Physiology of myocardial blood flow and metabolism.

In this chapter the normal functioning of the coronary circulation has been described with major emphasis placed on the hydraulic and small vessel resistance factors in its regulation. The impact of various forms of disease to compromise effective delivery of blood flow either in general or segmentally has also been stressed. The vulnerability of the deep or subendocardial layers to ischemia has been emphasized. The distinction has been drawn between primary and secondary vasodilatation, the primary type representing effects on the arteriole, irrespective of effects on myocardial mechanical and metabolic activity, while the secondary type represents changes in response to changes in the metabolic rate. An interrelationship has been demonstrated among the several factors which regulate blood supply and affect myocardial mechanical activity.