The atria is referring to those two chambers of the heart, and a defect means it's an abnormality. So normally, it closes. But in this type of defect, we have some type of abnormality that causes this valve to actually remain open. And so we have the movement of blood between the two atrium of the heart. Now, normally this condition is actually not very dangerous because normally what happens is because we have a higher pressure on the left side of the heart, then on the right side of the heart, a tiny bit of that oxygenated blood inside the left atrium will go into the right atrium. And so we have some of that oxygenated blood reaching the right atrium, and it will basically return back to the lungs via the pulmonary trunk.