Congenital Heart Disease

Your pet was born with a conge4nital heart defect. Congenital
defects are abnormalities that occur in the developing fetus and
are usually recognized soon after birth. If the defect is too
severe, the embryo dies before birth. Other situations, not as
severe, allow embryo development to birth, and the pet can live
until the defect interferes with normal functioning (here, the
cardiovascular system).

Most congenital defects are first recognized at or near the time
of weaning when the pet is taken to the veterinarian for the
first examination. Sometimes these problems may not be
identified until later in life. Congenital defects are most
often the result of abnormalities in the genetic makeup of the
pet. The abnormal genes may or may not be present in other
members of the litter but are carried by the mother and/or
father, sometimes without compromising their health. Other
causes of congenital defects include exposure to radiation,
toxins, or physical events that occurred during the animal’s
embryonic stage.

There are numerous ways to classify congenital heart defects,
but for simplicity we will consider them in four major
categories: (1) obstruction of blood flow within the heart; (2)
abnormal communication between the two sides of the heart,
increasing the blood flow from the left (systemic) to the right
(lung) side of the heart; (3) abnormal communications sending
blood in the opposite direction of flow, from the right (lung)
to the left (systemic) side of the heart; and (4) vessel
(vascular) abnormalities that obstruct a body part and interfere
with normal function.

Obstruction of blood flow within the heart includes conditions
such as pulmonic, mitral, or aortic valvular stenosis. Valvular
obstruction is caused by a narrowing of an area of blood flow,
decreasing circulation from the heart to some part of the body.
These conditions vary from mild to severe. They may be minimal
and require no care. However, in other cases, medication only,
opening the obstruction with a special catheter, or surgical
correction may be needed. Surgery, although commonly performed
in humans, is both difficult and infrequent in veterinary
medicine.

Blood may flow abnormally from the left to the right side of the
heart because of a hole between the two sides of the heart that
did not close during embryonic formation. One such condition,
patent ductus arteriosus (PDA), is a remnant of normal embryonic
heart function.

If PDA is diagnosed early, it may be corrected surgically and
the pet may be able to lead a normal life. Other conditions such
as ventricular or atrial septal defects involve a hole between
two chambers of the heart. Closure of septal defects requires
open heard cardiopulmonary bypass surgery, which is infrequently
performed in veterinary medicine.

Blood flow from the right to the left side of the heart without
passing through the lungs is very abnormal and quite uncommon.
Thus, a serious communication problem exists that results in
unoxygenated blood being transported to the body. Such a
situation usually does not allow the pet to live beyond early
adulthood. Because of the complicated nature of these problems,
open heart surgery is rarely an available option. Surgical
procedures may be available at teaching and specialty clinics to
treat such problems.

Persistent aortic arch, peripheral arteriovenous shunts, and cor
triatriatum are heart problems that are the result of abnormal
vessels interfering with normal blood flow. These conditions can
usually be corrected surgically if identified early, before
complicating problems develop to preclude normal life.

Because many congenital heart defects are thought to be due to
genetic problems that can be passed from one generation to the
next, veterinarians recommend that animals with such conditions
be neutered at an early age to prevent breeding and the
dissemination of defective genes to a new generation. Some
congenital heart defects may be surgically corrected; others are
effectively dealt with for variable periods using medication.

Regrettably, most congenital heart defects have a poor long-term
prognosis. It is sad for the owner and for the pet to suffer
needlessly. In selected circumstances, euthanasia may be
recommended if the pet is unable to maintain a good quality of
life. A number of more complicated congenital heart defects are
not covered in this handout. If such a situation exists in your
pet, your veterinarian will be able to discuss it with you and
will probably refer you to a specialist with additional training
and diagnostic equipment.

A congenital heart defect is suspected after a thorough physical
examination has been performed. The electrocardiogram helps to
identify the presence of abnormal heart chamber size as well as
irregularities of the heart’s rate and/or rhythm. Radiographs
(x-rays) are needed to visualize abnormalities in the size and
appearance of the heart, vessel, and lung structures. The
ultrasound (echocardiogram) examination is a direct, noninvasive
means of looking inside the heart’s walls to measure the size of
the heart’s four chambers and to identify abnormalities
(qualitatively and quantitatively) in blood flow. Occasionally,
more invasive procedures such as cardiac catheterization
(passing small tubes into the heart and blood vessels and
injecting dye) or surgical evaluation may be recommended.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.