Heart murmurs are sounds that are produced as a result of a disturbance in blood flow.   Murmurs are classified according to a variety of characteristics, including their timing, grade, configuration, and location.  Some heart murmurs can lead to heart failure while others are not progressive.  Without performing diagnostic test, we cannot predict the progression of the disease or decipher the underlying cause of the murmur.

Symptoms of heart failure may include coughing, weakness, open mouth breathing, abdominal breathing, increased respiratory effort, an enlarged distended abdomen and exercise intolerance.

Grading Scale for Murmurs

The grade of the murmur does not necessarily equal or indicate the severity of disease.

• Grade I - barely audible
• Grade II - soft, but easily heard with a stethoscope
• Grade III - intermediate loudness; most murmurs which are related to the mechanics of blood circulation are at least grade III.
• Grade IV - loud murmur that radiates widely, often including opposite side of chest
• Grade V - very loud, audible with stethoscope barely touching the chest; the vibration is also strong enough to be felt through the animal's chest wall.
• Grade VI - louder that grade V, audible with stethoscope barely touching the chest; the vibration is also strong enough to be felt through the animal's chest wall.

In order to determine exactly what is causing these symptoms, the veterinarian must differentiate between a wide range of abnormal heart sounds. They also must differentiate between abnormal lung and heart sounds and listen to see if timing of abnormal sound is correlated with respiration or heartbeat.  The location and radiation of the murmur, as well as the timing during cardiac cycle, is another way to determine the underlying cause.  This can be accomplished by conducting a variety of tests.

Recommended testing can include x-rays, blood work, ECG (electrocardiogram), echocardiogram (ultrasound of the heart), and blood pressure monitoring among other things.  Unless heart failure is evident, your pet will usually be treated on an outpatient basis.  Routine exams, blood work and annual chest x-rays are recommended in order to monitor the progression of the heart murmur and its associated disease.   The course of treatment will be determined based on the associated clinical signs.