Heart failure can develop in young babies usually for 1 of 2 reasons.  Either there is a congenital problem that causes a defect in the heart itself or in the blood vessels leading to the heart.  This can cause mixing of the blood that has high oxygen content, which should be used to fuel the rest of the body and de-oxygenated blood, blood that already unloaded its oxygen to the body.  The other cause can be failure of the heart muscle due to weakness from infection, medication, or a handful of other medical conditions such as hyperthyroidism or malnutrition.  If you think that your child is at risk, speak to your pediatrician and pursue a pediatric cardiologist.