Abstracts

Rationale: QT interval adaptation to heart rate (QT dynamics) represents a fundamental electrophysiological property essential for the stability of ventricular depolarization-repolarization. Impaired QT dynamics have been observed in cardiac disorders with propensity for ventricular arrhythmias, possibly reflecting an increased arrhythmic risk. Ictal ventricular repolarization abnormalities and arrhythmias have been reported in individuals with epilepsy, suggesting that seizures may adversely affect ventricular stability. Therefore, we hypothesize that seizures are associated with altered QT dynamics, with the most profound effects in individuals with prolonged seizures (status epilepticus) and epilepsy. Methods: We retrospectively reviewed Texas Children's Hospital emergency center (EC) visits from 1/1/2011 to 12/31/2013 with primary diagnosis of febrile seizures (FS), epilepsy with increased seizure frequency (E-Sz), and status epilepticus (SE). Children were included if they had a 12-lead EKG within 24 h of EC visit, no cardiac medications, no history of heart disease or ion channel defects. The SE group was divided as epileptic (SE-E) or non-epileptic (SE-NE). Controls (C) were age, gender, and ethnicity-matched children that met the inclusion criteria and had no seizure history. 10 QT and RR intervals per EKG were manually measured from Lead II. QT dynamics were assessed by the QT/RR relationship using linear regression analysis. Comparisons of clinical factors were performed using Student t test or Fisher exact test. Values are expressed as meanSEM. Results: There were 1257 FS, 287 E-Sz, and 435 SE children during the study period. Of these, 23 FS, 8 E-Sz, 16 SE-NE and 14 SE-E children met the inclusion criteria. Compared to control, SE-E exhibited the weakest QT/RR correlation (C: r2=0.80, FS: r2=0.88, E-Sz: r2=0.94, SE-NE: r2=0.66, SE-E: r2=0.61). Additionally, SE-E also had a flattened slope, while FS group had a steeper slope as compared with control (C: 0.290.01, FS: 0.380.01, E-Sz: 0.290.01, SE-NE: 0.280.02, SE-E: 0.170.01, p < 0.0001). No clinically significant factors were associated with altered QT dynamics. Conclusions: Impaired QT dynamics in the SE groups suggest that prolonged seizures can adversely affect ventricular stability and may reflect an increased arrhythmogenic risk following SE, particularly in children with epilepsy. Studies are ongoing to further examine the contribution of epilepsy-related factors to the observed changes in QT dynamics. Funding: K08NS063117 (YCL) Emma Bursick Memorial Fund (YCL) R21NS077028 (AEA)