The Relationship between QT Interval and RR Interval Using Wavelet Transform

Abstract

<Background and purpose> Atrial fibrillation (Af) associated with basic heart disease is known to be complicated with severe ventricular tachyarrhythmias. QT interval is one of the predictors of the cardiac arrhythmia development. However, it is not easy to determine the end of the T wave because of the baseline shift by fibrillation waveforms. We previously developed a new QT interval measurement system using wavelet transform, which enables automatic QT measurement which shows mean error of less than 5ms. The purpose of this study is to assess beat to beat QT interval as well as RR interval in Af. <Cases and method> Five minutes continuous ECG recording (lead II) was performed in 11 Af cases and 6 healthy sinus rhythm cases (SR) . QT intervals were identified by originally developed automated measurement system, in which wavelet transform method (mother wavelet: Mexican hat) was applied to determine the terminal portion of T wave, even if the baseline was fluctuated by the fibrillation waveform. <Results and conclusion> In Af cases, the fluctuation of QT interval by the fluctuation of RR interval was different from SR. However, both SR and Af may actually show a same logarithm-shaped response, and a difference of the variation area for the heart rate interval may contribute in the difference of the distribution. New QT interval measurement method using wavelet transform method is useful in Af cases even if fibrillation waveform interfere the end of T wave.