Atypical advanced interatrial blocks: Definition and electrocardiographic recognition

The diagnosis of advanced interatrial block (A-IAB) is done by surface ECG analysis when the P-wave ≥120 ms with biphasic (±) morphology in leads II, III and aVF. In this brief communication, we advance a new concept involving atypical patterns of A-IAB due to changes about the morphology or duration of the P-wave. It remains to be determined its real prevalence in different clinical scenarios, and whether these atypical ECG patterns should be considered as predictors of atrial fibrillation/stroke.