Fontan Procedure #2: Extracardiac Conduit Fontan

The extracardiac conduit Fontan is a contemporary form of total cavopulmonary connection (TCPC) in which the inferior vena cava (IVC) is connected to the pulmonary arteries through an external prosthetic conduit, usually a PTFE graft. In most patients, the superior vena caval pathway has already been established by a bidirectional Glenn or hemi-Fontan procedure; Fontan completion therefore adds the remaining IVC-to-pulmonary artery pathway.

The essential surgical principle is not merely to “connect the IVC to the pulmonary artery,” but to construct a durable, low-resistance venous pathway that can support passive pulmonary blood flow for decades.

1. Surgical Concept

In the extracardiac conduit Fontan, systemic venous blood from the IVC bypasses the right atrium and flows directly into the pulmonary arteries through a prosthetic extracardiac tube graft.

The operation typically involves the following steps:

1. Division of the IVC at the right atrial junction

The IVC is divided close to the RA–IVC junction.

2. Closure of the right atrial stump

The atrial side is closed securely, excluding the right atrium from the Fontan pathway.

3. Conduit–IVC anastomosis

A PTFE conduit, commonly 16–20 mm, is anastomosed to the divided IVC.

4. Pulmonary arteriotomy

An opening is created in the pulmonary artery, usually at a site that allows the smoothest conduit orientation.

5. Conduit–PA anastomosis

The conduit is trimmed to an appropriate length and anastomosed to the pulmonary artery. If the pulmonary artery is small, distorted, or stenotic, patch augmentation may be required.

The result is a complete cavopulmonary circuit in which both SVC and IVC return pass directly into the pulmonary arteries without a subpulmonary ventricle.

2. Hemodynamic Principle

The Fontan circulation is fundamentally a passive venous circulation. There is no right ventricle to pump blood through the lungs. Therefore, systemic venous pressure must overcome pulmonary vascular resistance, pulmonary artery resistance, conduit resistance, and ventricular filling pressure.

For this reason, the success of the extracardiac Fontan depends on several critical conditions:

• Low pulmonary vascular resistance
• Unobstructed branch pulmonary arteries
• Preserved ventricular systolic and diastolic function
• Minimal atrioventricular valve regurgitation
• Low atrial and ventricular filling pressures
• A smooth, non-obstructed Fontan pathway

In this circulation, geometry becomes physiology. A short, gently curved, non-kinked conduit can reduce energy loss, whereas angulation, narrowing, compression, or excessive length may increase resistance and impair long-term Fontan performance.

3. Advantages of the Extracardiac Conduit Fontan

1. Avoidance of extensive atrial manipulation

Unlike the atriopulmonary Fontan or lateral tunnel Fontan, the extracardiac conduit avoids placing a large baffle within the atrium. This reduces atrial suture lines, atrial distension, and atrial distortion.

This feature is one of the main reasons the extracardiac conduit Fontan has been associated with a lower risk of atrial arrhythmias compared with older Fontan modifications and, in some contemporary comparisons, compared with lateral tunnel Fontan [1].

2. Reproducible surgical geometry

The extracardiac conduit provides a relatively standardized route from the IVC to the pulmonary artery. This can be technically advantageous, especially when the atrial anatomy is complex or when minimizing atrial manipulation is desirable.

3. Smooth systemic venous return

When the conduit is appropriately sized and aligned, IVC flow can be directed into the pulmonary arteries with relatively favorable geometry. The goal is to avoid turbulence, stagnation, or preferential flow streaming that may compromise pulmonary blood flow distribution.

4. Lower atrial arrhythmia substrate

Atrial arrhythmias remain an important long-term complication after Fontan palliation. However, the extracardiac approach may reduce arrhythmogenic substrate by avoiding large intra-atrial suture lines and reducing chronic atrial dilation. A recent multicenter 15-year comparison reported lower atrial arrhythmia burden after extracardiac conduit Fontan compared with lateral tunnel Fontan [1].

4. Limitations of the Extracardiac Conduit Fontan

1. No intrinsic growth potential

The conduit is prosthetic and does not grow. This is one of the most important conceptual disadvantages of the extracardiac approach. As the patient grows, a conduit that was adequate at implantation may become relatively restrictive, especially if implanted at a small size.

Longitudinal imaging studies have shown that the autologous vessels above and below the Gore-Tex graft can grow, but the prosthetic graft itself remains fixed in size [2]. More recent pathway-growth analyses suggest that extracardiac conduits may demonstrate less favorable growth characteristics and may develop increasing power loss over time compared with lateral tunnel pathways [3].

2. Risk of thrombosis

The Fontan circulation is inherently thrombogenic. Contributing factors include low-velocity venous flow, prosthetic material, altered coagulation profiles, endothelial dysfunction, and venous stasis. Coagulation abnormalities may evolve throughout staged single-ventricle palliation, and thromboprophylaxis remains an important long-term management issue [4].

Aspirin and warfarin have both been used after Fontan completion. A multicenter randomized trial comparing aspirin with heparin/warfarin after Fontan surgery showed that thromboembolic events remain a significant concern despite prophylaxis, and no single strategy completely eliminates risk [5]. In current practice, antithrombotic selection is usually individualized according to anatomy, age, conduit type, fenestration status, arrhythmia, prior thrombosis, ventricular function, and institutional protocol.

3. Potential conduit stenosis or distortion

Although the conduit provides a clean extracardiac pathway, it may develop obstruction due to narrowing, kinking, compression, thrombus, pseudointimal formation, or distortion at either anastomosis. Therefore, long-term surveillance with echocardiography, CMR, CT, or catheterization is essential.

4. Fenestration considerations

Fenestration can be created between the extracardiac conduit and the atrium, but it is not as naturally integrated into the atrial pathway as in some lateral tunnel constructions. The decision to fenestrate depends on pulmonary vascular resistance, ventricular function, AV valve regurgitation, pulmonary artery anatomy, and expected postoperative Fontan pressure.

5. Extracardiac Conduit versus Lateral Tunnel Fontan

The extracardiac conduit and lateral tunnel Fontan are both forms of TCPC, but they differ in surgical construction and long-term biological behavior.

Extracardiac conduit Fontan

Strengths

• Less atrial manipulation
• Fewer atrial suture lines
• Potentially lower atrial arrhythmia risk
• Technically reproducible extracardiac pathway

Weaknesses

• Prosthetic material
• No conduit growth
• Risk of conduit thrombosis or stenosis
• Possible increase in power loss over time

Lateral tunnel Fontan

Strengths

• Partial use of native tissue
• Some potential for pathway growth
• Fenestration can be technically straightforward
• May show more favorable growth characteristics in some imaging studies

Weaknesses

• More atrial involvement
• Greater atrial suture burden
• Potentially higher atrial arrhythmia substrate
• More dependence on atrial anatomy and geometry

Recent comparative data suggest a trade-off: extracardiac conduit Fontan may offer a lower atrial arrhythmia burden, whereas lateral tunnel Fontan may have more favorable growth and lower progression of pathway-related power loss in selected cohorts [1, 3].

6. Long-Term Outcomes

Modern Fontan survival has improved substantially, and many patients now survive into adolescence and adulthood. In a large Pediatric Heart Network cohort, transplant-free survival over 12 years was approximately 90% [6]. However, long-term survival does not imply normal physiology. Fontan patients remain at risk for progressive circulatory failure, arrhythmia, exercise intolerance, thromboembolism, protein-losing enteropathy, plastic bronchitis, liver disease, renal dysfunction, and need for reintervention.

Large registry data demonstrate that reintervention is common over time. In the Australian and New Zealand Fontan Registry, the cumulative burden of reintervention was substantial, emphasizing that Fontan completion should be viewed not as a final cure but as the beginning of lifelong surveillance [7].

Functional outcome is also heterogeneous. Long-term follow-up studies have shown that exercise capacity, ventricular performance, atrial function, and end-organ status become increasingly important determinants of clinical trajectory [6, 8, 9].

7. Fontan-Associated Liver Disease and Systemic Consequences

The extracardiac conduit may optimize the pathway geometry, but it does not eliminate the fundamental physiology of Fontan circulation: chronically elevated systemic venous pressure and relatively reduced cardiac output. These features contribute to systemic complications, including Fontan-associated liver disease.

Fontan-associated liver disease is now recognized as a near-universal long-term consequence of Fontan physiology, driven by chronic hepatic venous congestion, reduced forward flow, and progressive fibrosis risk [10]. Therefore, long-term management of extracardiac Fontan patients requires a multidisciplinary approach, including surveillance of the heart, pulmonary arteries, conduit, rhythm, coagulation status, liver, kidneys, lymphatics, and exercise capacity.

8. Practical Surgical Pearls

1. The conduit should be large enough for long-term flow but not excessively oversized.

Oversizing may promote sluggish flow and thrombosis; undersizing may create late obstruction.

2. The conduit should follow a smooth, natural curve.

Sharp angulation, twisting, or compression increases energy loss.

3. The pulmonary artery anastomosis must be generous.

Branch pulmonary artery stenosis or a small arteriotomy can compromise the entire Fontan circuit.

4. The IVC anastomosis should be wide and tension-free.

Narrowing at the IVC-conduit junction creates a fixed inflow obstruction.

5. Fontan completion is a hemodynamic operation, not only an anatomic operation.

The surgical construction must be judged by its ability to preserve passive venous flow with minimal resistance.

Summary

The extracardiac conduit Fontan is a widely used modern TCPC strategy that routes IVC blood to the pulmonary arteries through an external PTFE conduit. Its major advantages are avoidance of extensive atrial manipulation, reproducible geometry, smooth systemic venous routing, and reduced atrial arrhythmia substrate. Its major disadvantages are prosthetic material, thrombosis risk, absence of growth potential, and possible conduit-related obstruction or energy loss over time.

The central concept is that the extracardiac Fontan is not simply a surgical connection. It is the construction of a long-term passive venous pathway. In this circulation, small geometric imperfections can become meaningful physiological burdens. Therefore, conduit size, length, orientation, anastomotic geometry, pulmonary artery adequacy, and lifelong surveillance all directly influence the durability of the Fontan circulation.

References

[1] Seese L, Schiff MD, Morell VO, Tran M, Arora G, Olivieri LJ, Follansbee CW, Christopher A, Kreutzer J, Fogel M, Medina MC, Diaz-Castrillon C, da Fonseca da Silva L, da Silva JD, Rathod R, Alsaied T. Extracardiac conduit Fontan versus lateral tunnel Fontan: a multicenter comparison of long-term outcomes. Ann Thorac Surg. 2025;120(6):1115-1123.

[2] Ochiai Y, Imoto Y, Sakamoto M, Sese A, Tsukuda M, Watanabe M, Ohno T, Joo K. Longitudinal growth of the autologous vessels above and below the Gore-Tex graft after the extracardiac conduit Fontan procedure. Eur J Cardiothorac Surg. 2010;37(5):996-1001.

[3] Verma A, Dafflisio GJ, Govindarajan V, Rathod R, Hammer P, Hoganson D, Emani S. Growth of the Fontan pathway and its association with long-term outcomes. J Thorac Cardiovasc Surg. 2025;170(6):1769-1778.e3.

[4] Odegard KC, Zurakowski D, DiNardo JA, Castro RA, McGowan FX Jr, Neufeld EJ, Laussen PC. Prospective longitudinal study of coagulation profiles in children with hypoplastic left heart syndrome from stage I through Fontan completion. J Thorac Cardiovasc Surg. 2009;137(4):934-941.

[5] Monagle P, Cochrane A, Roberts R, Manlhiot C, Weintraub R, Szechtman B, Hughes M, Andrew M, McCrindle BW. A multicenter, randomized trial comparing heparin/warfarin and acetylsalicylic acid as primary thromboprophylaxis for 2 years after the Fontan procedure in children. J Am Coll Cardiol. 2011;58(6):645-651.

[6] Atz AM, Zak V, Mahony L, Uzark K, D’Agincourt N, Goldberg DJ, Williams RV, Breitbart RE, Colan SD, Burns KM, Margossian R, Henderson HT, Korsin R, Marino BS, Daniels K, McCrindle BW. Longitudinal outcomes of patients with single ventricle after the Fontan procedure. J Am Coll Cardiol. 2017;69(22):2735-2744.

[7] Daley M, du Plessis K, Zannino D, Hornung T, Disney P, Cordina R, Grigg L, Radford D, Bullock A, d’Udekem Y. Reintervention and survival in 1428 patients in the Australian and New Zealand Fontan Registry. Heart. 2020;106(10):751-757.

[8] Atz AM, Zak V, Mahony L, Uzark K, Shrader P, Gallagher D, Paridon SM, Williams RV, Breitbart RE, Colan SD, Kaltman JR, Margossian R, Pasquali SK, Allen KR, Lai WW, Korsin R, Marino BS, Mirarchi N, McCrindle BW. Survival data and predictors of functional outcome an average of 15 years after the Fontan procedure: the Pediatric Heart Network Fontan cohort. Congenit Heart Dis. 2015;10(1):E30-E42.

[9] van der Ven JPG, Alsaied T, Juggan S, Bossers SSM, van den Bosch E, Kapusta L, Kuipers IM, Kroft LJM, ten Harkel ADJ, van Iperen GG, Rathod RH, Helbing WA. Atrial function in Fontan patients assessed by CMR: relation with exercise capacity and long-term outcomes. Int J Cardiol. 2020;312:56-61.

[10] Daniels CJ, Bradley EA, Landzberg MJ, Aboulhosn J, Beekman RH 3rd, Book W, Gurvitz M, John A, John BV, Marelli A, Marino BS, Minich LL, Poterucha J, Rand E, Veldtman G. Fontan-associated liver disease: proceedings from the American College of Cardiology Stakeholders Meeting, October 1 to 2, 2015, Washington DC. J Am Coll Cardiol. 2017;70(25):3173-3194.