Regional Sympathectomy of Canine Ventricle: Effect on Distribution of Myocardial Blood Flow

Abstract

In the coronary bed both α- and β-adrenergic receptors have been demonstrated (1, 2, 4, 5, 8, 13), but their significance under strictly physiological conditions has remained obscure. Therefore, in the unanesthetized dog without any premedication, we studied the question whether sympathetic activity can modify significantly myocardial blood flow by a direct effect on coronary arterioles, in addition to its metabolic effect on the myocardium. Since coronary arterioles cannot be denervated selectively, we have chosen an approach, by which regional myocardial blood flow was estimated in a defined denervated section of the heart and compared to that of the normally innervated control section of the same heart. Hemodynamic parameters affecting myocardial blood flow, such as heart rate, coronary perfusion pressure, left ventricular pre- and afterload are identical for the normally innervated and the denervated portion of the same ventricle. Therefore, differences in myocardial perfusion can be — at least under certain conditions — related to the direct effects of sympathetic innervation on coronary vessels. Two basically different experimental techniques have been used to obtain a defined section of the ventricle without sympathetic innervation.