Electrocardiography cannot reliably differentiate transient left ventricular apical ballooning syndrome from anterior ST-segment elevation myocardial infarction

Objective

The presentation and electrocardiographic (ECG) characteristics of transient left ventricular apical ballooning syndrome (TLVABS) can be similar to that of anterior ST-segment elevation myocardial infarction (STEMI). We tested the hypothesis that the ECG on presentation could reliably differentiate these syndromes.

Subjects and Methods

Between January 1, 2002 and July 31, 2004, we identified 18 consecutive patients with TLVABS who were matched with 36 subjects presenting with acute anterior STEMI due to atherothrombotic left anterior descending coronary artery occlusion.

Results

All patients with TLVABS were women (mean age, 72.0 ± 13.1 years). The heart rate, PR interval, QRS duration, and corrected QT interval were similar between groups. Distribution of ST elevation was similar, but patients with anterior STEMI exhibited greater ST elevation. Regressive partitioning analysis indicated that the combination of ST elevation in lead V₂ of less than 1.75 mm and ST-segment elevation in lead V₃ of less than 2.5 mm was a suggestive predictor of TLVABS (sensitivity, 67%; specificity, 94%). Conditional logistic regression indicated that the formula: (3 × ST-elevation lead V₂) + (ST-elevation V₃) + (2 × ST-elevation V₅) allowed possible discrimination between TLVABS and anterior STEMI with an optimal cutoff level of less than 11.5 mm for TLVABS (sensitivity, 94%; specificity, 72%). Patients with TLVABS were less likely to have concurrent ST-segment depression (6% vs 44%; P = .003).

Conclusions

Women presenting with TLVABS have similar ECG findings to patients with anterior infarct but with less-prominent ST-segment elevation in the anterior precordial ECG leads. These ECG findings are relatively subtle and do not have sufficient predictive value to allow reliable emergency differentiation of these syndromes.     

Optimizing the 12-lead electrocardiogram: a data driven approach to locating alternative recording sites

Background

Despite its widespread use, the limitations of the 12-lead electrocardiogram (ECG) are undisputed. The main deficiency is that just a small area of the precordium is interrogated and for some abnormalities information may be transmitted to a region of the body surface where information is not recorded. In this study, we attempted to optimize the 12-lead ECG by using a data-driven approach to suggest alternate recording sites.

Methods

A sequential lead selection algorithm was applied to a set of 744 body surface potential maps (BSPMs), consisting of recordings from subjects with myocardial infarction, left ventricular hypertrophy, and no apparent disease. A number of scenarios were investigated in which pairs of precordial leads were repositioned; these pairs were V₃ and V₅, V₄ and V₅, and V₄ and V₆. The algorithm was also used to find optimal positions for all 6 precordial leads.

Result

Through estimation of entire surface potential distributions it was found that each of the scenarios, with 2 leads repositioned, captured more information than the standard 12-lead ECG. The scenario with V₄ and V₆ repositioned performed best with a root mean square error of 22.3 microvolts and a correlation coefficient of 0.967. This configuration also fared favorably when compared to the scenario where all 6 precordial leads were repositioned as optimizing all 6 leads offered no significant improvement.

Conclusion

This study demonstrated the use of a lead selection algorithm in enhancing the 12-lead ECG. The results also indicated that repositioning just 2 precordial leads can provide the same level of information capture as that observed when all precordial leads are optimally placed.     

Total occlusion of the left main coronary artery presenting as ST-elevation myocardial infarction

An ECG pattern of widespread ST depression in six or more precordial and inferior leads, accompanied by ST-segment elevation in the aVR and/or V₁ leads, is typical of the non-ST-segment elevation myocardial infarction (NSTEMI) pattern associated left main (LM) artery occlusion, but this ECG pattern is really associated with a subocclusion of the LM, or in the case that the LM was occluded with the presence of collateral circulation. There are few reports of ST-elevation myocardial infarction (STEMI) due to acute total LM occlusion. We report a case of STEMI pattern due to acute total LM occlusion.     

A quantitative evaluation of ST-segment changes on the 18-lead electrocardiogram during acute coronary occlusions

This study determined quantitative ST segment changes on the 18-lead electrocardiogram (ECG) during occlusions in each of the coronary arteries.

Methods

Continuous 18-lead ECGs, including standard 12 leads, posterior (V_7-9), and right ventricular (RV) leads (V_3-5R) were recorded for 155 subjects undergoing percutaneous coronary occlusions, the maximum intervention.

Results

During 58 left anterior descending (LAD) coronary occlusions, the maximum ST elevation and depression were in V₃ (4.2mm) and III (−0.9mm), respectively. During 44 right coronary artery (RCA) occlusions, the maximum ST elevation and depression were in III (2.2mm) and aVL (−1.4mm), respectively. During 53 left circumflex (LCX) occlusions, the maximum ST elevation and depression were in V₇ (0.8mm) and V₂ (−1.6mm), respectively.

Conclusions

ST elevation often occurred in the anteroapical (V₁-V₆), lateral (I, aVL), and RV lead V_3R during LAD occlusions; in the inferior, RV, and posterior leads during RCA occlusions; and in the posterior, inferior, and apical leads (V₅-V₆) during LCX occlusions.     

Addition of right-sided and posterior precordial leads during stress testing

Background

Exercise treadmill testing has limited sensitivity for the detection of coronary artery disease, frequently requiring the addition of imaging modalities to enhance the predictive value of the test. Recently, there has been interest in using nonstandard electrocardiographic (ECG) leads during exercise testing.

Methods

We consecutively enrolled all patients undergoing exercise myocardial imaging with four additional leads recorded (V₄R, V₇, V₈, and V₉). The test characteristics of the 12-lead, the 15-lead (12-lead, V₇, V₈, V₉), and the 16-lead (12-lead, V₄R, V₇, V₈, V₉) ECGs were compared with stress imaging in all patients. In the subset of patients who underwent angiography within 60 days of stress testing, these lead arrays were compared with the catheterization findings.

Results

There were 727 subjects who met entry criteria. The mean age was 58.5 ± 12.3 years, and 366 (50.3%) were women. Pretest probability for disease was high in 241 (33.1%), intermediate in 347 (47.7%), and low in 139 (19.1%). A total of 166 subjects had an abnormal 12-lead ECG during exercise. The addition of 3 posterior leads to the standard 12-lead ECG resulted in 7 additional subjects having an abnormal electrocardiographic response to exercise. The addition of V₄R resulted in only 1 additional patient having an abnormal ECG during exercise. The sensitivity of the ECG for detecting ischemia as determined by stress imaging was 36.6%, 39.2%, and 40.0% (P = NS) for the 12-lead, 15-lead, and 16-lead ECGs, respectively. In those with catheterization data (n = 123), the sensitivity for determining obstructive coronary artery disease was 43.5%, 45.2%, and 45.2% (P = NS) for the 12-lead, 15-lead, and 16-lead ECGs, respectively. The sensitivity of imaging modalities was 77.4% when compared with catheterization.

Conclusions

In patients undergoing stress imaging studies, the addition of right-sided and posterior leads did not significantly increase the sensitivity of the ECG for the detection of myocardial ischemia. Additional leads should not be used to replace imaging modalities for the detection of coronary artery disease.     

The relationship between initial ST-segment deviation and final QRS complex changes related to the posterolateral wall in acute inferior myocardial infarction

Objectives

The aim of this study was to assess the relationship between initial ST-segment deviation and final QRS complex changes related to the posterolateral left ventricular wall in patients with acute inferior myocardial infarction receiving reperfusion therapy. The secondary aim was to determine if this relationship is stronger for patients who present early in the ischemia/infarction process in comparison with patients who present late.

Methods

The ST-segment depression in the leads V₁, V2, and −V6 were measured in the electrocardiograph (ECG) just before initiation of myocardial reperfusion. These leads were chosen because they represent the posterolateral wall in the Selvester score. In addition, the Anderson-Wilkins acuteness score was calculated in the admission ECG. Selvester criteria related to the posterolateral wall were identified in the ECG performed before hospital discharge to assess final infarct size.

Results

Fifty-six patients were included in this study. No significant relationship was found between the sum of initial ST-segment depression in the leads V₁, V₂, and −V₆, and final infarct size in the posterolateral left ventricular wall for the total study population (r = 0.19, P = .16). Patients were subgrouped by Anderson-Wilkins acuteness score of less than 3 vs 3 or more. In those with a low acuteness score, the amount of ST-segment depression had no relationship with final infarct size (r = −0.16, P = .41). However, the correlation was statistically significant for those with a high acuteness score (r = 0.42, P = .04).

Conclusion

The initial ST-segment depression in leads V₁, V₂, and −V₆ can predict ECG-estimated amount of infarction in the posterolateral left ventricular wall in patients with acute inferior myocardial infarction receiving reperfusion therapy, but only in those who present early in the ischemia/infarction process.     

Determinants of ST-segment level in lead aVR in anterior wall acute myocardial infarction with ST-segment elevation

Background

This study aimed to clarify the determinants of ST-segment level in lead aVR in anterior wall acute myocardial infarction (AAMI).

Methods

We analyzed ST-segment levels in all 12 leads on admission and emergency coronary angiographic findings in 261 patients with a first AAMI with ST-segment elevation. The length of the left anterior descending coronary artery (LAD) was classified as follows: short = not reaching the apex; medium = perfusing less than 25% of the inferior wall; long = perfusing 25% or more of the inferior wall.

Results

The ST-segment level in lead aVR correlated significantly with the ST-segment levels in leads I, II, III, aVF, V₁, and V_3-6, especially with those in leads II and V₆ (r = −0.63, P < .001; r = −0.61, P < .001; respectively). Patients with a proximal LAD occlusion had a greater ST-segment level in lead aVR than those with a distal LAD occlusion (P < .001). Patients with a long LAD had a lower ST-segment level than those with a short or medium LAD (P < .05).

Conclusions

The ST-segment levels, especially in leads II and V₆, the site of the LAD occlusion, and the length of the LAD affect the ST-segment level in lead aVR in ST-segment elevation AAMI.     

Type 1 electrocardiographic burden is increased in symptomatic patients with Brugada syndrome

Background

Spontaneous type 1 electrocardiographic (ECG) is a risk factor for arrhythmic events in Brugada patients but the importance of the proportion of time with a type 1 ECG is unknown.

Patients and Methods

Thirty-four Brugada patients (15 symptomatic) underwent a 24-hour 12-lead ECG recording. One-minute averaged waveforms displaying ST-segment elevation above 200 μV, with descending ST-segment and negative T-wave polarity on leads V₁-V₃ were considered as type 1 Brugada ECG. The burden was defined as the percentage of type 1 Brugada waveforms.

Results

Type 1 ECG on lead V2 was more frequent in symptomatic patients (median 80.6% [15.7-96.7] vs 12.4% [0.0-69.7], P = .05). Patients with a permanent type 1 pattern on lead V₂ were more likely to be symptomatic (5/6) than patients without type 1 ECG during a 24-hour period (2/9) (P < .05).

Conclusion

Type 1 pattern is more prevalent across a 24-hour period in symptomatic Brugada patients.     

Spontaneous onset of ventricular fibrillation in Brugada syndrome with J wave and ST-segment elevation in the inferior leads.

We report the case of a 52-year-old man with variant Brugada syndrome who was successfully resuscitated from ventricular fibrillation (VF). Resting ECG showed J wave and ST-segment elevation in the inferior leads but no coved or saddleback ST-segment elevation in the right precordial leads. Pilsicainide infusion provoked coved-type ST-segment elevation in the right precordial leads and mild ST-segment elevation 80 ms after the J point in the inferior leads. During an emergency, 12-lead ECG showed that spontaneous onset of VF was preceded by left bundle branch block and superior axis-type ventricular extrasystoles. The present case provides additional information on the site of origin of VF in patients with Brugada syndrome.     

Clinical and angiographic characteristics of patients with combined anterior and inferior ST-segment elevation on the initial electrocardiogram during acute myocardial infarction

Objective

We evaluated the significance of combined anterior and inferior ST-segment elevation on the initial electrocardiogram (EKG) in patients with acute myocardial infarction (AMI) and correlated it with AMI size and left ventricular (LV) function.

Methods

We analyzed admission EKGs of 2996 patients with AMI from the GUSTO-I angiographic substudy and the GUSTO-IIb angioplasty substudy who underwent immediate angiography. In all, we identified 1046 patients with anterior ST elevation (ST-segment elevation in ≥2 of leads V₁-V₄) and divided them into 3 groups: Group 1, anterior + inferior ST elevation (ST elevation in ≥2 of leads II, III, aVF, n =179); Group 2, anterior ST elevation only (<2 of leads II, III, aVF with ST elevation or depression, n = 447); Group 3, anterior ST elevation + superior ST elevation (ST depression in ≥2 of leads II, III, aVF, n = 420).

Results

Cardiac risk factors, prior AMI, prior percutaneous transluminal coronary angioplasty or coronary artery bypass graft, Killip class, and thrombolytic therapy assignment did not differ among the 3 groups. Group 1 patients had greater number of leads with ST elevation compared to Groups 2 and 3 (ST elevation in ≥6 leads 83% vs 22% vs 49%, P = .001). Despite greater ST-segment elevation, Group 1 patients had a lower peak CK level (median baseline peak CK 1370 vs 1670 vs 2381 IU, P = .0001) and less LV dysfunction (median ejection fraction 0.53 vs 0.49 vs 0.45, P = .0001; median number of abnormal chords 21 vs 32 vs 40, P = .0001). Angiographically, Group 1 had 2 distinct subsets of patients with either right coronary artery (RCA) (59%) or left anterior descending coronary artery (LAD) (36%) occlusion. In contrast, the infarct-related artery (IRA) was almost entirely the LAD in Groups 2 and 3 (97%). Further, the site of IRA occlusion in Group 1 was mostly proximal RCA (67%) in the RCA subgroup and mid or distal LAD (70%) in the LAD subgroup. ST-segment elevation in lead V₁ ≥ V₃ and absence of progression of ST elevation from lead V₁ to V₃ on the EKG differentiated IRA-RCA from IRA-LAD in patients with combined anterior and inferior ST elevation.

Conclusions

The AMI size and LV dysfunction in patients with anterior ST elevation is directly related to the direction of ST segment deviation in the leads II, III, aVF; least with inferior ST elevation, intermediate with no ST deviation, and maximal with superior ST elevation (inferior ST depression). Despite greater ST-segment elevation, patients with combined anterior and inferior ST elevation have limited AMI size and preserved LV function. Angiographically, they comprise 2 distinct subsets with either proximal RCA or mid to distal LAD occlusion. A predominant right ventricular and limited inferior LV AMI from a proximal RCA occlusion, or a smaller anterior AMI from a more distal occlusion of LAD may explain their limited AMI size despite greater ST elevation.     

Simulation of anteroseptal myocardial infarction by electrocardiographic filters

Background

Most electrocardiographs have high-pass filters that may be used to attenuate baseline wander due to respiratory artifact. However, the T wave also has low-frequency components and may be distorted by these filters. Our aim was to investigate the effect of high-pass filters on the ST segment.

Methods

Twenty healthy volunteers had a standard 12-lead electrocardiogram recorded using a Bard EP Labsystem (Bard Inc, Lowell, Mass) at different high-pass filter settings (0.05, 0.1, 0.5, and 1.0 Hz). ST-segment elevation or depression was measured using digital calipers at each setting and the electrocardiogram classified as being either normal or suggestive of myocardial infarction.

Results

There were no significant differences in ST elevation between 0.05- and 0.1-Hz filter settings. However, at 0.5 and 1.0 Hz, there was significant ST elevation in the right precordial leads and ST depression in the inferior leads. The greatest changes were observed in V₂, with an ST elevation of 0.13 ± 0.08 and 0.18 ± 0.09 mV at 0.5 and 1.0 Hz, respectively (P < .0001 compared with 0.05 Hz). All tracings were considered normal at 0.05- and 0.1-Hz filter settings. However, at 0.5 and 1.0 Hz, 60% and 100%, respectively, of tracings were suggestive of anteroseptal myocardial infarction. Signal distortion was attributed to phase nonlinearities of the filters.

Conclusions

High-pass filters may distort the ST segment and simulate anteroseptal myocardial infarction. These filters should comply with current standards if used on electrocardiographs and be used with caution. In case of doubt, the tracings should be compared with minimally filtered recordings.     

Best leads in the standard electrocardiogram for the emergency detection of acute coronary syndrome

Background and Purpose

The purpose of this study was to determine which leads in the standard 12-lead electrocardiogram (ECG) are the best for detecting acute coronary syndrome (ACS) among chest pain patients in the emergency department.

Methods

Neural network classifiers were used to determine the predictive capability of individual leads and combinations of leads from 862 ECGs from chest pain patients in the emergency department at Lund University Hospital.

Results

The best individual lead was aVL, with an area under the receiver operating characteristic curve of 75.5%. The best 3-lead combination was III, aVL, and V₂, with a receiver operating characteristic area of 82.0%, compared with the 12-lead ECG performance of 80.5%.

Conclusions

Our results indicate that leads III, aVL, and V2 are sufficient for computerized prediction of ACS. The present results are likely important in situations where the 12-lead ECG is impractical and for the creation of clinical decision support systems for ECG prediction of ACS.     

Referral of patients with ST-segment elevation acute myocardial infarction directly to the catheterization suite based on prehospital teletransmission of 12-lead electrocardiogram

Background

Time from symptom onset to reperfusion is essential in patients with ST-segment elevation acute myocardial infarction. Prior studies have indicated that prehospital 12-lead electrocardiogram (ECG) transmission can reduce time to reperfusion.

Purpose

Determine 12-lead ECG transmission success rates, and time saved by referring patients directly to primary percutaneous coronary intervention (pPCI) bypassing local hospitals and emergency departments.

Methods

Prehospital 12-lead ECG was recorded in patients with symptoms suggesting acute coronary syndrome during a 1-year pilot phase and transmitted to the attending cardiologist's mobile phone. Transmission success rates were determined, and prehospital and hospital delays were recorded and compared to historic controls.

Results

Transmission was attempted in 152 patients and was successful in 89%. Twenty-seven patients were referred directly for pPCI. Median hospital arrival to pPCI was 22 vs 94 minutes in the control group (P < .01).

Conclusions

Transmission of prehospital ECG is technically feasible and reduces time to pPCI in ST-segment elevation acute myocardial infarction patients.     

Where do derived precordial leads fail?

A 12-lead electrocardiogram (ECG) reconstructed from a reduced subset of leads is desired in continued arrhythmia and ST monitoring for less tangled wires and increased patient comfort. However, the impact of reconstructed 12-lead lead ECG on clinical ECG diagnosis has not been studied thoroughly. This study compares the differences between recorded and reconstructed 12-lead diagnostic ECG interpretation with 2 commonly used configurations: reconstruct precordial leads V₂, V₃, V₅, and V₆ from V₁,V₄, or reconstruct V₁, V₃, V₄, and V₆ from V₂,V₅. Limb leads are recorded in both configurations.A total of 1785 ECGs were randomly selected from a large database of 50000 ECGs consecutively collected from 2 teaching hospitals. ECGs with extreme artifact and paced rhythm were excluded. Manual ECG annotations by 2 cardiologists were categorized and used in testing. The Philips resting 12-lead ECG algorithm was used to generate computer measurements and interpretations for comparison. Results were compared for both arrhythmia and morphology categories with high prevalence interpretations including atrial fibrillation, anterior myocardial infarct, right bundle-branch block, left bundle-branch block, left atrial enlargement, and left ventricular hypertrophy. Sensitivity and specificity were calculated for each reconstruction configuration in these arrhythmia and morphology categories.Compared to recorded 12-leads, the V₂,V₅ lead configuration shows weakness in interpretations where V₁ is important such as atrial arrhythmia, atrial enlargement, and bundle-branch blocks. The V₁,V₄ lead configuration shows a decreased sensitivity in detection of anterior myocardial infarct, left bundle-branch block (LBBB), and left ventricular hypertrophy (LVH).In conclusion, reconstructed precordial leads are not equivalent to recorded leads for clinical ECG diagnoses especially in ECGs presenting rhythm and morphology abnormalities. In addition, significant accuracy reduction in ECG interpretation is not strongly correlated with waveform differences between reconstructed and recorded 12-lead ECGs.     

Electrocardiographic patterns of proximal left anterior descending artery occlusion in ST-elevation myocardial infarction may be modified by 3-vessel coronary artery disease

BackgroundThe electrocardiographic (ECG) pattern of ST-segment deviation in myocardial infarction is integral to the proper assessment of the location, extent, and functional significance of the infarct but may be modified by the underlying coronary artery anatomy.MethodsWe describe the ECG findings in 2 cases of proximal left anterior descending (LAD) artery occlusion in ST-elevation myocardial infarction (STEMI) associated with 3-vessel coronary artery disease.ResultsBoth patients had atypical ECG patterns of ST-segment elevation in leads V₂, I, and aVL and ST-segment depression with positive T waves suggestive of extensive subendocardial ischemia in leads II, III, aVF, and V₃ through V₆; acute proximal LAD occlusion and concomitant 3-vessel coronary artery disease were observed angiographically.ConclusionElectrocardiographic changes in proximal LAD STEMI may be modified by the presence of significant atherosclerotic disease elsewhere in the coronary vasculature. Recognition of this ECG pattern may aid the clinician in the rapid identification of high-risk STEMI.     

New Electrocardiographic Criteria to Differentiate Acute Pericarditis and Myocardial Infarction

Objective

Transmural myocardial ischemia induces changes in QRS complex and QT interval duration but, theoretically, these changes might not occur in acute pericarditis provided that the injury is not transmural. This study aims to assess whether QRS and QT duration permit distinguishing acute pericarditis and acute transmural myocardial ischemia.

Methods

Clinical records and 12-lead electrocardiogram (ECG) at ×2 magnification were analyzed in 79 patients with acute pericarditis and in 71 with acute ST-segment elevation myocardial infarction (STEMI).

Results

ECG leads with maximal ST-segment elevation showed longer QRS complex and shorter QT interval than leads with isoelectric ST segment in patients with STEMI (QRS: 85.9 ± 13.6 ms vs 81.3 ± 10.4 ms, P = .01; QT: 364.4 ± 38.6 vs 370.9 ± 37.0 ms, P = .04), but not in patients with pericarditis (QRS: 81.5 ± 12.5 ms vs 81.0 ± 7.9 ms, P = .69; QT: 347.9 ± 32.4 vs 347.3 ± 35.1 ms, P = .83). QT interval dispersion among the 12-ECG leads was greater in STEMI than in patients with pericarditis (69.8 ± 20.8 ms vs 50.6 ± 20.2 ms, P <.001). The diagnostic yield of classical ECG criteria (PR deviation and J point level in lead aVR and the number of leads with ST-segment elevation, ST-segment depression, and PR-segment depression) increased significantly (P = .012) when the QRS and QT changes were added to the diagnostic algorithm.

Conclusions

Patients with acute STEMI, but not those with acute pericarditis, show prolongation of QRS complex and shortening of QT interval in ECG leads with ST-segment elevation. These new findings may improve the differential diagnostic yield of the classical ECG criteria.     

ST-segment depression in aVR as a predictor of culprit artery and infarct size in acute inferior wall ST-segment elevation myocardial infarction

Background

ST-segment depression in lead aVR in acute inferior wall ST-segment elevation myocardial infarction (STEMI) has recently been suggested as a predictor of left circumflex (LCx) artery involvement. The purpose of this study is to evaluate the clinical significance of aVR depression during inferior wall STEMI.

Methods

This study included 106 consecutive patients who presented with inferior wall STEMI and underwent urgent coronary angiogram. Clinical and angiographic findings were compared between patients with and without aVR depression ≥0.1 mV.

Results

The sensitivity and specificity of aVR depression as a predictor of LCx infarction were 53% and 86%, respectively. In patients with right coronary artery infarction, aVR depression was associated with increased cardiac enzymes and the involvement of a large posterolateral branch, which may explain the larger infarction.

Conclusions

ST-segment depression in lead aVR in inferior wall STEMI predicts LCx infarction or larger RCA infarction involving a large posterolateral branch.     

Mirror image electrocardiograms and additional electrocardiographic leads: new wine in old wineskins?

Background

Mirror image electrocardiograms (ECGs), obtained by inverting the original signals, and additional precordial leads have been proposed as means to improve ECG diagnosis. The theoretical backgrounds of these proposals are discussed.

Methods

In 746 body surface potential maps, the mirror areas of the 6 precordial leads, V₃R, and 2 more leads higher up and 1 lower down the thorax have been determined. The similarity between the original signal and its mirror image was expressed by a similarity index. This was done separately for QRS and ST-T; for the first and second parts of QRS; and for the categories normal, left ventricular hypertrophy, and infarct.

Results

In general, high similarity scores were obtained. The mirror images of V₁ and V₂ are almost diametrically located on the back. Inverting these leads could render the V₈ and V₉ leads. The other mirror areas may deviate considerably from where generally expected.

Conclusion

Mirror images can be obtained consistently from all locations, supporting the dipole representation of cardiac electrical activity. Neither mirror image ECGs nor additional chest leads contribute essentially to ECG diagnosis.     

Pitfalls in diagnosing ST elevation among patients with acute myocardial infarction

Objectives: Patients with ST elevation (STE) in ≥ 2 leads or ST depression (STD) confined to V₁–V₄ are defined as potential STE myocardial infarction (STEMI). We evaluated the incidence of missed STEMI over an 11-month period. Methods: Consecutive patients with a discharge diagnosis of non STEMI were retrospectively evaluated. Clinical data, ECG and angiographic data were reviewed. Results: Of the 198 patients screened, 140 were included. Forty-nine patients (35%) met the STEMI criteria: 6 (12%) had STD confined to V₁–V₃, 20 (41%) had STD in V₁–V₆, 7 (14%) had STE in V₁–V₃, 2 (4%) had STE in I and aVL, 11 (22%) had STE in inferior leads, and 6 (12%) had STE in V₄–V₆. Conclusions: A significant percentage of patients met STEMI ECG criteria. A large number of patients with STD in V₁–V₆ had angiographic evidence compatible with inferolateral (posterior) STEMI equivalent.     

Value of Posterior and Right Ventricular Leads in Comparison to the Standard 12-Lead Electrocardiogram in Evaluation of ST-Segment Elevation in Suspected Acute Myocardial Infarction

In this multicenter prospective trial, we studied posterior (V₇ to V₉) and right ventricular (V₄R to V₆R) leads to assess their accuracy compared with standard 12-lead electrocardiograms (ECGs) for the diagnosis of acute myocardial infarction (AMI). Patients aged >34 years with suspected AMI received posterior and right ventricular leads immediately after the initial 12-lead ECG. ST elevation of 0.1 mV in 2 leads was blindly determined and inter-rater reliability estimated. AMI was diagnosed by World Health Organization criteria. The diagnostic value of nonstandard leads was determined when 12-lead ST elevation was absent and present and multivariate stepwise regression analysis was also performed. Of 533 study patients, 64.7% (345 of 533) had AMI and 24.8% received thrombolytic therapy. Posterior and right ventricular leads increased sensitivity for AMI by 8.4% (

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) but decreased specificity by 7.0% (

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). The likelihood ratios of a positive test for 12, 12 + posterior, and 12 + right ventricular ECGs were 6.4, 5.6, and 4.5, respectively. Increased AMI rates (positive predictive values) were found when ST elevation was present on 6 nonstandard leads (69.1%), on 12 leads only (88.4%), and on both 6 and 12 leads (96.8%; p <0.001). Treatment rates with thrombolytic therapy increased in parallel with this electrocardiographic gradient. Logistic regression analysis showed that 4 leads were independently predictive of AMI (p <0.001): leads I, II, V₃, V₅R; V₉ approached statistical significance (

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). The standard ECG is not optimal for detecting ST-segment elevation in AMI, but its accuracy is only modestly improved by the addition of posterior and right ventricular leads.In this multicenter prospective trial, 0.1 mV of ST-segment elevation in posterior (V₇ to V₉) and right ventricular (V₄R to V₆R) leads was found to increase the sensitivity of the electrocardiogram for acute myocardial infarction by 8.4% (

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), but decrease specificity by 7.0% (

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); logistic regression analysis showed that 4 leads were predictive of AMI at p <0.001: I, II, V₃, V₅; V₉ approached statistical significance (

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). The standard electrocardiogram is not optimal for detecting ST elevation in acute myocardial infarction, but its accuracy is only modestly improved by the addition of posterior and right ventricular leads.