What rhythm is characterized by a "sawtooth" appearance?

The rhythm characterized by a "sawtooth" appearance is atrial flutter. This distinctive appearance arises from the rapid atrial contractions that create a series of triangular waves in the ECG tracing, often described as "F-waves" or "flutter waves." The sawtooth pattern commonly occurs in the inferior leads, such as II, III, and aVF, and is indicative of the reentrant circuit within the atria that leads to this consistent and organized rhythm.

In atrial flutter, the atria contract at a rate typically between 240 and 340 beats per minute, which is much faster than normal sinus rhythm. This results in the characteristic zigzag pattern rather than the irregularly undulating lines seen in atrial fibrillation, which lacks the organized waves and can create more chaotic electrical activity. Therefore, the clear and rhythmic sawtooth pattern seen in atrial flutter significantly differentiates it from these other rhythms.