Atrial flutter is defined as an over-excitation of the atrias resulting in an atrial depolarization rate between 250 and 350 beats per minute. This can be due to hyperexcitability due to ischemia or a micro- or macroscopic re-entry pathway in the atrias. The AV node and ventricles can’t keep this pace so usually respond with some atrial beats hitting the still refractory AV node resulting in only a fraction of the atrial complexes getting through into the ventricles. On EKG, this will manifest as multiple atrial depolarizations (P waves) coming between each QRS complex if the ventricular response rate is slowed down by either rate related ischemia or pharmacologic agents such as beta blockers, calcium channel blockers or digitalis. When the ventricular response is slow, atrial flutter has a very typical appearance of “flutter waves” which look like the teeth of a saw. If the ventricular response rate is not slowed, it may be very difficult to pick up atrial flutter. The EKG reader must look very carefully in all leads for P waves that may be hiding within T waves. Since a typical rate for atrial flutter has an atrial rate of 300 bpm, when ever you see a regular ventricular rhythm where you are having trouble discerning the rhythm and the rate is 150, think atrial flutter with every other atrial beat being blocked.
See examples of atrial flutter