Vectorcardiographic loop alignment and the measurement of morphologic beat-to-beat variability in noisy signals

Abstract

The measurement of subtle morphologic beat-to-beat variability in the electrocardiogram (ECG)/vectorcardiogram (VCG) is complicated by the presence of noise which is caused by, e.g., respiration and muscular activity. A method was recently presented which reduces the influence of such noise by performing spatial and temporal alignment of VCG loops. The alignment is performed in terms of scaling, rotation and time synchronization of the loops. Using an ECG simulation model based on propagation of action potentials in cardiac tissue, the ability of the method to separate morphologic variability of physiological origin from respiratory activity was studied. Morphologic variability was created by introducing a random variation in action potential propagation between different compartments. The results indicate that the separation of these two activities can be done accurately at low to moderate noise levels (less than 10 microV). At high noise levels, the estimation of the rotation angles was found to break down in an abrupt manner. It was also shown that the breakdown noise level is strongly dependent on loop morphology; a planar loop corresponds to a lower breakdown noise level than does a nonplanar loop.

A review of beat-to-beat vectorcardiographic (VCG) parameters for analyzing repolarization variability in ECG signals

“…Thereby, the VCG analysis results may be affected. However, in 1998 and 2000, the articles published by Sörnmo [81] and Astrom et al [5] developed the method for reducing the affect of respiration and muscular activity on VCG loops in a beat-to-beat manner. Mainly, they reduced the respiration influence by performing spatial and temporal maximum-likelihood (ML) alignment of the VCG loops, and this alignment was based on scaling, rotation, and time synchronization of the loops.…”

An evaluation of planarity of the spatial QRS loop by three dimensional vectorcardiography: Its emergence and loss

“…Åström et al [23]studied the QRS Loop Morphology and itsrelationship with the established noise level. By using a measure related to loop planarity, it was demonstrated that the alignment breakdown noise level had an essentially linear dependence on loop planarity.…”

Atrial fibrillatory signal estimation using blind source extraction algorithm based on high-order statistics

“…The above algorithm will converge to a steady solution. For simplicity, we denote the above algorithm containing expressions (2), (6), and (7) by OrigALG.…”