Download Ventricular and Atrial Septal Defects

Ventricular and Atrial Septal Defects
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Ventricular and atrial septal defects are congenital heart deformities that are present at birth. An atrial septal defect (ASD) is a hole
in the membrane between the atria, the two smaller chambers of
the heart. An ASD can be any size and can be located in different
parts of the membrane.
A ventricular septal defect (VSD) is a hole in the septum, the
tissue that separates the two larger chambers of the heart (the ventricles). Most VSDs are small and are located just below the aortic
valve.
Causes
Some breeds of dog develop ASDs and VSDs because defective
genes cause the holes to form while the heart is developing. If
a pregnant dog is exposed to certain toxins, infections, or drugs
while the puppies’ hearts are developing, then ASD or VSD could
also occur. Most of the time, the cause of the VSD and ASD is
not known.
Clinical Signs
Most ASDs are small and do not cause much of a problem and may
not produce a murmur. They may be discovered as an incidental
finding when your dog has an echocardiogram (heart ultrasound)
for another reason. If the ASD is large or is associated with other
congenital heart defects, signs of right- or left-sided heart failure
may be present. These signs include increased rate and effort of
breathing, possibly coughing, and exercise intolerance. Cats are
more prone to large ASDs associated with other congenital defects
and are more likely to have signs of heart failure.
Most VSDs are small but cause loud murmurs that are detected
on a physical examination. Most dogs and cats with small VSDs
never have clinical signs; however, if the VSD is large or is associated with other congenital heart defects, the dog or cat can develop
signs of left or right heart failure.
Diagnostic Tests
If your animal has a murmur typical of an ASD or VSD, your
veterinarian may recommend chest x-rays followed by echocardiography with Doppler capabilities. Not all veterinarians have the
equipment needed to perform this last test, so you may be referred
to a veterinary specialist for the procedure. These tests usually
confirm the diagnosis and determine the size of the ASD or VSD.
If an abnormal heart rhythm (arrhythmia) is detected, an electrocardiogram (ECG) may be done. If the ASD or VSD needs to be
repaired via surgery or catheter occlusion, then laboratory tests are
often done prior to anesthesia. A cardiac catheterization procedure
is also usually performed prior to repair of the defect.
TREATMENT AND FOLLOW-UP
Treatment Options
Small ASDs and VSDs usually are not corrected, because they do
not commonly shorten an animal’s life span. If the ASD or VSD
is large and has resulted in heart failure, the heart failure is treated
with diuretics (furosemide), vasodilators (enalapril), and an agent
that improves heart contractions (pimobendan). Other drugs may
be needed to control any arrhythmias that are present.
Surgical repair of large ASDs or VSDs is usually done at specialized facilities that can perform open-heart procedures on dogs.
Only a few such facilities exist in the United States. The dogs must
also be large enough to undergo heart bypass surgery.
Some of the larger ASDs and VSDs can be closed with an
Amplatzer device that is placed via a cardiac catheter. This treatment option also requires referral to a veterinary cardiologist who
can perform the procedure.
Follow-up Care
Yearly x-rays are commonly done in dogs and cats with ASD or
VSD to evaluate heart size and to monitor the lungs for signs of
heart failure. Notify your veterinarian immediately if any of the
clinical signs of heart failure develop.
Prognosis
Animals with a small ASD or VSD often do well and have a normal life span, with no complications. The bigger the hole in the
heart, the more likely it is that heart failure will develop, and the
younger the animal will be when that failure occurs. Animals with
heart failure can often be successfully managed with medications
for months or possibly 1 year.
Because ASDs and VSDs are inherited in some breeds, animals with these defects should not be bred, in order to prevent the
spread of this problem. A female with a large ASD or VSD is also
likely to go into heart failure during the last trimester of pregnancy
because of the increased volume of blood her body must handle
due to the developing fetuses.
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