Hypoplastic left heart syndrome surgery


 * Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S.[mailto:psingh@perfuse.org],, Keri Shafer, M.D. [mailto:kshafer@bidmc.harvard.edu]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S.[mailto:kfeeney@perfuse.org]

Overview
Failure to treat hypoplastic left heart syndrome can be fatal for the infant. Surgical therapy is the only true way to treat and permanently fix hypoplastic left heart syndrome. Two main methods exist for treatment: transplantation and a three-stage surgical procedure.

Surgical Therapy
Without treatment, hypoplastic left heart syndrome (HLHS) is fatal, but with intervention, an infant may survive. A pediatric cardiothoracic surgeon may perform a series of operations or a full heart transplant. Because these operations are complex and need to be individualized for each patient, a cardiologist must assess all medical and surgical options on a case-by-case basis. After assessment the child's parents are given a percentage chance of survival and the choice of surgery or to take the child home to pass away.

The two methods for treatment of HLHS are transplantation and a three-stage surgical procedure. Each of these are open heart surgeries (meaning the chest is open and the sternum has to be separated), requiring the child to be on a heart bypass machine for at least five hours. The heart is stopped and the heart bypass machine pumps blood to the body. After successful surgery is performed there can be added complications of restarting the heart and getting the child off the heart bypass machine.

The three-stage procedure is a palliative procedure (not a cure), as the child's circulation is made to work with only two of the heart's four chambers.

Norwood procedure
The first step is the Norwood procedure. In this procedure, the right ventricle is used to pump blood into the systemic circulation. Since the right ventricle is no longer directly pumping blood to the lungs, a shunt is required in order to pass deoxygenated blood through the lungs. Either the subclavian artery can be connected to the pulmonary circulation (Blalock-Taussig shunt), or a shunt is made directly from the right ventricle to the pulmonary circulation (Sano shunt). The narrow aorta is enlarged using a patch to improve bloodflow to the body.

During this time the baby may be medically fragile and have feeding problems because the heart is working very hard. There is a considerable degree of venous mixing in the right ventricle, leading to lower oxygenation saturations. In addition, the Blalock-Taussig shunt and the Sano shunt both expose the lungs to systemic arterial pressures, leading in the long term to pulmonary hypertension and eventually to heart failure.

Bi-directional Glenn procedure/Hemi-Fontan procedure
The second stage, the bi-directional Glenn procedure or Hemi-Fontan (see also Kawashima procedure) relieves some of the above problems. In this operation, the superior vena cava is ligated from the heart and connected to the pulmonary circulation. At this time, the Blalock-Taussig or Sano shunt is taken down. At this point, the lungs are no longer exposed to systemic arterial pressures, but much lower venous pressures. Although venous blood from the upper half of the body is no longer mixing with oxygenated blood in the right ventricle, there is still venous mixing from the lower half of the body, leading to some degree of oxygen desaturation.

During this time the child may have improved quality of life as the heart does not have to work as hard.

Fontan procedure
The final procedure, the Fontan (Fontan procedure) completes the repair of the hypoplastic left heart. Although there are several variations, the functional effect is to redirect venous blood from the lower body (through the inferior vena cava) away from the right atrium to the pulmonary artery. Now, there should not be any mixing of oxygenated and deoxygenated blood in the right ventricle. The right ventricle performs the traditional job of the left, supplying the body with oxygenated blood, while the passive systemic venous pressure performs the traditional job of the right, passing deoxygenated blood to the lungs.

The Norwood Procedure is generally performed within a week of birth, the second stage at 3ñ6 months of age, and the Fontan at 18 months to four years of age. There are two types of Fontan: the Lateral Tunnel Fontan, and the Extracardiac Fontan. When the Fontan Procedure was first being done for children with HLHS, the only Fontan was the Lateral Tunnel Fontan. This requires actual cutting in the heart itself to create a "tunnel" by which the blood can travel passively to the lungs. Within the last decade, doctors have created an Extracardiac Fontan. This operation creates a tunnel outside the heart itself which reduces the chances of Fontan patients developing scar tissue on the heart which might later cause arrythmias.