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

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.

A Case of Argatroban Refractory Heparin Induced Thrombocytopenia and Thrombosis

Prophylaxis for deep vein thrombosis is a standard of care for most hospitalized patients. This is typically given in the form of chemical prophylaxis by either, unfractionated heparin or low molecular weight heparin. One complication of administration, besides bleeding, is heparin induced thrombocytopenia (HIT). Of patients receiving therapeutic anticoagulation with heparin an estimated, .5%-1% will go on to develop heparin induced thrombocytopenia.¹ We will present a case of argatroban refractory HIT after a coronary artery bypass grafting resulting in a massive left ventricular thrombus and death. There is a paucity of literature on the topic of argatroban refractory HIT. When it is discussed, the persistent drop of platelets and ongoing thrombosis, despite argatroban therapy, appears to be the hallmark. The treatment being used in these rare cases is intravenous immunoglobulin. Our case sheds light on the existence of this entity and helps consolidate some literature on the topic.