Physiologic Correlates of Congestive Heart Failure

Typically, most cases of congestive heart failure in children are caused by afterload increases in the pressure dynamics of one or both chambers of the heart. In these conditions, pressure builds in one chamber of the heart due to an obstructive lesion in the outflow tract of the affected chamber. Several of the more common entities early in the first weeks of life are the left ventricular outflow obstruction syndromes, followed by congenital aortic stenosis and moderate-to-severe coarctation of the aorta. With these lesions, the systemic circulation has inadequate perfusion, and renal flow is diminished. The combination of increased fluid retention and chamber dilatation results in cardiac failure. Treatment of afterload increases is aimed at vasodilatation with either specific load-altering medications, such as nitroprusside or nitroglycerin, or the use of furosemide, which has both a diuretic effect and a vasodilatory effect. Correction of the mechanical obstruction is viewed as the ideal solution.14

Less often, congestive heart failure can be related to increases in preload representing an overall volume overload without obstructive pressure consequences. Typical entities include large VSDs, and persistent patent ductus arteriosus in premature infants. Anemias of different etiologies should be considered, especially iron deficiency anemia in small cow-milk-fed infants. Sickle cell anemia and thalassemia variants should also be considered. In the former group of conditions, decreasing the vascular volume with diuretics is beneficial. In addition, the use of digoxin may be beneficial prior to surgical repair. In the latter cases, transfusion is warranted along with judicious use of fluid restriction and diuresis.

Poor contractility is not usually considered a major cause of congestive heart failure in small infants, because the ventricular walls are still relatively noncompliant. In older pediatric patients, though, poor contractility becomes an issue. Kawasaki syndrome, idiopathic endocardial fibroelastosis, pulmonary hypertension associated with Eisenmenger syndrome, and toxic-metabolic causes should be considered in adolescent patients with congestive heart failure. Less frequent inflammatory causes include myocarditis, constrictive pericarditis, and collagen vascular diseases. Treatment is geared toward increasing contractility with dobutamine or digoxin. 15

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