High Quality Content by WIKIPEDIA articles! In cardiology, a wandering pacemaker is an atrial arrhythmia that occurs when the natural cardiac pacemaker site shifts between the SA node, the atria, and/or the AV node. This shifting of the pacemaker from the SA node to adjacent tissues is identifiable on ECG Lead II by morphological changes in P waves; sinus beats have smooth upright P waves, while atrial beats have flattened, notched, or diphasic P-waves.