Five ECG methods were analysed for their ability to predict MRI infarct mass : ( 1 ) summed STR across all infarct-related ECG leads ( STR ) ; ( 2 ) STR in the single lead with maximum baseline ST-segment elevation ( maxSTR ) ; ( 3 ) summed residual ST-segment elevation across all infarct-related leads at 60 min post intervention ( ST residual ) ; ( 4 ) maximum residual ST-segment elevation in the worst single lead at 60 min post intervention ( maxST residual ) ; ( 5 ) number of new significant Q-waves ( Qwave ) at 60 min .