Myocardial protection with high-dose beta-blockade in acute myocardial ischemia

Objective: The risk of postoperative cardiac dysfunction is markedly increa sed by emergency coronary artery bypass grafting in the presence of acute m yocardial ischemia. High dose beta-blockade during continuous coronary perf usion has been suggested as an alternative to conventional cardioplegia and this technique has been applied successfully in high risk patients for cor onary artery bypass grafting (CABG) surgery. This study compared high dose beta-blockade with esmolol to continuous warm blood cardioplegia in a clini cally oriented model of acute left ventricular (LV) ischemia and reperfusio n. Methods: Twelve dogs were subjected to 60 min of regional LV ischemia by left anterior descending branch (LAD) ligation. Cardiopulmonary bypass (CP B) and aortic crossclamp were applied after 45 min of ischemia. Thereafter, high dose beta-blockade during continuous coronary perfusion (ESMO, n = 6) or antegrade continuous warm blood cardioplegia (WBC, n = 6) were maintain ed for 60 min. Myocardial water content (measured from endomyocardial biops ies using a microgravimetric technique), global LV function (preload recrui table stroke work: PRSW), and regional LV function (echocardiographic wall motion score) were determined at baseline and after weaning from CPB. Resul ts: During aortic crossclamp interstitial edema formation was significantly higher in the WBC group with an average water gain of 2.2 +/- 0.49 vs. 0.7 6 +/- 0.12% in the ESMO group. Thereafter, edema resolved in both groups, b ut myocardial water gain remained significantly higher in the WBC group at 60 and 120 min post CPB (0.98 +/- 0.19 and 1.13 +/- 0.32% vs. 0.07 +/- 0.25 and 0.04 +/- 0.08%). Global LV function was significantly higher in the ES MO group at 60 and 120 min post CPB (PRSW 103 +/- 6 and 94.7 +/- 4.6% of ba seline vs. 85.3 +/- 4.9 and 74.7 +/- 7.6% of baseline). However, regional L V function showed no significant difference between groups. Conclusions: Hi gh-dose beta-blockade during continuous coronary perfusion may allow the su rgeon to utilize the advantages of warm heart surgery, while avoiding the i nterstitial edema formation and temporary cardiac dysfunction associated wi th continuous warm blood cardioplegia. In high risk patients such as patien ts with unstable angina or after failed PTCA, high-dose beta-blockade may b e an applicable alternative to cardioplegic arrest. (C) 2000 Elsevier Scien ce B.V. All rights reserved.