This is a single-center, non-randomized study.The study staff will use the InSpectraTM tissue oxygen saturation (StO2) monitor manufactured by Hutchinson Technology to measure baseline StO2 levels after applying the noninvasive probe to the thenar eminence. After a stable reading is obtained, a blood pressure cuff will be inflated 40 mmHg above the obtained systolic pressure and the rate of desaturation (Rdes; % × sec-1) will be recorded. After 3 minutes or once the StO2 level comes to zero (whichever is earlier), the cuff pressure will be released and the rate of reperfusion (Rres; % × sec-1) will be measured. The investigators hypothesize that heart failure in children causes a baseline lower thenar tissue oxygen saturation (StO2), a faster rate of desaturation (Rdes) and a prolonged rate of reperfusion (Rres). The investigators also hypothesize that these changes will correlate with the severity of heart failure. The results of this study will provide groundwork for studies looking at correlation of therapy modification based on the combination thenar StO2 and clinical presentation.