Abstract Objective: The purpose of this study is to investigate the relationship between microvascular dysfunction and the presence of fragmented QRS(f-QRS) in patients with acute inferior myocardial infarction(MI) who underwent primary percutaneous coronary intervention(PPCI). Methodology:274 consecutive patients with a mean age of 56.8 ± 9.8 who met the inclusion criteria were enrolled; patients with TIMI 2-3 flow after PPCI were divided into two groups according to the myocardial blush grade (MBG) 0-1 and MBG 2-3. The f-QRS includes different morphologies of the QRS and includes an additional R wave (R ’) or notching at the lowest end of the S wave in two adjacent leads releasing the infarct area. ECG records were taken to assess f-QRS and ST segment resolution was assessed in the first hour after the procedure. During angiographic examination, myocardial blush grade (MBG) and TIMI flow were measured in the right coronary artery due to post-procedure infarction. Results:The patients were divided into two groups as MBG 0-1 and MBG 2-3. In general, the median age was 56.8 ± 9.8,and 49 patients(17.9%) were women. Among all study patients, f-QRS count was 36(13.1%). In this study, 62 and 212 patients had MBG 0-1 and MBG 2-3, respectively. f-QRS was detected in 23(21.7%) patients in the MBG 0-1 group and 13(10.7%) patients in the MBG 2-3 group. In multivariate logistic regression, f-QRS [OR: 2.3(1.13-5.06),p = 0.027],ST segment resolution at first hour [OR: 0.62 (0.39-0.90),p = 0.04], and TIMI frame number [OR: 1.05(1.01-1.09),p = 0.004] were found to be associated with MBG 0-1. Conclusion:Our study showed that the presence of f-QRS after PPCI was associated with microvascular dysfunction in patients with inferior MI who underwent successful PPCI.F-QRS, a simple and inexpensive parameter, can be used to assess microvascular dysfunction in MI patients who underwent PPCI. Keywords:microvascular dysfunction,fragmented QRS,myocardial infarction