(494) Clearing the Clot: Plasmapheresis Triumph in Acute HIT and Urgent Valve Replacement Surgery

Introduction: Heparin-induced thrombocytopenia (HIT) is an immune-mediated response to heparin therapy, characterized by the formation of antibodies against the heparin-platelet factor 4 complex and a paradoxical increase in thrombotic risk. HIT is life-threatening and management includes immediate cessation of heparin and initiation of alternate anticoagulants. We describe a complex case of mitral stenosis who underwent cardiopulmonary bypass surgery using heparin for urgent valve replacement in the setting of acute HIT.

Description: A 46-year-old woman was admitted for acute limb ischemia and ischemic stroke in the setting of LAA thrombus and atrial fibrillation with underlying severe rheumatic mitral stenosis. Nine days after vascular intervention and initial exposure to heparin, she developed an abrupt drop in platelet count with a 4T-Score of 6/8. Heparin was held and argatroban was initiated. HIT was confirmed with a positive HIT-antibody and serotonin release assay. Unfortunately, she developed bleeding complications, including an intracerebral punctate hemorrhage. Argatroban was held as a result. Subsequently, she had worsening renal function and hypoxemia secondary to refractory pulmonary edema despite fluid removal with continuous renal replacement therapy requiring non-invasive ventilation. She had another cardioembolic event and anticoagulation was resumed with bivalirudin, with plans for urgent valve replacement. However, given the recent intracranial bleed and uncertain half-life of bivalirudin in renal failure, a decision was made to perform plasmapheresis and operate using heparin instead, without any antiplatelet agents. Seroreversion of the HIT-antibody was achieved with plasmapheresis. Mitral valve replacement, maze procedure, and LAA thrombus removal were performed with intraoperative heparin. Post-operatively, bivalirudin was resumed, without further thrombotic or bleeding events.

Discussion: This case highlights the challenges of managing anticoagulation during urgent cardiopulmonary bypass surgeries in patients with acute HIT. The decision to use plasmapheresis until HIT-antibody seroreversion, resulting in a successful outcome, is emphasized. Intraoperative bivalirudin or antiplatelet agents are alternatives but were not used here given the risk of intracranial bleeding.