Review Question - QID 214374

A 3-year-old girl is brought by her parents to the pediatrician. The family recently immigrated from the Dominican Republic, and the child has never received pediatric care in the past. The parents report that the child often complains of discomfort in her legs after walking for a short distance and seems to have shortness of breath with exertion. They note that the child fed poorly as an infant and has had persistently swollen hands and feet since birth. The child is at the 5th percentile for both height and weight. On physical exam, the child is noted to have nonpitting edema of the hands and feet bilaterally as well as cold lower extremities with faint femoral pulses. She also has excess folds of skin along the sides of her neck, low-set ears, and a lower posterior hairline. Which of the following mechanisms is most likely responsible for the patient's leg discomfort with walking?