 1. Male or female children from birth through 17 years of age with chronic symptomatic CHF due to systemic ventricular systolic dysfunction who are receiving standard heart failure therapy will be eligible. Since adolescents with left ventricular dysfunction are very similar to adults with this disease, this study will focus recruitment in the prepubertal age group of children, including children from birth through Tanner Stage 3. The number of adolescents enrolled will be limited to approximately 10 of study enrollment. However, teenagers with single ventricles or morphologic right ventricles as systemic ventricles represent an important population that is unique to pediatric cardiology. The 10 limitation will only apply to teenagers who have dilated cardiomyopathies since these patients may be similar to young adults with dilated cardiomyopathies. Adolescents will be defined as Tanner Stage 4 through age 17. 