Article

PURPOSE: 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 (tau). 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, tauHR and tau(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.

Langue : ANGLAIS