Cardiac Failure
Richard E. L. Fowler MD1
1 Professor and Head of the Department of Pediatrics, Louisiana State University School of Medicine in New Orleans
Congestive heart failure is an altered state of circulatory dynamics resulting from an imbalance between the demands by the body for blood flow to meet its metabolic needs and the ability of the heart to meet those demands. The imbalance may be created in several different ways (Fig 1). The demand for cardiac output may be greatly increased in situations such as large intracardiac or extracardiac left-to-right shunts, valvular insufficiencies, hypermetabolic states, or fluid overload (Table 1). A demand for abnormally high pressure generation may be imposed by obstructive lesions of the outflow tracks of the left or right ventricles or by elevated resistance to blood flow in their attached blood vessels. An unbalanced state may also be produced by inability of the myocardium to meet normal demands when the myocardium has been damaged by inflammation (myocarditis), metabolic abnormalities (cardiac glycogenosis), fatigue or dysrhythmias (tachyarrhythmias, heart block), nutritional deficiencies (beri-beri, starvation), or toxins (diphtheria, alcohol). Still other causes of inadequate myocardial contractility are electrolyte disturbances (hyper- or hypokalemia), drugs (doxorubicin [Adriamycin]), muscular degeneration (muscular dystrophy), or coronary artery disease (congenital abnormalities, Kawasaki's disease). In each instance, the physician's task is to restore the needed equilibrium by reducing the demands upon the heart or by improving the myocardium's ability to respond.
