Background: Diagnosing the cause of left ventricular systolic dysfunction (LVSD) is key in heart failure management, but the use of coronary angiography varies due to limited evidence of its benefits. Aim: The present study aims to evaluate the diagnostic effectiveness of coronary angiography in patients with LVSD without a prior history of ischemic heart disease. Methods: This retrospective cohort study analyzed adult patients with LVSD (EF < 50%) who underwent coronary angiography between March 2022 and July 2024. Results: Of the 53 participants, 39 had non-significant coronary stenosis and 14 had significant stenosis. The mean age was 52.3 years, with no significant age difference between groups (p = 0.309). Smoking (p = 0.003) and diabetes mellitus (p < 0.001) were significantly more common in the significant stenosis group, while no differences were observed for hypertension (p = 0.853) or history of heart failure (p = 0.694). ECG findings showed no significant differences, but the significant stenosis group had a significantly lower left ventricular ejection fraction (p < 0.01), indicating reduced heart function. Conclusion: The present study concludes that in patients with left ventricular systolic dysfunction, the risk stratification of coronary disease can be established using information from the clinical history, electrocardiogram, and echocardiography.