Recovery of Contractile Function of Stunned Myocardium in Chronically Instrumented Dogs is Enhanced by Halothane or Isoflurane

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Abstract
Following breif periods (5-15 min) of total coronary artery occlusion and subsequent reperfusion, despite an absence of tissue necrosis, a decrement in contractile function of the postischemic myocardium may nevertheless be present for prolonged periods. This has been termed "stunned" myocardium to differentiate the condition from ischemic or infarction. Because the influence of volatile anesthetics on the recovery of postichemic, reperfused myocardium has yet to be studied, the purpose of this investigation was to compare the effects of halothane and isoflurane on systemic and regional hemodynamics following a brief coronary artery occlusion and reperfusion. Nine groups comprising 79 experiments were completed in 42 chronically instrumented dogs. In awake, unsedated dogs a 15-min coronary artery occlusion resulted in paradoxical systolic lengthening in the ischemic zone. Following reperfusion active systolic shortening slowly returned toward control levels but remained approximately 50% depresssed from control at 5 h. In contrast, dogs anesthetized with halothane or isoflurance (2% inspired concentration) demonstrated complete recovery of function 3-5 h following reperfusion. Because the anesthetics directly depressed contractile function, aditional experiments were conducted in which a 15-minute coronary artery occlusion was produced during volatile anesthesia; however, each animal was allowed to emerge from the anesthetized state at the onset of reperfusion. Similar results were obtained in these experiments, demonstrating total recovery of contractile function within 3-5 h following reperfusion. Thus, despite comparable degrees of contractile dysfunction coraonay artery occulsion in awake and anesthetized dogs, the present results demonstrate that halothane and isoflurane produce marked improvement in the recovery of segment function following a transient ishemic episode. Therefore, volatile anesthetics may attenuate postischemic left ventricular dysfunction occurring intraoperatively and enhance recovery of regional wall motion abnormalities during reperfusion.