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.

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.

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.

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 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.

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.

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.

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.

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.

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).

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.

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.

Appearance of abnormal Q waves early in the course of acute myocardial infarction: implications for efficacy of thrombolytic therapy

OBJECTIVES

The purpose of this study was to determine the time course of the appearance of abnormal Q waves on the electrocardiogram (ECG) over the first 6 h of symptoms of myocardial infarction and to determine what implications, if any, such Q waves have for the efficacy of thrombolytic therapy.

BACKGROUND

Severe myocardial ischemia can produce early QRS changes in the absence of infarction. Abnormal Q waves on the baseline ECG may not be an accurate marker of irreversibly injured myocardium.

METHODS

Data from 695 patients who had no past history of myocardial infarction and whose admission ECG allowed prediction of myocardial infarct size in the absence of thrombolytic therapy (Aldrich score) were pooled from four prospective trials of thrombolytic therapy. The presence and number of abnormal Q waves on each patient's initial ECG were recorded. Four hundred thirty-six patients had left ventricular infarct size measured using quantitative thallium-201 tomography a mean (+/- SD) of 52 +/- 43 days after admission.

RESULTS

Of patients admitted within 1 h of symptoms, 53% had abnormal Q waves on the initial ECG. Both predicted and final infarct size were larger in patients with abnormal Q waves on the initial ECG independent of the duration of symptoms before therapy (p < 0.001). Despite this finding, the presence of abnormal Q waves on the admission ECG did not eliminate the effect of thrombolytic therapy on reducing final infarct size (p < 0.0001).

CONCLUSIONS

Abnormal Q waves are a common finding early in the course of acute myocardial infarction. However, there is no evidence that abnormal Q waves are associated with less benefit in terms of reduction of infarct size after thrombolytic therapy.

Panoramic display of the orderly sequenced 12-lead ECG

The standard 12-lead electrocardiogram (ECG) has been developed over many years. The ECG has had a long and successful history of providing diagnostic information in clinical medicine. Cardiac arrhythmias have been elucidated by deductive reasoning from continuous ECG recordings with confirmation from electrophysiologic studies. Recently, there has been renewed interest in the morphology of the QRS complex, ST-segment, and T wave, which raises the important question of considering whether the usual method of display provides maximal diagnostic capabilities. The conventional display provides a logical visualization of precordial lead recordings representing the horizontal plane, but does not provide a logical visualization of the limb lead recordings representing the frontal plane. Many clinical problems require the consideration of serial ECGs necessitating the comparison of separate pages. An alternate format presenting serial recordings on a single page would be advantageous. Some automated ECG analysis systems already include the capability for multiple display formats, but these have not yet been widely used in clinical practice. This point of view paper introduces a new display format for the standard 12-lead ECG that includes: (1) a presentation of an orderly sequence of leads to facilitate scanning through different points in space and (2) a presentation of recordings of 12-lead sequences to facilitate scanning through different points in time. This display format could either replace or supplement the conventional ECG format.

ECG myocardial infarct size: a gender-, age-, race-insensitive 12-segment multiple regression model. I: Retrospective learning set of 100 pathoanatomic infarcts and 229 normal control subjects

In this early study of ongoing work with multiple regression modeling for mapping myocardial infarct (MI) into 12 left ventricular (LV) segments, promising results have been presented using electrocardiographic (ECG) QRS variables that are gender, age, and race insensitive (GARI), the GARI-QRS 12-segment multiple regression model. These include Q, R, and S duration, expressed as percentage total QRS duration, and R/Q duration, R/Q amplitude, R/S duration, and R/S amplitude variables. For version I, building 12 regression models using 68 single and 32 multiple MIs, the GARI-QRS variables correlated with pathoanatomic MI in each of 12 segments with r values ranging from .67 to .88. In version II of the model, using all MIs and 229 normal subjects, r = .73-.91. Version II predictions of MI in 12 LV segments for each subject were used to calculate the predicted total percentage LV infarct, which correlated well with that found at autopsy. The r values found were .81 for all single MIs, .73 for multiple MIs, and .80 for all MIs taken together. With refinements of the input ECG variables to include (1) improvement in the GARI-QRS variables, (2) adding a significant number of subjects with hypertrophies and conduction defects with and without MI to an expanded learning set, and (3) applying the enhanced 12-LV-segment regression models to a similar test set, it is to be expected that these regression models can be improved even further in such a way as to be applicable to general clinical populations using routine computerized ECG analysis programs.

QRST changes during and after percutaneous transluminal coronary angioplasty

This study reports preliminary results on 45 patients who underwent percutaneous transluminal coronary angioplasty (PTCA); 120-lead data (including the 12-lead standard electrocardiogram [ECG]) were recorded before, during, and after balloon inflation. Twenty-one patients underwent PTCA for left anterior descending coronary disease, 13 for right coronary artery disease, and 10 for left circumflex; 1 patient had combined left anterior descending and right coronary artery disease. In each patient, voltage data recorded during the various phases of the procedure were compared with the patient's own baseline data. In 18 patients, 120 leads were also recorded 24 hours after PTCA. In this study, the usefulness of the standard 12-lead ECG was investigated in locating the coronary artery being occluded, in elucidating the mechanisms of the QRS changes, and in identifying changes occurring 24 hours after completion of the procedure. Results indicate that the observation of ST elevation in the 12-lead ECG may lead to ambiguous interpretation. Also, limiting observation to ST-T patterns alone instead of including QRS changes further hampers correct identification of the involved vessel. QRS modifications during inflation are interpreted as conduction disturbances, although other mechanisms are evoked: study of surface maps may contribute to the understanding of these mechanisms. Changes present 24 hours later are visible in the standard leads, but again, in the absence of the thoracic potential distribution, these are difficult to interpret. These changes were different from those observed after cessation of inflation at the end of the procedure. It is hypothesized that next-day changes may reflect reperfusion injury and/or represent myocardial stunning. Presence of injury and reversibility of changes require further investigation. Also, biochemical markers such as creatine kinase-MB mass, creatine kinase-MB activity, myoglobin, and troponin-T may help elucidate the significance of these findings.

Correlation of the complete version of the Selvester QRS scoring system with quantitative anatomic findings for multiple left ventricular myocardial infarcts

The correlation between myocardial infarct size estimated by the complete version of the Selvester QRS scoring system and that documented by pathoanatomic studies has been reported for single anterior, inferior and posterolateral infarcts. Although previous studies described electrocardiographic changes in patients with multiple infarcts, no quantitative documentation of the ability of such changes to estimate the total amount of left ventricular infarction has been reported. This study of 32 patients with anatomically documented multiple infarcts shows a significant correlation between QRS-estimated and anatomically documented sizes (r = 0.44; p = 0.01), which is less than that previously reported for single infarcts in the anterior, inferior and posterolateral locations. Several of the 54 electrocardiographic criteria were never satisfied. Criteria for posterior infarction were seldom present, suggesting "cancellation effect" of coexisting anterior infarction. These results will be the basis for future modification of QRS criteria for estimating myocardial infarct size.

Evaluation of changes in standard electrocardiographic QRS waveforms recorded from activity-compatible proximal limb lead positions

Proximal limb lead positions are currently used for activity-compatible electrocardiographic monitoring of myocardial ischemia. Two previously described systems for alternate limb lead placement were studied in patients with and without QRS evidence of healed anterior or inferior myocardial infarction. An innovative method was used to simultaneously record 6 standard and 6 modified limb leads, and 3 standard and 3 modified precordial leads on a standard digital electrocardiograph. Both alternate lead placement systems showed rightward frontal plane axis shift and diminished Q-wave durations in lead aVF compared with those of their simultaneous standard controls. Furthermore, potential differences between the standard distal limb lead sites and 5 more proximal sites were explored along each limb. Differences along the left arm were accentuated relative to those along the right arm owing to differences in proximity of the arms to the myocardium. Along the lower limb, and anterior site showed less deviation from standard than did a more lateral site. It is imperative that recordings from alternate sites be labeled accordingly so that their output cannot be confused with that obtained from standard sites.

Evaluation of a QRS scoring system for estimating myocardial infarct size. VIII. Specificity in a control group with left ventricular hypertrophy and proposal of a new scoring system for use with this confounding factor

Electrocardiographic differentiation between left ventricular hypertrophy (LVH) and myocardial infarction (MI) is often difficult because both diagnoses are based primarily on QRS changes on the electrocardiogram (ECG). The specific goal of this study was the development of ECG criteria that could be used with the complete Selvester QRS scoring system for MI size in patients with LVH. A study population of 127 patients had significant aortic valve disease verified by cardiac catheterization. Inclusion in the study required no significant coronary artery disease, no focal contraction abnormality on the left ventriculogram, and no documented MI. Quantitative criteria for LVH developed by Bonner (IBM) and also those developed by the Cornell group were used to determine the ECG evidence for LVH in each patient. One or both sets of criteria were met in 110 (87%) of the 127 patients. This group was compared to a previously evaluated control population of 500 normal subjects. The complete 54-criteria, 32-point QRS MI size scoring system was applied to the 12-lead ECG of both groups. The score was 98% specific in the normal controls and 73% specific in the LVH group using a score of greater than 3 points as diagnostic for MI. Of the 54 individual QRS criteria, 16 failed to achieve 95% specificity in the LVH population: 13 were for anterior (and apical), 2 for inferior, and 1 for posterior locations. Of these 16, minor modifications to 11 were sufficient to achieve the 95% specificity standard.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of carbon monoxide on myocardial ischemia

The purpose of this study was to determine whether low doses of carbon monoxide (CO) exacerbate myocardial ischemia during a progressive exercise test. The effect of CO exposure was evaluated using the objective measure of time to development of electrocardiographic changes indicative of ischemia and the subjective measure of time to onset of angina. Sixty-three male subjects (41-75 years) with well-documented coronary artery disease, who had exertional angina pectoris and ischemic ST-segment changes in their electrocardiograms, were studied. Results from three randomized, double-blind test visits (room air, low and high CO) were compared. The effect of CO exposure was determined from the percent difference in the end points obtained on exercise tests performed before and after a 1-hr exposure to room air or CO. The exposures resulted in postexercise carboxyhemoglobin (COHb) levels of 0.6% +/- 0.3%, 2.0% +/- 0.1%, and 3.9% +/- 0.1%. The results obtained on the 2%-COHb day and 3.9%-COHb day were compared to those on the room air day. There were 5.1% (p = 0.01) and 12.1% (p less than or equal to 0.0001) decreases in the time to development of ischemic ST-segment changes after exposures producing 2.0 and 3.9% COHb, respectively, compared to the control day. In addition, there were 4.2% (p = 0.027) and 7.1% (p = 0.002) decreases in time to the onset of angina after exposures producing 2.0 and 3.9% COHb, respectively, compared to the control day. A significant dose-response relationship was found for the individual differences in the time to ST end point and angina for the pre- versus postexposure exercise tests at the three carboxyhemoglobin levels. These findings demonstrate that low doses of CO produce significant effects on cardiac function during exercise in subjects with coronary artery disease.

Discriminant analysis of the standard 12-lead ECG for diagnosing non-Q wave myocardial infarction

Discriminant analysis was performed on 12 standard lead data from 159 normal subjects (N) and 304 patients with first myocardial infarction (MI): the latter group consisted of 543 patients with acute non-Q wave MI (NQMI-group A), 68 patients with acute Q wave MI (QMI-group B) and 183 patients (group C) with recent (29) or old (154) QMI. A discriminant function was computed to separate optimally the larger group of QMI patients (group C) from N. A total of 7 features accounted for a specificity of 92% and a sensitivity of 89%. The classification model was then tested on patients with acute MI, regardless of the presence of Q waves (groups A and B); rates of correct classification were 72% for acute NQMI and 85% for acute QMI. The best measurements were voltages in the late portion of the T wave in aVR, V1 and V5, in early and late QRS in V2, at mid-QRS in lead II and in the second half of the P wave in V1. A weighted combination of these features with the coefficients of the discriminant function produced individual discriminant scores for each subject. Group-mean scores were 1.82 for N, -1.27 for acute QMI, -1.14 for old QMI and -.44 for acute NQMI, indicating that acute NQMI was "closer" to N than both acute and old QMI. QRS measurements from the 12-lead ECG were also used to derive the 45 criteria/33 point Selvester score in 53 patients with NQMI: 32% of NQMI were classified as MI with a score of 3 points or more (corresponding to a posterior probability greater than .50). These results were compared with those achieved by multivariate analysis using only QRS measurements: 56% of NQMI were classified as MI with a posterior probability threshold greater than .50. Associating a point score greater than or equal to 1 with criteria for ST-T abnormalities yielded a sensitivity of 72% at a specificity level of 95%. The results emphasize the presence of diagnostic information outside the initial part of QRS, the power of multivariate statistical procedures applied on continuous measurements and the potential benefit of discriminant scores for quantitative assessment of myocardial infarction.

Sensitivity of a set of myocardial infarction screening criteria in patients with anatomically documented single and multiple infarcts

A subset of 3 screening criteria (Q wave greater than or equal to 30 ms in lead aVF, any Q or R wave less than or equal to 10 ms and less than or equal to 0.1 mV in lead V2, and R wave greater than or equal to 40 ms in V1) has been proposed to identify single nonacute myocardial infarcts. Cumulatively, these 3 criteria achieved 95% specificity, and 84 and 77% sensitivities for inferior and anterior myocardial infarcts, respectively, among patients identified by coronary angiography and left ventriculography. This study establishes the true sensitivities of the set of screening criteria in 71 patients with anatomically proven single myocardial infarcts and 32 patients with multiple myocardial infarcts. In the single inferior infarct group, the aVF criterion was 90% sensitive. The V2 criterion (any Q or R wave less than or equal to 10 ms and less than or equal to 0.1 mV) was 67% sensitive in the single anterior infarct group. No single criterion proved sensitive in identifying a posterolateral infarct. The set of screening criteria performed just as well for multiple infarcts as it did for single infarcts, with a cumulative sensitivity of 72%. The overall sensitivity of the screening set in the 103 patients in all groups was 71%.

Anatomic validation of electrocardiographic estimation of the size of acute or healed myocardial infarcts

Seventeen new criteria added to the simplified version of the Selvester QRS scoring system to comprise the complete version were evaluated to determine their value in estimating the size of single infarcts. These non-Q-wave criteria might be particularly useful regarding posterolateral infarcts in the distribution of the left circumflex artery. The study population was made up of 21 anterior, 30 inferior and 20 posterolateral single myocardial infarction (MI) patients with no evidences of bundle branch or fascicular blocks, ventricular hypertrophy or previous MI on their final stable electrocardiogram. The complete system's maximum 32 points is capable of indicating MI in 96% of the left ventricle and it estimated a mean electrocardiographic MI size that better approximated the anatomic size compared with the simplified version in all MI locations. The correlation between anatomic and electrocardiographic MI size using the complete system was better and statistically significant for the posterolateral MI group (simplified r = 0.55, p less than 0.01 vs complete r = 0.70, p less than 0.0006). Criteria such as Q and S amplitude less than or equal to 0.3 mV in V1 and less than or equal to 0.4 mV in V2 were particularly helpful. This study documents the improved ability provided by the 17 additional non-Q-wave criteria which have been added in the complete version of this scoring system regarding the sizing of infarcts in the region of the left ventricle supplied by the left circumflex artery.

Intraventricular conduction defect (IVCD), real or fancied, QRS duration in 1,254 normal adult white males by a multilead automated algorithm

The QRS duration (QRSD) on a digital 12 simultaneous lead ECG was measured by a commercially available recording cart (Marquette MACII 12SL) in 1,254 white male safety workers (ages 19-65, mean 34). All had a negative history (including drugs known to affect the cardiovascular or pulmonary systems), a negative family history (in immediate family members before age 55), no physical findings suggestive of heart disease, a normal blood chemistry profile, pulmonary function tests, and symptom limited bicycle exercise test. The frontal QRS axis was between -30 and -65 in 22 of 1,254 (1.8%). Twenty-seven of 1,254 (2.1%) had QRSD greater than or equal to 120 ms-14 of these had normal morphology; 2 had RBB; 3 had atypical RBB; 5 had R' in V1, V2; 2 had WPW; and 1 had Superior Fascicular Block. Sixty-three (5%) had a QRSD greater than or equal to 112 and less than or equal to 116 ms-36 of this group had normal morphology; 1 had typical RBBB; and 26 had R' V1, V2 (considered a normal variant as it occurred in 360 of 1,164 remaining with QRSD less than or equal to 108). In 1,224 white men with normal QRS morphologies and frontal axis (-25 to 100), the 98% upper and lower bounds of QRSD with the 12SL algorithm, like that seen in BSMs, was 80-116 ms, peak 96 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term effects of carbon monoxide exposure on the exercise performance of subjects with coronary artery disease

Patients with atherosclerotic cardiovascular disease may be adversely affected by the presence of carboxyhemoglobin, even at low concentrations. We investigated the effects of carbon monoxide exposure on myocardial ischemia during exercise in 63 men with documented coronary artery disease. On each test day, subjects performed two symptom-limited incremental exercise tests on a treadmill; the tests were separated by a recovery period and 50 to 70 minutes of exposure to either room air or air containing one of two concentrations of carbon monoxide (117 +/- 4.4 ppm or 253 +/- 6.1 ppm). The order of exposure was assigned randomly. On each occasion, neither the subjects nor the study personnel knew whether the subjects had been exposed to room air or to one of the concentrations of carbon monoxide. Exposure to room air resulted in a mean carboxyhemoglobin level of 0.6 percent, exposure to the lower level of carbon monoxide resulted in a carboxyhemoglobin level of 2.0 percent, and exposure to the higher level of carbon monoxide resulted in a level of 3.9 percent. An effect of carbon monoxide on myocardial ischemia was demonstrated objectively by electrocardiographic changes during exercise. We observed a decrease of 5.1 percent (90 percent confidence interval, 1.5 to 8.7 percent; P = 0.02) and a decrease of 12.1 percent (90 percent confidence interval, 9.0 to 15.3 percent; P less than or equal to 0.0001) in the length of time to a threshold ischemic ST-segment change (ST end point) after carbon monoxide exposures that produced carboxyhemoglobin levels of 2.0 percent and 3.9 percent, respectively. The length of time to the onset of angina decreased by 4.2 percent (90 percent confidence interval, 0.7 to 7.9 percent; P = 0.054) at the 2.0 percent carboxyhemoglobin level and by 7.1 percent (90 percent confidence interval, 3.1 to 10.9 percent; P = 0.004) at the 3.9 percent carboxyhemoglobin level. Significant dose-response relations were found in both the change in the length of time to the ST end point (P less than or equal to 0.0001) and the change in the length of time to the onset of angina (P = 0.02). We conclude that low levels of carboxyhemoglobin exacerbate myocardial ischemia during graded exercise in subjects with coronary artery disease.

Acute effects of carbon monoxide exposure on individuals with coronary artery disease

The purpose of this study was to determine, using more objective evidence than that reported in previous studies, whether or not exposures to carbon monoxide that produce approximately 2% or 4% blood carboxyhemoglobin levels cause an exacerbation of myocardial ischemia during a progressive exercise test. The objective measurements were based on the development of electrocardiographic evidence of ischemia. In addition, time to onset of angina pectoris was studied. Male subjects, ages 35 to 75, with stable exertional angina pectoris and positive exercise treadmill tests with reproducible ischemic ST-segment changes in their electrocardiograms, were studied. In addition, each subject fulfilled at least one of the following criteria of coronary artery disease: angiographic evidence of at least a 70% occlusion of one or more major coronary artery; prior documented myocardial infarction; or a positive exercise thallium test. Each subject was evaluated on four separate occasions, a qualifying visit and three blinded test visits, which involved exposure (in random order) to air without added carbon monoxide and to air that contained carbon monoxide concentrations calculated to produce approximately 2.2% or 4.4% carboxyhemoglobin, measured by gas chromatography, at the end of the exposure period. These immediate postexposure target levels were set 10% higher than the desired postexercise carboxyhemoglobin levels of 2.0% and 4.0% because exercise while breathing room air results in loss of carbon monoxide. The actual one-minute postexercise levels reached were 2.0% +/- 0.1% (mean +/- standard error of the mean) and 3.9% +/- 0.1%. On each test day, the subject performed a symptom-limited exercise test on a treadmill, was exposed for approximately one hour to air or to one of two levels of carbon monoxide in air, and then performed a second exercise test. Time to the onset of ischemic ST-segment changes and time to the onset of angina were determined for each exercise test. The percent difference for these endpoints on the pre- and postexposure exercise tests was determined, and then the results on the 2%-COHb-target day and the results on the 4%-COHb-target day were compared to those on the control day. Data from the 63 subjects who completed the three test visits and met all protocol criteria were analyzed. There were 5.1% (p = 0.01) and 12.1% (p less than or equal to 0.0001) (trimmed mean) decreases in the time to development of ischemic ST-segment changes after the 2%- and 4%-COHb-target exposures, respectively, compared to the control day.(ABSTRACT TRUNCATED AT 400 WORDS)

Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the right and left circumflex coronary arteries

The dynamic QRS amplitude changes that appear during 1-vessel percutaneous transluminal coronary angioplasty of the right and left circumflex coronary arteries were studied in 20 patients using continuous 3-lead electrocardiographic recordings representing leads aVF, V2 and V5. The balloon inflations that produced the greatest extent of ST-segment deviation were identified for each lead ("maximally ischemic periods"). QRS amplitude measurements were performed manually at both the PR and shifted J-ST baselines at 10-second intervals during these periods to determine that baseline from which the R and S waves most nearly maintained their control amplitudes. There was no significant baseline relation for either the R or the S waves in leads V2 and V5 during ischemia. However, the R-wave changes in lead aVF were significantly associated with the PR- versus the J-ST-segment baseline (p = 0.007); the S wave, when it occurred, had no tendency for either baseline. The electrocardiographic records were also examined visually for characteristics of left posterior (inferior) "periischemic block" likely to occur uniquely in patients with a dominant right or left circumflex occlusion. There were 2 patients with obstruction of the right circumflex artery who exhibited the characteristics of periischemic block during percutaneous transluminal coronary angioplasty, as evidenced by an increase in R-wave duration, amplitude or both in lead aVF.

Instrumentation and practice standards for electrocardiographic monitoring in special care units. A report for health professionals by a Task Force of the Council on Clinical Cardiology, American Heart Association

The proposed recommendations for continuous electrocardiographic monitoring systems represent goals for future development. Description of a technique in the report does not constitute an endorsement of its clinical use. Lead systems for ECG monitoring must adequately sense the cardiac electrical field and the leads should be standardized. Future monitors should be capable of simultaneously displaying and analyzing multiple leads. Recommendations for electrode placement and position of patient are made. Important parameters in each category of standards for instrumentation published in 1983 in the American National Standard for Cardiac Monitors, Heart Rate Meters, and Alarms are listed. Selected procedures proposed by the Association for the Advancement of Medical Instrumentation to inform users of minimally acceptable accuracy of computerized systems in a standardized manner are presented. Emphasis is placed on the importance of nursing and medical staff capabilities. Personnel qualifications and training as well as systems to assure and maintain quality of immediate ECG diagnosis are highlighted.

Evaluation of a QRS scoring system for estimating myocardial infarct size. VI: Identification of screening criteria for non-acute myocardial infarcts

Each of the 54 criteria in the Selvester 32-point QRS scoring system for estimation of myocardial infarct (MI) size has attained greater than or equal to 95% specificity in normal subjects. This study was performed to identify a subset of those criteria with cumulative specificity greater than or equal to 95% and maximal sensitivity for use in screening for the presence of non-acute MI. Coronary angiography and left ventriculography were used to identify 500 normal subjects, 60 patients with isolated anterior MI and 62 patients with isolated inferior MI. Patients with the QRS confounding factors of ventricular hypertrophy, fascicular block or bundle branch block on their electrocardiogram were not included. Using stepwise logistic regression analysis, the screening criteria identified were: (1) Q greater than or equal to 30 ms in aVF, (2) R less than or equal to 10 ms and less than or equal to 0.1 mV in V2 and (3) R greater than or equal to 40 ms in V1. Cumulatively, these 3 screening criteria achieved 84% and 77% sensitivities for inferior and anterior MI groups, respectively. Thus, a set of 3 criteria from the Selvester QRS scoring system is capable of identifying single non-acute anterior or inferior MI in 80% of patients, and falsely indicating presence of MI in only 5% of normal subjects.

False-positive posterior myocardial infarct criteria during left anterior descending coronary angioplasty

In reviewing ECG change during acute anterior myocardial infarction (AMI) and during transluminal coronary angioplasty of the left anterior descending (LAD) coronary artery, QRS changes mimicking posterior myocardial infarct (PMI) and false-positive points for PMI using the QRS infarct size scoring system were observed in about 20% of patients. Nineteen patients in whom a three-lead electrocardiogram (ECG) was continuously recorded during transluminal coronary angioplasty of a proximal left anterior descending (LAD) coronary artery were reviewed. All but two had significant ST-segment shifts in V2 within a few seconds of balloon occlusion of a proximal LAD. In many such patients the R wave amplitude in V2 measured from the PR segment baseline remained relatively stable and the S amplitude tracked with the J. point. However, of the 19 patients studied, 11 had transient QRS changes greater than could be accounted for by baseline shift alone and 4 had transient false-positive PMI points by QRS MI size score. Transient QRS changes were observed as follows: (1) significant increase in R waves and/or decrease in S waves in V2 due to right septal block (or conduction delay) occurred in 3 of 11 patients and was the cause of the false-positive criteria for PMI; (2) 5 of 11 patients had a major decrease in R waves in V2 due to left septal block; (3) 2 of 11 patients had both (1) and (2); and (4) 1 of 11 had transient frontal plane axis shifts with the QRS configuration of anterosuperior fascicular block plus right and left septal block.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of the simplified Selvester QRS score in patients with coronary artery disease

The relation of the simplified Selvester QRS scoring system for the estimation of myocardial infarct size to survival was studied in 1,915 nonsurgically treated patients with documented coronary artery disease. Electrocardiograms (ECGs) were scored according to a simplified 29 point QRS scoring system. Using Cox model analyses, QRS scores were found to provide strong prognostic information by themselves (p less than 0.0001). Higher QRS scores were associated with lower survival rates. Patients with a score of 0 had a 1 year survival rate of 95% and a 5 year survival rate of 88%; patients with a score of 10 or more had survival rates of 81 and 52%, respectively, at the same intervals. Directly compared with the presence or absence of Q waves on the ECG, QRS scores provided greater prognostic information (p less than 0.001). When compared with 13 individual factors previously shown to provide the greatest independent prognostic information, the QRS score was the third most powerful individual prognostic factor. It did not contribute independent prognostic information in combination with the whole group, but did provide independent information in combination with the six most predictive factors. Its prognostic information overlapped mostly with clinical factors related to heart failure, and combined best with clinical factors related to the severity of ongoing myocardial ischemia. Because it is inexpensive and simple and maximizes the prognostic information from the ECG, the simplified Selvester QRS scoring system can be a useful clinical descriptor for practitioners and clinical investigators.

Effects of pulmonary emphysema on QRS infarct size score

Pulmonary emphysema can produce false-positive electrocardiographic (ECG) changes of anterior myocardial infarction (MI). This problem was not addressed in earlier studies of the Selvester 54 Criteria/32 Point QRS score for MI size. The purpose of this study was to examine an automated Hewlett Packard ECG Computer Language (HP-ECL) implementation of the QRS score in the following groups of subjects. Patients who had been studied for possible lung disease with pulmonary tests, including lung volumes, were divided into two groups: group 1 (n = 133), with abnormal tests (emphysema); and group 2 (n = 102), with normal tests (no emphysema). Two other groups were studied: group 3 (positive controls, n = 44), with greater than 3 QRS points for MI on ECG and documented coronary disease with wall motion abnormalities on angiography; and group 4 (negative controls, n = 146), 49 house staff and 97 clinically normal men. A frontal plane P axis greater than 65 separated 90% of patients with emphysema from those without. Of 133 patients with emphysema, 60 (45%) had greater than 3 QRS points for MI on ECG, mainly from Q criteria in aVL and V1-V3; decreased R criteria 1 in V2, V3, and V6; and abnormal R/S criteria in V4-V6. Using HP-ECL, the QRS score was readily modified so that when P axis was greater than 65 these MI size criteria were suppressed. This resulted in a more appropriate incidence of MI diagnoses: 2% (down from 45%) in emphysema patients, no change in specificity, and minor reduction in sensitivity to MI in infarct controls from 100% to 96%.(ABSTRACT TRUNCATED AT 250 WORDS)