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ECG Analysis (ecg + analysis)

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Medical Sciences	100%

Selected Abstracts

Detailed ECG Analysis of Atrial Repolarization in Humans

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009
Fredrik Holmqvist M.D., Ph.D.
Introduction: Data on human atrial repolarization are scarce since the QRS complex normally obscures its ECG trace. In the present study, consecutive patients with third-degree AV block were studied to better describe the human Ta wave. Methods and Results: Forty patients (mean age 75 years, 17 men) were included. All anti-arrhythmic drugs were discontinued before ECG recording. Standard 12-lead ECGs were recorded, transformed to orthogonal leads and studied using signal-averaged P wave analysis. The average P wave duration was 124 ± 16 ms. The PTa duration was 449 ± 55 ms (corrected PTa 512 ± 60 ms) and the Ta duration (P wave end to Ta wave end) was 323 ± 56 ms. The polarity of the Ta wave was opposite to that of the P wave in all leads. The Ta peaks were located at 196 ± 55 ms in Lead Y, 216 ± 50 ms in Lead X, and 335 ± 92 in Lead Z. No correlation was found between P wave duration and Ta duration, or between Ta peak amplitude and Ta duration. The morphology of the Ta wave was similar regardless of the interatrial conduction. Conclusions: The Ta wave has the opposite polarity, and the duration is generally two to three times that, of the P wave. Although the Ta peak may occasionally be located in the PQ interval during normal AV conduction, it is unlikely that enough information can be obtained from analysis of this segment to differentiate normal from abnormal atrial repolarization. Hence, an algorithm for QRST cancellation during sinus rhythm is needed to further improve analysis. [source]

Impact of advanced exercise ECG analysis on cost of coronary artery disease management

JOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 4 2010
Riccardo Bigi PhD
Abstract Background, Conventional analysis of exercise electrocardiogram (EX-ECG) has limited accuracy. This study aims to evaluate the potential impact of improving EX-ECG accuracy on costs of diagnosis and number of misdiagnoses of coronary artery disease (CAD). Methods, A decision-tree model was simulated including sequential application of diagnostic procedures for suspected CAD. The model was structured in two main branches (presence or absence of CAD). A probabilistic sensitivity analysis was then performed for several combinations of improvement in test sensitivity and specificity. Results, A clear trend in cost reduction was observed at improving EX-ECG specificity (about 8,8.5 million dollars, corresponding to a 5.6,7.6% reduction according to the prevalence level). Wrong diagnoses counted for 9,13% of test. Improvements in test parameters lead to reductions in wrong diagnoses, especially when increasing specificity (8.8,12.5%). Conclusions, A proper improvement in EX-ECG sensitivity and specificity would have a relevant impact on the costs of CAD management, while reducing the number of misdiagnoses. [source]

Philips QT Interval Measurement Algorithms for Diagnostic, Ambulatory, and Patient Monitoring ECG Applications

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
F.A.C.C., Sophia H. Zhou Ph.D.
Background: Commonly used techniques for QT measurement that identify T wave end using amplitude thresholds or the tangent method are sensitive to baseline drift and to variations of terminal T wave shape. Such QT measurement techniques commonly underestimate or overestimate the "true" QT interval. Methods: To find the end of the T wave, the new Philips QT interval measurement algorithms use the distance from an ancillary line drawn from the peak of the T wave to a point beyond the expected inflection point at the end of the T wave. We have adapted and optimized modifications of this basic approach for use in three different ECG application areas: resting diagnostic, ambulatory Holter, and in-hospital patient monitoring. The Philips DXL resting diagnostic algorithm uses an alpha-trimming technique and a measure of central tendency to determine the median QT value of eight most reliable leads. In ambulatory Holter ECG analysis, generally only two or three channels are available. QT is measured on a root-mean-square vector magnitude signal. Finally, QT measurement in the real time in-hospital application is among the most challenging areas of QT measurement. The Philips real time QT interval measurement algorithm employs features from both Philips DXL 12-lead and ambulatory Holter QT algorithms with further enhancements. Results: The diagnostic 12-lead algorithm has been tested against the gold standard measurement database established by the CSE group with results surpassing the industrial ECG measurement accuracy standards. Holter and monitoring algorithm performance data on the PhysioNet QT database were shown to be similar to the manual measurements by two cardiologists. Conclusion: The three variations of the QT measurement algorithm we developed are suitable for diagnostic 12-lead, Holter, and patient monitoring applications. [source]

Lack of Impact of Myocardial Ischemia on the Signal-Averaged ECG Assessment by Time-Domain Analysis

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2002
Michael A. E. Schneider M.D.
Background: Late potentials represent an arrhythmogenic substrate in chronically infarcted myocardium. It is hypothesized that acute transient ischemia enhances anisotropic electrical ventricular activation and facilitates reentry mechanisms. Study aim was the prospective assessment of the impact of dipyridamole-induced myocardial ischemia on the signal-averaged ECG. Methods: Dipyridamole stress thallium-201 SPECT imaging was utilized to avoid noise contamination of the signal-averaged ECG from exercise and to document evidence and localization of myocardial ischemia or persistent perfusion defects in 68 patients with suspected coronary artery disease. Before and during dipyridamole-induced vasodilatation serial signal-averaged ECG was performed to evaluate the influence of transient ischemia on the occurrence of late potentials. Results: There was a significant difference between heart rate at rest and heart rate under dipyridamole influence in patients with inducible ischemia (70 ± 13 vs. 87 ± 13; P < 0.0001) in contrast to patients without dipyridamole-induced ischemia (74 ± 20 vs. 80 ± 16; n.s.). The number of averaged beats and achieved noise level was comparable between both groups. Thirty-three of 68 patients (49%) revealed dipyridamole-induced ischemia; however, no changes of the SAECG parameters, such as QRS, RMS, LAS at 25,250 and 40,250 Hz bandpass filtering in the leads X, Y, Z and vector magnitude, respectively, were observed as a result of ischemia. Conclusion: These results suggest that transient myocardial ischemia does not affect the signal-averaged ECG. Clinically, the signal-averaged ECG analysis seems not to be helpful in identifying patients with silent ischemia. A.N.E. 2002;7(3):191,197 [source]