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Accelerometer Detects Pump Thrombosis and Thromboembolic Events in an In vitro HVAD Circuit

Schalit, Itai*,†; Espinoza, Andreas; Pettersen, Fred-Johan§; Thiara, Amrit P. S.; Karlsen, Hilde*; Sørensen, Gro; Fosse, Erik*,†; Fiane, Arnt E.†,¶; Halvorsen, Per S.*

doi: 10.1097/MAT.0000000000000699
Adult Circulatory Support

Pump thrombosis and stroke are serious complications of left ventricular assist device (LVAD) support. The aim of this study was to test the ability of an accelerometer to detect pump thrombosis and thromboembolic events (TEs) using real-time analysis of pump vibrations. An accelerometer sensor was attached to a HeartWare HVAD and tested in three in vitro experiments using different pumps for each experiment. Each experiment included thrombi injections sized 0.2–1.0 mL and control interventions: pump speed change, afterload increase, preload decrease, and saline bolus injections. A spectrogram was calculated from the accelerometer signal, and the third harmonic amplitude was used to test the sensitivity and specificity of the method. The third harmonic amplitude was compared with the pump energy consumption. The acceleration signals were of high quality. A significant change was identified in the accelerometer third harmonic during the thromboembolic interventions. The third harmonic detected thromboembolic events with higher sensitivity/specificity than LVAD energy consumption: 92%/94% vs. 72%/58%, respectively. A total of 60% of thromboembolic events led to a prolonged third harmonic amplitude change, which is indicative of thrombus mass residue on the impeller. We concluded that there is strong evidence to support the feasibility of real-time continuous LVAD monitoring for thromboembolic events and pump thrombosis using an accelerometer. Further in vivo studies are needed to confirm these promising findings.

From the *The Intervention Centre, Oslo University Hospital, 0424 Oslo, Norway

Faculty of Medicine, University of Oslo, 0372 Oslo, Norway

Department of Anesthesiology, Oslo University Hospital, 0424 Oslo, Norway

§Department of Clinical and Biomedical Engineering, Oslo University Hospital, 0424 Oslo, Norway

Department of Cardiothoracic Surgery, Oslo University Hospital, 0424 Oslo, Norway.

Submitted for consideration January 2017; accepted for publication in revised form September 2017.

Disclosure: The research was funded by the South-Eastern Norway Regional Health Authority. The idea of using accelerometer in pump thrombosis detection is patented, and the authors Halvorsen, Espinoza, and Fosse are patent holders. Fiane is a consultant for HeartWare. We report no other conflict of interest.

Correspondence: Itai Schalit, MD, The Intervention Centre, Rikshospitalet - Oslo University Hospital, Box 4950 Nydalen, 0424 Oslo, Norway. Email:,

Copyright © 2018 by the American Society for Artificial Internal Organs