COLLATERAL FLOW PREVENTS UNINTENTIONAL MYOCARDIAL-ISCHEMIA DURING ANTEGRADE CARDIOPLEGIA IN PATIENTS UNDERGOING CORONARY-ARTERY BYPASS-GRAFTING

Objective: We evaluated, in the prevention of perioperative unintentio nal myocardial ischemia, the role of coronary collateral flow in patie nts with left anterior descending coronary artery stenosis or occlusio n who underwent elective coronary artery bypass grafting, Methods: Cor onary lesions and collaterals were assessed by coronary angiography in 21 patients, Anteroseptal myocardial viability was evaluated by dobut amine echocardiography, Antegrade perfusion of cardioplegic solution w as assessed by myocardial contrast echocardiography, Time-intensity cu rves were generated from the anteroseptal region, Twelve parameters we re measured and averaged in the following four groups of patients: tho se with stenosis of the left anterior descending artery and poor colla terals; those with stenosis of the left anterior descending artery and good collaterals; those with occlusion of the left anterior descendin g artery and good collaterals; and those with occlusion of the left an terior 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 group s with stenosis and occlusion of the left anterior descending artery, Patients with occlusion of the left anterior descending artery and goo d collaterals had perfusion parameters similar to those of patients wi th stenosis of the left anterior descending artery (p = not significan t), except for the ascending slope and time to peak values (p < 0.05 a nd p < 0.01, respectively), which reflected a higher flow resistance i n the collateral circulation, Regional systolic function after coronar y artery bypass grafting was depressed in patients with poor collatera ls and poor perfusion of cardioplegic solution, as compared with findi ngs in other subgroups, Conclusions: Incomplete myocardial protection may impair the early recovery of function after coronary artery bypass grafting.