Aortic Stenosis In Golden Retrievers

In aortic stenosis, there is a partial obstruction to the flow of blood as it leaves the left side of the heart (the left ventricle) through the main blood vessel (the aorta) that carries blood to the rest of the body. The obstruction ranges from small nodules to a fibrous band, most commonly just below the aortic valve ("subvalvular aortic stenosis"). Due to the obstruction, the heart must work harder to pump out an adequate blood volume. Clinical signs and long-term outcome depend on the degree of narrowing, or stenosis.

In the mildest form, the condition is undetectable and will not cause any problems for the dog. However the defect may still be passed on to offspring. The challenge for breeders and veterinarians is to identify affected Golden Retrievers with very mild or no clinical signs of the disorder.

Golden Retrievers with mild stenosis will generally show no clinical effects and have a normal life expectancy. With moderate to severe stenosis, signs will be variable. Because of the narrowing in the aorta as the blood leaves the left ventricle, your Golden's heart must work harder to pump an adequate volume of blood to the rest of the body. Depending on the degree of obstruction, your Golden's heart may be able to compensate at rest but not keep up with the body's demands during exercise. Thus you may see reduced exercise tolerance  - your Golden just seems to run out of steam - or fainting due to inadequate blood supply to the brain.

In response to the obstruction to blood flow, the heart muscle becomes thicker over time (left ventricular hypertrophy). As the condition progresses, your dog's heart becomes less able to compensate and you and your veterinarian may see signs associated with left-sided heart failure such as tiring on exercise, difficulty in breathing, coughing, and/or poor growth. Changes in the heart muscle can also lead  to abnormal heart rhythms (cardiac arrythmias) and sudden death.

Your veterinarian can do various tests (see below) to determine the severity of the defect. Based on the results, he or she will discuss with you the long-term prognosis, and ways to manage this condition in your Golden Retriever.

In young Golden Retriever (less than 6 months of age) there may be no clinical signs. Thus the first indication that your dog may have a problem may come when your veterinarian hears a heart murmur during physical examination. Some low-grade murmurs are "innocent" and disappear by 6 months of age, but if the murmur is significant, your veterinarian will suggest a diagnostic workup to determine the cause. He or she will listen very carefully to your dog's heart to determine the point of maximal intensity of the murmur and when the murmur occurs during the cardiac cycle. Other diagnostic aids include chest x-rays, an electrocardiogram (ECG) and/or ultrasonography if available. To determine the extent of the narrowing, the pressure gradient  across the aortic valve (between the left ventricle and the aorta) can be measured using special procedures for which your veterinarian can refer your Golden Retriever to a specialist.

In an older Golden Retriever or when the obstruction is pronounced there may be clinical signs associated with left-sided heart failure.

Based on the results of these various tests, your veterinarian will discuss with you the prognosis and long term management of your Golden Retriever. She/he will also be able to tell you if any (and how much) change has occurred in the heart already as a result of the stenosis.

Re-printed with permission from Canine Inherited Disorders Database