Maximal coronary flow and the concept of coronary vascular reserve.

CORONARY FLOW can usually be increased above resting levels by reactive hyperemia after transient coronary arterial occlusion,'-" exercise,7 11, 1421 pacing,22-26 or injection of agents like dipyridamole,' 17. 18 20 21. 27-37 other vasodilating -7. 10, 11. 30. 38 agents,5 or hyperosmolar iodinated contrast media.4 693 If the stimulus produces maximal coronary vasodilatation, then the increment of coronary flow above the resting level will be maximal. This increment, often termed the "coronary vascular reserve," is beginning to be measured in human beings to give information about the coronary vascular bed.9 13, 15. 17. 19-29. 33A3 However, it is easy to misinterpret the information, so that it is important to understand the basic physiology that underlies the concept of coronary vascular reserve.