Search

The European Society of Cardiology and American College of Cardiology established their initial Joint Consensus Conference in July 1999 to develop a new definition of Acute Myocardial Infarction. This action was deemed necessary because of the development of new sensitive biochemical markers of myocardial necroses: Troponins T and I. There were 5 working groups, including one in Electrocardiography. The Conference adopted a definition that required only a history of "ischemic symptoms" and "a typical rise and fall" of at least one of the biochemical markers. The ECG Working Group strongly advised that a term distinctive from "myocardial infarction" such as "myocardial necrosette" be adopted as the diagnosis for an acute coronary event during which the peak biochemical marker level is below that which occurs when serial evolutionary ECG changes are observed. A pilot substudy from the GUSTO IIa Clinical Trial has identified the low end of the "ECG Change Range" to be: >2x the upper limit of normal for CK-MB, > 11 x for Troponin T, and >6 x for Troponin I.

OBJECTIVE: This study tests the ability of high-frequency components of the depolarization phase (HF-QRS) vs conventional ST-elevation criteria to detect and quantify myocardial ischemia. METHODS: Twenty-one patients admitted for elective percutaneous coronary intervention were included. Quantification of the ischemia was made by myocardial scintigraphy. High-resolution electrocardiogram before and during percutaneous coronary intervention was recorded and signal averaged. The HF-QRS were determined within the frequency band 150 to 250 Hz. ST-segment deviation was measured in the standard frequency range (

Background It is of great clinical importance to exclude myocardial infarction in patients with suspected coronary artery disease who do not have stress-induced ischemia. The diagnostic use of myocardial perfusion single-photon emission computed tomography (SPECT) in this situation is sometimes complicated by attenuation artifacts that mimic myocardial infarction. Imaging in the prone position has been suggested as a method to overcome this problem. Methods In this study, 52 patients without known prior infarction and no stress-induced ischemia on SPECT imaging were examined in both supine and prone position. The results were compared with cardiac magnetic resonance imaging (CMR) with delayed-enhancement technique to confirm or exclude myocardial infarction. Results There were 63 defects in supine-position images, 37 of which disappeared in the prone position. None of the 37 defects were associated with myocardial infarction by CMR, indicating that all of them represented attenuation artifacts. Of the remaining 26 defects that did not disappear on prone imaging, myocardial infarction was confirmed by CMR in 2; the remaining 24 had no sign of ischemic infarction but 2 had other kinds of myocardial injuries. In 3 patients, SPECT failed to detect small scars identified by CMR. Conclusion Perfusion defects in the supine position that disappeared in the prone position were caused by attenuation, not myocardial infarction. Hence, imaging in the prone position can help to rule out ischemic heart disease for some patients admitted for SPECT with suspected but not documented ischemic heart disease. This would indicate a better prognosis and prevent unnecessary further investigations and treatment.

Background Resolution of ST-segment elevation in the electrocardiogram (ECG) is used as a reperfusion sign during thrombolytic therapy in acute myocardial infarction. Analysis of high-frequency QRS components (HF-QRS) might provide additional information. The study compares changes in HF-QRS (150-250 Hz) to ST-segment changes in the standard ECG during thrombolytic therapy. Methods Twelve patients receiving intravenous thrombolytic therapy were included. A continuous 12-lead ECG recording was acquired for 4 hours. Results After 1 hour of therapy, 3 patients showed ST-elevation resolution as well as an increase in HF-QRS. These changes in ST and HF-QRS occurred simultaneously. No other patient showed significant changes in ST or HF-QRS after 1 hour. After 2 and 4 hours, there was less concordance between the standard and high-frequency ECGs. Conclusions In patients with early ST-elevation resolution, the standard and high-frequency ECGs show similar results. Later changes are more disparate and may provide different clinical information.

The detection and assessment of cardiac chamber hypertrophy has long been an important objective of clinical electrocardiography. Its importance has increased in recent years with the recognition that hypertrophy can be reversed with therapy, and that by doing so, adverse clinical outcomes can be

A subset of 3 criteria from the complete Selvester scoring system has been proposed earlier for electrocardiographic screening of healed myocardial infarcts. This subset yielded 95% specificity and high sensitivity for single anterior and inferior infarcts. In the present study, an automated version of these criteria was applied to 1,344 electrocardiograms from normal subjects (473 normal subjects as determined by cardiac catheterization and 871 apparently normal subjects by history and physical examination), to 706 from subjects with single myocardial infarction, and to 131 from subjects with combined anterior and inferior myocardial infarcts. Of the single infarcts, 366 had inferior, 277 anterior and 63 posterolateral locations. Presence and location of infarcts were judged from left ventriculograms and coronary angiograms. Overall specificity was only 86%, whereas overall sensitivity for the infarct population was 77%. Specificity was lower in men than in women; it was also lower in older than in younger subjects. One of the screening criteria (R greater than or equal to 40 ms in V1) may possibly be eliminated to augment specificity; this can be done with only minor loss of sensitivity. Differences in wave form measurements between the manual and computer methods account for a large part of the deterioration of specificity in this study compared with previously published results. Computer application of the screening criteria requires altered criteria limits in comparison with those used in manual application. Probably sex- and age-dependent criteria limits should be used.

Commonly used electrocardiographic criteria have been developed and tested in studies based on visual measurements. Limits from these criteria are often found in computer interpretation programs. The purpose of the present study was to assess the difference between visually measured Q durations and those measured by computer. The measurements were made using 12-lead electrocardiograms from 351 normal subjects

BACKGROUND: Knowledge of the location and size of ischemic myocardium at risk for infarction could impact prehospital patient triage and reperfusion therapy. The 12-lead electrocardiogram (ECG) can roughly estimate ischemia size; however, individual precordial ECG leads are at different distances from the left ventricle (LV) and certain LV walls have greater effects on the ECG. Vectorcardiographic corrected orthogonal lead systems can display the magnitude and direction of the ST-segment "injury current" vector in 3-dimensional space. We assessed whether the vectorcardiographic ST-vector direction and magnitude derived from the ECG by the inverse-Dower method can estimate the location and size of ischemia. METHODS AND RESULTS: Thirty-two patients underwent elective coronary angioplasty with control and 5-minute balloon-occlusion ECG and sestamibi injection followed by single photon emission computed tomography (SPECT). The ST-vector direction derived from the inverse-Dower method was projected to an LV model with normal coronary artery anatomy. The graphical display of ST-vector location could discriminate among occlusions of the different coronaries. The ST-vector located ischemia within the SPECT defect in 75% (24/32) of all patients and 96% (24/25) of patients with ischemia in more than 12% of the LV. ST-vector magnitude had a Spearman correlation of r = 0.68 (P < .0001) with SPECT ischemia size. CONCLUSIONS: The 3-dimensional ST vector derived from the ECG can be graphically projected onto an LV model to localize ischemia, and ST-vector magnitude correlates with ischemia size. Further study is warranted to assess the ability of vectorcardiographic imaging to risk-stratify and provide decision-support for patients with acute myocardial infarction. (Less)

Background Knowledge of the size and location of ischemic myocardium during acute coronary occlusion could provide decision support before reperfusion therapy. Electrocardiogram (ECG) scores based on the number of leads and the sum of ST-segment elevation have been unreliable in quantifying ischemia. We aimed to develop a new method to graphically display ischemic myocardium from simulated ECGs (DIMS-ECG) associated with known ischemic regions. Methods Twenty-one patterns of ischemia based on normal coronary anatomy were programmed into the freely available program ECGSIM ( www.ecgsim.org ). Minor variations of these patterns and 5 levels of ischemia severity produced 45 455 ECGs; 1000 normal ECGs were also added. Given a de novo ECG (an ECG from a patient), ST-segment and T-wave measurements are compared with ECG measurements in the database. The closest 200 matches are selected, and the corresponding ischemic areas are “averaged” to create a graphical display of the ischemic myocardium. Results Three patients are presented who underwent elective coronary angioplasty with continuous ECG recording and scintigraphically defined ischemic myocardium. Based on ECG analysis, the program graphically displays the ischemic myocardium with close agreement to the scintigraphic images. The program's source code and the ECG database will be made freely available. Conclusions The DIMS-ECG method graphically displays ischemic myocardium from information contained in the 12-lead ECG based on a novel approach to use a large simulated database instead of rule- or score-based method. After further development and testing, the DIMS-ECG method could be used to risk stratify patients with acute myocardial infarction.

Background The size of myocardial infarction (MI) is of significance for the prognosis. Selvester scores might be valuable for this estimation. Objective To compare the differences in Selvester scores for chronic MI provided from standard and EASI-derived 12-lead electrocardiograms (ECGs) and to compare these scores to the MI size measured by delayed-enhancement magnetic resonance imaging (DE-MRI). Methods Thirty-seven patients were studied. In connection with their DE-MRI scan follow-up after chest pain, body surface potential mapping was performed. Standard and EASI 12-lead ECGs were constructed from the maps. Two investigators manually performed the measurements required for scoring with the Selvester system using a quad-plot format of the ECGs. One of the investigators repeated this once for the standard leads. Results The differences between the 2 ECG estimations of MRI-measured MI size were not statistically significant. Neither the association nor the agreement between MRI and EASI-lead measurements or between MRI and standard-lead measurements were very strong. Conclusions The differences between ECG and MRI measurements of MI size indicate that both methods may need improvement.

There is currently a challenge to produce an electrocardiogram (ECG) recording of waveforms that are "standard" and also achieve the "noise immunity" required for continuous monitoring. The potential solutions that have been considered are to label each torso-recorded ECG as "nonstandard, torso-recorded," designate torso placement as "standard," or to reconstruct the "equivalent distally recorded ECG." The purpose of the present study was to validate an alternative "Lund system" of proximal limb electrode sites as a clinically feasible solution to this challenge. Data were collected from 75 patients referred for exercise testing at the Lund University Hospital. The Lund system produced Q wave dimensions and frontal plane QRS axis measurements that were in much better agreement with the standard ECG than those variables recorded with the Mason-Likar torso limb electrode method. Indeed, the Lund system replicated distal waveforms at a clinically acceptable level. Studies of larger patient cohorts including patients with various cardiac pathologies and studies of the noise immunity attained should be performed, and the acceptability by health care professionals should be determined.

For a 12-lead resting electrocardiogram (ECG) to be considered "standard," limb electrodes should be placed distally on the limbs. When resting ECGs are taken in conjunction with an ECG-monitoring situation, so-called monitoring sites (as described by Mason and Likar and also others) on the torso are used. Numerous publication have indicated that these ECGs are not identical with those recorded from distal sites, and this prohibits application of visual or computer-based interpretation criteria as well as serial comparison with standard ECGs. Loss of Q waves diagnostic for inferior wall myocardial infarction, as well as marked differences in frontal plane electrical axis, is the most commonly encountered problem with torso-recorded ECGs. This overview suggests 4 possible solutions to this dilemma.

The purpose of this study is to assess QT interval measurements from the EASI 12-lead ECG as compared to the standard 12-lead ECG. The QT interval was automatically measured in simultaneously recorded standard and EASI 12-lead ECGs, using a validated wavelet-based delineator. The agreement between the two sets of measurements was quantified both on a lead-by-lead basis and a multilead basis. The results show an acceptable agreement between QT measurements in the two lead systems, with correlation coefficients (CC) 0.91-0.98 depending on the lead. Standard deviations range from 9.2 ms to 26.4 ms depending on the selected lead. In a few patients large inter-system differences were found, mainly due to different T wave morphologies. Using a multilead delineation, QT intervals were considerably more stable than single-lead measurements and resulted in a much better agreement between the two lead systems (CC: 0.98, QT difference: 1.1 ms +/- 9.8 ms). Thus, EASI-derived 12-lead ECG may be used for reliable QT monitoring when the multilead delineation approach is adopted.

Magnetic resonance imaging (MRI) has emerged in the last decade as an important method for characterizing various aspects of cardiac anatomy, patho-anatomy, pathophysiology, and function. Measurements of flow parameters, left ventricular function, and grade of valvular regurgitation have been validated and proved to serve as excellent gold standards compared to simpler, established techniques, such as echocardiography, thermodilution measurements, and electrocardiography [1].

This statement provides a concise list of diagnostic terms for ECG interpretation that can be shared by students, teachers, and readers of electrocardiography. This effort was motivated by the existence of multiple automated diagnostic code sets containing imprecise and overlapping terms. An intended outcome of this statement list is greater uniformity of ECG diagnosis and a resultant improvement in patient care. The lexicon includes primary diagnostic statements, secondary diagnostic statements, modifiers, and statements for the comparison of ECGs. This diagnostic lexicon should be reviewed and updated periodically.

This statement examines the relation of the resting ECG to its technology. Its purpose is to foster understanding of how the modern ECG is derived and displayed and to establish standards that will improve the accuracy and usefulness of the ECG in practice. Derivation of representative waveforms and measurements based on global intervals are described. Special emphasis is placed on digital signal acquisition and computer-based signal processing, which provide automated measurements that lead to computer-generated diagnostic statements. Lead placement, recording methods, and waveform presentation are reviewed. Throughout the statement, recommendations for ECG standards are placed in context of the clinical implications of evolving ECG technology.

This statement examines the relation of the resting ECG to its technology. Its purpose is to foster understanding of how the modern ECG is derived and displayed and to establish standards that will improve the accuracy and usefulness of the ECG in practice. Derivation of representative waveforms and measurements based on global intervals are described. Special emphasis is placed on digital signal acquisition and computer-based signal processing, which provide automated measurements that lead to computer-generated diagnostic statements. Lead placement, recording methods, and waveform presentation are reviewed. Throughout the statement, recommendations for ECG standards are placed in context of the clinical implications of evolving ECG technology.

Background: The electrocardiographic (ECG) diagnosis of acute myocardial infarction (MI) should be improved. This might be done either by regarding all 24 aspects (both positive and negative leads), or a subset hereof (e.g. 19-lead ECG), of the conventional 12-lead ECG or by using additional electrodes. The purpose of this study was to investigate the accuracy of the different ECG methods in diagnosing acute ST-elevation MI. Methods: The study population consisted of 479 patients admitted to Lund University Hospital with acute chest pain. One conventional ECG plus leads V4R, V5R, V8 and V9 were recorded for each patient within 24 h of admittance. Biochemical markers were used as the 'gold standard' for diagnosis of MI. We measured ST-segment elevations in the 12-, 16- and 24-lead postadmission ECGs as well as in the 12-, 19- and 24-lead admission ECGs. Results: The sensitivity for detecting acute MI was 28% for the postadmission 12-lead ECG, 33% for the 16-lead ECG and 37% for the 24-lead ECG. The specificities were 97%, 93% and 95%, respectively. For admission ECGs, the sensitivity was 33% for the 12-lead ECG, 45% for the 19-lead ECG and 49% for the 24-lead ECG, with specificities of 97%, 96% and 94%, respectively. Conclusion: The sensitivity for detecting acute MI was higher for the 16-, 19- and 24-lead ECGs than for the conventional 12-lead ECGs. Their specificity, however, was slightly lower. If increased sensitivity for detecting MI is desired, the 24-lead or 19-lead should be used as no additional electrodes are required.

Background: A previous study has shown that analysis of high-frequency QRS components (HF-QRS) is highly sensitive and reasonably specific for detecting reversible perfusion defects on myocardial perfusion imaging (MPI) scans during adenosine. The purpose of the present study was to try to reproduce those findings. Methods: 12-lead high-resolution electrocardiogram recordings were obtained from 100 patients before (baseline) and during adenosine Tc-99m-tetrofosmin MPI tests. HF-QRS were analyzed regarding morphology and changes in root mean square (RMS) voltages from before the adenosine infusion to peak infusion. Results: The best area under the curve (AUC) was found in supine patients (AUC=0.736) in a combination of morphology and RMS changes. None of the measurements, however, were statistically better than tossing a coin (AUC=0.5). Conclusion: Analysis of HF-QRS was not significantly better than tossing a coin for determining reversible perfusion defects on MPI scans.

Objectives: This study investigates whether sequential addition of inverted, (negative) leads from the 24-lead electrocardiogram (ECG) to the orderly sequenced 12-lead ECG would identify a number of leads with which the sensitivity for diagnosis of acute transmural ischemia is significantly increased with minimal loss of specificity. Background: Acute transmural ischemia due to thrombotic coronary occlusion typically progresses to infarction. Its recognition is based on currently accepted ST-elevation myocardial infarction (STEMI) criteria with suboptimal sensitivity, which could be potentially increased by consideration of the principle that each of the 12 ECG leads can be inverted to provide an additional lead with the opposite (180 degrees) orientation, generating a 24-lead ECG. Methods: The study population included 162 patients who underwent prolonged coronary occlusion during elective percutaneoas transluminal coronary angioplasty. Balloon occlusion was performed in the left anterior descending coronary artery (51 patients), in the right coronary artery (67 patients), or in the left circumflex coronary artery (44 patients). To be classified as indicative of the epicardial injury current of acute ischemia, the ECGs had to fulfill either the criteria of a consensus document from the American College of Cardiology or the European Society of Cardiology or thresholds for the inverted leads based on a population study from Scotland. Results: The addition of -V1, -V2, -V3, -aVL, -I, aVR, and -III increased sensitivity from 61% to 78% (P

The number of leads needed in clinical electrocardiography depends on the clinical problem to be solved. The standard 12-lead ECG is so well established that alternative lead systems must prove their advantage through well-conducted clinical studies to achieve clinical acceptance. Certain additional leads seem to add valuable information in specific patient groups. The use of a large number of leads (eg, in body surface potential mapping) may add clinically relevant information, but it is cumbersome and its clinical advantage is yet to be proven. Reduced lead sets emulate the 12-lead ECG reasonably well and are especially advantageous in emergency situations.

The purpose of the present study is to assess QT-interval measurements from the EASI 12-lead electrocardiogram (ECG) as compared with the standard 12-lead ECG. The QT interval was automatically determined in simultaneously recorded standard and EASI 12-lead ECGs, using a validated wavelet-based delineator. The agreement between the 2 sets of measurements was quantified both on a lead-by-lead basis and a multilead basis with global definitions of QRS onset and T-wave end. The results show that the agreement between QT-interval measurements from the 2 lead systems is acceptable, with negligible mean differences and with correlation coefficients ranging from 0.91 to 0.98 depending on the lead studied. Although the SD shows a clear dependence on the selected lead (ranging from 9.2 to 26.4 milliseconds), differences are within the accepted tolerances for automatic delineation. In a few patients, large differences were found, mainly because of changes in morphology present in both lead systems. QT intervals measured by the multilead approach were considerably more stable than single-lead measurements and resulted in a much better agreement between the 2 lead systems (correlation coefficient, 0.98; QT difference, 1.1 +/- 9.8 milliseconds). Thus, the EASI 12-lead ECG may be used for reliable QT monitoring when the multilead delineation approach is adopted. (c) 2007 Elsevier Inc. All rights reserved. (Less)

In patients with myocytolysis detected in endomyocardial biopsy, there is a tendency towards a shift of ventricular electrical axes from normal to strain pattern on surface ECG. Their 12-lead signal-averaged electrocardiogram (SAECG) show a significant increase in filtered QRS duration (QRSD) compared with those with specimens without myocytolysis. Late potentials were generally found more frequently in individual SAECG leads than in the vector magnitude. An increase in filtered QRSD and the presence of late potentials compared with a baseline study emphasizes the need for endomyocardial biopsy. Consequently, no change in these parameters may preclude the indication for endomyocardial biopsy.

Background: The mechanisms underlying high-frequency QRS components (HF-QRS) are incompletely understood. One theory is that HF-QRS are related to the conduction velocity of the heart. The purpose was to test this hypothesis by comparing HF-QRS in patients with left or right bundle branch block (LBBB and RBBB, respectively) to those in healthy subjects and in patients with ischemic heart disease (IHD). Methods: Twenty-two patients with LBBB, 19 patients with RBBB, 63 normal subjects, and 64 patients with IHD were included. Twelve-lead electrocardiograms were analyzed in the frequency interval 150 to 250 Hz. Results: The study showed reduced HF-QRS in patients with LBBB compared with healthy subjects and patients with IHD. The difference, however, was small in lead V-1 and V-2. In patients with RBBB, no differences in HF-QRS could be detected except in few leads; among those is lead V-1. Conclusion: The results support the theory that HF-QRS are related to the conduction velocity of the heart. (c) 2007 Elsevier Inc. All rights reserved. (Less)

ST-segment measurements in the standard 12-lead electrocardiogram (ECG) of patients with acute coronary syndromes are crucial for these patients' management. Our objective was to determine whether the 12-lead ECG derived from the 3-lead EASI system can attain a level of diagnostic performance similar to that of the Mason-Likar (ML) 12-lead ECG acquired in clinical practice (CP) by paramedics and emergency department technicians. Using 120-lead body surface potential maps recorded before and during balloon inflation angioplasty from 88 patients (divided into "responders" and "nonresponders"), and electrode placement data from 60 applications of precordial leads in CP, we generated for the "nonischemic" and "ischemic' states of each patient the following lead sets: the ML 12-lead ECG, the EASI-derived 12-lead ECG, and 60 sets of 12-lead CP ECGs. We extracted ST deviations at J + 60 milliseconds, summed them for all 12 leads of each lead set to obtain Sigma ST, and, by using the bootstrap method, determined the mean sensitivity and specificity for recognizing the "ischemic' state at various thresholds of Sigma ST. Results were displayed as receiver operating characteristics, and the area under these curves (AUC) +/- SE was used as the measure of diagnostic performance. AUC SE for all patients were ML ECG, 0.66 +/- 0.03; EASI ECG, 0.64 +/- 0.03; and CP ECG, 0.67 +/- 0.03. Corresponding results for responders only were 0.81 +/- 0.04 for ML ECG, 0.78 +/- 0.04 for EASI ECG, and 0.81 +/- 0.04 for CP ECG. The differences between the AUCs for the different lead sets were not significant (P >.05). Thus, the EASI-derived 12-lead ECG is as good for detecting acute ischemia as is the 12-lead ECG acquired in CP. (c) 2007 Elsevier Inc. All rights reserved. (Less)

In this work U method is presented for robust estimation of the respiratory frequency from exercise ECG. The method is based on the rotation angles of the heart's electrical axis as induced by respiration, determined by aligning successive QRS loops to a reference loop using a least squares criterion. The respirarory frequency is estimated by power specfral analysis of the estimated rotation angle series. Special attention has been paid to handling highly non-stationary and noisy exercise ECGs. The ECG and respiratory signals of 14 volunteers and 20 patients were simultaneously recoded during stress resting to evaluate the method. The respiratmy frequency was estimated from exercise ECGs and compared to the frequency obtained from respiratory signals. An error of 6.1% ± f3.7% (0.024±0.017Hz, mean±sd) is achieved, suggesting that the method is useful for analysis of exercise ECGs.

The Anderson-Wilkins (AW) electrocardiographic (ECG) acuteness score complements time from pain onset in prognostic stratification of patients with acute myocardial infarction (AMI). However, for the AW acuteness score to be of practical use in the acute situation, it must be an integral component of a commercial automated ECG analysis program. The objective of this study was to determine the concordance between human and computer measurements and calculation of the AW acuteness score. The mean difference in AW acuteness score was 0.11 +/- 0.66 for anterior and -0.07 +/- 1.24 for inferior AMI. Ninety-nine percent of the differences were found to be 1.0 or less for the anterior AMI group, and 91.7% were 1.0 or less in the inferior AMI group. The differences were primarily caused by minor disagreements in measurements. In conclusion, the AW acuteness score established using manual ECG waveform measurements can be implemented into commercial automated ECG analysis programs to achieve practical use in clinical decision support for patients with AMI.

Summary Background: Electrocardiogram-gated myocardial single-photon emission computed tomography (SPECT) with 99mTc-tetrofosmin allows simultaneous evaluation of myocardial perfusion and function. In this study, left ventricular volumes, ejection fraction (LVEF), and left ventricular wall volume (LVWV) derived from gated SPECT were compared with measurements from cardiovascular magnetic resonance (CMR), performed within a few hours. Methods: The study population included 55 patients with known or suspected coronary artery disease, including 13 patients with recent acute myocardial infarction. End-diastolic (EDV) and end-systolic (ESV) volumes, LVEF and LVWV were derived automatically from gated SPECT using commercially available software (QGS). In the CMR studies, manually delineated endocardial and epicardial borders on short-axis slices were used to calculate the volumes. Results: Gated SPECT underestimated EDV by 35 ± 14 ml (mean ± SD) (P

The ability to estimate left ventricular mass (LVM) from the standard 12-lead electrocardiogram (ECG) has been shown to be limited because there is a considerable variability of the normal 12-lead ECG due to demographic and anthropometric variables. We sought to study LVM in healthy subjects and its relationship with QRS duration, and established electrocardiographic criteria for left ventricular hypertrophy. Cardiac magnetic resonance imaging was used to measure LVM. Seventy-one healthy volunteers (36 men; age range, 21-82 years) were studied. All ECG criteria tested showed a statistically significant relationship with LVM. The highest R value was found between LVM and QRS duration, as well as the 12-lead voltage-duration product (R = 0.59, P < .001 for both). The lowest R value was found for the Sokolow-Lyon voltage criterion (R = 0.25, P = .033). Left ventricular mass differed significantly between sexes, as did all ECG criteria except the Sokolow-Lyon criterion. Thus, in healthy subjects, QRS duration alone is equally or more strongly correlated to LVM than are established electrocardiographic left ventricular hypertrophy criteria.

ST elevation myocardial infarction (STEMI) in the right ventricle (RV) associated with right coronary artery (RCA) occlusion is known to have high hospital mortality. The hypothesis tested in this study is: right precordial leads V4R and V5R help detect STEMI in the right ventricle. ECGs from 1,970 subjects were collected in Ruijin Hospital (n=1,342), Shanghai, China and Lund University Hospital, Lund (n=565), Sweden. All ECGs were recorded with additional leads on the right precordial location in V4R and V5R. Our results show that the subjects with middle to upper RCA occlusion often show ST elevation in leads V4R and V5R and ST depression in lateral leads I, aVL, V5-V6, and are often undetected as STEMI or AMI in the standard 12-lead ECG. We conclude that adding V4R and V5R to standard ECG recording in assessing patients presenting with acute coronary syndrome is an easy and convenient way to increases the sensitivity of STEMI detection

The ability of the 12-lead electrocardiogram (ECG) to quantify size and transmural extent of myocardial infarction (MI) is not fully explored. Q waves are still thought of as indicative of transmural MI despite that several studies have rejected this association. We hypothesized that size and transmural extent of acute MI indeed can be estimated by QRS scoring on the 12-lead ECG using delayed, contrast-enhanced magnetic resonance imaging (DE-MRI) as gold standard and that Q waves are not predictive of transmural MI.Twenty-nine patients with first-time reperfused MI were studied. Delayed, contrast-enhanced magnetic resonance imaging was performed and 12-lead ECG was recorded 8 +/- 1 days after the acute event. Myocardial infarction size and transmurality were determined by DE-MRI and compared with Selvester QRS score from the ECG recorded on the same day.There was a good correlation (r = 0.79, P.001) between MI size by QRS scoring and DE-MRI. As local MI transmurality increased as assessed by DE-MRI, the local QRS score increased progressively (P.001). There was no significant difference in the number of Q-wave-related QRS points between nontransmural and transmural MI (1.8 +/- 0.6 vs 2.9 +/- 0.4, P = .14). The global QRS score, however, differed significantly (3.1 +/- 0.8 vs 5.1 +/- 0.6, P.05).QRS score is significantly related to both MI size and transmurality by DE-MRI in patients with first-time reperfused MI. Presence of Q waves, however, is not indicative of transmural MI in these patients. Thus, QRS scoring could potentially be used for diagnosing and characterizing MI in patients with suspected recent MI.

Background: It is possible that efforts in ECG review by both young experienced clinicians are currently discouraged—and risk to be completely dismissed—by the conventional (ie, disorderly) display of the frontal plane leads, with lead aVR at −150°. Methods: We reviewed studies on the usefulness of leads aVR and −aVR as well as on the history of the frontal leads in electrocardiography. Results: Lead aVR and particularly, lead −aVR, provide useful information when systematically analyzed. In addition, if lead −aVR is examined in its anatomically logical sequence, ie, aVL, I, −aVR, II, aVF, and III, the frontal plane of the 12-lead ECG is more easily understood. This “panoramic” or “orderly” display is in common use in countries such as Sweden, but it is rarely seen in the United States. Conclusions: ECG interpretation would be enhanced by displaying the limb leads in an orderly arrangement that starts with lead aVL and ends with lead III, and many ECG changes would be ideally displayed by a lead −aVR at 30°.

Introduction: Monitoring of serial 12-lead electrocardiogram (ECG) recordings is the accepted requirement for prehospital data acquisition in patients with chest pain. The purpose of this study was to determine whether waveforms and clinical triage decisions are similar for EASI-derived ECGs and paramedic-acquired 12-lead ECGs using Mason-Likar limb lead configuration when compared with standard 12-lead ECGs (stdECG). Method: Twenty patients with chest pain had a prehospital 12-lead ECG recorded in the ambulance, and paramedic-applied electrodes retained in place at hospital arrival. An ECG technician applied standard precordial and EASI electrodes in their Correct positions. Twelve-lead ECGs were obtained from the paramedic-applied electrodes using their Mason-Likar limb lead configuration, and derived from the EASI leads for comparison with the stdECG. Three computer-measured QRS-T waveform parameters were considered, and differences in waveform measurement between EASI and stdECG (EASI Delta stdECG) versus differences in waveform measurements between paramedic Mason-Likar and stdECG (PML Delta stdECG) were calculated. Two emergency physicians determined whether the EASI-derived or the paramedic Mason-Likar ECG contained information that would change their clinical triage decision from that indicated by the stdECG. Results: EASI Delta stdECG and PML Delta stdECG were identical in 28%, whereas EASI Delta stdECG was more than PML Delta stdECG in 35%, and PML Delta stdECG was accurate (both times) than EASI Delta stdECG in 37% (P = .62). The physicians were more likely to change the level of patient care based on the EASI-derived ECGs compared with the paramedic ECGs; however, this difference was not statistically significant (P = .27), but this may only be caused by the small study population. Conclusions: There are similar differences from stdECG waveforms in EASI-derived ECGs and those acquired via paramedic-applied precordial electrodes using Mason-Likar limb lead configuration. Either method can be used as a substitute for monitoring, but neither should be considered equivalent to the stdECG for diagnostic purposes. (c) 2006 Elsevier Inc. All rights reserved. (Less)

Myoelectric noise and baseline wander, artifacts that appear when patients move during electrocardiographic monitoring, can cause false alarms. This problem can be addressed by using a reduced lead set and placing electrodes on the anterior part of the torso only. The Mason-Likar modification of the standard 12-lead electrocardiogram and the EASI lead system are 2 alternative systems for lead placement.To test the hypothesis that the EASI lead system is less susceptible to artifacts than is the Mason-Likar modification of the standard 12-lead electrocardiogram.Baseline wander and myoelectric noise amplitudes of EASI and Mason-Likar 12-lead electrocardiograms were compared. Twenty healthy volunteers participated. Both lead systems were recorded simultaneously for different types of physical activities. For each lead in each subject, baseline wander and myoelectric noise were measured for both systems, at rest and during each physical activity.The outcome for baseline wander was mixed. For myoelectric noise content, the EASI system performed better for the limb leads in the different physical activities. In the precordial leads, the differences were minimal or mixed. However, for supine-to-right turning, EASI performed worse than the Mason-Likar system.The 2 systems have similar susceptibilities to baseline wander. The EASI system is, however, less susceptible to myoelectric noise than is the Mason-Likar system. EASI performed worse than Mason-Likar for turning supine to right, because only the EASI system uses an electrode in the right-midaxillary line.

Signal-averaged electrocardiograms (SAECGs) were recorded with bipolar orthogonal and standard 12-lead settings in 29 term healthy newborn infants. SAECGs performed with the two lead configurations were similar in quality and quantity. For the duration of the QRS complex (QRSD), the upper limit of normality for newborn infants can be set to 100 ms. It is similar in individual bipolar orthogonal and individual standard 12-lead recordings as well as in filtered QRSD in the vectorcardiograms (the vector magnitude, VM, and the sum of extremity leads). In individual leads of bipolar orthogonal and standard 12-lead recordings, root-mean-square voltage of the terminal 40 ms of the QRS complex (RMS40) is widely scattered and unsuitable as discriminant variable. For VM and the sum of the extremity leads, the same reference values for RMS40 and duration of low-amplitude signal can be used as applied in adults. Individual lead recordings provide complementary information in addition to vectorcardiograms. There are practical advantages using standard 12-lead compared to conventional bipolar orthogonal configurations. The widespread use of standard 12-lead ECG in routine medical practice makes its utility advantageous also in performing signal-averaged electrocardiography.

Optimal treatment of acute myocardial infarction (AMI) depends on the duration of the ischemia. The Anderson Wilkins (AW) electrocardiographic acuteness score has been shown to complement the historical timing in estimating the time interval from acute thrombotic coronary occlusion in patients presenting with chest pain and evolving myocardial infarction. The purposes of this study were to (1) compare the distributions of the previously developed AW acuteness score in a training population with either anterior or inferior AMI and (2) propose modifications to the formula to achieve distributions similar to the observed distributions of historical times from onset of pain.Two hundred three and 177 patients were included as training and testing population, respectively. All patients had an anterior or an inferior AMI and were without confounding factors on the electrocardiogram.The training population had similar distributions of historical times from onset of pain, but differences in distributions of AW acuteness scores, between patients with anterior and inferior AMI (P.0001). Eighty percent of the inferior AMI group had the highest possible AW acuteness score. Modification of a Q-wave criterion fromor =30 toor =20 ms resulted in similar distributions in patients with anterior and inferior AMI both in the training and an independent testing population.These results suggest that a modified AW acuteness score using a lower Q-wave duration criterion provides similar AMI timing information in patients with anterior and inferior locations. Clinical use of the AW acuteness score will only be practical if the calculation is automated.

Accurate precordial electrode placement can be difficult in emergency situations leading either to loss of time or diminished accuracy. A possible solution is the quasi-orthogonal EASI lead system, with only five electrodes and easily defined landmarks to provide a derived 12-lead electrocardiogram (ECG). The purpose of this study was to test the hypothesis that precordial waveforms in EASI-derived ECGs have no greater deviation from those in gold standard ECGs, than do the precordial waveforms in paramedic acquired standard ECGs. Twenty paramedics applied the standard precordial electrodes employing the routine procedure. A certified ECG technician applied the 6 standard precordial electrodes in their correct gold standard positions, and the EASI electrodes. 12-lead ECGs were obtained from the paramedics' standard leads, and derived from the EASI leads, for comparison with the gold standard ECG. In each precordial lead recording, 6 computer-measured QRS-T waveform parameters were considered. Differences between deltaEASI-gold standard versus deltaparamedic-gold standard were calculated for every waveform in every lead resulting in 720 comparisons. EASI and paramedic results were "equally accurate" in 47%, the paramedic was more accurate in 31%, and EASI was more accurate in the remaining 22%. The differences from gold standard recording of precordial waveforms in ECGs derived from the EASI leads and those acquired via paramedic-applied standard electrodes are similar. The results suggest that the EASI lead system may provide an alternative to the standard ECG precordial leads to facilitate data acquisition and possibly save valuable time in emergency situations.

A method for detecting body position changes that uses the surface vectorcardiogram (VCG) is presented. Such changes are often manifested as sudden shifts in the electrical axis of the heart and can erroneously be interpreted as acute ischaemic events. Axis shifts were detected by analysing the rotation angles obtained from the alignment of successive VCG loops to a reference loop. Following the rejection of angles originating from noise events, the detection of body position changes was performed on the angle series using a Bayesian approach. On a database of ECG recordings from normal subjects performing a predefined sequence of body position changes, a detection rate of 92% and a false alarm rate of 7% was achieved.

To investigate the possibility of simplifying electrocardiogram (ECG) recording in children, we compared waveforms in conventional 12-lead ECGs to those derived from EASI leads in 221 children of various ages. The conventional 12-lead ECGs and the ECGs using EASI electrode positions were collected simultaneously. We developed and determined the value of age-specific transformation coefficients for use in deriving 12-lead ECGs from the signals recorded at the EASI sites. We compared the results of using age-specific coefficients to the results of using adult coefficients and studied the "goodness-of-fit" between the conventional and the derived 12-lead ECGs. The age-specific coefficients performed slightly better than the adult coefficients, and good agreement was usually attained between the conventional 12-lead ECG and the EASI-derived 12-lead ECG. Our conclusion is that EASI leads in children have the same high levels of "goodness-of-fit" to replicate conventional 12-lead ECG waveforms, as reported earlier in adults.

The purpose of the present study was to examine the performance of a neural network in an electrocardiogram (ECG) classification task. ECGs recorded from 272 patients with anterior myocardial infarction and 479 subjects without myocardial infarction were studied. Fifteen QRS measurements of the leads V2-V4 were used as inputs to the network. The network was trained using 502 ECGs. Thereafter, a comparison of the network, conventional criteria and a human expert was performed using a test set of 249 ECGs. The neural network showed a higher sensitivity than the conventional criteria, both having a specificity of 97%. The performance of the human expert was the same as that of the neural network. It seems that neural networks could be used to improve the performance of some parts of ECG interpretation programs. >

Artificial neural networks are computer-based expert systems which have been used for several pattern recognition tasks, e.g. classification of electrocardiograms (ECG). Another method which has proved to be a valuable tool for improving the quality of ECG interpretation is the synthesized vectorcardiogram (VCG). These two methods were combined and applied on a material of 1458 ECGs recorded from subjects with or without inferior myocardial infarction (MI) evidences by ECG independent data. Neural networks fed with measurements from the ECG as well as the synthesized VCG showed after a learning process a sensitivity of 83% at a level of specificity of 97%. The result shows that planar ST-T measurements and QRS measurements from the synthesized VCG improved the performance compared to networks fed with scalar QRS measurements only. >

The measurement of subtle beat-to-beat morphologic variability is complicated by the presence of respiration-induced movements of the heart. A statistical signal model is developed which accounts for scaling, rotation and time synchronization of a VCG loop. The maximum likelihood (ML) estimator of the model parameters is derived and tested on a material of high-resolution VCG recordings. The results show that the new method, relying on a spatial relationship of the leads, is able to efficiently reduce the effects of respiration on beat-to-beat variability.

The aim was to study beat-to-beat QRS variability in resting 12-lead ECG in patients with ischemia and myocardial infarction. The variability analysis was based on a refined technique for time alignment of the beats and included means for compensating the influence of respiration. A group with normal myocardial scintigraphy (called NO) was compared to a group with signs of both myocardial infarction and exercise-induced ischemia (called ISCINF). The mean QRS variability was smaller in lead I in ISCINF than in NO but there was no significant difference in QRS variability in the other leads. The joint variance in all leads was calculated and ROC curves constructed. The sensitivity to detect coronary artery disease (CAD) was 75% at a specificity of 50%. It is concluded that QRS variability does not discriminate between presence and absence of CAD well enough to be of clinical value.

A method to synthesize the vectorcardiogram (VCG) from the 12-lead electrocardiogram (ECG) was earlier presented by L. Edenbrandt et al. (1988). The authors also presented an automated method for detection and quantification of bites, i.e. abnormalities in the configuration of the planar loops. The purpose of the present study is to combine and test these two methods in order to introduce the concept of vectorcardiographic bites in computerized analysis of the 12-lead ECG. Bite amplitudes were studied in 296 patients with diabetes mellitus using the method for synthesizing VCGs from 12-lead ECGs and automated bite analysis. The differences between bite amplitudes measured automatically and visually were less than 35 mu V in all but 3/149 cases. The differences in bite amplitude between Frank VCG and synthesized VCG were greater, but good agreement was seen in the majority of cases. >

Artificial neural networks (ANNs) have proved to be of value in pattern recognition tasks, e.g. classification of electrocardiograms (ECGs). Electrocardiographic lead reversals are often overlooked by ECG readers, and may cause incorrect ECG interpretation, misdiagnosis and subsequent lack of proper treatment. A database of 11000 ECGs from an emergency department, which had been purified from technically deficient ECGs as well as ECGs with lead reversals were used in the study. The same database was used to generate by computer two subsets of 11000 ECGs, one consistent with right arm/left foot lead reversal and one with left arm/left foot lead reversal. After training, the networks detected 57.6% of the ECGs with left arm/left foot lead reversal and 80.5% of the ECGs with right arm/left foot lead reversal. The specificities were 99.97% and 99.95% respectively. The results show that ANNs can be trained to detect ECG lead reversals at very high specificity.