Hypoplastic Left Heart Syndrome: Recently Diagnosed

While at your most recent ultrasound, your unborn baby has been diagnosed with Hypoplastic Left Heart Syndrome, also known as HLHS. The cause of this rare birth defect, affecting 1,000 babies per year, is unknown and there is nothing that can prevent it. The birth defect occurs in utero while the baby is developing. There is a very slight increased risk (less than 10 percent) that families who have one child born with HLHS will have another child born with a heart defect.

HLHS is defined as a severely underdeveloped left side of the heart. In a healthy heart, the right side of the heart accepts blood from the rest of the body and pumps it to the lungs while the left side of the heart accepts blood from the lungs and pumps it to the body. When the left side of the heart is underdeveloped, the right side must perform both functions, pumping blood to the lungs and to the body.    

During the first few days after a baby is born, the right side of the heart is able to do the job of both the right and left sides because of two processes. The first is through an opening, known as the foramen ovale, by which the blood flowing through the lungs can return to the right heart. The second process is by a blood vessel connecting the pulmonary artery to the aorta, known as ductus arteriosus, that allows the right side of the heart to pump blood to the body in addition to the lungs. The majority of the time, the foramen ovale and ductus arteriosus close after a few days, leaving the heart with no way to pump the blood to the rest of the body.   ------------------------------------------------------------------------------------------------------------------------------------ The Todd and Karen Wanek Family Program for Hypoplastic Left Heart Syndrome (HLHS) is a collaborative network of specialists bonded by the vision of delaying or preventing heart failure for individuals affected by congenital heart defects including HLHS. The specialized team is addressing the various aspects of these defects by using research and clinical strategies ranging from basic science to diagnostic imaging to regenerative therapies.  Contact the program at HLHS@mayo.edu.