Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a heart condition present from birth (congenital heart defect). In HLHS, the heart's left side (including the aorta, aortic valve, left ventricle and mitral valve) is underdeveloped. At birth, oxygen-rich blood bypasses the underdeveloped left side of the heart, going through openings between the left and right side that normally close a few days after birth (the patent ductus arteriosus and the patent foramen ovale). The right side of the heart then pumps blood to the lungs and the body. Therefore, there may be no symptoms for a few days. However, when these openings close, oxygen-rich blood cannot easily get to the rest of the body. Symptoms then develop quickly, and may include problems breathing, pounding heart, weak pulse, and/or an ashen or bluish skin color. Some children with HLHS also have other heart defects, such as an atrial septal defect.

In most children with HLHS, the cause is not known. It typically occurs sporadically in otherwise normal babies. In some children, isolated HLHS is known to be genetic. These cases may be due to mutations in the GJA1 gene with autosomal recessive inheritance, or the NKX2-5 gene with autosomal dominant inheritance. HLHS has also been reported with certain genetic disorders including Turner syndrome, Jacobsen syndrome, trisomy 13, and trisomy 18.

If not treated, HLHS is fatal within the first few days or weeks of life. While treatment is difficult, surgical and medical interventions have improved chances of survival. Treatment may include a series of surgeries to restore function to the left side of the heart (staged reconstruction), or heart transplant. However, even with treatment, lifelong complications are possible and life expectancy may be reduced.