False Positive Perfusion/Ventilation SPECT Study for Pulmonary Embolism in a Patient with Fontan Circulation

Figures

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  Figure 1. SPECT: First row: Ventilation with technegas, second row: Perfusion with 200 MBq of Tc-99m MAA, and third row: Subtraction of anterior, left lateral, MIP and transaxial images. There is satisfactory ventilation in both lungs. However, there is nearly no perfusion in the left lung (cross in transaxial images). Moreover, there is a subsegmental perfusion/ventilation mismatched defect in the right upper lobe, raising the possibility of pulmonary embolism (PE)

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  Figure 2. Computed tomography (CT) pulmonary angiogram coronal and transaxial images below the level of the carina. A extra cardiac conduit demonstrated with the superior vena cava (SVC) to pulmonary arteries (PA) and a stent within the intra-thoracic inferior vena cava (IVC) which enters the right PA resulting to single ventricle/Fontan physiology. There is non-opacified blood within the stent as a result of passive venous supply to the lungs in Fontan circulation and IV contrast seen within the stent post upper extremity contrast administration and passive venous supply to the lungs. There is also a hypoplastic right ventricle. The peripheral PA are patent with no evidence of distal PE. There is ground glass shadowing in the right upper lobe with minor cystic changes, which could represent an atypical infection. The Fontan procedure refers to any surgical procedure that leads to systemic flow of venous blood to the lungs without passing through a ventricle. In 1971, Fontan and Baudet (1) described a surgical procedure for repair of tricuspid atresia that was built on experimental and clinical research since the 1940s. The principle of the Fontan operation is diversion of systemic venous…