Abstract
993 Heart surgery induces profound changes in myocardial metabolism. These are the combined effect of systemic activation and myocardial ischemia. Prominant features are restricted carbohydrate oxidation, and a high, energy inefficient FFA load. The purpose of this study was to investigate uptake and release of substrates (including amino acids) during implantation and reperfusion in clinical heart transplantation. A secondary issue was to evaluate effects of insulin (GIK) and amino acid infusion, since these agents attenuate metabolic derangment in conventional heart surgery. 22 patients were included in a controlled randomized prospective study. In 11 patients GIK (4 IU/kg × bw/hour insulin) and a balanced amino acid infusion (I+AA) was initiated at the start of implantation. Arterial and coronary sinus blood was analyzed for oxygen content, glucose, lactate, FFA and amino acids. During blood cardioplegia lactate was released in most of the patients (18/22, mean −0.52±0.12 μm/L), and there was no uptake of FFA, glucose or any amino acid. I+AA had no effects on myocardial substrates during cardioplegia. After 1 hour reperfusion lactate uptake was resumed in I+AA but not in control patients (0.40±0.11 vs 0.02±0.11 μm/L, p=0.034). In I+AA patients there was still no FFA uptake, while in control patients FFA uptake was significant (0.20±0.05 μm/L, p=0.003). There was still no uptake of glucose or amino acids in either group. It is concluded that substate metabolism is markedly abnormal in the human heart allograft during implantation and reperfusion. Infusion of insulin (GIK) and amino acids improves myocardial lactate metabolism and decreases FFA load.
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