Pharmacology of the Coronary Circulation

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Abstract
Data accumulated by the nitrous oxide method in intact anesthetized dogs and in man appear to be comparable, and without significant inter species variation. Available information has contributed considerably to understanding of clinical activity of cardiovascular drugs and has caused revision of concepts of the mechanism of action of many pharmacologic agents. Although an agent that increases coronary flow and elevates the coronary sinus O2 content would formerly have been predicted to be effective in relieving anginal pain in a subject with atherosclerotic coronary vascular disease, experience has shown that it is not helpful. A drug which fails to increase the coronary sinus blood O2 content, or to increase myocardial blood flow, would not have been predicted to be effective in relieving angina pectoris, yet experience has shown that such agents frequently are beneficial. Either the concept that effectiveness of drug of cardiovascular disease can be predicted from known hemodynamic effects is erroneous, or the wrong parameters have been selected for examination. One of the important factors would appear to be change in major coronary artery size. Dilatation of the large coronary arteries on the surface of the heart may be more important than dilatation of the resistance vessels which presumably control total coronary blood flow. Present understanding of coronary hemodynamics is related chiefly to the gross circulation rather than the microcirculation, and hence probably does not supply the information really required.