Incidence of Heparin Induced Thrombocytopenia in Patients Undergoing Implantation of Durable and Non-Durable Mechanical Circulatory Support Devices

Purpose Unfractionated heparin exposure in patients undergoing mechanical circulatory support device (MCSD) implantation increases the risk for developing heparin-induced-thrombocytopenia (HIT). The false positive rate of HIT in this population using current standard testing is unknown. Postoperative and device related thrombocytopenia complicate the HIT diagnosis. Methods A retrospective analysis of patients undergoing MCSD pre-implantation assessment or implantation of MCSD (October 2014 - August 2020) was performed. The primary objective was to assess the incidence of HIT with positive PF4 IgG ELISA (PF4) and serotonin release (SRA) assays. False positive HIT was defined as PF4 ≥0.4 optical density (OD) and negative SRA. Argatroban usage was also assessed. Results 366 patients with 512 tests were analyzed. PF4 tests were performed in 128 patients (158 tests) undergoing pre-implantation assessment, 136 patients (185 tests) with non-durable devices (primarily Impella®), and 102 (169 tests) patients with durable devices (72 ventricular assist devices, 30 total artificial hearts). 25% (92/366) of patients had positive PF4 ≥0.4 OD and had subsequent SRA performed (92 patients, 122 tests). True positive HIT was documented in 13% (12/92) of PF4 positive patients consisting of 1 pre-implantation, 9 non-durable MCSD, and 2 durable MCSD patients. The mean PF4 for true positive HIT was 2.2±0.7 OD. False positive HIT was documented in 15% (19/128) of pre-implantation patients (mean PF4 0.9±0.6 OD), 14% (19/136) of non-durable MCSD patients (mean PF4 0.8±0.5 OD), and 41% (42/102) of durable MCSD patients (mean PF4 1.1±0.6 OD). Argatroban was administered in 40% (37/92) of patients with a positive PF4 and 67% (25/37) of patients with a negative SRA. Conclusion Without clinical suspicion of HIT, preoperative PF4 testing is not recommended. Patients with non-durable MCSD devices are at the highest risk of developing HIT (7%). Although a PF4 ≥0.4 OD is considered a positive screening test for HIT, a higher threshold should be considered for MCSD patients. To our knowledge, this is the first in depth assessment of the incidence of HIT in patients undergoing pre-implantation evaluation for both non-durable and durable MCS devices.