Abstracts

Rationale: Prolonged corrected QT (QTc) interval is a significant risk factor for fatal cardiac arrhythmias. EEG is a test commonly used to diagnose and differentiate between paroxysmal events (i.e., seizure, syncope). The interpretation of QTc is often neglected during routine EEG reading. We aim to compare the incidence of prolonged QTc interval, as seen in the EKG recording of the EEG, in cohorts of children presenting with seizure, syncope or attention deficit and hyperactivity disorder (ADHD). Methods: The EEG database of our institution was searched to identify the 50 most recent recordings of patients with a history of seizure, syncope or ADHD. EKG QT and RR interval were measured digitally and randomly on three occasions in each EEG blindly to patients’ diagnoses. The average of the three sets was used for analysis. QTc was calculated as the QT interval divided by the square root of the RR interval (Bazett’s method). Positive results were reviewed by an experienced pediatric cardiologist (ACO). The incidence of abnormal QTc, defined as >0.46 was compared among groups using Chi-square test. The group means were compared using ANOVA with Bonferroni correction. Results: The incidence of prolonged QTc in the seizure, syncope and ADHD groups was 2/50 (4%), 7/50 (14%) and 1/50 (2%) respectively (p=0.036, Chi-square). The mean ± SD of QTc values for the three groups were 0.405 ± 0.035, 0.424 ± 0.04 and 0.414 ± 0.037 respectively (p=0.035, syncope group, compared to seizure group, ANOVA). Conclusions: The incidence of prolonged QTc as measured in the EEG was unexpectedly high in children presenting with syncope, ADHD or seizures, particularly in the former. These data support the concept that QTc evaluation should be emphasized during routine EEG reading, as it may confirm suspected diagnoses or help to identify cases of undiagnosed abnormalities. Prospective studies comparing EEG-EKG tracings with 12-lead EKG are warranted to confirm these results.