Patent Ductus Arteriosus Continuous Murmur

A 3-year-old girl born preterm at 32 weeks presents with poor weight gain, recurrent lower respiratory tract infections, and easy fatigability. On examination, she has a wide pulse pressure with bounding pulses, heart rate 118/min, respiratory rate 30/min, and a classic continuous "machinery" murmur heard best in the left infraclavicular area. Echocardiography confirms a moderate-sized shunt with left atrial and left ventricular dilatation. The structure marked **A** in the diagram represents the abnormal communication responsible for this clinical presentation. Which of the following best describes the hemodynamic consequence of the shunt through structure **A**?