In addition, an everyday heart rate of 150 is hard work
for the heart, and (untreated)
atrial flutter can, similar to
atrial fibrillation, cause blood clots over time. I think most doctors prefers their patients have atrial fibrillation instead of atrial flutter, as this rhythm is easier to control.
If you have atrial flutter, the heart rate will increase in steps with increasing exercise levels, as the blocking is less and less.