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Variability in surface ECG morphology: signal or noise?Using data collected from canine models of acute myocardial ischemia, we investigated two issues of major relevance to electrocardiographic signal averaging: ECG epoch alignment, and the spectral characteristics of the beat-to-beat variability in ECG morphology. With initial digitization rates of 1 kHz, an iterative a posteriori matched filtering alignment scheme, and linear interpolation, we demonstrated that there is sufficient information in the body surface ECG to merit alignment to a precision of 0.1 msecs. Applying this technique to align QRS complexes and atrial pacing artifacts independently, we demonstrated that the conduction delay from atrial stimulus to ventricular activation may be so variable as to preclude using atrial pacing as an alignment mechanism, and that this variability in conduction time be modulated at the frequency of respiration and at a much lower frequency (0.02-0.03Hz). Using a multidimensional spectral technique, we investigated the beat-to-beat variability in ECG morphology, demonstrating that the frequency spectrum of ECG morphological variation reveals a readily discernable modulation at the frequency of respiration. In addition, this technique detects a subtle beat-to-beat alternation in surface ECG morphology which accompanies transient coronary artery occlusion. We conclude that physiologically important information may be stored in the variability in the surface electrocardiogram, and that this information is lost by conventional averaging techniques.
Document ID
20040089065
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Smith, J. M.
(Harvard-MIT Division of Health Sciences and Technology Cambridge, Massachusetts 02139, United States)
Rosenbaum, D. S.
Cohen, R. J.
Date Acquired
August 21, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Computers in cardiology
Volume: 14
ISSN: 0276-6574
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAG2-327
CONTRACT_GRANT: N0001479C0-168
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cardiopulmonary
Non-NASA Center

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