Goal: Heart rate is a factor that predicts cardiovascular diseases such as heart failure, high blood pressure, stroke and coronary artery diseases. This study examined the association between admission heart rate of STEMI[1] patients undergoing PCI[2] on the LCX[3] artery and their clinical and angiographic results. Materials and procedure: This retrospective cross-sectional study was carried out on 155 patients with acute inferior or posterior STEMI who underwent angioplasty on the LCX at the Shahid Madani Hospital of Tabriz, Iran, from 2018 to 2021. To gather data, all the files of the STEMI patients undergoing PPCI[4] on the LCX artery were identified at the Medical Records Department of the hospital, and registered in the questionnaire. Patients’ heart rate at admission was obtained from the ECGs recorded in the files. The patients were divided into three groups of under 70 beats (low), 70-100 beats (normal), and over 100 beats (high) per minute. Findings: The studied group consisted of 155 patients, including 31 ones (20%) with low heart rates, 107 ones (69%) with normal heart rates and 17 ones (11%) with high heart rates.