Show notes
CardioNerds (Amit Goyal and Daniel Ambinder), ACHD series co-chair Dr. Daniel Clark (Vanderbilt University), and ACHD FIT lead Dr. Danielle Massarella (Toronto University Health Network) join ACHD expert Dr. Yuli Kim (Associated Professor of Medicine & Pediatrics at the University of Pennsylvania), to discuss single ventricular heart disease and Fontan palliation. They cover the varied anatomical conditions that can require 3-step surgical palliation culminating in the Fontan circulation, which is characterized by passive pulmonary blood flow, high venous pressures, and low cardiac output. Audio editing by Dr. Gurleen Kaur (Director of the CardioNerds Internship and CardioNerds Academy Fellow).
The CardioNerds Adult Congenital Heart Disease (ACHD) series provides a comprehensive curriculum to dive deep into the labyrinthine world of congenital heart disease with the aim of empowering every CardioNerd to help improve the lives of people living with congenital heart disease. This series is multi-institutional collaborative project made possible by contributions of stellar fellow leads and expert faculty from several programs, led by series co-chairs, Dr. Josh Saef, Dr. Agnes Koczo, and Dr. Dan Clark.
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Pearls • Notes • References • Guest Profiles • Production Team
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Pearls
There are various forms of unpalliated ‘single ventricle’ congenital heart disease. The three main hemodynamic issues that need to be addressed in any form are unbalanced flow, pulmonary over-circulation, and blood mixing.
The Fontan palliation is a series of operations for congenital heart disease patients in whom biventricular repair is not feasible.
In the completed Fontan circulation, systemic venous blood is surgically routed directly to the lungs, effectively bypassing the heart, and creating passive pulmonary blood flow.
The hallmarks of the Fontan circulation (and Fontan failure) are elevated central venous pressure and low cardiac output.
Patients with Fontan circulation may experience significant morbidity in the long term from both cardiac and non-cardiac sequelae, and require lifelong specialist care.
Show notes
1. Why do some patients require Fontan palliation?
Many different types of anatomies may ultimately require single ventricular palliation via the Fontan procedure due to inadequate biventricular function to support both pulmonary and systemic circulations. Some examples include Tricuspid Atresia (hypoplastic RV), Double Inlet Left Ventricle (DILV; hypoplastic RV), Hypoplastic Left Heart Syndrome (HLHS; hypoplastic LV), and atrioventricular septal defects (AVSD; either RV or LV may be inadequate based on “commitment” of the common AV valve). The Fontan procedure was first described in 1971; at this time, mortality of single ventricular patients exceeded 90% in the first year of life.
2. What are the stages of Fontan palliation?
Effective pulmonary blood flow/balancing flow to the pulmonary and systemic circulations: for many conditions, this involves retrograde pulmonary blood flow from a systemic - PA shunt (i.e. Blalock-Taussig-Thomas “BTT” shunt in which the subclavian artery is turned down and anastomosed to the pulmonary artery). In infants, the pulmonary vascular resistance (PVR) is high perinatally and gradually lowers over the first 3 months of life to adult levels with exposure to the atmosphere’s natural pulmonary vasodilator: oxygen. Thus, in the first 3 months of life babies have an intrinsic PVR that is too high to directly connect the venous system to the lung arteries and thereby require staged surgeries. Protect the pulmonary vasculature from overcirculation: ultimately, the goal of single ventricular palliation is rerouting systemic venous drainage directly to the pulmonary vasculature passively, without a cardiac pumping chamber. This volume unloads the common ventricle and allows it a better chance to function over the lifespan by pumping only to a single circuit: the systemic vascular bed. Thus, steps 2 and 3 of Fontan palliation are passive head/neck venous connection to the pulmonary arteries (now typically accomplished with the modified bidirectional Glenn operation that anastomoses the SVC to the RPA typically) and finally total cavopulmonary connection by the Fontan conduit connecting the lower body’s venous return from the IVC to the Fontan tunnel and up to the RPA.
3. What is the ultimate “plumbing” of Fontan circulation?
Venous blood from the head/neck is connected directly from the SVC to the right pulmonary artery (RPA; typically, via a Glenn operation).Venous blood from the legs, abdomen/pelvis and lower body is connected directly to the RPA via the Fontan tunnel.In sum, the pulmonary blood flow enters passively, without a pump to send venous blood to the lungs.
http://pted.org/?id=fontan3
4. What are the types of Fontan?
The classic Fontan operation involved a direct venous connection to the right atrium with an atriopulmonary connection to the RPA.Contemporary era Fontan operations typically involve the lateral tunnel (LT) or extracardiac conduit. The LT incorporates pericardium in the creation of the Fontan conduit along the surface of the heart, while the extracardiac conduit is entirely prosthetic material (typically GoreTex).
https://www.ahajournals.org/doi/epub/10.1161/CIR.0000000000000696
5. What are the common complications of Fontan circulation?
CardiacArrhythmias: both atrial and ventricular arrhythmias can be common, especially owing to surgical scar lines, residual valvular disease, and hemodynamic sequelae of the Fontan palliationVentricular dysfunction: this may take the form of both systolic and/or diastolic dysfunctionValvular disease: atrioventricular valvular insufficiency, etc.Thromboembolic complications: venous stasis, endothelial damage, and exposure of von Willebrand factor contribute to a risk of thrombosis and risk of paradoxical emboli into the systemic circulation for patients with residual venous-arterial system connections (such as Fontan fenestration/baffle leak)
ExtracardiacNeurocognitive: mental health disorders (including PTSD, depression, and anxiety) are common, as are executive function limitations that can be identified as early as childhoodFontan-associated liver disease (FALD): including risk of developing hepatocellular carcinomaRenal disease: chronic kidney disease/renal venous hypertensionLymphatic: protein-losing enteropathy (PLE) and plastic bronchitis
6. When is it time to refer a patient with Fontan palliation for heart transplantation evaluation?
This is a very challenging, multidisciplinary decision that must weigh operative risk, HT candidacy, allosensitization, need for multi-organ transplantation (heart-liver, heart-lung, etc.), and patient-centered discussion about their goals of care.The team must way high near-term per-transplantation risk with improved long-term outcomes.
References
1. Cetta F, Dearani J, O'Leary P and Driscoll D.Tricuspid Valve Disorders: Atresia, Dysplasia and Ebstein Anomaly. In: H. Allen, R. Shaddy, D. Penny, T. Feltes and F. Cetta, eds. Moss and Adams' Heart Disease in Infants, Children and Adolescents Philadelphia: Wolters Kluwer; 2016.
2. Book WM, Gerardin J, Saraf A, Valente AM, Rodriquez III F. Clinical phenotypes of fontan failure: implications for management. Congenit Heart Dis. 2016;11:296–308. https://pubmed.ncbi.nlm.nih.gov/27226033/
3. Rychlik J, Atz AM, Celermajer DS, Deal BJ, Gatzoulis MA, Gewillig MH et al. American Heart Association Council on Cardiovascular Disease in the Young and Council on Cardiovascular and Stroke Nursing. Evaluation and Management of the Child and Adult With Fontan Circulation: A Scientific Statement From the American Heart Association. Circulation. 2019 Jul 1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000696
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