An implantable device for analyzing a high frequency (HF) electrogram signal received from subcutaneous, above-rib pickup locations, the device including an implantable electrode for use inside a living body, and a can for subcutaneous implantation, the can including a signal pickup configured to pick up an electrogram signal including a high frequency (HF) component, a signal filter connected to the signal pickup and configured to measure a high frequency (HF) component from the electrogram signal, and an analyzer for analyzing the HF component of the electrogram signal, wherein the analyzer is configured to analyze at least one time-varying parameter of the HF component of the electrogram signal, and the signal filter is configured to measure the electrogram signal by using a signal picked up from at least two pickup locations which are both subcutaneous and above-rib. Related apparatus and methods are also described.
