Cardioplegic arrest superimposed on evolving myocardial ischemia. Improved recovery after inhibition of hydroxyl radical generation by peroxidase or deferoxamine. A 31P nuclear resonance study.

Superimposition of cardioplegic arrest on acute low-cardiac-output states, as may occur after failure of percutaneous transluminal coronary angioplasty requiring emergency surgery, is associated with an increased operative risk. This increased risk is possibly attributable to reperfusion, which, after sequential episodes of myocardial ischemia, exacerbates tissue injury mediated by oxygen free radicals. One of the most cytotoxic of these active oxygen species is the hydroxyl radical, which is formed from superoxide anion and hydrogen peroxide through an iron-catalyzed reaction. This study assesses the effects of peroxidase, a hydrogen-peroxide scavenger, and of deferoxamine, an iron chelator, in isolated working rat hearts subjected to 30 minutes of low-flow ischemia (75% reduction in coronary flow) followed by 2 hours of cardioplegic arrest at 15 degrees C and by 30 minutes of normothermic reperfusion. Three groups of hearts (n = 7) were studied. Two groups were pretreated with either peroxidase (10,000 units/l) or deferoxamine (0.03 mM) during the last 15 minutes of the low-flow ischemic period. The third group received no prearrest intervention and served as a control group. In addition to hemodynamic determination, high-energy phosphate content [adenosine 5'-triphosphate (ATP)] and intracellular pH were monitored serially by 31P nuclear magnetic resonance spectroscopy. The two pretreated groups had better recovery of ATP levels and aortic flow values than did the control group.(ABSTRACT TRUNCATED AT 250 WORDS)