The type of operation needed in the newborn period is quite varied depending on the specific type of single ventricle cardiac defect. In some babies there is not enough blood flow into the lungs, resulting in cyanosis. In these babies, a tube graft is placed from an artery (usually the left subclavian or left innominate artery) to the pulmonary artery. This is called a systemic to pulmonary artery shunt or Blalock-Taussig (BT) shunt.
In other babies, the flow of blood into the lungs may be too much, placing an extra burden on the ventricle and exposing the pulmonary arteries to dangerously high pressure. In these babies, a procedure will be performed to restrict blood flow to the lungs. This is done by placing a piece of material or a "band" around the pulmonary artery to narrow it.
Other newborns have more complex heart disease and require more complex operations, such as the Norwood procedure for patients with hypoplastic left heart syndrome.
Rarely, a baby with a single ventricle anomaly will have "just right" flow into the lungs so that an equal amount of blood flows to the body and the lungs. These babies do not require intervention in the newborn period.
Whatever is needed in the newborn period, the aim is typically to balance the blood flow between the lungs and the body, achieving stable oxygen levels and adequate heart function.
The second stage for most children with single ventricle anomalies is undertaken around three to six months of age. The operation is called a "bi-directional Glenn" or sometimes a "hemi-Fontan."
During the Glenn operation the large vessel that drains blood from the head and upper body back to the heart (the superior vena cava) is taken off the heart and sewn directly to the pulmonary artery. If a prior BT shunt was present, it is removed. If a pulmonary artery band was previously placed, it may be removed but can also be left in place in some situations.
The Glenn operation has two major advantages in most children. First, because the connection is a direct one between two blood vessels, rather than made of artificial matter, it has the ability to grow with the child.
Second, it removes some of the work from the single ventricle so that the ventricle will no longer have to pump all of the blood to the lungs in addition to all of the blood to the body. This replaces the risk for early heart failure. In most cases this stage is tolerated the best of all the stages with a survival rate of 95 percent or better.
After the Glenn operation most children will have oxygen saturation levels of 75 percent to 85 percent.
The third and final stage in the reconstruction of a single ventricle heart defect is the Fontan completion operation. This operation is usually performed at 2 or 3 years of age, based on the child's size and clinical status.
During the Fontan operation, the blood vessels returning blood to the heart from the lower half of the body (inferior vena cava) is connected directly to the pulmonary arteries. Until now this blood has bypassed the lungs and has been pumped directly to the body resulting in oxygen levels lower than normal.
After a Fontan operation, oxygen levels will be nearly normal (90s). The two most common methods of performing the Fontan completion today are the "lateral tunnel" and the "extra-cardiac" techniques.
In the lateral tunnel method, a tunnel-like patch is placed inside the atrium so that blood returning from the inferior vena cava is directed through this tunnel. A connection is then made between the end of the tunnel / top of the right atrium and the underside of the pulmonary artery.
In the extra-cardiac method, the inferior vena cava is connected to a synthetic tube, usually Gore-Tex, and is sewn to the underside of the pulmonary artery, routing this blue blood flow outside of the heart.
In either method, a hole, or "fenestration," is often made between the Fontan circuit and the right atrium so that if pressures become very high in the Fontan circuit, there is a "pop-off" into the heart. Patients with fenestrations may have a more stable post-operative course with smaller and less prolonged collections of fluid within the chest (a common complication after Fontan surgery). Many fenestrations close spontaneously many months after surgery, but can also be closed during a cardiac catheterization procedure if deemed necessary.
Currently, when patients have been well prepared for Fontan completion, the success rates are 90 percent and higher.