Hypoplastic left heart syndrome is a rare and complex heart condition where the left side of a baby’s heart doesn’t develop properly before birth, requiring urgent medical intervention and a carefully planned series of surgeries to help the child survive and grow.

How Treatment Helps Children with an Underdeveloped Heart

When a baby is born with hypoplastic left heart syndrome, the goal of treatment is not to cure the condition but to help the child’s heart work well enough to support life. The left side of the heart, which normally pumps oxygen-rich blood to the body, is too small to do its job. Without treatment, this condition is fatal within the first days or weeks of life. However, thanks to advances in medicine and surgery over the past few decades, many children with this condition can now survive into adulthood and lead meaningful lives.^[1][6]

Treatment for hypoplastic left heart syndrome depends on several factors, including the baby’s overall health at birth, the specific structures of the heart that are affected, and whether the baby has other medical conditions. Some babies are born premature or with low birth weight, which makes them more fragile and requires extra care before surgery can be safely performed. The treatment approach is highly individualized because no two babies with this condition are exactly alike.^[4][7]

The standard approach involves a series of three major heart surgeries performed over the first few years of a child’s life. These surgeries do not repair the heart to make it normal. Instead, they redirect blood flow so that the right side of the heart takes over the job of pumping blood to both the lungs and the body. This is called single-ventricle palliation, meaning the heart will function with only one working pumping chamber instead of two.^[6][10]

In addition to surgery, babies with hypoplastic left heart syndrome need medications and close monitoring before, between, and after their operations. The medical team works to keep the baby stable, manage symptoms like difficulty breathing or poor feeding, and prevent complications such as shock or organ damage. Some children may eventually need a heart transplant if their heart cannot keep up with the demands of their growing body.^[10][17]

Standard Treatment: Medicines and Staged Surgeries

As soon as a baby with hypoplastic left heart syndrome is born, doctors begin treatment with a medicine called alprostadil, also known by the brand name Prostin VR Pediatric. This drug is critically important because it keeps a blood vessel called the ductus arteriosus open. All babies have this vessel before birth, but it usually closes within a few days after delivery. In babies with this heart condition, the ductus arteriosus must stay open to allow blood to reach the body. Without this medicine, the baby’s oxygen levels drop dangerously, and vital organs can fail.^[10][19]

Alprostadil is given through an intravenous line, meaning it is delivered directly into a vein. The baby must stay in the hospital while receiving this medication, often in a neonatal intensive care unit, where specialists can monitor the heart, breathing, and oxygen levels closely. During this time, doctors also perform detailed tests like echocardiograms, which use sound waves to create pictures of the heart, to plan the best surgical approach.^[10][19]

The first surgery, called the Norwood procedure, is usually performed within the first week of life. This operation is complex and involves reconstructing parts of the heart and blood vessels. Surgeons create a new pathway for blood to travel from the heart to the body, using the right ventricle to do the work that the underdeveloped left ventricle cannot. They also place a small tube, called a shunt, to ensure blood continues to flow to the lungs. The Norwood procedure typically requires the baby to be on a heart-lung machine, which temporarily takes over the work of the heart and lungs during surgery.^[6][13]

Recovery from the Norwood procedure is challenging. Babies spend several weeks in the hospital and may face complications such as fluid buildup, irregular heart rhythms, or infections. Parents and medical teams work together to manage feeding, breathing support, and medications to help the baby grow stronger before the next surgery.^[13]

The second surgery, known as the Glenn procedure or bidirectional Glenn, is usually done when the baby is between three and six months old. By this time, the baby has grown and can better tolerate another operation. During the Glenn procedure, surgeons connect one of the large veins that carries blood from the upper body directly to the blood vessels leading to the lungs. This reduces the workload on the right ventricle, allowing it to focus on pumping blood to the body. The shunt placed during the Norwood procedure is removed during this surgery.^[6][13]

The third and final surgery in the series is the Fontan procedure, typically performed when the child is between two and five years old. This operation completes the redirection of blood flow. Surgeons connect the remaining large vein, which brings blood from the lower body, directly to the lung blood vessels. After the Fontan procedure, all blood returning from the body goes directly to the lungs without being pumped by the heart. The right ventricle then only has to pump oxygen-rich blood to the body. This setup is not normal, but it allows children to live and grow.^[6][13]

In some cases, doctors may recommend a heart transplant as an alternative to the three-stage surgery approach. A heart transplant involves removing the child’s underdeveloped heart and replacing it with a healthy donor heart from someone who has died. This option may be chosen if the baby is too sick for surgery, if the surgeries are not successful, or if the heart fails later in life. However, heart transplants come with their own challenges, including the need for lifelong medications to prevent the body from rejecting the new heart, the risk of infections, and the limited availability of donor hearts.^[10][19]

Throughout childhood and into adulthood, people with hypoplastic left heart syndrome take various medications to support heart function and prevent complications. These may include medicines to reduce fluid buildup, control blood pressure, prevent blood clots, or manage irregular heart rhythms. The specific medications and their duration vary depending on each person’s needs.^[17]

Possible side effects of the surgeries and long-term complications include problems with blood flow to the lungs, liver disease, a condition called protein-losing enteropathy where the intestines lose too much protein, developmental delays, and reduced exercise capacity. Regular checkups, imaging tests, and blood work help doctors catch and treat these issues early.^[6][17]

Treatment in Clinical Trials: New Approaches Being Tested

Researchers around the world are working to find better ways to treat hypoplastic left heart syndrome, especially for babies who are at the highest risk and may not survive the standard surgeries. One approach being explored is the hybrid procedure, which is a less invasive alternative to the traditional Norwood operation. The hybrid procedure is especially helpful for babies who are very fragile, born prematurely, or have other medical problems that make open-heart surgery too dangerous right after birth.^[16]

During the hybrid procedure, doctors place small bands around the blood vessels leading to the lungs to control blood flow and may insert a tiny tube called a stent into the ductus arteriosus to keep it open. This procedure does not require opening the chest fully or using a heart-lung machine. It gives the baby time to grow stronger before undergoing a more complex surgery later. This staged approach has shown promise, with some studies reporting survival rates of around 70 percent for high-risk babies who would have had very low chances of survival with traditional methods.^[16]

The hybrid procedure is still being studied and refined. It is not yet standard practice everywhere, but specialized centers in the United States and other countries offer it as part of clinical trials or as an option for carefully selected patients. The procedure requires advanced equipment, including specially designed stents that are small enough to fit into a newborn’s blood vessels. These devices have recently become available through special approval processes, allowing doctors to use them even though they are not yet fully approved for widespread use.^[16]

Another area of research involves improving how doctors manage heart failure in children and adults living with hypoplastic left heart syndrome. The right ventricle, which takes over the workload for the entire body, often becomes weak over time. This leads to symptoms like fatigue, swelling, and difficulty breathing. Researchers are testing whether medications used for heart failure in adults, such as drugs that reduce the heart’s workload or improve how it pumps, might also help children with single-ventricle hearts.^[17]

These clinical trials are testing different classes of heart failure drugs to see if they can slow down the progression of heart muscle damage, improve quality of life, and delay the need for heart transplant. However, results so far have been mixed, and most traditional adult heart failure therapies have not been very effective in this population. Scientists believe this is because the failing right ventricle in hypoplastic left heart syndrome behaves differently from the failing left ventricle in adults with typical heart failure.^[17]

Some research centers are also exploring stem cell therapies to help repair or strengthen the heart muscle. Stem cells are special cells that can develop into different types of tissue. The idea is to inject these cells into the heart to encourage new muscle growth or improve blood flow. This type of treatment is still in very early stages of testing, and researchers are learning whether it is safe and whether it can actually improve heart function in children with hypoplastic left heart syndrome.^[8]

There are also ongoing trials looking at fetal interventions, which are procedures performed on babies while they are still in the mother’s womb. For some babies with early signs of heart problems that could lead to hypoplastic left heart syndrome, doctors may be able to perform a procedure before birth to open a blocked heart valve. This could allow the left side of the heart to develop more normally, potentially avoiding the need for three-stage surgery. These fetal procedures are highly specialized and only offered at a few centers around the world as part of research studies.^[13]

In the United States and Europe, several medical centers are recruiting families to participate in studies to better understand the long-term outcomes for children with hypoplastic left heart syndrome. These studies collect information about growth, brain development, exercise ability, and quality of life. Some also test new medications or surgical techniques in carefully controlled Phase I (safety), Phase II (effectiveness), or Phase III (comparison to standard treatment) clinical trials. Families interested in learning more about these opportunities can ask their child’s heart doctor about available studies.^[22]

Most common treatment methods

• Medications
  • Alprostadil to keep the ductus arteriosus open in newborns
  • Medicines to reduce fluid buildup and control blood pressure
  • Medications to prevent blood clots
  • Drugs to manage irregular heart rhythms
• Staged surgical procedures
  • Norwood procedure (first surgery, usually within the first week of life)
  • Glenn procedure (second surgery, typically at three to six months of age)
  • Fontan procedure (third surgery, usually between two and five years of age)
• Hybrid procedure
  • Less invasive alternative to Norwood operation for high-risk infants
  • Placement of bands on lung vessels and stent in ductus arteriosus
  • Allows baby to grow stronger before more complex surgery
• Heart transplant
  • Replacing the underdeveloped heart with a healthy donor heart
  • May be chosen if surgeries are not successful or heart fails later in life
  • Requires lifelong medications to prevent rejection
• Fetal interventions
  • Procedures performed before birth to open blocked heart valves
  • May help left side of heart develop more normally
  • Highly specialized and offered only at select research centers