Lung-to-lung circulation times during exercise in heart failure

Norman R. Morris, Eric M. Snyder, Kenneth C. Beck, Bruce D. Johnson

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Circulation time (the transit time for a bolus of blood through the circulatory system) is a potential index of cardiac dysfunction in chronic heart failure (HF). In healthy subjects, circulation time falls as cardiac output (Q) rises during exercise, however little is known about this index in HF. In this study we examined the relationship between lung-to-lung circulation time (LLCT) during exercise in ten HF (53 ± 14 year, resting ejection fraction = 23 ± 8%) and control subjects (51 ± 18 year). We hypothesized that HF patients would have slower LLCT times during exercise when compared to control subjects. Each subject completed two identical incremental exercise tests during which LLCT was measured in one test and Q measured in the other. Q was measured using the open circuit C2H2 washin technique and circulation time measured using an inert gas technique. In HF patients and control subjects, LLCT decreased and Q increased from rest (HF:LLCT = 53.6 ± 8.2 s, Q = 4.3 ± 1.1 1 min-1; control: LLCT = 55.3 ± 10.9 s, Q = 4.5 ± 0.5 min-1) to peak exercise (HF:LLCT = 20.6 ± 3.9* s, Q = 8.8 ± 2.5* l min-1; control:LLCT = 14.9 ± 2.4 s, Q = 16.5 ± 1.2 l min-1; *P < 0.05 vs control). LLCT was significantly (P < 0.05) slower for the HF group when compared to the control group during submaximal exercise and at peak exercise. However, at a fixed Q the HF subjects had a faster LLCT. We hypothesize that the faster LLCT at a fixed Q for HF patients, may be the result of a more intensive peripheral vasoconstriction of non-active beds and a better redistribution of blood flow.

Original languageEnglish (US)
Pages (from-to)621-627
Number of pages7
JournalEuropean Journal of Applied Physiology
Volume106
Issue number4
DOIs
StatePublished - 2009
Externally publishedYes

Bibliographical note

Funding Information:
Acknowledgments The authors of this study would like to thank Kathy O’Malley and Angela Heydmann for their assistance in the data collection and management of this project. This work was supported in part by National Institute of Health grant HL71478, the Heart Foundation Research Centre and Griffith University.

Keywords

  • Circulation time
  • Exercise
  • Heart failure

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