The Effects of Isoflurane on Regional Myocardial Contractility and Metabolism in Stunned Myocardium in Acutely Instrumented Dogs

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Abstract
The sustained dysfunction of myocardial contractility after short periods of coronary artery occlusion and reperfusion is termed "stunned myocardium." Isoflurane may improve the recovery of regional myocardial contractility in stunned myocardium. The purpose of the present study was to determine the effects of isoflurane on 1) the restoration of regional myocardial contractility and 2) the high-energy phosphate metabolism in an acute canine model. To evaluate the effects of isoflurane on the recovery of regional myocardial contractility in stunned myocardium, the left anterior descending coronary artery (LAD) was occluded for 15 min and then reperfused for 60 min during isoflurane (1.5% end-tidal concentration) anesthesia. Regional myocardial contraction was evaluated by ultrasonic segment shortening (SegS), systolic shortening (SysS), and postsystolic shortening (PSS) measurements. High-energy phosphate metabolites were measured at 60 min after reperfusion in another group using full-thickness samples of myocardium obtained from the reperfused area (supplied by the LAD), and the nonischemic area (supplied by the left circumflex coronary artery). The concentrations of adenosine monophosphate (AMP), adenosine diphosphate (ADP), adenosine triphosphate (ATP), creatine phosphate (CP), and lactate in the endocardial portion of the myocardium were measured and the energy charge potential (ECP) was calculated. After 60 min of reperfusion percent SegS was 67.7% +/- 6.6% vs 23.9% +/- 9.4%, isoflurane and control, respectively; percent SysS was 67.4% +/- 6.3% isoflurane vs 29.3% +/- 7.4% control; and percent PSS was 10.5% +/- 4.6% isoflurane vs 40.5% +/- 8.8% control. ATP in the reperfused area decreased in both anesthetic groups but was higher in the isoflurane (88.2%) compared to the control group (77.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

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