A horse’s heart rate changes with exercise, stress, pain, surprise, anxiety, cardiovascular shock, anemia, endotoxemia and metabolic abnormalities as well as disease of the heart itself.
Murmurs and arryhthmias, and missing beats are common in horses and can reflect heart disease, but most are considered normal findings. If you are listening to your horse’s heart anyway (for rate) you have an opportunity to listen for normal and abnormal heart sounds.
Approach your horse's left shoulder and make contact with the horse. Place the stethoscope in your ears correctly (ear pieces pointed forward) and place the stethoscope head as far toward the head, under the muscle mass of triceps as possible. Now listen.
Each lub-dub is one beat. The beats should be regular, drum-like, crisp and sharp sounding. There should not be hissing or whooshing noises associated with the beats. If there is, share this finding with your vet.
Tips for safety & Success
It is more difficult to hear the heart of a heavy horse, especially obese horses and draft breeds. The heart is much easier to hear in foals, thin body-walled yearlings and lightly built horses.
When in doubt, push the stethoscope along the rib cage and toward the head, under the large triceps muscle mass in front of the girth.
It is much easier to hear the heart on the left side of the chest than the right.