New Public Defence

On October 28 2022 MD Itai Schalit from The Intervention Centre and Institute of Clinical Medicine at Faculty of Medicine, University of Oslo defended the thesis “Accelerometer-based monitoring of left ventricular assist device: tromboembolism and pump thrombosis detection in HeartWare HVAD” for the degree of PhD. The candidate presented an excellent trial lecture on the given topic: “The history and working principles of mechanical cardiac assist devices”. The image shows main supervicer professor Steinar Halvorsen congratulating the PhD candidate after the dissertation. ​

​Summary
​​End stage heart failure is a major challenge in the developed countries. Heart transplantation, the treatment of choice, is limited by organ supply. Left ventricular assist device (LVAD) support for the heart, is an alternative treatment. It has, however, severe complications, including stroke and pump thrombosis. Accurate diagnosis of These complications is lacking. Increased third harmonic (pump speed x 3) amplitude on pump sounds analysis has been shown to correlate with pump thrombosis. However, it’s intermittent nature and varied signal quality led to low reproducibility between studies.
In this thesis we tested in vitro (paper I, III) and in vivo (paper II, III) a novel accelerometer-based detection of thromboembolism and pump thrombosis in LVAD. We hypothesized that an accelerometer would detect changes in vibration pattern under thromboembolism and pump thrombosis.
LVAD vibrations were recorded by an accelerometer attached to the LVAD housing. Signal changes under thromboembolism were compared with control interventions.
Thromboembolism detection: Thromboembolic events led to acute significant increased amplitude in the third harmonic (paper I and paper II) (ROC analysis area under the curve > 90%). Analyzing changes in the nonharmonic frequencies further improved the positive predictive value of the method by 8.3% (paper III).
Pump thrombosis detection: A subgroup of the thromboembolic events led to persistent signal changes indicating pump thrombosis, which affected either the third harmonic (21.6%), or the nonharmonic frequencies (8.3%). Using both signal changes led to 36% improvement in the positive predictive value of the method (paper III).
The novel accelerometer based LVAD monitoring detected both pump thrombosis and thromboembolic events. It is suitable for real-time continuous monitoring and may open the door to early diagnosis and potentially better response to treatment.