What is Hypoplastic Left Heart Syndrome (HLHS)?
What is Hypoplastic Left Heart Syndrome (HLHS)?Hypoplastic left heart syndrome (HLHS) is a serious, but rare, congenital heart defect that causes abnormal development of the left side of the heart during gestation. This results in poor circulation of blood flow through the heart. Congenital heart defects refer to those conditions present at birth. Children born with this condition usually require surgery within the first few weeks of life.
Hypoplastic left heart syndrome can involve different structures that do not fully develop on the left side of the baby’s heart. Developmental malformations can include:
- Left ventricle. If the left ventricle has not developed, it is too small
- Mitral valve. In these cases, the mitral valve has not formed or is too small
- Aortic valve. The aortic valve has not formed and is too small
- Ascending section of aorta. The ascending portion of the aorta has not formed or is too small
- Atrial septal defect. Children born with HLHS often have a hole between the left and right upper chambers of the heart, known as an atrial septal defect
Babies born with hypoplastic left heart syndrome cannot properly circulate oxygen-rich blood throughout the body. During normal development in a mother’s womb, the two openings between the left and right side of the heart are formed and will close within a few days after being born. However, for a baby with HLHS, these holes do not close and the oxygen-rich blood is redirected to the right side of the heart, which pumps blood to both the lungs.
Eventually, when these openings finally close it becomes difficult to pump the oxygen-rich blood throughout the body.
Signs & Symptoms of Hypoplastic Left Heart Syndrome
SymptomsHypoplastic left heart syndrome is a critical illness for an infant and soon after their birth they will exhibit signs of the condition. Most babies with HLHS are diagnosed while in the mother’s womb or very soon after birth. Therefore, a pediatric cardiologist or heart specialist should be available during the delivery of the child.
Symptoms for HLHS include:
- Cyanosis. This condition is caused by lack of oxygenation. The lips and gums of a person will become grayish-blue in color.
- Breathing. The baby will have rapid or difficulty breathing
- Feeding. The infant will have poor feeding
- Cold hands and feet. Because of the lack of blood circulation and oxygen reaching the extremities, the baby might have cold hands and feet
- Weak pulse. Infants may show signs of heart failure or heart disease
- Extreme sleepiness. Due to lack of oxygen, infants with HLHS may experience extreme sleepiness
If the openings between the left and right sides of the heart do close for babies with hypoplastic left heart syndrome, they could go into shock or die. Babies experiencing shock may be conscious or unconscious.
Signs of shock for babies include:
- Cold, clammy, pale skin
- Bluish-gray lips
- Rapid or weak pulse
- Difficulty breathing, or slow or shallow breaths
- Dull stare in the eyes
What Causes Hypoplastic Left Heart Syndrome?
CausesThe cause of hypoplastic left heart syndrome and other congenital heart defects is unknown. However, hypoplastic left heart syndrome begins during the developmental stage while a baby is in the mother’s womb. During this period, the openings between the right and left side of the heart that allow oxygen-rich blood and oxygen-poor blood to flow to and from the heart and lungs forms abnormally, reducing the flow of blood from the left side of the heart. This obstruction of oxygen delivery causes excess work for the right side of the heart and reduction of oxygen-rich blood throughout the body.
Defects in the genes and chromosomes are believed to be a possible cause of heart defects like HLHS. Environmental exposure to toxins or what a mother eats or drinks during pregnancy could contribute to heart defects. In addition, certain medications should be avoided during pregnancy because of the risk for developing birth defects.
Parents who have one child born with hypoplastic left heart syndrome are at risk for having another child with a heart defect. Discussing this possibility with a doctor or seeking genetic counseling may be an option for parents concerned about this happening.
Risk Factors
Risk FactorsBecause the cause for hypoplastic left heart syndrome is unknown, it is difficult to discuss with certainty the risk factors that cause the condition. However, genetics are believed to play a role in the abnormalities that create hypoplastic left heart syndrome.
Changes in the baby’s genes or chromosomal damage occur in the mother’s womb. Exposure to toxic chemicals while pregnant could cause chromosome deviations. In addition, what a mother eats, drinks, or takes as medication could adversely affect the unborn child. Some medications are known to cause birth defects and should be avoided.
Findings show that parents with one child having a heart defect are at a higher risk for having another child with a similar disorder.
Complications
ComplicationsBabies with hypoplastic left heart syndrome will die without surgery. If left untreated, a child would not be expected to survive longer than a few days or weeks after birth. The risk of HLHS complications or death are highest during the first stage of surgery. The second and third stages of surgery have an increased survival rate. Children who experience staged surgeries will continue to need special care and treatments throughout their life to ensure proper growth and development.
Children with HLHS often have physical and developmental delays, and parents may need additional educational services and physical therapies to help their child adjust. There is an increased risk for heart failure and heart rhythm issues. In addition, children with HLHS can develop digestive and liver complications.
This condition causes a child to become easily fatigued, therefore limiting their participation in exercise. Eventually, people with HLHS may require a heart transplant to survive into adulthood. As with other congenital heart disorders, children must continue regular follow-up visits with a pediatric cardiologist or heart specialist throughout their lifetime.
Other complications common to hypoplastic left heart syndrome may include:
- Fatigue
- Heart arrhythmias
- Fluid buildup in the lungs, abdomen, legs, and feet
- Blood clots
- Developmental issues
Prevention
PreventionTo date, there is no solid line of prevention for hypoplastic left heart syndrome. However, for people with a family history of congenital heart defects, they should see a genetic counselor or specialist before getting pregnant.
Trust NewYork-Presbyterian for Hypoplastic Left Heart Syndrome
The NewYork-Presbyterian Congenital Heart Center retains world renowned pediatric heart surgeons whose expertise in treating children with congenital and acquired cardiovascular conditions is unsurpassed. A combined program of NewYork-Presbyterian Morgan Stanley’s Children’s Hospital and NewYork-Presbyterian Komansky Children’s Hospital together with the NewYork-Presbyterian Congenital Heart Center bring big treatments to our most tiny patients.
Contact a NewYork-Presbyterian Congenital Heart Center to schedule an appointment with a leading pediatric cardiologist or pediatric cardiovascular surgeon. Knowing the treatment options available to your child can alleviate some of your feelings of doubt and confusion. NewYork-Presbyterian is here to help you and your child stay healthy.