Clinical VignetteQuestion 1 of 30
Sweaty Feeds
A 3-month-old girl is brought to the pediatric clinic because of a 4-week history of poor feeding and increased sweating during feeds. Her mother reports that she becomes tired quickly while bottle-feeding and takes 45 minutes to finish what she previously consumed in 15 minutes. She was born at 39 weeks' gestation with no complications and was healthy during the first month of life. She has gained only 400 g since her 2-month well-child visit. Her temperature is 37.0°C (98.6°F), pulse is 165/min, and respirations are 65/min. Pulse oximetry on room air shows an oxygen saturation of 98%. Physical examination shows a pink, well-perfused infant with mild subcostal retractions. A harsh holosystolic murmur is heard best at the left lower sternal border. The liver is palpable 3 cm below the right costal margin. The remainder of the examination shows no abnormalities.
Which of the following best explains the pathophysiology underlying this patient's clinical presentation?