This chapter discusses the diagnosis, evaluation and management of acute decompensated heart failure (ADHF). Left-sided heart failure classically presents with dyspnea, usually related to pulmonary vascular congestion. Patients with severe ADHF present with respiratory distress and impending respiratory failure. The associated symptoms may include frothy oral secretions, diaphoresis, and hypoxia. Patients may also have other symptoms related to poor cardiac output and poor perfusion such as chest pain and altered mental status. Patients may be hypertensive or hypotensive depending on the etiology of symptoms and hypotension can be indicative of cardiogenic shock and is particularly concerning. Important elements of history include past history of cardiac dysfunction and potential causes of new cardiac dysfunction. When approaching a patient with ADHF, one must be sure to address any underlying cause while simultaneously managing the physiological derangements. Patients who become hypoxic, lethargic, or more confused despite noninvasive positive-pressure ventilation (NPPV) should be intubated.