Congenital Heart Disease Health Article

Definition

Congenital heart disease, or congenital heart defect, includes a variety of structural problems of the heart or its major blood vessels, which are present at birth.

Description

The heart, which is completely developed about eight weeks after conception, is one of the earliest organs to completely develop. Congenital heart defects occur when the heart or blood vessels near the heart do not develop properly before birth. Some infants are born with mild types of congenital heart defects, but most need surgery in order to survive. In some cases, the defect may be mild and unnoticed at birth, then diagnosed later in life.

Research is ongoing, and at least 35 congenital heart or cardiovascular defects have been identified. Each defect is defined by its location and severity. Most congenital cardiovascular defects obstruct the flow of blood in the heart or nearby blood vessels, or cause an abnormal flow of blood through the heart. Rarer congenital cardiovascular defects occur when the newborn has only one ventricle (lower chamber), when the pulmonary artery (leading to the lungs) and the aorta (the largest artery that brings blood to the body) come out of the same ventricle, or when one side of the heart is not completely formed.

Patent ductus arteriosus

Ductus arteriosus refers to an open passageway—or temporary blood vessel (ductus)—that carries blood from the heart via the pulmonary artery to the aorta before birth. This passageway allows blood to bypass the lungs, which are not yet functional in the fetus. The ductus should close spontaneously in the first few hours after birth. When it does not close in the newborn, some of the blood that should flow through the aorta returns to the lungs. Patent ductus arteriosus is common in premature babies, but rare in full-term babies. It has been associated with mothers who had German measles (rubella) while pregnant. Patent ductus arteriosus accounts for 6–11 percent of all cases of congenital cardiovascular defects in the United States.

Hypoplastic left heart syndrome

Although rare, hypoplastic left heart syndrome, a condition in which the left side of the heart is underdeveloped, is the most serious congenital cardiovascular defect. With this syndrome, blood returning from the lungs must flow through an opening or hole in the wall between the atria, called an atrial septal defect. The right ventricle pumps blood into the pulmonary artery and blood reaches the aorta through a patent ductus arteriosus (see description in the previous section). In hypoplastic left heart syndrome, the baby seems normal at birth, but as the ductus closes, blood cannot reach the aorta and circulation fails. If left untreated, hypoplastic left heart syndrome is always fatal.

Heart rhythm problems

An arrhythmia is an abnormal heart beat. Normally, the heart beats at 50–150 beats per minute, depending on the child's age. Bradycardia is an irregularly slow heart rhythm, and tachycardia is an irregularly fast heart rhythm. Both conditions reduce the heart's pumping ability.

Obstruction defects

When heart valves, arteries, or veins are narrowed, they partially or completely block the flow of blood. The most common obstruction defects are pulmonary valve stenosis, aortic valve stenosis, and coarctation of the aorta. Coarctation of the aorta accounts for 8–11 percent of all cases of congenital cardiovascular defects in the United States.

Stenosis is a narrowing of the valves or arteries. In pulmonary stenosis, the pulmonary valve does not open properly, forcing the right ventricle to work harder. In aortic stenosis, the improperly formed aortic valve is narrowed. As the left ventricle works harder to pump blood through the body, it becomes enlarged. In coarctation of the aorta, the aorta is constricted, reducing the flow of blood to the lower part of the body and increasing blood pressure in the upper body.

Bicuspid aortic valve and subaortic stenosis are less common obstruction defects. A bicuspid aortic valve has only two flaps instead of three, which can lead to stenosis in adulthood. Subaortic stenosis is a narrowing of the left ventricle below the aortic valve that limits the flow of blood from the left ventricle.