High-Risk Indicators for Fontan Completion – #2 Anatomic and Surgical History

Pre-Fontan catheterisation provides a snapshot of current pressures and saturations, but anatomic substrate and surgical history often carry equal or greater prognostic weight. Contemporary Fontan guidelines emphasise that decisions should integrate not only hemodynamics, but also residual lesions, prior interventions, and evidence of early pulmonary or lymphatic injury.[1]

Among these historical features, three deserve particular attention:

• Pulmonary artery (PA) stenting or surgical reconstruction after Glenn
• Pulmonary venous (PV) interventions after Glenn
• A neonatal history of intact or severely restrictive atrial septum

Each of these signals underlying disease of the pulmonary vascular or venous bed and a circulation that has already required substantial structural manipulation before Fontan.

1. Pulmonary Artery Interventions Post-Glenn

Definition

• Balloon angioplasty or stenting of branch PAs
• Surgical patch augmentation, re-do PA reconstruction, or unifocalisation performed after a bidirectional Glenn

Pathophysiologic concerns

1. Asymmetric or obstructed pulmonary blood flow
• Branch PA stenosis or distortion diverts flow to one lung and underperfunds the other.
• This creates segmental differences in PVR and energy loss within the cavopulmonary circuit, undermining the passive flow that a Fontan circulation depends on.
2. Marker of abnormal pulmonary vascular development
• The need for repeated PA interventions often reflects more than a single anatomic kink: previous shunts, abnormal arborisation, or intrinsic arteriopathy.
• Such lungs are more prone to elevated PVR and impaired compliance, which are well-recognised contraindications to Fontan completion.[1,2]
3. Technical complexity at Fontan completion
• Stents and bulky patch material frequently lie at or near the intended anastomotic site for an extracardiac conduit or lateral tunnel.
• Dense scar tissue and residual stenosis can make it difficult to construct a smooth, unobstructed cavopulmonary pathway, sometimes necessitating extensive re-do reconstruction at the time of Fontan.

Practical approach

• Obtain detailed cross-sectional imaging (CT or MRI) and angiography to confirm:
• Symmetric lung perfusion
• Adequate calibre of both branch PAs
• Freedom from significant stenosis at the future Fontan pathway
• Consider staged PA reconstruction before Fontan if anatomy is borderline, rather than accepting a compromised pathway.

2. Pulmonary Venous Interventions Post-Glenn

Definition

• Balloon dilation or stenting of pulmonary veins
• Surgical repair (including sutureless techniques) for pulmonary vein stenosis (PVS) after Glenn

Why pulmonary venous disease is a major red flag

1. Pulmonary venous hypertension in a high-venous-pressure system
• The Fontan circuit already operates at elevated systemic venous pressure.
• Superimposed PV obstruction raises left atrial and pulmonary venous pressure, sharply reducing the transpulmonary gradient and predisposing to low cardiac output and severe congestion.
2. Aggressive, recurrent disease
• In single-ventricle patients with total anomalous pulmonary venous connection (TAPVC) or acquired PVS, survival remains substantially worse than for other single-ventricle lesions, largely because of recurrent venous obstruction despite modern repair strategies.[3–5]
• Series of functional single ventricles with extracardiac TAPVC report modest long-term survival and frequent need for reintervention, underscoring the chronic nature of PV disease in this setting.[4,5]
3. Pulmonary parenchymal and lymphatic injury
• Chronic pulmonary venous hypertension leads to interstitial fibrosis, small-vessel remodeling, and lymphatic dilation.
• When Fontan venous pressures are added on top of this, patients are at high risk for persistent pleural effusions, plastic bronchitis, and protein-losing enteropathy, classic manifestations of failing Fontan physiology.[1,3]

Practical approach

• Treat a history of PV intervention as a major risk factor rather than a minor technical detail.
• Ensure:
• Careful angiography and cross-sectional imaging of pulmonary veins
• Multidisciplinary review (surgery, interventional cardiology, imaging) regarding the durability of venous repair
• In patients with recurrent or bilateral PVS, many centres regard Fontan as a relative or absolute contraindication, and early transplant evaluation may be more appropriate than proceeding to completion.[3–5]

3. History of Intact or Severely Restrictive Atrial Septum

In neonates with single-ventricle physiology—especially hypoplastic left heart syndrome (HLHS)—an intact or highly restrictive atrial septum (IAS) leads to extreme pulmonary venous hypertension in utero and immediately after birth. Pathologic studies show marked pulmonary venous congestion, muscularisation of small arteries, and early lymphatic remodeling in this subgroup.[6]

Early outcomes

• Multiple series confirm that HLHS with IAS represents one of the highest-risk phenotypes within HLHS, accounting for a small minority of cases but a disproportionate share of mortality.[6–9]
• Even with rapid postnatal or fetal atrial decompression, hospital and interstage mortality remain significantly higher than in HLHS without IAS.[7–9]
• Contemporary surgical cohorts report hospital survival rates after stage I palliation that, while improving, still lag behind standard HLHS populations.[8,9]

Long-term consequences for the Fontan pathway

• Survivors carry the “imprint” of early pulmonary venous and lymphatic injury:
• Higher baseline PVR and lower pulmonary vascular compliance
• Persistent abnormalities of the lymphatic system, predisposing to chylothorax, plastic bronchitis, and protein-losing enteropathy once exposed to Fontan venous pressures[1,9,10]
• Editorial and review articles emphasise that HLHS with IAS should be viewed as a distinct risk phenotype along the entire staged pathway, not only at birth.[9,10]

Thus, a neonatal history of intact or severely restrictive atrial septum is a powerful “embedded red flag” in the surgical history: even apparently acceptable pre-Fontan hemodynamics may underestimate the fragility of the pulmonary vascular and lymphatic beds.

4. Broader Context: Lesion-Specific Anatomical Risk (Example – PA/IVS)

The importance of anatomic substrate is not unique to HLHS with IAS. In pulmonary atresia with intact ventricular septum (PA/IVS), large registry data show that:

• Overall 20-year transplant-free survival is about two-thirds, largely limited by infant and interstage mortality.[11]
• Among patients who survive to definitive repair—whether 2-ventricle, 1.5-ventricle, or Fontan—long-term survival is excellent, approaching 90–98%.[11]

However, within the Fontan subgroup, right-ventricle–dependent coronary circulation (RVDCC) remains a potent anatomic risk factor: Fontan survivors with RVDCC have substantially higher late mortality and sudden death compared with those without coronary dependence.[12]

This PA/IVS example reinforces the central message of this section: anatomy and prior surgical history can define risk in ways that are not fully captured by a single pre-Fontan catheterisation.

5. Using Anatomic and Surgical History as a Risk Map

When planning Fontan completion, past interventions and neonatal anatomy should be read as a risk map layered onto current hemodynamics:

1. Pulmonary artery interventions post-Glenn
• Suggest complex PA anatomy, asymmetric perfusion, and potential technical difficulty in creating an unobstructed cavopulmonary pathway.
• Require meticulous imaging and, if necessary, additional PA reconstruction before Fontan.[1,2]
2. Pulmonary venous interventions post-Glenn
• Indicate a fragile pulmonary venous bed with high odds of recurrent obstruction and pulmonary venous hypertension.
• Often justify viewing Fontan completion with great caution and considering transplant options early.[3–5]
3. History of intact or highly restrictive atrial septum
• Marks a lung and lymphatic system exposed to severe early injury, associated with higher interstage mortality and greater vulnerability to chronic venous hypertension.[6–10]

Patients with one or more of these features merit:

• Comprehensive, often serial, pre-Fontan imaging and catheterisation
• A low threshold for additional PA/PV repair or staged strategies (e.g., delayed or fenestrated Fontan)
• Honest discussion with families about elevated risk of Fontan failure, late complications, and the potential need for transplant, rather than assuming the Fontan pathway is inevitable.

References

[1] Rychik J, Atz AM, Celermajer DS, Deal BJ, Gatzoulis MA, Gewillig MH, et al. Evaluation and management of the child and adult with Fontan circulation: A scientific statement from the American Heart Association. Circulation. 2019;140(6):e234-e284. PubMed

[2] Salik I, Mehta B, Ambati S. Bidirectional Glenn procedure or hemi-Fontan. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025. ncbi.nlm.nih.gov

[3] Gaynor JW, Collins MH, Rychik J, Gaughan JP, Spray TL, Rychik J, et al. Long-term outcome of infants with single ventricle and total anomalous pulmonary venous connection. J Thorac Cardiovasc Surg. 1999;117(3):506-513. PubMed

[4] Nakata T, Fujimoto Y, Hirose K, Osaki M, Tosaka Y, Ide Y, et al. Functional single ventricle with extracardiac total anomalous pulmonary venous connection. Eur J Cardiothorac Surg. 2009;36(1):49-56. OUP Academic

[5] Hoashi T, Kagisaki K, Oda T, Kitano M, Kurosaki K, Shiraishi I, et al. Long-term results of treatments for functional single ventricle associated with extracardiac type total anomalous pulmonary venous connection. Eur J Cardiothorac Surg. 2013;43(5):965-970. OUP Academic

[6] Rychik J, Rome JJ, Collins MH, DeCampli WM, Spray TL. The hypoplastic left heart syndrome with intact atrial septum: Atrial morphology, pulmonary vascular histopathology, and outcome. J Am Coll Cardiol. 1999;34(2):554-560. Thieme

[7] Vlahos AP, Lock JE, McElhinney DB, van der Velde ME. Hypoplastic left heart syndrome with intact or highly restrictive atrial septum: Outcome after neonatal transcatheter atrial septostomy. Circulation. 2004;109(19):2326-2330. Thieme

[8] Vida VL, Bacha EA, Larrazabal A, Gauvreau K, Thiagarajan R, Fynn-Thompson F, et al. Hypoplastic left heart syndrome with intact or highly restrictive atrial septum: Surgical experience from a single center. Ann Thorac Surg. 2007;84(2):581-585. PubMed

[9] Sood V, Zampi JD, Romano JC. Hypoplastic left heart syndrome with an intact atrial septum. JTCVS Open. 2020;1:51-56. PubMed

[10] Alsoufi B. It takes a village to manage a child with hypoplastic left heart syndrome and an intact atrial septum. JTCVS Open. 2020;1:57-59. PMC

[11] Wright LK, Knight JH, Thomas AS, Oster ME, St Louis JD, Kochilas LK. Long-term outcomes after intervention for pulmonary atresia with intact ventricular septum. Heart. 2019;105(13):1007-1013. PubMed

[12] Elias P, Poh CL, du Plessis K, Zannino D, Rice K, Radford DJ, et al. Long-term outcomes of single-ventricle palliation for pulmonary atresia with intact ventricular septum: Fontan survivors remain at risk of late myocardial ischaemia and death. Eur J Cardiothorac Surg. 2018;53(6):1230-1236.