Key result
Atropine altered the normal heart rate response to standing by abolishing rebound R-R interval lengthening, demonstrating that the initial response is primarily under vagal control.
Why the study?
What are the autonomic mechanisms underlying the initial heart rate response to standing in normal subjects?
Population
Normal subjects (n=9 for initial analysis, n=23 for reproducibility, n=4 for tilt vs standing)
Comparison
Pharmacological autonomic blockade and postural… vs Baseline/normal response without pharmacological…
Design
Other
Authors
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May inform orthostatic test interpretation in normals; leaves open roles in disease states.
What are the autonomic mechanisms underlying the initial heart rate response to standing in normal subjects?
The initial heart rate response to standing is primarily mediated by vagal withdrawal, with rebound lengthening driven by muscular activity rather than the speed of postural change.
Ewing et al. (1980) studied Healthy volunteers (n=36). Atropine and propranolol vs. Unblocked state was evaluated on R-R interval changes during standing. Atropine altered the normal heart rate response to standing by abolishing rebound R-R interval lengthening, demonstrating that the initial response is primarily under vagal control.
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