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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 30 (1992), S. 277-282 
    ISSN: 1741-0444
    Keywords: Frequency analysis ; Highly amplified ECG ; Maximum entropy spectral estimation ; Ventricular late potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Recognition of patients with high risk for ventricular tachycardia (VT) or sudden cardiac death is of high clinical importance. We have investigated the efficiency of maximum entropy spectral estimation (MES) to detect such risk patients on the basis of highly amplified surface ECG. In comparison with the traditionally applied periodogram (fast Fourier transform), the MES produces sharper and more pronounced peaks in the power density spectrum (PS). The main problem is the influence of residual noise (after averaging), which often leads to additional components in the PS. To completely avoid this negative noise influence we developed a new algorithm, called the variance subtraction method. In a first clinical investigation 86 per cent of patients with myocardial infarction and ventricular tachycardia have shown frequency components above 80 Hz in the PS compared with healthy persons where no frequency components above this 80 Hz level could be detected.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 680-685 
    ISSN: 1741-0444
    Keywords: Heart rate variability ; Renormalised entropy ; Risk stratification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Standard time and frequency parameters of heart rate variability (HRV) describe only linear and periodic behaviour, whereas more complex relationships cannot be recognised. A method that may be capable of assessing more complex properties is the non-linear measure of ‘renormalised entropy’. A new concept of the method, REAR, has been developed, based on a non-linear renormalisation of autoregressive spectral distributions. To test the hypothesis that renormalised entropy may improve the result of high-risk stratification after myocardial infarction, it is applied to a clinical pilot study (41 subjects) and to prospective data of the St George's Hospital post-infarction database (572 patients). The study shows that the new REAR method is more reproducible and more stable in time than a previously introduced method (p〈0.001). Moreover, the results of the study confirm the hypothesis that on average, the survivors have negative values of REAR (−0.11±0.18), whereas the non-survivors have positive values (0.03±0.22, p〈0.01). Further, the study shows that the combination of an HRV triangular index and REAR leads to a better prediction of sudden arrhythmic death than standard measurements of HRV. In summary, the new REAR method is an independent measure in HRV analysis that may be suitable for risk stratification in patients after myocardial infarction.
    Type of Medium: Electronic Resource
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