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Canine Subaortic Stenosis
Stenosis means narrowing; subaortic stenosis (SAS) refers to the narrowing of the area of the heart just below the aortic valve. The narrowing develops due to the presence of an abnormal fibrous tissue. The narrowing causes the increase of blood pressure in the left ventricle.
Breeds at Risk for Subaortic Stenosis
This is the third most common congenital genetic heart defect in dogs. Breeds predisposed include Newfoundland,
Boxer, Golden retriever, German Shepherd, Rottweiler, Bouvier des Flandres, Bull Terrier, and Bernese Mountain Dog. An unusual form of subaortic stenosis in combination with mitral valve dysplasia has been reported in Golden retrievers.
Diagnosis
Dogs with mild form of the disease and those who develop infective endocarditis are usually diagnosed at older ages than those with moderate and severe. Sudden death occurs mainly in the first three years of life, primarily, but not exclusively with severe obstruction. Infective endocarditis and left heart failure tend to occur later in life and in dogs with mild to moderate obstructions.
Signs
Most dogs do not have any signs. Others may experience episodes of fainting and difficulty breathing. Signs may develop in affected puppies within the first month of life and can include stunted growth, weakness, shortness of breath, abdominal swelling and, in extreme instances, sudden death. Most SAS patients are diagnosed when heart murmur is detected at the left heart base during a routine physical examination. Affected puppies are usually alert and otherwise healthy.
Treatment and Prognosis
Medical treatment is directed towards decreasing the workload on the diseased heart. Surgical correction of the defect may be attempted, yet owning to the nature of the disease and the age of the affected dog, the outcome of such a procedure is generally poor. Caridiopulmonary bypass and open-heart surgery are necessary to directly reach the stenotic area. Although this type of surgery can significantly reduce the ventricular pressure and possibly improve exercise ability, no improvement in long-term survival was found compared to dogs not undergoing the procedure.7 Atenolol, a specific adrenergic drug, has been used to prevent sudden death in dogs with severe subaortic stenosis. Prognosis and therapy depend on the severity of the disease and complications that may be present.4
The majority of severely affected dogs with SAS die suddenly before the age of 3 years. However, the increasing availability of modern diagnostic imaging systems now allows a better assessment of cardiac function, thereby facilitating early detection of the disease. Dogs with mild pressure rarely progress to congestive heart failure (CHF). If CHF develops, it can be managed with medications that can prolong quality and length of life.
References
- Falk T, Jönsson L, Pedersen HD. J Small Anim Pract. 2004 Sep;45(9):448-53. Intramyocardial arterial narrowing in dogs with subaortic stenosis.
- Robert M. Freedom, Shi-Joon Yoo, Haverj Mikailian, William G. Williams. The natural and modified history of congenital heart disease
- O. M. Radostits, Ian G. Mayhew, Doreen Marie Houston. Veterinary clinical examination and diagnosis
- Jim E. Riviere, Mark G. Papich. Veterinary Pharmacology and Therapeutics
- John K. Dunn. Textbook of small animal medicine
- Chris C. Pinney. German Shorthaired Pointer
- Richard W. Nelson, C. Guillermo Couto. Small Animal Internal Medicine
- Matthew J. Ryan, Veterinary Hospital Section Of Cardiology, UPENN. Understanding Canine Subaortic Stenosis
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