Comments: Pulmonary atresia with intact ventricular septum is a rare congenital cardiac malformation with considerable morphological heterogeneity. There is complete atresia of the pulmonary valve in conjunction with a variable degree of hypoplasia of the tricuspid valve and RV cavity. Ebstein malformation coexists in 10% of patients. The hypoplastic and hypertensive RV can be associated with right ventricular to coronary communications termed fistulae, present in approximately 50% of patients at birth. At the worst end of the spectrum, such fistulae may be associated with coronary artery ectasia, stenoses, or even interruption; this latter situation is known as an RV-dependent circulation for reasons to be discussed subsequently.

In those cases where a biventricular repair is not deemed possible, a univentricular route is embarked on. A balloon atrial septostomy is initially performed to enable right-to-left atrial shunting and so preserve cardiac output. A systemic-to-pulmonary shunt is then performed to increase pulmonary blood flow and thus oxygenation. At 3 to 12 months a bidirectional superior cavopulmonary (Glenn) anastomosis is constructed followed by a total cavopulmonary connection (modified Fontan), usually at 2 to 5 years of age. Most often, these procedures are performed separately, unlike the case described here, where they were performed as a single procedure.

In the Fontan circulation all the systemic venous return is directly to the lungs without the need for a subpulmonary ventricle. This does require high venous pressures to drive the blood across the pulmonary bed. In some cases, a fenestration is performed at the time of the Fontan. This is a small atrial defect created in the lateral tunnel that allows deoxygenated blood to flow into the left heart (by way of right-to-left shunting), reducing the venous pressures and maintaining cardiac output at the expense of mild systemic desaturation. Fenestration of the Fontan circulation has improved operative survival rates among high-risk patients.

Comments: The application of the Fontan procedure in one of its several modifications has allowed many patients excellent univentricular palliation. However, patients doing well after a Fontan procedure should be seen at least yearly. The risk of cardiac failure and late death increases progressively. Overall survival is approximately 86% at 5 years and 74% at 10 years.

Intracardiac thrombus formation is not an uncommon sequela after the Fontan operation. Oral anticoagulation therapy is prescribed in many centers, although there is no consensus at present for routine use in all patients. The incidence of thromboembolic events after the Fontan operation is 10% to 20%, and depends on the age of the patient and the size of the RA for patients with an atriopulmonary type of Fontan.

Comments: Most Fontan patients without atrial fenestration have a transcutaneous oxygen saturation at the lower end of normal. If oxygen saturations are less than 90%, one should determine the etiology of the hypoxemia. Apart from fenestration, other causes of hypoxemia after a Fontan include:

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  Residual intra-atrial communication(s)

  
  
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  Systemic-to-pulmonary venous collateralization with right-to-left shunting

  
  
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  Pulmonary arteriovenous malformation

  
  
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  Connection of hepatic veins to the coronary sinus or LA (i.e., excluded from the total cavopulmonary circulation pathway)

  
  
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  Reopening of levoatrial cardinal vein allowing systemic venous blood to enter the LA

  
  
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  Shunting via thebesian veins

  
  
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  Intrinsic pulmonary pathology

  
  
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  Diaphragmatic (phrenic nerve) palsy

  
  
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  Hepatopulmonary syndrome

  
  
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  Murmurs are uncommon in Fontan patients.

A systolic murmur suggests AV valve regurgitation (in this case tricuspid regurgitation from the high-pressure RV), dehiscence of a surgical patch leading to left-to-right ventricular shunting, forward flow through an incompletely ligated main pulmonary trunk, or the development of a restrictive, subaortic VSD (bulboventricular foramen).

Diastolic murmurs may be due to aortic or pulmonary regurgitation. Continuous murmurs may be due to fistulous communications, systemic-to-pulmonary collateral arteries, or incompletely ligated systemic-to-pulmonary shunts.