A 2-month-old girl is brought to the physician because of poor feeding, sweating during feeding and bluish discoloration of the lips when crying. She is below the 5th percentile for both height and weight. Cardiac examination shows a right parasternal heave. A grade 3/6 systolic ejection murmur is heard over the left second intercostal space. During the examination, the infant begins crying and becomes cyanotic; during this time, the murmur is noted to be barely audible. Which of the following is the most likely diagnosis?