Background: Terminal QRS distortion and fragmentation (fQRS) with elevated myeloperoxidase (MPO) were linked to poor cardiovascular outcomes in acute coronary syndrome. We aimed to investigate these parameters in early prediction of coronary artery disease severity based on SYNTAX score and in-hospital adverse events in STEMI patients. Methods: A total of 215 patients with first STEMI admitted for primary PCI were included in the study. They were divided according to the admission ECG into group I with QRS distortion or fQRS, group II with combined QRS distortion and fQRS, and group III without QRS distortion or fQRS. Myeloperoxidase and troponin I levels, ST resolution ratio, left ventricular EF%, and severity of coronary artery lesions using SYNTAX risk score were measured. Results: MPO level, SYNTAX score, and in-hospital mortality were higher in group I and II and were higher in group II compared to group I. By regression analysis, QRS distortion, fQRS, and MPO > 412 ng/ml were independent predictors of both CAD severity and in-hospital mortality. DM was an independent predictor of CAD severity (OR: 2.851, P 0.012) while high SYNTAX score was an independent predictor of in-hospital mortality (OR: 6.113, P 0.001). Adding MPO level to any QRS configuration pattern increased predictive value for the detection of CAD severity that was more evident in the combined QRS distortion and fragmentation. Conclusion: Terminal QRS distortion, fragmentation, or combined QRS distortion and fragmentation have a significant value in predicting in-hospital adverse events and CAD severity as assessed by SYNTAX score in association with plasma myeloperoxidase level in STEMI patients. Combined QRS distortion and fragmentation, in spite less common, could be more helpful for early risk stratification and management.