Comparison of Clinical Outcomes in Patients with Heparin-Induced Thrombocytopenia Treated with Direct Thrombin Inhibitors.

Heparin-induced thrombocytopenia (HIT) is a clinical syndrome that has been reported to occur in 3–5% of patients treated with unfractionated heparin. If untreated, 36–50% of patients diagnosed with HIT develop life or limb-threatening thromboses. The occurrence of thrombosis, the most common serious complication of HIT, results in rates of amputation and death of 10–20% and 20–30% respectively. Thus, the desired clinical outcomes in patients with HIT are the prevention of thromboembolic complications, limb amputation, and death. The three direct thrombin inhibitors available in the U.S. are lepirudin, argatroban and bivalirudin. Lepirudin and argatroban have both been shown in clinical trials to significantly decrease the incidence of these complications in patients with HIT. Our institution also has experience with bivalirudin as treatment for HIT. We therefore sought to confirm whether all-cause mortality, length of stay, bleeding rate, time to platelet recovery, absolute change in platelet count following therapy, and percentage of therapeutic APTTs differed among patients treated with these agents at our institution. Data were collected by retrospective chart reviews, and from the Florida Hospital pharmacy computer system. Length of stay was calculated as the time to hospital discharge following the finding of a positive heparin-platelet factor 4 antibody test. For the purposes of comparison, the therapeutic range for APTT was taken as 50–90 seconds. As shown in the table, there were no statistically significant differences in any of the endpoints, when the efficacy and safety of the three direct thrombin inhibitors were compared. It therefore appears that within our institution, each of the direct thrombin inhibitors are equally efficacious and safe in treating the clinical syndrome of HIT, with similar outcomes with respect to length of stay, recovery of platelet counts, incidence of bleeding, and overall mortality. We conclude that selection of a direct thrombin inhibitor can be guided by the patient’s clinical status and organ function instead of efficacy and safety considerations.