A normal wave is typically upright in leads I, II and aVF, and biphasic in lead V1. An abnormal P waveA wave generated from the depolarization of the atria; the P wave is upright when originating from the SA node. The P wave represents the depolarization of the right and left atria. The P wave begins with the first deviation... can possess several alternate characteristics including a misshapen P wave (bifid shape), a P wave lasting longer than 115 milliseconds, having a size more than 2.5 mm in leads II and III, or being inverted in Leads I, II or aVF.
