Objective To investigate whether oxygen uptake (V˙o 2) kinetics during low intensity exercise are related to clinical signs, symptoms, and neurohumoral activation independently of peak oxygen consumption in chronic heart failure.
Design Comparison ofV˙o 2 kinetics with peakV˙o 2, neurohormones, and clinical signs of chronic heart failure.
Setting Tertiary care centre.
Patients 48 patients with mild to moderate chronic heart failure.
Interventions Treadmill exercise testing with “breath by breath” gas exchange monitoring. Measurement of atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), and noradrenaline. Assessment of clinical findings by questionnaire.
Main outcome measures O2 kinetics were defined as O2 deficit (time [rest to steady state] × ΔV˙o 2 − ∑V˙o 2 [rest to steady state]; normalised to body weight) and mean response time of oxygen consumption (MRT; O2 deficit/ΔV˙o 2).
Results V˙o 2kinetics were weakly to moderately correlated to the peakV˙o 2 (O2 deficit,r = −0.37, p < 0.05; MRT,r = −0.49, p < 0.001). Natriuretic peptides were more closely correlated with MRT (ANF,r = 0.58; BNP,r = 0.53, p < 0.001) than with O2 deficit (ANF, r = 0.48, p = 0.001; BNP, r = 0.37, p < 0.01) or peak V˙o 2 (ANF,r = −0.40; BNP,r = −0.31, p < 0.05). Noradrenaline was correlated with MRT (r = 0.33, p < 0.05) and O2 deficit (r = 0.39, p < 0.01) but not with peakV˙o 2(r = −0.20, NS). Symptoms of chronic heart failure were correlated with all indices of oxygen consumption (MRT, r = 0.47, p < 0.01; O2 deficit, r = 0.39, p < 0.01; peak V˙o 2,r = −0.48, p < 0.01). Multivariate analysis showed that the correlation ofV˙o 2 kinetics with neurohormones and symptoms of chronic heart failure was independent of peakV˙o 2 and other variables.
Conclusions Oxygen kinetics during low intensity exercise may provide additional information over peak V˙o 2 in patients with chronic heart failure, given the better correlation with neurohormones which represent an index of homeostasis of the cardiovascular system.
- oxygen consumption
- low intensity exercise
- heart failure
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