Determination of the ability of high-frequency ECG to estimate left ventricular mass in humans, determined by magnetic resonance imaging

BACKGROUND: Previous studies have shown a significantly higher correlation between left ventricular mass index (LVMi) and high-frequency QRS components (HF-QRS) than between LVMi and QRS amplitudes in the standard frequency range in rabbits. The purpose of the present study was to compare ECG measurements from standard and high-frequency ranges with left ventricular mass (LVM) and LVMi determined by magnetic resonance imaging in humans. METHODS: Sixty-two normal subjects were studied. Signal-averaged ECGs from the 12 standard leads were analysed in the standard frequency range (0.05-150 Hz), in the middle (25-100 Hz) and high end (50-150 Hz) of the standard frequency range and in the 150-250 Hz range. Root-mean square (RMS) values from the HF-QRS and QRS amplitude measurements from the standard ECGs were compared with LVM and LVMi. RESULTS: The correlations between LVMi and HF-QRS were similar to those between LVMi and standard ECG. When regarding LVM, however, the correlations found in the standard ECG were higher than those found in HF-QRS. CONCLUSIONS: Contrary to previous results in animals, we found in humans no better correlation between HF-QRS and LVM/LVMi than between standard ECG and LVM/LVMi.     

Serial changes in the high-frequency ECG during the first year following acute myocardial infarction

BACKGROUND: Previous studies have shown reduced high-frequency QRS components (HF-QRS) after acute myocardial infarction (MI). The purpose of this study was to investigate serial changes in HF-QRS during the first year following acute MI. METHODS: A total of 75 patients were included. Standard- and high-frequency ECGs were recorded on five occasions during the year following the MI (a few days after the MI, after 6 weeks, and after 3, 6 and 12 months). RESULTS: There was a statistically significant increase in HF-QRS during the follow-up year (P = 0.002). There were no significant differences in HF-QRS when comparing either the infarct location or the presence or absence of reperfusive therapy. Large differences in HF-QRS were observed, both intra-individually and inter-individually, during the year. CONCLUSIONS: There was a statistically significant increase in HF-QRS during the year following acute MI.     

标准12导联心电图与标准监护Ⅱ导联监测心肌缺血对照研究

目的评价标准12导联心电图与标准监护Ⅱ导联监测心肌缺血的有效性和敏感性。方法以标准12导联心电图作为判断心肌缺血的标准,将50例有ST段改变的心脏病患者设为病例组,45例无ST段改变的心脏病患者设为非病例组,比较标准12导联与标准监护Ⅱ导联心电图心肌缺血检出率。结果50例经标准12导联心电图发现存在心肌缺血的患者,同时经标准监护Ⅱ导联检测仅发现15例患者存在心肌缺血,差异有极显著性（χ^2=53．846,P〈0．01）,且标准监护Ⅱ导联心电图出现心肌缺血改变假阳性率为11．1％。结论标准监护Ⅱ导联心电图并不能有效发现心肌缺血,在l临床监护中需同时描记标准12导联心电图。     

Additional electrocardiographic leads in the ED chest pain patient: right ventricular and posterior leads

In the evaluation of the patient with chest pain, the 12-lead electro cardiogram is a less-than-(ECG) perfect indicator of acute myocardial infarction (AMI), particularly when used early in the course of the acute ischemic event; this relative insensitivity for AMI results from many different issues, including a less-than-optimal imaging of certain areas of the heart. It has been suggested that the sensitivity of the 12-lead ECG can be improved if 3 additional body surface leads are used in selected individuals. Acute posterior (PMI) and right ventricular myocardial infarctions are likely to be underdiagnosed, because the standard lead placement of the 12-lead ECG does not allow these areas to be assessed directly. Additional leads frequently used include leads V(8) and V(9), which image the posterior wall of the left ventricle, and lead V(4R), which reflects the status of the right ventricle. The standard ECG coupled with these additional leads constitutes the 15-lead ECG, the most frequently used additional lead ECG in clinical practice. The use of the additional leads might not only confirm the presence of AMI, but also provide a more accurate reflection of the true extent of myocardial damage.     

Non-invasive detection of coronary artery disease by a newly developed high-frequency QRS electrocardiogram

Compared to other non-invasive methods, the conventional 12-lead electrocardiogram (ECG) has low sensitivity and specificity for identifying coronary artery disease (CAD). We compared the newly developed high-frequency QRS electrocardiogram (HFQRS ECG, 150-250 Hz) with adenosine sestamibi myocardial perfusion study (MPI)-the most sensitive non-invasive study in cardiology practice. Using advanced 12-lead computer-based ECG software recently developed at NASA, criteria for a positive 12-lead HFQRS-ECG test for obstructive CAD were developed using 300 signal-averaged beats from patients undergoing elective coronary angiograms for evaluation of chest pain. These criteria, which rely strictly upon the presence or the absence of morphologic 'reduced amplitude zones' (RAZs) and not upon the 'root mean squared' (RMS) voltage amplitudes of the HFQRS complexes, were then applied prospectively to 18 patients undergoing MPI. Active CAD was considered present when reversible ischemic defects were present on MPI. Of the 18 patients, 9 had reversible defects on MPI (positive scan), whereas the other 9 had no reversible perfusion defects (negative scan). Patients with a positive nuclear study went on to coronary angiography confirming CAD, except in one patient who had nonobstructive coronary disease (<50% stenosis). Eight of the 18 subjects therefore had active CAD, whereas 10 were judged not to have active CAD. The 12-lead HFQRS-ECG result was consistent with nuclear scan results in 14 of 18 patients. The HFQRS-ECG and nuclear results differed in: (1) one patient who had a low score positive MPI, negative HFQRS-ECG and normal coronary angiogram; (2) one patient who had a small reversible anterior wall perfusion defect, 60% LAD lesion on angiogram but a negative HF-QRS result; and (3) two individuals who had positive HFQRS-ECG results in the face of negative nuclear scans but who did not undergo angiography. 12-lead HFQRS ECG had excellent sensitivity (87.5% based on 7/8 true positives correctly identified) and specificity (no worse than 80%, >8/10 true negatives correctly identified) for identifying CAD. 12-lead HFQRS ECG is an easily performed, inexpensive and potentially widely available technique that utilizes the same leads and electrodes as the conventional 12-lead ECG. It had accuracy comparable to MPI in this study. Resting 12-lead HFQRS ECG appears to be a very promising non-invasive technique for identifying CAD and may represent a viable alternative to many of the more expensive and time-consuming techniques presently utilized for non-invasively identifying CAD.     

Electrocardiographic changes during prolonged coronary artery occlusion in man: comparison of standard and high-frequency recordings

Detection of acute myocardial ischaemia using electrocardiographic methods is generally based on assessment of the ST segments in the standard 12-lead electrocardiogram (ECG). Several studies have also shown changes in high-frequency QRS components during acute ischaemia. The purpose of the present study was to determine the changes in high-frequency QRS components during prolonged percutaneous transluminal coronary angioplasty (PTCA) and to compare these changes with ST-segment deviations in the standard 12-lead ECG. The study population consisted of 19 patients receiving prolonged PTCA. Standard and high-resolution signal-averaged ECGs were recorded before and during balloon inflation. The high-resolution recordings were performed using bipolar X, Y and Z leads. The QRS complexes in the high-resolution signal-averaged ECGs were analysed within a bandwidth of 150–250 Hz. During inflation, significant reductions in high-frequency QRS components were observed (12–72%). Changes in the high-frequency QRS components were seen in four of the patients without ST-segment deviation in the standard ECG. The correlation between the ST-segment deviation and the reduction in high-frequency QRS components was weak (r = 0·27). Acute coronary artery occlusion produces changes in high-frequency QRS components, even in the absence of ST-segment deviation in the standard ECG. Further studies need to be carried out to evaluate whether analysis of high-frequency QRS components could provide a method for detecting myocardial ischaemia and give additional information to that available in the ST segment in the standard ECG.     

急性ST段抬高型心肌梗死的非典型心电图改变

心电图是广泛使用和容易获得的最初诊断工具。急性心肌梗死（AMI）的治疗有赖于其临床表现、心电图及心肌坏死标志物的综合判断。识别高危心电图及其微妙变化将使患者早期血运重建明显获益。本文主要对非典型的心电图诊断相当于急性ST段抬高型心肌梗死（STEMI）的一些规律,包括左束支传导阻滞（LBBB）满足Sgarbossa标准、Wellens′综合征、QRS波终末变形、超急性T波、de Winter征和aVR导联抬高等进行综述。     

冠脉旁路移植术后心电图改变的临床评价

目的 探讨冠脉旁路移植术(coronary artery bypass grafting，CABG)后各种缺血性心电图改变的临床意义，评价其围术期心梗和心肌缺血的早期诊断价值及与术后早期预后的相关性。方法 108例患者于CABG术后2—10d进行2次／d的12标准导联心电图检查，术后第7天、第14天常规12导联心电图检查1次。依据急性心梗及心肌缺血的心电图诊断标准记录阳性改变。根据有无心电图阳性改变将本组患者分为研究组和对照组，进行手术前后超声心动图EF值及室壁运动情况、术后心肌酶、血流动力学情况和相关并发症等的比较及统计学分析。结果 单纯ST-T改变者51例(研究组1)，出现Q波者15例(研究组2)，无阳性改变者42例(对照组)，各研究组与对照组在以上观察指标的比较中无显著差别。结论 CABG术后心电图的缺血性改变并非围术期心梗和心肌缺血的特异性诊断指标及术后早期顸后的判断指标。     

QRS duration in high-resolution methods and standard ECG in risk assessment after first and recurrent myocardial infarctions

Background: Prolonged QRS duration (QRSd) is associated with increased mortality after myocardial infarction (MI). Only little data exist about its predictive ability and relationships to clinical variables in the present era of active treatment of myocardial ischemia and cardiac dysfunction. We investigated whether QRSd in high-resolution methods and standard ECG predict arrhythmic events and cardiac death in post-infarction patients with cardiac dysfunction and how it relates to clinical variables, with a special emphasis on history of previous MI.
Methods and Results: Patients (n = 158) with acute MI and cardiac dysfunction had magnetocardiography (MCG), signal-averaged ECG (SAECG), and ECG registered at discharge. Patients with a previous MI had significantly longer QRSd although their left ventricular function was almost similarly impaired. During the mean follow-up of 50 ± 15 (range 1–72) months, 32 patients died and 17 (53%) of the deaths were classified as cardiac. Eighteen patients had an arrhythmic event. QRSd >121 ms in MCG and >114 ms in SAECG were significant predictors of arrhythmic events and cardiac death, whereas QRSd in ECG predicted only cardiac death. In multivariate analysis, QRSd in MCG (hazard ratio (HR) = 3.6, P = 0.007) and SAECG (HR = 4.6, P = 0.016) predicted only arrhythmic events, whereas QRSd in ECG was an independent predictor of cardiac death.
Conclusions: Prolonged QRSd in MCG and SAECG are powerful indicators of the arrhythmia substrate in post-infarction patients with cardiac dysfunction, whereas prolonged QRSd in standard ECG associates with increased risk of cardiac death.     

Evaluation of left ventricular mass measured by 3D echocardiography using magnetic resonance imaging as gold standard

OBJECTIVE: Increased left ventricular mass (LVM) and presence of left ventricular hypertrophy (LVH) are predictors of cardiovascular morbidity and mortality, but can be reversed with proper treatment of the underlying cause. Therefore accurate as well as reproducible methods for diagnosis and follow-up are needed. We evaluated different modalities by which to measure LVM in patients with no known LVH using magnetic resonance imaging (MRI) as the gold standard: ECG using the formulae proposed by Sokolow-Lyon and Cornell, 2D echocardiography and 3D echocardiography. METHODS: 34 subjects were included in the study; 17 had a history of myocardial infarction, 7 had pulmonary hypertension and 10 were healthy. All patients and controls had a standard 12-lead ECG, a transthoracic 2D and 3D echocardiographic study and a cardiac MRI. RESULTS: ECG estimates of LVM correlated poorly with LVM by MRI (r = 0.18, NS and 0.16, NS for Sokolow-Lyon and Cornell, respectively), whereas a moderate correlation between 2D and 3D echocardiography and MRI was observed (r = 0.63, p<0.001 and r = 0.74, p<0.001, respectively). All methods were reproducible with no significant bias. CONCLUSION: LVM measured by 3D echocardiography is highly accurate compared to LVM measured by MRI. LVM calculated from 2D echocardiography also proved useful, whereas estimates of LVM by ECG are inaccurate in a non-hypertrophic population.     

Body surface mapping versus the standard 12 lead ECG in the detection of myocardial infarction amongst emergency department patients: a Bayesian approach

OBJECTIVE: To determine if body surface mapping (BSM) is better than the standard 12 lead ECG in the diagnosis of acute myocardial infarction amongst emergency department patients. SETTING: A University affiliated inner-city emergency department. PARTICIPANTS: People presenting to an emergency department with symptoms compatible with myocardial ischaemia/infarction. MAIN OUTCOME MEASURES: Myocardial infarction as defined by either standard 12 lead ECG changes with associated cardiac marker rise, Troponin T >0.1 microg/ml at > 12 h or autopsy/surgical findings of fresh macroscopic infarction. RESULTS: BSM had an overall sensitivity of 47.1% versus 40% for the 12 lead ECG (P < 0.001). Specificity for the BSM was 85.6% versus 93.7% for the 12 lead ECG (P < 0.001). These findings were consistent for low/moderate and high risk subgroups. Bayesian analysis demonstrates that indiscriminate use of BSM would result in a clinically important overdiagnosis of myocardial infarction amongst emergency department patients. CONCLUSIONS: BSM has a higher sensitivity, but a lower specificity for the diagnosis of myocardial infarction.     

Interpreting 12-lead electrocardiograms for acute ST-elevation myocardial infarction: what nurses know

In patients with acute myocardial infarction, early reperfusion and sustained patency of the culprit artery are important determinants of survival. The 12-lead electrocardiogram (ECG) is considered the noninvasive gold standard for identification of acute ST-elevation myocardial infarction. Nurses play a critical role in the process of obtaining, interpreting, and communicating ECG findings. This study evaluates nurses' ability to differentiate ischemic from nonischemic ECG patterns, to detect affected ECG leads and location of ischemia, and assesses skill level by hospital unit type. Seventy-five nurses were given a set of 6 patient scenarios, each with a corresponding 12-lead ECG, and asked to identify the presence or absence of ischemia. Fourteen (19%) of the 75 nurses correctly identified the presence or absence of ischemia in all 6 scenarios. Of the 3 ECGs with a myocardial infarction pattern, 59 (79%) of the nurses identified all 3 as ischemic; however, no one was able to determine the correct leads, location, or amplitude of ST-segment elevation. For the 3 nonischemic ECGs, 37 (49%) of the nurses identified a normal ECG as ischemic, 47 (63%) determined that an early repolarization pattern was ischemic, and 34 (45%) indicated that a left bundle branch block pattern was ischemic. These results not only identify educational opportunities but also provide important information for researchers implementing clinical trials evaluating the use of bedside ECG monitoring systems for detection of acute myocardial ischemia.     

Using the 12-lead ECG to assess acute coronary patients

Acute coronary syndromes (ACS) are characterized by the rupture of unstable plaque within coronary arteries. Depending on the extent of the ensuing occlusion and myocardial damage, ACS can be classified as unstable angina, non-ST elevation myocardial infarction (MI) and ST elevation MI. The electrocardiogram (ECG) is an invaluable tool in the assessment of patients with ACS. It provides evidence for the location of myocardial ischaemia, injury and infarction and is a crucial factor in the decision to administer thrombolytic agents and other management strategies. The 12-lead ECG is limited to a view of the left ventricle, however it can be extended to provide additional information about the right ventricular and posterior walls. Critical care nurses with ECG skills can contribute to the early detection and management of patients with ACS.     

Posterior myocardial infarction with isolated ST elevations in V8 and V9: Is this an "ST elevation MI"?

We report a case of a 53-year-old man whose first manifestation of coronary artery disease was an acute isolated posterior myocardial infarction (IPMI). Acute IPMI is relatively uncommon and predominantly due to occlusion of the left circumflex coronary artery. IPMI is challenging to diagnose due to the absence of ST segment elevation on a standard 12-lead electrocardiogram (ECG) even in the setting of total coronary artery occlusion and transmural (Q-wave) infarct. We discuss the diagnostic implications of the absence of tall R waves in leads V1 and V2 on this patient's ECG. The utility of posterior leads (V7 through V9) is demonstrated. The controversy surrounding the use of thrombolytic therapy or primary angioplasty in the setting of acute IPMI without ST segment elevation on a standard 12-lead ECG is reviewed.     

不稳定型心绞痛与心电图检测的价值研究

目的:探讨不稳定型心绞痛(UAP)与心电图检测的临床价值。方法:回顾性分析56例UAP患者标准12导联ECG的一过性心肌缺血、心率变异、QTI以及ST-T段变化。结果:一过性心肌缺血持续时间长、心率变异<50 ms、QTI增加以及ST-T段压低,近期内发生恶性室性心律失常及心脏病事件明显增加。结论:ECG是除生化指标外,对UAP进行危险分析并指导治疗等方面都具有十分现实的临床意义。     

Parameters of variation pulsometry, Q-T interval dispersion and frequency of occurrence of late potentials in acute myocardial infarction

Registration of standard and high-resolution EGCs, echocardiography in 90 ischemic heart disease (IHD) patients on myocardial infarction week 2 to 6 has demonstrated that deterioration of local myocardial contractility and development of left ventricular dilation increase frequency of late ventricular potentials and worsen parameters of high-resolution ECG. Left ventricular dysfunction is associated with defects in autonomic regulation of cardiac activity. Diminished myocardial contractility had no significant effect on dispersion of repolarisation.     

A comparison between EASI system 12-lead ECGs and standard 12-lead ECGs for improved clinical nursing practice

Aims and objectives. This study was carried out to verify the accuracy of 12‐Lead ECG, obtained through a continuous ECG monitoring system with five cables positioned in EASI mode, to identify basic ECG alterations. Background. This study concerns continuous ECG monitoring systems in Coronary Care Units. Continuous ECG monitoring is an important device for nursing surveillance and is useful in decreasing adverse events. Design and method. Thirteen patients admitted consecutively to the Coronary Care Unit for Acute Myocardial Infarction underwent daily and simultaneous recording of a12‐lead ECG using both procedures: EASI ECG and STANDARD ECG. A sample of 1164 ECG leads acquired in EASI mode was compared with a sample of as many ECG leads acquired using the standard procedure with a traditional cardiograph. Results and conclusions. In the Coronary Care Unit, Continous ECG monitoring with five cables positioned in EASI mode is a valid alternative to the standard 12‐lead ECG for cardiac rhythm abnormalities detection and for acute myocardial ischemia and old myocardial infarction assessment. Therefore, the EASI system might be advantageous for long‐term patient monitoring. Relevance to clinical practice. The EASI system represents a valid device for the nursing surveillance of patients who need continuous ECG monitoring, improves clinical nursing practice in Coronary Care Units, supports the reduction of adverse events such as cardiac arrest and reduces the hospital costs.     

Use of the pacing pulmonary arterial catheter to detect endocardial electrical activity during hypothermic cardioplegic arrest

The pacing Swan-Ganz catheter was evaluated for its ability to monitor atrial and ventricular electrical activity during cardioplegic arrest on cardiopulmonary bypass. This endocardial electrical activity was compared with the activity found on the standard electrocardiogram (ECG). The atrial electrodes detected activity that was noted also by visual inspection. The ventricular electrodes detected recurring electrical activity in 7 of 18 patients. Three of these 7 patients did not have simultaneous standard ECG activity, indicating that, in the usual monitoring circumstances, this ventricular electrical activity would not have been treated with repeat cardioplegia. If the pacing Swan-Ganz catheter is used for clinical care, it can be used also to monitor myocardial electrical activity during cardioplegic arrest.     

Interpretation and clinical significance of the QRS axis of the electrocardiogram

The frontal plane QRS axis of the standard 12-lead electrocardiogram (ECG) is easily and accurately measured by the clinician. A simple method of estimating this axis is discussed. This axis is age-dependent. We reviewed the literature to determine if evidence exists of an association between an “abnormal” QRS axis and clinically significant myocardial disease. We also examined the literature for clinical correlation of a “normal” QRS axis with the absence of myocardial pathology. We found that although an abnormal QRS axis (falling outside the limits of ⁺30° and ⁺90°) occurs in a small number of normal individuals, its presence should prompt a thorough evaluation of all the parameters of the ECG to look for myocardial disease.     

Electrocardiographic manifestations of hypothermia

Hypothermia is generally defined as a core body temperature less than 35 degrees C (95 degrees F). Hypothermia is one of the most common environmental emergencies encountered by emergency physicians. Although the diagnosis will usually be evident after an initial check of vital signs, the diagnosis can sometimes be missed because of overreliance on normal or near-normal oral or tympanic thermometer readings. The classic and well-known electrocardiographic (ECG) manifestations of hypothermia include the presence of J (Osborn) waves, interval (PR, QRS, QT) prolongation, and atrial and ventricular dysrhythmias. There are also some less known (ECG) findings associated with hypothermia. For example, hypothermia can produce ECG signs that simulate those of acute myocardial ischemia or myocardial infarction. Hypothermia can also blunt the expected ECG findings associated with hyperkalemia. A thorough knowledge of these findings is important for prompt diagnosis and treatment of hypothermia. Six cases are presented that show these important ECG manifestations of hypothermia.