Tonic influence of the sympathetic nervous system on myocardial reactive hyperemia and on coronary blood flow distribution in dogs.

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Abstract
In 2 groups of dogs the effect of right and/or left stellectomy on myocardial reactive hyperemia (RH) and coronary blood flow distribution was studied. In the 1st group of 14 conscious dogs, the percent repayment of flow debt produced by a 10 s occlusion of the left circumflex coronary artery was recorded with a Doppler ultrasonic flow probe and a hydraulic vascular occluder. Dogs were studied under control conditions after right stellectomy, left stellectomy and after administration of propranolol and phentolamine. Right stellectomy did not affect RH. RH was significantly increased by left stellectomy from 476 .+-. 71%-622 .+-. 86% (+31%) at the spontaneous heart rate and from 407 .+-. 51%-577 .+-. 106% (+42%) during pacing. Propranolol significantly reduced RH from 447 .+-. 25%-390 .+-. 27% (-13%) at the spontaneous heart rate and from 456 .+-. 25%-311 .+-. 24% (-32%) during pacing. Phentolamine significantly increased RH from 419 .+-. 63%-517 .+-. 71% (+23%). Propranolol was effective after bilateral stellectomy, whereas phentolamine was not effective after left stellectomy. In the 2nd group of 14 anesthetized dogs with constant heart rate (15 .mu.m) microspheres were injected twice into the left atrium. The 1st injection provided a control measurement; in 9 dogs the 2nd injection was made after left stellectomy. Left stellectomy significantly increased the left ventricular endocardial to epicardial ratio from 1.7 .+-. 0.03-1.23 .+-. 0.04. The sympathetic nervous system apparently has a tonic influence on coronary circulation, and left stellectomy may increase the ability of the coronary bed to dilate and improve the endocardial perfusion.