Esmolol and cardiopulmonary bypass during reperfusion reduce myocardial infarct size in dogs.
BACKGROUND
Infarct size can be reduced by beta-blockade in acute myocardial ischemia. However it is unknown whether myocardial salvage is still effective when beta-blockade is limited to reperfusion.


METHODS
After initiation of cardiopulmonary bypass, 20 dogs were submitted to 2 hours of regional left ventricular ischemia, followed by 2 hours of reperfusion. In 11 dogs beta-blockade was started with the onset of reperfusion (esmolol group). The remaining dogs received no treatment (control, n = 9). Infarct size was determined by tetrazolium chloride staining. Myocardial water content (MWC) and ultrastructural damage (electronmicroscopy) were determined from transmural biopsies.


RESULTS
Infarct size was significantly smaller in the esmolol group compared with control (49% versus 68%, p < 0.05). After 2 hours ischemia there was no difference in MWC between groups, whereas after 2 hours reperfusion MWC of ischemic myocardium was significantly lower in the esmolol group than in the control (p < 0.05). Ultrastructural changes were typical for ischemia-reperfusion injury in both groups.


CONCLUSIONS
Beta-blockade may be cardioprotective during reperfusion through various mechanisms and may enhance myocardial salvage, even when treatment is initiated as late as with the onset of reperfusion.
Geissler
H J
HJ
Department of Anesthesiology, University of Texas-Houston Medical School, USA. hans.geissler@medizin.uni-koeln.de
Davis
K L
KL
Buja
L M
LM
Laine
G A
GA
Brennan
M L
ML
Mehlhorn
U
U
Allen
S J
SJ
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001706:Biopsy; D002315:Cardiopulmonary Bypass; D004285:Dogs; D005260:Female; D008297:Male; D008854:Microscopy, Electron; D009203:Myocardial Infarction / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000473:pathology*; D009206:Myocardium / Q000473:pathology; D011412:Propanolamines / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; C036604:esmolol