Related Experiment Videos
Circadian changes of left ventricular ejection fraction in normal subjects
1Department of Respiratory Medicine, University Hospital, Grenoble, France.
Chronobiology International
|June 1, 1994
Summary
Healthy individuals experienced a significant drop in left ventricular ejection fraction (LVEF) upon waking. This overnight decrease in heart function returned to normal within 30 minutes and was not linked to autonomic nervous system changes.
Area of Science:
- Cardiology
- Sleep Medicine
- Physiology
Background:
- Previous studies noted decreased left ventricular ejection fraction (LVEF) in respiratory patients upon waking.
- The cause of this LVEF decrease, whether respiratory-related or physiological, was unclear.
Purpose of the Study:
- To investigate overnight changes in LVEF in healthy individuals.
- To determine if sleep and autonomic nervous system activity influence LVEF.
Main Methods:
- Eight healthy men underwent LVEF measurement using Technetium-99m red cell labeling.
- Measurements were taken at rest, before/after exercise, before sleep, and upon waking.
- Sleep parameters and sympathovagal tone (SVT) were monitored overnight.
Main Results:
- LVEF decreased significantly in several subjects upon waking, with some dropping below 30%.
- These overnight LVEF drops were not correlated with SVT or sleep patterns.
- LVEF normalized within 30 minutes after waking.
- Exercise-induced LVEF changes were consistent with existing literature.
Conclusions:
- Healthy individuals can experience dramatic overnight decreases in LVEF.
- The underlying mechanisms may involve vascular resistance or cardiac contractility variations.
- Further research is needed to elucidate the causes of these nocturnal LVEF fluctuations.