What characteristic defines an EKG that shows atrial flutter?

An EKG showing atrial flutter is characterized by the presence of sawtooth F waves, which are typically observed in the inferior leads (II, III, and aVF) and resemble a "flapping" pattern. These F waves are a result of rapid, organized contractions of the atria, usually at rates between 240 to 340 beats per minute.

In atrial flutter, the ventricular response may be regular, particularly if there is a consistent conduction through the AV node, resulting in a stable and predictable number of QRS complexes for each F wave. This regularity of the ventricular response is a key distinguishing feature of atrial flutter compared to other atrial arrhythmias.

The presence of the sawtooth pattern of F waves is vital in making a diagnosis of atrial flutter, differentiating it from other arrhythmias that may display irregular waveforms or different types of P waves. Understanding these nuances is crucial for accurate interpretation of EKG findings.