▁as ▁a ▁diameter ▁exceed ing ▁the ▁following ▁cut off : ▁ 4 . 5 ▁cm ▁in ▁the ▁United ▁States ▁ 4 . 0 ▁cm ▁in ▁South ▁Korea ▁ ▁A ▁diameter ▁of ▁ 3 . 5 ▁cm ▁is ▁generally ▁considered ▁dil ated . ▁However , ▁average ▁values ▁vary ▁with ▁age ▁and ▁size ▁of ▁the ▁reference ▁population , ▁as ▁well ▁as ▁different ▁segments ▁of ▁the ▁a ort a . ▁ ▁Screen ing ▁ ▁Gu idel ines ▁were ▁issued ▁in ▁March ▁ 2 0 1 0 ▁for ▁early ▁detection ▁of ▁thor ac ic ▁a ort ic ▁disease , ▁by ▁the ▁American ▁College ▁of ▁Card i ology , ▁the ▁American ▁Heart ▁Association , ▁and ▁other ▁groups . ▁Among ▁the ▁recommend ations : ▁▁ ▁First - deg ree ▁relatives ▁of ▁people ▁with ▁thor ac ic ▁a ort ic ▁an eur ys m ▁or ▁dis section ▁should ▁have ▁a ort ic ▁imag ing ▁to ▁identify ▁asympt om atic ▁disease . ▁ ▁People ▁with ▁sympt oms ▁suggest ive ▁of ▁thor ac ic ▁a ort ic ▁dis section ▁should ▁be ▁rout in ely ▁evaluated ▁" to ▁establish ▁a ▁pre test ▁risk ▁of ▁disease ▁that ▁can ▁then ▁be ▁used ▁to ▁guide ▁di agnostic ▁dec isions ." ▁ ▁People ▁diagn osed ▁with ▁Mar fan ▁synd rome ▁should ▁immediately ▁have ▁an ▁e ch oc ardi ogram ▁to ▁measure ▁the ▁a ort a , ▁and ▁followed ▁up ▁ 6 ▁months ▁later ▁to ▁check ▁for ▁a ort ic ▁en larg ement . ▁ ▁Tre at ment ▁ ▁The ▁size ▁cut ▁off ▁for ▁a ort ic ▁an