Journal of electrocardiology
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Comparative Study
Assessment of ischemic changes by ambulatory ECG-monitoring: comparison with 12-lead ECG during exercise testing.
The accuracy of commercially available ambulatory electrocardiographic monitoring (AEM) systems for reproducing ischemic changes has been questioned. Since these systems are widely used for evaluation of ST-segment changes, both for prognostic purposes and for assessment of the efficacy of antiischemic drugs, such doubts must be clarified. For this purpose, we recorded electrocardiograms (ECGs) during exercise testing, using split leads, simultaneously with a 12-lead electrocardiograph and with the Marquette AEM recorder. ⋯ Of the 19 patients with negative exercise tests only 1 patient had a 1-mm ST-segment depression on AEM. Thus, of the 48 patients studied, similar responses were observed in 47. The results of indicate that the Marquette AEM system is as accurate as the 12-lead ECG in detecting ischemic changes and in assessing their severity.
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Comparative Study
Effect of electrode positioning on ECG interpretation by computer.
The aim of this study was to assess the variability in automated electrocardiogram (ECG) interpretation due to electrode positioning variations. Such variations were simulated by using a set of 746 body surface potential mappings from apparently healthy individuals and patients with myocardial infarction or left ventricular hypertrophy. Four types of electrode position changes were simulated, and the effect on ECG measurements and diagnostic classifications was determined by a computer program. ⋯ In the 40 cases with large diagnostic changes, the cardiologist made no change in 18 cases. The effect of electrode position changes on ECG classification by an expert cardiologist was about half of the effect determined by computerized ECG classification. The effects on classification are significant; therefore, correct placement of chest electrodes remains mandatory.
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A patient with spontaneous left-sided pneumothorax and unusual, phasic voltage variations in the electrocardiogram (ECG), which fluctuated depending on respiration, was observed. After intercostal tube drainage, these variations disappeared. The respiratory changes in the thorax seem to be a cause of these ECG findings.
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Comparative Study
ECG identification of left ventricular hypertrophy. Relationship of test performance to body habitus.
Obesity is associated with the presence of left ventricular hypertrophy (LVH) and, conversely, with decreased sensitivity of the electrocardiogram (ECG) for LVH due to attenuating effects on QRS amplitudes. Although the Framingham-adjusted Cornell voltage, incorporating age, sex, and body mass index (BMI), was developed to correct for the effects of obesity on the accuracy of the ECG, the impact of body habitus on ECG detection of LVH for newer, more accurate ECG criteria based on the time-voltage area under the QRS complex has not been determined. The authors examined the test accuracy of the Sokolow-Lyon voltage, Cornell voltage, Cornell product (product of QRS duration and Cornell voltage), Framingham-adjusted Cornell voltage, and time-voltage area of the horizontal plane vector QRS for the detection of echocardiographic LVH in relation to body habitus in 250 patients. ⋯ Specificity varied with body habitus only for the Framingham-adjusted Cornell voltage: 100% in normal-weight vs 95% in overweight patients (P < .05). Thus, accuracy of the Framingham-adjusted Cornell voltage and Sokolow-Lyon voltage varies significantly with body habitus. In contrast, accuracy of the Cornell voltage and the Cornell product appears less dependent on BMI, and the time-voltage area of the QRS minimizes the effects of obesity on the accuracy of the ECG for LVH.
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Case Reports
Complete atrioventricular block with ventricular asystole following infusion of intravenous phenytoin.
A case of complete atrioventricular block with ventricular asystole in a patient receiving intravenous phenytoin is presented. Although the potential for hypotension is generally recognized with the intravenous administration of phenytoin, conduction abnormalities are rarely reported. The differential diagnosis of atrioventricular block and the effects of phenytoin on cardiac conduction are discussed.