History A 17-year-old white male adolescent was re-evaluated for a withheld cardiac condition initially detected during prenatal imaging at an outside institution. He had previously experienced intermittent episodes of shortness of breath, chest pain, and palpitations with exertion, but more recently he had been asymptomatic. He had no other comorbidities and no family history of congenital heart disease, cardiomyopathy, arrhythmia, or sudden cardiac death. At physical examination, the patient had a grade II/IV rumbling systolic murmur best heard at the left upper sternal border. Otherwise, cardiovascular and other physical examination findings were normal. An electrocardiogram showed sinus bradycardia and nonspecific T wave changes. A graded exercise stress test was normal. Cardiac MRI was performed without and with gadolinium-based contrast material. Multiple echocardiograms obtained since birth, cardiac MR images obtained 2 and 4 years earlier, and nongated CT images obtained with iodinated contrast material to evaluate trauma 8 years prior showed findings similar to those of the current examination. Prior chest radiographs (not shown) were normal, and angiography performed when the patient was 4 years old revealed normal coronary arteries.