eur ys m ▁is ▁cru cial ▁to ▁its ▁treatment . ▁A ▁thor ac ic ▁a ort a ▁greater ▁than ▁ 4 . 5   cm ▁is ▁generally ▁defined ▁as ▁an eur ys mal , ▁while ▁a ▁size ▁greater ▁than ▁ 6   cm ▁is ▁the ▁distinction ▁for ▁treatment , ▁which ▁can ▁be ▁either ▁end ov asc ular ▁or ▁surg ical , ▁with ▁the ▁former ▁reserved ▁for ▁path ology ▁at ▁the ▁desc ending ▁a ort a . ▁ ▁Ind ic ation ▁for ▁surg ery ▁may ▁depend ▁upon ▁the ▁size ▁of ▁the ▁an eur ys m . ▁A neur ys ms ▁in ▁the ▁asc ending ▁a ort a ▁may ▁require ▁surg ery ▁at ▁a ▁smaller ▁size ▁than ▁an eur ys ms ▁in ▁the ▁desc ending ▁a ort a . ▁ ▁Tre at ment ▁may ▁be ▁via ▁open ▁or ▁via ▁end ov asc ular ▁means . ▁ ▁Ep ide mi ology ▁ ▁Each ▁year ▁in ▁the ▁United ▁States , ▁some ▁ 4 5 , 0 0 0 ▁people ▁die ▁from ▁dise ases ▁of ▁the ▁a ort a ▁and ▁its ▁branches . ▁Ac ute ▁a ort ic ▁dis section , ▁a ▁life - th re aten ing ▁event ▁due ▁to ▁a ▁te ar ▁in ▁the ▁a ort ic ▁wall , ▁affect s ▁ 5 ▁to ▁ 1 0 ▁patients ▁per ▁million ▁population ▁each ▁year , ▁most ▁often ▁men ▁between ▁the ▁ages ▁of ▁ 5 0 ▁and ▁ 7 0 ; ▁of ▁those ▁that ▁occur ▁in ▁women ▁younger ▁than ▁ 4 0 , ▁nearly ▁half ▁arise ▁during ▁pre