The objective of this study was to study the integrated score of ST-segment resolution (ISSTE) and in-hospital death in patients undergoing primary percutaneous intervention (pPCI) for ST-segment elevation myocardial infarction (STEMI). Material and Methods: This prospective study included 586 consecutive patients admitted with STEMI to the Cardiol- ogy Clinic of the County Emergency Clinical Hospital of Tîrgu Mureș, between January 1st, 2013 and December 31, 2014, who underwent pPCI in less than twelve hours after the onset of symptoms. Clinical and demographic data were analyzed in 539 (91.9%) survivors (Group 1) and 47 (8.1%) nonsurvivors (Group 2). The Integrated Score of ST elevation (ISSTE) was calculated by summing the amplitude of the ST segment elevation in all the 12 leads, before and at 2 hours after revascularization. Results: The ISSTE score calculated at baseline, im- mediately before the primary percutaneous coronary intervention, was significantly higher in Group 2 as compared to Group 1 (13.9 ± 1.2 vs. 11.0 ± 0.2, p = 0.026). At the same time, the ISSTE score calculated at 2 hours after the coronary intervention was significantly higher for patients in Group 2 (7.36 ± 1.12 vs. 2.9 ± 0.1, p <0.0001). Analysis of the dynamics of the ISSTE score indicated that patients who survived presented a more expressed reduction in the ISSTE score following pPCI, as compared to those who subsequently died (73.5% reduction in Group 1 compared to 47.2% reduction in Group 2, p <0.0001). In-hospital mortality was significantly higher in the group of patients with >50% reduction in the ISSTE score. The in-hospital death rate was 5.4% in patients with >50% reduction in the ISSTE score, compared to 19.4% for those who presented less than 50% reduction in the ISSTE score following pPCI (p <0.0001). The rate of successful reperfusion rate, expressed by the reduction in ISSTE score, was 83.8% in Group 1, compared to 55.3% in Group 2 (p <0.0001), indicating that the absence of an effi- cient reperfusion after pPCI is associated with a higher mortality in STEMI patients, and could be evaluated using regression of the ISSTE score, which proved to be directly associated with mortality. Conclusion: The ISSTE score is shown to be an effective ECG-derived marker of myocardial damage in STEMI patients. A high ISSTE score is associated with higher mortal- ity, while a reduction in the ISSTE score after pPCI may indicate an efficient reperfusion and a decrease in mortality in the first days after infarction.