What is Hypoplastic Left Heart Syndrome (HLHS)?

Hypoplastic left heart syndrome(HLHS) describes a spectrum of cardiac abnormalities characterized by marked underdevelopment of the left ventricle – the lower compartment of heart, and ascending aorta– the great vessel receiving blood from the left ventricle. It’s a rare congenital heart defect. Incidence of HLHS is less than 0.5 per 1000 live births and is more common in males than in females.

Hypoplastic left heart syndrome typically presents within the first 24-48 hours of life, with symptoms of cyanosis– bluish discoloration of periphery, increased rate of respiration, respiratory distress, pallor, inactivity, and decreased urine production, which finally develops into shock, without intervention result in death. Occasionally, respiratory symptoms and profound systemic cyanosis are apparent at birth.

If you already have a child with Hypoplastic left heart syndrome, you’re at a higher risk of having another baby with this condition than is a family who does not have a history of congenital heart defects. Beyond family history, there are no clear risk factors for Hypoplastic left heart syndrome.

The newborn infant with Hypoplastic left heart syndrome has a complex cardiovascular physiology. Oxygenated returning to the left atrium, from the lungs, cannot flow into the left ventricle because of underdeveloped mitral valve. Therefore, this oxygenated blood must cross the septum dividing the two upper chambers of atria and mix with deoxygenated blood brought to the right atrium by the veins. The right ventricle then must pump this mixed blood to both the lung and the body circulations that are connected in parallel, rather than in series, by the ductus Arteriosus– a connecting segment between aorta and pulmonary artery. Blood exiting the right ventricle may flow either to the lungs via the branch pulmonary arteries or to the body via the ductus arteriosus and aorta. 

Management involves initial stabilization of the baby. The major effort from the part of the medical personnel is to keep the ductus patent. After birth the ductus usually closes off in 24-48 hours. This should be avoided by using drugs such as Prostaglandin, which would prevent the transit of the baby to shock and consequent death. Diuretics, antibiotics, and other medications can be a useful aid in maintaining a stable state.

Surgical correction is a multistage procedure. The goal of the three staged surgical reconstruction is to eventually separate the circulation to the body(systemic) and lung(pulmonary). The other option for the correction being a cardiac transplantation.