Magnetic Resonance Imaging in the Adult with Congenital Heart Disease

Given relatively recent advances in pediatric cardiovascular surgery, catheter-based interventional therapies, intensive care, and medical management, many children with complex congenital heart disease (CHD) are surviving into adulthood. As such, adults with CHD constitute a rapidly growing population. The majority of these adults have complex residual disease requiring serial imaging and often further intervention. There are a number of imaging modalities available to the clinician and radiologist when it comes to these evaluations. Magnetic resonance imaging (MRI) holds a unique and growing position among these. Echocardiography has been a mainstay of imaging in congenital heart disease. Despite its importance in rapid diagnosis and follow-up, it has limitations in the evaluation of the adult with CHD. The presence of postoperative scar, chest wall deformities, overlying lung tissue, and large body size often results in suboptimal transthoracic echocardiographic windows. Transesophageal echocardiography, while providing improved acoustic windows, is limited by its small fieldof-view and more invasive nature, often requiring deep sedation or general anesthesia. Cardiac catheterization, employing X-ray fluoroscopy and contrast angiography, has an expanding role in minimally invasive interventions, but its role as a diagnostic procedure is rapidly diminishing. This is in part due to its limitation as a 2D projection imaging technique with poor soft-tissue contrast and the substantial ionizing radiation exposure involved, and in part because both diagnostic and functional analysis are often better performed with noninvasive imaging techniques. Computed tomography (CT) has been useful in evaluating vascular anatomy, and with the advent of high-resolution CT and cardiac gating, has emerged as a useful tool for assessing intracardiacanatomyandmyocardialfunction.Nevertheless, the temporal resolution of cardiac CT remains limited and advances in CT imaging technology have often come with increases in exposure to ionizing radiation. MRI has emerged over the past few decades as an alternative, complementary, and frequently superior imaging modality for the investigation of anatomy and function in the adult with CHD. It has many advantages over other imaging modalities. It does not require the use of iodinated contrast agents and does not involve exposure to ionizing radiation. This is particularly important in a population of patients who have been, and continue to be, exposed to large doses of contrast agent and radiation during hemodynamic and interventional catheterization. Major advances in MRI hardware and software, including advanced coil design, faster gradients, new pulse sequences, and faster image reconstruction techniques, allow rapid, high-resolution imaging of complex anatomy and accurate, quantitative assessment of physiology and function. This review highlights the MRI techniques frequently employed to evaluate the anatomy and physiology of the adult with CHD. It provides information about the general application of cardiac MRI in this patient population, as well as sample protocols and guidelines for its use in the more commonly encountered lesions referred for MRI.