Permanent atrial fibrillation affects exercise capacity in chronic heart failure patients

Aims: The influence of permanent atrial fibrillation on exercise tolerance and cardio-respiratory function during exercise in heart failure (HF) is unknown. Methods and results: We retrospectively compared the results of 942 cardiopulmonary exercise tests, performed consecutively at seven Italian laboratories, in HF patients with atrial fibrillation (n = 180) and sinus rhythm (n = 762). By multivariable logistic regression analysis, peak VO₂ (OR 0.376, 95% CI 0.240-0.588, P <0.0001), O₂pulse (VO ₂/heart rate, HR) (OR 0.236, 95% CI 0.152-0.366, P <0.0001), VCO₂ (OR 3.97, 95% CI 2.163-7.287, P <0.0001), and ventilation (OR 1.38, 95% CI 1.045-1.821, P = 0.0231) were independently associated with atrial fibrillation. Anaerobic threshold (AT) was identified in 132 of 180 (73%) atrial fibrillation and in 649 of 762 (85%) sinus rhythm patients (P = 0.0002). By multivariable logistic regression analysis, only peak VO₂ (OR 0.214, 95% CI 0.155-0.296, P <0.0001) was independently associated with unidentified AT. At AT, atrial fibrillation HF patients had higher HR (P <0.0001) and higher VO₂ (P <0.001) compared with sinus rhythm HF patients. Among AT variables, by multivariable logistic regression analysis, only HR was an independent predictor of atrial fibrillation. Conclusion: In HF patients with permanent atrial fibrillation, exercise performance is reduced as reflected by reduced peak VO₂. The finding of unidentified AT is associated with a poor performance. In atrial fibrillation patients, VO ₂ is higher at AT whereas lower at peak. This last observation raises uncertainties about the use of AT data to define performance and prognosis of HF patients with atrial fibrillation.