This document provides an overview of heart failure including its definition, classification, etiology, precipitating factors, compensatory mechanisms, clinical picture, investigations, differential diagnosis, and treatment. Key points include that heart failure results from the heart's inability to pump adequately to meet metabolic demands, and can be due to problems of the left ventricle, right ventricle, or both sides. Common causes include ischemic heart disease and hypertension. The clinical picture involves manifestations of low cardiac output and congestion. Investigations include echocardiography, ECG, and cardiac catheterization. Treatment involves addressing the underlying cause, precipitants, and specific therapies for heart failure.