Circulatory effects of carotid sinus nerve stimulation in dogs with reference to coronary flow and resistance

Abstract only The effects of electrical stimulation of the carotid sinus nerves upon heart rate, myocardial function, circulatory dynamics, and coronary flow were studied in the anesthetized, open-chest dog. Carotid sinus nerve stimulation produced a transient profound bradycardia, which was abolished by vagotomy, and a more sustained, less marked, slowing of the heart, which became less marked after propranolol. The effects on cardiac output were variable. Significant drops in aortic pressure and systemic resistance were observed. Anterior descending coronary arterial flow also decreased significantly, but the changes in calculated coronary vascular resistance were variable. A disproportionate reduction in coronary blood flow was observed relative to the decrease in myocardial oxygen consumption. Under the conditions of our experiment, carotid sinus nerve stimulation significantly decreased cardiac work, arterial pressure, and myocardial contractility, and probably produced some coronary vasoconstriction secondary to the reduction in myocardial oxygen demand.