•Heart murmurs. These abnormal heart sounds are usually caused by an abnormal heart valve. Heart murmurs can be congenital or acquired. While many congenital murmurs will never cause a problem during the dog’s lifetime, some can cause problems later on, and some may be early signs of more serious heart problems. Some heart murmurs are caused by a viral assault. Cardiomyopathy may be caused by such viral infection. If it appears that the dog is developing normally and there are no other clinical signs of heart disease, the murmur may be considered "innocent".
•Sub Aortic Stenosis (SAS) is characterized by a narrowing of the outflow track from the left ventricle of the heart to the aorta. Thankfully, SAS is a relatively uncommon cause of a heart murmur. However, it can be life threatening and does show up from time to time. SAS is known to be hereditary. It is usually diagnosed with an echocardiogram and can be treated with medications.
•Cardiomyopathy. This is, literally, "sick heart muscle".
While weakness, lethargy, stunted growth, exercise intolerance, fainting, or abnormal heartbeats (arrhythmias) may be present, both of these heart conditions (SAS and cardiomyopathy) can also progress undetected until they result in sudden death. Listening to the heart with a stethoscope is the first step in assessing a dog’s cardiac condition, but it is not always adequate, especially in a short-nosed breed such as the Bullmastiff. Further tests involving EKGs and cardiac ultrasound may be indicated. A consultation with a canine cardiologist is recommended when abnormalities are detected. Some treatments to manage cardiac disease are available through your veterinarian.