PLASMA FATTY-ACID LEVELS IN INFANTS AND ADULTS AFTER MYOCARDIAL-ISCHEMIA

High levels of fatty acids are detrimental during reperfusion of ische mic hearts in part because of an inhibition of myocardial glucose use. We therefore measured plasma fatty acids during and after myocardial ischemia in both adult and pediatric patients. In adult patients under going thrombolytic therapy after an acute myocardial infarction, plasm a fatty acids levels were elevated on admission to hospital (0.96 +/- 0.06 vs 0.40 +/- 0.01 mmol/L in healthy control subjects) and remained elevated throughout the initial 48 hours of hospitalization. In adult patients undergoing cardiac surgery, plasma fatty acids were markedly increased during surgery and at the time of the release of the aortic cross clamp(2.21 +/- 0.54 and 1.61 +/- 0.32 mmol/L, respectively). In children and infants (mean age 4.33 +/- 0.44 years) who had surgery t o correct congenital heart defects, fatty acid levels during surgery i ncreased to 3.27 +/- 0.26 mmol/L and remained elevated during immediat e reperfusion (1.91 +/- 0.15 mmol/L) and for 24 hours after surgery (1 .67 +/- 0.22 mmol/L). Because experimental studies have shown that hig h levels of fatty acids are detrimental to recovery of adult animal he arts, we determined the effect of high fatty acid levels on reperfusio n recovery of isolated working hearts from 1-day-old rabbits perfused with 0.4 mmol/L palmitate (normal fat) or 1.2 mmol/L palmitate (high f at) and subjected to 50 minutes of global ischemia followed by aerobic reperfusion. Rabbit hearts perfused with high fat showed significantl y decreased preischemic function (heart rate X change in pressure was 51.2% of normal-fat hearts) and postischemic function (heart rate X ch ange in pressure recovered to 34.4% of values seen in normal-fat heart s). Thus the reperfused myocardium after ischemia in adults, children, and infants is exposed to elevated levels of fatty acids. In keeping with experimental data from newborn rabbits and mature animal models, it is likely that pediatric myocardial function is compromised by expo sure to high fatty acid levels.