Auscultation is the art and science of listening through a stethoscope. The range of sounds heard when auscultating the horses heart is unusually large when compared to other species. Up to 6 different normal heart sounds plus a murmur and/or click per cycle can fall within the normal range. The character and position in the cycle are important characteristics to help derive a possible diagnostic and prognostic significance. Other sounds include squeaks, and adventitial sounds. This articles discusses general principles of using a stethoscope, auscultation, and interpretation of heart sounds with an emphasis on determining the possible significance or heart murmurs and sounds.

Auscultation is one of the most useful techniques for examining the horse's heart available. Besides being quick, inexpensive, and available everywhere there is a stethoscope, it is the surest way to get a accurate minute heart rate (MHR). Besides detecting disease of the heart, MHR can also be your best indication of exercise tolerance, recovery from exercise stress, and a good measure of pain severity and/or severity of other disease processes. Auscultation can be the first localizing sign that abnormal clinical findings may be attributable to the heart. This said, it is important to realize there are very definite limitations to the interpretation of abnormal heart sounds on the horse.

There are several reasons why interpretation of abnormal heart sounds is particularly difficult in the horse. The size of the horse's heart seems to lead to the frequent production of unusual sounds, particularly split sounds, murmurs, squeaks, and clicks that do not correlate with a disease process. But, these sounds mimic early heart disease related sounds. Also mild non-progressive pathology of the horses heart may not effect athletic endeavor at all but the most intensive exercise levels. So when the examiner comes across an abnormal heart sound he is often left with the question, "What is the significance of this sound?". One further principle needs bringing forward and that is the absence of a abnormal heart sound does not rule out disease of the heart.

Keeping in mind the problems of interpretation problems, there are some "abnormal sounds" that are frequently benign and others that are frequently indicative of disease. Besides the interpretation of the heart sound you should also take into account:

• Does this sound represent a change from past examinations?
• Does this sound persist or worsen with exercise?
• Are there any clinical signs referable to heart disease?

If the answer to these questions is "no" it further increases the chance this is a benign sound.