Retrograde Activation of Atria in Auriculoventricular Block: An Electrocardiographic Demonstration

THE retrograde conduction of automatic ventricular beats in a complete auriculoventricular (A-V) block was considered for a long time to be impossible.1 New data accumulated in the recent years concerning this phenomenon have changed this view, and today retrograde conduction is considered not at all uncommon.The form of the abnormal P waves (P') is identical. They are peaked, of short duration, inverted in leads II, III and aVF and positive in lead aVR. They indicate an activation of the atria in a reversed direction, i.e., from the area of the A-V node towards the sinus node.Certain features are common to all tracings displaying these retrograde P waves: (1) Retrograde P waves appear only after automatic ventricular beats and not after conducted beats from atria to ventricles, or as isolated blocked P waves. (2) The abnormal P waves are seen very late in the atrial diastole, only shortly