Possible atypical heparin-induced thrombocytopenia presenting with splenic infarction despite preserved platelet counts after cardiac surgery - a case report.

Heparin-induced thrombocytopenia (HIT) type 2 is a major complication of heparin therapy and associated with considerable morbidity and mortality. Correct diagnosis, especially in the intensive care setting where thrombocytopenia occurs frequently, is of paramount importance. We report a 44-year-old female patient undergoing surgical replacement of the tricuspid valve due to Ebstein anomaly. Peri-operatively, the patient was treated with unfractionated heparin (UFH). Sixteen days after treatment initiation, computed tomography incidentally revealed multiple splenic infarctions consistent with embolic infarction. The 4T score was 3 points, suggesting a low pre-test probability for HIT; however, its applicability was limited by post-cardiac surgery platelet kinetics and the absence of a typical platelet fall. A PF4/heparin antibody immunoassay was therefore performed and showed strong positivity (optical density 2.07, lower limit of normal <0.51). Anticoagulation was changed to argatroban, followed by apixaban. Importantly, although an initial perioperative platelet decline of 59% was observed consistent with cardiopulmonary bypass-related consumption, platelet counts had recovered to within the normal range at the time of diagnosis, and no classical secondary platelet fall was observed. In summary, we report a case of possible HIT in which platelet count-based risk stratification may not have fully captured an atypical presentation in this selected clinical setting.