What is an atrial septal defect ?
Atrial septal
defect (ASD) is a hole in the wall (the septum) between the
heart's two uppermost chambers, the right atrium and the left
atrium. This hole allows blood to flow in either direction between
the left and right atrium.
An ASD may cause several problems. First, it creates a condition
in which the right side of the heart now contains extra blood, and
extra blood also now flows to the lungs. This diversion of blood
puts strain on the heart because it has to pump this extra blood to
the lungs. This extra blood flow to the lungs may damage the
arteries to the lungs over time, leading to high blood pressure in
these vessels. In addition, the strain put on the right-sided
pumping chamber can lead to a weakening or enlargement of the right
side of the heart and eventually heart failure, if left untreated.
This enlargement may also cause arrhythmias (irregular heart
rhythms) to develop. Also, ASDs in some circumstances can allow
blood clots from the body to enter the brain and cause a
stroke.
What are the symptoms of an ASD?
Most patients do
not have any symptoms in childhood. However, symptoms that might
develop over time, depending on the severity of the ASD and other
factors, include:
- shortness of breath, fatigue, and labored breathing while
exercising
- irregular heart beats
- transient ischemic attacks (TIA), which result in stroke-like
symptoms
- stroke
- pulmonary hypertension (high blood pressure in the arteries of
the lung; can lead to heart failure if not treated)
- reduction in lifespan of about 20 years on average if the ASD
is not closed
What causes ASD?
An ASD is congenital, meaning it
is a defect that is inborn or exists at birth. Stated another way,
the defect is an abnormality, not a disease. The septum between the
two atria of the heart did not develop normally before birth. What
is known is that about 20 percent of ASDs that occur in
infants close on their own in the first years of life.
Heart defects in general
Sometimes a viral
infection can cause heart defects to develop. Other causes include
genetic factors, certain other medical conditions (Down's
syndrome, for example), and some prescription and nonprescription
drugs; however, in about 95% of the cases, no cause can be
identified.
How is an ASD diagnosed?
During a routine
examination, your doctor may hear a murmur when listening to your
heart. A heart murmur is an additional swishing sound heard in the
heart. If a murmur is identified, your doctor will order other
tests that can include the following:
- electrocardiogram (ECG or EKG) - a test that records the
electrical changes that occur during a heartbeat; reveals abnormal
heart rhythms (arrhythmias) and detects heart muscle stress
- chest X-ray - a test to show the size and shape of the
heart and lungs
- echocardiogram - a test that uses sound waves to create
a moving picture of the heart's internal
structures
- Doppler ultrasound - a test that uses sound waves
to measure blood flow; often combined with echocardiogram to
evaluate both the internal structure of the heart and blood flow
across the heart's valves
- cardiac magnetic resonance imaging (MRI) - a test that
uses three-dimensional imaging to reveal how blood flows through
the heart and how the heart is working
- cardiac catheterization - a procedure that involves
inserting a thin tube (a catheter) into a vein or artery and
passing it into the heart to sample the level of oxygen, measure
pressure changes, and make x-ray movies of the heart and its
internal structures
- angiography - a dye-enhanced x-ray of the heart's
internal structures
Additional tests may be ordered as necessary.
How is an ASD treated?
If you or your child is
diagnosed with an ASD, your primary care doctor will recommend that
you meet with a congenital heart specialist (a doctor who has the
training and equipment to determine the heart problem), who will
order the necessary special tests, medical care, heart surgery, and
follow-up checkups. The best treatment approach will depend on the
patient's symptoms as well as the size of the ASD. The ASD
may need to be closed surgically through open-heart surgery or may
be repaired through an outpatient catheter-based procedure.