CT for Assessment of Thrombosis and Pulmonary Embolism in Multiple Stages of Single-Ventricle Palliation: Challenges and Suggested Protocols

Abstract

The total cavopulmonary connection (TCPC), or Fontan procedure, diverts systemic venous blood directly into the pulmonary arteries and is the palliative surgery of choice for patients with a wide variety of congenital heart diseases with single-ventricle physiologic characteristics. Pulmonary embolism and thrombosis are known complications and are among the major causes of morbidity and mortality in patients after TCPC. Magnetic resonance (MR) imaging is usually performed for postoperative evaluation of patients after single-ventricle repair; however, screening for thrombosis or embolism with MR imaging is not always feasible because of the emergent nature of the clinical presentation or because of artifacts from metallic devices or coils. Computed tomographic (CT) angiography is an effective method for diagnosing pulmonary embolism in children. However, because of altered hemodynamics after single-ventricle palliation, there are unique challenges in achieving optimal opacification of the pulmonary arteries and Fontan circuit that can result in nondiagnostic CT angiographic studies or erroneous image interpretation. Radiologists should be familiar with the multiple stages of single-ventricle palliation, understand the technique for performing pulmonary CT angiography at each stage, and recognize common pitfalls in obtaining and interpreting pulmonary CT angiographic images in patients who have undergone single-ventricle repair. Online supplemental material is available for this article. (©)RSNA, 2016.

Imaging of complications following Fontan circulation in children — diagnosis and surveillance

“…For Fontan circulation, specific contrast-injection protocols are necessary depending on the clinical question. Knowledge of pitfalls in the interpretation is important [ 33 , 43 ] (Fig. 7 ).…”

“…7 ). Functional cardiac information can also be provided by electrocardiography-gated scanning of the whole cardiac cycle at the cost of increased radiation and performed in select cases, such as children with an implantable device like a cardioverter defibrillator [ 33 , 44 ]. Both MR and CT are used to guide intervention for catheter-based ablation of arrhythmia [ 45 , 46 ].…”

Misdiagnosis of Pulmonary embolism in a Fontan's patient: When standard protocol CT Pulmonary angiogram is inadequate

“…In a normal circulation contrast enhanced blood from the SVC is mixed with noncontrast blood from the IVC in the right ventricle leading to equal distribution through the right and left pulmonary artery. In a Fontan circuit, the lack of this sub-pulmonary ventricle results in an uneven distribution of contrast through the pulmonary arteries [2] and suboptimal timings of pulmonary artery enhancement [3] . This can mimic the appearance of a 1-sided PE in the lung that is preferentially supplied by the IVC.…”

“…Studies show that a simultaneous injection of contrast into upper and lower limb veins leads to a more uniform distribution of contrast in the pulmonary arteries [3] .…”

User-Friendly Vendor-Specific Guideline for Pediatric Cardiothoracic Computed Tomography Provided by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group: Part 1. Imaging Techniques

“…When an arm vein is used, use of the right side can avoid streak artifacts around the left brachiocephalic vein; the streak artifacts are more pronounced and extensive in patients with bilateral superior vena cavae, in which the use of a right arm vein is highly recommended. It is difficult to achieve uniform vascular enhancement in patients with superior or total cavopulmonary connection because of the preferential blood flow and streaming (47778). To obtain optimal vascular enhancement in subjects with superior cavopulmonary connection, leg vein injection with a longer scan delay of approximately 50–60 seconds depending on the patient size is recommended.…”