Absence of atrial contraction and exercise in patients with isolated atrial fibrillation.

The aim of the study was to assess the effect of absence of atrial contraction during exercise. During the incremental ergometer exercise tests, heart rate, oxygen uptake, and oxygen pulse in patients with isolated atrial fibrillation were compared with those in control subjects at rest, at the exercise level of gas exchange anaerobic threshold, and at peak exercise. The study population consisted of 51 subjects aged 40 years or more: 12 patients with isolated atrial fibrillation and 39 control subjects with normal sinus rhythm. Heart rate in control subjects was lower than that in patients with isolated atrial fibrillation, at rest, anaerobic threshold, and peak exercise (74 +/- 12 vs 85 +/- 8 beats/min at rest, 108 +/- 16 vs 134 +/- 18 beats/min at anaerobic threshold, and 151 +/- 16 vs 173 +/- 22 beats/min at peak exercise, all p less than 0.01). During exercise, oxygen uptake in patients with isolated atrial fibrillation was not significantly different from that in control subjects. Oxygen pulse in patients with isolated atrial fibrillation was lower than that in control subjects during exercise (6.45 +/- 2.04 vs 7.84 +/- 1.63 ml/beat at anaerobic threshold, 7.79 +/- 2.28 vs 9.16 +/- 1.79 ml/beat at peak exercise, both p less than 0.05). In patients with isolated atrial fibrillation, the oxygen pulse might be reduced due to the lack of atrial contraction during exercise. However, the oxygen uptake that represents the exercise capacity would be preserved with the increase in heart rate.