Single ventricle heart defects, such as hypoplastic left heart syndrome (HLHS), are among the most complex and challenging forms of congenital heart defects to treat. They often require surgical repair in early infancy for survival.
Jennifer Lynch, a University of Pennsylvania physics graduate student who investigates biomedical optics at The Children’s Hospital of Philadelphia, researched how the timing of surgery influences brain injury in newborns with HLHS. She won Cardiology 2014’s Annual Outstanding Investigator Award for this study, and her contribution to the development of a novel tool to monitor brain metabolism and blood flow could help improve the care of these critically ill infants.
Infants with severe heart defects have a high prevalence of white matter injury, known as periventricular leukomalacia (PVL). White matter is the inner part of the brain that transmits information between the nerve cells and the spinal cord, as well as from one part of the brain to another. Babies with PVL are at higher risk for developing neurodevelopmental dysfunction, including cerebral palsy and intellectual or learning difficulties.
“These kids are very susceptible to brain injury because they’re not getting enough oxygen to their brain during this very fragile time when they’re just born and waiting to get their surgery and when they’re recovering from the surgery,” Lynch said. “The goal of the study was to see when they are most at risk for acquiring those injuries.”
Lynch works closely with Daniel Licht, MD, director of the Neurovascular Imaging Lab at CHOP and a member of the NeuroCardiac Care Program team. Their research focuses on how a portable noninvasive optical instrument — diffuse correlation spectroscopy (DCS) — developed at the University of Pennsylvania can provide information about blood flow to the brain.
They used this new technology in conjunction with near-infrared spectroscopy (NIRS), a noninvasive modality that provides information about tissue oxygenation. NIRS and DCS are diffuse optical techniques that make measurements by passing light through intact skin.
Currently, physicians rely on magnetic resonance imaging (MRI) to get a snapshot at specific time points to identify and quantify PVL. An advantage of using diffuse optical techniques is that they offer continuous monitoring at the bedside of cerebral blood flow and oxygen saturation, which allows physicians to get a more complete picture of how and when the injury occurs.
In this NIH-funded study, 37 infants with HLHS underwent pre- and postoperative MRI scans as well as continuous monitoring using NIRS/DCS. Lynch and her co-investigators noted that newborns who underwent surgery within four days of birth developed significantly less PLV.
The researchers also found some correlation between cerebral oxygen saturation measurements on the morning of surgery and the amount of white matter damage that the infants developed.
“We’re leading down this path where we think it’s this preoperative time period determining whether or not they acquire brain injury,” Lynch said. “Even though the brain injury doesn’t show up until a week later on the MRI scan, it seems to be predetermined preoperatively.”
In the future, Lynch said, diffuse optical monitoring of cerebral hemodynamic changes could help to predict which infants with HLHS are prone to brain injury and allow physicians to develop strategies to achieve optimal oxygen delivery to protect them from PVL.
Lynch received the outstanding investigator award at Cardiology 2014, the 17th annual update on pediatric and cardiovascular disease sponsored by CHOP. Held in Orlando in February, the conference gathered an international group of more than 1,000 medical experts. “It was exciting,” said Lynch, who attended the meeting for the first time and presented her abstract. “It was a great honor to win because a lot of amazing people were up for that award.”