Pulmonary Atresia with Ventricular Septal Defect without Major Aorto-Pulmonary Collateral Arteries: Echocardiography and the Role of Computed Tomography and Magnetic Resonance Imaging

Pulmonary atresia with ventricular septal defect (PA-VSD) is usually diagnosed by transthoracic or fetal echocardiography, with the prenatal diagnosis being feasible and accurate if fetal cardiology services are available. The limitations of transthoracic echocardiography (TTE) in the evaluation of PA-VSD include the complete evaluation of the pulmonary arteries and patent ductus arteriosus, quantitative evaluation of the right ventricle size and function, and delineation of associated cardiac anomalies such as coronary artery anomalies, anomalies of systemic or pulmonary venous return, and complex arch anomalies. Echocardiography also has limitations in evaluating hemodynamics such as flow volumes, shunts, and regurgitant fraction. Despite these limitations, TTE remains the most widely available and the most cost-effective cardiac imaging modality for patients with PA-VSD and its accuracy in evaluating the sources of pulmonary blood flow and in selecting patients for systemic-to-pulmonary artery shunt palliation is well established. Cardiac computed tomography (CT) can answer many of the questions not answered by TTE, including demonstrating the PA anatomy and defining coronary artery, systemic and pulmonary venous, and aortic arch anatomies. The short acquisition time allows for the study to be performed without sedation/anesthesia in most patients. Cardiac CT is also useful in defining postoperative anatomy when there are non-magnetic resonance imaging (MRI) compatible devices or even MRI-compatible devices that cause a significant MRI artifact. Cardiac MRI/magnetic resonance angiography has emerged as an ideal modality to evaluate patients with PA-VSD as it allows for anatomic, functional, and hemodynamic assessment without exposure to ionizing radiation or iodinated contrast material. Both cardiac CT and cardiac MRI can be used to generate 3D imaging of the heart.