Heart failure is a clinical syndrome characterized by impaired structure and/or function of the heart, leading to dyspnea and fatigue at rest or with exertion. The pathophysiology of heart failure is complex, and there is no single lesion. Any form of heart disease can lead to heart failure. Most heart failure can be explained by well-recognized etiologic factors, though ostensibly healthy patients may harbor risk factors for the later development of heart failure. A fundamental response to myocardial injury or altered loading conditions includes "remodeling" of the heart, so that the size, shape, and function of the affected chamber is grossly distorted. This is accompanied by a constellation of biologic changes, best recognized in advanced cases of heart failure. These multiple alterations may be primary or secondary events but, nonetheless, add importantly to the morbidity and mortality of the patients. More emphasis should be placed on recognition and correction of risk factors related to the development of heart failure.