CHRONOTROPIC RESPONSE TO EXERCISE IN PATIENTS WITH ATRIAL-FIBRILLATION - RELATION TO FUNCTIONAL-STATE

Objective-To determine the relation between functional capacity and he art rate response to exercise in patients with atrial fibrillation. Su bjects-73 consecutive patients with chronic atrial fibrillation. Main outcome measures-Relation between functional capacity, measured as pea k oxygen consumption (peak VO2; ml/min/kg), and heart rate at all stag es of exercise in univariate and multivariate analyses. Results-Peak V O2 showed no correlation with resting heart rate, but it showed a nega tive correlation with heart rate during the first stage of exercise (r = -0.94, p < 0.01). Indeed, heart rate during the early stages of exe rcise (stages 1-5) was higher in patients with a peak VO2 less than or equal to 20 ml/mm/kg than in those with a peak VO2 greater than 20 ml /min/kg (heart rate 140 v 125 beats/min, p < 0.05). At maximal exercis e, however, peak VO2 was positively correlated with heart rate (r = 2. 15, p < 0.0001). Conclusion-In patients with atrial fibrillation and i mpaired functional capacity heart rate at low levels of exercise is au gmented but maximal heart rate attenuated compared with patients with preserved functional capacity. Excessive heart rate responses to minor exercise may have deleterious effects on left ventricular function an d thereby further limit functional capacity.