Enhancing the Precision of ECG Baseline Correction: Selective Filtering and Removal of Residual Error

Shusterman, Vladimir; Shah, Syed Afaq Ali; Beigel, Anna; Anderson, Kelly P.

doi:10.1006/cbmr.2000.1539

Cited by 42 publications

(35 citation statements)

References 22 publications

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“…7 To eliminate the low-frequency artifacts caused by baseline wander, a previously validated, adaptive algorithm for accurate removal of baseline drifts with a minimal distortion of repolarization complexes has been used. 36 Theoretically, the dynamics of TWA at 0.5 c/b could be influenced by a subharmonic of the fundamental frequency at 0.25 c/b. 1 To rule out this possibility, the increase in the magnitude of TWA has been confirmed by 3 independent methods.…”

Section: Repolarization Analysis In Ambulatory Ecg Recordingsmentioning

confidence: 99%

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

2006

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Background-Analysis of repolarization instability, manifested by T-wave alternans (TWA), has proved useful for arrhythmia risk assessment. However, temporal relations between TWA and the spontaneous initiation of ventricular tachyarrhythmias (VTA) in humans are unknown. We examined continuous dynamics of repolarization in Holter electrocardiograms with spontaneous sustained (Ͼ30 seconds) VTA. Methods and Results-Ambulatory electrocardiograms from 42 patients (79% with ischemic heart disease; left ventricular ejection fraction, 37Ϯ15%) were digitized, and the lead with the highest magnitude of the T wave was selected for analysis. TWA was examined by the modified moving average and intrabeat average analyses. To examine non-TWA (longer-period) oscillations in the repolarization segment, spectral energy of oscillations of consecutive T-wave amplitudes was calculated with the use of the short-time Fourier transform. Heart rate variability was assessed with the Fourier transform as well. TWA increased before the onset of VTA and reached a peak value of 23.6Ϯ11.7 V 10 minutes before the event (Pϭ0.0007). Spectral power of the oscillations of consecutive T-wave amplitudes increased nonuniformly, with the greatest increase in the respiratory range (2.6 V 2 ; Pϭ0.005). In the TWA range, the change was smaller but highly pronounced relative to the 60-to 120-minute level (65%; Pϭ0.003). The low-frequency and high-frequency heart rate variability power declined before the arrhythmia (Pϭ0.04 and Pϭ0.06, respectively). Conclusions-The magnitude of repolarization instability, manifested by TWA and beat-to-beat oscillations of T-wave amplitudes at other frequencies, increased before the onset of VTA. Tracking of these dynamics can facilitate timely detection of high-risk periods and may be useful for initiation of preventive treatments.

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Section: Repolarization Analysis In Ambulatory Ecg Recordingsmentioning

confidence: 99%

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

2006

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“…Algorithms taken from the literature were used for the first two stages: baseline drift cancellation [10] and QRS detection [11].…”

Section: A Segmentation Algorithmmentioning

confidence: 99%

Improving ECG Beats Delineation With an Evolutionary Optimization Process

Dumont

Hernández

Carrault

2010

IEEE Trans. Biomed. Eng.

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Abstract-As in other complex signal processing tasks, ECG beat delineation algorithms are usually constituted of a set of processing modules, each one characterized by a certain number of parameters (filter cutoff frequencies, threshold levels, time windows...). It is well recognized that the adjustment of these parameters is a complex task that is traditionally performed empirically and manually, based on the experience of the designer. In this work, we propose a new automated and quantitative method to optimize the parameters of such complex signal processing algorithms. To solve this multiobjective optimization problem, an evolutionary algorithm (EA) is proposed. This method for parameter optimization is applied to a Wavelet-Transform-based ECG delineator that has previously shown to present interesting performances. An evaluation of the final delineator, using the optimal parameters, has been performed on the QT database from Physionet and results are compared with previous algorithms reported in the literature. The optimized parameters provide a more accurate delineation, with a global improvement, over all the criteria evaluated, and over the best results find in the literature, measured of 7.7%, which is a proof of the interest of the approach.

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“…Various approaches have been proposed based typically on smart filtering techniques, such as: moving average filters repeatedly applied to achieve the passband and the stopband specifications 10 ; a combination of the moving average with a FIR filter designed by using a Kaiser window 4 ; an offline bi-directional highpass filter with adaptable cut-off frequency, keeping the RS and ST changes below a selected threshold 7 ; a quasi real-time procedure for estimation of the BW by low-pass filtering and consecutive tracking and elimination of the QRS complexes 6 ; the two-step procedure for baseline estimation by selective ECG filtering and minimization of the residual error 27 ; the nonlinear filter banks allowing low-pass and power-line interference reduction. 17 Adaptive filtering has also been applied, 30 in particular by cubic spline technique combined with adaptive two stage cascade filter 13 or by Kalman model, accepting the hypothesis that the ECG signal can be characterized by an autoregressive model, while the BW is estimated as a first order polynomial.…”

Section: Introductionmentioning

confidence: 99%

Online Digital Filter and QRS Detector Applicable in Low Resource ECG Monitoring Systems

2008

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The present work describes fast computation methods for real-time digital filtration and QRS detection, both applicable in autonomous personal ECG systems for long-term monitoring. Since such devices work under considerable artifacts of intensive body and electrode movements, the input filtering should provide high-quality ECG signals supporting the accurate ECG interpretation. In this respect, we propose a combined high-pass and power-line interference rejection filter, introducing the simple principle of averaging of samples with a predefined distance between them. In our implementation (sampling frequency of 250 Hz), we applied averaging over 17 samples distanced by 10 samples (Filter10x17), thus realizing a comb filter with a zero at 50 Hz and high-pass cut-off at 1.1 Hz. Filter10x17 affords very fast filtering procedure at the price of minimal computing resources. Another benefit concerns the small ECG distortions introduced by the filter, providing its powerful application in the preprocessing module of diagnostic systems analyzing the ECG morphology. Filter10x17 does not attenuate the QRS amplitude, or introduce significant ST-segment elevation/depression. The filter output produces a constant error, leading to uniform shifting of the entire P-QRS-T segment toward about 5% of the R-peak amplitude. Tests with standardized ECG signals proved that Filter10x17 is capable to remove very strong baseline wanderings, and to fully suppress 50 Hz interferences. By changing the number of the averaged samples and the distance between them, a filter design with different cut-off and zero frequency could be easily achieved. The real-time QRS detector is designed with simplified computations over single channel, low-resolution ECGs. It relies on simple evaluations of amplitudes and slopes, including history of their mean values estimated over the preceding beats, smart adjustable thresholds, as well as linear logical rules for identification of the R-peaks in real-time. The performance of the QRS detector was tested with internationally recognized ECG databases (AHA, MIT-BIH, European ST-T database), showing mean sensitivity of 99.65% and positive predictive value of 99.57%. The performance of the presented QRS detector can be highly rated, comparable and even better than other published real-time QRS detectors. Examples representing some typical unfavorable conditions in real ECGs, illustrate the common operation of Filter10x17 and the QRS detector.

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Enhancing the Precision of ECG Baseline Correction: Selective Filtering and Removal of Residual Error

Cited by 42 publications

References 22 publications

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

Upsurge in T-Wave Alternans and Nonalternating Repolarization Instability Precedes Spontaneous Initiation of Ventricular Tachyarrhythmias in Humans

Improving ECG Beats Delineation With an Evolutionary Optimization Process

Online Digital Filter and QRS Detector Applicable in Low Resource ECG Monitoring Systems

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