In which rhythm would you observe "sawtooth" waves in the lead II ECG?

In atrial flutter, "sawtooth" waves, often referred to as "F-waves," are characteristic features that can be seen on the ECG, particularly in lead II. These F-waves create a distinctive pattern resembling a series of sawteeth and are typically observed in a regular rhythm. This rhythm is caused by a reentrant circuit within the atria, leading to rapid atrial depolarization at rates often between 240 to 340 beats per minute.

In contrast, atrial fibrillation presents with an irregularly irregular rhythm without distinct organized F-waves; instead, there is chaotic electrical activity with no identifiable atrial contraction. Ventricular fibrillation is characterized by rapid, disorganized electrical activity that does not produce any effective heart contractions and thus lacks a sawtooth appearance. Normal sinus rhythm features a smooth, consistent pattern with P waves preceding QRS complexes, which does not resemble the chaotic sawtooth pattern seen in atrial flutter. Therefore, the presence of sawtooth waves in lead II specifically indicates atrial flutter as the correct answer.