Conclusion
Interatrial blocks are a separate entity from atrial enlargement and may be of first (partial), second degree (intermittent) or third degree (advanced). This ECG pattern may be transient, it may present simultaneously without left atrial enlargement (or not), and it may be reproduced experimentally. Advanced interatrial block presents a clear ECG pattern (P ≥120 ms with a ± morphology in leads II, III and VF).
Although all IABs are more frequently associated with atrial arrhythmia, its incidence is much higher in advanced IABs when compared with partial IABs. The presence of advanced IAB associated with supraventricular arrhythmias constitutes a true syndrome, named as Bayes’ Syndrome.
Further studies will help in characterising the syndrome in different clinical scenarios.