Atrial activity during exercise in patients with atrial flutter or atrial fibrillation.

The atrial activity was studied at rest and during exercise in 6 patients with atrial flutter and in 7 patients with atrial fibrillation. In the latter, a special recording technique was used which permitted identification of the f-waves. No increase in the frequency of the atrial waves was found. Thus the increase of the ventricular rate during work in patients with atrial flutter or atrial fibrillation seems to be caused by a change in the atrio-ventricular conduction.