A new method for the simultaneous automatic measurement of the RR and QT intervals in ambulatory ECG recordings

Since the QT interval changes with time under the influence of heart rate and autonomic input, it needs to be analyzed on a long-term basis. The authors present a method for automatic QT measurement based on linear regression analysis, by which the end of the T wave is determined as the crossing point between the baseline and the tangent to the last branch of the T wave itself. The automatic QT measurement is coupled with the analysis of the heart rate variability when examining 24-h Holter recordings. The focus is on the characteristics of the algorithm for measuring the QT interval and the results of its validation. This procedure proved to be accurate when compared with manual measurements and, to some extent, was little affected by the sampling rate. This feature could substantially reduce the amount of data to be analyzed and quicken the procedure without appreciably affecting the quality of the analysis