Measurement of QT Interval and Duration of the QRS Complex at Different ECG Sampling Rates

MARCELO RISK; JULIAN BRUNO; MARIANO LLAMEDO SORIA; PEDRO ARINI; RICARDO TABORDA

COMPUTERS IN CARDIOLOGY

IEEE

Año: 2005 vol. 32 p. 495 - 498

0276-6574

The precise measurement of QT interval and QRS complex duration is important to characterize the elec- trical cardiac activity of the surface ECG. Variations of these intervals were evaluated when ECG sampling rate changes. The ECG recordings used in this study (n = 78) were obtained from a combination of pharmacologi- cal blockage and postural changes. The ECG recordings were originally sampled at 500 Hz, and then were down- sampled by intervals of 25 Hz until the minimum sampling rate of 75 Hz. In all cases the down-sampling was imple- mented using cubic spline interpolation. The QRS com- plex duration, RR and QT intervals for each subject, con- dition and sampling rate were measured. The QT inter- val was corrected using two different techniques: Bazzett and individualized QT corrections. The effect of the sam- pling rate was modeled with an exponential decay func- tion, which was used later to measure where the exponen- tial reaches an asymptotic value (at 5 ). The 5 value for uncorrected QT was at 290 Hz, corrected QT with Bazzett was at 303 Hz, and corrected QT with Individual method was at 253 Hz, finally QRS complex duration was at 297 Hz. An overestimation of the QT interval and QRS com- plex duration was observed when decreasing the sampling rate below 300 Hz.