Role of the 12-lead electrocardiogram in diagnosing pulmonary embolism

We investigated the role of the standard 12-lead electrocardiogram (ECG) to improve the pretest probability of pulmonary embolism before performing computed tomographic (CT) pulmonary angiography. A retrospective chart analysis was performed on patients who underwent CT pulmonary angiography at a tertiary care hospital during a 30-month period. Comparison of 15 ECG parameters was made between those with CT pulmonary angiograms positive for pulmonary embolism and a matched control group with negative CT pulmonary angiograms. Data were analyzed by chi-squared tests and logistic regression. Sinus tachycardia (39% vs. 24%, P <0.01), an S1 Q3 T3 pattern (12% vs. 3%, P <0.01), atrial tachyarrhythmias (15% vs. 4%, P <0.005), a Q wave in lead III (40% vs. 26%, P <0.02), and a Q3 T3 pattern (8% vs. 1%, P <0.02) were the findings significantly associated with pulmonary embolism. We conclude that 1) standard 12-lead ECG findings can increase the pretest probability of pulmonary embolism before performing CT pulmonary angiography; and that 2) the ECG findings have relatively low likelihood ratios to have clinical use.     

Body surface maps and the conventional 12-lead ECG compared by studying their performances in classification of old myocardial infarction

The performance of body surface potential maps and the 12-lead ECG in the detection of old myocardial infarction has been compared in a two-group (54 normals; 52 infarctions) classification procedure (linear discriminant analysis). Three methods for data reduction of body surface maps were compared: 1) time integration, 2) one-step reduction in eigenvectors and 3) two-step reduction in spatial and temporal eigenvectors. Features were taken from the reduction variables by a stepwise selection procedure. From 90% to 93% correct classifications could be obtained using three features from the map data over the initial 30 ms (Q interval) of the QRS wave for all three methods considered. Using the 100 ms (QRS) interval 86% correct classifications were obtained using method 1, and up to 90% and 87% for methods 2 and 3, respectively. In a further analysis the classification based on body surface maps was compared to the one based on the 12-lead ECG. The 12-lead ECG was treated as a restricted set of the body surface mapping leads, so the same methods of data reduction, feature extraction and classification could be applied to both sets of data. Applying method 1 (time integration) 89% correct classifications were obtained using data taken from the 30 ms interval of the 12-lead ECG and a subsequent reduction to three features. When using the 100 ms interval the result was 79% also using three features. The results of method 2 applied to the 12-lead ECG were 89% (30 ms interval, three features) and 78% (100 ms interval, three features).     

A comparison of 2-lead, 6-lead, and 12-lead ECGs in patients with changing edematous states: implications for the employment of quantitative electrocardiography in research and clinical applications

OBJECTIVE: Precordial ECGs reveal significant intrasubject variability due to the inexact employment of the recommended V(1)-V(6) chest landmarks. Also, as per the Einthoven law, the six limb leads can be derived from leads 1 and 2. The purpose of this study was to evaluate whether the 12-lead ECG could be substituted by ECG sets with a limited number of leads. MATERIALS AND METHODS: The performance of three ECG systems (ie, the 12-lead ECG, a 6-lead ECG comprising the limb leads, and a 2-lead ECG comprising exclusively leads 1 and 2) was evaluated in data from 28 patients with anasarca (AN), 28 control patients, 10 patients who had undergone hemodialysis, and 3 patients with idiopathic dilated cardiomyopathy. RESULTS: Linear regression analyses of changes in ECG data with the weight gain of patients with AN and the intercorrelations of the three ECG systems in the various patient subgroups were found to be statistically significant at p = 0.0005 and r values ranging from 0.61 to 0.99, which are suggestive of good/excellent correlations. However, regression analyses of peak weight (PW) gain with changes in the 2-lead ECG (r = 0.43; p = 0.02) and 6-lead ECG (r = 0.48; p = 0.01), and half of PW gain and 12-lead ECG (r = 0.41; p = 0.03), 6-lead ECG (r= 0.18; p = 0.35), and 2-lead ECG (r = 0.43; p = 0.02) revealed poor correlations. CONCLUSION: ECG systems, comprising 2 or 6 leads, can be substituted for the 12-lead ECG for certain clinical and research applications (pertaining to the amplitude of QRS complexes), attesting to the inherent redundancy of the information from the 12-lead ECG.     

Assessment of right ventricular overload in patients with chronic pulmonary disease by 12-lead electrocardiography, vectorcardiography, and body surface electrocardiographic mapping

Twenty-eight patients with chronic pulmonary diseases were examined with standard 12-lead electrocardiogram (ECG), vectorcardiogram (VCG), and body surface ECG mapping (MAP). The electrocardiographic findings were compared with results of 99 mTc radionuclide right ventriculography or T1-201 myocardial scintigraphy. In a stepwise multiple regression analysis between the electrocardiographic parameters and right ventricular ejection fraction, only the amplitude of the negative P wave in V2 (r = 0.69), the posterior force of P loop in VCG (r = 0.71), and the size of -2SD area at 50 msec QRS potential departure map (r = 0.55) were selected as the parameters in standard ECG, VCG, and MAP, respectively. On the radionuclide ventriculography and myocardial scintigraphy, 14 patients were judged to have right ventricular overload. The criteria by VCG, and MAP had better sensitivity and specificity for right ventricle overload than those by 12-lead ECG. VCG criteria of Chou et al had sensitivity of 93% and specificity of 71%. MAP criteria, departure index of F3 or F4 less than or equal to -2, had sensitivity of 86% and specificity of 79%. The electrocardiographic findings by standard 12-lead ECG, VCG and body surface ECG mapping are useful parameters for the noninvasive detection of right ventricular overload in patients with chronic pulmonary diseases.     

Comparison of 12-lead and computer-analysed 3 orthogonal lead electocardiogram in coronary artery disease.

The computer-analysed 3 orthogonal lead system ("3-lead ECG") provides a rapid and consistent interpretation of the electrocardiogram. In 102 patients undergoing selective coronary arteriography, the ability of such a system to predict the presence of absence of coronary artery disease and the site of myocardial ischaemia was compared with that of the conventional scalar electrocardiogram interpreted by cardiologists ("12-lead ECG"). Each system predicted the site of myocardial ischaemia with equal accuracy. The 3-lead ECG was a more sensitive index (3-lead ECG sensitivity=77%; 12-lead ECG sensitivity=70%) but less specific (3-lead ECG specificity=74%; 12-lead ECG specificity=78%). In coronary artery disease, the predictive "index of merit" for the 3-lead ECG was 0-51, compared with 0-48 for the 12-lead ECG. These results provide further justification for the routine use of the 3 orthogonal lead electrocardiogram.     

12导联同步动态心电图在冠心病心肌缺血诊断中的应用

目的探讨12导联同步动态心电图（DCG）在冠心病心肌缺血诊断中的价值,进一步推广在基层医院中的应用。方法选取本院就诊中疑诊为冠心病的250例作为研究对象,同时行12导联和3导联同步DCG24h监测,收集相关信息,进行统计学分析。结果 12导联同步DCG对心肌缺血诊断的阳性率明显高于3导联者,两者之间有显著差异（P〈0.05）;12导联同步DCG对下壁、侧壁心肌缺血的诊断优于3导联同步记录。结论 12导联描记在冠心病心肌缺血诊断上明显优于3导联记录,可以减少冠心病的漏诊率。     

肺心病合并冠心病心电图分析

目的探讨肺心病合并冠心病心电图的特点。方法回顾我院住院病例选择肺心病和肺心病合并冠心病各120例均行同步十二导联心电图检查,必要时进行24 h动态心电图检查对比心电图的变化。结果肺心病合并冠心病组(合并组)比肺心病组心电图改变明显,两者有显著差异结论心电图及动态心电图的某些特殊改变能提示肺心病合并冠心病。     

Supplemented standard 12-lead electrocardiogram for optimal diagnosis and reconstruction of significant body surface map patterns

In this study, based on 120-lead body surface potential maps (BSPMs), we explored the improvement in electrocardiogram (ECG) diagnosis obtained by adding additional leads and using estimation of unmeasured leads. We found that adding a few leads observed to be optimal for diagnosis or signal capture combined with the existing 12-lead ECG improves diagnostic performance. Separately, using reconstruction (estimation) of BSPMs and using diagnostic criteria derived for maps also improve diagnostic performance over that provided by the recorded 12-lead ECG alone. Combining these 2 ideas, namely, addition of optimal leads and estimation of BSPMs improves performance even more.     

心电图评分在急性肺血栓栓塞症严重程度评估中的应用

目的探讨心电图（ECG）评分在急性肺血栓栓塞症（PTE）患者危险评估的应用价值。方法观察ECG异常类型及其评分值;评价分值与放射性核素全肺灌注缺损百分数（PPDS）、超声心动图右心室前后径、肺动脉收缩压（SPAP）、动脉血气指标的关系,应用受试者工作特征（ROC）曲线评估ECG分值预测PPDS〉50％和SPAP〉50mmHg的准确性。结果40例急性PTE患者的ECG评分值与PPDS和右心室前后径呈正相关;与SPAP呈等级正相关;与PaO2呈负相关。ECG分值预测PPDS〉50％和SPAP〉50mmHg准确性的ROC曲线下面积分别为0．888和0．763。ECG分值〉9．5时预测PPDS〉50％的敏感性和特异性分别为76．2％和84．2％;ECG分值〉11．5时预测SPAP〉50mmHg的敏感性和特异性分别为70．0％和73．9％。结论ECG评分是评估急性PTE严重程度的良好指标。     

A blind comparison of four non-invasive twelve-lead electrocardiogram algorithms for predicting susceptibility to ventricular tachycardia

INTRODUCTION: To reduce QT measurement error, a new method was tested in which high-gain, high-speed, simultaneous 12-lead electrocardiographic (ECG) recordings were obtained during a single cardiac cycle. To increase its predictive power, the utility of combining QTD with the QRS duration for predicting susceptibility to ventricular tachyarrhythmia (VT) was analyzed. METHODS AND RESULTS: A total of 113 patients referred for electrophysiological study underwent baseline simultaneous 12-lead ECG followed by electrophysiological study to determine VT inducibility. Twenty-six patients had inducible VT while 87 patients did not. QT intervals and the width of QRS complex were measured from a single cardiac cycle with high-gain (8 times normal) and high-speed (100 mm/second) 12-lead ECG recordings. This method resulted in 100% QT interval identification throughout all 12 leads for every patient. Receiver-operator characteristic curves (ROC) and the areas under the ROC curves (AUC) were used to quantitatively analyze the performance of four ECG variables (QTD3, QTD12, QTD12 + QRS and QTD3 + QRS). All four ECG variables were significantly increased in the patients with inducible VT as compared to those without inducible VT. The QTD3 algorithm was less useful than QTD12 in predicting inducible VT; however, the addition of QRS duration to all QTD algorithms enhanced VT detection. CONCLUSION: 1) QRS duration has an incremental benefit in the detection of VT when combined with QTD; 2) QTD12 + QRS duration provided the highest predictive power among the four tested algorithms; 3) high-gain, high-speed 12-lead ECG recordings reduced QT measurement error.     

Right precordial and posterior electrocardiographic leads do not increase detection of ischemia in low-risk patients presenting with chest pain

BACKGROUND: A number of innovative approaches have been investigated for their value in the early detection of acute ischemia or infarction in patients presenting to the emergency department (ED) with chest pain suggestive of a cardiac origin. Prior investigations have demonstrated the utility of adding right precordial and posterior chest leads to the standard 12-lead electrocardiogram (ECG) for identifying right ventricular and posterior wall infarctions in the ED. HYPOTHESIS: To assess the utility of additional ECG leads in low-risk patients presenting to the ED with symptoms suggestive of acute coronary syndromes who are managed in a chest pain evaluation unit (CPEU). METHODS: We studied low-risk patients who presented to the ED with chest pain compatible with myocardial ischemia. Low-risk patients were identified by a normal 12-lead ECG, no arrhythmias or hemodynamic instability, and one negative serum cardiac troponin I. Patients were admitted to the CPEU where a 16-lead ECG was recorded by the addition of 2 right-sided precordial leads (V4R, V5R) and 2 posterior leads (V8, V9) to the standard 12-lead ECG. RESULTS: The 16-lead ECG system was applied to 316 consecutive patients. The study group was a middle-aged population with equal numbers of men and women and an average of 2 cardiac risk factors per patient. The 16-lead ECG demonstrated evidence of myocardial injury in only 1 patient and no evidence of ischemia in any of the 316 patients. CONCLUSION: In patients presenting to the ED with chest pain and evidence of low clinical risk by our criteria, the addition of both right-sided precordial and posterior chest leads to the standard 12-lead ECG did not provide additional information for risk stratification.     

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.     

Detection of acute ischemia from the EASI-derived 12-lead electrocardiogram and from the 12-lead electrocardiogram acquired in clinical practice

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 ΣST, and, by using the bootstrap method, determined the mean sensitivity and specificity for recognizing the “ischemic” state at various thresholds of ΣST. 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.     

Prehospital 12-lead ST-segment monitoring improves the early diagnosis of acute coronary syndrome

Aims/MethodsWe studied 620 patients who activated “911” for chest pain symptoms to determine the sensitivity and specificity of 12-lead electrocardiogram (ECG) ST-segment monitoring in the prehospital period (PH ECG) for diagnosing acute coronary syndrome (ACS) and to assess whether the addition of PH ECG signs of ischemia/injury to the initial hospital 12-lead ECG obtained in the emergency department would improve the diagnosis of ACS.ResultsThe sensitivity and specificity of the PH ECG were 65.4% and 66.4%. There was a significant increase in sensitivity (79.9%) and decrease in specificity (61.2%) when considered in conjunction with the initial hospital ECG (P < .001). Those with PH ECG ischemia/injury were more than 2.5 times likely to have an ACS diagnosis than those who had no PH ECG ischemia/injury (P < .001).ConclusionsPrehospital ECG data obtained with 12-lead ST-segment monitoring provides diagnostic information about ACS above and beyond the initial hospital ECG.     

False ST elevation in a modified 12-lead surface electrocardiogram

Precise recording of the standard 12-lead electrocardiogram (ECG) is technically time consuming. Placing limb leads on the torso has the major advantages of ease of use, increased speed of application, and decreased artifact. This modified ECG frequently substitutes for the standard 12-lead ECG in intensive care units to detect ischemia, although its implementation should be limited to interpreting arrhythmias. We describe a patient who was misdiagnosed with acute inferior myocardial infarction in a modified 12-lead ECG. To the best of our knowledge, this is the first case report regarding detection of false ST elevations in this setting. Always, a standard 12-lead ECG is recommended to evaluate any ST-T changes.     

Derived 12-lead electrocardiogram in the assessment of ST-segment deviation and cardiac rhythm

BACKGROUND: There are little data on the validation of 12-lead electrocardiogram (ECG) derived by the EASI lead system used for continuous monitoring in critical care settings. OBJECTIVE: The objectives of this study were to determine the accuracy of 12-lead ECG derived by the EASI lead system in the detection of ST-segment deviation and cardiac rhythm compared with the standard 12-lead ECG. METHODS: All patients admitted to the coronary care unit were studied. Kappa statistics was used to calculate the agreement between both ECG systems in the determination of cardiac rhythm and premature ventricular complex morphology. ST-segment analysis was performed in patients with acute coronary syndromes. Pearson correlation was used to correlate the ST-segment deviation between both techniques. The sensitivity and specificity of the determination of significant ST-segment deviation by the EASI lead system were calculated. RESULTS: There were a total of 282 patients enrolled in this study. There was a complete agreement in the interpretation of cardiac rhythm between the 2 methods (kappa = 1). Analysis of ST-segment deviation of 12-lead ECG also showed a significant correlation (correlation coefficient varied from 0.62 in lead I to 0.823 in lead aVF with a P value of <.001 in all leads) between the 2 methods with very high sensitivity and specificity in the detection of significant ST-segment elevation and depression. CONCLUSION: The 12-lead ECG derived by the EASI lead system is an accurate and reliable information for the assessment of ST-segment deviation and cardiac rhythm in critically ill patients.     

Comparison of ST depression recorded by Holter monitors and 12-lead ECGs during coronary angiography and exercise testing

Data from previous studies are debatable regarding whether Holter monitors are a reliable electrocardiographic indicator of ischemia, for which the 12-lead electrocardiogram (ECG) is the standard. Simultaneous 12-lead and Holter ECGs were performed on 30 patients with typical angina pectoris during coronary angiography or exercise testing. ST depression recorded by both methods was directly compared, using the 12-lead ECG as the reference. The Holter tapes were also scanned by two automated ST analysis programs and the results were compared to 12-lead ECGs. Only 66 of the 178 12-lead ECG ST depression events were also present on the Holter recordings (37.1% Holter sensitivity). ST depression was underestimated by the Holter recordings compared to the 12-lead ECGs (p < 0.0001). The majority (67.0%) of ST depression events identified by one computer program were false positive events. The degree of ST depression was overestimated compared to 12-lead ECGs by the second program (p = 0.0033). Holter-detected ST depression may not be a reliable ECG indicator of myocardial ischemia.     

ST depression only on the initial 12-lead ECG: early diagnosis of acute myocardial infarction.

AIMS: To compare the diagnostic ability of the 12-lead ECG with body surface mapping for early detection of acute myocardial infarction in patients presenting with ST depression only on the 12-lead ECG. METHODS AND RESULTS: Fifty-four consecutive patients with chest pain <24 h and ST depression were recruited. A 12-lead ECG and 80-lead body surface map were recorded at presentation from which univariate and multivariate prediction models of acute myocardial infarction were developed. Patients were randomly divided into a training-set and a validation-set. Acute myocardial infarction occurred in 16/30 training-set and 8/24 validation-set patients. Univariate prediction of acute myocardial infarction by the 12-lead ECG, based on the depth or numbers of leads with ST depression, was not improved by assessment of ST elevation outside the conventional 12 leads using body surface mapping. The optimum multivariate 12-lead ECG model developed in training-set patients (six ST depression variables) had poor sensitivity (38%) although good specificity (81%) for acute myocardial infarction when tested prospectively in validation-set patients. In contrast, the optimum body surface mapping model developed in training-set patients (three isointegral or isopotential variables) achieved high sensitivity (88%) whilst maintaining good specificity (75%) for acute myocardial infarction when tested prospectively in validation-set patients. CONCLUSION: Body surface mapping, when compared with the 12-lead ECG, may improve the early diagnosis of acute myocardial infarction in patients presenting with chest pain and ST depression only on the 12-lead ECG.     

Electrocardiographic and hemodynamic correlations in primary pulmonary hypertension

In order to evaluate the pulmonary hemodynamics in primary pulmonary hypertension, the relation between the standard 12-lead electrocardiogram (ECG) and pulmonary hemodynamics as determined by right-heart catheterization was analyzed. Significant positive correlations were noted between amplitude of the R in V1, the R/S ratio in V1, and the pulmonary artery systolic pressure (r = 0.46 and 0.50, respectively, p less than 0.01). An amplitude of the R in V1 of more than 1.2 mV indicated a pulmonary artery systolic pressure of more than 90 mmHg with a sensitivity of 94% and a specificity of 47%. The cardiac index showed a significant positive relationship with amplitude of the R in V5 and V6 and the R/S ratio in V5 and V6 (r = 0.46, 0.46, 0.39, and 0.48, respectively; each with a p less than 0.01). Moreover, an AQRS greater than or equal to 100 degrees, and either an SV6 greater than or equal to 0.7 mV, or R/SV6 less than or equal to 2 indicated a cardiac index of less than 2.8L/min/m2 with a sensitivity of 82% and 84% and a specificity of 86% and 100% respectively. This study suggests, therefore, that the 12-lead ECG is useful for the evaluation of the severity of pulmonary hypertension by its ability to predict pulmonary artery systolic pressure and cardiac index with clinically useful accuracy.