A 3-year-old boy is brought to the pediatrician for evaluation of developmental delay and frequent irritability. On examination, the child has a broad forehead, elfin-like facies, periorbital fullness, and an overly friendly personality. A harsh systolic ejection murmur is heard at the upper right sternal border. Blood pressure is notably higher in the upper extremities compared to the lower extremities. The physician suspects a genetic disorder. Which of the following is the most likely cause of cardiovascular complications in this patient?
