Background: Various prior studies have suggested that the region of a myocardial scar is associated with alteration in QRS morphology, leading to a terminal conduction delay or a fragmentation of QRS complexes (fQRS) on the 12-lead ECG. However, there were limited data regarding the incidence and fate of fragmented QRS in patients with acute ischemic myocardial injury. So, we investigate the temporal change of QRS after ST elevation myocardiac infacrtion (STEMI) and its regional correlation with infarct area by delayed enhancement of cardiac MR (DE-CMR). Methods: Seventy-five adults (57 men and 18 female: mean age 56.7짹13 yrs) presenting with STEMI were included. 12 leads standard ECG (GE, Marquette, Wis; model Mac 5500; filter range, 0.16 to 100 Hz; AC filter, 60 Hz, 25 mm/s, 10 mm/mV) at admission, 24hrs, 1 month, 9-12 months after event and electrocardiogram-gated MRI were performed. Cardiac MR was performed on a 1.5 Tesla (T) MR system (Signa Infinity Twinspeed, GE Medical Systems, Waukesha, Wisconsin) and myocardial scarring change was confirmed with delayed gadolinium (Gd) enhancement (DE)-MRI. Results: Baseline characteristics were shown in Table 1. After 24hrs after admission, 66%(50/75) developed Q wave and 74.5%(56/75) developed fQRS. All Q wave and fQRS except two fQRS were correlated with myocardial infracted area (94.3%). In contrast fQRSs showed no regression, 41.9% of Q wave were regressed after 9 month. The sensitivity, specificity and positive predictive value detecting myocardiac scar with fQRS were 76.1%, 100 % and 100%. Furthermore, old infarcted scars developed earlier than culprit lesion were detected with fQRS, not Q wave, in 5 patients. Conclusion: fQRS complex have a good correlation with myocardial scar developed after ischemic injury and was not regressed for long time. Therefore, fQRS is promising indicator of remote myocardial ischemic injury. The myocardial fibrosis presented with delayed enhancement in CMR after injury was the suggestive mechanism of fQRS formation.