Congenital means inborn or existing at birth. Among the terms you may hear are congenital heart defect, congenital heart disease and congenital cardiovascular disease. The word "defect" is more accurate than "disease." A congenital cardiovascular defect occurs when the heart or blood vessels near the heart don't develop normally before birth.

Congenital heart defects are rather uncommon. In most cases we don't know what causes them. Don't feel it's your fault for having a child with this problem. Rarely a viral infection may produce serious problems. For example, if a mother gets the German measles (rubella) while she's pregnant, this may interfere with the baby's heart as it develops, or it may cause other malformations. Other viral diseases also may cause defects before birth.

Heredity sometimes plays a role in congenital cardiovascular disease. More than one child in a family may have a congenital cardiovascular defect, but this rarely occurs. Certain conditions affecting multiple organs, such as Down's syndrome, can involve the heart, too. Some prescription drugs and over-the-counter medicines, as well as alcohol and "street" drugs, may increase the risk of having a baby with a heart defect. Other factors that affect the heart's development are under study.

Most heart defects either 1) obstruct blood flow in the heart or vessels near it or 2) cause blood to flow through the heart in an abnormal pattern. Rarely defects occur in which only one ventricle (single ventricle) is present, or both the pulmonary artery and aorta arise from the same ventricle (double outlet ventricle). A third rare defect occurs when the right or left side of the heart is incompletely formed hypoplastic heart. The different types of defects are discussed below.

Patent ductus arteriosus (P.D.A.)

This defect allows blood to mix between the pulmonary artery and the aorta. Before birth there's an open passageway (the ductus arteriosus) between these two blood vessels. Normally this closes within a few hours of birth. When this doesn't happen, some blood that should flow through the aorta and on to nourish the body returns to the lungs. A ductus that doesn't close is quite common in premature infants but rather rare in full-term babies. An obstruction is a narrowing that partly or completely blocks the flow of blood. Obstructions called stenoses can occur in heart valves, arteries or veins. The three most common forms of obstructed blood flow are pulmonary stenosis, aortic stenosis and coarctation of the aorta. Related but less common forms include bicuspid aortic valve, subaortic stenosis and Ebstein's anomaly.

-Pulmonary stenosis (P.S.) - The pulmonary or pulmonic valve is between the right ventricle and the pulmonary artery . It opens to allow blood to flow from the right ventricle to the lungs. A defective pulmonary valve that doesn't open properly is called stenotic . That means the right ventricle must pump harder than normal to overcome the obstruction. Aortic stenosis (A.S.) - The aortic valve, between the left ventricle and the aorta , is narrowed. This makes it hard for the heart to pump blood to the body. Aortic stenosis occurs when the aortic valve didn't form properly. A normal valve has three leaflets or cusps, but a stenotic valve may have only one cusp (unicuspid) or two cusps (bicuspid), which are thick and stiff. (See bicuspid aortic valve below.)

-Coarctation of the aorta ("Coarct") - The aorta is pinched or constricted. This obstructs blood flow to the lower part of the body and increases blood pressure above the constriction. Usually there are no symptoms at birth, but they can develop as early as the first week after birth. A baby may develop congestive heart failure or high blood pressure that requires early surgery. Otherwise, surgery usually can be delayed. A child with a severe coarctation should have surgery in early childhood. This prevents problems such as developing high blood pressure as an adult.

-Bicuspid aortic valve - The normal aortic valve has three flaps, or cusps, that open and close. A bicuspid valve has only two flaps, rather than three. There may be no symptoms in childhood, but by adulthood (often middle age or older) the valve can become stenotic (narrowed), making it harder for blood to pass through it, or regurgitant (allowing blood to leak backward through it). Treatment depends on how well the valve works.

-Subaortic stenosis - Stenosis means constriction or narrowing. Subaortic means below the aorta . Subaortic stenosis refers to a narrowing of the left ventricle just below the aortic valve, which blood passes through to go into the aorta. This stenosis limits the flow of blood out of the left ventricle. This condition may be congenital or may be due to a particular form of cardiomyopathy known as "idiopathic hypertrophic subaortic stenosis" (I.H.S.S.). Treatment depends on the cause and the severity of the narrowing. It can include drugs or surgery.

-Ebstein's anomaly is a congenital downward displacement of the tricuspid valve (located between the heart's upper and lower chambers on the right side) into the heart's right bottom chamber (or right ventricle) . It's usually associated with an atrial septal defect (see below).

Septal defects

Some congenital cardiovascular defects let blood flow between the heart's right and left chambers. This happens when a baby is born with an opening between the wall (septum) that separates the right and left sides of the heart. This defect is sometimes called "a hole in the heart." The two most common types of this defect are atrial septal defect and ventricular septal defect. Two variations are Eisenmenger's complex and atrioventricular canal defect.

-Atrial septal defect (A.S.D.) - An opening exists between the heart's two upper chambers. This lets some blood from the left atrium (blood that's already been to the lungs) return via the hole to the right atrium instead of flowing through the left ventricle , out the aorta and to the body. Many children with ASD have few, if any, symptoms. Closing the atrial defect by open-heart surgery in childhood can prevent serious problems later in life.

-Ventricular septal defect (V.S.D.) - An opening exists between the two lower chambers of the heart. Some blood that's returned from the lungs and been pumped into the left ventricle flows to the right ventricle through the hole instead of being pumped into the aorta. Because the heart has to pump extra blood and is overworked, it may may enlarge.

-Eisenmenger's complex is a ventricular septal defect coupled with pulmonary high blood pressure, the passage of blood from the right side of the heart to the left (right to left shunt), an enlarged right ventricle and a latent or clearly visible bluish discoloration of the skin called cyanosis . It may also include a malpositioned aorta that receives ejected blood from both the right and left ventricles (an overriding aorta).

-Atrioventricular (A-V) canal defect (also called endocardial cushion defect or atrioventricular septal defect) - A large hole in the center of the heart exists where the wall between the upper chambers joins the wall between the lower chambers. Also, the tricuspid and mitral valves that normally separate the heart's upper and lower chambers aren't formed as individual valves. Instead, a single large valve forms that crosses the defect.

-Transposition of the great arteries - The positions of the pulmonary artery and the aorta are reversed. The aorta is connected to the right ventricle , so most of the blood returning to the heart from the body is pumped back out without first going to the lungs. The pulmonary artery is connected to the left ventricle, so most of the blood returning from the lungs goes back to the lungs again.

-Pulmonary atresia - No pulmonary valve exists, so blood can't flow from the right ventricle into the pulmonary artery and on to the lungs. The right ventricle acts as a blind pouch that may stay small and not well developed. The tricuspid valve is often poorly developed, too.

-Truncus arteriosus - This is a complex malformation where only one artery arises from the heart and forms the aorta (a-OR'tah) and pulmonary artery . Surgery for this condition usually is required early in life. It includes closing a large ventricular septal defect within the heart, detaching the pulmonary arteries from the large common artery, and connecting the pulmonary arteries to the right ventricle with a tube graft. Children with truncus arteriosus need lifelong follow-up to see how well the heart is working.

Hypoplastic left heart syndrome

In hypoplastic left heart syndrome, the left side of the heart, including the aorta, aortic valve, left ventricle and mitral valve, is underdeveloped. Blood returning from the lungs must flow through an opening in the wall between the atria , called an atrial septal defect. The right ventricle pumps the blood into the pulmonary artery , and blood reaches the aorta through a patent ductus arteriosus (see above).