Aortic Valve Insufficiency in a Horse

Figure 1

Figure 2A and 2B

 The image in Figure 1 is of a horse's heart taken via trans-thoracic ultrasound. Specifically, the ultrasound probe is centered on the aortic valve. The horse presented for a prepurchase exam and a loud murmur was detected during the physical exam. There was no history of exercise intolerance nor was there evidence of heart failure during the physical exam. The murmur was best described as diastolic (during the filling phase) and included a high musical pitch at the end of the murmur. During the cardiac ultrasound exam, color flow doppler was imaged (Figure 1) to determine the flow of blood across the aortic valve. Normally, the color of the blood flow will be blue or red depending on whether the blood is moving towards or away from the ultrasound probe. When there is a "leaky" valve or a valve that is "insufficient" the color of the blood flow is bright yellow, white or orange. This color flow pattern is consistent with turbulence across the valve due to blood traveling "backwards" through the valve. In Figure 2, the red arrow identifies the normal direction of blood flow through the aortic valve. In Figure 3 a small white line is highlighted by the yellow arrows. This white line corresponds to one of the 3 valves that make up the aortic valve. In this horse, the aortic valve is thickened resulting in a "leaky" valve. The "leakiness" can be noted in Figure 4 as bright yellow and white blood flow in the opposite direction of normal blood flow across the aortic valve. The thickened valve likely vibrates as the jet of blood flows "backwards" causing the musical heart murmur!  Aortic insufficiency is the most common type of heart murmurs in horses and is often benign during the early phases of development. However, if the horse lives long enough, the aortic insufficiency can lead to heart failure in the horse. As such, heart murmurs in horses should not be dismissed as "normal" and inconsequential but should be carefully documented via ultrasound exam!!

Figure 3

Figure 4