PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ECG”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed2005

ECG patterns confounding the ECG diagnosis of acute coronary syndrome: left bundle branch block, right ventricular paced rhythms, and left ventricular hypertrophy.

The ECG has limitations in the evaluation of the chest-pain patient, including the presence of confounding ECG patterns; the ECG patterns that confound the diagnosis of acute myocardial infarction(AMI) include left bundle branch block (LBBB), ventricular paced rhythms (VPR), and left ventricular hypertrophy (LVH). These patterns produce new ST-segment/T-wave abnormalities, which are the new normal findings in these patients and may lead the clinician astray in two distinct instances: (1) diagnosing ECG change related to acute coronary syndromes (ACS) when the abnormality results solely from the confounding pattern; and (2) not acknowledging the confounding nature of these ECG patterns in the evaluation of potential ACS, thereby placing excessive diagnostic confidence in the ECG. This article highlights the diagnostic dilemma encountered in these confounding ECG patterns; the discussion focuses on the expected ECG abnormalities in these patients and the findings seen in ACS.

Bundle-Branch Block↗
PubMed1998

A standardized procedure for locating and documenting ECG chest electrode positions: consideration of the effect of breast tissue on ECG amplitudes in women.

Continuing uncertainty exists about standardized procedures for the placement of electrocardiographic (ECG) chest electrodes, technical variability being the largest error source for short-term variations in amplitudes and waveforms of the chest lead ECGs. To avoid presumed attenuation of ECG amplitudes by abundant breast tissue, anterolateral chest electrodes in women are often placed under the breasts and too low. There is also considerable uncertainty about locating the midclavicular line and the V4 electrode, particularly in obese persons and in women. We examined the effect of breast tissue protuberance on ECG amplitudes using ECG and anthropometric data on 6,814 women included in the Atherosclerosis Research in Communities Study (ARIC). The R wave amplitudes in anterolateral chest leads and the Sokolow-Lyon voltage decreased (P < .001 for all), and RaVL and the Cornell voltage increased significantly with increasing breast protuberance (P < .001 for all). However, these effects were small (15 microV or less for each 1-cm increment in breast protuberance), and R2 values were less than .01, indicating that breast protuberance alone explained less than 1% of ECG amplitude variations. When chest size and breast protuberance estimates were entered simultaneously into a multivariate regression model, chest size appeared to dominate, and model R2 values increased for positive associations with RaVL (R2 = .12) and the Cornell voltage (R2 = .04). Combined model R2 values remained < or =.01 for all other ECG amplitudes. A detailed step-by-step standardized electrode placement procedure was formulated. Because of the difficulties encountered in locating the left midclavicular line by visual inspection, we introduced well-defined procedures for identification and documentation of lateral chest electrode placement locations as a quality control method for clinical trials. Population data from the Third National Health and Nutrition Survey on the distributions by sex and race of chest electrode V4 and V6 locations and anthropometric data on chest size and shape are presented in order to facilitate evaluation of the comparability of electrode placement procedures in various studies and for quality control in clinical trials. It is concluded that standardized procedures to document chest electrode placement locations are feasible. Breast tissue appears to have a practically negligible effect on ECG amplitudes, and in women, the placement of chest electrodes on the breast rather than under the breast is recommended in order to facilitate the precision of electrode placement at the correct horizontal level and at the correct lateral positions.

Aged↗
PubMed1993

Assessing the diagnostic value of an ECG containing leads V4R, V8, and V9: the 15-lead ECG.

STUDY OBJECTIVES: To assess sensitivity, specificity, and odds ratios of ECG findings on leads V4R, V8, and V9 for acute myocardial infarction. DESIGN: Prospective, two-stage cohort study. SETTING: A 660-bed university-affiliated community hospital. TYPE OF PARTICIPANTS: One hundred forty-nine admitted patients with suspected myocardial infarction or unstable angina. INTERVENTIONS: Standard 12-lead ECG followed immediately by V4R, V8, and V9. MEASUREMENTS: Initial ECG findings of ST-segment displacement, Q waves, T-wave inversion, and eligibility for thrombolytic therapy. RESULTS: Major abnormalities (ST-segment deviation, T-wave inversion, Q waves) were found on the extra three leads in 28.9% (43 of 149) of patients. Sensitivity of ST-segment elevation for acute myocardial infarction on 12 versus 15 leads increased from 47.1% to 58.8%, respectively, with no decrease in specificity. McNemar's pair-matched analysis for ST-segment elevation on myocardial infarction subgroup showed an association of ST elevation with the 15-lead ECG (P < .05). An eightfold increase in the odds of detecting ST elevation was found (90% confidence interval, 1.42 to 14.58); 22% of patients negative for ST elevation on 12 leads were positive on 15 leads. Analysis of ECG criteria for thrombolytic therapy presenting uniquely on extra leads showed an increased sensitivity from 35.3% to 44.1% on 12 versus 15 leads, respectively; there was a sixfold increase in the odds of meeting ECG thrombolytic therapy criteria (90% confidence interval, 0.34 to 11.66); 13.5% of patients not meeting criteria on 12 leads did so on 15 leads. CONCLUSION: The 15-lead ECG provides increased sensitivity and odds of detecting ST-segment elevation in acute myocardial infarction patients with no loss of specificity; its use may expand the selection of thrombolytic therapy candidates and provide a fuller ECG description of the extent of myocardial injury and necrosis.

Aged↗
PubMed1999

ST-segment monitoring with continuous 12-lead ECG improves early risk stratification in patients with chest pain and ECG nondiagnostic of acute myocardial infarction.

OBJECTIVES: The purpose of this study was to evaluate the prognostic importance of ischemic episodes detected by ST-segment monitoring with continuous 12-lead electrocardiography (ECG) in a nonselected coronary care unit (CCU) population with chest pain and ECG nondiagnostic of acute myocardial infarction (AMI). BACKGROUND: Patients with chest pain and ECG nondiagnostic of AMI constitute a heterogeneous group concerning both diagnosis and prognosis. Continuous 12-lead ECG is a rather new method not thoroughly studied in this population. METHODS: The ST-segment monitoring with continuous 12-lead ECG was performed for 12 h in 630 consecutive patients admitted to CCU due to chest pain and a nondiagnostic ECG, i.e., no ST-segment elevations. An ST-episode was defined as a transient ST-segment depression or elevation of at least 0.10 mV. The median follow-up time was six months. RESULTS: A total of 176 ST-episodes occurred in 100 (15.9%) patients. The median duration and maximal ST-segment deviation in patients with ST-episodes were 80 min and 0.20 mV, respectively. Presence of ST-episodes predicted worse outcome concerning cardiac death and cardiac death or myocardial infarction (MI) (log-rank p < 0.001). At 30 day follow-up procedure, 10% versus 1.5% died from cardiac causes or had an MI in the group with and without ST-episodes, respectively. In a multivariate analysis, only troponin T > or = 0.10 microg/l and the presence of ST-episodes came out as independent predictors of cardiac death or MI. CONCLUSIONS: Continuous 12-lead ECG monitoring provides prognostic information on-line and considerably improves early risk stratification in patients with ECG nondiagnostic of AMI and symptoms suggestive of acute coronary syndrome.

Aged↗
PubMed1988

Problems and limitations of ECG baseline estimation and removal using a cubic spline technique during exercise ECG testing: recommendations for proper implementation.

One common variety of exercise-induced artifact is baseline wander resulting from movement, respiration, and poor electrode contact. Although filters can be designed to remove much of this baseline variation, they will distort the low-frequency components of the ECG complex, such as the TP-segment, the PR-segment, and, most problematically, the ST-segment. The ST-segment is the most diagnostically relevant measure of the ECG taken during exercise. While linear baseline interpolation and removal may be adequate at lower heart rates, they also will introduce significant distortions. This is particularly evident when excessive nonlinear wander is present, as seen at higher heart rates and respiration rates. A nonlinear, third-order, polynomial estimator of baseline wander, known as the cubic spline, has been used for nearly 15 years. It is a very robust technique applied to exercise ECG recordings. Since the cubic spline is not a filter and use an a priori knowledge of the shape of the ECG signal, it estimates the true baseline and avoids distortion better. The more common implementations of this technique use relatively short ECG recordings. With the advent of increasing power in computerized ECG systems, the implementation of the cubic spline algorithm for removing baseline wander in continuous, longer-duration ECG records and in real-time processing is being attempted. However, the correct application of the cubic spline to continuous recordings is not straightforward and involves a number of previously unforeseen difficulties. The accuracy and resolution of both floating point and integer operations is critical during long-term application of the cubic spline function.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1977

High fidelity ECG in the diagnosis of occult coronary artery disease: a study of patients with normal conventional ECG.

High fidelity (HF) electrocardiography (ECGY) was performed on four groups of patients with a normal resting electrocardiogram (ECG). Two groups (A and B) consisted of normal subjects over or under the age of 40, while the other two groups of patients (C and D) underwent coronary arteriography because of chest pain. HR ECG components within the initial portion of the QRS complex were significantly more common among patients with advanced coronary disease. The difference between the normal groups and the group with documented coronary artery disease (CAD) became more significant when the number of leads showing the HF ECG components was counted. Precordial leads were more sensitive in predicting the presence or absence of CAD than limb leads. HF ECG components in the terminal portion of the QRS complex did not differentiate between normals and patients with coronary artery disease, unless the number of leads showing these HF ECG components was considered. It seems that abnormal HF ECG components can point to minor areas of fibrosis caused by coronary artery disease even if the resting conventional ECG is normal.

Adult↗
PubMed1996

Influence of ECG measurement accuracy on ECG diagnostic statements.

Computer analysis of electrocardiograms (ECGs) provides a large amount of ECG measurement data, which may be used for diagnostic classification and storage in ECG databases. Until now, neither error limits for ECG measurements have been specified nor has their influence on diagnostic statements been systematically investigated. An analytical method is presented to estimate the influence of measurement errors on the accuracy of diagnostic ECG statements. Systematic (offset) errors will usually result in an increase of false positive or false negative statements since they cause a shift of the working point on the receiver operating characteristics curve. Measurement error dispersion broadens the distribution function of discriminative measurement parameters and, therefore, usually increases the overlap between discriminative parameters. This results in a flattening of the receiver operating characteristics curve and an increase of false positive and false negative classifications. The method developed has been applied to ECG conduction defect diagnoses by using the proposed International Electrotechnical Commission's interval measurement tolerance limits. These limits appear too large because more than 30% of false positive atrial conduction defect statements and 10-18% of false intraventricular conduction defect statements could be expected due to tolerated measurement errors. To assure long-term usability of ECG measurement databases, it is recommended that systems provide its error tolerance limits obtained on a defined test set.

Arrhythmias, Cardiac↗
PubMed1992

Accuracy of 22-lead ECG analysis for diagnosis of acute myocardial infarction and coronary artery disease in the emergency department: a comparison with 12-lead ECG.

STUDY OBJECTIVES: To compare a new 22-lead ECG with the 12-lead ECG for diagnosis of acute myocardial infarction (AMI). DESIGN: Prospective study of all consenting patients presenting to the emergency department with chest pain. SETTING: Urban hospital ED. TYPE OF PARTICIPANTS: 163 patients admitted with a cardiac-related diagnosis and complete data sets of 22- and 12-lead ECG results and creatine kinase-MB analysis. INTERVENTIONS: Patient care and existing protocols were unaltered, with the exception of including the new 22-lead ECG. MEASUREMENTS AND MAIN RESULTS: Forty-one of 163 patients had an AMI as defined by creatine kinase-MB analysis. The 22-lead ECG provided a statistically significant improvement in sensitivity (83%) for AMI diagnosis over the 12-lead ECG (51%) with specificities of 76% and 99%, respectively. CONCLUSION: When combined with clinical judgment, the 22-lead ECG could provide a 97.6% sensitivity for AMI diagnosis while reducing unnecessary admissions for "rule-out MI" by 69%.

Adult↗
PubMed2002

Dose reduction in multi-slice CT of the heart by use of ECG-controlled tube current modulation ("ECG pulsing"): phantom measurements.

PURPOSE: To evaluate the effect of ECG-controlled tube current modulation on radiation exposure in retrospectively-ECG-gated multislice CT (MSCT) of the heart. MATERIAL AND METHODS: Three different cardiac MSCT protocols with different slice collimation (4 x 1, and 4 x 2.5mm), and a pitch-factor of 1.5 and 1.8 were investigated at a multi-slice CT scanner Somatom Volume Zoom, Siemens. An anthropomorphic Alderson-Rando phantom was equipped with LiF-thermoluminescence dosimeters at several organ sites, and effective doses were calculated using ICRP-weighting factors. Scan protocols were performed with ECG-controlled tube current modulation ("ECG pulsing") at two different heart rates (60 and 80 bpm). These data were compared to previous data from MSCT of the heart without use of "ECG pulsing". RESULTS: Radiation exposure with (60 bpm) and without tube current modulation using a 2.5 mm collimation was 1.8 mSv and 2.9 mSv for females, and 1.5 mSv and 2.4 mSv for males, respectively. For protocols using a 1 mm collimation with a pitch-factor of 1.5 (1.8), radiation exposure with and without tube current modulation was 5.6 (6.3) mSv and 9.5 (11.2) mSv for females, and 4.6 (5.2) mSv and 7.7 (9.2) mSv for males, respectively. At higher heart rates (80 bpm) radiation exposure is increased from 1.5 - 1.8 mSv to 1.8 - 2.1 mSv, using the 2.5 mm collimation, and from 4.6 - 5.6 mSv to 5.9 - 7.2 mSv, for protocols using 1 mm collimation. CONCLUSIONS: The ECG-controlled tube current modulation allows a dose reduction of 37 % to 44 % when retrospectively ECG-gated MSCT of the heart is performed. The tube current - as a function over time - and therefore the radiation exposure is dependent on the heart rate.

Coronary Angiography↗
PubMed1991

[The noninvasive diagnosis of coronary heart disease in women. The exercise ECG or ST-segment analysis in the long-term ECG?].

The diagnostic value of an exercise ECG in women with the clinical symptoms of stable angina is limited because of its low accuracy in demonstrating coronary heart disease. A study of ambulatory patients was undertaken, involving 143 men and 29 women (mean age 55 [37-70] years), to determine whether ST-segment analysis of the 24-hour ECG gives better results, the coronary arteriogram providing the standard of comparison. 24-hour monitoring and the exercise ECG gave similar diagnostic results (66% vs 67%) in the 143 men. But in the 29 women 24-hour monitoring was diagnostically superior to the exercise ECG (76% vs 45%; P less than 0.01), as a result of a significantly higher specificity (64% vs 29%; P less than 0.05) and a tendency towards higher sensitivity (87% vs 60%; P = 0.13). As expected, the accuracy of the exercise ECG was thus lower in women than in men (P less than 0.05). There were no significant gender-specific differences for accuracy of 24-hour monitoring (76% in women, 66% in men; P less than 0.15). These data indicate that in women ST-segment analysis of the 24-hour ECG is better than the exercise ECG for demonstrating coronary heart disease.

Angina Pectoris↗
PubMed1996

Difference in QT interval measurement on ambulatory ECG compared with standard ECG.

Measurement of the QT interval on standard ECG has diagnostic importance in the congenital long QT syndrome, in pharmacological therapy of arrhythmias, as well as in ischemic heart disease. It has been suggested that QT prolongation on ambulatory ECG (Holter) may have similar importance. To assess agreement between methods, QT interval measurement on standard ECG was compared to that on Holter. Simultaneously obtained ECG and Holter tracings (25 mm/s) of the same complexes in leads V1 and V5 were studied in 14 patients (age range 4-36 years). ECG pairs (n = 100, 49 V1 and 51 V5) were compared over a range of QT interval from 300-620 ms, as determined with the use of calipers by two observers blinded to pairing relationship. Correlation between methods was high for both observers (observer 1:r[V1] = 0.872, r[V5] = 0.973; observer 2: r[V1] = 0.972, r[V5] = 0.988), and interobserver variability was small (> 85% of measurements within 20 ms). As compared to ECG, Holter underestimated QT interval in V1, mean difference (QT [Holter]-QT [ECG]) observer 1 (-23 ms, P < 0.001), observer 2 (-7 ms, P < 0.05), and overestimated QT in V5, mean difference observer 1 (+13 ms, P < 0.001), observer 2 (+ 13 ms, P < 0.001). However, individual variation between methods was wide, as expressed by the difference between individual measurements (95% confidence interval [V1]: observer 1 [-99 to +53 ms] observer 2 [-47 to +33 ms]; [V5]: observer 1 [-33 to +59 ms] observer 2 [-17 to +43 ms]). Furthermore, when using the QTA (interval from onset of Q wave to apex of T wave) similar variability was observed. In the assessment of QT interval, potential sources of error of this magnitude could limit the clinical utility of ambulatory monitoring in detecting prolongation of the QT interval for diagnostic purposes.

Adolescent↗
PubMed1976

[Value of long-term ECG monitoring in the diagnosis of coronary disease--comparison of 8-hour ECG monitoring and double Master exercise test with a clinical coronary index].

The use of the long term Ecg (dynamic Ecg) in the diagnosis of coronary artery disease (CAD) has been investigated in 83 patients and its sensitivity compared with the double Master two step test. The average ECG registration time was 8 hours. The presence of CAD was assumed when the clinical index according to Cohn et al. revealed a pathological value. If a horizontal or downsloping ST-segment depression of greater than or equal to 0,5 mm was chosen for the diagnosis of CAD a sensitivity of 82% resp. 64% was found for the dynamic Ecg and the double Master two step test. The specificity of the dynamic Ecg however was with 77% slightly inferior compared with the Master-test. The superiority in sensitivity of the dynamic Ecg was also present when the diagnosis of CAD was based on a ST-segment depression of greater than or equal to 1,0 mm. We believe that the dynamic Ecg can provide besides arrhythmia detection valuable information in the diagnosis of CAD and careful interpretation of the ST-segment should therefore be undertaken. The number of false positive results in the diagnosis of CAD was not influenced by the women included in the study.

Adult↗
PubMed1989

[Clinical evaluation of Tl-201 ECG-gated myocardial SPECT--comparison with ECG-gated blood pool SPECT].

In order to evaluate the clinical usefulness of the Tl-201 ECG-gated myocardial single photon emission computed tomography (SPECT), we compared the wall motion and the grade of the Tl-201 uptake of the ECG-gated myocardial SPECT with the wall motion of the ECG-gated blood pool SPECT. Materials were 87 patients of 50 old myocardial infarctions (OMIs), 19 hypertrophic cardiomyopathies (HCMs), 2 dilated cardiomyopathies (DCMs) and 16 others. After intravenous injection of 111-185 MBq (3-5 mCi) of Tl-201 at rest, the projection data were acquired using a rotating gamma-camera through 180 degrees, from RAO 45 degrees in 24 directions, each of which consisted of 80-100 beats. For the reconstruction of ED, ES and non-gated images, R-R interval was divided into about 20 (18-22) fractions. In 348 regions of interest (anterior, septal, lateral and inferior wall) in 87 cases, wall motion and the Tl-201 uptake were evaluated to three grades (normal, hypokinesis and akinesis; normal, low and defect, respectively), which were compared with the wall motion of the ECG-gated blood pool SPECT. The wall motion and the grade of the Tl-201 uptake of the ECG-gated myocardial SPECT correlated well with the wall motion of the ECG-gated blood pool SPECT (96.6% and 87.9%, respectively). In conclusion, the ECG-gated myocardial SPECT can provide clear perfusion images and is a very useful diagnostic strategy to evaluate the regional wall motion and perfusion simultaneously.

Adolescent↗
PubMed1989

[ST-segment analysis in long-term ECG: amplitude and phase response of various systems in comparison with standard ECG and their effect on true original reproduction of ST segment depression].

Ambulatory ECG monitoring has been suggested as a method for the detection of transient myocardial ischemia. But it is still unclear how accurately ST-segment alterations can be detected with the different systems. Measurement of amplitude and phase response is a valid method to estimate the fidelity of reproduction of an ECG-signal. We investigated the direct-recording long-term ECG systems CardioData Mk4 with recorder PR3, CardioData Mk4 with Spacelabs recorder, DMI Eclipse with DMI Recorder, Reynolds Pathfinder II with Oxford replay PB2 and recorder MR-10 and Reynolds Pathfinder III with tracker in comparison to a standard ECG recorder Picker Schwarzer C6800. Amplitude vs frequency response curves were derived from input sinus waves ranging from 0.01 to 500 Hz. The phase response was measured with a phase-sensitive waveform at a frequency range from 0.05 to 10 Hz. To determine the distortion of the ST-segment on the actual ECG, we produced a standard PQRST-signal that was modified to provide flat ST-segment depressions from 0 to 0.5 mV at 0.05 mV increments. The low and high frequency cut-off of the amplitude response was found at 0.09 and 220 Hz with the standard ECG recorder. A phase shift of -30 degrees was detected at 0.07 Hz. ST-segment depressions of the test-ECG were reflected to the same extent. For the CardioData-System, both cassette recorders yielded lower and upper cut-off frequencies of 0.06 and 0.07, and 20 and 16 Hz, respectively. A phase shift of -30 degrees was found at 0.35 and 0.31 Hz, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1978

Influence of resting ECG abnormalities on the ECG response to maximal exercise in women suspected of coronary heart disease.

Coronary arteriographic data have been compared with the ECG response to a maximal exercise test in 53 women with typical or atypical complaints of angina pectoris (AP). All patients with factors known as influencing the repolarization at rest were eliminated and the cases were subdivided according to the presence of a normal (n=26) or abnormal (n=27) resting ECG. The sensitivity (88%) and specificity (81%) of the exertional ECG was not affected by the clinical history nor by the resting ECG data. False positive responses were frequent (32%), particularly among women with atypical AP (50%), but their prevalence was not influenced by the resting ECG data. We conclude that, even in the absence of drug therapy, non-specific resting ECG abnormalities do not influence the ECG response to exercise in women and that they cannot be considered as a factor contributing to the false positive responses: the latter appear to be related to the low prevalence of coronary artery disease in women.

Adult↗
PubMed1994

[Comparison of stress ECG and long-term ECG for detection of myocardial ischemia in patients with coronary heart disease].

Holter-monitoring and exercise-ECG can be employed for the detection of myocardial ischemia. Exercise-ECG is capable of detecting ischemias caused by physical activity. In contrast, Holter monitoring can detect episodes of myocardial ischemia independent of exertion, but possibly connected with other factors such as mental stress. In 60 patients (49 male, 11 female, mean age 55.1 years) with angiographically documented coronary artery disease (26 x 1-vessel, 21 x 2-vessel, 13 x 3-vessel diseases) exercise-ECG and ambulatory 24-h monitoring were performed (3-channel recordings, ST-segment analysis). The assessment of the exercise-ECG showed 31 out of 60 patients with pathological results. 34 patients had pathological ST-segment changes during Holter monitoring (56%). Since both methods detected different patients, a combination of these techniques is useful. The combination of Holter monitoring and exercise-ECG raised the sensitivity to 78% (47/60 patients). Different heart rates were found at the point of maximal ST-segment changes in exercise-ECG as compared to the episodes of ST-segment changes recorded by Holter monitoring. This finding clearly illustrates the fact that different pathophysiological mechanisms are causing myocardial ischemia in respective cases. Using the coronary arteriogram as standard, the sensitivity of the two methods was different. While both techniques could detect multi-vessel disease at a similar level, Holter monitoring was significantly more sensitive in detecting patients with single-vessel disease. Thus, exercise-ECG and Holter monitoring supplement each other in detecting myocardial ischemia. In the future, larger clinical trials will have to confirm these results.

Adult↗