SECTION XIII - Fontan Operation

Part I - Background Information

Definition

The Fontan operation is a palliative procedure for patients with a functionally or anatomically single ventricle or complex malformation considered unsuitable for biventricular repair. There is diversion of all of the systemic venous return to the pulmonary arteries, usually without employing a subpulmonary ventricle.

Originally described for patients with tricuspid atresia, it has now been extended to most forms of single ventricle circulation.

There are numerous variations in the surgical approach. The most likely types of Fontan procedure to be encountered today are: 1) the direct RA-PA connection; 2) the total cavopulmonary connection (SVC to PA and IVC to PA through an intra-atrial tunnel); 3) the extra cardiac conduit (SVC to PA and IVC to PA through an external conduit); and 4) RA-RV through a valved conduit when RV size and function is adequate. The Fontan procedure may be done as a single or staged procedure (with a classic or bi-directional Glenn shunt performed as the first procedure, followed by the completion of the Fontan as a second procedure).

 
Part II - History and Management of Operated Patients

Patients who have had a Fontan operation are at risk from the following:

• Arrhythmias (194).
  - Atrial flutter/fibrillation is common and increases with increasing duration of follow-up. This can be associated with profound hemodynamic deterioration and needs prompt medical attention.
  - Heart block may also occur late and is often associated with hemodynamic deterioration.

When arrhythmias are present, an underlying hemodynamic cause should always be sought, and in particular, obstruction of the Fontan circuit needs to be excluded
Grade: C	Level: V	Ref: 195

• Thromboembolism (both systemic and pulmonary (196)
  - May be associated with atrial fibrillation.
  - May be related to a sluggish circulation, especially in the systemic veins and right atrium.
  - May be related to clotting abnormalities (e.g. protein C deficiency).
  
• Protein-losing enteropathy (PLE) (197)
  - Occurs in up to 10% of postoperative Fontan patients.
  - Is associated with ascites, peripheral edema, pleural and pericardial effusions and chronic diarrhea and an elevated stool 1 antitrypsin levels
  
• Progressive deterioration of ventricular function with or without AV valve regurgitation:
  - This may be part of the natural history of a patient with a single ventricle.
  
• Hepatic dysfunction:
  - Usually due to hepatic congestion.
  
• Right pulmonary vein compression/obstruction:
  - Due to compression from the enlarged right atrium or atrial baffle bulging into the left atrium.
• Cyanosis
  Worsening cyanosis may relate to worsening of ventricular function, the development of venous collateral channels draining to the left atrium or the development of pulmonary arteriovenous malformation (especially if a classic Glenn procedure remains as part of the Fontan operation).

 
Part III - Investigational Recommendations

Particular attention should be paid to:

• Ventricular function, both systolic and diastolic.
• Systemic AV valve regurgitation.
• Obstruction at the Fontan anastomosis.
• Residual shunts.
• The detection of thrombus within the right atrium.
• Increasing cyanosis.
• The development of atrial flutter or fibrillation.
• The detection of pulmonary arterio-venous malformations resulting in increased cyanosis (especially when a classic Glenn procedure remains).
• Serum protein and albumin levels.
• Hepatic function.

Investigations are directed towards postoperative sequelae and will vary according to the type of operation performed.

All patients should have at a minimum:

• A thorough clinical assessment.
• Oximetry at rest.
• ECG.
• Chest x-ray.
• Echo Doppler examination by an appropriately trained individual to assess systemic ventricular function, AV valve regurgitation, the presence or absence of residual shunts, the presence or absence of obstruction in the Fontan circuit, and of spontaneous contrast ('smoke') in the atrium.
• Serum protein and albumin measurement. If low, increased 1 anti-trypsin clearance in the stool documents the presence of PLE.

The diagnostic workup may require:

• Echocardiography with a bubble study to rule out pulmonary arterio-venous malformations.
• TEE if there is inadequate visualization of the Fontan anastomosis or to exclude thrombus in the atrium.
• MRI if the Fontan anastomosis cannot be assessed reliably by TEE or to assess ventricular function.
• Nuclear angiography to evaluate ventricular function.
• Complete heart catheterization if surgical re-intervention is planned or if adequate assessment of the hemodynamics is not obtained by non-invasive means. Even small gradients between the atrium and pulmonary artery (or outflow chamber) may suggest important obstruction across the Fontan anastomosis.

 
Part IV - Indications for Re-intervention

The following situations may warrant re-intervention: Residual atrial septal defect resulting in a significant right-to-left shunt, symptoms or cyanosis. Residual shunt secondary to a previous palliative surgical shunt or residual ventricle-to-pulmonary artery connection. Significant systemic AV valve regurgitation. Obstruction in the Fontan circuit. Development of venous collateral channels or pulmonary arterio-venous malformations. Development of sustained atrial flutter or fibrillation (an immediate attempt to restore sinus rhythm is crucial once right atrial thrombus has been excluded). Development of PLE. Pulmonary venous obstruction. High degree AV block or sick sinus syndrome necessitating pacemaker insertion. Planned closure of a fenestrated Fontan (trans-catheter).
Grade: C	Level: V	Refs: 198-201

 
Part V - Surgical/Interventional Options

Patients who require re-intervention should be treated at by ACHD cardiologists and congenital heart surgeons with appropriate training/experience
Grade: C	Level: V	Refs: 18,19

The following are possible intervention strategies:

• Patients with systemic AV valve regurgitation may require AV valve repair or replacement.
• Patients with residual shunts of significance may require closure of the residual shunt.
• Patients with significant obstruction at the Fontan anastomosis may be candidates for balloon angioplasty, stenting or surgical revision of the Fontan connection.
• Patients whose anastomosis is a valved conduit (RA-RV connection) may need Fontan revision or conversion to a different form of Fontan.
• Patients with venous collateral channels or arterio-venous malformation may need trans-catheter occlusion or conversion of a classic Glenn shunt to a bi-directional Glenn respectively.
• Patients with poorly controlled atrial flutter may be candidates for catheter ablation.
• Conversion of a classical Fontan to a lateral tunnel or external conduit with concomitant atrial maze procedure may be considered for the treatment of serious refractory atrial arrhythmias.
• If permanent pacing is required, epicardial A-V sequential pacing should be employed whenever possible to reduce the risk of thromboembolism.
• Patients with PLE may be candidates for creation of a fenestration in the atrial septum or revision of the Fontan. Alternatively, subcutaneous heparin, octreotide treatment and prednisone therapy have also been tried with variable success. No therapy seems more successful than the others.
• Transplantation may be necessary for systemic ventricular failure or intractable PLE.

The role of long-term anticoagulation is contentious. It is recommended that patients with a history of documented atrial flutter or fibrillation, fenestration in the Fontan connection, or spontaneous contrast ('smoke') in the right atrium on echocardiography be anticoagulated.
Grade: Consensus		Refs: 202,203

 
Part VI - Surgical/Interventional Outcomes

The Fontan operation remains a palliative, not a curative, procedure.

The reported average 10-year survival following Fontan operation is approximately 60% rising to 80% under ideal circumstances (204,205).

If PLE develops, the 5-year survival is approximately 50%. Reoperation following the Fontan procedure carries a high mortality, and with PLE the mortality may be as high as 75%. If obstruction in the Fontan circuit is the cause of the PLE, however, successful revision of the Fontan anastomosis may cure the PLE.

Usual causes of death are those related to ventricular failure, arrhythmias, reoperation and PLE.

 
Part VII - Arrhythmias

Atrial flutter/fibrillation is common (15-20% at 5 year follow up), and increases with duration of follow-up. It carries significant morbidity, can be associated with profound hemodynamic deterioration, and needs prompt medical attention. Patients at greater risk for atrial tachyarrhythmias are those who were operated on at an older age, with an atriopulmonary connection, with poor ventricular function, systemic atrioventricular valve regurgitation or increased pulmonary artery pressure. When atrial flutter/fibrillation are present, an underlying hemodynamic cause should always be sought, and in particular, evidence for obstruction of the Fontan circuit needs to be sought. Patients not anticoagulated, presenting in atrial flutter/fibrillation should have intravenous heparin started immediately and transesophageal echocardiography performed to rule out the presence of thrombus. Prompt attempts should be made to restore sinus rhythm if no thrombus is found and/or if there is hemodynamic compromise. Antiarrhythmic medications, alone or combined with an antitachycardia pacing device, and radiofrequency catheter ablation techniques, have had limited success. Surgical conversion from an atriopulmonary Fontan to a total cavopulmonary connection with concomitant atrial cryoablation (for flutter) therapy and maze procedure (for fibrillation) at the time of surgery has been reported with good short-term success (206). Patients with atrial arrhythmias (including paroxysmal) should be anticoagulated with coumadin long-term.

Sinus node dysfunction and complete heart block can occur and require pacemaker insertion. Endovenous ventricular pacing through the coronary sinus is possible but epicardial A-V sequential pacing should be employed whenever possible to reduce the risk of thromboembolism.

 
Part VIII - Pregnancy

Pregnancy carries additional risks to the mother because of the increased hemodynamic burden on the single ventricle and atrium. There is an increased risk of:

• Systemic venous congestion
• Deterioration in ventricular function.
• Worsened systemic AV valve regurgitation.
• Atrial arrhythmias.
• Thromboemboli.
• Paradoxical emboli if the Fontan is fenestrated.

Pregnancy is possible, however, with very careful patient selection, meticulous cardiac and obstetric supervision (207).

 
Part IX - Follow Up

All patients who have had a Fontan operation should be followed yearly by an ACHD cardiologist. Endocarditis prophylaxis is often recommended.

Grade: Consensus