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Detection of Thromboembolic Events and Pump Thrombosis in HeartWare HVAD Using Accelerometer in a Porcine Model

Schalit, Itai*,†; Espinoza, Andreas; Pettersen, Fred-Johan§; Snartland, Steinar; Ringdal, Mari-Ann L.; Hoel, Tom N.; Skulstad, Helge; Fosse, Erik*,†; Fiane, Arnt E.‡,†; Halvorsen, Per S.*,‡

doi: 10.1097/MAT.0000000000000954
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We have recently demonstrated that accelerometer-based pump thrombosis and thromboembolic events detection is feasible in vitro. This article focuses on detection of these conditions in vivo. In an open-chest porcine model (n = 7), an accelerometer was attached to the pump casing of an implanted HeartWare HVAD. Pump vibration was analyzed by Fast Fourier Transform of the accelerometer signals, and the spectrogram third harmonic amplitude quantified and compared with pump power. Interventions included injection of thrombi into the left atrium (sized 0.3–0.4 ml, total n = 35) and control interventions; pump speed change, graft obstruction, and saline bolus injections (total n = 47). Graft flow to cardiac output ratio was used to estimate the expected number of thrombi passing through the pump. Sensitivity/specificity was assessed by receiver operating characteristic curve. Graft flow to cardiac output ratio averaged 66%. Twenty-six of 35 (74%) thrombi caused notable accelerometer signal change. Accelerometer third harmonic amplitude was significantly increased in thromboembolic interventions compared with control interventions, 64.5 (interquartile range [IQR]: 95.4) and 5.45 (IQR: 2.55), respectively (p < 0.01). The corresponding difference in pump power was 3 W (IQR: 0.4) and 2.8 W (IQR: 0.6), respectively (p < 0.01). Sensitivity/specificity of the accelerometer and pump power to detect thromboembolic events was 0.74/1.00 (area under the curve [AUC]: 0.956) and 0.40/1.00 (AUC: 0.759), respectively. Persistent high third harmonic amplitude was evident at end of all experiments, and pump thrombosis was confirmed by visual inspection. The findings demonstrate that accelerometer-based detection of thromboembolic events and pump thrombosis is feasible in vivo and that the method is superior to detection based on pump power.

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

Faculty of Medicine, University of Oslo, Oslo, Norway

Department of Anesthesiology, Oslo University Hospital, Oslo, Norway

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

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

Department of Cardiology, Oslo University Hospital, Oslo, Norway.

Submitted for consideration May 2018; accepted for publication in revised form November 2018.

This research was funded by the South-Eastern Norway Regional Health Authority.

Disclosures: The idea of using accelerometer in pump thrombosis detection is patented, and the authors P.S.H, A.E., and E.F. are patent holders. A.E.F. is a consultant for HeartWare. The other authors have no conflicts of interest to report.

Correspondence: Itai Schalit, The Intervention Centre, Oslo University Hospital, Rikshospitalet, Box 4950 Nydalen, 0424 Oslo, Norway. Email: itai.schalit@gmail.com.

Copyright © 2019 by the American Society for Artificial Internal Organs