An approach to imaging adult congenital heart disease: pitfalls and pearls

Noninvasive cardiovascular evaluation of an adult congenital heart disease (ACHD) patient is a multimodality endeavor that can include chest roentgenograms, electrocardiograms, echocardiography (including stress, three-dimensional, intravascular and intracardiac ultrasound, and transesophageal), cardiac magnetic resonance imaging (CMR), computed tomography angiography (CTA), single photon emission computed tomographic (SPECT) perfusion imaging, and positron emission tomography (PET). The cost-benefit ratio and limitations of each modality should always be considered (Table 1). Adults with ACHD often need repetitive imaging, making them vulnerable to radiation-induced cancer; hence, modalities using ionizing radiation should be minimized. A transthoracic echocardiogram remains the initial noninvasive modality of choice due to its real-time imaging capability with excellent temporal resolution and its ability to quickly assess hemodynamics along with anatomic delineation. A transesophageal echocardiogram is extremely helpful in further defining intracardiac anatomy and guiding surgical and interventional procedures. Cardiac magnetic resonance imaging is an adjunctive modality to an echocardiogram because ACHD patients frequently have intra-thoracic abnormalities (e.g., adhesions from multiple cardiac operations and lung disease) that can limit the resolution of the ultrasound beam. A CMR is especially helpful in periodic evaluation of the right ventricle, visceral situs, extracardiac anatomy, lesions of the pericardium, pulmonary veins, systemic veins, pulmonary arteries, and aorta. For real-time CMR, special techniques such as echo planar can be used; for hemodynamic evaluation by CMR, techniques like velocity-vector mapping, myocardial tagging, echo planar, and fast gradient echo can be used. Besides excellent spatial resolution, the advantage of CTA over other techniques is an extremely fast acquisition time. Furthermore, CTA can replace an invasive procedure such as catheterization and angiography for anatomical diagnosis where hemodynamics is not required, such as the diagnosis of arch or coronary artery anomalies. Nuclear scans such as lung perfusion scans and splenic scans are very helpful in determining differential pulmonary blood flow and splenic function, respectively. Both SPECT and PET are valuable in assessing tissue perfusion and metabolism and help to determine viable versus nonviable myocardium after surgery for hypoplastic left heart syndrome and coronary artery anomaly, after arterial switch operation for d-transposition of great arteries, and in acquired illness such as Kawasaki disease. When considering imaging a patient with ACHD, and overall evaluation strategy should include the aspects found in Table 2.