The evaluation of a precordial ECG BELT: technologist satisfaction and accuracy of recording.

The standard method for performing electrocardiogram (ECG) recordings presents a challenge to technicians because of the need to correctly position the individual precordial electrodes according to 6 bony thoracic landmarks. A proposed new method using a 6-lead ECG BELT for precordial application was compared to the standard method to determine the level of agreement among automated interpretations. A comparison of automated interpretations from repeat standard recordings served as the control. Results indicate that BELT and standard automated interpretations disagreed significantly more frequently than repeat standard recording automated interpretations of the cardiac rhythm. The BELT's most obvious weakness was the inability to obtain a recording with a stable ECG baseline, triggering automated detection of "baseline artifact or wander," and requiring a repeat recording. These findings suggest that the ECG BELT is not adequate for clinical application in its current form.

Standards for the function of an academic 12-lead electrocardiographic core laboratory.

An academic 12-lead electrocardiogram (ECG) core laboratory aims to provide the highest possible quality ECG recording, measurement, and storage to aid clinicians in research into important cardiovascular outcomes and to maximize the credibility of scientific results based solely, or in part, on ECG data. This position paper presents a guide for the structure and function of an academic ECG core laboratory. The key functional aspects are: 1) Data collection, 2) Staff composition, 3) Diagnostic measurement and definition standards, 4) Data management, 5) Academic considerations, 6) Economic consideration, and 7) Accreditation. An ECG Core Laboratory has the responsibility for rapid and accurate analysis and responsible management of the electrocardiographic data in multicenter clinical trials. Academic Laboratories, in addition, provide leadership in research protocol generation and production of research manuscripts for submission to the appropriate peer-review journals.

A dynamic three-dimensional display of ventricular excitation and the generation of the vector and electrocardiogram.

Computer models, such as those produced by Solomon and Selvester, have helped increase our understanding of the heart's electrical activity. In the present report, we describe a dynamic three-dimensional computerized display of the myocardial excitation sequence that is based on this fundamental research. The display is based on the vectors of the potential differences generated in the various parts of the myocardium during its excitation. The sums of these individual vectors form composite vectors that are related to the ECG signals recorded from the body's surface. The display simultaneously portrays the temporal changes of the composite vectors in 3 dimensions and in each plane (the transverse, frontal and left sagittal). It also shows the corresponding changes in the QRS complexes in each of the 12 scalar ECG leads. The display shows the patterns of activation of the normal heart and an example of posterolateral myocardial infarction. The technique facilitates the understanding of myocardial activation and how it is modified by specific pathological conditions. It is believed that this method of presentation and visualization of the generation of the ECG will be of value in the teaching of this process.

A method for assembling a collaborative research team from multiple disciplines and academic centers to study the relationships between ECG estimation and MRI measurement of myocardial infarct size.

A method has been developed for establishing a "University Without Walls" for the purpose of studying the relationship between electrocardiographic estimation and magnetic resonance imaging measurements of myocardial infarct size. The research team includes faculty and students from 4 medical centers, with expertise extending from clinical to technical. Weekly interactive videoconferences provide the key research communication method. Study patients are recruited from 2 of the sites, and the correlations between their electrocardiographic and magnetic resonance imaging data are considered by the research team in conference. Outcomes of this program are both scientific publications in international peer-review journals and formal postdoctoral degree attainment by the research trainees.

Validation of advanced ECG diagnostic software for the detection of prior myocardial infarction by using nuclear cardiac imaging.

The investigators report the diagnostic performance of the latest version (Version 2.5) of the recently developed Cardiovise algorithm for detecting prior myocardial infarction (MI). The Cardiovise 2.5 prior MI algorithm, a component of Cardiovise Cardiac Diagnostic System (Inovise Medical, Inc, Newberg, OR), uses scalar QRS, scalar T wave, and vectorcardiographic QRS criteria for detecting, sizing, and localizing prior MI. In this study only the detection part of the algorithm's performance was evaluated, using 105 patients with and 98 patients without prior MI as indicated by the results of cardiac imaging with Sestamibi. The specificity, and sensitivity of Cardiovise 2.5 for detecting prior MI in this population of patients are 97% and 79%, respectively. The sensitivity and overall diagnostic performance of Cardiovise 2.5 was significantly better than those of a total of 6 human readers (3 cardiologists and 3 primary care physicians) and to 2 commercially available ECG diagnostic algorithms.

Importance of accounting for the variability of electrocardiographic data among diagnostically similar patients with inferior wall healed myocardial infarction.

The authors describe a method to account for patient-to-patient variability in electrocardiographic data. The method yielded criteria for healed inferior myocardial infarction with diagnostic performances better than those of traditional electrocardiographic parameters.

Validation of cardiologists' decisions to initiate reperfusion therapy for acute myocardial infarction with electrocardiograms viewed on liquid crystal displays of cellular telephones.

BACKGROUND: The transmission of 12-lead electrocardiograms from remote locations to hand-held computers of cardiologists is now possible with the development of wireless technology and computer software. This investigation determined whether the cardiologist's decisions regarding reperfusion therapy for patients with symptoms suggestive of an acute myocardial infarction are the same when given electrocardiograms displayed on a cellular telephone as on a standard paper recording. METHODS: Cardiologists were given 20 electrocardiograms of patients with acute chest pain suggestive of acute myocardial infarction to test the diagnostic reliability of the Nokia 9000i cellular telephone liquid crystal display (LCD) screen. The cardiologists made their decision to initiate or not initiate reperfusion therapy for the patients after viewing their electrocardiograms displayed on both 5-mm and 1-mm formatted grids and twice on traditional printout electrocardiograms. The control level of intraobserver agreement between the responses from the 2 sets of paper display electrocardiograms was compared with the experimental level of intraobserver agreement between the 1-mm LCD electrocardiograms and both sets of paper display electrocardiograms to determine whether the viewing medium affected the cardiologist's decisions. The 1-mm and 5-mm LCD screen electrocardiograms were compared to determine if the grid size affected the cardiologist's decisions. RESULTS: Ninety-three percent of the 2 sets of paper-guided decisions were in agreement. When comparing the 1-mm LCD-guided decisions with both sets of paper-guided decisions, 94% and 89% of the decisions, respectively, were in agreement. The differences between the control and experimental degrees of intraobserver agreement of 1% and 4% were not statistically significant (P1 =.81, P2 =.29). Ninety-one percent of the 1-mm LCD-guided decisions were in agreement with the 5-mm LCD-guided decisions. CONCLUSIONS: Cardiologists' decisions did not vary significantly when viewing either traditional paper electrocardiograms or LCD screen electrocardiograms. Even though there was not a significant difference in the cardiologists' decisions when they viewed electrocardiograms displayed on both the 1-mm and 5-mm grid, it is recommended that the 1-mm grid be used for clinical implementation of the LCD screen.

Comparison of an automated thrombolytic predictive instrument to both diagnostic software and an expert cardiologist for diagnosis of an ST elevation acute myocardial infarction.

Because the electrocardiograms (ECGs) of patients with symptoms suggesting an acute thrombotic coronary occlusion are typically read by physicians relatively inexperienced in this skill, it is important to develop automated decision support. A Thrombolytic Predictive Instrument (TPI) is now available along with the standard diagnostic software in a commercially available electrocardiograph. This study evaluates the performance of the predictive software in comparison to both an expert cardiologist and standard diagnostic software. True sensitivity and specificity cannot be determined because acute coronary angiography was not performed. The specificities determined by this study were excellent (98% and 99%), and the sensitivities were very good (72% and 78%). These results that the TPI will be only rarely applied to patients who do not indeed have an acute coronary thrombosis. However, the reasons for even this small number of presumably falsely TPI positive patients should be determined and analyzed. It is unlikely that alterations of the thresholds for TPI activation will significantly improve on this very good level of sensitivity, without prohibitively decreasing specificity.

The correlation between presenting ST-segment depression and the final size of acute myocardial infarcts in patients with acute coronary syndromes.

The use of reperfusion therapy in patients with ST elevation acute coronary syndromes had been established. However, reperfusion therapy is usually considered contra-indicated in those with ST depression, despite the knowledge that regional posterior infarction is typically indicated by ST depression maximal in leads V1 to V3 and nonregional subendocardial infarction is typically indicated by marked ST depression maximal in other leads. This study of patients with non-ST-elevation acute coronary syndromes investigates the quantitative relationship between presenting ST depression and final QRS changes in both of these subgroups. The final QRS score was significantly higher (2.44 points) than that of a control group with not ST depression, (1.55 points) in the group with maximal ST depression in V1 to V3 (P = 0.04). However, in the entire population, there was a highly significant correlation (P = .003) between the sum of the presenting ST depression and the final QRS score. Trials of reperfusion therapy will be required to determine if such evolution to electrocardiogram documented acute myocardial infarction can be prevented in patient with marked ST depression acute coronary syndromes.

Combined historical and electrocardiographic timing of acute anterior and inferior myocardial infarcts for prediction of reperfusion achievable size limitation.

The historical time of acute symptom onset is not always an accurate indication of the timing of onset of an acute myocardial infarction (AMI). Consideration of electrocardiographic (ECG) timing parameters could supplement historical timing alone as a clinical guide for decisions regarding the use of reperfusion therapy. Three hundred ninety-five patients from 4 trials of thrombolytic therapy conducted in the northwestern United States and western Canada are included in the present study. A total of 316 patients received either streptokinase or tissue plasminogen activator, and 79 received no reperfusion therapy. Historical time of symptom onset was acquired by emergency or cardiology department personnel and recorded on patient report forms. An ECG method for estimating the timing of the AMI, the Anderson-Wilkins (AW) acuteness score, was calculated from the initial standard 12-lead recording by investigators blinded to the knowledge of symptom duration or any other study variables. Tomographic thallium-201 imaging 7 weeks after hospital admission was used to measure final AMI size. The ECG timing method achieved a relation with final AMI size similar to that previously reported for historical timing. The AW acuteness score proved most useful for anterior AMI location when there was a > or = 2 hour delay following symptom onset, but was most useful for the inferior AMI location when there was a < 2 hour delay. Despite a longer delay, patients with high AW acuteness scores had 50% lower final anterior AMI size than those with low scores; and despite a shorter delay, those with low ECG acuteness scores had 50% greater final inferior AMI size than those with high scores. The AW acuteness score combined with the historical estimation of symptom duration should provide a more accurate basis for predicting the potential for limitation of final AMI size than either method alone. These results could potentially provide the basis for developing a new method for noninvasive guidance of clinical decisions regarding administration of reperfusion therapy in the initial evaluation of patients with AMI.

Significance of ST-segment depression with R-wave amplitude decrease on exercise testing.

A retrospective evaluation was performed of patients who underwent exercise tests and angiography and 50 ambulatory normal subjects who underwent only exercise testing. We found that when deltaST depression of 0.5 mm was combined with deltaR-wave decrease of 1 mm, the sensitivity and specificity were improved.

Specificity of electrocardiographic myocardial infarction screening criteria in patients with nonischemic cardiomyopathies.

BACKGROUND: The 32-point, 54-criteria Selvester QRS scoring system has been successfully used to estimate the size of nonacute myocardial infarction (MI). Three criteria of the system have been shown to be sensitive for the identification of nonacute MI and specific in normal control subjects. The validity of the system has not been tested in patients with cardiomyopathy of nonischemic origin. The purpose of this study was to examine the electrocardiographs (ECGs) of patients with abnormal left ventricular function but no presence of coronary disease to determine the diagnostic specificity of the MI screening criteria subset of the Selvester QRS scoring system. METHODS AND RESULTS: Six hundred ninety patients were considered. Exclusion criteria included age <10 years, cardiac transplantation, thrombolytic therapy, any angiographic evidence of coronary disease, left ventricular ejection fraction (LVEF) >60%, or history of myocardial revascularization. ECG exclusion criteria included left ventricular hypertrophy, right ventricular hypertrophy, left bundle branch block, right bundle branch block, ventricular pacing, left anterior fascicular block, left posterior fascicular block, ventricular preexcitation, and low voltage, because these confounding factors could mimic an infarct on the ECG. The 261 remaining patients were then examined for the presence of the MI screening criteria subset: (1) inferior location: Q > or =30 msec in aVF, (2) anterior location: either any Q or R< or =0.1 mV and < or =10 msec in V2, and (3) posterior location: R> or =40 msec in V1. Thirty-two of the 261 patients falsely met at least 1 of the 3 MI screening criteria, resulting in an overall specificity of 88% (vs 95% in normal control subjects, P=.0006). A specificity of 98% (n = 256) was achieved for the inferior MI screening criterion alone, whereas the anterior and posterior MI screening criteria alone achieved significantly lower specificities: 94% (n = 245) and 95% (n = 249), respectively. When the patient population was divided into LVEF <30% and LVEF > or =30%, no significant association was found between MI screening criteria and LVEF with specificities of 87% and 88%, respectively, for the 2 groups (P= .34). CONCLUSIONS: The MI screening criteria subset is relatively specific in patients with nonischemic cardiomyopathy, falsely identifying only 12% with nonacute MI. However, this specificity is lower than the 95% achieved in normal subjects. Regional accumulation of scarring caused by cardiomyopathy could result in false-positive indication of MI in the present population. Another possibility could be that some patients could have hypertrophy of the myocardium insufficient to produce positive ECG criteria for left ventricular hypertrophy or right ventricular hypertrophy but sufficient to mimic infarction.

Comparison of the various electrocardiographic scoring codes for estimating anatomically documented sizes of single and multiple infarcts of the left ventricle.

It is clinically important to estimate the size of a myocardial infarction (MI) to predict patient prognosis, to determine the ability of a therapy to limit its size, and to evaluate its effect on left ventricular function. Various electrocardiographic methods have been used for these purposes but their accuracies have not been compared with each other using an identical reference population of anatomically measured infarcts. The capability of 4 electrocardiographic scoring methods (the Selvester score, the Minnesota code, the Novacode, and the Cardiac Infarction Injury Score) to estimate MI size was compared using anatomic MI size in a group of 100 deceased patients. All patients had a standard 12-lead electrocardiogram of sufficient quality to perform manual waveform measurements and without confounding factors such as ventricular hypertrophy, fascicular block, or bundle branch block. The location and size of the left ventricular infarction was measured postmortem using the anatomic method of Ideker et al. All methods' size estimates correlated best with anatomic MI size in the anterior location (r = 0.65 to 0.89). The Selvester score was superior in estimating the sizes of inferior (r = 0.70) and posterolateral (r = 0.74) infarcts. For multiple infarcts all methods performed poorly (r = 0.18 to 0.44).

Patient-specific predictions of outcomes in myocardial infarction for real-time emergency use: a thrombolytic predictive instrument.

BACKGROUND: Thrombolytic therapy can be life-saving in patients with acute myocardial infarction. However, if given too late or insufficiently selectively, it may provide little benefit but still cause serious complications and incur substantial costs. OBJECTIVE: To develop a thrombolytic predictive instrument for real-time use in emergency medical service settings that could 1) identify patients likely to benefit from thrombolysis and 2) facilitate the earliest possible use of this therapy. DESIGN: Creation and validation of logistic regression-based predictive instruments based on secondary analysis of clinical data. PATIENTS: 4911 patients who had acute myocardial infarction and ST-segment elevation on electrocardiogram; 3483 received thrombolytic therapy. MEASUREMENTS: Data were obtained from 13 major clinical trials and registries and directly from medical records, including electrocardiograms obtained at presentation. Input variables include presenting clinical and electrocardiography features; predictive models generate probabilities for acute (30-day) mortality if and if not treated with thrombolysis, 1-year mortality rates if and if not treated with thrombolysis, cardiac arrest if and if not treated with thrombolysis, thrombolysis-related intracranial hemorrhage, and thrombolysis-related major bleeding episode requiring transfusion. Together, these models constitute the thrombolytic predictive instrument. RESULTS: The predictive models generated the following mean predictions for patients in the Thrombolytic Predictive instrument Database: 30-day mortality rate, 7.1%; 1-year mortality rate, 10.9%; rate of cardiac arrest, 3.7%; rate of thrombolysis-related intracranial hemorrhage. 0.6%; and rate of other thrombolysis-related major bleeding episodes, 5.0%. They discriminated with between persons having and those not having the predicted outcome; areas under the receiver-operating characteristic (ROC) curve were between 0.77 and 0.84 for the five outcomes. Calibration between each instrument's predicted and observed served rates was excellent. Validation of the predictive instruments of 30-day and 1-year mortality, done on a separate test dataset, yielded areas under the ROC curve of 0.76 for each CONCLUSIONS: After the basic features of a clinical presentation are entered into a computerized electrocardiograph, the predictions of the thrombolytic predictive instrument can be printed on the electrocardiogram report. This decision aid may facilitate earlier and more appropriate use of thrombolytic therapy in patients with acute myocardial infarction.

Relation between symptom duration before thrombolytic therapy and final myocardial infarct size.

BACKGROUND: Myocardial salvage is most likely to occur when thrombolytic therapy is administered within 4 to 6 hours of the onset of symptoms of myocardial infarction. The impact of delays within this early time period on final myocardial infarct size are unknown. The purpose of this study was to quantitate the relation between final myocardial infarct size and duration of symptoms before initiation of thrombolytic therapy in patients treated within 6 hours of symptom onset. METHODS AND RESULTS: The findings from patients in four prospective randomized trials of thrombolytic therapy were combined for analysis. The study population consisted of 432 patients presenting within 6 hours of onset of symptoms of first acute myocardial infarction who met ECG criteria that allowed estimation of myocardial area at risk before treatment with thrombolytic therapy and who had thallium-201 myocardial infarct-size measurements performed several weeks after infarction. ECG analysis revealed no difference in myocardium at risk for infarction as a function of duration of symptoms before initiation of thrombolytic therapy. In contrast, univariate and multivariate analysis showed that final infarct size was highly dependent on duration of symptoms before initiation of therapy. Each 30-minute increase in symptom duration before thrombolytic therapy was associated with an increase in infarct size of 1% of the myocardium. Final infarct size in patients treated 4 to 6 hours after symptom onset was indistinguishable from patients who did not receive thrombolytic therapy. CONCLUSIONS: These findings suggest that for patients treated within 4 to 6 hours of the onset of symptoms, there is a progressive decline in the extent of myocardium salvaged as the duration of symptoms before therapy increases. These results support efforts to minimize the time delay between symptom onset and initiation of reperfusion therapy in all eligible patients.

Asymptomatic coronary artery disease detection: update 1996. A screening protocol using 16-lead high-resolution ECG, ultrafast CT, exercise testing, and radionuclear imaging.

The authors have proposed a new four-step screening algorithm to detect asymptomatic coronary artery disease (CAD) in flight school candidates, cadets, and rated flyers of the Unites States Air Force (USAF). In step 1, the USAF Armstrong Laboratory (USAF/AL) risk profile and improved 16-lead high-resolution electrocardiogram/vectorcardiogram will be recorded at baseline. On routine follow-up evaluations, quantitative serial comparisons will be performed by the method of Kornreich. In step 2, beginning with flight school candidates and cadets, all three groups will be studied by the ultrafast computed tomograph (CT) protocol. Those candidates positive for coronary calcium will be studied by coronary angiography and ventriculography, and their eligibility for continued rated flight status will be determined by present criteria. In step 3, those candidates negative for coronary calcium by ultrafast CT will then be screened by the newly defined and improved high-sensitivity treadmill exercise test criteria. In step 4, candidates with a positive treadmill exercise test result, or who are also found in the upper quintile of the USAF/AL risk profile, wild also have exercise nuclear wall motion studies and perfusion scans. If these are abnormal and suggestive of myocardial ischemia, this subset will also be studied by heart catheterization and coronary angiography, and their eligibility for continued rated flight status will be determined by present criteria. The incidence of coronary calcium/no calcium for each degree of stenosis in the 6,000 flyers in each quintile was used to develop the following projections: (1) that more than 3 of 4 rated flyers with unsuspected CAD, and (2) more than 9 of 10 with severe flow-limiting CAD can be identified by these upgraded screening procedures. Evidence is herein presented that these enhancements will result in a major (5-8-fold) increase in case finding of this disease. Based on the estimate of four lost high-performance aircrafts per year from sudden incapacitation of the pilot due to CAD, when this four-step screen is fully operational, it can be expected to reduce the $80 million annual losses to the United States government from CAD by 85%, a savings of $68 million per year.

Estimates of myocardium at risk and collateral flow in acute myocardial infarction using electrocardiographic indexes with comparison to radionuclide and angiographic measures.

OBJECTIVES: This study sought to determine the accuracy of the initial 12-lead electrocardiogram (ECG) in predicting final infarct size after direct coronary angioplasty for myocardial infarction and to examine which physiologic variables known to be determinants of outcome the ST segment changes most closely reflect. BACKGROUND: Myocardium at risk, collateral flow and time to reperfusion have been shown to be independent physiologic predictors of infarct size in animal and clinical models. However, such measurements may be difficult to perform on a routine basis in patients with myocardial infarction. The standard 12-lead ECG is inexpensive and readily available. METHODS: Sixty-seven patients with acute myocardial infarction, ST segment elevation and duration of chest pain < 12 h had an initial injection of technetium-99m sestamibi. Tomographic imaging was performed 1 to 8 h later (after direct coronary angioplasty), and the images were quantified to measure perfusion defect size (myocardium at risk) and severity (a measure of collateral flow). Contrast agent injection and tomographic acquisition were repeated at hospital discharge to measure infarct size. The ST segment elevation score was calculated for each patient according to infarct location and using previously described formulas. RESULTS: ST segment elevation score correlated closest with the radionuclide measure of collateral flow (r = -0.44, p < or = 0.0001), as well as an angiographic measure of collateral flow (r = -0.38, p = 0.05). Although ST segment elevation score correlated weakly with the magnitude of myocardium at risk by technetium-99m sestamibi, it was not as strong as infarct location alone in predicting myocardium at risk ([mean +/- SD] anterior 51 +/- 13% left ventricle vs. inferior 17 +/- 10% left ventricle, p < 0.0001). ST segment elevation score was weakly associated with final infarct size (r = 0.34, p = 0.005). A multivariate ECG model was constructed with infarct location as a surrogate for myocardium at risk, ST segment elevation score as a surrogate for estimated collateral flow, and elapsed time to reperfusion from onset of chest pain. All three variables were independently associated with infarct size. CONCLUSIONS: The initial standard 12-lead ECG can provide insight into myocardium at risk and, to a greater extent, collateral flow and can consequently provide some estimate of subsequent infarct size. However, the confidence limits for such predictors are wide.

Evolution of electrocardiographic and echocardiographic abnormalities during the 4 years following first acute myocardial infarction.

Therapies aimed at salvaging jeopardized myocardium in patients with acute myocardial infarction (MI) are now routine. The success of these therapies must often be estimated by non-invasive tests, such as the 12-lead electrocardiogram (ECG) or two-dimensional echocardiography. To monitor QRS changes and left ventricular (LV) function over time in patients who have received therapies aimed at myocardial salvage, it is important to know the 'spontaneous' evolution of these estimates. Consecutive MI survivors admitted in the pre-thrombolytic era with their first MI were re-studied at 4 years. Patients were excluded if they had experienced reinfarction, coronary revascularization or bundle branch block in the acute or follow-up period. A standard ECG and a two-dimensional echocardiogram were obtained prior to discharge and at follow-up. The quantitative ECG analysis was performed according to the Selvester QRS scoring method. During the two-dimensional echocardiogram each of the 20 segments of the LV were assessed to provide a wall motion score. Eighty patients with a median age of 64 years (range 40-79) were included in the study. Thirty-two had anterior and 48 inferior MI. A significant decrement in median QRS score-estimated AMI size occurred between pre-discharge and follow-up ECGs in the entire group (18.3% vs 10.5%; P<0.0001). This difference occurred in both anterior (21.6% vs 10.5%; P<0.0001) and inferior-posterior (16.5 vs 10.5%; P<0.0001) MI locations. In the anterior MI group ther was a trend towards a greater total decrease of QRS points than in the inferior-posterior MI group (42% vs 27%; P=0.10). Within the anterior MI group, more QRS points awarded in the anteroseptal leads (V1-V3) remained follow-up than in the anterosuperior and apical leads (I, aVL and V4-V6), (80% vs 49%; P=0,03).

T wave amplitudes in normal populations. Variation with ECG lead, sex, and age.

Consideration of increased T wave amplitude (tall T waves), either alone or in association with other electrocardiographic (ECG) parameters, may be beneficial for the early detection of acute transmural ischemia, and quantification of the increase might be used in quantifying the ischemic area. The primary purpose of this study was to quantify normal T wave amplitude limits according to ECG lead, sex, and age. One thousand nine hundred thirty-five subjects in two normal populations were analyzed, and the 98th percentile of the positive T wave amplitude for each ECG lead (including -aVR) was considered the upper limit of normal. Normal T wave amplitude was two times greater in the precordial than in the limb leads, and it was approximately 25% greater in men than in women in all leads. There was approximately a 10% decrease in normal T wave amplitude between 18-39- and 40-59-year-old patients and a 15% decrease between 40-59- and 60-79-year-old patients. The upper limit of normal T wave amplitudes identified in this study confirm those developed by Lepeschkin for use as means for each lead when age and sex are not considered. These limits might be incorporated into both normograms and automated ECG analysis systems to determine the presence or absence of tall T waves in patients presenting with symptoms of acute transmural ischemia.