Functional and morphologic pathology of equine aortic insufficiency.

This research is an examination of the anatomical and functional abnormalities in horses and mules suffering from aortic insufficiency, specifically in relation to distinctive murmur sounds and valve defects visible in their aortas.

Participant Selection

• The researchers selected fifteen animals – twelve horses and three mules – with symptoms of aortic insufficiency, specifically those exhibit grade II or louder prolonged diastolic murmurs.
• For comparative purposes, the study also included an additional fifteen control animals that showed no symptoms of aortic insufficiency.

Observations

• Upon examination, all mules and majority of the horses, precisely all except two, exhibited signs of aortic insufficiency. These symptoms were based on the presence of murmurs, jet lesions, and/or pathological and incompetent valve cusps.
• In all defective aortic valves, the presence of a thick fibrous band was observed. Located at the line of valvular closure and parallel to the free edge, this band resulted in the eversion, or flipping outwards, of the outermost part of the valve cusp.
• Growth of endothelial-covered villi was detected on the ventricular surface of valves with band lesions as part of the body’s natural response to injury or inflammation. There was also a fibroblastic proliferation in a rich ground substance within these villi and on the surface of the ventricularis, involving all layers of the valve.
• The existence of nodular lesions within the aortic leaflet was also reported. Being similar to nonbacterial thrombotic endocarditis in humans, it led to the proliferation of fibrocytes and subsequent production of acid mucopolysaccharide ground substance and collagen fibers. However, these nodular lesions did not contribute significantly to the observed aortic insufficiency.
• Signs of age-related deterioration, or senile degenerative changes were detected via the degeneration of elastic fibers and focal mineralization of the fibrosa.

Conclusion

• The study contributes to our understanding of aortic insufficiency in equine subjects. It aids in the identification of its functional and morphological changes, which may improve diagnostic and interventional approaches. It underlines that degenerative changes and valve deformation play critical roles in the pathogenesis of equine aortic insufficiency, while other factors such as nodular lesions seem less substantial.