Subaortic stenosis (SAS) is an inherited heart disease of large breed dogs. In subaortic stenosis there is a narrowing in the left side of the heart (ventricle) whose function is to pump blood to the whole of the body via the aorta. The stenosis means that the left ventricle must pump harder to get the correct blood volume through the narrowed area. The blood squirts through the stenosis in a turbulent fashion which creates a sound known as a ‘heart murmur.’
Because the heart has to pump against the increased resistance and continuously generate high pressures, there is an increased risk of dogs developing heart muscle damage and even heart failure. The extent of the symptoms and the rate at which they develop depends on the severity of the narrowing inside the heart and will vary between individual dogs.
Abnormal muscle in the heart causes abnormal electrical conduction in the heart and the heart’s normal electrical rhythm is disrupted. Because the pumping and filling actions are coordinated electrically, when this coordination is lost, fainting spells or even sudden death while exercising can result. Most dogs with SAS do not survive beyond three years of age without treatment, although dogs with milder cases can have normal life spans. A dog with SAS is always predisposed to electrical arrhythmia, heart failure, and infection of the abnormal aortic valve.
Dogs used for breeding should have a clear heart certificate issued by a specialist with an interest in cardiology certifying that the dog has no auscultatory evidence of heart disease.