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Circulatory effects in healthy young men of atrial pacing at rest and during isometric handgrip
Insights
Atrial pacing increases cardiac output and alters blood flow responses during isometric handgrip exercise in healthy individuals. Handgrip primarily causes vasoconstriction in vascular beds beyond the forearm.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Isometric handgrip exercise is a common stressor used to study cardiovascular responses.
- Atrial pacing allows for controlled manipulation of heart rate and cardiac output.
Purpose of the Study:
- To investigate the cardiovascular effects of isometric handgrip when heart rate and cardiac output are fixed using atrial pacing.
- To determine the influence of atrial pacing on systemic and forearm vascular resistance during handgrip.
Main Methods:
- Utilized atrial pacing to maintain a fixed heart rate (mean 109 beats/min) and cardiac output.
- Measured cardiovascular responses, including systemic and forearm vascular resistance, at rest and during isometric handgrip (1/3 maximal voluntary contraction).
Main Results:
- At rest, atrial pacing increased cardiac output and forearm blood flow, while decreasing total systemic and forearm vascular resistance.
- During handgrip, total systemic resistance rose irrespective of pacing.
- Forearm vascular resistance decreased slowly with pacing during handgrip, but remained unchanged without pacing.
Conclusions:
- Atrial pacing effectively increases cardiac output in healthy young volunteers.
- Isometric handgrip induces vasoconstriction in vascular beds other than the resting forearm, independent of pacing-induced changes in cardiac output.
Abstract:
1. The influence of a fixed heart rate and cardiac output on the cardiovascular response to isometric handgrip at one third of maximal voluntary contraction has been studied by means of atrial pacing. 2. At rest, atrial pacing with a mean heart rate of 109 beats/min increased cardiac output and forearm blood flow while total systemic and forearm vascular resistance decreased. 3. During handgrip, total systemic resistance increased both with and without pacing. A slow lowering of forearm vascular resistance was noted in the former situation, no change in the latter. 4. It is concluded that atrial pacing per se increases cardiac output in healthy, young volunteers. Handgrip elicits a vasoconstriction on other vascular beds than the resting forearm.