Babies born with hypoplastic left heart syndrome usually are seriously ill soon after birth. Symptoms include: 
Grayish-blue color of the lips and gums (cyanosis)
Rapid, difficult breathing
Poor feeding
Cold hands and feet
Weak pulse
Being unusually drowsy or inactive
 If the natural connections between the heart's left and right sides (foramen ovale and ductus arteriosus) are allowed to close in the first few days of life in babies with hypoplastic left heart syndrome, they can go into shock and possibly die. Signs of shock include: 
Cool, clammy skin that can be pale or lips that can be bluish-gray
A weak and rapid pulse
Breathing that may be slow and shallow or very rapid
Dull eyes that seem to stare
 A baby in shock might be conscious or unconscious.