The vet said my dog might have a muffled heart

Our question this week was:

The vet said my dog might have a muffled heart. What is this and are there any treatments?


Bob Gibb


Hi – thanks for your email. You question is about what is a muffled heart and what causes it.

In a normal dog, heart sounds result from the heart beating. As the heart beats, heart sounds result from blood is being pumped through the heart as the heart valves open and close. The normal heart sounds are clear and consist of two basic components often referred to as a "Lub–Dub" sequence of sounds.

Heart sounds can be abnormal – such as when there is a murmur present or muffling.

Your question refers to muffling. Muffled means…"you can't hear something very well". The sounds may be less clear or sound far away. This is can be caused by a few reasons, some of which are not serious and others which are serious.

For example, if you put the stethoscope in the wrong place – the heart sounds can be less clear. Heart sounds can also be slightly muffled in some grossly obese patients. The most concerning cause for muffled heart sounds relate to abnormalities of the heart such as a pericardial effusion.

Pericardial effusion is a condition in which the sack that surrounds the heart fills up with fluid and therefore puts pressure on the heart and creates a layer between the stethoscope and the heart – thus causing a muffled sound.

An article that might be helpful to you is on our is "Pericardial Effusion in Dogs"

If you dog is symptomatic, experiencing symptoms such as lethargy, weakness, trouble breathing, or not eating – then you should be concerned. A couple tests can determine if pericardial effusion is present. One is a chest radiograph and the other (the best way) is an echocardiogram.

Ask your veterinarian why he things the heart is muffled and if he recommends any tests.

Best of luck!

Dr. Debra

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