The role of coronary collateral circulation has been a subject of great interest and controversy. The functional significance of collateral circulation was evaluated in 125 patients with total coronary occlusion of left anterior descending artery(LAD) or right coronary artery(RCA).

Patients were classified into two groups. Group 1:patients with angina pectoris(AP), Group 2:patients with a first transmural myocardial infarction(MI) within 3 months of symptom onset, Clinical variables, resting and exercise electrocardiogram(EKG) were analyzed with angiographic findings. Collateral fillings were graded from 0 to 3 : 0=none ; 1=filling of side branches only ; 2=partial filling of the epicardial segment ; 3=complete filling of epicardial segment. The wall motion of each segment was scored from 1 to 5:1=normal ; 2=mild to moderate hypokinesia ; 3=severe hypokinesia ; 4=akinesia ; 5=dyskinesia. The score of the 5 segments were added to yield a total LV score.

There is a higher prevalence of good collaterals and multivessel disease in group 1 than in group 2(83% vs 53%, 54% vs 30%, respectively, p<0.05). The left ventricular ejection fraction(LVEF), left ventricular end-diastolic pressure(LVEDP) and segmental wall motion score were significantly better in group 1 than group 2(68.9±13.4% vs 50.5±12.6%, 15.0±7.3 vs 20.3±8.8mmHg, 6.5±2.2 vs 9.6±2.3, respectively, p<0.05). In spite of total coronary occlusion, 61% of AP patients had normal resting EKG but 96% of patients who underwent treadmill test proved to be positive. The proportions of well-developed collaterals in 3 groups divided according to the interval between onset of MI and angiography(within 1 day, 2 to 14 days, 15 days to 3 months)were 13%, 54% and 60%. There were no significant difference in LVEF, segmental wall motion score and LVEDP in MI patients with poorly-developed collaterals and well-developed collaterals(49.1±15.7 vs 46.4±10.1%, 11.1±2.2 vs 10.9±1.4 and 24.3±9.7 vs 20.3±7.0mmHg, p=NS). The degree of collateral development is higher in MI with RCA occlusion compared with that of LAD occlusion(1.1±1.0 vs 2.0±1.0, p<0.05).

Collateral circulation can prevent myocardial ischemia and preserve myocardial function in a significant number of patients with AP but do not provide protection against exercise-induced myocardial ischemia in a majority of patients with AP. Well-developed collaterals are uncommonly present within 1 day after MI, but subsequently develop and are generally demonstrable after 2 weeks. Collateral vessels in patients with MI have no beneficial effects on preserving myocardial function.