Wide QRS complex tachycardia: ECG differential diagnosis.

Wide QRS complex tachycardias (WCT) present significant diagnostic and therapeutic challenges to the emergency physician. WCT may represent a supraventricular tachycardia with aberrant ventricular conduction; alternatively, such a rhythm presentation may be caused by ventricular tachycardia. Other clinical syndromes may also demonstrate WCT, such as tricyclic antidepressant toxicity and hyperkalemia. Patient age and history may assist in rhythm diagnosis, especially when coupled with electrocardiographic (ECG) evidence. Numerous ECG features have been suggested as potential clues to origin of the WCT, including ventricular rate, frontal axis, QRS complex width, and QRS morphology, as well as the presence of other characteristics such as atrioventricular dissociation and fusion/capture beats. Differentiation between ventricular tachycardia and supraventricular tachycardia with aberrant conduction frequently is difficult despite this clinical and electrocardiographic information, particularly in the early stages of evaluation with an unstable patient. When the rhythm diagnosis is in question, resuscitative therapy should be directed toward ventricular tachycardia.     

Derivation of the 12-lead electrocardiogram and 3-lead vectorcardiogram

Objective

The cardiac dipolar field is represented by the measured 12-lead electrocardiogram (ECG) and 3-lead vectorcardiogram (VCG). The objective is to derive the 12-lead ECG and 3-lead VCG from 3 measured leads acquired from only 5 electrodes.

Methods

This is a retrospective blinded study comparing measured and derived ECG and VCG tracings. A nonlinear optimization model was used to synthesize the derived 12-lead ECG and 3-lead derived VCG from leads I, II, and V₂. A total of 367 measured 12-lead electrocardiograms and 3-lead vectorcardiograms of varying morphologies were acquired from archived digital ECG databases. All tracings were interpreted by 2 blinded physician reference standards. The derived vs measured tracings were compared quantitatively using Pearson correlation and root mean square error. Qualitative comparisons were determined by physician percent agreement analysis and adjudication.

Results

The correlations between the measured and derived ECGs and VCGs were high (r = 0.867). No clinically significant differences were noted in 98.1% of cases. Electrocardiographic rate, rhythm, segment, axis, and acute myocardial infarction interpretations showed 100% correlation. Root mean square error compared favorably against other synthesis techniques. Overall percent agreements for the various ECG morphologies were noted to be 98.4% to 100%.

Conclusions

The 12-lead ECG and 3-lead VCG can be derived accurately from 3 measured leads with high quantitative and qualitative correlations. These derived tracings can be acquired instantaneously and displayed in real time from a cardiac rhythm monitor. This will allow for immediate, on-demand, convenient, and cost-effective acquisition and analysis of the 12-lead ECG and 3-lead VCG in areas of acute patient care.     

Clinical and functional assessment of electric heart instability in patients with painless myocardial ischemia

Markers of electric myocardial instability were studied in 82 patients during painless episodes of coronary heart disease (CHD). Clinical examination was supplemented by 12-lead ECG, 24-hour ECG monitoring, functional tests, echocardiography, signal-averaged ECG, recording of LVP, analysis of cardiac rhythm variability, and assessment of ventricular repolarization time. It is concluded that a combination of 24-hr ECG monitoring and functional tests (veloergometer) is indispensable for diagnostics of CHD and the evaluation of the patient"s condition. Daily dynamics of myocardial ischemia and the number of its painless episodes are shown to correlate with the results of signal-averaged ECG, Q-T dispersion and LF/HF ratio. Patients with painless CHD show enhanced frequency of myocardial infarction with the Q-wave, high-grade ventricular extrasystole, and LVP coupled to disordered autonomous vegetative control of the sinus rhythm.     

Body surface mapping improves diagnosis of acute myocardial infarction in the emergency department

Traditionally, the diagnosis of acute myocardial infarction (AMI) in emergency departments is done through an assessment of history and presenting symptoms, 12-lead electrocardiogram (ECG), and cardiac biomarkers. The 12-lead ECG is not highly sensitive for detecting ECG changes, and some infarctions may be missed. Failure to identify patients in the early stages of AMI can result in failure to provide beneficial therapies. New technology, the 80-lead ECG, uses body surface mapping to provide a more comprehensive view of cardiac electrical activity. Body surface mapping has greater sensitivity in detecting AMI in the inferoposterior portions of the left ventricle and the right ventricle. Portable hardware and user-friendly software coupled with an easily applied disposable torso vest containing the electrodes produce a 12-lead ECG, 80-lead ECG, and color contour torso or flat map showing ECG changes. Recent studies support the use of 80-lead body surface mapping for detecting AMI in the emergency department.     

A compact electric potential sensor array for the acquisition and reconstruction of the 7-lead electrocardiogram without electrical charge contact with the skin

Conventional electrocardiogram (ECG) systems make use of separate electrical connections to the arms and legs. These use a 'long baseline' for the voltage reference potential which in the case of precordial ECG leads is provided using a Wilson central terminal (WCT) wiring configuration. The aims of this project were (a) to construct compact, non-invasive surface ECG sensor arrays which would operate without the need for a WCT reference, (b) to obtain high quality precordial ECGs showing fine differences in ECG detail between small adjacent areas of the chest and (c) to reconstruct, from a compact array of four sensors, ECGs which closely match to the conventional 7-lead ECG system, but without the need for multiple wires and long baselines. In this paper, we describe two sensor array configurations which have been constructed using electric potential sensors (EPSs). We show high quality precordial ECGs obtained from small areas of the surface of the chest and show the different angular vectors (leads) in the frontal cardiac plane constructed using signals from the array elements. We suggest that these ECG arrays, which are simple to apply, should prove to be a valuable tool in providing useful information about the state of the heart.     

The electrocardiogram in the primary care office

A 12-lead electrocardiogram (ECG) graphically displays the heart's electrical activity. It is the most common clinical tool for detection and diagnosis of heart disease, and is especially useful for detecting conditions related to abnormalities of cardiac rhythm. ECG should be considered in patients who have known cardiovascular disease or an increased risk for it. The responsibility for correctly interpreting an ECG lies with the physician, who should be able to recognize patient-dependent errors, operator-dependent errors, and artifact. Current ECG tracings should always be compared with previous tracings. Following a specific routine and methodical analysis of the data will ensure an accurate interpretation result. In the worst-case scenario, they can always be faxed or transmitted for inter-consultation with a more experienced reader.     

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.     

Detection of acute myocardial infarction using the 12-lead ECG plus inverted leads versus the 16-lead ECG (with additional posterior and right-sided chest electrodes)

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. CONCLUSIONS: 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.     

Prehospital 12-lead ECG diagnostic programs

Early reperfusion significantly reduces mortality and morbidity in patients with acute myocardial infarction [2-6]. Prehospital 12-lead ECG programs significantly decrease time to definitive reperfusion therapy [8-13]. The feasibility and safety of prehospital 12-lead ECG programs are well [figure: see text] established [8,11,13,14]. Additional potential benefits include increased diagnostic accuracy in the prehospital setting [14], providing a comparison ECG to the one obtained in-hospital [15], differentiating arrhythmias [16-18], and sensitive and specific computerized ECG interpretation [31,32]. Prehospital 12-lead ECG diagnostic programs also provide the necessary clinical information to implement system changes or interventions such as prehospital thrombolytic therapy, direct CCU admission, or triage to tertiary cardiac care centers [22,30,34,35]. The information acquired should be used optimally to effect significant improvements in patient care through a well planned and coordinated program.     

Body surface mapping vs 12-lead electrocardiography to detect ST-elevation myocardial infarction

A prospective, multicenter trial was conducted in patients with nontraumatic chest pain in 4 hospitals to determine whether an 80-lead body surface map electrocardiogram system (80-lead BSM ECG) improves detection of ST-segment elevation in acute myocardial infarction (STEMI) compared with a standard 12-lead electrocardiogram (ECG) in an emergency department (ED) setting. A trained ED or cardiology staff member (technician or nurse) recorded a 12-lead ECG and 80-lead BSM ECG from each subject at initial presentation. Serial biomarkers (total creatine kinase [CK], CK-MB, and/or troponin) were obtained according to individual hospital practice. Of the 647 patients evaluated, 589 had available biomarkers results. Eighty-lead BSM ECG improved detection of biomarker-confirmed STEMI compared with the 12-lead ECG for CK-MB–defined STEMI (100% vs 72.7%, P = .031; n = 364) or troponin-defined STEMI (92.9% vs 60.7%, P = .022; n = 225). Specificity for STEMI was high (range, 94.9%-97.1%) with no significant difference between 80-lead BSM ECG and 12-lead ECG. Right ventricular involvement complicating inferior STEMI was detected by 80-lead BSM ECG in 2 (22%) of 9 patients with CK-MB–defined MI and in 2 (22%) of 9 patients with troponin-defined MI. The infarct location missed most commonly on 12-lead ECG but detected by 80-lead BSM ECG was inferoposterior MI. We conclude that BSM using 80-lead BSM ECG is more sensitive for detection of STEMI than 12-lead ECG, while retaining similar specificity.     

Limitations of Dower's Inverse Transform for the Study of Atrial Loops during Atrial Fibrillation

Introduction: Spatial characteristics of atrial fibrillatory waves have been extracted by using a vectorcardiogram (VCG) during atrial fibrillation (AF). However, the VCG is usually not recorded in clinical practice and atrial loops are derived from the 12-lead electrocardiogram (ECG). We evaluated the suitability of the reconstruction of orthogonal leads from the 12-lead ECG for fibrillatory waves in AF.
Methods: We used the Physikalisch-Technische Bundesanstalt diagnostic ECG database, which contains 15 simultaneously recorded signals (12-lead ECG and three Frank orthogonal leads) of 13 patients during AF. Frank leads were derived from the 12-lead ECG by using Dower's inverse transform. Derived leads were then compared to true Frank leads in terms of the relative error achieved. We calculated the orientation of AF loops of both recorded orthogonal leads and derived leads and measured the difference in estimated orientation. Also, we investigated the relationship of errors in derivation with fibrillatory wave amplitude, frequency, wave residuum, and fit to a plane of the AF loops.
Results: Errors in derivation of AF loops were 68 ± 31% and errors in the estimation of orientation were 35.85 ± 20.43°. We did not find any correlation among these errors and amplitude, frequency, or other parameters.
Conclusions: In conclusion, Dower's inverse transform should not be used for the derivation of orthogonal leads from the 12-lead ECG for the analysis of fibrillatory wave loops in AF. Spatial parameters obtained after this derivation may differ from those obtained from recorded orthogonal leads.     

Pre-excited atrial fibrillation triggered by intravenous adenosine: a commonly used drug with potentially life-threatening adverse effects

Although serious adverse events following adenosine administration are rare, it should only be administered in an environment where continuous ECG monitoring and emergency resuscitation equipment are available. The case report describes the development of pre-excited atrial fibrillation in a 31-year-old woman with Wolff-Parkinson-White syndrome following the administration of adenosine. She had previously been fit and well and was admitted to the coronary care unit with a 2 h history of regular palpitations. A 12-lead ECG showed a narrow QRS complex tachycardia. Carotid sinus massage was unsuccessful in terminating the tachycardia and the patient subsequently received rapid boluses of intravenous adenosine. The cardiac rhythm degenerated into atrial fibrillation with ventricular pre-excitation following 12 mg adenosine.     

Pseudo pacemaker stimuli

Current electrocardiographic technology is limited in its ability to detect pacemaker stimuli secondary to the use of 150 Hz low-pass bandwidth filters designed to block high-frequency interference. Software solutions to improve the sensitivity of pacemaker stimulus detection are associated with imperfect specificity. The following case reports include three patients who do not have a pacing device, but were identified by a computer-based preliminary interpretation of a routine 12-lead surface electrocardiogram (ECG) as having a paced rhythm.     

Wide-complex tachycardia: beyond the traditional differential diagnosis of ventricular tachycardia vs supraventricular tachycardia with aberrant conduction

Wide-complex tachycardia (WCT) is defined as a rhythm disturbance with a rate greater than 100 beats/min and a QRS complex duration of 0.12 seconds or more in the adult patient; in the pediatric patient, both rate and QRS complex width are age related. In evaluating this type of tachycardia, there are 2 broad categories usually discussed in the medical literature: ventricular and supraventricular with aberrant intraventricular conduction. There are several other important causes of a WCT encountered in clinical practice, which are less often discussed; these tachycardias often require specific therapies differing from the standard approach to WCT. These tachycardias are diverse; as such, the pathophysiology behind each form of WCT includes toxic, metabolic, and conduction system dysfunction mechanisms.     

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.     

Localization of accessory pathways in the Wolff-Parkinson-White pattern--physician versus computer interpretation of the same algorithm

BACKGROUND: There are several published algorithms for the prediction of accessory pathway (AP) location in the Wolff-Parkinson-White syndrome from the 12-lead electrocardiogram (ECG). Most depend on stepwise criteria, and minor disagreements between observers over QRS transition point or delta wave axis may lead to different classification of pathway location. We compared the utility of a computerized program in identifying pathway location from the ECG using the algorithm published by Fitzpatrick and coworkers(3) against physician assessment with the same algorithm. METHODS: Thirty-one 12-lead ECGs with an overt preexcitation pattern were examined by three physicians and AP localized to one of eight anatomical sites using the Fitzpatrick algorithm, with disagreements resolved by consensus. Similarly, pathway location was determined by the Glasgow ECG program with the Fitzpatrick algorithm incorporated into its logic. RESULTS: The agreement between each physician and their consensus was 28/31, 29/31, and 29/31. Similarly, assessment by the Glasgow program produced agreement with the physician consensus in 29/31 cases. Of the 24 patients who underwent radiofrequency ablation, the program localized the pathway to the true or adjacent annular region in 20, compared to 20/24 by physician assessment of the algorithm, producing a similar predictive accuracy to published data. CONCLUSION: This study has shown that incorporation of the Fitzpatrick algorithm for AP location into a widely used computer program results in the same level of performance as that of experienced physicians and may be useful in clinical practice as an aid to referral for electrophysiological study and ablation.     

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。     

Electrocardiographic applications of lead aVR

Lead aVR, 1 of 12 electrocardiographic leads, is frequently ignored in clinical medicine. In fact, many clinicians refer to the 12-lead electrocardiogram (ECG) as the 11-lead ECG, noting the commonly held belief that lead aVR rarely offers clinically useful information. In this report, we discuss the findings in lead aVR, which are potentially of value, including ST-segment elevation in the patient with acute coronary syndrome suggestive of left main coronary artery occlusion, PR-segment elevation in the patient with acute pericarditis, prominent R wave in the patient with significant tricyclic antidepressant poisoning, and ST-segment elevation in narrow complex tachycardia suggestive of Wolff-Parkinson-White syndrome.     

12-lead ECG training: the way forward

The teaching of electrocardiography (ECG) monitoring has not changed for decades and still very much relies on access to real patients for practice. However there is nowadays an even greater need for modern training tools in this field as more healthcare professionals than ever before need to be trained on 12-lead ECG monitoring techniques. For example in many parts of the UK ambulance paramedics use features observed from 12-lead ECG monitoring equipment to determine whether or not a patient can receive pre-hospital thrombolytic therapy. Because important decisions are made without the presence of a cardiologist, it is essential that the training is carried out with the most realistic tools, including tools which give realistic feedback of the consequences of incorrect electrode placement. Current mannequins for ECG training are designed with protruding electrodes on the chest, which act as cues for trainees. There is therefore a need for a realistic simulation training tool to teach 12-lead ECG interpretation which includes the ability to give this feedback. We are currently working on the development of such a training tool and it is expected that it will be of great interest to medical, nursing and paramedic schools.