A flow of blood directly from the right atrium to left atrium is a dangerous complication of certain heart abnormalities. It can lead to cyanosis. What do you know about the flow of blood through the heart and lungs that would explain this? Yes, I do know what cyanosis means. I am having difficulty coming up with the correct words to address this.

The the right atrium lets blood flow to the right ventricle, which receives oxygen-poor blood. This blood goes to the lungs to get more oxygen. If the blood flows to the left atrium, the blood is not getting the oxygen it needs.