Background: Left ventricular systolic dysfunction (LVSD) and diabetes mellitus (DM) usually coexist, which raises patient morbidity and mortality. It is crucial to determine how isolated cases of a significant proximal stenosis of the left anterior descending artery in diabetic patients are affected by changes in the left ventricular function assessed by echocardiography after percutaneous coronary stenting. Objective: This study aimed to compare the early detection of changes in left ventricular systolic and diastolic performance in diabetic and non-diabetic patients using conventional and 2D speckle tracking echocardiography following successful percutaneous coronary intervention (PCI) with drug-eluting stenting of isolated stenosis of the proximal left anterior descending (LAD) artery. Patients and methods: A prospective cross-sectional study was conducted on 82 patients presenting with chest discomfort and myocardial ischemia at Al-Ahrar Teaching Hospital and Zagazig University Hospitals. Patients were categorized into two groups based on the occurrence of major adverse cardiovascular events (MACE) following percutaneous coronary intervention (PCI): Group I (MACE occurred) and Group II (MACE did not occur), stratified by diabetes status. All participants underwent electrocardiography (ECG) and echocardiography. Results: Pre-global longitudinal strain (GLS) and Delta GLS are significant predictor for MACE in diabetic and non-diabetic patients in univariate and multivariate logistic regression analysis. Conclusion: Patients with ischemic heart disease who had impaired systolic function improved significantly in diastolic dysfunction and all diastolic filling pattern measures after PCI.