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The effect of coronary artery constriction and ligation, and graded changes in coronary arterial blood flow on myocardial contractile force was studied in anesthetized open-chest dogs. The coronary constriction and stepwise decreases in coronary blood flow using a Sigmamotor pump decreased myocardialcontractile force essentially in proportion to the decrements of the coronary flow. On the other hand, the increased coronary blood flow beyond physiological ranges did not increase contractile force. The coronary ligation decreased myocardial contractile force of the ischemic or injured areas of the ventricle, but increased the contractile force in the healthy area of the ventricle. Under these conditions, norepinephrine administration increased the contractile force of the healthy portion of the ventricle, whereas the myocardial contractile force of the injured portion remained essentially unchanged.
Jiro Nakano (1966) studied this question.