Management of a patient undergoing PCI and cardiac surgery during multiple phases of HIT. (A) Patient develops a fall in platelet count and lower extremity deep vein thrombosis 7 days after initiation of unfractionated heparin. The 4Ts score is 7. Heparin is stopped and the patient is started on bivalirudin. HIT laboratory testing reveals a positive PF4/H ELISA and positive SRA. Acute HIT is diagnosed. (B) At hospital day 15, the platelet count has recovered. The PF4/H ELISA and SRA remain positive, meeting criteria for subacute HIT A. The patient undergoes left heart catheterization with bivalirudin. At hospital day 20, he remains in subacute HIT A and requires LVAD placement that cannot be delayed. He receives bivalirudin during LVAD placement. Postprocedurally, he continues receiving bivalirudin and is bridged to warfarin for discharge to home. (C) The patient is subsequently referred to a hematology clinic for cardiac transplant evaluation. Repeat anti-PF4/H testing remains positive by ELISA (1.0 OD units) 45 days post-HIT diagnosis, but the SRA is now negative, satisfying criteria for subacute HIT B. (D) Approximately 3 months after index admission for HIT, both PF4/H ELISA and SRA are negative. The patient is listed for cardiac transplant with planned brief intraoperative heparin exposure followed by treatment with an alternative anticoagulant postoperatively. PCI, percutaneous cardiac intervention; LVAD, left ventricular assist device; PF4/H ELISA, Platelet factor-4/heparin Enzyme linked immunoassay; SRA, serotonin release assay.