Cyanotic and acyanotic congenital heart disease

Plain radiography

Chest radiography (chest x-ray [CXR]) is utilized as first-line imaging in patients with congenital heart disease (CHD) or in patients ultimately diagnosed with this condition, since the initial symptoms of CHD may mimic respiratory pathology (i.e., tachypnea, hypoxia, crackles, retractions, wheezing). Chest radiography has been found to have a low sensitivity for structural heart disease (26%–59%), a negative predictive value of 46%–52%, and a lower sensitivity in premature infants, less than 35 weeks’ gestation. The use of chest radiography as a routine screening test for CHD is not supported, and patients with unremarkable radiography in the clinical context of suspected CHD should have echocardiography. The performance of CXR in the detection of cardiac enlargement in pediatric patients has been compared to a gold standard of cardiac enlargement by echocardiography. CXR was found to have high specificity and negative predictive value (92.3% and 91.1%, respectively) for cardiac enlargement, but low sensitivity and positive predictive value (58.8% and 62.5%, respectively). The identification of cardiomegaly by plain chest radiography in adults has also been shown to have low sensitivity (40%) but high specificity (91%). The cardiothoracic ratio has been used as a marker for cardiac size in adult and pediatric patients; in adult patients, a cardiothoracic ratio greater than 0.55 has been shown to correlate with an increased risk of death.

Plain chest radiography, however, does have value. Causes of respiratory distress, such as pneumonia or pneumothorax, can be detected by this modality. Additionally, ionizing radiation exposure is minimal, sedation is not required, and radiographic imaging is rapid and readily available.

Computed tomography (CT)

This noninvasive modality is useful to image vascular and extracardiac structures, especially those with limited visualization on echocardiography. ^, CT angiography has been utilized to visualize cardiac anatomy, the coronary arteries, and other vascular structures. CT angiography is very useful in evaluating major arteries and veins, the aortic arch, and vascular rings. The relationship of vascular and airway structures can also be evaluated. ^, Compared to cardiac magnetic resonance imaging (MRI), CT angiography has superior spatial resolution (allowing for more detailed visualization of small vessels), is preferred when there are airway or pulmonary abnormalities, and may be used in patients in whom MRI may be contraindicated, such as patients with a pacemaker, internal defibrillator, or aneurysm clip.

CT does involve exposure to ionizing radiation and use of intravenous contrast material. While sedation is generally not necessary, it may at times be needed. CT is a readily available modality and can rapidly produce useful images for diagnosis and management, but CT for CHD should be performed and interpreted by those with expertise in pediatric CT imaging for CHD to obtain a diagnostic study and a meaningful interpretation.

Magnetic resonance imaging

MRI and magnetic resonance angiography (MRA) have proven to be excellent imaging modalities for patients with CHD, in both preoperative and postoperative patients. MRI can be utilized to assess anatomy and physiologic function and has the ability to assess for multiple conditions, including tetralogy of Fallot (TOF), transposition of the great vessels, single ventricle physiology, cardiac tumors, myocarditis, and cardiomyopathies. ^{, ,} Not all cardiac MRI studies require intravenous contrast. Gadolinium-based contrast agents are the typical contrast agents utilized. Contrast enhancement facilitates visualization of vascular structures and allows performance of cardiac function and perfusion studies. In patients with cardiomyopathies, right ventricular dysplasia, and myocarditis, contrast-enhanced MRI studies can be used to detect scarring or fibrosis. ^,

One disadvantage of cardiac MRI is the length of time needed to complete a study, and breath holds or sedation may be required. Some young infants may not require sedation, as they may be swaddled. ^{, ,}

Ultrasound (US)

Echocardiography continues to be a first-line imaging modality in pediatric patients with suspected CHD. Excellent visualization of cardiac structure, anatomy, and function can be achieved with echocardiography. ^, Echocardiography can be utilized to diagnose structural cardiac disease and plan for operative repair and to clinically follow patients.