Coronary collateral circulation as an important factor to modify the ischemic injury of the myocardium in coronary ligated dogs.

Effect of coronary ligation on epicardial and intramyocardial ST-segment voltage was investigated in 121 dogs. After ligation of the anterior descending coronary artery, marked ST-elevation, more than 2 mV, was detected in 102 dogs (Group-I) in epicardial lead of the area which was nourished by the ligated coronary artery. In 7 dogs (Group-II), coronary ligation produced negligible changes in ST-segment voltage in epicardial lead, while significant ST-elevation was observed in the leads of middle and inner layers of the myocardium. Systemic hemo-dynamic parameters showed no statistically significant difference between the 2 groups. Coronary collateral indices, however, revealed the significant difference between them. Systolic peripheral coronary pressure was 29.3 +/- 3.1 mmHg in Group-I and 59.2 +/- 10.6 mmHg in Group-II (P less than 0.05). Retrograde flow was also greater in Group-II (14.8 +/- 4.4 ml/min) than in Group-I (1.3 +/- 0.5 ml/min) (p less than 0.01). Diversion of retrograde flow produced a marked ST-elevation in Group-II. Restoration of retrograde flow to the myocardium immediately decreased the ST-segment voltage. These results suggest that spontaneously developed collaterals have an important function for the prevention of the occurrence of ischemic injury after coronary ligation in dogs.