Amplitude differences least squares method applied to temporal cardiac beat alignment

• Published in: Journal of physics. Conference series 2007-11, Vol.90 (1), p.012073
• Main Authors: Correa, R O, Laciar, E, Valentinuzzi, M E
• Format: Article
• Language: English
• Subjects: Alignment; Amplitudes; Cross correlation; High resolution; Interference; Least squares method; Physics; Power lines; Synchronism; Tachycardia; White noise
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/90/1/012073

High resolution averaged ECG is an important diagnostic technique in post-infarcted and/or chagasic patients with high risk of ventricular tachycardia (VT). It calls for precise determination of the synchronism point (fiducial point) in each beat to be averaged. Cross-correlation (CC) between each detected beat and a reference beat is, by and large, the standard alignment procedure. However, the fiducial point determination is not precise in records contaminated with high levels of noise. Herein, we propose an alignment procedure based on the least squares calculation of the amplitude differences (LSAD) between the ECG samples and a reference or template beat. Both techniques, CC and LSAD, were tested in high resolution ECG's corrupted with white noise and 50 Hz line interference of varying amplitudes (RMS range: 0-100μV). Results point out that LSDA produced a lower alignment error in all contaminated records while in those blurred by power line interference better results were found only within the 0–40 μV range. It is concluded that the proposed method represents a valid alignment alternative.