Subaortic stenosis is a narrowing of the area just below the heart valve leading to the aorta, the major blood vessel leading out of the heart. The stricture overloads the right ventricle of the heart. Signs of SAS often don’t develop until around 18 months of age. They include coughing, fainting, murmur, exercise intolerance, high heart rate, and lethargy. If SAS has gone undiagnosed in an older dog it can die suddenly. The condition may be detected when a murmur is noted by an examining vet; location in the heart and when during the heartbeat the murmur is loudest are indicative of SAS. Definitive diagnosis requires echocardiography. Prognosis for the affected dog varies. Some never show signs of disease, while for others it is fatal. Surgery usually does not help. There is no effective treatment for SAS though if the disease advances medication may relieve some symptoms. Long-term prognosis is often a shortened lifespan.
SAS is rare in Australian Shepherds. It is inherited in several breeds where it is common and, due to its serious nature, should be assumed to be so in Aussies for breeding purposes. Affected dogs should not be bred. Littermates should not be bred and serious consideration should be given to retiring the parents. At the very least they should never be bred to each other again or to any near relatives of their own or the other parent’s. Males that have produced SAS should not be used frequently. Anyone having puppies from them should be made aware this is a potential. Other relatives might be bred but only to mates that do not have a family history of SAS.