Final answer:
The most common etiology of acute aortic insufficiency is Rheumatic fever.
Step-by-step explanation:
The most common etiology of acute aortic insufficiency is Rheumatic fever. When a valve malfunctions, the flow of blood to a region will often be disrupted. The resulting inadequate flow of blood to this region will be described in general terms as an insufficiency. In the case of acute aortic insufficiency, it refers to the inadequate flow of blood through the aortic valve.