What is the Fenestrated Fontan or Stage III Norwood Procedure?The Fontan operation was developed by Dr. Francis Fontan in the early 1970s to treat children with other single-ventricle heart defects. A modified version has been successfully used as the third stage of surgical treatment for children born with HLHS. Just as before your child's Glenn Anastomosis operation, information from medical examinations, echocardiograms and a cardiac catheterisation will help determine when he is ready for Stage III.
After this operation has been completed, your child's heart will have separate pulmonary and systemic circulations, except for a small window (fenestration) between the two pathways at the atrial level. While there are different surgical techniques
available, the end results are the same-all blue blood, returning to the heart by way of the vena caval system (IVC and SVC), is rerouted directly to the pulmonary arteries and then to the lungs. All red blood returning to the left side of the heart through the pulmonary veins from the lungs is pumped by the single ventricle out to the body through the Stage I rebuilt aorta.
A peadiatric cardiologist surgeon converts the Stage II Glenn anatomy to the fenestrated Fontan anatomy in two basic steps. The right atrium is reconnected to the right pulmonary artery using an area of the right atrium called the atrial appendage. This area is enlarged with pericardium (the outer sac of the heart), and a tube-like connection is made with these tissues to the underside of the right pulmonary artery in the same end-to-side garden hose-like fashion described with the Glenn Anastomosis.
Secondly, in order to reroute all IVC blood to the right pulmonary artery, the peadiatric cardiologist surgeon . places a baffle of synthetic Gore-Tex® material within the right atrium. All blue blood flows under normal venous pressures along the right side of the baffle to the pulmonary arteries and thus bypasses the single ventricle. The single ventricle now pumps only red blood out to the body as oxygenated blood returns from the lungs, by way of the four pulmonary veins, to the left side of the baffle.
A fenestration (window) is made in the baffle as a safety or pop-off valve through which blue blood may cross if blood pressure in the lungs becomes too high. Also, a small amount of blue blood will return to the right atrium, in an area called the coronary sinus, from the coronary veins of the heart muscle itself. (Recall that the coronary arteries, arising at the beginning of the aorta, supply oxygen to the heart muscle.) The coronary veins emptying into the right atrium plus the effect of the fenestration result in slightly less-than-normal oxygen levels (90 percent to 95 percent) after completion of Stage III.
Some doctors use an outside-the-heart (external) conduit (tube-like pathway) to redirect blue IVC blood to the right pulmonary artery and on to the lungs. The conduit is made of either synthetic Gore-Tex® material or donated homograft tissue. The surgeon disconnects the IVC from the right atrium, connects it end-to-end fashion to the conduit, then end-to-side sutures the conduit into the underside of the right pulmonary artery. All blue blood now bypasses the single ventricle which pumps only red blood to the body. Normal venous pressures are relied upon for blood flow to the lungs.
A fenestration is placed between the right-sided pulmonary blood flow and the left-sided systemic circuit. This window is created between the conduit and the outside wall of the atrium, acting as the needed safety valve to guard against too-high lung pressures.
The same effect of slightly lower-than-normal oxygen levels (eventually 93 to 95 percent) for Fontan children is present due to the surgically made fenestration and the natural position of the coronary sinus receiving blue blood from the heart muscle itself.
A common complication, usually temporary, after the fenestrated Fontan operation is a build-up of fluid (effusion) around the heart (pericardial) or around the lungs (pleural). If not treated, cardiac or respiratory distress can result. Diuretics are used to minimize these accumulations. Chest catheters can be inserted to pull out (aspirate) the build-up of pleural fluid, or post-operative chest drainage tubes may be left in for several days or even weeks. Oxygen may also be given. The use of fenestrations to regulate pulmonary pressures helps decrease the incidences of effusion while improving cardiac output after this surgery.
Another complication common in some children before or after this third stage operation are collateral (secondary or accessory) blood vessels. They develop over time between the heart and the lungs. These vessels seem to be the body's own attempt to improve oxygen levels in the blood, but what the body intends as a help can actually become a problem: with the Glenn Anastomosis in place or the Fontan completed, the extra pathways allow too much blood flow to the lungs. These children may need special "coils" placed in the tiny, sometimes numerous, vessels to occlude (block) them. This is a procedure done in the cardiac catheterisation lab by one of the cardiologists under guidance of special x-rays and monitors.
As with Stages I and II, your child will be closely followed after the Fontan Procedure with physical exams, ECHOs and heart catheterisations. As needed, your doctors will adjust or change medicines or suggest other treatments to improve your child's condition. If, after any of the three stages of surgery, the heart function weakens, your doctor may suggest considering heart transplantation.
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