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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 2 (1997), S. 0 
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: During the last 10 years, the signal-averaged electrocardiographic (SAECG) method has been proposed for a growing amount of clinical applications. As a screening method for increased risk of life-threatening ventricular arrhythmias it has demonstrated its value especially in risk stratification after myocardial infarction (Ml) and in the evaluation of patients with unexplained syncope. Its value in risk prediction is now also proven in patients treated with thrombolytic therapy.〈section xml:id="abs1-2"〉〈title type="main"〉MethodsIn patients with dilated cardiomyopathy, hypertrophic cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy, the SAECG is helpful for detecting propensity to spontaneous ventricular tachycardia. P wave signal averaging has been demonstrated to identify patients with propensity to atrial arrhythmias, especially atrial fibrillation. Also, the diagnosis of sick sinus syndrome can be enhanced using this method.〈section xml:id="abs1-3"〉〈title type="main"〉ResultsSo far, the use of SAECG in other patient populations except coronary heart disease has been very limited. However, the results of the recent studies recommend the utilization of this technique also in children and in the elderly, adjusting the findings with the effects of body size and age on the SAECG.〈section xml:id="abs1-4"〉〈title type="main"〉ConclusionsThe SAECG has a definite independent role in improving the predictive accuracy of conventional risk-evaluation techniques in patients with Ml or cardiomyopathy. New patient populations like children and the elderly enlarge the number of patients benefiting of this method. New clinical applications of the SAECG method, such as detection of the propensity to atrial arrhythmias, ischemia and drug effects, are currently merging. Combining the time- and frequencydomain analysis of the SAECG with other methods relevant for the clinical problem is the way to optimize the use of this sophisticated noninvasive technique in clinical practice.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1971
    Keywords: Operated congenital heart defect ; Children ; Signal-averaged electrocardiography ; Late potentials ; Arrhythmias
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract After corrective surgery for congenital heart defects, scars may create fractionation and delay of the electrical signals in the heart muscle, providing a substrate for arrhythmias. Signalaveraged electrocardiograms (SAECGs) were obtained from 33 children after right ventriculotomy, on average 6 years after surgery, and from 38 healthy controls of the same age. The duration of the filtered QRS complex (fQRS), the duration of the low amplitude signal (〈40μV) in the terminal QRS complex (LAS40), and the root mean square amplitude of the terminal 40 ms of the QRS complex (RMS40) were determined. The values of fQRS ≥117 ms, RMS40≤25μV, and LAS40≥35 ms, which were beyond the mean ±2 SD of the healthy controls, were considered abnormal. Most patients had right bundle branch block and therefore a prolonged fQRS. Late potentials were defined as present if both the RMS40 and LAS40 were abnormal. Altogether nine patients (27%) had late potentials. In the patients with late potentials the incidence of serious ventricular arrhythmias was 44% (4 of 9) and in the patients without late potentials 0% (0 of 24). In seven patients with enlargement of the right ventricle, the incidence of arrhythmias was 57% (4 of 7) when late potentials were present and 0% (0 of 7) when they were absent. In the present study late potentials were associated with a history of arrhythmias, especially when the right ventricle was enlarged. Therefore the SAECG may be useful for determining the risk of serious arrhythmia events in children operated for congenital heart defects.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Herzschrittmachertherapie & Elektrophysiologie 11 (2000), S. 229-234 
    ISSN: 1435-1544
    Keywords: Key words Magneto cardiography – arrhythmia risk evaluation –¶signal-averaged electrocardiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have applied various methods to extract parameters from high-resolution magnetocardiographic (MCG) and electrocardiographic (ECG) recordings for characterizing the risk of life-threatening arrhythmias. The methods include detection of late fields and late potentials at the end of the QRS, abnormalities in spectral variability and signal fragmentation during the QRS, and variability in the heart rate. In addition, we have developed methods to convert MCG signals measured with any sensor configurations to a common presentation form. The signal processing methods have been implemented on a user-friendly interface which allows fast and easy use in a clinical environment.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1741-0444
    Keywords: Risk stratification ; Magnetocardiography ; High-resolution electrocardiography ; Ventricular tachycardia ; Sudden cardiac death ; Myocardial infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A new time-domain analysis method, which quantifies ECG/MCG intra-ORS fragmentation, is applied to parts of the QRS complex to identify postmyocardial infarction patients with ventricular tachycardia. Three leads of signalaveraged electrocardiograms and nine leads of magnetocardiograms were band-pass filtered (74Hz to 180Hz). The filtered signals showed fragmentation in the QRS region, which was quantified by the number of peaks M and a score S, that is the product of M and the sum of the peak amplitudes. Both parameters were determined for the first 80 ms of the QRS complex and the total QRS complex in each channel. For classification, the mean-values of the parameters M and S of the three electrical leads and the nine magnetic leads were calculated. Late potential and late field analyses were performed for the same signals. 31 myocardial infarction patients were included, 20 of them with a history of documented ventricular tachycardia (VT). Identification of VT patients using the SAECG led to better results (sensitivity 95%, specificity 91%) considering the entire QRS complex than with the standard late potential analysis suggested by Simson (sensitivity 90%, specificity 73%). For the SAMCG and the entire QRS complex results using the parameters S and M are also better (sensitivity 95%, specificity 100%) than for the late field analysis (sensitivity 90% and specificity 100%). For the first 80 ms, the performance of the parameters M and S is only slightly decreased.
    Type of Medium: Electronic Resource
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