Atypical advanced interatrial block due to giant atrial lipoma

In 2012, a consensus report on interatrial blocks (IAB) was published, which established the electrocardiographic criteria for advanced IAB (A-IAB), consisting of a P-wave duration ≥120 ms plus biphasic ± morphology in the inferior leads (II, III, and aVF).1 The abnormal P-wave morphology seen in A-IAB is due to the complete block of the sinus impulse at the Bachmann region with subsequent retrograde activation of the left atrium (LA). A recent paper has described atypical electrocardiographic findings of A-IAB consisting of either changes in P-wave duration (<120 ms) or P-wave morphology (alterations in the classic biphasic morphology in the inferior leads, but always presenting final negative component in aVF, representative of caudocranial activation of the LA).2 The accurate diagnosis of A-IAB remains imperative given the increased risk of atrial fibrillation and stroke, and the need for monitoring and possible treatment of these conditions.