The genetics and pathology of discrete subaortic stenosis in the Newfoundland dog - and even if our Leonberger is not a Newfoundland dog, it seems to be of interest to learn that one of the "foundation"-breeds is suffering from that (inherited) condition:

The genetics and pathology of discrete subaortic stenosis in the Newfoundland dog.

Pyle RL, Patterson DF, Chacko S.

Breeding experiments confirm that discrete subaortic stenosis (SAS) in Newfoundland dogs is a specific inherited trait. Specificity of the morphogenetic abnormality is not complete, however, since matings between Newfoundlands with SAS occasionally produced pups with valvular and subvalvular pulmonic stenosis as well as SAS. The spectrum of severity of SAS ranged from a subclinical forme fruste to a severe form causing death before maturity. Well-developed subvalvular stenotic rings consisted of a base of loosely arranged fibrous connective tissue and a subendocardial region of cartilagenous tissue. Severely affected dogs, some of which died suddenly, had foci of necrosis and fibrosis in the left ventricular myocardium, associated with thickening of the intramural coronary arteries. The lesions of SAS were not found in dogs before 3 weeks of age, and the mildest form was seen only in dogs between 3 and 12 weeks of age, suggesting that SAS is not a true congenital defect but develops postnatally. It is hypothesized that the fibrocartilagenous ring of SAS is derived from persistent embryonal endocardial tissue which retains its proliferative capacity and has chondrogenic potential for some time after birth. The results of breeding experiments were not consistent with any simple genetic hypothesis, and indicate that SAS is inherited as a polygenic trait or as an autosomal dominant trait with modifiers.

PMID: 986114 [PubMed - indexed for MEDLINE]

Copyright © 1998 Canine Inherited Disorders Database. All rights reserved.
 

http://www.upei.ca/~cidd/Diseases/cardiovascular%20diseases/aorticstenosis.htm - for those interested to read the article full length, pls. follow the link provided -

related terms: Type A aortic stenosis, Type B aortic stenosis, subvalvular aortic stenosis

What is aortic stenosis?

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.

How is aortic stenosis inherited?

In Newfoundlands, this defect has been shown to have an autosomal dominant mode of inheritance, with variable expression.

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 dogs with very mild or no clinical signs of the disorder.

What breeds are affected by aortic stenosis?

Congenital aortic stenosis is probably the most common heart defect seen in large breed dogs. Newfoundland dogs have the highest risk for this disorder. It is also important in the golden retriever, Rottweiler, and boxer.

There is a mildly increased risk of aortic stenosis in the German shepherd, German short-haired pointer, Great Dane,samoyed and bulldog.

Copyright © 1998 Canine Inherited Disorders Database. All rights reserved.
Revised: September 12, 2005.

This database is funded jointly by the Animal Welfare Unit at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association.