Dynamic properties of QT intervals

Five dynamic models of QT/RR coupling are tested on measurements of tilt table test at 19 healthy individuals. RMS of error signal (difference between measured and computed QT) and correlation coefficient (R) between error signal and RR are analyzed. Four models were based on weighted average of RR intervals-constant weighting, exponential weighting with linear dependency and nonlinear dependency and the new model given by exponential weighting, linear dependency and direct coupling with RR-MDCEXP. The fifth model was based on transfer function-MTRF. According to both parameters, RMS (P < 0.001), R (P < 10^-7) MDCEXP and MTRF are the best. Between MDCEXP and MTRF does not exist significant differences.