 So, let's discuss some general principles on how to approach a question about congenital heart defects. So, if you're reading a question stem, what's going to make you think that a patient might have congenital heart defect? Some things to look out for. Failure to thrive. This is a really important symptom. The question writers love to use this phrase, failure to thrive in poor feeding and conjunction with congenital heart defects. Cyanosis as well. This is a very classic symptom of certain types of congenital heart defects. You can see an example over here on the right of cyanosis. That's when the patient turns blue because they're not able to oxygenate their blood properly. Dyspnea or shortness of breath, that goes along with cyanosis and poor oxygenation. And if you have a question about a child that has congestive heart failure, you might want to consider that it could have been caused by congenital heart defect that should be on the differential. And how do you work up these patients? An echocardiogram is really going to be the gold standard. Again, these are structural heart problems, so you want a test that can let us look at the heart. And then how about treatment? So if you ever get a question about treatment of congenital heart defects, one question I always want you to ask yourself is, is the patient symptomatic and are they cyanotic? If the answer to either of these questions is yes, they're trying to get you to think of surgery as a potential answer. Now, before we can discuss some examples of congenital heart defects, we need to clarify the difference between cyanotic and asynotic disease. So we have an example of a normal heart over here on the right. If we imagine a situation in which you have a shunt that causes blood to flow from the right side to the left side of the heart, it'll bypass the lung. So we know that blood is not flowing through the lungs to be oxygenated. Instead, we have deoxygenated blood flowing from the right side to the left side and then deoxygenated blood flowing out into systemic circulation. And this deoxygenated blood in the systemic circulation will cause the symptom of cyanosis very early in the disease process. So these right to left shunts, we call those cyanotic because they present with newborn cyanosis. Now, if we imagine another heart defect in which blood now flows from the left side to the right side through a shunt, it still has the opportunity to flow through the pulmonary artery into pulmonary circulation to get oxygenated. So we'll still have oxygenated blood flowing out into systemic circulation. It's just that we lose a little bit of oxygenated blood from left to right with each beat of the heart, so things are less efficient. But since these defects don't cause cyanosis, when the patient's a newborn, we call these asynotic defects, so these left to right shunts. And if they do present with cyanosis, it's usually when the child is a little bit older.