What is an extension on the aortic valve?

Aortic valve: You need to revise your question and check what it is you'd like to know. To the best of my knowledge, there is no such thing. You can have a valvular vegetation, bicuspid valve, valvular stenosis, insufficiency etc...But no extension. Please specify and i'd be delighted to answer.

Vegetation? : I'm assuming you mean a pathological extension? It's a vegetation and is due to infection.

Vegetation: Lambls excrescence or papillary fiboelatoma of which only excrescence is benign.