In a canine model, coronary collateral circulation from the cardiac lumen to the myocardium increases significantly only during coronary occlusion, not during ischemia or ventricular hypertension.
Coronary collateral circulation from the cardiac lumen was studied in 36 anesthetized, open-chest dogs with hearts beating in situ. The coronary arteries were cannulated and perfused from an isolated, nonradioactive blood source while 131 I-labeled blood circulated through the cardiac lumen for 2 minutes. Ventricular fibrillation was then produced, and luminal blood samples and myocardial tissue samples were obtained for radioactive assay and calculation of the amount of luminal blood appearing as a part of the myocardial blood volume. These volumes were obtained from both ventricles and the atria under (1) normal antegrade coronary flow conditions, (2) myocardial ischemia, (3) left and right ventricular hypertension, and (4) coronary occlusion. Small quantities of luminal blood appeared in the left ventricular myocardium under normal coronary flow conditions while considerably larger amounts were found in the right ventricle and atria. There was no significant increase of the luminal contribution to the myocardial blood volume in response to the various experimental conditions except that of coronary occlusion. Although in the latter, the amount of left ventricular luminal blood was greater than with normal coronary flow conditions, right ventricular and atrial myocardial blood volumes remained greater than the left.
THOMAS W. MOIR (Thu,) studied this question.