TY - JOUR
T1 - A Frequency Domain Analysis of Spatial Organization of Epicardial Maps
AU - Sih, Haris J.
AU - Sahakian, Alan V.
AU - Arentzen, Carl E.
AU - Swiryn, Steven
N1 - Funding Information:
Manuscript received December 27, 1993; revised February 22, 1995. This work was supported in part by the Hartman Family Fund and the Virginia and Robert Neuschel Fund, Evanston, IL. H. J. Sih is with the Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, IL 60201 USA. A. V. Sahakian is with the Department of Electrical Engineering and Computer Science and the Department of Biomedical Engineering, Northwestem University, Evanston, IL 60201 USA. C. E. Arentzen is with the Department of Surgery, The Evanston Hospital, Northwestern University Medical School, Evanston, IL 60201 USA. S. Swiryn is with the Department of Medicine, The Evanston Hospital, Northwestem University Medical School, Evanston, IL 60201 USA. IEEE Log Number 941 1743.
PY - 1995/7
Y1 - 1995/7
N2 - Mapping of organized rhythms like sinus rhythm uses activation times from individual electrograms, and often assumes that the map for a single activation is similar to maps for subsequent activations. However, during fibrillation, activation times and electrograms are not easy to define, and maps change from activation to activation. Volume and complexity of data make analysis of more than a few seconds of fibrillation difficult. Magnitude Squared Coherence (MSC), a frequency domain measure of the phase consistency between two signals, can be used to help interpret longer data segments without defining activation times or electrograms. Sinus rhythm, flutter, and fibrillation in humans and swine were mapped with an array of unipolar electrodes (2.5 nun apart) at 240 sites on the atrial or ventricular epicardium. Four-second data segments were analyzed. One site near the center of the array was chosen ad hoc as a reference. MSC maps were made by measuring mean MSC from 0–50 Hz between every point in the array relative to the reference. Isocoherence contours were drawn. The effects of bias in the coherence estimate due to misalignment were investigated. Average MSC versus distance from the reference was measured for all rhythms. Results indicate that in a 4-s segment of fibrillation, there can exist some phase consistency between one site and the reference and little or none between a second site and the reference even when both sites are equidistant from the reference. In fibrillation, isocoherence contours are elongated and irregularly shaped, reflecting longterm, but nonuniform, spatial organization. That is, activation during fibrillation cannot be considered as random over a 4-s interval. Bias in the coherence estimate due to misalignment is significant for sinus rhythm and flutter, but can be corrected by manual realignment. Average MSC drops with distance for all rhythms, being most pronounced for fibrillation. MSC maps may provide insights into long-term spatial organization of rhythms that would otherwise be cumbersome and difficult to interpret with standard time domain analysis.
AB - Mapping of organized rhythms like sinus rhythm uses activation times from individual electrograms, and often assumes that the map for a single activation is similar to maps for subsequent activations. However, during fibrillation, activation times and electrograms are not easy to define, and maps change from activation to activation. Volume and complexity of data make analysis of more than a few seconds of fibrillation difficult. Magnitude Squared Coherence (MSC), a frequency domain measure of the phase consistency between two signals, can be used to help interpret longer data segments without defining activation times or electrograms. Sinus rhythm, flutter, and fibrillation in humans and swine were mapped with an array of unipolar electrodes (2.5 nun apart) at 240 sites on the atrial or ventricular epicardium. Four-second data segments were analyzed. One site near the center of the array was chosen ad hoc as a reference. MSC maps were made by measuring mean MSC from 0–50 Hz between every point in the array relative to the reference. Isocoherence contours were drawn. The effects of bias in the coherence estimate due to misalignment were investigated. Average MSC versus distance from the reference was measured for all rhythms. Results indicate that in a 4-s segment of fibrillation, there can exist some phase consistency between one site and the reference and little or none between a second site and the reference even when both sites are equidistant from the reference. In fibrillation, isocoherence contours are elongated and irregularly shaped, reflecting longterm, but nonuniform, spatial organization. That is, activation during fibrillation cannot be considered as random over a 4-s interval. Bias in the coherence estimate due to misalignment is significant for sinus rhythm and flutter, but can be corrected by manual realignment. Average MSC drops with distance for all rhythms, being most pronounced for fibrillation. MSC maps may provide insights into long-term spatial organization of rhythms that would otherwise be cumbersome and difficult to interpret with standard time domain analysis.
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U2 - 10.1109/10.391158
DO - 10.1109/10.391158
M3 - Article
C2 - 7622155
AN - SCOPUS:0029329153
SN - 0018-9294
VL - 42
SP - 718
EP - 727
JO - IEEE Transactions on Biomedical Engineering
JF - IEEE Transactions on Biomedical Engineering
IS - 7
ER -