Journal
EUROPEAN JOURNAL OF HEART FAILURE
Volume 6, Issue 7, Pages 917-926Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ejheart.2004.02.010
Keywords
heart failure; efficiency; cardiopulmonary exercise testing; oxygen consumption; heart failure symptoms
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Funding
- NIA NIH HHS [K12 AG00503] Funding Source: Medline
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Previous studies of biomechanical efficiency (external work/energy input - Watt/O-2 consumed) in heart failure (HF) using cardiopulmonary exercise testing (CPET) and magnetic resonance spectroscopy (MRS) have had discordant results with increased efficiency by CPET and decreased efficiency by MRS. Aims: Compare biomechanical efficiency of HF subjects and normal controls during steady state (SS = 35 W for 6 min) and ramp cycle ergometer exercise. The hypothesis was that HF subjects would have impaired biomechanical efficiency that correlated with HF symptoms. Methods: Biomechanical efficiency used the actual Vo(2) during exercise and recovery. Gross (Vo(2) above zero), Net (Vo(2) above the resting Vo(2)) and Work (Vo(2) above the unloaded pedaling Vo(2)) efficiencies were calculated. Results: HF subjects had an 18% higher Vo(2) during SS exercise (P= 0.029). Biomechanical efficiency was reduced during SS exercise (gross - 15%, P= 0.019, net - 15%, P= 0.062, and work - 35%, P= 0.002). Gross Efficiency during SS exercise had the strongest correlation with HF symptoms (r = 0.55). During ramp exercise gross ( - 26%), net ( - 10%) and work ( - 8%) biomechanical efficiency were all reduced (all P< 0.05). The slope of the Vo(2)/Watt relationship during ramp exercise had the best correlation with HF symptoms (r= 0.46). Conclusions: HF subjects have an increased O-2 cost/Watt during SS and ramp exercise that correlates with HF symptoms of fatigue and breathlessness. Methods to improve biomechanical efficiency in HF subjects by exercise training or medications may improve the symptoms and the impaired exercise capacity associated with HF. (C) 2004 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.
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