Hypoplastic left heart syndrome


Hypoplastic left heart syndrome (HLHS) is a heart defect that is present from birth. In a normal heart, each side has its own function. The right-side transports oxygen-depleted blood to the lungs, while the left delivers oxygen-rich blood to the body. Hypoplastic left heart syndrome is a condition in which the left side of the heart is not sufficiently developed to pump enough blood to supply the body’s needs. As a result, the right ventricle or the lower chamber of the heart takes over the function of pumping blood to both the lungs and the rest of the body. To do this, the body relies on a blood vessel called the ductus arteriosus.

The management of hypoplastic left heart syndrome involves administering medication to prevent the closure of the ductus arteriosus, the connection between the left and right sides of the heart. Additionally, either a surgical procedure or a heart transplant is required. Fortunately, with advancements in medical care, the prognosis for infants born with this condition has improved significantly.


Newborns with hypoplastic left heart syndrome do not always show symptoms immediately. Instead, symptoms may develop within a few hours or days of birth. Among the symptoms are:

  • Cyanosis, or grayish blue discoloration of skin, lips, and nails
  • Difficulty breathing
  • Rapid heartbeat
  • Difficulty feeding
  • Chilly, sweaty hands and feet
  • Weak pulse
  • Lack of energy or drowsiness

In babies with hypoplastic left heart syndrome, the closure of the natural connections between the heart’s left and right sides (specifically the foramen ovale and ductus arteriosus) during the first few days of life can result in shock and potentially fatal outcomes.

A newborn experiencing shock may or may not be conscious, and typical symptoms include:

  • Cold, damp skin that can be pale, or bluish gray lips
  • A quick and faint pulse
  • Slow, shallow, or fast breathing
  • Dull, staring eyes

Hypoplastic left heart syndrome is usually diagnosed in babies either prenatally or shortly after birth. Nonetheless, if you observe any indications of the condition in your baby, seek medical assistance promptly. In case you suspect that your baby is experiencing shock, do not delay and contact your local emergency number immediately.


In many cases, the cause of hypoplastic left heart syndrome is unknown. However, certain genetic mutations can increase the likelihood of a baby developing hypoplastic left heart syndrome. The GJA1 and NKX2-5 genes are examples of such mutations. Additionally, infants with genetic disorders like Turner syndrome or trisomy 18 may also be at a higher risk of developing hypoplastic left heart syndrome.

Risk factors

Having a child with hypoplastic left heart syndrome increases the likelihood of having another baby with the same or a related condition, but there are no other known risk factors for this syndrome.