Collateral flow prevents unintentional myocardial ischemia during antegrade cardioplegia in patients undergoing coronary artery bypass grafting.

OBJECTIVE: We evaluated, in the prevention of perioperative unintentional myocardial ischemia, the role of coronary collateral flow in patients with left anterior descending coronary artery stenosis or occlusion who underwent elective coronary artery bypass grafting. METHODS: Coronary lesions and collaterals were assessed by coronary angiography in 21 patients. Anteroseptal myocardial viability was evaluated by dobutamine echocardiography. Antegrade perfusion of cardioplegic solution was assessed by myocardial contrast echocardiography. Time-intensity curves were generated from the anteroseptal region. Twelve parameters were measured and averaged in the following four groups of patients: those with stenosis of the left anterior descending artery and poor collaterals; those with stenosis of the left anterior descending artery and good collaterals; those with occlusion of the left anterior descending artery and good collaterals; and those with occlusion of the left anterior descending artery and poor collaterals. RESULTS: Time-intensity curves were significantly different in patients with stenosis versus occlusion of the left anterior descending artery (p < 0.005); multiple comparisons with Bonferroni's correction showed that this difference was mainly a result of the impact of collateral circulation (p < 0.01). However, the role of collaterals was nonsignificant within the groups with stenosis and occlusion of the left anterior descending artery. Patients with occlusion of the left anterior descending artery and good collaterals had perfusion parameters similar to those of patients with stenosis of the left anterior descending artery (p = not significant), except for the ascending slope and time to peak values (p < 0.05 and p < 0.01, respectively), which reflected a higher flow resistance in the collateral circulation. Regional systolic function after coronary artery bypass grafting was depressed in patients with poor collaterals and poor perfusion of cardioplegic solution, as compared with findings in other subgroups. CONCLUSIONS: Incomplete myocardial protection may impair the early recovery of function after coronary artery bypass grafting.