Hypoplastic left heart syndrome (HLHS) is a critical congenital (birth defect) heart disease where the left side of the heart is underdeveloped and smaller in size. This condition disrupts the heart’s ability to pump blood leading to poor blood circulation and inadequate oxygen supply throughout the body. Though this condition is not completely curable, it can be managed with multiple surgeries before the child is five years old to ensure adequate blood circulation.
What is hypoplastic left heart syndrome?
Dr Kavya Mallikarjun, consultant, Pediatric Cardiology, Manipal Hospital, Bengaluru, says HLHS is a congenital condition where the mitral valve (divides the two left chambers of the heart) is too small or entirely closed or the left ventricle is severely underdeveloped. It is not capable of supporting systemic circulation. She adds that when the left side of the heart is underdeveloped, the blood flow through the aorta (the main artery that carries blood from your heart to the rest of your body) is impeded.
How HLHS hampers supply of oxygenated blood
Dr Thejaswi N Marla, Clinical Lead, Minimally Invasive Cardiac Surgery, Fortis Malar, Chennai, explains that the right side of the heart pumps oxygen-poor blood from the heart to the lungs where it gets oxygenated. The left side of the heart circulates this oxygen rich blood to the rest of the body. However, in babies with HLHS, the left side of the heart cannot pump oxygen-rich blood to the body properly.
Dr Mallikarjun says, babies diagnosed with this condition will have structural defects on the left side of their heart mainly in their heart valve and chamber.
What causes HLHS
While there are no specific causes for HLHS, genetic factors are generally cited as a major reason for this condition. According to Dr Mallikarjun, this condition could be genetic or be caused due to a viral infection or defective cardiac muscle developed on the left side of the heart.
“The risk of HLHS and related congenital defects of the heart is higher among siblings,” she adds.
How to diagnose HLHS before birth
Congenital heart disease may be diagnosed during pregnancy or soon after the baby is born.
During pregnancy, screening tests help check for birth defects and other health conditions. HLHS can be diagnosed with the help of a scan (usually carried out when you’re between 18 and 20 weeks pregnant). If it is suspected to be HLHS, then a detailed screening through fetal echocardiography takes place, explains Dr Mallikarjun.
“Fetal echocardiography can evaluate any abnormal or congenital heart defects, if done properly and at the right time,” she adds.
Symptoms of HLHS in newborn baby
The Centers for Disease Control and Prevention (CDC) estimates that at least 1025 babies born every year in the US suffer from HLHS.
According to the CDC, newborn babies found with the following symptoms should be screened for heart defects, especially HLHS:
- Breathing problems
- Pounding heart
- Weak pulse
- Bluish skin colouration
Babies diagnosed with HLHS might face nutritional issues as they do not have the energy to feed properly due to limited oxygenated blood supply and might require extra nutritional food. Sometimes external feeding support might also be required to manage their health.
Hypoplastic left heart syndrome surgical intervention
Three complex heart surgeries at various intervals, Norwood procedure, bi-directional Glenn Shunt and Fontan procedure are performed to manage HLHS condition. These surgeries are done to manage better blood circulation and ensure oxygenated blood flow is facilitated through the right ventricle.
- Norwood procedure is the first surgery performed shortly after birth (within two weeks). It involves creating a new aorta and connecting it to the right ventricle, says Dr Marla. This allows the right ventricle to pump blood to both the lungs and the body.
- In the bi-directional Glenn shunt procedure, we connect the pulmonary artery to the superior vena cava, says Dr Marla. In cases where the right ventricle may not pump enough blood, the superior vena cava (carries blood from the head, neck, arms, and chest) returns oxygenated blood from the upper part of the body to the heart, adds Dr Marla. This procedure is performed when an infant is four to six months of age.
- The Fontan procedure is performed when a baby is around two to three years old. It involves connecting the pulmonary artery and the inferior vena cava (which redirects the blood flow from the lower body directly into the lungs).
Dr Mallikarjun says that if HLHS is not treated in babies, their survival rate is very low.
Takeaways
Hypoplastic left heart syndrome requires a delicate balance of surgical intervention and continuous care to ensure the best possible outcomes. Although there is no known cure for HLHS, treatments can help babies with the condition live longer. Babies with hypoplastic left heart syndrome, however, may experience lifelong issues.
