Congenital Heart Disease (CHD) is a malformation of the heart and/or great vessels, and becomes more severe as the puppy grows. Most often this disease is inherited from the parents. Breeders try to screen for CHD but it can be difficult or impossible to detect with 100% accuracy.
SAS (Sub-Aortic Stenosis)
SAS is the most common form of CHD. To put it simply, SAS can be explained by comparing blood from the out-flow tract from the left ventricle to the rushing water from an ordinary garden hose. If you put your finger over a hose without a nozzle, the water will be restricted and the sound of the flow will become noisier like that of a heart murmur. As the dog matures, he develops more heart muscle to push harder resulting in irregular heart beats.
SAS may show no signs or warning. If your Rottie has heavy panting from short walks (5 or 10 minutes) you might want to get him checked. Talk to a cardiologist for sure as general practitioners are not always good at cardiac stuff. Also keep in mind that puppies will sometimes outgrow these murmurs.
Unfortunately, several breeds of dogs are prone to this disease and emphasis must be put on careful heart screening of the parents before breeding. As technology and screening tests improve, it will become easier for breeders to prevent this disease. The sad and true fact is SAS can be devastating on you and your Rottweiler as it may cause congestive heart failure or sudden death.