Aims Patients with heart failure (HF) are typically designated as having reduced, mid-range, or preserved ejection fraction (EF) (HFrEF, HFmrEF, or HFpEF, respectively) because of the importance of left ventricular EF (LVEF) on therapeutic decisions and prognosis. However, such designations are not necessarily static, as there are many transitions among the three HF phenotypes during follow-up. This prospective longitudinal cohort study sought to examine the HF transitions over time and their clinical characteristics, prognosis, and response to medical therapy. Methods and results We identified 1920 patients from a prospective cohort with a primary diagnosis of HF between 1 January 2007 and 31 December 2012. The enrolled HF patients were re-classified into three groups on the basis of baseline and 1 year follow-up echocardiography: HF with improved EF (HFiEF), HF with deteriorated EF (HFdEF), and HF with unchanged EF (HFuEF). The primary outcome was 5 year all-cause mortality. According to 1 year follow-up echocardiography, 490 (25.5%) were diagnosed as HFiEF, 179 (9.3%) as HFdEF, and 1251 (65.2%) as HFuEF. Ischaemic heart disease was an independent predictor of HFdEF, and beta-blocker prescription was an independent predictor of HFiEF. During the 5 year follow-up, patients with HFdEF had higher mortality, whereas patients with HFiEF had lower mortality. After adjustment, HFiEF, compared with HFuEF, was associated with a 62.1% decreased risk for mortality. Finally, the use of beta-blockers was associated with improved prognosis of patients with HFiEF and HFuEF. Conclusions In this cohort of patients with HF, LVEF is a dynamic factor related to coexisting conditions and drug therapy. HFiEF and HFdEF are distinct HF phenotypes with different clinical outcomes than other phenotypes.