ESTIMATION OF CIRCULATORY CONDITION BASED ON THE FREQUENCY ANALYSIS OF MOTOR CURRENT WAVEFORM FOR IMPLANTABLE CENTRIFUGAL VAD

Abstract

The continuous monitoring of ventricular function and operating condition of ventricular assist device (VAD) has some advantage for bridge to recovery application or appropriate pump speed control. The stable and long-term assessment of circulatory condition with implantable sensors, however, is difficult. For the stable assessment and successful recovery of the ventricle, we examined the frequency characteristic changes of the relations between motor current (MC) waveform and left ventricular pressure (LVP), cardiac output through the aorta valve (CO), assist ratio (AR) during circulatory support with centrifugal blood pump. [Method] The mock circulatory loop simulated the left ventricular apex to aorta bypass model with a centrifugal blood pump. The peak LVP of the pulsatile ventricle was varied to simulate recovery pattern of the left ventricle. The experiment was repeated at the pump RPM of 1500 to 2100. The power spectral density (PSD) of MC waveform (MCpsdP) was analyzed and its relations to LVP, CO, AR were evaluated. [Results] MCpsdP value showed a strong correlation with LVP peak for the aortic valve closed or opened. Moreover, the change of aortic valve condition was observed from the change of MCpsdP's slope. However, the slope of the linear relationship was varied depending on the pump speed and also aortic valve condition. On the other hand, CO and AR had also strong correlation with MCpsdP. Both correlation slopes were not affected significantly by pump speed and aortic pressure. [Conclusion] The frequency analysis of MC waveform demonstrated the possibilities for circulatory condition estimation in mock loop. We are now planning to evaluate this method with animal experiment.