Estimation of the native cardiac output from a rotary blood pump flow: in vitro study

The rotary blood pump will be an implantable left ventricular assist device (LVAD) in the near future. However, the best control method and the interrelationship between the rotary blood pump and native heart functions are unclear. An estimation was made of the native heart cardiac output from the change of an LVAD's outflow waveform. The mock circulation loop was composed of an aortic compliance chamber, left arterial chamber, total artificial heart as a native heart, and a rotary blood pump that was placed as an LVAD with left ventricular drainage. The fast Fourier transform (FFT) technique was utilized to analyze the LVAD's outflow waveform and calculate the pulse power index (PPI) to examine a relation between the PPI and total artificial heart (TAH) output. The PPI increased with the increase of the TAH output; there was a positive correlation, and there was an inverse correlation between the PPI and the assist ratio. From this viewpoint, an estimation of the pulsatility change of the LVAD's outflow wave may indicate the native cardiac output.