abnormalities of the skeletal, urinary, and gas-
trointestinal systems, forming a collection that
doctors refer to by the acronym VACTERL: vertebral,
anorectal, cardiac, tracheoesophageal, renal, and
limb. About 50 percent of infants born with one
congenital anomaly among this grouping have at
least one other. Researchers believe about 10 per-
cent of congenital heart malformations result from
GENE MUTATIONor CHROMOSOMEabnormalities.
Common forms of congenital heart disease The
most common and most easily treatable congenital
heart malformations are patent ductus arteriosus
(PDA) and septal defects. The ductus arteriosus is
an opening between the AORTAand the pulmonary
ARTERYin the FETUSthat allows fetal circulation to
bypass the nonfunctioning LUNGS(the fetus draws
oxygen from the mother’s blood supply). At birth
a sequence of events takes place, initiated with the
pressure changes that occur with the infant’s first
breath, that cause the ductus arteriosus to close.
In some infants, especially those born prema-
turely, the closure does not take place and the
ductus arteriosus remains patent, or open. PDA
allows oxygenated and deoxygenated blood to
mix in the pulmonary artery, with the result that
the blood the aorta sends to the body carries only
partial oxygenation.
In a septal defect there is an abnormal opening
in the septum, or wall, separating the heart’s
chambers. A septal defect allows blood to move
directly between the involved chambers, which
disturbs the flow of blood and can result in blood
turbulence and pooling as well as reduced OXY-
GENATION. The most common presentation is atrial
septal defect (ASD), in which the opening is
between the right and left atria. The opening may
be the result of incomplete closure of the foramen
ovale, a natural opening between the atria in the
fetus that normally closes within 48 hours of
birth. ASD may also occur as a malformation of
the atrial septum. A ventricular septal defect
(VSD) is a malformation of the ventricular septum
and results in an opening between the right and
left ventricles. A VSD allows oxygenated and
deoxygenated blood to mingle, reducing the oxy-
gen content of the blood the left ventricle pumps
out to the body.
Atrioventricular (AV) canal defect is a more
extensive malformation of the septum in which
the atrial septum, the ventricular septum, or the
entire septum is missing. The heart becomes
essentially a single large chamber with oxygenated
and deoxygenated blood mixing freely. Blood
going to the body carries insufficient oxygen, and
blood going to the lungs is under much higher
pressure than the lungs can accommodate. AV
canal defect requires surgical repair within the
first few months of the infant’s life. Though AV
canal defect can occur as an isolated malformation
it most often occurs in conjunction with Down
syndrome, affecting about 25 percent of Down
syndrome infants.
Other common congenital heart defects include
coarctation of the AORTA(narrowing and irregular-
ities) and malformations of the heart valves such
as AORTIC STENOSIS, bicuspid aortic valve, tricuspid
atresia, and pulmonary atresia.
Grave malformations of the heart A number of
heart malformations are rare, complex, and life-
threatening. Their defects are severe and include
alterations of the heart’s structure that cannot sus-
tain life. They require immediate surgery for sur-
vival and usually follow-up operations for further
reconstruction. In some cases the only viable long-38 The Cardiovascular System
FORMS OF CONGENITAL HEART DISEASEanomalous pulmonary venous return aortic coarctation
AORTIC STENOSIS atrial septal defect (ASD)
atrioventricular (AV) canal defect bicuspid aortic valve
Eisenmenger’s complex hypoplastic left heart syndrome (HLHS)
LONG QT SYNDROME(LQTS) patent ductus arteriosus (PDA)
persistent truncus arteriosus pulmonary atresia
tetralogy of Fallot transposition of the great arteries (TPA)
tricuspid atresia ventricular septal defect (VSD)