Bystander atrium detection using coronary sinus (CS) signals

An atrial flutter identification system, the system comprising:

• a catheter comprising multiple electrodes, the catheter configured to be placed in in a coronary sinus (CS) of a heart of a patient so that some of the electrodes overlap a left atrium (LA) of the heart and some of the electrodes overlap a right atrium (RA) of the heart;
• and
• a processor, which is configured to:
• acquire intra cardiac (IC) electrophysiological (EP) signals with the electrodes overlapping the LA;
• acquire IC EP signals with the electrodes overlapping the RA;
• determine LA signal-stability measures by comparing the IC EP signals acquired by the electrodes overlapping the LA with a reference arrhythmogenic CS signal;
• determine RA signal-stability measures by comparing the IC EP signals acquired by the electrodes overlapping the RA with a reference arrhythmogenic CS signal;
• and
• when one of the LA or RA signal-stability measures is above a first threshold while the other of the LA or RA signal-stability measures is below a second threshold, indicate the atrium corresponding to the LA or RA signal-stability measures above the first threshold as a source of atrial flutter.