Measurements of myocardium tissue impedance during the cardiac cycle have information about the morphology of myocardium cells as well as cell membranes and intra/extra cellular spaces. Although the variation with time of the impedance cardiac signal has information about the myocardium tissue activity during the cardiac cycle, this information has been usually underestimated in the studies based on frequency-sweep Electrical Impedance Spectroscopy (EIS) technique. In these cases, the dynamic behavior was removed from the impedance by means of averaging. The originality of this research is to show the time evolution of in-vivo healthy myocardium tissue impedance during the cardiac cycle, being measured with a multisine excitation at 26 frequencies (1 kHz-1 MHz). The obtained parameters from fitting data to a Cole model are valid indicators to explain the time relation of the systolic and diastolic function with respect to the myocardium impedance time variation. This paper presents a successful application of broadband Impedance Spectroscopy for time-varying impedance monitoring. Furthermore, it can be extended to understand various unsolved problems in a wide range of biomedical and electrochemical applications, where the system dynamics are intended to be studied.