The purpose of this study is to determine whether using an echocardiogram (a painless test where ultrasound is used to see your heart) while using mild electrical stimulation from your own CRT-D device to stimulate the ventricles (the lower chambers of the heart) to squeeze one slightly earlier than the other will show a sustained increase your heart's productivity (Cardiac Output (CO)), following implantation of a Cardiac Resynchronization Device (CRT-D). We believe that squeezing some parts of the heart earlier than others may make the heart a stronger pump.