Introduction Noninvasive cardiovascular imaging plays a fundamental role in the clinical history of patients with congenital heart diseases (CHDs) and acquired cardiac conditions, from antenatal diagnosis to long-term follow-up in adult life Prior to birth, different noninvasive imaging modalities are used to evaluate cardiac anatomy and physiology, to plan surgical and interventional procedures, and to assess the outcomes and complications With a reported prevalence of 9 per 1000 live births, which corresponds to approximately 1.35 million newborns per year worldwide, CHD patients represent a very large population.1 Moreover, the improvement in the treatment of complex CHD has led to a substantial increase in the number of patients who reach adult age, living with a cardiac condition In these patients, the clinical follow-up is often associated with the need for noninvasive imaging.2 Most of these patients will have to undergo lifelong imaging follow-up with serial examinations, and this should be taken into account when deciding among the different imaging modalities available The rapid technologic development of noninvasive imaging has led to a reduction in the need of cardiac catheterization The ideal noninvasive imaging modality should be able to assess both cardiac and extracardiac anatomy, provide information about physiology and function, and be highly reproducible, safe, and cost effective None of the imaging modalities available can satisfy all these criteria, and therefore the assessment of children with CHD often requires a multimodality approach.3 Echocardiography always represents the first line investigation when CHD is suspected and is the most common follow-up modality It has the great advantage of being portable, rapidly available at the bedside even in emergency scenarios, but it sometimes fails to provide adequate information of extracardiac anatomy and distal vascular structures and can be limited by poor acoustic windows (e.g., after cardiac surgery) Moreover, echocardiography is less able to provide chamber quantification data for the right ventricle (RV), and this information is often crucial in patients with CHD because the RV is commonly involved Cardiac magnetic resonance (CMR) has emerged as a powerful technique to assess comprehensively both three-dimensional (3D) anatomy and physiology in patients with CHD It allows accurate evaluation of both cardiac and extracardiac anatomy in multiple image planes, as well as ventricular function and physiology Image postprocessing provides information about left ventricle (LV) and RV volumes and ejection fraction (EF) with high interobserver and intraobserver agreement, regardless of ventricular orientation and morphology It allows quantification of valvar regurgitation, as well as stroke volume (SV) and shunt Acquisition of 3D datasets allows 3D reconstruction of complex cardiac anatomy and evaluation of the origin and proximal course of the coronary arteries without the use of contrast media or radiation Compared with echocardiography, CMR can add important and relevant information about cardiac anatomy, cardiac function, and tissue characterization in patients with CHD, as well as acquired cardiac conditions, summarized in Tables 21.1 and 21.2 Table 21.1 Additional Information Obtainable From Cardiac Magnetic Resonance (Compared With Echocardiography) in Structural Congenital Heart Disease Anomaly Atrial septal defects Additional Information Assessment of associated extra cardiac defects (anomalous pulmonary venous return) Accurate quantification of shunt Accurate quantification of RV volumes and EF Ventricular Assessment of location and size with possibility of 3D reconstruction septal defects Assessment of associated extracardiac defects (coarctation, patent arterial duct) Accurate quantification of shunt Accurate quantification of LV volumes Bicuspid aortic Accurate measurements of the entire aorta valve Quantification of aortic regurgitation in presence of eccentric jets at echo Aortic Assessment of the entire arch (hypoplasia, vascular abnormalities) coarctation Assessment of the presence of collateral vessels Follow-up after repair (recoartation, aneurysm), mostly in patient with poor acoustic window Patent arterial Assessment of the entire arch (hypoplasia, vascular abnormalities) duct Assessment dimension in older patients with poor acoustic window Accurate quantification of the shunt Assessment of associated defects (coarctation) Anomalous Assessment of all the pulmonary veins anatomy pulmonary Assessment of associated extracardiac anomalous venous connections venous return Quantification of the shunt Quantification of RV volumes and function Ebstein anomaly Assessment of tricuspid leaflet morphology and displacement Accurate quantification of the tricuspid regurgitation Accurate quantification of the RV and arterialized RV volume and RVEF Quantification of shunt, if present Tetralogy of Assessment of pulmonary regurgitation Fallot Assessment of RV volumes and EF Assessment of pulmonary arteries anatomy and flow (stenosis, split flows) Assessment of origin and proximal course of the coronary arteries Double-outlet right ventricle Transposition of the great arteries Common arterial trunk Anomalous origin of coronary arteries Single ventricle physiology Assessment of VSD location and commitment to great arteries Quantification of LV and RV volumes Quantification of shunt Follow-up assessment after surgery Coronary arteries stenosis or kinking Presence of inducible myocardial perfusion defects Quantification of RV volume and function (systemic RV) Anatomy of the pulmonary arteries Assessment of associated extracardiac abnormalities (coarctation) Origin and proximal course of the LCA and RCA and relationship to the great vessels Presence of inducible myocardial perfusion defect Presence of myocardial infarction Assessment of systemic venous return before surgery (presence of bilateral SVC) Assessment of associated extracardiac abnormalities (coarctation) and collaterals Quantification of single ventricle volumes and systolic function Follow-up after Fontan operation: assessment of SVC and IVC connections to PAs, exclude presence of thrombus, assess single ventricle volume and function, quantify atrioventricular vale regurgitation EF, Ejection fraction; IVC, inferior vena cava; LCA, left coronary artery; LV, left ventricle; PAs, pulmonary arteries; RCA, right coronary artery; RV, right ventricle; RVEF, right ventricular ejection fraction; SVC, superior vena cava; VSD, ventricular septal defect Table 21.2 Additional Information Obtainable by Cardiac Magnetic Resonance (Compared With Echocardiography) in Cardiomyopathies, Genetic Diseases, and Acquired Cardiac Diseases Anomaly Myocarditis Additional Information Presence of myocardial edema Presence of myocardial scar (LGE) Kawasaki disease Assessment of coronary artery anatomy Presence of myocardial infarction Presence of inducible myocardial perfusion defects Dilated cardiomyopathy Accurate quantification of LV volumes and EF Evaluation of myocardial fibrosis (LGE) Evaluation of LV thrombi Hypertrophic cardiomyopathy Accurate measurement of maximal wall thickness Evaluation of myocardial fibrosis (LGE) Arrhythmogenic right ventricular Quantification of RV volumes cardiomyopathy Evaluation of RV regional wall motion abnormalities Muscular dystrophies Accurate quantification of LV volumes and EF in patient with poor acoustic window Marfan syndrome, Loeys-Dietz syndrome Accurate measurements of the entire aorta Cardiac masses Tissue characterization Mass perfusion EF, Ejection fraction; LV, left ventricle; LGE, late gadolinium enhancement; RV, right ventricle CMR also has limitations, mostly related to the long scanning time and the need for breath holds during acquisition, which cannot often be achieved properly in children However, the development of new free-breathing CMR