CD-ROM Today (UK) (Spanish) 15/CDRT.iso/dp/0350/03506.txt

Text File | 1994-01-18 | 9.1 KB | 198 lines

$Unique_ID{BRK03506}
$Pretitle{}
$Title{Atrial Septal Defects}
$Subject{Atrial Septal Defects Atrioseptal Defects Ostium Primum Defect
endocardial cushion defects Ostium Secundum Defect Sinus Venosus}
$Volume{}
$Log{}

Copyright (C) 1986 National Organization for Rare Disorders, Inc.

138:
Atrial Septal Defects

** IMPORTANT **
It is possible that the main title of the article (Atrial Septal Defects)
is not the name you expected.  Please check the SYNONYM listing to find the
alternate names and disorder subdivisions covered by this article.

Synonyms

     Atrioseptal Defects

DISORDER SUBDIVISION:

     Ostium Primum Defect; such defects belong to the "endocardial cushion"
defects, and may sometimes be known as such
     Ostium Secundum Defect
     Sinus Venosus

General Discussion

** REMINDER **
The information contained in the Rare Disease Database is provided for
educational purposes only.  It should not be used for diagnostic or treatment
purposes.  If you wish to obtain more information about this disorder, please
contact your personal physician and/or the agencies listed in the "Resources"
section.


Atrial septal defects are a relatively common form of congenital heart
disease.  The septum separating the two atria is incompletely formed before
birth and the opening persists.  This can result in inefficient distribution
of oxygen to the various tissues of the body, heart failure characterized by
edema, difficulty breathing, fatigue, and other cardiovascular disturbances.
Symptoms tend to be mild at first, so that the defect is sometimes not
recognized until adulthood, when various cardiorespiratory problems and heart
failure begin to develop.  Atrial defects can take several forms, with
different clinical consequences.

Many symptoms are shared by several different kinds of congenital heart
defects.  To determine the exact anatomic abnormality, physicians rely on the
patterns and quality of the sounds of the beating heart, electrocardiographic
(EKG) and echocardiographic findings, and information from cardiac
catheterization.  The heart sounds and EKG are the most commonly performed
investigations and may be characteristic.

Symptoms

A short discussion of the structure and function of the normal heart follows.
The human heart has four chambers, two atria and two ventricles.
Deoxygenated blood enters the right atrium from the systemic veins (i.e., the
veins draining all the body organs and tissues except the lungs).  It is
pumped from the right atrium to the right ventricle, and from the right
ventricle to the pulmonary artery.  The pulmonary artery carries the blood to
the lungs, where it is saturated with oxygen.  From the lungs, the blood
passes through the pulmonary veins to the left atrium, and thence into the
left ventricle, the most muscular of the four chambers of the heart.  The
contraction of the left ventricle forces the blood back into the systemic
circulation, where it supplies oxygen to the various body tissues.  Blood
then collects in veins, which eventually come together and drain again into
the right atrium.  The two atria are separated from each other by a
relatively thin membrane, known as the atrial septum.  The ventricular septum
separates the right and the left ventricles.

In atrial septal defects, this thin membrane separating the atria is
incomplete.  In ostium primum defects, the membrane at the lower part of the
septum has failed to develop normally; often the valves separating the atrium
from the ventricle on each side [tricuspid (right side) and bicuspid or
mitral (left side) valves] are also malformed, and even the apex of the
ventricular septum may be missing.  Ostium primum defects are often
associated with Down's Syndrome and are a relatively severe form of septal
defect.  The most common atrial septal defect is known as the ostium secundum
defect.  Here, the middle part of the atrial septum (region of foramen ovale)
fails to close during development of the fetus.  This condition superficially
appears similar to what is known as patent foramen ovale, but develops
differently, and has a different course.  (The foramen ovale is a hole in the
atrial septum covered by a flap of tissue; it allows blood to flow in one
direction between the two atria during the fetal stage, when the circulation
bypasses the lungs.  Normally, it closes shortly after birth, but in some
cases it remains anatomically, though not functionally, open.)

A third form of atrial septal defect, known as sinus venosus, occurs high
in the septum and is often associated with anomalous entry of the pulmonary
veins or vena cava (from the systemic circulation) in to the right and left
atria respectively.

Septal defects allow deoxygenated blood from the right atrium to mix with
freshly oxygenated blood from the left atrium.  This decreases the overall
oxygen saturation of the blood that is pumped into the systemic circulation.

Many children with atrial septal defects do not have symptoms.  Some have
mild growth retardation, and there seems to be an unusual susceptibility to
respiratory infections.  However, by about 40 years of age, or even earlier
at high altitudes where there is more stress on the cardiorespiratory system,
patients may begin to have difficulties.  This is because hypertension (high
blood pressure) gradually develops in the pulmonary circulation, changing the
direction in which the blood is shunted through the opening in the atrial
septum.

Right to left shunts have several clinical consequences, including
cyanosis (bluish complexion) due to poor oxygen saturation of the blood and
tissues, clubbing of the finger tips, and polycythemia, or an increase in the
number of red blood cells.  This condition also predisposes its victims to
brain abscesses.  In severe cases, the tissues may receive less than adequate
amounts of oxygen.  Eventually, there may be heart failure, with edema and
breathlessness.  Death may result without surgical repair of this defect.
Another later manifestation of atrial septal defects is disturbance of the
rhythm of atrial contractions (arrhythmias, including atrial fibrillation).

Heart defects seem to predispose the patient to bacterial infection of
the inner lining of the heart (bacterial endocarditis).  The resulting damage
can aggregate the patient's condition.

Causes

The causes of the arrest in embryonic development resulting in congenital
heart disease are poorly understood.  Only about 10% of the cases appear to
be hereditary.  Maternal rubella (measles), alcoholism, or diabetes are
associated with heart defects.  Ostium primum defects often occur in
individuals with Down's syndrome, and certain other chromosomal
abnormalities.

Affected Population

About one percent of live births have some kind of congenital heart defect;
of these, about ten percent have atrial septal defects.  Males are affected
more often than females.

Related Disorders

Other congenital heart defects include ventricular septal defects, valve
defects of various kinds, malformations of the large vessels entering and
leaving the heart, and anomalous positions of the heart in the chest.

Therapies:  Standard

The definitive treatment for atrial septal defects is surgical.  The hole in
the septum is either sutured shut, or patched with a graft.  The success rate
is quite high.  In ostim primum (endocardial cushion) defects, the
atrioventricular valves may have to be repaired or replaced; the success rate
is substantially lower in these more complex operations.  Surgery is usually
most successful in patients between the ages of 3 and 6 years.

Presurgical, palliative, treatment includes medication such as digitalis
to treat arrhythmias, excessively rapid heart beat, and heart failure.
Sodium restriction, diuretics, and rest are also effective in treating
congestive heart failure.  Respiratory infections are treated vigorously, and
antibiotics are given prophylactically with such procedures as tooth
extractions to reduce the risk of developing bacterial endocarditis.

Therapies:  Investigational

This disease entry is based upon medical information available through March
1987.  Since NORD's resources are limited, it is not possible to keep every
entry in the Rare Disease Database completely current and accurate.  Please
check with the agencies listed in the Resources section for the most current
information about this disorder.

Resources

For more information on Atrial Septal Defects, please contact:

     National Organization for Rare Disorders (NORD)
     P.O. Box 8923
     New Fairfield, CT  06812-1783
     [phone]

     American Heart Association
     7320 Greenville Ave.
     Dallas, TX 75231
     [phone]

     NIH/National Heart, Lung and Blood Institute
     9000 Rockville Pike
     Bethesda, MD  20892
     [phone]

     American Lung Association
     1740 Broadway
     New York, NY 10019
     [phone]

References

Petersdorf, Robert G., et al, editors, Harrison's Principles of Internal
Medicine, tenth edition.  New York:  McGraw-Hill 1983, pp. 1383-96.