We would like to see if using Carvedilol in adjunct with Ace inhibitors will increase ejection fraction of the heart under echo. All interpretation of data will be sent to Boston Children's Hospital to be reviewed, which is the primary research center in this study. There are 5 hospitals participating in this study. The population targeted are children with moderate heart failure and must be on Ace inhibitors at the time of enrollment. Our outcome after placing them on Carvedilol is to change their ejection fraction on echo. The patients will be seen every 1-2 weeks, while we will titrate their medication to a maintenance dose. Secondary outcome is to increase quality of life, exercise tolerance and decrease their symptom scores as noted on their questionnaires.