Background: The instantaneous wave-free ratio (iFR) is non-hyperemic pressure-derived indices of the severity of stenosis. The index has been tested against fractional flow reserve (FFR) in small trials, and the two measures have been found to have similar diagnostic accuracy. However, studies of clinical outcomes associated with the use of iFR are lacking. Objectives: To improve the outcomes of percutaneous coronary intervention (PCI) in patients presenting with ST segment elevation myocardial infarction (STEMI) and have multivessel coronary artery disease (CAD) through using a new technology of iFR in STEMI patients. Subjects and methods: The present prospective cohort study was conducted by cooperation between Zagazig University Hospitals, Egypt and Chest Disease Hospital, Kuwait. During the period from April 2019 to April 2020. It included 188 patients presented with acute myocardial infarction (STEMI). Patients were divided into 2 groups each one enrolled 94 patients.  Group I (iFR technique) and Group II (FFR technique), both were used to guide the decision as to whether percutaneous revascularization was appropriate. Results: There was no statistically significant difference regarding lesion characteristics assessed among studied patients. 90.4% of IFR group were not suffering from chest discomfort during the procedure versus 29.8% of FFR group with a high statistically significant difference among both groups. Four patients (4.3%) out of total number of the first group had sustained non-fatal MI, however only three cases (3.2%) had non-fatal MI, the calculated p value was 0.71. Conclusion: iFR-guided revascularization strategy was non-inferior to an FFR-guided revascularization strategy with respect to the rate of major adverse cardiac outcomes and was associated with less chest discomfort.