Pathophysiology of heart failure.

Heart failure, a major contributor to cardiovascular disease morbidity and mortality, is newly diagnosed in approximately 400,000 patients each year, and is particularly prevalent in individuals over age 65 years. Average mortality rates 5 years after diagnosis are 45-60%, and may be as high as 50% after 1 year for those with New York Heart Association class IV heart disease. Heart failure occurs when myocardial muscle dysfunction prevents the heart from pumping enough blood at normal cardiac pressures to meet the metabolic needs of the body, especially during exercise, and compensatory hemodynamic and neurohormonal mechanisms are overwhelmed or maladaptive. Pathologic classifications are broadly based on the presence of systolic (dilated cardiomyopathy) or diastolic (hypertrophic or restrictive cardiomyopathies) dysfunction. The etiologies of heart failure may include inadequate coronary blood flow, pressure or volume overload, cardiomyopathy, or pericardial disease. Coronary artery disease, idiopathic dilated cardiomyopathy, and hypertension are the most frequent causes, and certain drugs may also worsen myocardial function. When contractility is reduced, stroke volume and cardiac output are decreased, and alterations in the kidneys may induce fluid retention to compensate for the perceived low output and reduced circulating blood volume. Fluid retention in turn causes preload or filling pressure to increase and symptoms of pulmonary congestion to emerge. Depressed contractility also results in a reduction in blood pressure, leading to compensatory neurohormonal activation and vasoconstriction, which significantly elevate afterload and further reduce stroke volume. The overall approach to heart failure includes defining the etiology, identifying precipitant factors, and assessing the severity of myocardial dysfunction and clinical symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)