Characterization of aortic input impedence in the supplemental domain

Although ventricular-arterial coupling has been widely studied with frequency domain modeling of arterial hemodynamics, the existence of reflected flow and pressure waves in the arterial tree still remains controversial. Aortic input impedance (AII) is the ratio between pulsatile aortic pressure and flow waveforms in the frequency domain, and it has been mainly measured using discrete Fourier series (DFS). We propose a signal processing method for accurately estimating the impulse response of AII. In an animal model, the full-band spectra of pulsatile aortic pressure and flow were calculated using homomorphic deconvolution, and then compared to DFS spectra. Given the observed band-limited nature of these signals, we formulated a supplemental domain model for AII estimation, in which calculations are made using equivalent full-band, pole-free spectra of pressure and flow signals. In three animals, impulse responses were obtained, which exhibited among-subjects reproducible patterns in the basal state. The estimation of AII in the supplemental domain allows the estimation of its impulse response, which could explain the role of reflections in the arterial tree