Myocardial 18F-FDG-PET. Experiences with the euglycemic hyperinsulinemic clamp technique.

Myocardial positron emission tomography (PET) with 18F-Fluordeoxyglucose (FDG) is increasingly used for the detection of viable tissue in the infarcted myocardium. Previous studies show that the variable metabolic conditions determine the regional distribution of this tracer and that the inhomogeneities of uptake often observed even in the normal myocardium may relate to substrate availability. The authors tried to stimulate the myocardial FDG uptake by either the technically easier method of glucose loading or by the euglycemic hyperinsulinemic clamp (EHC) technique. In their hands both methods could be considered as equally practicable but differing in some important details in regard to both the study protocol (tracer dose, optimal scanning time) and the reproducibility of results. The EHC allows a quick stabilization of the metabolic environment and resulted in an earlier and markedly increased FDG uptake. However, the important standardization of the method was performed by a computer-controlled system only for the glucose and insulin infusions. Their experiences show that the EHC provides a useful framework for assessing altered cardiac metabolism and possibly describes changes after therapeutic interventions more precisely than the commonly used glucose-loading technique.