Myocardial [18F]Fluorodeoxyglucose Uptake After Heterotopic Cardiac Transplantation Assessed by Positron Emission Tomography
Metabolic aspects, perfusion autoregulation, and receptor-mediated cardiac responses of the orthotopic cardiac transplant have gained increasing attention in the past few years. We recently assessed glucose uptake in vivo in orthotopic heart transplant recipients.1 Enhanced myocardial uptake as demonstrated by [18F]2-fluoro-2-deoxyglucose (18FDG) and PET scanning was explained by inefficient metabolic utilization of glucose by the transplanted myocardium or by the influence of circulating catecholamines, which may stimulate glucose uptake independently of cardiac workload. We also studied a 48-year-old male patient 6 months after heterotopic heart transplantation. Glucose uptake was assessed by use of 18FDG and PET imaging, with the basic premise that this parameter gives direct evidence of glucose metabolic state and myocardial viability in both cardiac allograft and the native poorly contracting heart, which was left in situ. Regional 18FDG uptake (mL · s−1 · g−1) was defined as the ratio of the average 18FDG pixel counts in the various tissue regions of the left ventricle to the integral of the arterial input function, as previously described.1 Regional 18FDG uptake was on average 285% higher in the transplanted heart than in the native heart (Figure⇓). This stems largely from the difference in myocardial tissue viability, as well as probably reflecting functional-metabolic coupling of the transplanted heart as opposed to the native heart.
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