Figure 4.

Schematic illustration of mechanisms underlying the development of biphasic P waves in the sagittal plane. Interatrial conduction over posterior interatrial connections (with or without participation of Bachmann's bundle) result in posterior‐to‐anterior propagation of excitation in the left atrium, leading to positive or isoelectric P waves in the sagittal plane (upper panel, Type 1 P‐wave morphology). Interatrial conduction over Bachmann's bundle only, without contribution from posterior fibers, results in anterior‐to‐posterior activation of the left atrium and biphasic P waves in the same leads (lower panel, Type 2 morphology).