Abstract: A method is provided for measuring a frequency response of an object, the method involving: generating an excitation signal having relatively fast changing frequency, defined by a time-domain function; generating at least one reference signal, having a waveform corresponding to the excitation signal; introducing the excitation signal into the object, receiving a response signal from the object; analyzing said response signal in a signal analyzer by correlating the response signal with at least one reference signal during a relatively short sliding time-domain window.

Abstract: A method and device are provided for fast impedance measurement of a biological object having dynamically varying in time parameters, wherein a titlet shaped pulse is introduced into the object and a voltage response signal is measured and analyzed by a processing unit for estimating the impedance of the object. The titlet pulse has a start frequency substantially in one end of the frequency range of interest and a stop frequency substantially in the other end of the frequency range of interest and a duration of the titlet pulse is one cycle or less.

Abstract: A device for monitoring cardiac pacing rate having a measuring unit for receiving an electrical signal representing the patient's cardiac demand, and a computing unit for determining the myocardial energy balance by calculating energy consumed by the myocardium for both an external dynamic work for pumping blood into a vascular system, and an internal static work of the myocardium. Volume and time based measurements are used, and in one embodiment, volumes are estimated and volume ratios are calculated from volume estimates. In another embodiment, volumes are estimated from bioimpedance measurements. A further aspect is a rate adaptive pacemaker, wherein the maximum pacing rate is determined from the myocardial energy balance such that the energy supplied to the myocardium approximately equals the energy consumed by the myocardium for both an external dynamic work for pumping blood into a vascular system and an internal static work of the myocardium.