Review Question - QID 108870

A seven-month-old male is brought to the pediatrician by his mother because she is concerned that the child’s lips occasionally turn blue when he cries. His temperature is 99.2°F (37.3°C), blood pressure is 90/50 mmHg, pulse is 160/min, and respirations are 24/min. On examination, a harsh systolic ejection murmur is heard at the left upper sternal border. A chest radiograph of the infant is shown in Figure A. Which of the following processes most likely contributed to this patient’s condition?