LVAD Thrombosis Detection Using Third Harmonic Frequency Measured With 3D Accelerometer

Left ventricular assist device (LVAD) thrombosis is a life-threatening condition that is difficult to detect. We investigated whether an accelerometer attached to the LVAD enabled continuous detection of embolic events by analyzing the LVAD vibration pattern. An accelerometer was attached to the surface of an internal LVAD and used in 2 in-vitro experiments using a circuit filled with heparinized full blood. The circuit included a reservoir with a blood filter, pressure transducers and clamps on the LVAD inflow and outflow lines to alter pre- and afterload. Blood thrombi (n=21, volumes 0.05-2ml) were injected in the inflow line to test sensitivity of the method. To test specificity RPM was stepwise changed from 1800-2600 (n=5), preload reduced (n=9) and afterload increased to flow obstruction (n=18), and boluses of 20 ml 0.9% NaCl iv (n=7) were given. In an in-vivo LVAD experiment (pig 90 kg) 5 thrombi (2ml) were injected in the left atrium. LVAD energy consumption (Watt) and acceleration signals were recorded simultaneously during the interventions. The accelerometer signal was analyzed by Fast Fourier Transform and change in amplitude of the 3rd harmonic used as marker of LVAD thrombosis as previously described by acoustic analysis of pump sound. ROC analysis was used to test sensitivity and specificity. Large changes in the power of the accelerometer 3rd harmonic signal were only found after injection of thrombi (Figure) with sensitivity 0.83, specificity 0.93, AUC 0.851, p<0.001. The LVAD Watt measurements were unchanged during injection of thrombi. Similar changes were found in-vivo. LVAD thrombosis was detected with high sensitivity/specificity with the accelerometer. An accelerometer integrated into the system will enable real time detection of LVAD thrombosis.