Magnetic Resonance Imaging in Congenital Heart Disease

Abstract

Magnetic resonance imaging (MRI) is increasingly being applied to critically ill newborns with congenital heart disease (CHD) with the hope of understanding mechanisms accounting for adverse neurodevelopmental outcome. This powerful technique has opened an unprecedented window into normal development and pathogenesis during fetal life and surrounding surgery. Much as the technological advances of cardiopulmonary bypass, cardiac intensive care, and transcatheter and surgical techniques have translated into improved survival for neonates with complex congenital heart lesions, MRI promises to elucidate mechanisms and measure outcomes in a way that will inform treatment and establish neurointensive care to lessen neurologic morbidity. Many agree that improving neurodevelopmental outcome in CHD is the preeminent challenge to the field.1 MRI studies in CHD have made the important and surprising observations that (1) brain injury is present before surgery,2 (2) injury is most commonly focal affecting the white matter,3 and (3) brain development is delayed in term infants with CHD.4 Despite its promise as a sensitive early outcome variable that could be used to structure interventional studies with novel trial design,5 success to date has largely been descriptive, identifying clinical risk factors in limited case series. A particular challenge applying these findings to clinical practice is that the incidence of injury and associated risk factors are often unique to each form of CHD.6 For this reason, the approach has not substantially altered clinical care to date. However, several themes have emerged from multiple studies, providing confidence that the identified risk factors are valid and potent. These include the significance of postoperative hypotension,3,6 hypoxemia3 and diminished regional cerebral oxygen saturation.6,7 Although multiple studies have noted the high frequency of preoperative brain injury, particularly in neonates with transposition of the great arteries (TGA),2,6,8 few risk factors have been identified …