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Myocardial protection with high-dose beta-blockade in acute myocardial ischemia
H J Geissler1, K L Davis, G A Laine
1Department of Anesthesiology, University of Texas-Houston Medical School, 77030, USA.
Insights
High-dose beta-blockade with esmolol during continuous coronary perfusion effectively preserved global left ventricular function and reduced myocardial edema compared to warm blood cardioplegia in a canine model of acute ischemia. This suggests a potential alternative for high-risk cardiac surgery patients.
Area of Science:
- Cardiology
- Cardiac Surgery
- Cardiovascular Physiology
Background:
- Emergency coronary artery bypass grafting (CABG) in acute myocardial ischemia increases the risk of postoperative cardiac dysfunction.
- High-dose beta-blockade during continuous coronary perfusion is explored as an alternative to conventional cardioplegia for high-risk CABG patients.
Purpose of the Study:
- To compare the efficacy of high-dose beta-blockade with esmolol versus continuous warm blood cardioplegia.
- To evaluate their effects on left ventricular (LV) ischemia and reperfusion in a clinically relevant model.
Main Methods:
- Twelve dogs underwent 60 minutes of regional LV ischemia induced by LAD ligation.
- Cardiopulmonary bypass and aortic crossclamp were initiated; treatments included high-dose beta-blockade (ESMO, n=6) or warm blood cardioplegia (WBC, n=6) for 60 minutes.
- Myocardial water content, global LV function (PRSW), and regional LV function (wall motion score) were assessed.
Main Results:
- The WBC group exhibited significantly higher interstitial edema formation during aortic crossclamp (2.2% vs. 0.76%).
- Myocardial water gain remained significantly higher in the WBC group post-CPB (0.98-1.13% vs. 0.04-0.07%).
- Global LV function (PRSW) was significantly better preserved in the ESMO group post-CPB (94.7-103% vs. 74.7-85.3% of baseline).
Conclusions:
- High-dose beta-blockade with esmolol during continuous perfusion may offer advantages of warm heart surgery without the edema and dysfunction associated with warm blood cardioplegia.
- This approach could be a viable alternative for high-risk patients undergoing CABG, including those with unstable angina or failed PTCA.
Objective:
The risk of postoperative cardiac dysfunction is markedly increased by emergency coronary artery bypass grafting in the presence of acute myocardial ischemia. High dose beta-blockade during continuous coronary perfusion has been suggested as an alternative to conventional cardioplegia and this technique has been applied successfully in high risk patients for coronary artery bypass grafting (CABG) surgery. This study compared high dose beta-blockade with esmolol to continuous warm blood cardioplegia in a clinically oriented model of acute left ventricular (LV) ischemia and reperfusion.
Methods:
Twelve dogs were subjected to 60 min of regional LV ischemia by left anterior descending branch (LAD) ligation. Cardiopulmonary bypass (CPB) 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 maintained for 60 min. Myocardial water content (measured from endomyocardial biopsies using a microgravimetric technique), global LV function (preload recruitable stroke work: PRSW), and regional LV function (echocardiographic wall motion score) were determined at baseline and after weaning from CPB.
Results:
During aortic crossclamp interstitial edema formation was significantly higher in the WBC group with an average water gain of 2.2 +/- 0.49 vs. 0.76 +/- 0.12% in the ESMO group. Thereafter, edema resolved in both groups, but 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 ESMO group at 60 and 120 min post CPB (PRSW 103 +/- 6 and 94.7 +/- 4.6% of baseline vs. 85.3 +/- 4.9 and 74.7 +/- 7.6% of baseline). However, regional LV function showed no significant difference between groups.
Conclusions:
High-dose beta-blockade during continuous coronary perfusion may allow the surgeon to utilize the advantages of warm heart surgery, while avoiding the interstitial edema formation and temporary cardiac dysfunction associated with continuous warm blood cardioplegia. In high risk patients such as patients with unstable angina or after failed PTCA, high-dose beta-blockade may be an applicable alternative to cardioplegic arrest.