What Do Heart Murmurs in Your Cat Indicate?


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Extra vibrations in the heart due to disturbances in the blood flow produce an audible noise, referred to as murmurs. They are classified according to a number of characteristics, including the timing. For instance, systolic murmurs can be heard when the muscle in the heart contracts and diastolic murmurs can be heard when the heart relaxes in between beats. Continuous murmurs can be heard throughout the lifetime of the heart cycle.


The symptoms of murmurs depend on a lot of characteristics, from grade and location to configuration. However, if the murmur is the consequence of a structural disease, you will see signs of congestive heart failure, like weakness, coughing and exercise intolerance.

Grading scale
  • Scale 1 โ€“ Barely audible
  • Scale 2 โ€“ Soft, but can be heard quite easily with a stethoscope
  • Scale 3 โ€“ Intermediate loudness; a lot of the murmurs that are related to blood circulation are scale 3
  • Scale 4 โ€“ You can hear a loud murmur which radiates widely, often to the opposite sides of the chest
  • Scale 5 โ€“ Very loud and it is audible even when the stethoscope barely touches the chest. The vibration is strong and can be felt through the chest wall of the animal
  • Plateau murmurs and uniformly loud and are a symptom of blood regurgitation through an abnormal orifice in the valves.
  • Decrescendo-crescendo murmurs tend to get softer and then louder and are symptomatic of ejection murmurs due to a turbulence in the blood flow.
  • Decrescendo murmurs start out loud and get softer โ€“ they are symptomatic of diastolic murmurs.

Murmurs are caused due to:

  • Disturbances in the blood flow due to a high flow through abnormal or normal valves or due to structures vibrating when the blood flows.
  • Flow disturbances due to an outflow obstruction or because of forward flow through a diseased valve or into a dilated vessel.
  • Flow disturbances due to regurgitant flow from an incompetent valve, a septum defect or patent ductus arteriosus.

In order to figure out the exact cause of the symptoms, your vet must be able to differentiate between a number of heart sounds โ€“ ejection sounds, split sounds, clicks and gallop rhythms, for instance. He/she must also be able to tell between abnormal heart and lung sounds, and listen to see if the timing of abnormal sounds correlates with heartbeat or respiration.The radiation and location of the murmur, as well as its timing during the cardiac cycle, is another way of figuring out the underlying cause. This can be accomplished by doing a wide number of tests, including Doppler studies, chest X-rays and echocardiography. A complete blood panel is the preferred way of confirming an anemic murmur.


Unless there is indication of heart failure, you cat will be considered an outpatient. The treatment course depends on the clinical signs. Cats with low-grade murmurs, for instance, do not need any treatment and the murmur will resolve itself in six months.

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