LAUSR

To the Editor: Cardiogenic shock carries a high mortality rate. Over last decade increasing number of patients in cardiogenic shock are managed on the percutaneous ventricular assist device, Impella. This is usually a short-term device to support cardiac function. Impella is inserted by a standard catheterization procedure into the left ventricle, sucks the oxygenated blood from the left ventricle and pumps it into the aortic root. Impella assists ventricles in cardiogenic shock and improves mortality. In supporting its mechanics unfractionated heparin (UFH) purge solution is used, which can lead to heparin-induced thrombocytopenia (HIT) in susceptible patients. In all cases of HIT on the Impella device which have been reported since 2008, UFH was replaced with argatroban purge solution. In all cases, the pump functioned smoothly without any complications. Every case has mentioned a different dosage range, because there are no predefined guidelines till now. Table 1 gives details of the cases and the dose of argatroban used. Only 2 cases, reported by Kazutomo Saito,2 had bleeding secondary to argatroban; however, it seems to be dependent on the dose. In the first patient (59 years old) 2 additional bolus doses of 15 mg of argatroban were given. In the other patient (age 30 years) an additional bolus dose of 15 mg was given. Bleeding stopped after patient was weaned off the pump and argatroban purge solution. Blum et al reported a case series of 2 cases where they used argatroban dosage as per liver functions of patients and was titrated as per APTT.3 All patients were maintained at an APTT of 50–90. Webb and Warhoover4 reported a case in 2008 and patient was maintained on argatroban purge solution without any complications. They used a solution of 7 micrograms/mL and they bloused 3500 micrograms initially to get the activated clotting time near 400. Patient was maintained on this clotting time. No bleeding complication was reported. Laliberte and Reed5 reported a case in 2017 in a 70-year-old patient who was maintained on argatroban purge solution without any complications. The Impella devices provide short-term hemodynamic support for refractory cardiogenic shock in the intensive care unit. Impella devices are percutaneously inserted ventricular assist devices that have been used in cardiogenic shock, which are refractory to inotropes and intra-aortic balloon pumps. Multiple studies have reported use of Impella during cardiogenic shock. The Impella device helps to wean off from inotropes and provides ventricular support, which helps in improving mortality.6,7 A continuous purge solution is used to prevent blood from entering the motor and the insertion of device, and it is highly recommended that UFH be added to the purge solution to prevent pump thrombosis and device failure.8 UFH is often used for prophylactic and therapeutic anticoagulation. UFH has unique pharmacologic properties, including a rapid onset of action, ability to inhibit multiple coagulant proteins, ease of monitoring, and reversibility which makes it preferable in acute and ICU setting. HIT is a rare thromboembolic complication. It is an immune mediated complication caused by antibodies directed to complexes containing UFH and an endogenous platelet protein, platelet factor 4 (PF4). The PF4 protein is stored in platelet alpha granules. Platelet activation causes release of PF4, which forms a tetramer that binds to and neutralizes UFH and related endogenous molecules (eg, heparan sulfate, chondroitin sulfate) on endothelial surfaces.1 UFH-PF4 complexes also form on the platelet surface. It presents both as thrombocytopenia and thrombosis. Patients are highly predisposed to thrombosis, in spite of thrombocytopenia, if not treated. The mechanisms of thrombocytopenia in HIT are autoimmune, which include removal of antibody coated platelets by macrophages of the reticuloendothelial system (eg, spleen, liver, bone marrow), which is similar to other types of drug-induced immune thrombocytopenia; consumption of platelets at sites of thrombosis; and platelet destruction due to the development of a consumptive coagulopathy. A second cause of thrombocytopenia is American Journal of Therapeutics 0, 1–3 (2020)