Temporal presentations of heparin‐induced thrombocytopenia following cardiac surgery: A single‐center, retrospective cohort study

Background Heparin‐induced thrombocytopenia (HIT) is an important adverse drug reaction that can occur postcardiac surgery. Preoperative exposure to unfractionated heparin (UFH) is common, raising the issue of how frequently cardiac surgery‐associated HIT occurs after immunizing preoperative exposure to heparin. Objective To determine the frequency and clinical picture of HIT occurring within 4 days of cardiac surgery (early presentation) versus later presentations (typical, delayed). Methods We identified patients with laboratory‐confirmed HIT following cardiac surgery over 30 years in a single cardiac surgery center. Three different clinical presentations of HIT were identified: typical (HIT‐related platelet count fall beginning between postoperative days [PODs] 5–10), delayed (patients with falls after POD10 or who presented following hospital discharge), and early (established before POD5, including during cardiac surgery [acute intraoperative HIT]). Results Of 129 patients identified with HIT complicating cardiac surgery, 100 had typical and 16 had delayed presentation of HIT; only 13 patients (10.1%) presented with early HIT, all of whom had received exposure to UFH during the 10 days before cardiac surgery. No patient was identified in whom remote preoperative UFH exposure was implicated in explaining early HIT. Notably, five patients appeared to have had acute intraoperative HIT, without immediate adverse consequences. Conclusions Approximately 90% of patients with HIT after cardiac surgery appear to develop this complication due to immunization triggered by cardiac surgery; however, in approximately 10% of patients, early presentation during the first four PODs (or intraoperatively) can be explained by recent immunizing exposure to heparin.