EFFECT OF CORONARY-BYPASS GRAFTING ONTO THE SITE OF OLD MYOCARDIAL-INFARCTION AND THE RECOVERY OF CARDIAC-FUNCTION

This study investigated whether or not revascularization to the site o f old myocardial infarction can bring beneficial effects on postoperat ive cardiac function, Thirty-two patients without a history of old myo cardial infarction and 71 with a history of old myocardial infarction were included. The mean number of grafts bypassed were 2.7 and 2.8, an d the mean duration of aortic clamping was 99 min and 105 min in non-o ld myocardial infarction and old myocardial infarction patients, respe ctively. All the patients underwent simple coronary artery bypass graf ting electively. The left ventricular stroke work index in non-old myo cardial infarction and old myocardial infarction were 40.8 g-m/m(2) an d 38.9 g-m/m(2) preoperatively, and this was recovered to 41.4 g-m/m(2 ) and 38.7 g-m/m(2), respectively, at 24 hours after reperfusion (NS). Subgroups of old myocardial infarctions had high ejection fractions o f more than 50% (49) and low ejection fractions of less than 50% (22), The left ventricular stroke work index in high and low ejection fract ions was 39.7 g-m/m(2) and 36.7 g-m/m(2) preoperatively (MS), Recovery rates in both high and low ejection fractions were reduced to 74.2% a nd 84.3% at 3 h after reperfusion (P < 0.001 and P < 0.05 versus preop erative value), but were increased in the low ejection fraction by up to 102.7% and 108.5% at 6 and 12 h after reperfusion, while still rema ining reduced in the high ejection fraction at 88.8% and 88.2%, respec tively (P < 0.01). At 24 h after reperfusion, left ventricular stroke work index in the low ejection fraction was improved to 44.3 g-m/m(2) or 130% of the preoperative value, and the high ejection fraction was 37.5 g-m/m(2) or 100% (NS). This showed that a chief cause of reduced cardiac function in the low ejection fraction was mainly reversible my ocardial damage or hibernation, Preoperative mean left ventricular eje ction fractions in non-old myocardial infarctions and old myocardial i nfarctions were 73.1% and 55.9%, and these returned to 73.7% (NS) and 61.8% (P < 0.001) at 1 month post-coronary artery bypass grafting. A s imilar trend towards a significant improvement was shown in both end-d iastolic volume indices and end-systolic volume indices of patients wi th an old myocardial infarction (P < 0.001). Regional wall motion acco rding to AHA classification in patients with old myocardial infarction s was estimated from biplane left ventriculogram as normal, reduced, n one, dyskinetic and aneurysmal, and scored as 0, 1, 2, 3 and 4, respec tively. Summated scores in old myocardial infarctions was improved fro m 5.2 to 4.1 after coronary artery bypass grafting (P < 0.05). There w as a significant improvement of summated scores from 8.17 to 6.28 in t he low ejection fraction (P < 0.05); however, this was not reflected i n the high ejection fraction (3.76 to 3.0: NS). The regional wall moti on in the old myocardial infarctions that were heart bypassed to the l eft anterior ascending artery (n = 67) or to the circumflex artery (n = 40) were significantly improved at regions 2 (P < 0.05), 3 (P < 0.05 ) and 7 (P < 0.05), and that bypassed to right coronary artery (n = 50 ) was also improved at regions 3 (P < 0.05), 5 (P < 0.05) and 7 (P < 0 .001). This shows that augmentation of regional blood flow by coronary artery bypass grafting will contribute to awakening the hibernated my ocardium even in the old myocardial infarction. (C) 1998 The internati onal Society for Cardiovascular Surgery. Published by Elsevier Science Ltd. All rights reserved.