Abstract
Chronic occlusion of the left circumflex artery and of the right coronary artery was produced in 21 dogs with the Ameroid technique. Thirteen animals survived and myocardial infarction was avoided in 12 due to the development of a network of collateral vessels. The functional state of the collaterals was tested by physiologic and pharmacologic stimuli using Tracer Microspheres and 133-Xe as indicators of coronary flow and of collateral flow. Increases in heart rate up to 160 beats per minute caused mild coronary vasodilation and homogeneous distribution of left ventricular myocardial flow. Carbochromene caused moderate-to-marked increase in coronary blood flow. Collateral flow rose also but less than coronary flow. Carbochromene plus tachycardia caused a marked increase in coronary flow but collateral flow to the subendocardial layers actually decreased below control values. An explanation of these findings is offered on the basis of relations between the collateral and coronary resistances.
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