Hypoplastic Left Heart Syndrome (HLHS)

What is Hypoplastic Left Heart Syndrome?

Hypoplastic left heart syndrome, or HLHS, is one of several congenital heart anomalies classified as a single ventricle defect. This rare condition affects about two to three out of every 10,000 babies born each year.

In a normal heart, deoxygenated blood enters the heart through the right atrium. When it reaches the right ventricle, the blood is sent to the lungs via the pulmonary artery to become oxygenated. The oxygen-rich blood then returns to the heart through the left atrium and is pumped into the left ventricle. From there, the blood is pumped through the aorta and delivered to the rest of the body.

In a heart with HLHS, the structures on the left side of the heart do not develop properly in the first eight weeks of pregnancy. The heart has a much smaller left ventricle than a normal heart, as well as an absent or non-functioning mitral valve, which separates the left atrium and the left ventricle. The aorta and the aortic valve may also be smaller than normal as well.

In a normal heart, the left ventricle is very strong so it can pump blood to the body. An underdeveloped left ventricle can't pump enough blood out to the body. Because of this, a baby born with HLHS will not survive without surgery to correct the defect.

The mitral and aortic valves are either completely "atretic" (closed), or they are small (hypoplastic). The left ventricle is tiny. The first part of the aorta is very small. Often only a few millimeters around.

Babies with HLHS are almost always born with an atrial septal defect (ASD). This is a hole between the atria that lets oxygen-rick blood mix with oxygen-poor blood. This way, the blood that the right ventricle pumps out to the body has some oxygen in it.

Hypoplastic Left Heart Syndrome Signs and Symptoms

Newborns with HLHS will have signs and symptoms that point to a potentially serious heart condition. These include:

• Cyanosis (blue tint to the skin, lips and nails)
• Respiratory distress that often gets worse
• Weak pulse in the extremities
• Sleepiness
• Poor feeding
• Pale skin
• Sweaty, clammy or cool skin
• Fast heart rate

If not treated, a baby with HLHS may go into shock and could experience seizures, kidney and liver failure and worsening heart function. These complications may be reversible with proper treatment, depending on the extent of the damage.

Diagnosing Hypoplastic Left Heart Syndrome

HLHS is sometimes diagnosed before a baby is born through a prenatal ultrasound. If this is the case, pediatric cardiologists will work with the mother’s care team, including UH maternal-fetal medicine experts, to develop a care plan for intervening either before birth via fetal heart interventions or after birth.

If a child presents with symptoms of a heart defect after birth, he or she may be referred to one of UH Rainbow’s pediatric heart specialists for further examination and tests. These may include:

Hypoplastic Left Heart Syndrome Treatment

HLHS is most often fatal if not treated right away. At University Hospitals we have a team from UH MacDonald Women’s Hospital and UH Rainbow Babies & Children’s with special expertise in diagnosing and treating HLHS, starting even before the baby is born. Treatment options today are much more advanced than they were just a couple of decades ago. If your child is diagnosed with HLHS, the congenital heart experts at UH Rainbow will work with your family to develop an advanced, individualized treatment plan to correct the defect.

Surgical procedures for HLHS are performed in our state-of-the-art hybrid catheterization and surgical suites. Our facility offers cutting-edge technology, including the most advanced imaging available worldwide and 3-D capabilities. This helps our surgeons better understand and visualize each patient’s unique anatomy while making complex repairs, leading to improved patient safety and outcomes.

In Utero Treatment of HLHS

Fetal aortic valvuloplasty is performed in utero using ultrasound guidance and a catheter-based approach to gain access to the fetus’s heart. It is normally recommended to take place between 20 and 29 weeks of pregnancy. Before the procedure begins, the mother is given an epidural and medication is given to the fetus to keep them calm, comfortable and still. The doctor will then insert a catheter into the mother's abdomen, through the uterus and into the fetus's heart. Once the catheter is inserted and in the correct position, a needle and wire and with an attached balloon is placed into the catheter and threaded into the fetus’s heart to the aortic valve. Once in place, the balloon is gently inflated to enlarge the opening of the aortic valve and increasing blood flow into the left ventricle. The team will check to ensure adequate blood flow before the needle, wire and balloon is removed.

If this procedure is successful it will allow the left ventricle and left sided structures to keep growing during pregnancy the baby can have a functioning and normal sized left ventricle at birth. This will help eliminate the need for potentially numerous heart surgeries after birth.

After the procedure, the mother will usually remain in the hospital for about 48 hours so that the mother and fetus can remain under close supervision. We will continue to follow the mother and fetus closely throughout the remainder of the pregnancy with regular ultrasounds and fetal echocardiograms to evaluate the baby’s heart.

Balloon Cardiac Catheterization

If a baby with HLHS is born with an intact atrial septum, a balloon atrial septostomy may be performed shortly after birth. This cardiac catheterization procedure uses a balloon threaded through a catheter to create or enlarge an atrial septal defect, which allows for oxygen-rich blood to mix with oxygen-poor blood so that the body receives enough oxygen. After this procedure, the ductus arteriosus will be allowed to close since the blood is now mixing through the atrial septal defect. This procedure can help stabilize the baby in the short-term before surgery. The procedure can be done bedside or in the pediatric cardiac catheterization lab.

Surgery

If HLHS is not diagnosed until after birth, a baby will likely need three or more open-heart surgeries in order to repair this complicated heart defect, depending on the severity of the defect. Your baby will be cared for at UH Rainbow’s nationally ranked neonatal intensive care unit (NICU) to provide advanced cardiac care and make sure they are strong enough before the first surgery takes place.

The main surgical procedures used to treat HLHS include:

Norwood surgery: This surgery takes place within the first week of life. The open heart procedure repairs the aortic arch to provide adequate blood flow to the body. Recovery time in the hospital is usually about three to four weeks.

Glenn surgery: This surgery takes place when the baby is four to six months old. With this procedure, blood is sent from the upper body directly to the lungs to receive oxygen. This way, the single ventricle only has to pump blood to the body and not the lungs. Recovery time in the hospital is about one to two weeks.

Fontan surgery: This procedure is usually performed 18 – 36 months after the Glenn surgery. With the Fontan procedure, a separate channel is created to send oxygen-poor blood directly to the pulmonary artery instead of through the heart. This allows the left ventricle to only pump oxygen-rich blood to the body. Hospital recovery time is usually one to two weeks.

Heart Transplant

In some cases, a heart transplant may be recommended for babies with HLHS. This may be more difficult because of the limited availability of donor hearts for babies. However, UH Rainbow has a partnership with the pediatric heart transplant program at Nationwide Children’s Hospital in Columbus, giving our patients and families access to their extensive pediatric heart transplant team. If a heart transplant is determined to be the best option, the expert teams at Nationwide and UH Rainbow can help coordinate and facilitate transplant care.

Home Heart Monitoring

Babies with HLHS are at risk for complications in the first weeks to months of life, particularly during the time between the first and second heart surgeries. UH Rainbow is the first pediatric heart program in Northern Ohio to provide parents of infants born with a rare heart defect a home monitoring system with FaceTime and 24/7 access to their pediatric cardiology team. The Hearts at HOME (High-Risk Outpatient Monitoring and Education) program provides parents with specially configured iPad. This allows parents to submit important data about their child’s health, including weight and oxygen level, to the UH Rainbow team in real time. Hearts at HOME also has a designated nurse navigator that will help coordinate care throughout your child’s journey at UH Rainbow.

Recovering from Surgery

Your child will recovery from their surgeries in our state-of-the-art pediatric cardiac intensive care unit (PCICU), where they will be cared for around-the-clock by specially trained pediatric cardiac intensive care physicians, nurses and staff. As they recover, your child will transition from the PCICU to the pediatric cardiac stepdown unit, where they will receive continuity of care by specially trained staff. Before discharge, our cardiac nursing staff will work with families to set up follow-up appointments, educate them on how to care for their child once they return home, and ensure they have the necessary equipment and supplies.

Between surgeries, your child will require frequent check-ups and observation with the UH Rainbow pediatric heart team to monitor their heart function and overall health. If your child is healthy enough to be at home, their doctor will give you instructions on how to care for your baby at home and how to look out for signs of potential problems.