Acute heart failure (HF) is the most common diagnosis at discharge in patients aged > 65 years. It carries a dismal prognosis with a high in-hospital mortality rate and very high post-discharge mortality and rehospitalization rates. It is a complex clinical syndrome that is challenging to define as it may vary widely with respect to underlying pathophysiological mechanisms and clinical presentations. Different clinical scenarios have prognostic significance and may influence therapeutic options. Amongst the main clinical presentations, we may include the following: de novo HF vs acutely decompensated chronic HF, HF caused, and/or worsened, by myocardial ischemia, acute HF with low, normal, or high systolic blood pressure, acute HF caused by hydrosaline retention or fluid redistribution to the lungs, acute HF with comorbidities (diabetes, anemia, renal insufficiency, etc.). Different pathophysiological mechanisms and clinical presentations may coexist in the same patient. Identification and, whenever possible, treatment of underlying pathophyisiological mechanisms should be a primary objective of acute HF management.