Congenital Heart Defects.
Eight out of every 1,000 infants have some type of structural heart abnormality at birth. Such abnormalities, known as congenital heart defects, may be so minor that they cause no symptoms or so severe that they're usually fatal. Congenital heart defects also vary widely in complexity, from a simple hole in the wall between two heart chambers to a complicated set of malformations, such as blood vessels in the wrong places and underdevelopment of one side of the heart.
A normal heart is divided into four hollow chambers, two on the right and two on the left. In performing its basic job — pumping blood throughout the body — the heart uses its left and right sides for different tasks. The right side moves blood into vessels called pulmonary arteries, leading to the lungs. In the lungs, oxygen enriches the blood, which circulates to the heart's left side in blood vessels called pulmonary veins. The left side of the heart pumps blood into a large vessel called the aorta. Branching off from the aorta are numerous other vessels that circulate blood to the rest of the body.
Several defects can be thought of as holes in the walls between heart chambers or abnormal passageways between major blood vessels leaving the heart. These holes allow oxygen-rich and oxygen-poor blood to mix.
If the holes are large and a lot of blood is mixed, the baby's skin or the area under the fingernails may be a slight bluish color. He or she may also develop signs and symptoms of congestive heart failure, such as shortness of breath, fatigue and leg swelling, because blood is flooding (overcirculating) the lungs.
The most common examples of hole defects include: ventricular septal defect, which is a hole in the wall between the right and left ventricles, and patent ductus arteriosus (DUK-tus ahr-teer-e-O-sus), an opening between the pulmonary artery and the aorta. During fetal development, this opening allows blood in the fetus to bypass the lungs. Within a few hours after birth, however, it should close. If it doesn't, oxygen-rich blood intended for the body is directed back to the lungs.
When vessels or valves become narrowed, the heart must work harder to move blood through them. Imagine trying to squeeze water out of a small hole in a balloon, rather than a large hole, and you'll get the idea.
Among the most common obstructive defects is pulmonary stenosis (stuh-NO-sis), a narrowing of the pulmonary valve, through which blood passes from the right ventricle to the pulmonary artery. Another obstructive defect, aortic stenosis, is a narrowing of the aortic valve, through which blood passes from the left ventricle into the aorta, eventually causing the heart muscle to thicken and the left ventricle to enlarge.
Several congenital heart defects involve incorrectly formed or positioned blood vessels going to and from the heart. For example, transposition of the great arteries occurs when the pulmonary artery and the aorta are on the wrong sides of the heart. This is a serious and immediately life-threatening defect.
Heart valve abnormalities. If the heart valves can't open and close correctly, blood can't flow smoothly. Examples includeEbstein's anomaly, in which the tricuspid valve is malformed and often leaks, and pulmonary atresia, in which a solid sheet of tissue forms in place of the pulmonary valve and blocks normal blood flow to the lungs. Both defects prevent oxygen-poor blood from circulating to the lungs.
1998-2005 Mayo Foundation for Medical Education and Research (MFMER)