An intracardiac electrogram obtained by placing electrodes near the sinus node or the cardiac muscle fibers located in the posterior wall of the right atrium of the heart which acts as a pacemaker by generating at regular intervals the electric impulses of the heartbeat.

The purpose is to examine the time for impulse conductions from the node to the atrium, one of the upper chambers on either side of the heart, which receive blood from the body and transmit it to the ventricles.