Authors

1. Palermo, Pietro MD
2. Magri, Damiano MD, PhD
3. Sciomer, Susanna MD
4. Stefanini, Elisa MD
5. Agalbato, Cecilia MD
6. Compagnino, Elisa MD
7. Chircu, Cristina M. MD
8. Maffessanti, Francesco PhD
9. Teodoru, Minodora MD
10. Agostoni, Piergiuseppe MD, PhD

Abstract

PURPOSE: To assess whether atrial fibrillation (AF) in heart failure (HF) affects oxygen uptake at anaerobic threshold (

O₂ AT) and heart rate (HR) kinetics.

METHODS: A total of 15 patients with HF and AF and 18 with HF and sinus rhythm (SR) performed a maximal incremental and 2 constant workload cycle ergometer cardiopulmonary exercise tests (below and above AT, at 25% and 75% of maximal workload, respectively). At constant workload tests, kinetics of

O₂ and HR were assessed by calculating time constant ([tau]).

RESULTS: HF patients with AF showed a similar peak

O₂ to those with SR (16.7 +/- 4.5 mL/kg/min vs 16.6 +/- 3.9 mL/kg/min). However,

O₂ AT (11.3 +/- 2.9 mL/kg/min vs 9.3 +/- 2.8 mL/kg/min; P < .05), peak HR (149 +/- 18.8 bpm vs 116.4 +/- 20.4 bpm; P < .001), HR AT (125.3 +/- 19.1 bpm vs 90.3 +/- 15.5 bpm; P < .001), and HR increase during exercise were greater in HF patients with AF. Finally, [tau]HR and [tau]

O₂ below and above AT were not significantly different.

CONCLUSIONS: In HF patients with AF, despite a similar peak

O₂ compared with patients with HF and SR,

O₂ AT is higher because of a higher HR and a greater HR increase during exercise. One postulated mechanism would be a greater cardiac output increase at the beginning of exercise in HF patients with AF. The delayed AT generates uncertainty about the meaning of a

O₂ value at AT in HF patients with AF, because a higher AT is usually associated with better performance and a better prognosis.