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Influence of the autonomic nervous system on coronary blood flow during partial stenosis
Insights
The autonomic nervous system influences coronary blood flow (CBF) changes during partial coronary stenosis. Cardiac sympathetic tone significantly impacts CBF patterns, while vagal nerve effects require further investigation.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Research
- Platelet Aggregation Studies
Background:
- Partial coronary stenosis causes cyclical changes in coronary blood flow (CBF).
- These CBF oscillations result from platelet aggregation and disaggregation at the occlusion site.
- The autonomic nervous system's role in this phenomenon was previously undetermined.
Purpose of the Study:
- To investigate the influence of the autonomic nervous system on cyclical CBF changes during partial coronary stenosis.
- To examine the effects of vagotomy and stellectomy on CBF oscillations in dogs with coronary stenosis.
Main Methods:
- Studied 20 anesthetized dogs with partial stenosis of the left circumflex coronary artery.
- Assessed the impact of bilateral vagotomy and cervical stellectomy on CBF oscillations.
- Investigated responses to stellate ganglion stimulation and epinephrine infusion, and the effect of atropine on flow changes.
Main Results:
- Bilateral vagotomy reduced the frequency of CBF oscillations (p < 0.05).
- Bilateral cervical stellectomy significantly reduced both the frequency (p < 0.025) and magnitude (p < 0.05) of CBF changes.
- Epinephrine infusion provoked CBF changes, while atropine attenuated them, suggesting a role for sympathetic tone and potentially direct platelet effects.
Conclusions:
- Cardiac sympathetic tone significantly influences coronary blood flow patterns during critical coronary stenosis.
- The vagus nerve's afferent limb may mediate effects via increased catecholamines, but the efferent vagal role needs further clarification.
Abstract:
Partial coronary stenosis produces cyclical changes in coronary blood flow (CBF) which are the result of spontaneous aggregation and disaggregation of platelet plugs at the site of occlusion. The possible influence of the autonomic nervous system on this phenomenon has not been hitherto determined. The present study was performed in 20 chloralose-anesthetized dogs in which the effects of bilateral vagotomy and stellectomy were examined during partial stenosis of the left circumflex coronary artery. Vagotomy reduced the frequency of CBF oscillations from 11.5 +/- 2.1 to 5.0 +/- 2.1 cycles/hr (p less than 0.05). The magnitude of the flow changes was reduced from 13.8 +/- 4.0 to 9.7 +/- 3.0 ml/min (NS). Bilateral cervical stellectomy reduced the frequency of CBF changes from 7.8 +/- 2.7 to 3.7 +/- 1.3 cycles/hr (p less than 0.025) and their magnitude from 10.6 +/- 2.5 to 5.6 +/- 1.8 ml/min (P less than 0.05). In five dogs in which cyclical CBF changes were reduced or abolished by decentralizing the stellate ganglia, electrical stimulation of the main body of the left ganglion evoked or enhanced the oscillations in two dogs, had no distinct effect in two dogs, and elicited no response in one dog. A 5-minute infusion of 0.5 microgram/kg/min and 0.75 microgram/kg/min epinephrine (four dogs) provoked the CBF changes in all animals for a period of 5 to 10 minutes. Blockade of muscarinic receptors by 0.2 mg/kg atropine resulted in a significant attenuation of flow changes, which may at least in part have been due to a direct effect of atropine on platelets. We conclude that cardiac sympathetic tone significantly influences the CBF pattern during critical coronary stenosis. While the afferent limb of the vagus may in part mediate this effect via a reflex increase of adrenal medullary catecholamines, the role of the efferent vagus awaits further clarification.