Hypoplastic left heart syndrome

Hypoplastic left heart syndrome is a rare and severe congenital heart defect in which the left side of the heart, including the left ventricle, aorta, and often the aortic and mitral valves, fails to develop enough to support the body's circulation after birth. It accounts for two to three percent of all congenital heart disease and is the most common defect involving only a single functioning ventricle. In a healthy fetus the underdevelopment causes few problems because the placenta handles circulation, but once a newborn's fetal blood vessels close after delivery, the right side of the heart must take over pumping blood to the whole body, a job it is not built for. Infants show poor feeding, bluish skin from low oxygen, and weak pulses within the first days of life, and without treatment the condition is fatal. The cause is thought to combine genetic mutations with abnormal blood flow patterns during heart formation. In the United States the syndrome occurs in roughly one of every 3,841 live births and is one and a half times more common in boys. Survival now depends on a staged series of open heart operations or, in some cases, heart transplantation.