Atrial flutter often presents with 2:1 conduction, and the diagnosis is often missed. Atrial flutter with 2:1 conduction can appear, on first glance, to be sinus tachycardia. It is always wise to look for atrial flutter in anyone with a heart rate of approximately 150 / minute. Sinus tach at this rate is rare in patients who are at rest. Because the flutter waves of atrial flutter usually have a rate of 250 - 350 bpm, in 2:1 conduction, the QRS complexes (and the patient's pulse) will occur at approximately 125-175. In this example, the rate is near the top of the range. This lead II rhythm strip clearly shows the flutter waves as they continue, uninterrupted, through the QRS complexes. Not all leads will show the flutter waves clearly, and it is highly recommended that you check all rhythm strips in as many leads as available. It is also wise to watch the rhythm for a while. Notice near the end of this strip, there is a moment of 3:1 conduction, and the flutter waves are uncovered. It is important to distinguish between sinus tach and atrial flutter because the etiology and treatment are very different for the two rhythms.