What Are the 3 Stages of the Fontan Pathway for CAVSD?

When a baby is born with an unbalanced complete atrioventricular septal defect (CAVSD), one of the heart’s lower pumping chambers (ventricles) is too small to do its job. Because the heart cannot be repaired into a typical two-pump system, doctors use a series of three staged surgeries known as the single-ventricle or Fontan pathway ^[1][2]. The goal of this pathway is to separate the oxygen-rich and oxygen-poor blood, using the heart’s one strong ventricle to pump red blood to the body, while rerouting the blue, oxygen-poor blood to flow directly into the lungs without a pump ^[3][4].

This pathway requires three major surgeries spread over your child’s first few years of life. Please note that the age ranges provided below are general guidelines; the exact timing will depend on your child’s individual growth, weight gain, and clinical stability.

Stage 1: Initial Palliation (Birth to 1 Month)

The first step in the pathway happens shortly after birth. Because every unbalanced CAVSD is a little different, this surgery is tailored to your baby’s specific anatomy ^[5]. The main goal of this first surgery is to balance the blood flow between the body and the lungs.

Depending on how the blood is flowing, your baby’s care team may recommend one of the following:

• Pulmonary Artery (PA) Banding: If too much blood is rushing to the lungs, doctors will place a small band around the pulmonary artery to restrict or limit the flow ^[6][7]. This prevents high pressure from causing permanent damage to the lungs, protecting them for the later stages ^[6][8].
• Systemic-to-Pulmonary Shunt (e.g., BT Shunt): If not enough blood is reaching the lungs (often due to a narrowed valve), a small tube or shunt is placed to ensure a steady supply of blood gets to the lungs to pick up oxygen ^[9][10].
• Norwood Procedure: If the main problem is that not enough blood is getting to the body (often due to a narrowed or underdeveloped aorta), a Norwood surgery is necessary to rebuild the aorta and create a clear, stable pathway for blood to reach the rest of the body ^[9][11].

The “Interstage” Period (A Crucial Time at Home)

The time between the first surgery and the second surgery is known as the interstage period. This is a fragile and critical window where your baby will likely be at home but requires intense monitoring ^[12][13].

During this time, your care team will likely enroll you in a home monitoring program where you will track your baby’s weight and oxygen levels daily to catch any subtle changes early ^[12][14]. Additionally, babies with a single ventricle burn a lot of calories but get tired very easily while eating. It is extremely common for them to need a feeding tube (like an NG or G-tube) to ensure they gain the weight necessary to be strong enough for the next surgery ^[13][15].

Stage 2: The Glenn Procedure (4 to 6 Months)

Around 4 to 6 months of age, your baby will undergo the second surgery, called the Bidirectional Glenn procedure (or sometimes a Hemi-Fontan) ^[16].

During this surgery, the surgeon disconnects the large vein that carries oxygen-poor blood from the upper body and head (the superior vena cava) and attaches it directly to the pulmonary artery ^[16].

• Why it helps: This reroutes half of the body’s blue blood straight to the lungs. This takes a significant amount of stress and workload off the single working ventricle, as it no longer has to pump that blood ^[16].
• Recovery: Post-operative care requires specialized monitoring, and babies may need specific sedation and pain relief as their bodies adjust to the new blood flow ^[17].

Stage 3: The Fontan Procedure (2 to 4 Years)

The final step is the Fontan procedure, typically performed when the child is between 2 and 4 years old.

In this surgery, the surgeon takes the large vein carrying oxygen-poor blood from the lower half of the body (the inferior vena cava) and connects it to the pulmonary artery ^[3][4].

• The completed circuit: This establishes what doctors call a total cavopulmonary connection ^[3]. Now, all oxygen-poor blood from the body flows passively into the lungs, entirely bypassing the heart’s pumping chambers ^[3][18].
• The outcome: The single working ventricle is now solely responsible for pumping oxygen-rich blood to the body, just like the left ventricle in a typical heart.

Ongoing Care and Watchful Waiting

While the Fontan pathway is a life-saving strategy, it is a palliative treatment, meaning it manages the condition but is not a cure ^[1]. The success of these stages relies heavily on the health of the common atrioventricular (AV) valve. If this valve leaks significantly (regurgitation), it can overwork the single ventricle. If necessary, your surgeon can attempt to repair the leaking AV valve during the Glenn or Fontan surgeries to protect the ventricle, though this does add risk to the procedures ^[19][20].

Even after a successful Fontan procedure, patients need lifelong specialized care. Because the blood flows to the lungs without a pump, the veins stay at a higher pressure. Over time, this chronic central venous hypertension can lead to late complications, such as protein-losing enteropathy (PLE) (where essential proteins are lost through the digestive tract) or plastic bronchitis (a condition affecting the airways) ^[21][22].

This is exactly why your child will need a lifelong congenital heart specialist—to proactively monitor your child’s health, manage these risks, and support their single ventricle for decades to come.