Can impedance characterize the heart?

When considering the use of Fourier series in hemodynamics, the question is whether one can relate the frequency components of the flow oscillations to the corresponding ones of pressure using impedance concepts. For the arteries, this method provided the basis for great advances in understanding. However, it is precisely because the arterial tree acts almost linearly while its properties do not change markedly within one beat that frequency analysis achieved such success. For the ventricle, in which the mechanical properties vary widely over the course of one heart cycle, Fourier analysis loses its usefulness. Consequently, we must return to the time domain for formulating a description of the heart as a pump. A time-domain method, the impulse response, is suggested as a possible alternative to impedance.