The chapter provides a comprehensive overview of the clinical presentation, diagnosis, triggers, and management of acute decompensated heart failure (ADHF), a major cause of hospitalization, especially among those over 65. Key symptoms include shortness of breath, nocturnal cough, and leg swelling, with diagnostic tools such as chest X-rays and EKGs used to assess conditions like pulmonary edema and heart arrhythmias. It discusses various heart failure types categorized by ejection fraction, and highlights common precipitants of ADHF such as hypertension, arrhythmias, and acute coronary syndrome. The chapter emphasizes the importance of a thorough clinical approach, including the ABCDE assessment for unstable patients, and suggests a detailed workup including tests like BNP and ECHO. Treatment strategies focus on diuretics, vasodilators, and supportive care, alongside addressing underlying factors like hypertension and arrhythmias. The chapter also explores specific scenarios and alternative treatments, offering a nuanced view of heart failure management.