Heparin-Induced Thrombocytopenia in Contemporary Cardiac Surgical Practice and Experience With a Protocol for Early Identification

Abstract

This analysis was designed to (1) examine the impact of heparin-induced thrombocytopenia (HIT) on contemporary cardiac surgical practice and (2) describe the results of a protocol designed for early identification of the presence of the immune mechanisms involved. Consecutive patients who underwent cardiac surgery were screened postoperatively for thrombocytopenia. Patients with thrombocytopenia were tested for antiplatelet factor 4 (PF4)/heparin antibodies by ELISA and clinical evidence of thrombosis sought. Demographics, co-morbidities, operative details, and outcomes were abstracted from the departmental registry. Of 14,415 consecutive patients undergoing cardiac surgery, 1,849 patients (13%) had thrombocytopenia. Of them, 277 patients (15%) had PF4/heparin antibodies and 76 patients (4%) had both antibodies and clinical thrombosis. Antibodies were more frequent: (1) in women (p = 0.01), (2) in patients with an increased body mass index (p <0.01), and (3) in patients with clinical heart failure before surgery (p <0.01). Thirty-day mortality was greatest among the 76 patients with the triad of thrombocytopenia, antibodies, and clinical thrombosis (30%). Of the 1,849 patients with thrombocytopenia, the presence of PF4/heparin antibodies was an independent predictor of 30-day mortality (odds ratio 2.09, 95% CI 1.46 to 2.49; p <0.001). HIT remains an infrequent but very serious complication of heparin therapy in contemporary cardiac surgical practice. The possibility that the presence of HIT antibodies in patients with thrombocytopenia independently increases operative mortality deserves further study.