Effect of carotid sinus nerve stimulation on coronary blood flow in myocardial ischaemia: role of the collateral vessels.

The carotid sinus nerves of dogs were electrically stimulated to reveal reflex effects exerted on the coronary blood flow both in normal and ischaemic states. Myocardia ischaemia was produced by occlusion of the left anterior descending (LAD) coronary artery. In 10 experiments the coronary sinus outflow was measured as an index of the overall coronary flow; in 30 cases the local myocardial blood flow was registered by means of the heat clearance technique. In the overall coronary flow carotid sinus nerve stimulation (CSNS) elicited coronary dilatation. After acute LAD occlusion this effect was slightly potentiated. A similar but significantly greater potentiation was observed in the local reflex vascular dilatation recorded with the aid of the thermal probes immediately after LAD occlusion when the myocardial area explored was supplied exclusively by collateral channels. 24-48 hours and 5-64 days after the coronary ligation the effect of the CSNS on the local blood flow was tested in the developing and the regenerative phases of the myocardial infarction. In both phases an enhanced reflex dilatation was found in the collateral-dependent ischaemic areas as compared to the myocardial areas supplied by the normal vessels. The results suggest that reflexly induced intrinsic redistribution of the myocardial blood flow is one of the mechanisms responsible for the therapeutical effects of the CSNS.