BackgroundQRS 3D-voltage-time-integral (VTI) or 3D QRS area is a recently proposed marker for assessing response to cardiac resynchronization therapy (CRT). Automated VTI measurement in patients receiving CRT is affected by pacing artifacts that occur within the QRS.ObjectiveTo demonstrate that automated signal processing can effectively filter out pacing artifacts without appreciably affecting the true ECG signal.MethodsWe devised a two-step filter. First, the true QRS is identified as the peak within the QRS complex that is lower than the 98th percentile of the modified Z-score of detrended data plus 40. The pacing outlier filter deletes all data above this value and fills the gap with a B-spline interpolation function. Second, a median filter is applied to eliminate residual noise. 12 leads each from 30 ECGs with pacing artifacts and 30 non-paced control ECGs were evaluated. We compared the unfiltered ECG with 3 filters (a) Whittaker & Hayes, (b) Laplacian of Gaussian, and (c) our novel method.ResultsAs shown in the Table, among paced ECGs our novel method had the greatest diminution of the pacing artifact (peak-to-peak amplitude from 1.59±1.36 to 0.02±0.04 mV and artifact VTI from 5.28±4.71 to 0.05±0.43 μVs). The novel method had the least impact on the QRS VTI measurement in ECGs with no pacing (from 35.5±20.1 to 35.1±19.9 μVs). The Figure demonstrates complete elimination of pacing artifacts with the novel filter in most cases, without any overt effect on the true ECG signal.ConclusionView Large Image Figure ViewerDownload Hi-res image Download (PPT) BackgroundQRS 3D-voltage-time-integral (VTI) or 3D QRS area is a recently proposed marker for assessing response to cardiac resynchronization therapy (CRT). Automated VTI measurement in patients receiving CRT is affected by pacing artifacts that occur within the QRS. QRS 3D-voltage-time-integral (VTI) or 3D QRS area is a recently proposed marker for assessing response to cardiac resynchronization therapy (CRT). Automated VTI measurement in patients receiving CRT is affected by pacing artifacts that occur within the QRS. ObjectiveTo demonstrate that automated signal processing can effectively filter out pacing artifacts without appreciably affecting the true ECG signal. To demonstrate that automated signal processing can effectively filter out pacing artifacts without appreciably affecting the true ECG signal. MethodsWe devised a two-step filter. First, the true QRS is identified as the peak within the QRS complex that is lower than the 98th percentile of the modified Z-score of detrended data plus 40. The pacing outlier filter deletes all data above this value and fills the gap with a B-spline interpolation function. Second, a median filter is applied to eliminate residual noise. 12 leads each from 30 ECGs with pacing artifacts and 30 non-paced control ECGs were evaluated. We compared the unfiltered ECG with 3 filters (a) Whittaker & Hayes, (b) Laplacian of Gaussian, and (c) our novel method. We devised a two-step filter. First, the true QRS is identified as the peak within the QRS complex that is lower than the 98th percentile of the modified Z-score of detrended data plus 40. The pacing outlier filter deletes all data above this value and fills the gap with a B-spline interpolation function. Second, a median filter is applied to eliminate residual noise. 12 leads each from 30 ECGs with pacing artifacts and 30 non-paced control ECGs were evaluated. We compared the unfiltered ECG with 3 filters (a) Whittaker & Hayes, (b) Laplacian of Gaussian, and (c) our novel method. ResultsAs shown in the Table, among paced ECGs our novel method had the greatest diminution of the pacing artifact (peak-to-peak amplitude from 1.59±1.36 to 0.02±0.04 mV and artifact VTI from 5.28±4.71 to 0.05±0.43 μVs). The novel method had the least impact on the QRS VTI measurement in ECGs with no pacing (from 35.5±20.1 to 35.1±19.9 μVs). The Figure demonstrates complete elimination of pacing artifacts with the novel filter in most cases, without any overt effect on the true ECG signal. As shown in the Table, among paced ECGs our novel method had the greatest diminution of the pacing artifact (peak-to-peak amplitude from 1.59±1.36 to 0.02±0.04 mV and artifact VTI from 5.28±4.71 to 0.05±0.43 μVs). The novel method had the least impact on the QRS VTI measurement in ECGs with no pacing (from 35.5±20.1 to 35.1±19.9 μVs). The Figure demonstrates complete elimination of pacing artifacts with the novel filter in most cases, without any overt effect on the true ECG signal. Conclusion
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