What might be the heart rate when atrial flutter with a 2:1 block is present?

In the case of atrial flutter with a 2:1 block, the atrial rate is typically around 300 beats per minute, given that atrial flutter usually results in a rapid atrial rhythm. However, when a 2:1 block is present, only every second atrial impulse is conducted to the ventricles, effectively halving the ventricular rate.

Thus, if the atrial rate is approximately 300 bpm, the ventricular response rate in the presence of a 2:1 block would be approximately 150 bpm (300 bpm divided by 2). This makes a heart rate of 150 bpm the correct response when evaluating the effects of a 2:1 block in patients exhibiting atrial flutter.

Understanding the conduction pattern helps clarify why a 150 bpm rate accurately reflects the physiological response in this situation.