BACKGROUND: Rate control is an acceptable alternative to rhythm control in patients with chronic atrial fibrillation (AF). HYPOTHESIS: The aim of this study of AF patients was to understand the correlation between their exercise capacity and both heart rate (HR) and HR variation index during exercise. METHODS: The exercise capacity of 85 male patients with chronic AF was measured using a cardiopulmonary exercise test (CPX). Within this population, we compared the exercise tolerance of patients with a normal chronotropic response (maximal HR 85%-115% that of the maximal age-predicted HR during CPX) to those whose HR response exceeded this range. Two similar comparisons were made by dividing the subject population according to (1) whether or not their HR variation index (HRVI) during CPX exceeded 10 bpm/min, and (2) whether their HR during the 6-minute walk test exceeded 110 bpm. RESULTS: Patients with an HRVI not over 10 bpm/min showed higher maximal oxygen uptake compared to patients with a higher HRVI (26.7 ± 6.1 vs 22.8 ± 4.8 mL O(2) /kg/min, P = 0.002) and a longer distance walked during CPX (705.6 ± 200.3 vs 520.9 ± 155.5 m, P<0.001). No other significant influence on exercise capacity was seen. Multivariate regression analysis revealed that both the body mass index and the HRVI during CPX were independent predictors of the maximal oxygen uptake. CONCLUSIONS: Better HRVI control on CPX was correlated with better exercise capacity in patients with chronic AF.
BACKGROUND: Rate control is an acceptable alternative to rhythm control in patients with chronic atrial fibrillation (AF). HYPOTHESIS: The aim of this study of AFpatients was to understand the correlation between their exercise capacity and both heart rate (HR) and HR variation index during exercise. METHODS: The exercise capacity of 85 male patients with chronic AF was measured using a cardiopulmonary exercise test (CPX). Within this population, we compared the exercise tolerance of patients with a normal chronotropic response (maximal HR 85%-115% that of the maximal age-predicted HR during CPX) to those whose HR response exceeded this range. Two similar comparisons were made by dividing the subject population according to (1) whether or not their HR variation index (HRVI) during CPX exceeded 10 bpm/min, and (2) whether their HR during the 6-minute walk test exceeded 110 bpm. RESULTS:Patients with an HRVI not over 10 bpm/min showed higher maximal oxygen uptake compared to patients with a higher HRVI (26.7 ± 6.1 vs 22.8 ± 4.8 mL O(2) /kg/min, P = 0.002) and a longer distance walked during CPX (705.6 ± 200.3 vs 520.9 ± 155.5 m, P<0.001). No other significant influence on exercise capacity was seen. Multivariate regression analysis revealed that both the body mass index and the HRVI during CPX were independent predictors of the maximal oxygen uptake. CONCLUSIONS: Better HRVI control on CPX was correlated with better exercise capacity in patients with chronic AF.