Winter 2015 - Research and innovation

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Brain MRIs Provide Insight into Cardiac Neurodevelopment

A common but often overlooked consequence of congenital heart disease (CHD) is impaired neurodevelopment. As early interventions save more and more structurally complex hearts, the population of children, adolescents and adults living with CHD steadily climbs. Children with congenital heart disease are more likely to struggle with language, reasoning, attention span and controlling impulsive behavior than their CHD-free peers. The Boston Children’s Cardiac Neurodevelopment Program is leading research efforts that may help current and future cardiac patients by examining the physiologic foundations of cardiac neurodevelopment delays.

Disruptive medical events in the Cardiac Intensive Care Unit post-surgery are well-known contributors to cognitive lapse, and a home environment that stifles socialization and learning can also negatively impact developing brains.  Still, the brain seems to develop differently in congenital heart disease patients. Figuring out exactly what that internal difference is may lead to development of medical measures that can prevent cognitive delay in future patients.

Caitlin Rollins, MD, is pioneering a study that examines the brain MRIs of fetuses, and Henry Cheng, MD is using both brain MRIs and near-infrared spectroscopy (NIRS) devices with infants in the Cardiac Intensive Care Unit (CICU). Put together, their findings can shed much light on how the cardiac patient’s brain develops and how connections between the different areas of the brain are formed.

Rollins explains that very few studies have been published about fetal brain growth and development in cardiac patients. “In 2010, one study found abnormalities in the patterns of brain maturity and smaller brain volumes in fetuses with cardiac disease compared with the control group,” Rollins says. “While the study was a major contribution to the field, fetuses were evaluated on a single occasion toward the later part of the pregnancy.”  Rollins’s study enrolls patients during the second trimester and obtains MRIs on two occasions to evaluate growth and maturation over the course of the pregnancy to identify the earliest markers of abnormal brain development. It also differentiates patients based on details of the underlying cardiac disease. “We don’t just record the diagnosis; we detail each patient’s specific anatomy, because even within diagnoses hearts can impact the brain in dramatically different ways.”

Ultimately, Rollins hopes to find out if there are ways to combat the neurodevelopmental delays as early as possible. For instance, if lack of oxygenated blood is a problem in a patient with transposition of the great arteries (TGA), the mother could be given medication to increase her blood’s oxygenation. Early indications suggest that the underlying cardiac diagnosis may have a significant impact on fetal brain development, Rollins reports.

Cheng’s study combines data from three sources: brain MRIs, NIRS (now present in our Cardiac CICU) and comprehensive neurodevelopmental follow-up. The MRIs are performed on infants before surgery and again three months after surgery. NIRS readings are made before surgery, immediately after surgery and three months out. The NIRS adds information that MRIs cannot capture, such as cerebral oxygen levels and metabolism. Cheng reports preliminary evidence that synaptic development in CHD patients may be delayed. However, a deeper understanding of cerebral hemodynamics is necessary to sort out why this is happening. “What we want to know next,” he explains, “is how much oxygen goes to the brain? How much of that is actually used, and is there enough?”

Cardiac Neurodevelopment Program Director Jane Newburger says the group has grown exponentially since its inception in 2006. Her enthusiasm is contagious as she explains, “We now have a large, multi-disciplinary team committed to this research, including specialists from psychiatry, radiology, neurology, cardiology and genetics,” she says. “We even have occupational and physical therapists involved.”   

Undoubtedly, the program’s groundbreaking research will significantly advance the way clinicians across specialties approach cardiac neurodevelopment. 

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