Affiliation:
1. Department of Medicine, Medical College of Virginia/Virginia Commonwealth University, Richmond.
Abstract
BACKGROUND
Left ventricular sympathetic afferent nerves are located mainly in superficial epicardial layers. Reflex excitatory responses mediated by sympathetic afferent nerves have been observed during myocardial ischemia in cats and humans but not in dogs. Previous canine studies have induced ischemia by occlusion of a coronary artery. Extensive collateral circulation in the canine heart may limit ischemia of epicardial layers during simple coronary occlusion, resulting in little stimulation of sympathetic afferent nerves and minimal reflex excitatory responses.
METHODS AND RESULTS
In anesthetized dogs with sinoaortic and vagal deafferentation, we determined whether reflex sympathoexcitatory responses mediated by sympathetic afferents occurred during transmural myocardial ischemia. Reflex sympathoexcitation was quantitated by direct recording from either efferent renal (n = 20) or cardiac (n = 5) sympathetic nerves. Responses of arterial pressure and efferent sympathetic nerve activity were measured during simple occlusion of the anterior descending artery (LAD alone) and during LAD occlusion with a circumflex stenosis (LAD + CIRC). This circumflex stenosis was adjusted to abolish coronary vasodilator reserve without reducing basal flow. We observed significantly greater reflex increases in renal (32 +/- 5%) and cardiac (58 +/- 15%) nerve activity during LAD + CIRC than during LAD alone (14 +/- 6% and 8 +/- 7%, respectively). Reflex changes in renal nerve activity during LAD + CIRC were abolished by interruption of cardiac sympathetic afferent pathways (n = 5). In eight experiments, myocardial blood flow was measured during the two coronary occlusions. These experiments confirmed that LAD + CIRC elicited more transmural ischemia in the LAD distribution than did LAD alone. However, these experiments also revealed that LAD + CIRC elicited endocardial ischemia in the circumflex distribution. In five additional experiments, regional sympathetic deafferentation of the posterior left ventricle by epicardial application of 88% phenol along the atrioventricular groove had no significant effect on renal nerve responses to LAD + CIRC (36 +/- 5% increase before phenol versus 31 +/- 3% increase after phenol). These results indicate that endocardial ischemia in the circumflex distribution did not contribute to the reflex increases in nerve activity that were noted during LAD + CIRC.
CONCLUSIONS
Reflex sympathoexcitation mediated by cardiac sympathetic afferents can be elicited in dogs. However, these responses are significant only during ischemia that is transmural and involves the superficial epicardial layers of the left ventricle.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine
Reference27 articles.
1. Excitation of afferent cardiac sympathetic nerve fibres during myocardial ischaemia
2. Excitation of afferent cardiac sympathetic nerve fibers during coronary occlusion;Uchida Y;Am JPhysiol,1974
3. A sympathetic reflex elicited by experimental coronary occlusion;Malliani A;Am J Physiol,1969
4. Contrasting reflex influences of cardiac afferent nerves during coronary occlusion;Weaver LC;Am J Physiol,1981
5. Autonomic disturbance at onset of acute myocardial infarction;Webb SW;BrMedJ,1972
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