A method for analyzing a high frequency (HF) electrogram signal including (a) providing at least one electrogram signal from an electrode located within a subjects body, (b) measuring the electrogram signal at a high frequency during a specific segment of a cardiac cycle, generating a HF electrogram signal, and (c) having a computer measure at least one time-varying parameter of the HF electrogram signal. Related apparatus and methods are also described.
