ReviewFontan Circulation: Success or Failure?
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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Cited by (72)
Late Fontan failure in adult patients is predominantly associated with deteriorating ventricular function
2021, International Journal of CardiologyCitation Excerpt :However, to date, there is only limited data supporting the view of PVR as the main contributor to late Fontan failure. Moreover, it has become increasingly evident that there may be profoundly differing hemodynamic phenotypes of Fontan failure. [5,19,20] With limited therapeutic options to offer patients with failing Fontan, identifying the most prevalent hemodynamic restriction might allow a more timely and targeted initiation of therapies in order to delay the most likely inevitable hemodynamic demise of the Fontan circulation.
Late complications following the Fontan operation
2018, Diagnosis and Management of Adult Congenital Heart Disease: Third EditionFontan Failure: Phenotypes, Evaluation, Management and Future Directions
2022, Cardiology in the Young
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