For IR-drop analysis, patterns that produce maximum instantaneous currents are required, whereas for electromigration purposes, patterns producing large sustained (average) currents are of interest.
fɔːɹ ˌaɪˈɑːɹdɹˈɑːp ɐnˈæləsˌɪs, pˈætɚnz ðæt pɹədˈuːs mˈæksɪməm ˌɪnstəntˈeɪniəs kˈɜːɹənts ɑːɹ ɹᵻkwˈaɪɚd, wˈɛɹæz fɔːɹ ɪlˌɛktɹoʊmɪɡɹˈeɪʃən pˈɜːpəsᵻz, pˈætɚnz pɹədˈuːsɪŋ lˈɑːɹdʒ səstˈeɪnd ˈævɹɪdʒ kˈɜːɹənts ɑːɹ ʌv ˈɪntɹɛst.