Written by: Lauryn Feil
Reviewed by: Carlos Mery, MD
Congenital heart defects are the most common types of birth defects, affecting 1 in every 100 babies born. While there are a variety of heart defects that range in severity, with treatment the percentage of children surviving and living healthy productive lives is very high. One of the rarest and more severe heart defects is hypoplastic left heart syndrome (HLHS), which affects about 2 to 3 percent of babies born with a congenital heart defect or about 1 in every 4,344 births.
The term “hypoplastic” refers to underdevelopment of a tissue or organ. In the case of HLHS, the left side of a baby’s heart (the side which receives oxygen-rich blood from the lungs and pumps it out to the body) is critically underdeveloped. The mitral and aortic valves are either completely closed, or they are very small. The left ventricle itself is tiny, and the first part of the aorta is very small, often only a few millimeters in diameter. As a result the left side of the heart is completely unable to support the circulation needed by the body’s organs.
Without a functioning left ventricle, the right side of the heart must perform the action of pumping blood to both the lungs as well as out to the rest of the body. Babies born with HLHS have a bluish appearance known as cyanosis as a result of mixing oxygen rich and oxygen poor blood.
Because HLHS is complicated to repair, most babies need three or more surgeries after birth. The surgeries are risky and require a great deal of skill and management from a team of cardiac specialists. Carlos Mery, MD, UT Health Austin Congenital Heart Surgeon in the Texas Center for Pediatric and Congenital Heart Disease, the clinical partnership between UT Health Austin and Dell Children’s Medical Center, specializes in the management of children and adults with congenital heart disease, including simple and complex heart defects like HLHS.
“Hypoplastic left heart syndrome is uniformly fatal without surgery and this is one of the riskiest and most complex conditions we treat here at Dell Children’s,” says Dr. Mery. “We treat it with a series of three operations beginning with the Norwood within the first few weeks of life, followed by the Glenn about 4 to 6 months later, and then the Fontan performed 18 to 36 months after the Glenn.”
- The Norwood procedure converts the right ventricle into the main ventricle pumping blood to both the lungs and the body. The main pulmonary artery and the aorta are connected and the main pulmonary artery is cut off from the two branching pulmonary arteries that direct blood to each side of the lungs. Instead, a connection called a shunt is placed between the pulmonary arteries and the aorta to supply blood to the lungs.
- The Glenn procedure diverts half of the blood to the lungs when circulation through the lungs no longer needs as much pressure from the ventricle. The shunt to the pulmonary arteries is disconnected and the right pulmonary artery is connected directly to the superior vena cava, the vein that brings deoxygenated blood from the upper part of the body to the heart. This sends half of the deoxygenated blood directly to the lungs without going through the ventricle.
- The Fontan procedure connects the inferior vena cava, the blood vessel that drains deoxygenated blood from the lower part of the body into the heart, to the pulmonary artery by creating a channel through or just outside the heart to direct blood to the pulmonary artery. At this stage, all deoxygenated blood flows passively through the lungs.
The overall goal of these procedures is to reconstruct the structures of the heart to allow for the right ventricle to pump blood to the rest of the body while the vessels are redirected into the lungs to oxygenate blood without it having to pass through the heart. Because of innovations such as specialized monitoring and technologies in the operating room and approaches to care after surgery, the long-term survival rate and positive outcomes for patients born with HLHS has increased drastically in the last 30 years.
Dr. Mery stresses that the survival and success of these patients is dependent on more than just surgery. “The ability to treat hypoplastic left heart syndrome is a marker of success for a program. You have to have a pretty robust multi-disciplinary team, and that doesn’t only include surgeons, it includes anesthesiologists, intensivists, cardiologists, hospitalists, nurses, therapists, staff, and more, all working together seamlessly to be able to provide the care for these patients,” says Dr. Mery.
Since the Texas Center for Pediatric and Congenital Heart Disease began seeing patients in the fall of 2018, it has expanded at Dell Children’s Medical Center to include an entire dedicated cardiac unit with 24 beds and a second operating room opening soon to meet the high demand of the Central Texas area. This is particularly helpful for patients who are diagnosed with rare or highly complex conditions like HLHS.
“Before this program, the families of babies that were diagnosed with hypoplastic left heart syndrome would have to leave Austin and relocate to Houston or Dallas for about six months, which is the time it takes between the first operation and the second operation,” says Dr. Mery. “That’s not the case anymore, we have the ability to deliver the best care to those patients right here in Austin, which is extremely exciting. It’s one of the reasons why we came here,” he says.
The program emphasizes a wholistic care approach that puts the patient and their family at the center of the care team to meet each patient’s unique needs. With ongoing support throughout childhood and into adulthood, children born with congenital heart defects like HLHS are able to receive world-class care close to home. “We have received a lot of gratitude from the families here and it’s really an honor to be able to provide this service to them,” says Dr. Mery.