follows: initial anticoagulant, dosing and indication, interval before onset of HIT, thrombotic complications, platelet nadir and recovery, direct thrombin inhibitor (DTI) and DOAC usage, and clinical outcomes.

RESULTS

15 patients were included in the study. 8 underwent a vascular procedure, 3 had cardiac surgery, 1 patient had both and was included in both groups, and 5 patients had either noncardiac, nonvascular surgery, or no surgery. 14 patients received unfractionated heparin (93% with therapeutic dosing), and 1 received prophylactic enoxaparin prior to diagnosis of HIT. The average time to diagnosis of HIT was 10.77 days after initial anticoagulation. In-hospital mortality was 27%, related to Covid-19 infection (3/4) and intracranial hemorrhage (1/4). 40% developed thrombosis (67% venous, 33% arterial) after the diagnosis of HIT. 8/11 survivors were discharged on a DOAC. With DOAC therapy, platelet counts rebounded to an average of 265K ( ± 104.6 K) within an average of 2.3 days and 364K ( ± 273.9 K) within 30 days after initiation of a DOAC. No recurrent thrombosis occurred after DOAC administration and only one patient had persistent thrombocytopenia within 30 days.

CONCLUSIONS

Mortality and thrombosis (arterial and venous) are common complications in patients diagnosed with HIT. In patients who survive to discharge, DOACs are the most common discharge antithrombotic agent, with low rates of recurrent thrombosis and thrombocytopenia.

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

PURPOSE

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

SUMMARY

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

CONCLUSION

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

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.

An Open-Label, Single-Arm, Pilot Intervention Study to Assess the Efficacy and Safety of Apixaban in Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a serious adverse drug reaction due to its related risk of life- and limb-threatening thrombosis. Apixaban is a direct factor Xa inhibitor that may be intended as an ideal alternative for the management of HIT. In this open-label, single-arm, pilot intervention study, the efficacy and safety of apixaban were evaluated in 30 patients over the age of 18 with clinically suspected HIT (4Ts score 4 points or greater). Patients with mechanical heart valves, chronic kidney disease, hepatic impairment, and active bleeding were excluded. In all patients with inclusion criteria, heparin or enoxaparin was discontinued and apixaban was started. The dose of apixaban for HIT suspected patients were defined based on the reason for anticoagulant therapy. Endpoints included confirmed thrombosis, mortality, and adverse treatment-related events. After Apixaban therapy, platelet counts normalized in all patients, none of the 30 subjects developed new, progressive, or recurrent thrombosis, and only 1/30 patients developed hemorrhagic events. Five patients (16.7%) died, but the reason for death was not linked to thrombosis, hemorrhage, or adverse effects of apixaban. Along with the available emerging data, our results propose that apixaban could be a safe and effective drug for the management of suspected HIT in clinically stable patients. This article is protected by copyright. All rights reserved.

Direct Oral Anticoagulants as Successful Treatment of Heparin-Induced Thrombocytopenia: A Parisian Retrospective Case Series

Background: Heparin-induced thrombocytopenia (HIT) is a prothrombotic life-threatening disorder caused by an adverse reaction to heparin exposure. In this context, it is imperative to stop heparin immediately and to replace it by a non-heparin anticoagulant therapy. Despite their advantages, the use of direct oral anticoagulants (DOACs) is only emerging for HIT treatment, and their use remains rare. Objective: To improve our knowledge on the emerging role of DOACs as treatment of HIT and give an overview of our local practices in this context. Patients/Methods: This is a multi-centric retrospective case series of HIT patients referred to our Parisian pharmacovigilance network and treated with DOACs. Results: We report the cases of seven patients from four healthcare centers, diagnosed with HIT (4T score ≥ 4, positive anti-PF4/heparin immunoassay and positive serotonin-release assay) and treated with DOACs. After a few days on substitutive parenteral treatment (n = 6) or directly at HIT diagnosis (n = 1), these patients were treated with either rivaroxaban (n = 6) or apixaban (n = 1) during acute HIT phase. Mean time to platelet count recovery after heparin discontinuation was 3.3 days (range 3-5). No patient experienced major or clinically relevant non-major bleeding or thrombosis that could be related to DOAC treatment during follow-up. Conclusions: Our cases studies are consistent with recent guidelines credit to the potential and safe use of DOAC during acute HIT in clinically stable patients.

Oral Factor Xa (FXa) Inhibitors for Treatment of Heparin-induced Thrombocytopenia (HIT)

Background::

Heparin is the most commonly used injectable anticoagulant for many indications, ranging from the treatment of atrial fibrillation to the prevention of clotting in patients undergoing surgery. Currently, only argatroban and bivalirudin are FDA approved for the management of heparin induced thrombocytopenia (HIT) in the United States, both of which are direct thrombin inhibitors. The agents being reviewed, apixaban and rivaroxaban, are oral direct factor Xa (FXa) inhibitors. Currently, neither has FDA approval for use in HIT. The objective of this review is to summarize the current evidence available regarding the use of oral factor Xa inhibitors for the treatment of HIT.

Methods::

A literature search was conducted using Medline and Ovid Embase. Search terms included heparin-induced thrombocytopenia, HIT, apixaban, rivaroxaban, Xa Inhibitor, direct thrombin inhibitor, NOAC, and DOAC. Studies and case reports were included if they evaluated the efficacy and safety of oral FXa inhibitors for the treatment of HIT. Additional literature and case reports were found through bibliographic review.

Results and Discussion:

Currently, available literature includes an in vitro study with apixaban, case reports, and retrospective and prospective cohort studies. The in vitro study evaluated the interaction between apixaban and platelets in the presence of HIT antibodies, which assessed its potential for use in HIT management. Fourteen case reports and one case series were also identified, of which six described treatment with apixaban and eight with rivaroxaban. Lastly, four cohort studies were published evaluating the use of direct acting oral anticoagulants (DOACs), including oral factor Xa inhibitors in patients with HIT. Although there are no published randomized control trials evaluating the use of FXa inhibitors in the management of HIT, there are several findings that may guide clinicians on the use of these agents in practice.

Conclusion::

As indicated by the case reports, case series and cohort studies detailing clinical use and described in this manuscript, there are data and positive patient outcomes that support the potential use of these agents for HIT, and are an impetus for future studies.

Management of heparin-induced thrombocytopenia: systematic reviews and meta-analyses

Heparin-induced thrombocytopenia (HIT) is a prothrombotic adverse drug reaction occurring in <0.1% to 7% of patients receiving heparin products depending on the patient population and type of heparin. Management of HIT is highly dependent on a sequence of tests for which clinicians may or may not have the results when care decisions need to be made. We conducted systematic reviews of the effects of management strategies in persons with acute HIT, subacute HIT A or B, and remote HIT. We searched Medline, EMBASE, and the Cochrane Database through July 2019 for previously published systematic reviews and primary studies. Two investigators independently screened and extracted data and assessed the certainty of the evidence using the Grading of Recommendations Assessment, Development and Evaluation approach. We found primarily noncomparative studies and case series assessing effects of treatments, which led to low to very low certainty evidence. There may be little to no difference in the effects between nonheparin parenteral anticoagulants and direct oral anticoagulants in acute HIT. The benefits of therapeutic-intensity may be greater than prophylactic-intensity anticoagulation. Using inferior vena cava filters or platelet transfusion may result in greater harm than not using these approaches. Evidence for management in special situations, such as for patients undergoing cardiovascular interventions or renal replacement therapy, was also low to very low certainty. Additional research to evaluate nonheparin anticoagulants is urgently needed, and the development of novel treatments that reduce thrombosis without increasing hemorrhage should be a priority.

Potential Role of Direct Oral Anticoagulants in the Management of Heparin-induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a rare, potentially life-threatening condition secondary to unfractionated heparin or low molecular weight heparin exposure. This immune-mediated drug reaction manifests as thrombocytopenia with a paradoxical hypercoagulable state that can result in life-threatening thrombosis. It is imperative to ensure cessation of heparin-based products as soon as HIT is identified. Traditional treatment options include argatroban, bivalirudin, fondaparinux, and danaparoid with a transition to warfarin upon platelet recovery. These anticoagulants are notwithstanding limitations including parenteral administration and routine laboratory monitoring leading to prolonged hospitalizations, emphasizing the need for new therapies. Direct oral anticoagulants (DOACs) have been increasingly investigated for the management of HIT and may overcome the aforementioned challenges of current therapies. The objective of this narrative review is to summarize the current HIT guidelines, discuss limitations to contemporary treatment options, provide insight into the emerging evidence for the DOACs rivaroxaban, apixaban, and dabigatran, and conclude with a clinical summary for their use in this setting. The PubMed, Google Scholar, and MEDLINE databases were searched for peer-reviewed literature from January 1, 2012, to June 31, 2018. Twenty-seven articles met inclusion criteria for review: 1 prospective trial, 5 retrospective cohort studies, and 21 case reports totaling 104 patients treated with a DOAC for HIT. The DOACs prevented new and recurrent thrombosis in 98% (n=102) of cases, and bleeding complications occurred in 3% (n=3). While current literature remains limited, it is suggestive of a potential role of DOACs for HIT, which has led to their integration into the 2018 American Society Hematology Guidelines with a conditional recommendation.