Newborns who have cardiac surgery for heart disease have a significant risk of potentially severe seizures, which may not be apparent in routine bedside clinical assessments. Pediatric researchers who followed current professional guidelines that recommend continuous encephalographic (EEG) monitoring reported that infants who experienced postsurgical seizures had a higher mortality rate than those without seizures.
“We found that continuous EEG monitoring identified newborns who had seizures, which indicated underlying brain injury and are also a risk factor for worse neurodevelopmental outcomes and mortality,” said study leader Maryam Y. Naim, MD, a cardiac critical care physician at The Children’s Hospital of Philadelphia (CHOP). “Recognizing these seizures early is crucial for implementing treatments to prevent their recurrence.”
Naim and colleagues from CHOP and the Perelman School of Medicine at the University of Pennsylvania published their study in the July issue of The Journal of Thoracic and Cardiovascular Surgery.
Majority of seizures would not have been visible to clinical caregivers
The researchers studied 161 newborns who underwent open heart surgery at CHOP over an 18-month period and received continuous EEG monitoring as part of routine postoperative monitoring. The team found seizures in 13 of the infants (8 percent). Of those 13 infants, 11 (85 percent) had subclinical seizures, detectable only by EEG. Eight of the 13 infants had status epilepticus seizures, which are particularly dangerous. The majority of the seizures found using EEG would not have been visible to clinical caregivers, said Naim. The seizures occurred in newborns with all types of congenital heart disease (CHD).
The study team found a mortality rate of 38 percent (five deaths) among the 13 infants with seizures, compared to 3 percent (four deaths) among the 148 infants who did not have seizures. “Seizures are a marker of brain injury, but their recurrence may independently cause brain injury, making it all the more important to detect and potentially treat seizures as soon as possible,” said Naim.
This single-center study was the first to report on the implementation of guidelines issued in 2011 by the American Clinical Neurophysiology Society recommending continuous EEG monitoring of neonates undergoing cardiac surgery for congenital heart disease. CHOP implemented routine postoperative EEG monitoring in 2012. Many centers do not currently follow these recommendations, possibly because of the resource commitment necessary to perform continuous EEG monitoring for these patients.
Early identification of seizures key to intervention and improved long-term outcomes
Identifying seizure occurrence allows clinicians to use antiseizure drugs or other therapies to decrease seizure recurrence. Naim acknowledged that investigators have not yet demonstrated that treating seizures will improve long-term outcomes in high-risk pediatric heart patients.
However, previous studies in animals and humans have shown a link between seizures and long-term neurodevelopmental outcomes. The Boston Circulatory Arrest Study, for instance, showed that postoperative seizures were the most important predictor of poor neurological outcomes, such as memory and executive function, when pediatric heart patients were followed 16 years later. More recently, a CHOP co-author of the current paper, J. William Gaynor, MD, found that a genetic subset of CHD patients treated as infants with antiseizure medication had better neurological outcomes compared to patients in the Boston study.
“Our surgeons are excellent at what they do, with exceptional survival rates following cardiac surgery in this high-risk population,” said Naim. “Our focus has now moved from survival to improving long-term neurodevelopmental outcomes for CHD patients. With that said, I expect that investigations of seizures and seizure prevention may become more prominent,” she added.
An editorial commentary on the current study in the same journal calls for a larger, multicenter study to analyze continuous EEG monitoring following infant heart surgery, and to investigate seizure prevention and treatment. The commenters also advocate for a less expensive, and less labor-intensive screening tool than continuous EEG monitoring.
Funds from the National Institutes of Health (grants NS072338 and NS076550) and the June and Steve Wolfson Family Foundation supported this research.
“Subclinical seizures identified by postoperative electroencephalographic monitoring are common after neonatal cardiac surgery,” The Journal of Thoracic and Cardiovascular Surgery, July 2015 print issue. http://doi.org/10.1016/j.jtcvs.2015.03.045