Influence of atrial fibrillation on oxygen uptake and exercise tolerance in cardiovascular patients; close association with heart rate response

To investigate the effect of atrial fibrillation (AF) on the oxygen uptake and exercise tolerance, we evaluated cardiopulmonary exercise test (CPET) data in AF patients and heart rate-matched controls with sinus rhythm (cSR) who received ambulatory cardiac rehabilitation. We compared CPET data between AF (N = 27) and cSR patients (N = 106) who had similar HRs at rest and the peak points. Oxygen uptake (VO(2))/kg and relative O(2) pulse (ml/bpm/kg) at rest and the anaerobic threshold (AT) level was not different between AF and cSR patients, but these parameters above the AT level were significantly lower in AF than in cSR patients. Concisely the parallel increase of relative O(2) pulse during exercise was blunted above the respiratory compensation level (Rc) in the AF group. In addition, the HR change during exercise was inversely correlated with the increase of the O(2) pulse above the AT level and this inverse correlation was more prominent in AF patients than in cSR patients. In conclusion, the value of VO(2) was significantly lower above the AT level in AF patients. The trend of O(2) pulse above the AT level was strongly associated with the detrimental response of HR increase and the response was markedly exaggerated in the AF patients.