Explosive Multiterritorial Arterial Thrombosis Following Brief Heparin Exposure: A Diagnostic Pitfall in the Cath Lab.

BACKGROUND: Type II heparin-induced thrombocytopenia (HIT) is a catastrophic immunothrombotic disorder that can be triggered by minimal heparin exposure during routine coronary angiography. CASE SUMMARY: A 67-year-old woman developed "explosive" multiterritorial arterial thrombosis-including acute limb ischemia, an inferior STEMI, and a stroke-within minutes of receiving 5000 units of intra-arterial heparin. This followed a brief nadroparin exposure 8 days prior. Crucially, events occurred while platelet counts were still normal. Despite a negative functional assay, a high 4T score (6 points) confirmed HIT. Management involved non-heparin anticoagulation (danaparoid sodium) and thrombectomies. DISCUSSION: This case highlights a major diagnostic pitfall: severe arterial thrombosis preceding overt thrombocytopenia. The immediate "anaphylactoid-like" reaction following a heparin bolus is often misidentified as contrast allergy, delaying life-saving intervention. TAKE HOME MESSAGES: Suspect HIT in acute systemic reactions or multifocal thrombosis after heparin exposure, regardless of initial platelet counts.