It is always an exciting time to get a new puppy or dog, unfortunately many new owners don't consider all the possible health issues that may be associated with different breeds. In some of the medium to large breeds such as the Golden Retriever, Bullmastiff, Rottweiler, Boxer and Newfoundland the condition is considered the leading cause of heart conditions within the breed.
Sub-aortic stenosis is a congenital and inherited condition, which means that it is passed on through the parents and is present when the puppy is born. What the condition actually consists of is a narrowing of the opening between the heart's left ventricle and the aorta, the major blood vessel carrying blood that is rich in oxygen to the rest of the body. The narrowing is actually caused by a thickening or the walls or a ring of scar tissue that is formed inside the aorta just at the ventricle, which will decrease the volume of blood that can be carried out of the heart to the body.
The exact genetic causation of sub-aortic stenosis does not appear to be the same in all breeds of dogs. The Newfoundland breed has been extensively studied and in these dogs it appears to be an autosomal dominant gene but that there are several other factors that can decrease or increase the problem with sub-aortic stenosis within a puppy. This has complicated the process both for research as well as for identification. Many dogs will have sub-aortic stenosis (SAS), but because the effects are so mild they may never be diagnosed, leading to problems in limiting these dogs from the breeding population.
Typically SAS does not get worse over time, rather the results of the heart having to work harder to pump the blood through the narrowed aorta is what causes the problem. In cases where the SAS is significant congestive heart failure or sudden death are very common outcomes to the condition. Since there is less blood being pumped through the left ventricle the heart must pump harder, often resulting in swelling of the muscles and thickening of the heart walls. In addition more pressure is placed on the mitral valve, which can lead to further problems with leakage of the blood backwards through the heart chambers. Symptoms of SAS are often first noted with heart murmurs followed by increased fluid on the lungs, coughing, lack of appetite and energy and weakness and fainting. In many dogs death will be sudden and unexpected as owners just assume the dog has a slight respiratory infection. Blood clots may also be a problem for dogs with SAS, especially if the condition is severe.
There is no cure for SAS, but early diagnosis is important to start drug therapies to support the heart function. Medications to strength the heart walls, dilate the circulatory system and to help prevent inflammation of the heart are important in moderate to severe cases. In mild cases of SAS the dog will need a very controlled diet to avoid any increased weight, regular exercise and careful monitoring of heart functioning as the dog ages. Chest x-rays can be used to confirm the condition and breeders should be notified immediately to prevent producing further litters with the condition. The puppy should be spayed or neutered as soon as possible to prevent breeding and passing on SAS.
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