Aspects of coronary vasomotor regulation.

Abstract

Matching the supply of blood and oxygen to the myocardial demand for oxygen is an essential function of the coronary regulatory system. The heart cannot tolerate a deficit of oxygen for more than a few seconds without harmful consequences, so that the regulatory system must respond rapidly to changes in oxygen demand or perfusion pressure. The matching of oxygen supply to myocardial oxygen demand can be examined in three main ways. One of them is to test autoregulation which may be defined as the response to a change in perfusion pressure when myocardial oxygen demand remains unchanged. To do this in the heart, the coronary artery must be cannulated so that changes in perfusion pressure have no or relatively little effect on myocardial oxygen demand. The second method is to examine the response during constant perfusion pressure to changed myocardial oxygen demand which may either be increased by pacing, increases in cardiac pressure or volume work, or infusion of metabolic stimulators like calcium or catecholamines, or may be decreased by decreasing cardiac pressure or volume work or by decreasing contractility. A subset of these experiments is to examine maximal flows induced by severe exercise or very rapid pacing. The third method is to examine the reactive hyperemic response; coronary flow is stopped for several seconds, and the hyperemic response after flow is restored is examined. It is possible that all these three methods are examining the same regulatory systems, except that reactive hyperemia only examines decreases in oxygen supply and definitely produces transient ischemia.KeywordsNitric OxideMyocardial Blood FlowAtrial Natriuretic PeptideCoronary FlowAdenosine DeaminaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.