Variability of the Lumped Constant for [ 18 F]2-Deoxy-2-fluoroglucose and the Experimental Isolated Rat Heart Model: Clinical Perspectives for the Measurement of Myocardial Tissue Viability in Humans

Abstract

To the Editor: The recent publication of findings on the utilization rate for glucose (MRglu) in the ischemic and reperfused isolated rat heart1 concludes that the lumped constant (LC) for [18F]2-deoxy-2-fluoroglucose (FDG) is variable under conditions in which free fatty acids (FFAs) are the main metabolic substrate. The article thus signals a cautionary message to those workers using FDG in the fasted state. However, what is not stated in the take-home message is the important finding that the LC is unaffected by ischemia and reperfusion when circulating FFAs are low. The authors assert that the coadministration of glucose and FFAs results in a far more physiological condition than glucose alone, and thus they pay scant attention to the equally physiological condition in which insulin levels are increased and FFA concentrations greatly diminished. This is unfortunate, …