Cardiac murmur in dogs

Dear Prof McCrindle,

I recently took my dog to be sterilised. She is an 18-month-old German Shepherd. The sterilisation went well, but the vet told me that she had heard a murmur while listening to her heart. She has never shown any symptoms of a heart problem and is a very active dog (no breathlessness, fatigue or coughing). The vet said she may grow out of it. Kind regards,

Frank

Dear Frank,

Heart murmurs can be very serious, depending on the cause. A sound similar to a heart murmur can, however, occasionally be heard when a dog is put under anaesthetic. It can also be due to the surgery itself, as there is sometimes blood loss, which leads to lowered blood pressure and a cardiac murmur.

When she goes back to have her stitches taken out, ask the vet to listen to the heart again to see if the murmur is still there.

The literature describes abnormalities in the mitral valve on the right side of the heart as a common factor in German Shepherds. It could be a heritable condition, passed on by her parents. Although I have noticed murmurs in several German Shepherd dogs over time, it is seldom that I have seen any typical signs of chronic heart failure.

You have had your dog sterilised, which means she will not pass this genetic factor on to puppies. The signs of heart failure include heavy breathing, fluid in the lungs, and a chronic cough. Due to poor circulation, she may tire on long walks or lack energy, sleeping all day. Sometimes fluid accumulates in the abdominal cavity, and this is known as ascites.

There are several different reasons for heart murmurs in dogs. The most important and often neglected reason is chronic, ignored parasitic disease.

German Shepherds can easily be infected by hookworm at a very early stage in life and this parasite can cause severe anaemia, which also results in heart murmurs. Severe roundworm infestation of the stomach and intestines is another cause of anaemia, for different reasons. This common verminous parasite can easily cause chronic malnutrition. When last was your dog dewormed?

Another major cause of heart murmurs is malnutrition due to a poorly balanced diet. German Shepherds are large, very active dogs and they need a diet that contains enough protein, essential minerals and fatty acids to rebuild their muscles. They are very excitable and energetic, so a poorly balanced diet can affect their muscles, including the heart muscles, in the long run.

It’s worth taking a blood test to check for infections, parasites or anaemia, as well as a faecal sample to look for parasite eggs. If she begins to show signs of heart failure, such as pale gums, panting or coughing, it would be a good idea to consult a canine cardiologist. There are affordable chronic medications available for canines with cardiac problems. Kind regards,

Prof Cheryl McCrindle

ȊȲSource: Borgarelli et al, 2024. ‘Comparison of primary mitral valve disease in GSD and small breeds’. Journal of Veterinary Cardiology 6(2)pp27-33. Visit pubmed. ncbi.nlm.nih.gov/19083307/.