Overview of Canine Aortic Stenosis
Aortic (subaortic) stenosis (AS or SAS) is a congenital heart disease that can affect dog.
Aortic (subaortic) stenosis is a narrowing of the pathway for blood leaving the heart. The narrowing is usually beneath the aortic valve of the left ventricle; the condition is then called subvalvular aortic stenosis or SAS for short. SAS is a genetically predetermined disease that affects dogs. The condition is rare in cats. The mode of inheritance, or the genetic cause, is not simple and healthy carriers of the disease genes are common.
Several dog breeds are predisposed to aortic stenosis including golden retrievers, Newfoundlands, boxers, German shepherds, Rottweilers, shar-peis, bull terriers, English bulldogs and Bouvier de Flanders.
Mild cases of SAS have little impact on the dog other than causing a heart murmur and rendering the dog unsuitable for breeding. Moderate to severe cases are at risk for exercise intolerance, fainting, heart failure, irregular heart rhythms, infections on the heart valve and sudden death.
What to Watch For
Diagnosis of Aortic Stenosis in Dogs
Diagnostic tests are needed to recognize SAS and exclude other diseases. Tests may include:
Treatment of Aortic Stenosis in Dogs
For mild cases, there is no treatment. For more serious cases, treatments for SAS may include one or more of the following:
Home Care and Prevention
If your dog has SAS, find out the degree of severity so you can modify your dog's activity. Mild cases of SAS pose no real activity/exercise limitations, but more advanced cases may require some exercise restriction or medical therapy.
Learn to measure your dog's rectal temperature. If your dog is acting sick and has a fever (temperature greater than 103), call your veterinarian immediately.
Schedule regular examinations (every 6 to 12 months) and possibly chest X-rays and/or an echocardiogram.
Breeders should have their dogs screened for SAS. Never breed a dog with congenital heart disease.
In-depth Information on Aortic Stenosis in Dogs
Aortic (subaortic) stenosis (SAS) is a form of genetic heart disease in dogs that is very rare in cats. It is characterized by an obstructive band or ridge of tissue that prevents the normal ejection of blood from the left ventricle of the heart. The defect is located in the outlet of the left ventricle, immediately below the aortic valve, hence the name “subaortic” stenosis (or SAS). This genetic defect develops very early after birth, but the severity of blood flow obstruction may increase as the dog matures. Such progression can be particularly prominent in giant breeds such as the Newfoundland.
The left ventricle reacts to a stenosis (narrowing) by increasing the pressure developed during pumping (systole) and generating a pressure difference that propels the blood out of the heart at a much faster rate. These changes cause disturbed blood flow that, in turn, creates a heart murmur, which can be detected by a noninvasive ultrasound diagnosis using Doppler echocardiography. The increased heart work in moderate to severe obstructions is associated with left ventricular hypertrophy or thickening, myocardial fibrosis (scarring), and coronary artery lesions. Coronary blood flow back to the heart is abnormal and poor blood supply to the heart muscle (ischemia) predisposes to irregular heart rhythms and sudden death.
Clinical surveys have indicated that SAS is now the most common congenital heart disease in the dog in many areas. Commonly affected breeds include the golden retriever dog, Newfoundland, boxer, and German shepherd. Recent clinical and breeder surveys indicate the emergence of SAS in other breeds including the Rottweiler, shar-pei, bull terrier, English bulldog and Bouvier de Flanders. Breeding experiments have confirmed that SAS is inherited in these breeds, but the precise mode of transmission has not been proven. The disease does not appear to be transmitted by a gene or as a sex-linked trait. It is important to note that even mildly affected or clinically normal parents may transmit the defect to future generations.
The presence of a heart murmur in a puppy, especially in breeds at risk should be investigated; SAS is only one cause of a murmur. In diagnosed cases, any of the following symptoms should prompt a visit to your veterinarian:
Advanced cases of SAS can lead to complications including heart failure, heart arrhythmia (irregular heart beating), fainting (syncope) or sudden death. Also, heart valve infections can occur in this condition leading to fever, illness and joint ache.
Other heart problems can appear similar to aortic stenosis. These are differentiated based on the history, physical examination, and the echocardiogram. These diseases include:
SAS can occur concurrently with other heart defects.
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth of Aortic Stenosis in Dogs
Diagnostic tests are needed to recognize aortic (subaortic) stenosis, and exclude other diseases. Tests may include:
Breeders like to speak of the “grade of SAS,” which usually refers to the grade or intensity of the heart murmur. The intensity or grade of the heart murmur depends on the “tightness” of the stenosis and other factors as well. It is generally true that a soft murmur (grade I or II out of a possible VI) is typically a “mild” defect while a grade V or VI murmur is usually related to a more severe defect.
Murmurs can be variable and a soft murmur may first be obvious in a mature dog of breeding age. For practical purposes, most dogs can be screened at one year of age for “final” heart clearance if the dog is intended for breeding. It is also crucial to understand that this clearance represents a clinical description and does not tell us the dog is free from the genetic liability for aortic stenosis.
If your veterinarian suspects congenital heart disease, referral to a cardiologist is usually the best course, unless your veterinarian is particularly experienced in congenital heart defects. Commonly recommended tests are echocardiography (ultrasound of the heart) with Doppler studies (blood flow studies using the Doppler ultrasound method), and often chest X-rays and an electrocardiogram. The last two tests are useful only in moderate to severe disease.
Treatment In-depth of Aortic Stenosis in Dogs
Therapy of moderate to severe SAS has generally been disappointing. While technical success can be achieved surgically, long-term survival has not been satisfactory. Specialists can dilate the area with a balloon catheter, but the long-term benefits of this have proved no better than surgery. Chronic management of aortic (subaortic) stenosis may include:
Prognosis of Dogs with Aortic Stenosis
Optimal treatment for the dog with moderate to severe SAS requires a combination of home and professional veterinary care. Follow-up can be critical.
Administer any prescribed medication as directed by your veterinarian. Be certain to alert your veterinarian if you are experiencing problems while treating your dog, especially collapsing with exercise, difficulty in breathing, coughing or signs of illness with fever.
Schedule regular examinations every 6 to 12 months, including perhaps chest X-rays and/or an echocardiogram.