Abstract: A detector for atrial fibrillation and/or atrial flutter comprises an atrial input for receiving an atrial signal representing an intraatrial electrogram or a time course of an intraatrial impedance, a ventricular input for receiving a ventricular event signal comprising information on an occurrence of a cyclically reoccurring ventricular event in chronological association to an atrial signal received via atrial input, an averaging unit adapted to average a plurality of sections of said atrial signal, each section to be considered for averaging starts or ends at a predetermined offset before a ventricular event, and to put out an averaged atrial signal, a peak amplitude determination unit adapted to determine peak-to-peak amplitude of said averaged atrial signal, and threshold comparator adapted to compare peak-to-peak amplitude of averaged atrial signal to predetermined reference value and to generate an AF warning signal if peak-to-peak amplitude of averaged atrial signal is less than predetermined threshol

Abstract: Atrial fibrillation or flutter detector having impedance unit, with measurement input, connected to atrial electrode line having electrode for unipolar measurement of atrium impedance and implemented to generate atrial impedance signal obtained in unipolar manner so that impedance signal comprises multiple impedance values detected at different instants within particular atrial cycle for each atrial cycle, comprising atrial contraction and the following relaxation of the atrium, and having a signal input, via which ventricle signal is supplied to detector, which reflects instants of ventricular contractions in chronological assignment to impedance signal, the detector having an analysis unit, implemented to average multiple sequential impedance signal sections of unipolar atrial impedance signal, delimited by two sequential ventricular contractions with one another and determine maximum amplitude of averaged unipolar atrial impedance signal section, compare to comparison value, and if maximum amplitude of ave