Introduction. The ejection fraction (EF) is the volumetric fraction of blood ejected from a ventricle of the heart with each heartbeat. EF is used as a measure of the pumping efficiency of the heart. The systemic circuit is provided by the left ventricle, thus left ventricular ejection fraction (LVEF) is the main index the body’s systemic circulation. By today’s standards, LVEF is used as an important determinant of the severity of systolic heart failure (HF). In many studies, LVEF was proposed as a predictor in patients’ outcome presenting cardiac disease.  Aim of the study. It was a performed a literature review in order to highlight the significance of the LVEF in cardiac disease prognosis outcome.  Materials and methods. There were used “PubMed MEDLINE” database to select relevant full-text original articles published from 2013 till 2018, using a search formula “ejection fraction predictor mortality”, non-human studies, as well as review articles were excluded. According to research criteria, there were retrieved 36 full-text, clinical trial articles, published in the last 5 years.  Results. Several studies identified LVEF as the most prominent independent predictor of morbidity and mortality in both acute and chronic HF patients. Acute heart failure (AHF) is one of the most important cardiovascular syndromes associated with high cardiovascular morbidity, and is the major cause of admission in emergency departments worldwide. AHF is an increasing cause of admission in emergency departments worldwide and in almost half of patients the LVEF is moderately or severely reduced ( < 40%). Since AHF is a very heterogeneous condition, it is important to identify clinical and laboratory parameters useful for risk stratification of these populations. LVEF may be one of the most convenient, since it is widely measured, easily interpreted, and inexpensive. This applies mainly to patients with reduced LVEF, while the interactions between diabetes and HF with preserved LVEF are less known.  Conclusions. On one side, studies have shown that LVEF is an independent predictor in both acute and chronic HF patients. On the other side, patients with diabetes and HF, as well as those with non-ST segment elevation myocardial infarction after revascularization, the reduced and preserved LVEF have a major impact which are less known and require additional research.