A congenital heart defect, or congenital heart disease, is any abnormality of the heart that is present from the time of birth. These conditions are fairly rare and in nearly all cases you would know if your baby is going to have the condition, even before the baby is born, because the conditions can be detected with ultrasonography (ultrasound) while the mother is still pregnant. Congenital heart disease typically is grouped into two main categories. One category, called acyanotic congenital heart disease consists of abnormalities in which the baby does not demonstrate cyanosis, a situation when the skin, lips, and nailbeds take on a bluish coloration.
The other category is cyanotic congenital heart disease, meaning that the baby does show the bluish coloring, which could be all the time or the cyanosis can wax and wane. So far on the Pulse, we have discussed two examples of cyanotic congenital heart disease: transposition of the great arteries and tetralogy of Fallot. We’ll be discussing more examples both cyanotic and acyanotic congenital heart disease in the weeks and months to come.
In cyanosis, the blue color is due to the presence of high quantities of hemoglobin that is not carrying oxygen (called deoxyhemoglobin) in red blood cells passing through capillaries of the skin and mucous membranes. This, in turn, results from oxygen-depleted blood that has returned to the heart finding its way into the systemic arteries without first flowing through the lungs to pick up more oxygen (O2) and eliminate carbon dioxide (O2). When blood bypasses the lungs in such a way, it’s called a cyanotic shunt and also a right-to-left shunt, since blood moves from the right side of the heart directly to either the left side of the heart, or to a big artery, such as the aorta, that receives blood from the left side of the heart. In contrast, many types of acyanotic congenital heart disease features blood moving from the left side of the circulation to the right side (the right side of the heart or the pulmonary artery), so that’s called a left-to-right shunt. Since the blood that shunts has been through the lungs, the shunting to the right side of the circulation does not cause cyanosis, but it does cause other problems, since the lungs end up getting more blood flow than they are supposed to get. In severe cases, the rising pressure and volume of blood in the pulmonary blood vessels causes the vessels to narrow and harden, elevating the pressure so much that that blood pressure rises very high on the right side of the heart, causing the shunting to reverse from a left-to-right shunt to a right-to-left shunt, which will produce cyanosis. This is called Eisenmenger syndrome.
In all the beautiful pictures and animations, you will see red representing oxygenated blood, namely blood coming from the lungs through the pulmonary veins, blood coming from the placenta through the umbilical vein, and blood in the left side of the heart and the aorta, subsequent to birth. You will see blue in pictures to represent deoxygenated blood —blood traveling in the superior and inferior vena cava, moving through the right atrium, right ventricle, and pulmonary artery— also after birth, once the shunts have closed, when everything is normal. Finally, you will see purple in the drawings to represent blood with some intermediate level of oxygenation, because of mixing of blood that has traveled through the lungs with blood that has not traveled through the lungs. This purple blood will becomes very important as we explore congenital heart disease, especially the cyanotic category, because that’s when there is a lot of mixing. Often in such cases, the mixing, causing such purple blood is the only reason why the baby is getting any oxygen at all into its oxygen-starved body tissues. If the newborn is cyanotic, but alive, there’s some kind of mixing happening somewhere. But typically, if nothing is done after birth —and sometimes before birth— it will be fatal in cases of cyanotic congenital heart disease. There is typically a lot more time to identify acyanotic congenital heart disease.
Overall, congenital heart disease strikes about 1 in each 3,000 births, and as noted above, generally it can be detected on ultrasound during pregnancy, so doctors can be prepared for it and so can the parents. With cyanotic disease, generally, the cyanosis would start after the child starts to breathe —sometimes almost immediately after, but often after a period of time— and in most cases there’s a simple thing that doctors can do during pregnancy, prior to delivery. Administer a medicine called prostaglandin E1 to keep the ductus arteriosus open. That’s a blood vessel that connects the aorta with the pulmonary artery during fetal life. Normally, the ductus arteriosus closes within a couple of days after birth, but by forcing it to stay open, doctors can keep blood from the two sides of the heart mixing when that’s the better situation for a newborn with congenital heart disease.
