OBJECTIVES: The aim of the study was to assess regional glucose metabolism and contractile function by gated positron emission tomography using fluoro-18-deoxyglucose (FDG-PET) in pediatric patients after the arterial switch operation and suspected myocardial infarction. BACKGROUND: Morbidity and mortality after the arterial switch operation for transposition of the great arteries are often related to impaired coronary function. Justification of high-risk revascularization procedure in infancy requires thorough evaluation of myocardial viability. Although PET is state-of-the-art for evaluation of myocardial viability in adults there are no reports on its impact and feasibility in infants and children. METHODS: We applied electrocardiogram-triggered FDG-PET for assessment of metabolic and functional status of the myocardium in seven infants and seven children. Glucose metabolism, wall motion and wall thickening were evaluated visually and quantitatively on the basis of parametric 3-D images. Additionally, single-photon emission computed tomography perfusion scan was performed in six children. RESULTS: In two of seven infants, FDG-PET demonstrated viable myocardium in akinetic or hypokinetic regions corresponding to a coronary artery stenosis or occlusion. Therefore, indication for revascularization was derived from this finding. In six of the seven children, impaired glucose uptake reflecting myocardial scarring was present. Two patients had pathological findings on coronary angiography and signs of ischemia but were not suitable for revascularization. CONCLUSIONS: Myocardial viability and contractile function can be assessed simultaneously by gated FDG-PET even in infant hearts. This method contributes pertinent information to guide further therapy after the arterial switch operation and suspected myocardial infarction.