What is HLHS?

Hypoplastic left heart syndrome (HLHS) is a complex congenital cardiac defect related to the underdevelopment of left-sided heart structures. These left-sided heart structures are responsible for pumping blood to the entire body.

Normal Blood Flow Through the Left Side of the Heart

Left upper chamber (the left atrium), through the mitral valve, left lower chamber (the left ventricle), out the aortic valve to the aorta, which then delivers blood to the body. 

Blood flow with HLHS Disease

In HLHS, the left ventricle is too small, the two valves (aortic and mitral valve) are either too small or not present, the aorta is too small, and therefore, adequate blood flow body cannot be achieved.

Generally, the right side of the heart, which delivers blood from the body to the lungs, is structurally normal. This arrangement of having one normal side and one weak side of the heart forces the right side to function as the only source of delivering blood to both the lungs and body. Oxygenated blood returning from the lungs to the left side of the heart must be delivered across an opening in the upper chambers (atrium) of the heart to the right side.

In addition to the atrial communication, the ductus arteriosus (a blood vessel that is a normal part of fetal circulation and typically closes in the first few days immediately after a baby is born) is required to remain for blood to flow from the right side of the heart to the body. To keep this vessel open, a medication will be given (prostaglandin E) until the time of surgical palliation.

Children diagnosed with Hypoplastic Left Heart Syndrome have many factors influencing their life expectancy. These variabilities include but are not limited to appropriate prenatal care, delivery planning, infant birth weight, the condition of their atrial septum, any obstruction (blockage) in their pulmonary veins, the status of their heart valves, and overall heart function. If left untreated, HLHS is fatal. Survival rates for staged surgical palliations continue to rise as surgical techniques and post-operative care is improved. For children who survive to the age of 1 year, long-term survival is about 90%. Patients who undergo all three stages of palliation experience survival rates >75% at 25 years. With more patients surviving the staged palliations, more information is being collected about the long-term experience and quality of life in children born with HLHS.

Currently, in addition to our Fontan Clinc, Arkansas Children’s Hospital Single Ventricle Clinic is a national leader in studying and improving the neurodevelopmental outcomes in children born with HLHS. Our cutting-edge research is pioneering new diagnostic testing and designing patient specific care plans for every child treated at our center to not only improve but maximize their quality of life.


Signs and symptoms vary greatly on when the diagnosis is made and the status of the ductus arteriosus closing. If the ductus does not remain open or patent, the infant will have poor perfusion of the body. This causes a state of shock where they become extremely cyanotic (blue) and ill, requiring immediate medical attention.

Infants will typically appear to have a blue hue (cyanosis), along with difficulty breathing or fast breathing (tachypnea), may not eat well or refuse to eat completely, and may appear lethargic or excessively sleepy. All of this is a result of poor perfusion of oxygenated blood to the body. Sometimes these symptoms are not present immediately after birth but rather appear and worsen as the ductus closes. Lack of or delay in medical attention during this time may result in shock. This is especially concerning because many bodily functions can be affected: neurological, renal, liver, some of which may not be reversible or recoverable.


Early diagnosis during prenatal care with a well-orchestrated birthing plan sets infants with HLHS up for improved chances of survival during this critical time. Routine prenatal anatomy ultrasounds performed at an obstetrician’s office will commonly trigger follow-up when concerns for HLHS are present. At that time, a specialized ultrasound, fetal echocardiogram, is performed by a pediatric cardiologist to identify the unique concerns of the abnormal heart structures.


Surgical Intervention

Hypoplastic left heart syndrome (HLHS) requires immediate medical management and surgical intervention very soon after delivery. Specifics of the infant’s heart will be discussed extensively by the pediatric cardiology and cardiothoracic surgery teams. This evaluation will determine the interventions needed and the timing of those interventions in the immediate neonatal period. 

For babies diagnosed before birth (prenatal), the medical team present for the delivery is prepared to immediately begin placing catheter lines (IVs) and initiating medications needed to ensure as much stability as possible. When a diagnosis is made after birth (postnatal), the infant may require aggressive medical management and resuscitation depending on the severity of their clinical situation. 

Ductal Stent

Interventional procedures such as ductal stent placement (Hybrid approach) or medical palliation along with surgical placement of pulmonary artery bands may be indicated to stabilize the amount or direction of blood flow to the lungs and the body. These procedures are performed in the Cardiac Surgery Operating Room or Cardiac Catheterization Lab

Norwood Procedure

Traditional surgical palliation (the Norwood procedure) is routinely performed sometime in the first week of life. The primary goal of this surgery is to convert the heart into a single pumping chamber and to create a stable pathway for blood to get to the lungs. This will be the first stage of a progression of surgeries (usually, three surgeries over the first five years of life are needed). Each surgery will be specific to the child’s anatomy and planned out thoroughly by the pediatric cardiology and cardiothoracic surgery team. The overall goal of these surgeries is to set up a “single ventricle” (the right heart) as the main pumping chamber of blood circulation while pulmonary blood (blood to the lungs) drains back passively. As the child grows, they will require a series of tests/exams to evaluate for “candidacy” of progression down this pathway.

Glenn Procedure

The second palliation, the Glenn, is typically performed sometime around 3 – 6 months of age. 

Fontan Procedure

The final palliation, a Fontan, is undertaken after the child is 2 – 3 years old. However, some children may be delayed until older. 

Post-Operative Care

Your care provider will provide an individualized care plan to each patient due to the complexity and whid range of recovery for each of the surgeries.