Review
Fontan Circulation: Success or Failure?

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Abstract

Fontan surgery represents a milestone in the evolution of congenital heart disease management. It achieved the seemingly improbable (ie, restoration of a noncyanotic state by entirely bypassing the subpulmonary ventricle). In so doing, it has allowed a generation of children who may have otherwise succumbed to their severe congenital heart defect to survive to adulthood. Perfect univentricular physiology is, however, an elusive goal. The Fontan circulation inherently represents a hemodynamic compromise that results in a catalog of potential multiorgan complications. In this review, we explore current knowledge regarding pathophysiology of the failing Fontan, its varied clinical manifestations, and potential therapeutic options. Failure of the Fontan circulation is broadly divided into 3 overlapping categories: ventricular dysfunction, systemic complications of Fontan physiology, and chronic Fontan failure. As long as the Fontan operation continues to serve as the paradigm of care for patients with univentricular hearts, efforts must be directed toward supporting this dynamic circulation that progressively declines in efficiency with age. Continued research in therapies is needed for univentricular dysfunction and systemic complications of Fontan palliation, including potential uses of mechanical support as a bridge to transplantation or as a neosubpulmonary ventricle. Fontan patients remain a major challenge to the medical and surgical community as a whole. Multicentre and multidisciplinary efforts to improve the density and depth of experiences might lead to a better appreciation for, and management of, Fontan failure and its ramifications.

Résumé

L’opération de Fontan est une étape importante dans l’évolution de la prise en charge de la cardiopathie congénitale. Elle a atteint ce qui était apparemment improbable (c.-à-d. la restauration d’un état non cyanotique en contournant entièrement le ventricule sous-pulmonaire). Ainsi, elle a permis à une génération d’enfants qui auraient autrement succombé à leur malformation cardiaque congénitale grave de survivre jusqu’à l’âge adulte. Cependant, la physiologie univentriculaire parfaite est un objectif difficile à atteindre. La circulation de type Fontan représente intrinsèquement un compromis hémodynamique qui entraîne des complications potentielles de plusieurs organes. Dans cette revue, nous explorons les connaissances actuelles en ce qui concerne la physiopathologie en cas d’échec de l’opération de Fontan, ses diverses manifestations cliniques et les options thérapeutiques potentielles. L’échec de la circulation de Fontan est généralement divisé en 3 catégories qui se recoupent : le dysfonctionnement ventriculaire, les complications systémiques de la physiologie de Fontan et l’insuffisance chronique de Fontan. Tant que l’opération de Fontan sera inscrite dans le paradigme de soins des patients ayant un cœur univentriculaire, nous devrons concentrer nos efforts au maintien de cette circulation dynamique qui décline progressivement en efficacité avec l’âge. La recherche continue de traitements sur le dysfonctionnement univentriculaire et les complications systémiques de la chirurgie palliative de Fontan, incluant l’utilisation potentielle de soutiens mécaniques comme pont vers la transplantation ou comme un ventricule néo-sous-pulmonaire est nécessaire. Les patients ayant subi une opération de Fontan demeurent un défi important pour l’ensemble de la communauté médicale et chirurgicale. Les efforts multicentriques et multidisciplinaires pour améliorer la concentration et l’envergure des expériences pourraient conduire à une meilleure appréciation et une meilleure prise en charge de l’échec de l’opération de Fontan et ses ramifications.

Section snippets

The Fontan Procedure

In the first iteration of the Fontan procedure, the right atrium was isolated (eg, closure of atrial septal defect, oversewing of the tricuspid annulus), and its appendage anastomosed to the pulmonary artery.5 Several modifications were subsequently proposed in an effort to improve hemodynamic function and thwart progressive atrial dilation (Fig. 1). The lateral tunnel Fontan consists of suturing the superior vena cava to the right pulmonary artery and directing inferior vena caval flow to the

Mortality

The perioperative mortality rate has declined steadily to < 2% in the modern era, in part because of improved patient selection, better adjustment of pulmonary blood flow, and the staged approach to Fontan palliation, with a previous bidirectional Glenn shunt.8 Reported predictors of perioperative mortality include an earlier postoperative era, elevated preoperative pulmonary artery pressures (≥ 15 mm Hg), a common atrioventricular valve, and hypoplastic left heart syndrome.7, 8, 9 In

The Failing Fontan

Late Fontan failure might present gradually and insidiously over years. The absence of overt symptoms or ascites is insufficient evidence for optimal hemodynamic status. Fontan patients have lived with less than ideal cardiac output their entire lives and might not recognize symptoms or demonstrate overt manifestations of progressive decline in functional status until deterioration is quite advanced. Detection of hemodynamic abnormalities is, therefore, complicated by the lack of heralding

Ventricular Dysfunction

In a cross-sectional analysis of 546 children with Fontan procedures, 27% had abnormal ventricular ejection fractions and 72% had diastolic dysfunction.13 The prevalence of systolic and diastolic ventricular dysfunction continues to increase in adulthood, particularly in those with morphologic right ventricles and/or previous ventriculotomy incisions during staged palliation.14, 15 Chronic hypoxemia and ventricular volume loading early in life, as associated with staged palliation, might

Growth

Failure to gain weight appropriately might be an early indicator of suboptimal cardiac output in childhood.20 Growth failure should prompt a thorough investigation of hemodynamic status and early efforts to address residual obstructions or valve abnormalities with catheter or surgical interventions.

Cyanosis

Fontans might be fenestrated to help decompress the circuit in the early postoperative period and ease adaptation to the new circulation. However, this hemodynamic advantage is obtained at the

Chronic Fontan Failure

Fontan physiology is characterized by progressively decreasing cardiac output and increasing central venous pressure over time. The average peak oxygen consumption ranges from 19 to 28 mL/kg per minute, or 50%-60% of predicted values.83 By midadolescence, exercise capacity is typically reduced to approximately 66% of normative values.84 Beyond adolescence, exercise tolerance continues to fall at a rate of about 2.6% per year.85 When exercise capacity crosses a threshold of approximately 45% of

Conclusion

Patients with univentricular hearts and Fontan palliation face a unique set of long-term challenges. Though the congenital heart community has successfully created a generation of survivors, failures of this unnatural circulation have become increasingly evident. As long as the Fontan operation serves as the paradigm of care for patients with univentricular hearts, intense efforts will be required to improve our ability to support this circulation. Complications are complex, involve multiple

Funding Sources

Dr Khairy is supported by a Canada Research Chair in Adult Congenital Heart Disease and Electrophysiology.

Disclosures

The authors have no conflicts of interest to disclose.

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