Abstracts

Rationale: Patients with congenital heart disease are at high risk for cerebral injury and seizures. Surgical procedures are necessary, but come with a high risk of potential complications such as cardiac arrest or the need for extracorporeal membrane oxygenation (ECMO). The aim of this study is to further characterize the clinical and electrographic features of critically ill neonates and children with congenital heart disease that undergo a clinically indicated continuous EEG (cEEG).Methods: Retrospective study of neonates and children with congenital heart disease who underwent a clinically indicated cEEG (>3 hours of uninterrupted EEG) in the neonatal, pediatric, and cardiac intensive care unit at Boston Children’s Hospital from January 2011 to December 2013. In patients with multiple cEEG procedures, only the first recording was considered. Electrographic seizures were defined as any seizure detected on cEEG, whether electro-clinical or electrographic-only seizures. Electrographic status epilepticus (ESE) was defined as a continuous seizure lasting greater than 30 minutes or seizures totaling at least 50% of a 1 hour epoch.Results: Eighty eight neonates and children were studied (48% male) with a median age of 3.1 years. Thirty one patients were less than 1 month corrected gestational age while 57 patients were 1 month to 21 years of age. Forty five patients had a structural lesion, of which 35 were acute. Thirty six patients had a cardiac arrest, 10 underwent hypothermia, 39 were paralyzed and 33 required ECMO. The main indications for monitoring were to characterize events concerning for seizures in 56 patients (64%) or for the detection of nonconvulsive or subclinical seizures in 38 patients (43%). Sporadic interictal discharges were seen in 43 patients (49%). Electrographic seizures were detected in 11 (12.5%) patients with ESE occurring in 1 patient (9%). 7 out of 11 patients (65%) with seizures were within 1 week of cardiac surgery. Electrographic only seizures were detected in 5 patients (45%). 55% of patients with ES had interictal epileptiform discharges. The majority of seizures were focal (n=9) and all ES lasted 1 to 5 minutes. The median total duration of monitoring was 21.6 hours with minimum duration 6.8 hours (Figure 1). The median time to first seizure was 1.6 hours with the longest time to detection of first seizure being 20.9 hours (Figure 2). The median duration of monitoring patients without seizures was 19.6 hrs. The overall mortality was 28% (25/88) while 18% of patients with seizures died.Conclusions: Patients with congenital heart disease that have a clinically indicated cEEG are at high risk of electrographic seizures particularly in the postoperative period, and nearly half of patients with seizures had subclinical events requiring EEG for detection. While many seizures will be detected in the first several hours of monitoring, twenty four hours of monitoring may be necessary to capture all seizures. There is a considerable risk of mortality in ICU patients with congenital heart disease.