If less than 100 beats per minute, then the term “ectopic atrial rhythm” is used. Because the origination of this electrical activity is not from the sinus node, the P wave would not have its ...

The second ECG strip below shows an ectopic atrial rhythm. Note that the P wave is down in lead II and only up (not biphasic) in lead V1. If there is sinus rhythm, and the heart rate is less than ...