Hypoplastic left heart syndrome (HLHS) is a rare heart defect where the left side of the heart is underdeveloped and cannot provide effective circulation. For babies born with HLHS to survive, a heart vessel called the ductus arteriosus (1), which normally closes shortly after birth, needs to remain open so that blood can pass from the baby’s heart to the body. To keep the vessel from closing, doctors typically treat the baby with a medication called prostaglandin E1. Babies with HLHS also need to have a hole between the upper chambers of the heart (2) to allow oxygen-rich blood to pass into the heart so it can be pumped to the rest of the body. Babies with HLHS also have an underdeveloped mitral valve (3) and aortic valve (4), resulting in a small left ventricle (5), which cannot provide blood to the body.

One strategy for treating HLHS is a series of surgeries that address the different heart defects.

Surgery 1:  At approximately 1 to 2 weeks of life: Norwood Procedure

This image is reprinted with permission from University of Michigan Congenital Heart Center.

The goals of the first stage procedure is to create an unimpeded pathway of blood from the heart to the body, to create a large communication between the upper chambers of the heart to allow oxygen-rich blood from the lungs to pass through the heart, and to create a balanced flow of blood from the heart to the lungs. The right ventricle is made to pump blood to the body. This is accomplished by surgically combining the blood vessel (pulmonary artery) that comes out of the right ventricle and goes to the lungs with the blood vessel (the aorta) that emerges from the left ventricle and carries blood to the body. This step also includes removing the wall between the heart’s two upper chambers (the atrial septum) and placing a man-made (prosthetic) tube to handle blood flow to the lungs. A shunt is placed between one of the branches of the aorta and one of the pulmonary arteries (modified Blalock-Taussig shunt) or directly from the right ventricle to the lung arteries (Sano shunt). As a result, blood returning from the lungs to the left atrium will cross the surgically removed atrial septum and mix with blood coming back from the body in the right atrium. After the blood flows into and fills the right ventricle, it is pumped to both the body and the lungs. In some cases, there is an inadequate or nonexistent hole between the atria after birth. This creates a backup of blood in the lungs and prevents oxygen-rich blood from the lungs from being able able to be sent to the body. An emergency atrial septostomy may have to be performed immediately after birth.

Surgery 2: At approximately 3 to 4 months of life: Bidirectional (or Hemi-Fontan) Glenn Procedure

This image is reprinted with permission from University of Michigan Congenital Heart Center.

In this stage, the superior vena cava that delivers venous blood from the upper part of the body (head, neck and arms) to the heart is connected directly into the pulmonary artery. The shunt that was previously placed is removed. With this step, blood flow to the lungs comes directly from the upper part of the body without first going to the heart. This lifts some of the work-load from the heart since it no longer must pump blood to both the lungs and the body. Because the venous blood from the lower part of the body still goes directly to the heart, the oxygen level (saturation) remains less than normal and similar to after the Norwood Procedure.

Surgery 3:  At approximately 18 months to 6 years of life: The Fontan Procedure

This image is reprinted with permission from University of Michigan Congenital Heart Center.

At this stage, which is typically performed when the child reaches about 18 months of age, the vein (the inferior vena cava) that brings blood back from the lower part of the body to the heart is also connected directly into the lung circulation, bypassing the heart and saving the heart (and its only functioning ventricle) the work of pumping blood to the lungs. With this procedure, the circulation of the oxygen-depleted venous blood and the oxygen-rich arterial blood are separated; therefore, the oxygen level to the body normalizes. Blood returning from the lungs (now rich in oxygen and pink in color) returns to the heart and is pumped out by the right ventricle into the aorta and to the body. After this stage, there is no pumping chamber connected to the lungs. Blood must flow passively through the lungs at this stage with the single ventricle being used to pump blood to the body. Often a small hole (fenestration) is created to function as a "pop-off valve" in case the pressure of the venous circulation gets too high. This may result in a slightly lower than normal saturation. In some situations, this hole can be closed in the catheterization lab if it is deemed to no longer be necessary.

Children treated with these staged surgeries may suffer from continuing heart failure. This may be due to any of several factors, including failure of the right side of the heart to pump blood to the entire body, high pressure in the blood vessels of the lungs due to lung disease, or abnormal heart rhythm. Medications such as Lasix, ACE inhibitors and beta blockers are commonly used to manage congestive heart failure symptoms.

Twenty to 40 percent of children die before or soon after all of the stages of surgery are performed. Long-term outcomes for this approach are not well known, but there is increasing concern about the longevity of the Fontan circulation into the adult years.

New "hybrid" treatments are being developed where interventional cardiologists and heart surgeons work together at the same time to complete some of these procedures.

Learn More

For more information about hypoplastic left heart syndrome and treatment options, click here.

And to watch the amazing story of Ian McDonagh and the interventional cardiologists who pioneered a treatment strategy that saved Ian’s life and has been used around the world ever since, click here.