What is Aortic Insufficiency?
A dysfunctional aortic valve often goes unnoticed. It is a condition that commonly affects older horses, whose performance expectations are already lowered. The cause of the dysfunction could be a degenerative condition, or an infection in the valve. Problems with the chordae tendinae, or the connective tissue bands that hold the valve shut to prevent backflow, could also be at fault. The turbulent flow of blood that results can cause a murmur, the presence of which is a clear indication of a problem. A murmur caused by the aortic valve is present during diastole, or after the dub sound, and is louder on the left side.
Aortic insufficiency, also called aortic regurgitation, is a type of degenerative valve disease that involves the aortic valve. When this essential valve fails to properly close, a leak occurs that causes the blood to flow in the opposite direction than it should. This, in turn, causes an overload in the volume of blood in the left ventricle, which can enlarge over time. While mild cases can produce symptoms such as tiring easily and poor performance, more severe leaks can cause death from congestive heart failure. It is important to get your horse’s heart evaluated, as treatments can slow the progression of the disease.
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Symptoms of Aortic Insufficiency in Horses
Symptoms of an aortic insufficiency include:
- Poor performance
- Increased heart rate
- Swollen abdomen
- Tires more easily
- Increased breathing rate
- Presence of heart murmurs that are louder on the left side
- Congestive heart failure
Causes of Aortic Insufficiency in Horses
Causes of an aortic insufficiency in horses relate to conditions that affect the performance of the aortic valve. These can include:
- Degenerative valve thickening
- Aortic valve prolapse
- Buckling of the leaflets, or the flaps that make up the valve
- Valve leaﬂet tearing
- Infective endocarditis in the valve leaflets
- Progressive scarring of valve margins
- Infections on or near the valves
- Ruptured chordae tendinae, or the connective bands of tissue that help the valve to seal shut
- Valvulitis, or inflammation on the valves
- Fenestrations, or surgical openings created in bone
- Aortic root disease
- Congenital malformations
Diagnosis of Aortic Insufficiency in Horses
A diagnosis of aortic insufficiency is based on medical history, symptoms present, and the results of a physical exam, which includes a more thorough examination of the heart. The presence of a heart murmur can indicate a leaking valve. A murmur in the aortic valve is louder on the left side, and is described as a cooing dove or dive bomber sound. Lung sounds may also be evaluated. Your veterinarian may take your horse’s blood pressure, noting the presence of a bounding pulse which can be an indication of this condition. An ECG may also be used to look at the electrical flow patterns in your horse’s heart cycle.
Echocardiography is an ultrasound of the heart, the results of which can lead to a definitive diagnosis. This test can evaluate valve structures, track movement of the ventricles, reveal the speed, direction and volume of blood flow, and analyze the severity of a valve leak. They can also show abnormalities, such as lesions, or an enlargement of the left ventricle, which is a common side effect of aortic insufficiency.
Treatment of Aortic Insufficiency in Horses
In mild cases, your veterinarian will not prescribe treatment, but instead may schedule repeated visits twice a year to evaluate your horse’s heart. A physical exam and echocardiography are used to monitor the progression of the condition in your horse over time. Exercise can often help with mild to moderate cases, and should be tailored to your individual horse, taking into account his age, fitness level, and severity of cardiac dysfunction.
In more severe cases, your vet may prescribe daily medications to delay the progression of the condition and reduce symptoms. These could include angiotensin converting enzyme (ACE) inhibitors, such as Enalapril or furosemide.
Recovery of Aortic Insufficiency in Horses
If your horse suffers from a mild case of aortic insufficiency, you may only need to provide sufficient exercise and have his heart examined twice a year to monitor his condition. Recovery is good, in that the condition may not affect your horse’s daily life significantly, but it can worsen with age. If your horse’s aortic insufficiency is more severe, you may be prescribed daily medications to administer to delay the progression of the disease. This may improve symptoms, but severe cases carry a poor prognosis regardless.