Baby A is a two-year-old girl, slightly small for her age. Her mother reports that she has had three respiratory infections in the past six months and seems unable to run around without becoming out of breath. When you examine Baby A, you detect sounds of fluid in her lungs. Palpation indicates enlarged right ventricle and pulmonary arteries. Baby A’s blood pressure is low for her size. The doctor orders BNP levels and an echocardiogram to test for atrial septal defect, or a hole connecting the left and right atria. Baby A's mother is very upset by this idea. She wants to know what could have made a hole in her daughter's heart, and why the doctor is not searching for the infection that caused it. She has asked you to explain it to her. To start, review the path blood takes through the body and lungs.
In Baby A, the atrial septal defect did not close at birth. Blood is flowing through her defect in what direction?