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   -> Volume 6, Issue 5

Preprint: Contribution of wavelets in the ECG analysis
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Jean-Philippe Couderc (

PostPosted: Mon Apr 14, 1997 3:30 pm    
Subject: Preprint: Contribution of wavelets in the ECG analysis
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#2 Preprint: Contribution of wavelets in the ECG analysis

Stratification of Time-Frequency abnormalities
in the Signal-Averaged High-Resolution ECG in Post-infarction Patients
with and without Ventricular Tachycardia and Congenital Long QT syndrome.=

Authors : Jean Philippe Couderc, MSc,* Samir Fareh, MD,** Philippe
Chevalier, MD,** Jocelyne Fayn, PhD,* Gilbert Kirkorian, MD,** Paul
Rubel, PhD,*** Paul Touboul, MD,** * INSERM U121, H=F4pital
Cardiologique, Lyon, France **Electrophysiology Department, H=F4pital
Cardiologique, Lyon, France ***Information Systems Engineering
Laboratory (LISI), INSA-LYON, France


Abstract: Having developed sound mathematical techniques that allow
precise mapping of cardiac signals in the time-frequency (TF) and
time-scale planes, the next important issue is to extract from these
representations information that best reflect the electrophysiologic
and anatomic derangement unique to patients at risk of arrhythmias and
other cardiac diseases. In this paper, we present a new method that
stratifies the magnitude of the TF transforms of abnormal cardiac
signals into distinguishing features by comparing the means of the
coefficients of the TF transforms of any study population to the
corresponding means of a control population by using a standard ANOVA
technique. This results in a 3-D mapping of the HRECG into the time,
frequency and p-value space. Significant energy increases are given
positive p-values, depressed energies negative values, and ranked
according to a color scale. The method was tested on 2 study
populations: post-myocardial infarction patients with (MI+VT, N3D23)
and without (MI-VT, N3D40) documented sust ained ventricular
tachycardia, congenital long QT syndrome patients (LQTS, N3D19). Two
groups of healthy (N3D31 and N3D40) were used as a reference group
matched in sex. The study results were based on Morlet analyzing
wavelets, with frequencies ranging from 40 to 250 Hz in 10
logarithmically progressing scales, computed ms per ms over a 350 ms
analyzing time window, starting from 100 ms before the onset of the
QRS. The MI+VT patients displayed significantly increased high
frequency components in the 40 to 250 Hz frequency range,
corresponding to prolonged QRS duration, and late potentials in the
area from 80 to 150 ms after QRS onset. Significantly depressed energy
(p<10-4) was also observed for the 40 to 106 Hz frequency range in the
first 50 ms of the QRS complex, mainly in lead Y and in the magnitude
vector. In LQTS patients, significa nt modifications (p<10-2) were
observed in the first half of QRS and in the ST segment, in all leads,
revealing anomalies in the genesis of the ventricular depolarization
and repolarization process. In conclusion, we propose a new method for
the stratification of abnormal time-frequency components occurring in
the signal-averaged HR-ECG of patients at risk of ventricular
tachycardia and fibrillation under different pathologic conditions.

Couderc J Ph, Fareh S, Chevalier Ph, Fayn J, Kirkorian G, Rubel P,
Toubou l P.
Stratification of Time-Frequency Abnormalities in the Signal Averaged
ECG in Post-Infarction Patients and Congenital Long QT Syndrome.
In: J. Electrocardiol.1996, 29 (suppl):180-88

Jean-Philippe Couderc, PhD
University of Rochester
Heart Research
601 Elwood Avenue, No 653
Rochester, NY, 14620

Phone: (716) 275 1096
Fax : (716) 473 2751
All times are GMT + 1 Hour
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