Recent Views On Integrated Coronary Control: Significance Of Non‐Uniform Regional Control Of Coronary Flow Conductance

Abstract

1. Previous work from this laboratory and others has shown that powerful autonomic influences modulate coronary flow. In particular, the parasympathetic nervous system produces vasodilatation when activated by baroreceptors via the vagus nerve. 2. Differences exist in baroreflex coronary vasodilator mechanisms among the right, circumflex and anterior descending coronary vascular beds in the awake chronically instrumented dog. 3. Our hypothesis is that neurogenic acetylcholine acting from the adventitial side and endothelial nitric oxide from the luminal aspect of coronary smooth muscle compete with powerful intrinsic myogenic constrictor mechanisms to regulate regional flow conductance. 4. There is also increasing evidence that heterogeneity of control systems exists in different-sized coronary vessels within an individual coronary vascular bed. 5. It is concluded that coronary vessels in vascular beds can no longer be assumed to respond in a uniform manner to neural, myogenic, metabolic or humoral factors. 6. These new perspectives of regional control mechanisms have important implications for understanding pathophysiological mechanisms inducing and sustaining tachyarrhythmias involved in ischaemic heart disease.

Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats

“…These differences in compressive forces result in almost continuous flow in the right coronary bed, whereas flow in the anterior left descending bed occurs mainly during diastole (24,30). Furthermore, when aortic pressure rises and the ventricle is loaded, the right coronary bed exhibits reflex increase of blood flow, whereas the anterior left descending coronary artery vasodilates poorly (29). Such differences in the hemodynamic profile between the left (LCA) and right coronary arteries (RCA) may underline differences in the regulation of basal tone between these two vascular beds.…”

“…1B and 3). The greater contribution of Kv channels in RCA could explain the heterogeneity in autoregulatory mechanisms along the coronary vascular tree (10,29) and could be linked to the difference in the transmural pressure between the LCA and the RCA. Particularly, the left anterior descending branch appears to be less protected than the RCA and vasodilates poorly when aortic pressure rises and the left ventricle is loaded (29).…”