Abstracts

Rationale: To compare the accuracy of EEG -QT measurements with simultaneous 12 lead EKG-QT in pediatric patients as a quality improvement initiative. Methods: Prospective QT measurements from simultaneous 12 lead EKGs were compared with EEG QT (n=22). Indications for EEGs included paroxysmal spells (n=9), primary seizure disorder (n=11) or syncope(n=2). EEGs were recorded digitally at the standard paper speed of 30 mm/ sec at a gain of 7 mm/ v. The QT interval from 10 second print out of a single lead EKG (Lead I) was measured manually. Measurements were made by two different technicians and a neurologist for inter-observer variability and averaged. A standard 12 lead EKG was recorded at a paper speed of 25 mm/sec and a gain of 10mm/ v. Average of 3 measurements of the QT interval from leads I, II and V5 were calculated by a cardiac electrophysiologist. Statistics: Paired t-test was performed to compare the difference between individual and average EEG-QT and EKG-QT intervals. A p-value of <0.05 was considered to be statistically significant. Results: Mean age of subjects was 8.1 years (range 5m-15years). There were 14 males (64%). Inter observer variability in EEG-QT measurements was present between the 2 technician readings in 19/22 patients (86%)(mean difference 20 ms; range 10-50 ms) but not between one of the technicians and the physician. The average of 2 measurements of EEG-QT intervals (276 30ms) was significantly shorter in comparison to EKG-QT (310 30ms) (p<0.0001). Due to the presence of significant inter-observer variability, EEG-QT obtained by individual EEG technicians were also compared with EKG-QT. These were also significantly shorter. (Tech 1: 280 40 ms; Tech 2 and neurologist: 272 30ms) (p<0.0001). Conclusions: There is high inter-observer variability and a shorter QT interval with under estimation of up to 55 ms in the EEG- QT compared to EKG -QT, making such measurements unreliable. Different paper speeds, signal gain and difficulties in identifying the termination of T wave could be potential factors causing these differences. We therefore recommend that EKG during routine EEG recordings be used to detect artifacts and not for determination of QT intervals.