Magnetic Resonance Imaging in the Evaluation of Congenital Intracardiac Shunts

For many years, cardiac catheterization and angiocardiography have been the main diagnostic methods for morphological and functional assessment of congenital shunts. However, catheterization techniques are invasive, require injection of iodide contrast and exposure to x-rays, and complications may arise, particularly in pediatric patients. In the last 2 decades, echocardiography has progressively displaced invasive methods in the overall evaluation and definitive diagnosis of children and adults with congenital heart diseases. 1 Although echocardiography is a safe, cheap technique that offers high diagnostic yield, it also has important limitations. The echocardiographic image is less clear in older children and adults than in infants and small children, in whom high-frequency transducers with high spacial resolution are required. In addition, multiple surgical interventions in older children and adults may cause further deterioration of the image. Although echocardiography provides high anatomic definition of almost any cardiac structure, it is virtually blind to what is happening outside the heart, a few centimeters into the vascular system. This technique is particularly limited in assessment of pulmonary or systemic venous drainage or peripheral pulmonary artery circulation. It is also very imprecise in evaluation of the thoracic aorta, congenital or surgical fistulas, or collateral systemic vessels. Echocardiography is even more limited in functional assessments. The size and function of the left chambers can be readily assessed by 2-dimensional echocardiography, but this technique is much less useful in the evaluation of the right chambers. Right ventricular function is particularly difficult to determine by echocardiography, but in congenital heart disease, the right ventricle may be of similar if not more importance