Sympathetic influences on the native canine coronary collateral circulation.
OBJECTIVE
The aim was to investigate the influence of the sympathetic nervous system on the native collateral circulation in the intact heart.


METHODS
Experiments were performed on 10 open chest dogs anaesthetised with alpha chloralose. The left anterior descending coronary artery was cannulated and embolised with 25 microns microspheres. Collateral resistance was determined from measurements of aortic pressure and retrograde flow. Additional haemodynamic measurements included left ventricular pressure and blood flow in the circumflex coronary artery.


RESULTS
Coronary embolisation decreased retrograde resistance from 41.5(SEM 6.0) to 20.1(1.9) mm Hg.ml-1.min-1 (P < 0.01). Left stellate stimulation for 60 s (10 Hz) significantly increased circumflex blood flow and decreased circumflex resistance from 2.1(0.3) to 1.6(0.2) mm Hg.ml-1.min-1. Retrograde resistance during sympathetic stimulation decreased from 19.7(1.8) mm Hg.ml-1.min-1 (P < 0.01). Transient occlusion of descending aorta resulted in changes in perfusion pressure and retrograde flow that were similar to those observed during stellate stimulation. Stellate stimulation after beta blockade with timolol (0.1 mg.kg-1) increased circumflex resistance from 1.9(0.2) to 2.3(0.3) mm Hg.ml-1.min-1 (P < 0.01) but did not alter retrograde resistance.


CONCLUSIONS
The sympathetic nervous system does not have a direct effect on native coronary collateral vessels. Increased sympathetic input to the heart does not result in a coronary steal phenomenon. The primary determinant of flow and resistance in the native collateral network during sympathetic activation is the arterial perfusion pressure.
Euler
D E
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Department of Physiology, Loyola University Medical Center, Maywood, IL 60153.
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003097:Collateral Circulation / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology*; D003327:Coronary Disease / Q000503:physiopathology; D004285:Dogs; D004558:Electric Stimulation; D055590:Electromagnetic Phenomena; D004617:Embolism; D005260:Female; D008297:Male; D010477:Perfusion; D012039:Regional Blood Flow / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*