1. May 20-22, 2010, Brasov, Romania 12th International Conference on Optimization of Electrical and Electronic Equipment OPTIM 2010 Electrocardiogram Baseline Wander Removal Using Stationary Wavelet Approximations Beatrice ARVINTI, Dumitru TOADER, Marius COSTACHE, Alexandru ISAR “Politehnica” University, Timisoara, Romania

2. May 20-22, 2010, Brasov, Romania Contents Introduction Proposed method Simulation parameters Simulation results Conclusion

3. May 20-22, 2010, Brasov, Romania Objectives To propose a new method for the correction of the baseline wander of ECGs To reduce the required computation time To enhance further development of a non- supervised method

4. May 20-22, 2010, Brasov, Romania Introduction In practice, ECG signals are affected by noise Fig.1. “Noisy” ECG signal  Disadvantage:  a wandering of the baseline of the ECG, which can mask significant features  failure of the processing task

5. May 20-22, 2010, Brasov, Romania Estimation of the “overall tendency” of the ECG through multiresolution analysis (MRA) Procedure steps:  Estimation of the baseline wander using low-pass filtering  Elimination of the baseline wander by subtraction from the acquired ECG Proposed method

6. May 20-22, 2010, Brasov, Romania Proposed method Fig. 2. The architecture of the proposed baseline’s correction system ECG SWT d k =0 ISWT + Baseline’s estimator Corrected ECG The Stationary Wavelet Transform (SWT)

7. May 20-22, 2010, Brasov, Romania Proposed method Fig. 3. The scheme of the system that computes the stationary wavelet transform. The systems with the impulse responses h k are low-pass filters and the systems with impulse responses g k are high-pass filters. The impulse response of the filter: The frequency response of the used filter:

8. May 20-22, 2010, Brasov, Romania Simulation parameters Parameters: o the mother wavelets used for the computation of the SWT  the first mother wavelets proposed by Ingrid Daubechies: Dau_2 o the sampling frequency of the ECG: 360 Hz o the cut-off frequency: < 1/T o the resolution level K :

9. May 20-22, 2010, Brasov, Romania Simulation results Fig 4. First three beats. a) Before treatment (the baseline is represented in red), b) After treatment (the new baseline is represented in green) a) b) Best result

10. May 20-22, 2010, Brasov, Romania Simulation results Fig. 5. Simulation results obtained for the ECG 103 of the MIT-BIH arrhythmia database with the start moment at 18’20’’. a) Original waveform (in blue) and the estimation of the baseline (in red) and b) Result of the compensation method Worst result

11. May 20-22, 2010, Brasov, Romania Conclusion The proposed method is a non-supervised method The estimation of the ECG’s baseline is done with the aid of the SWT, computed using the mother wavelets Dau-2 for 8 decomposition levels The equivalence of the proposed estimation method with a low-pass filtering of the ECG using a special filter The method works well for ECGs moderately distorted by the drifts of their baseline The proposed method is robust Requires less computational effort

12. May 20-22, 2010, Brasov, Romania