Fontan Circulation

In a usual situation the heart has 2 ventricles (pumping chambers). The right ventricle pumps oxygen depleted (blue) blood to the lungs and the left ventricle pumps oxygen rich (red) blood to the body.

In many complex cardiac conditions, there is only one functioning ventricle, which has to pump blood both to the lungs and to the rest of the body. Fontan’s operation is a series of palliative surgical procedures, which when completed allow the oxygen depleted blood returning from the body to return directly to the lungs via the pulmonary arteries. From there oxygen-rich blood returns to the pumping chamber, and gets pumped around the body. The aims of the operations are to increase the blood that picks up oxygen from the lungs and reduce the workload to the single pumping chamber.

What do the operations involve?
The Fontan’s operation has been around since the early 1970s and the surgical techniques have changed, and continue to change significantly over the years. There are, however, three fundamental stages to the operation.

Stage 1- BT Shunt or PA Band or “Balanced” circulation
This happens at the first few weeks of life and depends on the amount of blood flow that reaches the lungs. If the blood flow to the lungs was excessive, a band would have been put around the main lung vessel to control the flow and protect the lungs from high pressure (PA Banding). This would usually happen through an incision at the site of the chest.

If there was inadequate amount of blood reaching the lungs, then a different procedure called a shunt operation would have taken place. This involves taking an artery which usually takes blood to the arm, and diverting it towards the lung vessels (BT shunt). This again would have happened through an incision at the site of the chest.
In a situation where there is “balanced” amount of blood to the lungs, no initial operation is required.

Stage 2- Glenn Operation/ Bidirectional Cavopulmonary shunt
This happens a few months to years later, and it involves diverting the blood returning to the heart from the top part of the body, towards the lung vessels. It involves connecting the superior vena cava (SVC) to the right pulmonary artery.

Stage 3- Fontan completion/ Total Cavopulmonary Connection (TCPC)
This happens some time after the second stage, usually by the end of childhood, but sometimes into early adult life. The operation involves directing the blood returning to the heart from the bottom part of the body towards the lung vessels as well. It is performed by connecting the Inferior vena cava (IVC) to the right pulmonary artery. The surgical techniques have varied greatly over the years. The commonest operation types now are the “lateral tunnel”, which uses part of the patient’s own atrium (collecting chamber), and the “extracardiac conduit”, which uses a prosthetic (Gortex) tube to divert blood to the lungs.

Both stages 2 and 3 happen through an incision through the centre of the chest (Sternotomy) and involve a heart bypass machine, which takes over the function of the heart and the lungs during the procedure. After the operation the sternotomy is closed using stainless steel wires, and surgical drains are positioned in the chest to allow any excess fluid to drain. The length of time in hospital can be from a few days to up to a few weeks, to allow the heart and lungs to adjust to the different pressures.

Do I need follow-up?
All patients with a Fontan operation require life-long follow up. Even though most patients will be well and symptom free for many years to come, others will develop significant complications such as pump failure (heart failure) and irregular heart rates (arrhythmias).

Some will require additional medication to help the heart work better. In the majority of patients, warfarin, a blood thinning medication which reduces the risk of blood clot formation, will be prescribed long term. The level of blood thinning (anticoagulation) will need to be monitored with a regular blood test called an INR (International Normalised Ratio). This will be organised by either your GP or the local haematology centre.

Is pregnancy possible?
Female patients can have successful pregnancies. However, these need to be planned carefully with close assessment and follow up by your obstetric centre and your cardiologist.

Warfarin in particular can be harmful to the foetus, especially in the first stages of pregnancy. Therefore, an alternative form of blood thinning medication may be necessary for stages of the pregnancy.

What is the long-term prognosis?
How long a heart with single ventricle can function well is not known. Some speculate that most single pump hearts will not work efficiently beyond 30 to 40 years. However, it has now been 30 years since the first successful Fontan operation and many improvements in the surgical technique and medical management have occurred. This could increase lifespan significantly.

When the pump fails heart transplantation will be an option.

Written by the Adult Congenital Team – Reviewed & updated April 2014