Abstract
Heparin-induced thrombocytopenia (HIT) is a serious complication of heparin therapy. As thrombosis occurs in 50% of untreated patients, prompt treatment with a direct thrombin inhibitor (DTI) is recommended. Lepirudin and argatroban are currently approved for the treatment of HIT. However, their use is complicated by antibody formation with potential for anaphylactic shock (lepirudin), effects on the PT/INR that complicate transition to coumadin (argatroban), and significant dose adjustments in patients with renal (lepirudin) or liver (argatroban) impairment. The effectiveness of bivalirudin, another DTI, as a replacement for heparin has been well documented in percutaneous coronary intervention, but there are little published data on its use in treating HIT. We now report our experience with bivalirudin in 52 patients with clinical suspicion of HIT, or at increased risk of this complication. HIT was suspected on the basis of a falling platelet count and/or thrombosis in the setting of current or recent heparin therapy (n=49). Patients were considered at increased risk of HIT if they required ongoing intravenous anticoagulation in a setting associated with a high incidence of heparin-platelet factor 4 (HPF4) antibodies (n=3). Data were collected by retrospective chart review, and patients classified according to whether HIT was very likely (n=13), likely (n=17), unlikely (n=11) or very unlikely (n=11). Bivalirudin was given by intravenous infusion, typically at an initial dose of 0.15 - 0.20 mg/kg/h and adjusted to achieve an APTT of approximately 1.5–2.5 x baseline. Twenty-one patients had moderate or severe renal impairment. The infusion rate was significantly lower for patients with severe renal insufficiency, but was not different in those with mild renal dysfunction. ELISA-detectable HPF4 antibodies were present in 43/52 cases. Twenty-seven patients were significantly thrombocytopenic (<100,000 x 109/L) and 22 had thrombosis before therapy. Transition to warfarin was achieved in 44/52 patients with a median overlap of therapy of 4 (0.5–14) days. Bivalirudin therapy was continued for an average of 8.0 (3–47) days, and had a relatively minor impact on the PT/INR. The mean INR on monotherapy was 1.50 (1.23–2.18) with a mean change in INR due to bivalirudin therapy of 0.33 ± 0.22. Therapeutic APTTs were achieved in all patients, with approximately 92.5% of tests in the desired range. The average time to platelet recovery was 3.0 (1–10) days. There were no cases of major bleeding, no deaths attributable to HIT, and no patient required amputation. We conclude that bivalirudin provides safe and effective anticoagulation for patients with suspected HIT, as well as for those with an increased risk of HIT that require intravenous anticoagulation. Potential advantages of bivalirudin include the relatively minor effect on the PT, which facilitates transition to warfarin therapy, and its short half-life in patients at high risk of bleeding or who require invasive procedures at short notice.
Heparin-induced thrombocytopenia
