By Harry Werner, VMD, WEVA Board Member

A prospective buyer had visited and ridden a 5-year-old Quarter Horse gelding at a reputable sales barn several times. The horse, which the buyers intended to use as a children’s hunter, seemed normal in all respects and rode well for the buyer’s child. So the buyers scheduled a prepurchase examination.

When the veterinarian arrived for the exam, he began with an assessment of the horse’s heart, lungs, and eyes in the quiet of the horse’s stall, something most veterinarians do before proceeding. In this case, however, the result was a prompt discontinuance of the rest of the examination. Upon auscultation (listening with a stethoscope) of the chest, the veterinarian heard a loud murmur over all origins of heart sounds and on both sides of the chest. The murmur completely filled the systolic phase (ventricular contraction, when the blood is ejected out of the heart and into the circulatory system) of the cardiac cycle and was strongly suggestive of a serious congenital heart defect.

The veterinarian suspected this Quarter Horse had a ventricular septal defect, a birth defect in which the horse has a hole in the inner wall of the heart. This wall, or septum, separates the right and left halves of the heart and prevents the mixing of venous (unoxygenated) blood with arterial (oxygenated) blood. The septal defect prevents this separation, causing the heart to work harder than normal and ultimately fail. Cardiac failure in this horse could come suddenly as a heart attacklike event or gradually as congestive heart failure.

The veterinarian eventually confirm