Document Detail

Reduced oxygen uptake increase to work rate increment (DeltaVO2/DeltaWR) is predictable by VO2 response to constant work rate exercise in patients with chronic heart failure.
MedLine Citation:
PMID:  12811568     Owner:  NLM     Status:  MEDLINE    
Patients with reduced peak oxygen uptake (VO2) due to chronic heart failure (CHF) exhibit abnormal VO2 kinetics even during mild to moderate exercise. This is characterized by a reduced ratio of the VO2 increase to the work rate increment (DeltaVO2/DeltaWR) during ramp exercise, and by a slow increase in VO2 during constant work rate exercise. Because the slow kinetics alone is unlikely to explain the reduced DeltaVO2/DeltaWR on theoretical grounds, we can postulate that the linearity between work rate and VO2 may be impaired when exercise is imposed in a ramp fashion. The present study was designed to address this issue. In 21 CHF patients and 17 normal controls, we performed both symptom-limited exercise testing (15 W. min(-1) ramp) and a constant work rate exercise test (0 W followed by 50-W step). The VO2 step response was used to mathematically derive the hypothetical VO2 ramp response by time integration. Although peak VO2 and work rate were both significantly lower in patients, the attenuation in peak VO2 was more prominent ( p<0.05), which could be explained by a lower DeltaVO2/DeltaWR in patients compared with controls [8.1 (SD 1.0) and 9.8 (0.5) ml. min(-1). W(-1), p<0.01]. The hypothetical DeltaVO2/DeltaWR derived from the VO2 step response was also significantly lower in patients [8.7 (1.0) and 10.0 (0.7) ml. min(-1). W(-1), p<0.01]. The hypothetical and measured DeltaVO2/DeltaWR were highly correlated ( r=0.78, p<0.001). Thus, we can reasonably predict the VO2 ramp response from the VO2 response to a step increase in work rate, indicating that linearity between VO2 and work rate is held constant irrespective of loading patterns. Additional studies, such as those including evaluation of anaerobic bioenergetics, are needed to further elucidate the precise mechanism(s) of this phenomenon.
Mamoru Toyofuku; Hiroshi Takaki; Masaru Sugimachi; Toru Kawada; Yoichi Goto; Kenji Sunagawa
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Publication Detail:
Type:  Clinical Trial; Controlled Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't     Date:  2003-06-13
Journal Detail:
Title:  European journal of applied physiology     Volume:  90     ISSN:  1439-6319     ISO Abbreviation:  Eur. J. Appl. Physiol.     Publication Date:  2003 Sep 
Date Detail:
Created Date:  2003-09-23     Completed Date:  2004-09-13     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100954790     Medline TA:  Eur J Appl Physiol     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  76-82     Citation Subset:  IM    
Division of Cardiology, Department of Medicine, National Cardiovascular Center, Suita, Japan.
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MeSH Terms
Chronic Disease
Energy Transfer*
Exercise Test / methods
Heart Failure / physiopathology*
Middle Aged
Oxygen Consumption*
Physical Exertion / physiology*
Statistics as Topic

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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