Veterinary care should include diagnostic tests and subsequent treatment recommendations.Diagnosis In-depth
Diagnostic tests are needed to recognize aortic (subaortic) stenosis, and exclude other diseases. Tests may include: Complete medical history and physical examination
Currently, no blood test is available to detect the genetic markers of SAS in dogs.
Dogs without heart murmurs are unlikely to have SAS, and routine use of costly Doppler studies is not justified for screening purposes.
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.
Referral to a specialist. If a heart murmur is detected in a puppy, the possibility of an innocent heart murmur or congenital heart defect must be considered. This distinction can be difficult and may require examination by a veterinary cardiologist. In general, innocent murmurs are very soft, are detected best over the left side of the chest, become softer with growth and are absent by the time of the first rabies vaccination at four to six months.
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.
Doppler echocardiography is the diagnostic test of choice and usually requires a referral to a specialist. Doppler echocardiography (DE) is the method most often used today for evaluating dogs with systolic murmurs. This test is a sophisticated examination, but like any laboratory test, there is some overlap between normal and abnormal. This is just one of the reasons why cardiologists don't recommend the Doppler as a routine screening test. The severity of the disease, the size of the heart, the function of the heart chambers, and the tightness of the obstruction can be determined by this test.
Specialists rarely suggest cardiac catheterization.
A 24-hour electrocardiogram (EKG) may be recommended in some cases.
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:
Drug therapy. The use of drugs called beta-blockers has been advocated to reduce myocardial oxygen demand and prevent irregular heart rhythms.
Medical therapy is indicated in cases of heart failure. Common treatments include administering digoxin, enalapril or benazepril, and/or furosemide. These medications can stabilize the dog, but the long-term prognosis is poor once congestive heart failure has developed.
Exercise should be restricted.
The prognosis for dogs with SAS varies with lesion severity. Mild lesions may not compromise quality of life or longevity, but moderate to severe lesions often lead to fainting (syncope), weakness with exercise, congestive heart failure (fluid or edema in the lungs) or sudden death. Infection of the heart valve (endocarditis) occurs in a very small percent of dogs with this condition. A fever is the telltale sign and requires urgent care.