Autoimmune heparin-induced thrombocytopenia and venous limb gangrene after aortic dissection repair: in vitro and in vivo effects of intravenous immunoglobulin
Case report published in Transfusion (2019)
Abstract
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.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
A 78-year-old man developed autoimmune heparin-induced thrombocytopenia with venous limb gangrene after aortic dissection repair; high-dose IVIG inhibited his serum's heparin-independent platelet activation in vitro, and a literature review favored 1 g/kg × 2 dosing.
Why This Matters for Hirudotherapy
This case report with accompanying literature review describes a 78-year-old man who developed autoimmune heparin-induced thrombocytopenia (aHIT) with DIC, deep vein thrombosis, and venous limb gangrene after aortic dissection repair; thrombocytopenia recovered with high-dose IVIG, in vitro testing showed IVIG inhibited platelet activation dose-dependently (more so without heparin), and the authors suggest 1 g/kg x 2 dosing for severe aHIT. It is pertinent to hirudotherapy because the patient's gangrene progressed during PTT-adjusted bivalirudin (a direct thrombin inhibitor in the same mechanistic class as the leech-derived anticoagulant hirudin), illustrating both the appeal and the dosing pitfalls of direct thrombin inhibition. As a single case plus narrative review, the findings are hypothesis-generating rather than definitive, the in vitro IVIG effect needs controlled confirmation, and nothing here bears on leech therapy itself.
Citation
Autoimmune heparin-induced thrombocytopenia and venous limb gangrene after aortic dissection repair: in vitro and in vivo effects of intravenous immunoglobulin.
Arcinas et al. · Transfusion, 2019
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