Evaluation of myocardial perfusion using positron emission tomography in infants following a neonatal arterial switch operation

This study was performed to examine the use of positron emission tomography (PET) as a method of evaluating myocardial perfusion after the arterial sw itch operation for correction of transposition of the great arteries. Eleve n asymptomatic patients (median age 2.3 years, range 1.3-4.3 years) post su ccessful neonatal arterial switch repair for transposition underwent cardia c PET scanning using N-13 ammonia before and after dipyridamole infusion. R econstructed data from static scans were analyzed for regional perfusion de fects before and after pharmacological stress. Simultaneous assessment of c oronary flow before and after stress was performed using a Patlak graphical analysis of data from dynamic scans. Results obtained from PET scanning we re correlated with patterns of coronary artery anatomy, electrocardiogram ( ECG) recordings, and echocardiographic evaluation. PET scanning demonstrate d normal distribution of myocardial perfusion before and after stress in al l but one patient, who was found to have a discrete inferior transmural per fusion defect. The defect was well correlated with perioperative ECG change s and a complicated postoperative course. Myocardial blood flow before dipy ridamole (0.690 ml/min/g) was similar to reported adult rest values. There was a small but significant (p < 0.002) increase in myocardial blood flow a fter dipyridamole stress with a mean coronary flow reserve of 1.19 (+/-0.10 3). Echocardiographic evaluation failed to demonstrate significant wall mot ion abnormalities in any of the patients. Cardiac PET scanning is a reliabl e noninvasive method for evaluation of myocardial perfusion in small childr en. In this study, the incidence of myocardial perfusion defects after the arterial switch operation is lower than previously reported. The data obtai ned concerning coronary flow and coronary flow reserve after the arterial s witch need to be interpreted with caution because normal data in children a re not available.