Delayed Anaerobic Threshold in Heart Failure Patients With Atrial Fibrillation.
OBJECTIVE
To assess whether atrial fibrillation (AF) in heart failure (HF) affects oxygen uptake at anaerobic threshold ((Equation is included in full-text article.)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 (Equation is included in full-text article.)O2 and HR were assessed by calculating time constant (τ).


RESULTS
HF patients with AF showed a similar peak (Equation is included in full-text article.)O2 to those with SR (16.7 ± 4.5 mL/kg/min vs 16.6 ± 3.9 mL/kg/min). However, (Equation is included in full-text article.)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, τHR and τ(Equation is included in full-text article.)O2 below and above AT were not significantly different.


CONCLUSIONS
In HF patients with AF, despite a similar peak (Equation is included in full-text article.)O2 compared with patients with HF and SR, (Equation is included in full-text article.)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 (Equation is included in full-text article.)O2 value at AT in HF patients with AF, because a higher AT is usually associated with better performance and a better prognosis.
Centro Cardiologico Monzino (Drs Palermo, Stefanini, Agalbato, Compagnino, Maffessanti, and Agostoni), IRCCS, Milan, Italy; Dipartimento di Medicina Clinica e Molecolare (Dr Magrì), Università degli Studi di Roma "La Sapienza," Rome, Italy; Dipartimento di Scienze Cardiovascolari (Dr Sciomer), Respiratorie, Anestesiologiche, Nefrologiche e Geriatriche, "La Sapienza," Rome, Italy; Emergency Clinical Hospital Sibiu (Dr Chircu), Sibiu, Romania; Faculty of Medicine (Dr Teodoru), "Lucian Blaga" University, Sibiu, Romania; and Department of Clinical Sciences and Community Health (Dr Agostoni), University of Milan, Milan, Italy.
Pietro
P
Palermo
Damiano
D
Magrì
Susanna
S
Sciomer
Elisa
E
Stefanini
Cecilia
C
Agalbato
Elisa
E
Compagnino
Cristina M
CM
Chircu
Francesco
F
Maffessanti
Minodora
M
Teodoru
Piergiuseppe
P
Agostoni
D000368:Aged; D015308:Anaerobic Threshold; D001281:Atrial Fibrillation / Q000150:complications / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion / Q000502:physiology*; D013997:Time Factors