For mild cases, no treatment is needed.
For more severe cases, ACE inhibitors and diuretics are used as medical treatments. The surgical options are aortic valve repair (valvuloplasty) or replacement with a mechanical or tissue valve.
Replacement carries high risks (1 in 50 patients dies) as it is open heart surgery and also a risk the risk of blood clots and thus needs to be carefully considered, and patients need to take anti-blood clot medication afterwards.
Sources:
Medlineplus on Aortic Insufficiency
Mayo Clinic on Aortic valve regurgitation (different name for aortic insufficiency)
NHS page on aortic valve replacements