Heart Murmurs in Horses

January 16, 2012 (published) | January 22, 2020 (revised)

Heart murmurs are common in small dogs as they get older and until they get severe, murmurs are generally not a problem.  Heart murmurs in cats are far less common. Any murmur heard in a cat should be considered potentially significant and further testing is warranted.  Murmurs in horses are also uncommon, and Dr. Chris Navas discusses two of the most common types in Teva Remuda. 

In general, there are two types of murmurs that horses get and they are characterized by when they appear in the cardiac cycle.  Systolic murmurs occur after the first beat and diastolic murmurs occur after the second beat.  The most common diastolic murmur occurs in older horses and is related to aortic regurgitation. Generally, it is due to degeneration of the aortic valve.  If your veterinarian hears this murmur, it is important to check the horse’s pulse. If the pulse is bounding or really strong, the heart problem is likely fairly severe.  The reason this is important is that horses with severe aortic regurgitation are susceptible to ventricular arrythmias and other heart problems and could collapse, and likely injure a rider.  Most horses with this murmur live normal lives and have successful athletic careers, but it is important to know that they have this murmur. 

Another common murmur is systolic, which is heard on the horse’s left side and is the same one commonly found in small breed dogs. It stems from mitral regurgitation.  This murmur can lead to heart failure and cause exercise intolerance, increased respiratory effort, and increased heart rate followed by foam coming out of the horse’s nostrils. The foam is from fluid in the lungs.  So, it is important for your veterinarian to listen to your horse’s heart at every visit to check for a heart murmur.

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