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Exercise capability in heart failure: is cardiac output important after all?
A J Cowley1, L J Fullwood, A F Muller
1Department of Medicine, University Hospital, Queen's Medical Centre, Nottingham, UK.
Lancet (London, England)
|March 30, 1991
Summary
Cardiac output influences exercise capacity in heart failure patients when they self-pace walks, but not during lab treadmill tests. This finding aids in understanding heart failure patient exercise limitations.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Assessing exercise capability is crucial for managing severe chronic heart failure.
- Cardiac output is a key indicator of cardiovascular function.
Purpose of the Study:
- To investigate the relationship between cardiac output and exercise tolerance in severe chronic heart failure patients.
- To compare exercise capability assessments using different methods against cardiac output measurements.
Main Methods:
- 39 patients with severe chronic heart failure underwent various exercise tests.
- Exercise tolerance was measured via treadmill tests and self-paced corridor walks.
- Customary activity was assessed using step counting.
- All exercise measures were compared with cardiac index (cardiac output normalized to body surface area).
Main Results:
- A poor correlation was found between cardiac index and treadmill-assessed exercise tolerance (r = 0.191, p = 0.245).
- Moderate correlations were observed between cardiac index and self-paced corridor walk tests (r = -0.404 to -0.516, p = 0.001-0.015).
- Step counting for customary activity showed a better correlation with cardiac index (r = 0.537, p < 0.001).
Conclusions:
- Cardiac output appears to be a significant factor in exercise capability when patients self-select their walking pace.
- Cardiac output may not accurately reflect exercise capacity during standardized laboratory treadmill tests in this population.
- Self-paced activity measures may offer a more relevant assessment of functional capacity in severe chronic heart failure.
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