The Footprints of Pacing Lead Position Using the 12-Lead Electrocardiograph

The 12-lead resting electrocardiograph (ECG) of a patient with an implanted cardiac pacemaker is a snapshot of cardiac electrical activity at the time of recording and may provide valuable information on both pacemaker function and malfunction, as well as identifying the position of pacing leads in the heart. The traditional site for atrial pacing is within or adjacent to the right atrial appendage and paced P waves on the ECG have a normal frontal plane axis, whereas the traditional site for ventricular pacing is at the right ventricular apex with the ECG demonstrating a left bundle branch block configuration and a left axis. More recently, ventricular leads and to a lesser extent, atrial leads have been positioned in alternate non-traditional sites resulting in 12-lead ECG appearances which have characteristic features, that are generally poorly recognised. Left ventricular pacing results in a right bundle branch block configuration and an axis dependent on the position of the lead in the ventricle. This review will describe the ECG patterns of pacing lead positions in the right atrium and ventricle as well as positions in the left ventricle, whether intentional or unintentional.