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