Heart murmurs are abnormal heart sounds which is a result of abnormal blood flow into, through or out of one or more heart chambers. Murmurs are extra heart vibrations that are produced as a result of a disturbance in the blood flow. Instead of the normal Lubb Dupp, an additional sound is present that can vary from a mild pshhh to a loud whoosh! This abnormal sound is loud enough to be audible using a stethoscope.
Heart murmurs is not a disease, rather a sign of a possible cardiac condition. It can be due to congenital heart defect or an acquired condition due to a variety of causes.
Murmurs are classified on the basis of a variety of characteristics including timing. A systolic murmur is when the heart muscles contract while a diastolic murmur occurs when heart muscles relax. Continuous and to-and-fro murmurs occur throughout or most of the cardiac cycle.
Murmurs are also graded on their intensity, on a scale of one to six (1-6). Grade 1 murmurs are very subtle and soft, intermittent and usually heard only in one location on the chest while grade 6 murmurs are very loud, audible everywhere the heart can be heard, and can be felt by placing a hand on chest.
Murmurs are further divided on the basis of whether they are long or short and by their location or the area where they are loudest.
Many a times, a dog with heart murmur will be asymptomatic (without symptoms). This means either the murmur is physiological or "innocent" (murmurs that cause no heart condition and usually outgrow with age) or that heart condition has not yet developed so as to cause clinical signs. When a dog does show symptoms, they are usually related to signs of congestive heart failure and may include
Decreased activity level
Panting (even at rest)
Respiratory distress; difficulty breathing (even at rest)
Pale mucous membranes
Pot-bellied appearance; abdominal distension (from fluid retention)
Fainting spells; collapse