Background: Axial flow pumps are standard treatment in cases of cardiogenic shock and high-risk interventions in cardiology and cardiac surgery, although the optimal anticoagulation strategy remains unclear. We evaluated whether laboratory findings could predict bleeding complications and acquired von Willebrand syndrome (avWS) among patients who were treated using axial flow pumps.

Methods and Results: We retrospectively evaluated 60 consecutive patients who received Impella® devices (Impella® RP: n=20, Impella® CP/5.0: n=40; Abiomed Inc., Danvers, USA) between January 2019 and December 2020. Thirty-two patients (53.3%) experienced major or fatal bleeding complications (Bleeding Academic Research Consortium score of >3) despite intravenous heparin being used to maintain normal activated partial thromboplastin times (40–50 s). Extensive testing was performed for 28 patients with bleeding complications (87.5%). Relative to patients with left ventricular support, patients with right ventricular support were less likely to develop avWS (87.5% vs. 58.8%, p=0.035). Bleeding was significantly associated with avWS (odds ratio [OR]: 20.8, 95% confidence interval [CI]: 3.3–128.5; p=0.001) and treatment duration (OR: 1.3, 95% CI: 1.09–1.55; p=0.003). Patients with avWS had longer Impella® treatment than patients without avWS (2 days [1–4.7 days] vs. 7.3 days [3.2–13.0 days]).

Conclusions: Anticoagulation monitoring based on aPTT was not sufficient to prevent bleeding complications during axial flow pump support. A more targeted anticoagulation monitoring is needed for patients who receive Impella® devices.