A 2-day-old male neonate born at term in Delhi presents with persistent cyanosis and poor feeding. On examination, the infant is tachypneic (RR 65/min) with mild hepatomegaly. Chest X-ray shows cardiomegaly with pulmonary congestion. Echocardiography reveals a large patent foramen ovale (PFO) with right-to-left shunting and elevated right atrial pressure. The attending pediatrician notes that the ductus venosus is still patent. Which of the following best explains the persistence of this right-to-left shunt through the PFO in this neonate?