Atrial Flutter and Atrial Fibrillation
With atrial flutter the 'P' waves are called flutter waves. The PRI is indeterminate. Note the 'Flutter' waves. They often look like a 'saw tooth' shape. Report the F wave to QRS ratio. If not a consistent ratio it is called Atrial Flutter with Variable AV conduction (as seen below).
Below are some examples of Atrial Flutter
EKG Page