One of the greatest challenges in analysis of the atrial rhythm from the ECG is to distinguish the atrial component from the large ventricular components. Our aim was to compare three techniques of atrial rhythm extraction from three groups working on this problem. 12-lead ECG data from 7 patients in atrial fibrillation were analysed. For extraction of the atrial rhythm, spatiotemporal QRST cancellation was performed by the Lund group, blind source separation by the Valencia group, and principal component analysis by the Newcastle group. Peak atrial frequency was determined by Fourier transform of the signal with the largest atrial activity. All algorithms were successful in distinguishing the atrial rhythm from the low frequency ventricular rhythm. The mean (range) atrial frequency was 6.5 (5.9 -7.6) H z (Lund), 6.7 (5.7 -7.9) Hz (Valencia) and 6.5 (5.9 -8.2) H z (Newcastle). There were no SigniJicant differences between the atrial frequencies estimated by each of the techniques.
IntroductionAtrial fibrillation is a common arrhythmia in old age with increased risk of stroke and death [ 1 I. The arrhythmia is diverse in its presentation and there are a number of different treatments which aim to restore sinus rhythm [2]. Analysis of the atrial rhythm, before, during and after treatment, provides a means by which to quantify the effects of treatment and to assess the effectiveness of treatment on the different characteristic types of atrial fibrillation. One of the greatest challenges in analysis of the atrial rhythm from the ECG is to distinguish the atrial component from the large ventricular components, namely the QRS and T waves.In this collaborative project, our aim was to compare, by analysis of the main atrial frequency, three techniques of atrial rhythm extraction from three groups working on this problem. The Lund group have developed spatiotemporal QRST cancellation, an extension of a technique for subtraction of the QRST waveform from each ECG lead which has been used for a number of years. Blind source separation and principal component analysis have only recently been applied to the problem of atrial rhythm extraction by the Valencia and Newcastle groups respectively, but are well established signal processing techniques in the fields of image analysis and data communications.
Methods
Data12-lead ECGs of 7 patients with atrial fibrillation were recorded to computer at the Freeman Hospital, Newcastle.The sampling rate was 500 Hz and the amplitude resolution was less than 5 pV. Recording duration analysed was 60 s. The ECGs were copied and distributed to the groups in Lund and Valencia. Ventricular rate was derived for each patient from the mean heart rate over the 60 s recording.
Atrial rhythm extraction techniques
Spatiotemporal QRST cancellationThe Lund group applied the spatiotemporal QRST cancellation technique [3]. The ECGs were resampled at 1 kHz and filtered using a 0.3 Hz high pass filter to reduce baseline wander prior to QRST cancellation. Beat detection and cross-correlation based beat class...
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