Update on Surgical Practice and Current State on Fontan Conversion Surgery:...

The Fontan is a surgically created condition of severe chronic right heart failure with sequelae including venous hypertension, hepatic congestion, lymphatic congestion, restrictive lung disease, altered pulmonary vasculature, and single ventricle dysfunction.

Fontan takedown indications include low cardiac output and elevated CVP, frequently resulting in a progressive downward spiral.

Early revision is reasonable for Fontan failure if the anatomic problem is clearly established and the patient is not too debilitated.

Temporary mechanical support may be considered if the problem is primarily arrhythmias or predictably temporary ventricular dysfunction.

Late Fontan takedown might help hepatic congestion problems, but there are not many large series and outcomes are generally poor.

Bambino Gesù in Rome reported 18 Fontan takedowns over 25 years (1990-2015), with 2 in immediate postoperative period and 16 within 2 months of completion Fontan.

In the Bambino Gesù series, there were 17 early survivors, 3 underwent subsequent successful Fontan palliation, 4 underwent transplantation with 2 late survivors, and 10 remained with bidirectional Glenn physiology with reasonable saturations at median 7-year follow-up.

A European multi-institutional registry study (1971-2012) reported 38 Fontan takedowns with average time from Fontan to takedown of 0.6 years, early mortality of approximately 25%, five late deaths, and 44% reaching final endpoint by study conclusion.

Fontan conversion is primarily used for patients after atrial-pulmonary Fontan with atrial arrhythmias.

Fontan conversion always involves large atrial reduction combined with a maze operation or lesion set to prevent propagation of macro-reentrant circuits, which are the mechanism for most arrhythmias encountered.

The maze lesion set is accomplished by incision and use of a cryo catheter using frozen argon to achieve cryo lesions.

The lesion set for maze procedure must be altered to accommodate specific anatomy when patients lack typical tricuspid and mitral valves or have atypical coronary sinus position as in heterotaxy syndrome.

Data from Chicago shows that the more complete the arrhythmia procedure (biattrial maze vs. right atrial maze vs. isthmal ablation), the lower the risk of arrhythmia recurrence.

A more complete lesion set is indicated if performing the operation for arrhythmias.

The Chicago group reported low Fontan conversion mortality of 1.4%, while multi-center trials show early mortality around 10%.

Conditional survival after Fontan conversion appears similar between European experience and Chicago, suggesting mortality differences are primarily due to patient selection and execution of the operation.

A Japanese study examined prophylactic Fontan conversion in 7 arrhythmia-free atrial-pulmonary Fontan patients versus 25 with tachyarrhythmias, finding the prophylactic group had no late deaths and complete freedom from arrhythmias and protein-losing enteropathy.

It is uncertain whether the Japanese study justifies prophylactic Fontan conversion because it is unclear how those patients would have done if left alone.

The number of patients with atrial-pulmonary Fontan is decreasing, making Fontan conversion potentially a short-lived concern.

Candidates for Fontan conversion require preserved ventricular function and preserved end-organ function, as this is primarily an arrhythmia procedure.

Contraindications to Fontan conversion include protein-losing enteropathy, older age (related to elevation of end-diastolic pressure), ascites, and right or indeterminate ventricular morphology.

Biattrial arrhythmia operation has been identified as a risk factor for mortality in Fontan conversion.

In Australia and New Zealand, the number of atrial-pulmonary Fontans peaked in early 1990s and is now decreasing, with only extracardiac conduit Fontans performed since 2007.

The classic atrial-pulmonary Fontan conversion operation is anticipated to decrease in the next few years.

All Fontan patients being considered for transplant will have concerning pulmonary artery anatomy.

Pulmonary arteries in Fontan patients have been at low pressure throughout life and can be very delicate and thin-walled, with many aortopulmonary collaterals creating surgical challenges.

After Fontan heart excision and Glenn takedown, defects from the Glenn and extracardiac conduit commonly require repair, along with management of stented areas that are frequently not adequately dilated.

Hilar pulmonary arteries in Fontan patients are very thin, frequently manipulated at previous surgery, may be deserosalized or have adventitia removed, are prone to injury, and posterior injuries can be very challenging to repair.

The preferred strategy for pulmonary artery reconstruction in Fontan transplant is to perform this part of the operation with circulatory arrest, manipulating only central pulmonary arteries rather than hilar vessels.

Lymphatic circulation drains into central venous circulation, so venous hypertension results in lymphatic hypertension, which leads to protein-losing enteropathy and plastic bronchitis.

Most lymphatic drainage from the lower half of the body and left half of the trunk drains to the junction of the left internal jugular vein and innominate vein.

Doctor Hiroska published two case reports of innominate vein detachment from superior vena cava and anastomosis to low-pressure atrium, with improvement in protein-losing enteropathy.

Christian Kreutzer from Argentina has suggested creating a second detachment of proximal innominate vein from left internal jugular and left subclavian vein, then reconstructing innominate vein using Gore-Tex tube graft to avoid right-to-left shunting and cyanosis.

Fontan takedown is a life-saving operation for some patients with early failure.

Fontan conversion is an option for individuals with atrial-pulmonary Fontan, arrhythmias, and preserved function.

The future role of Fontan conversion is unclear as the number of individuals with atrial-pulmonary connections decreases over time.

Lymphatic decompression may provide palliation, but experience is very early.

The best hope for long-term survival probably rests with mechanical support and transplantation, requiring better understanding of support, sensitization, and immunosuppression.

In the case scenario of an 8-year-old with heterotaxy, post-op day 2 from fenestrated Fontan with low output, elevated CVP, oliguria, ascites, worsening acidosis, good ventricular function, mild AV valve regurgitation, sinus rhythm, and no pathway obstruction, the patient likely has elevation of end-diastolic pressure or increased pulmonary vascular resistance as cause of failure.

ECMO (either VA or VV) is unlikely to fix elevated end-diastolic pressure or increased pulmonary vascular resistance and may make them worse.

VV ECMO would not have much role in the face of low cardiac output.

While dialysis might be required at some point in acute Fontan failure, it is unlikely to reverse the process.

Poor ventricular function is a contraindication to Fontan conversion, while severe mitral regurgitation and left pulmonary artery stenosis are problems that can potentially be rectified.

Either people are not doing late Fontan takedown in adults, or if they are doing it, the results were not worthy of publication.

The degree of cyanosis after late Fontan takedown would be dramatic, even with an additional source of pulmonary blood flow or shunt.

Older patients who have been acyanotic will not do well with significant cyanosis, even if cardiac output is improved, despite such cyanosis being well tolerated in small children.