P biatriale depicts an enlargement of both the right and left atria and is very rare. It occurs in patients with complex congenital heart disease or with combined disease of the heart and lungs.
The ECG in Figure 5 depicts P biatriale. Characteristics of P biatriale are:
The terminal negative portion of V1 is deep (> 1 mm) and wide (> 0.04 sec)
12-lead ECG Depicting Biatrial Atrial Enlargement