1.
Fontan anatomy
Fontan anatomy differs,
depending on the performed procedures.
See the following case examples of several variants.
Fig. 5 shows two different types of Fontan anatomy: TCPC and atriopulmonary circulation.
Fig. 6 is a good example of Glenn procedure with formation of venous collaterals through the azygos and hemiazygos systems.
Fig. 5: Different types of Fontan anatomy: TCPC (1A-B, coronal planes) and atriopulmonary circulation (2A-B, axial and sagittal plane) in still shots of cine SSFP.
References: Dr Evangelia Nyktari
Fig. 6: Glenn procedure.
See Fig. 7 showing variants of the intraatrial tunnel and a Fontan pathway stenosis.
Fig. 7: Variants of the intraatrial tunnel in paediatric patients. C: Patient has a Fontan pathway stenosis
References: Dr Inga Voges
2.
Complications
Fontan circulation is unique,
resulting in a specific spectrum of complications in end-organ systems (see Table 3).
Table 3: Table 3. Fontan circulation: late complications
Cardiovascular complications are more known and more frequently assessed by imaging.
Arrhythmias particularly in the context of haematological derangement as well as venous and cardiac chamber flow features may result in thromboembolic events.
Fontan pathway thrombosis and consequent pulmonary embolism is a known complication,
particularly in the patients who are less compliant with long-term antithrombotic treatment.
(5)
See Fig. 8: a large thrombus in the Fontan pathway with embolization into pulmonary arterial tree.
Fig. 9 shows a thrombus in Fontan pathway as well as a coarctation of aorta and lung parenchymal changes due to territorial hypoperfusion.
Fig. 8: Fontan circulation performed for congenital tricuspid atresia. Large thrombi seen in the right atrium (blue arrows) and in the right pulmonary artery (yellow arrows) on inversion recovery earlier gadolinium sequence.
References: CMR Unit, Royal Brompton Hospital, London, UK
Fig. 9: CT study of Fontan circulation performed for congenital tricuspid atresia.
References: Department of Radiology and Imaging, Liverpool Heart and Chest Hospital, UK
Pulmonary complications
Appearance of pulmonary arteriovenous malformations (PAVMs) in the context of Fontan circulation is a known complication and reflects a form of extracardiac shunting due to unbalanced pulmonary perfusion of hepatic vein blood flow.
Clinically PAVMs may be seen as severe oxygen desaturation. Patients may present with dyspnoea,
epistaxis,
stroke or cerebral abscess.
This feature can be occasionally seen on magnetic resonance imaging when assessing the large and mid-calibre thoracic vessels on balanced SSFP cine.
MR angiograms with or without contrast can specify the finding,
showing the exact location,
extent and morphology.
For the diagnosis of very small malformations CT remains the technique of choice.
See Fig. 10,
showing a large right pulmonary AVM in a Fontan patient.
Fig. 10: A large right pulmonary AVM in a Fontan patient
References: Dr Evangelia Nyktari
Although plastic bronchitis is a treatable complication,
it may be a less known airway condition for general radiologists.
It may occur in a spectrum of clinical settings:
- Cyanotic congenital heart disease (often with palliative procedures such as Fontan)
- Sickle cell disease
- Asthma
- Cystic fibrosis
While in the setting of sickle cell disease,
asthma and cystic fibrosis the main components of the bronchial casts are mucin,
fibrin and eosinophils,
in cases of congenital heart disease the predominant component is mucin and chylous content.
The pathological mechanism is thought to be hypersecretion of mucus in the airways and derangement of lymphatic drainage in the thoracic cavity,
which results in lymphatic leak to the bronchial lumina.
(6-9)
As the spectrum is wide,
over the last decades there have been several attempts to classify plastic bronchitis into types,
according to the aetiology and histology; the classification systems generally separate inflammatory and lymphatic groups.
Patients may present with non-specific symptoms,
ranging from dyspnoea and cough to acute respiratory distress.
The bronchial casts are usually expectorated.
Foreign body aspiration is one of the main differential possibilities; in such cases,
the casts are removed by bronchoscopy.
Novel treatment techniques such as embolization of lymphatic vessels are being studied.
(10)
See Fig. 11 showing bronchial casts from the bronchial trees of two Fontan patients.
Fig. 11: Plastic bronchitis: bronchial casts of two different Fontan patients.
References: Dr Inga Voges
Fontan-associated liver disease has been more widely discussed recently,
as the patient population has reached adult age.
Due to the specific haemodynamics (Table 4,
Fig. 12,
Video in Fig. 13),
liver parenchyma undergoes a pathological process related to the formation of portal hypertension.
Liver cirrhosis,
regenerative nodules and hepatocellular carcinoma are known risks in the this population. (11,12)
Fig. 13: Video 2. Haemodynamics of Fontan associated liver disease.
References: Dr Monika Arzanauskaite
Risk factors for Fontan-associated liver disease
- Higher Fontan pressures
- Increasing age
- Longer duration of Fontan
- Underlying Hepatitis B or C
- Alcohol abuse
- Hepatotoxic drug use
Indications for liver transplantation (11)
- HCC within Milan criteria
- Requirement for heart transplantation in the presence of decompensated liver disease or intrahepatic portal hypertension
- Liver dysfunction as defined by MELD score >15 (in the absence of warfarin anticoagulation)
See Fig. 14 showing two cases of Fontan associated liver disease.
Fig. 14: Two cases of Fontan associated liver disease. A-B: Fontan circulation in a 23 year old patient. C-D: Fontan circulation in a male patient.