Q waves on a 12-lead ECG are markers of a prior myocardial infarction (MI). However, they may regress or even disappear over time, and there is no specific ECG sign of a non-Q-wave MI. Fragmented QRS complexes (fQRSs), which include various RSR' patterns, without a typical bundle-branch block are markers of altered ventricular depolarization owing to a prior myocardial scar. We postulated that the presence of an fQRS might improve the ability to detect a prior MI compared with Q waves alone by ECG.