Modified П-shaped finite impulse response filter for stabilization of QT measurement

In drug-safety study, the measurements of QT intervals require to have a level of precision to detect small drug-induced prolongation (~ 5 msec). This paper discusses a modified approach of Π-shaped FIR Filter to optimize the quality of signal and improve the stability of QT/QTc interval measurements. The proposed filter is designed to have a time-dependent frequency characteristic based on pre-defined fiducial points of the EKG. The radius of regular Π-shaped FIR filter is modified to obtain different frequency characteristics between QRS and the repolarization interval. The evaluation of QTc stability was based on the standard deviations of QTc interval when measured from Holter ECG signals from 20 healthy subjects filtered with the proposed five versions of the Π-shaped FIR filter. The result shows that the standard deviation of QTc interval with hybrid filter revealed an averaged 50% increase of stability in comparison to other filter, such as the regular Π-shaped FIR filter, and the traditional FIR filters.