Heart Murmurs

Heart murmurs are abnormal noises that can be heard amongst the normal heart sounds of your horse. Although they can sometimes indicate a problem with your horse’s heart, in most instances these murmurs are harmless. In fact in a study involving racing thoroughbreds it was found that only 1 in 10 did not have an audible murmur.

What causes heart murmurs?

The normal sounds (beats) of the heart are caused by the sudden changes in the direction and speed of the blood as it is pumped through the heart. Heart murmurs are simply any noise other than the normal beats. Many murmurs are considered not to be related to a problem. Due to the anatomy of a horse (e.g.thin skin, low heart rate) these non-problematic noises are simply heard more frequently than in other animals and humans. These sounds are also more noticeable if the horse is excited or stressed.

A heart murmur indicates problems when its nature signals that the ability of the heart to pump blood is compromised. Your veterinary surgeon will be able to identify whether a murmur is serious or not by the time and character of its occurrence within the normal heart cycle. Such murmurs may indicate a variety of problems including leakage of blood through the heart valves, thickening or narrowing of a blood vessel or even a hole in the heart wall. Generally, the severity of the murmur depends on the extent of the defect i.e. the bigger the defect the more significant the murmur will be but more exact diagnosis is available by ultrasonography available at a few veterinary clinics and all referral centres. In the most severe cases a murmur may be heard or felt without a stethoscope.

What might be the clinical signs of a horse with a murmur?

Most murmurs do not signify a problem with the horse’s heart. In the rare case that your horse does have a heart problem however, the clinical signs are related to disturbance in the blood flow through the heart and therefore the inability of the heart to pump blood efficiently to the body. Therefore if the defect is only small there may be no noticeable signs, however, a larger defect may cause a decrease in the horse’s performance and willingness to exercise. If severe enough, your horse may even refuse to exercise at all.

If you suspect your horse may have a heart problem, contact your veterinary surgeon.