6.5 Aortic valve disease
Small nodules and fenestrations of the aortic valve cusps are common findings in normal horses. Fenestrations are usually found on the leading edge of the valve and may even be found in the fetus. Small nodules are more often found in older animals and become most common in horses over approximately seven years of age. These nodules are due to degenerative change, but frequently appear to have no effect on valve function. In some animals band-type lesions are found, and these are more often associated with signs of abnormal valve function. Nodules and bands are most frequently found on the right coronary cusp of the valve, although the left coronary cusp and the non-coronary cusp are also affected. Lesions, particularly those of a band-type, may result in valvular incompetence; however, there is no evidence that they ever result in sufficient obstruction to outflow to merit the term 'stenosis' (see section 6.5.4). Aortic regurgitation (AR) is quite common in older horses, but is occasionally found in younger animals.
6.5.2 Clinical signs and prognosis
6.5.3 Further diagnostic aids
6.5.4 Aortic stenosis