An electrographic study on the functional capacity of the coronary collateral circulation in dogs with chronic...

The functional capacity of coronary collaterals was investigated under resting and stress conditions in 15 dogs with chronic occlusion of the anterior descending coronary artery. ST-elevation in epicardial and intramyocardial electrograms was used for assessing the degree of regional myocardial ischemia. In resting condition, epicardial and intramyocardial electrograms from collateral, intermediate and circumflex areas revealed no significant ischemic changes. In 6 of 15 dogs in which atrial pacing was performed, ST-elevation appeared in electrograms from collateral and intermediate areas. In another 9 dogs, pacing tachycardia produced no significant changes in all electrograms. In these dogs more than 50% constriction of the donor coronary artery was necessary to induce ST-elevation in electrogram from collateral area. These findings indicate that the coronary collateral vessels in dog play beneficial role to prevent the myocardium from ischemic injury under stress condition, although their functional capacity is not comparable to that of normal coronary artery.