6.10.2 Sinus of Valsalva aneurysm
An aneurysm of the sinus of Valsalva is an uncommon condition which may be found in association with a murmur of aortic regurgitation or may be identified incidentally on echocardiography or PM. The aetiology of the aneurysm is unclear. Usually the right coronary sinus is involved and, on echocardiography, this may appear as a defect in the junction between the aortic root at the base of the IVS and the junction of the RV and RA. This may at first resemble a VSD; however, the defect is more dorsally situated and there is no flow through it unless rupture has occurred.
The lesion is a very significant finding because it is possible that the aneurysm may rupture at any time, usually resulting in sudden death. Horses with this condition should be regarded as unsafe to ride for this reason.