Echocardiography remains the cornerstone of non-invasive assessment of left ventricular (LV) systolic function, providing critical insights into cardiac function, the progression of cardiovascular disease, and therapeutic decision-making. LV systolic function LV systolic function is affected by preload, afterload, and myocardial contractility. Indeed, systolic function has a complex mechanism, including contraction of the helical arrangement of the LV myocardial fibers. The ejection fraction (EF) is the most widely used measure and popular method in evaluating left ventricular (LV) systolic function. It is considered a critical prognostic factor in all types of heart diseases. Precise evaluation of LV volume and systolic function is necessary for defining the optimal timing of surgery in patients with valvular heart diseases such as severe mitral regurgitation and aortic regurgitation. This section will provide a comprehensive overview of echocardiographic parameters for assessing LV systolic function, highlight the diagnostic features of systolic dysfunction, and discuss the application of echocardiography in recognizing complications associated with cardiac dysfunction and cardiac dyssynchrony.