Electrocardiographic criteria for the diagnosis of anterior myocardial infarction: importance of the duration of precordial R waves

Topology and random-walk network representation of cardiac dynamics for localization of myocardial infarction

While detection of acute cardiac disorders such as myocardial infarction (MI) from electrocardiogram (ECG) and vectorcardiogram (VCG) has been widely reported, identification of MI locations from these signals, pivotal for timely therapeutic and prognostic interventions, remains a standing issue. We present an approach for MI localization based on representing complex spatiotemporal patterns of cardiac dynamics as a random-walk network reconstructed from the evolution of VCG signals across a 3-D state space. Extensive tests with signals from the PTB database of the PhysioNet databank suggest that locations of MI can be determined accurately (sensitivity of ∼88% and specificity of ∼92%) from tracking certain consistently estimated invariants of this random-walk representation.

Optimized electrocardiographic criteria for prior inferior and anterior myocardial infarction

BACKGROUND AND PURPOSE

The first purpose of the study was to optimize empirically the detection of prior inferior myocardial infarction (IMI) and prior anterior myocardial infarction (AMI) by electrocardiogram (ECG). The second purpose was to compare the diagnostic performances of the new criteria with those of 3 widely used commercial diagnostic ECG algorithms.

MATERIALS AND METHODS

We analyzed the digital ECG data from 1138 subjects with suspected coronary artery disease in whom the presence or absence of prior IMI or AMI was documented by coronary angiography and left ventriculography. We used receiver operating characteristic curves to develop the new criteria for prior IMI and AMI using a training set of 562 subjects and then tested their diagnostic performances using a separate test set of 576 subjects. In both the training and test sets, we used χ(2) test to compare the performances of the new criteria with those of 3 commercial computerized diagnostic algorithms.

RESULTS

The best criterion for prior IMI was the algebraic sum of the Q and T amplitudes in leads III and aVF. Its sensitivities/specificities were 71%/98% and 74%/98% in the training and test sets, respectively. The best criterion for prior AMI was the algebraic sum of the Q, R, and T amplitudes minus the Q duration in leads V(2), V(3), and V(4). Its sensitivities/specificities were 68%/98% and 65%/98% in the training and test sets, respectively. In both the training and test sets, these diagnostic performances were generally superior to those of the 3 commercial algorithms.

CONCLUSIONS

Using digital ECG data, we developed and tested new criteria for prior IMI and AMI whose diagnostic performances are generally superior to each of 3 widely used commercial ECG diagnostic algorithms.

Electrocardiographic poor R-wave progression: analysis of multiple criteria reveals little usefulness

BACKGROUND

Poor or reverse R-wave progression (PRWP) is a common statement on electrocardiogram (ECG) interpretations, but its value in diagnosing anterior myocardial infarction (MI) is disputed. We assessed the accuracy of PRWP criteria in diagnosing anterior MI.

METHODS

We searched MEDLINE (1960-1998) and found 3 criteria for PRWP. We included a modified version of the Marquette Muse system's criteria and multiple novel criteria. We interpreted resting ECGs of consecutive patients undergoing pharmacologic stress tests with dual isotope gated single photon emission computed tomography. Subjects with Q-wave anterior MI, bundle branch block, or Wolf-Parkinson-White syndrome were excluded. We established whether patients met the PRWP criteria. A nuclear cardiologist blinded to PRWP classifications reviewed the scintigrams. Chi2 methods were used for statistical analysis.

RESULTS

Inclusion criteria were met by 122 subjects. The standard PRWP criteria were met in 15% to 42% of ECGs. Of subjects meeting PRWP criteria, 2% to 9% had anterior MI and 27% to 33% had anterior MI or ischemia. These proportions were similar to those expected by chance. The performance of PRWP criteria did not improve when subjects with electrocardiographic left ventricular hypertrophy were excluded or when more stringent criteria for right precordial R-wave amplitude were tested.

CONCLUSIONS

In our study of patients undergoing cardiac stress tests, only a small percentage of patients who met various criteria for PRWP (a proportion no different than would be expected by chance) had anterior MI. Conclusions about the presence of anterior MI solely on the basis of PRWP have little usefulness.

Using directly acquired digital ECG data to optimize the diagnostic criteria for anterior myocardial infarction

The use of a newly developed method of directly transferring digital data from Marquette electrocardiogram (ECG) systems (Milwaukee, Wisconsin) to personal computers for subsequent storage and analysis is illustrated. This method can eliminate the slowness and inaccuracy associated with measuring relevant ECG parameters from analog tracings and manually entering the data into a computer. In this study, the new method was used to derive ECG criteria for anterior myocardial infarction and to compare their performances to those of the current Marquette 12SL diagnostic program and of a group of cardiologists who had also interpreted the ECGs. Using angiographic data, 82 normal subjects and 55 patients with anterior myocardial infarction were identified. The digital ECG data from the patients in each group were transferred to a personal computer and frequency distributions of these data were generated. From these frequency distributions, the ECG criteria that most reliably separated the two groups were identified. The diagnostic performance of the best of these empirically derived criteria appears clinically superior to the performances of both the 12SL program and the cardiologists who had also interpreted the ECGs.

The presence of small q waves and decreased precordial r waves indicates a small amount of fibrosis of the anterior myocardial wall

Biopsy specimens were obtained from the anterior wall of the left ventricle during aortocoronary bypass surgery in 79 patients with critical narrowing or occlusion of the left anterior descending artery. The percent of fibrous replacement on histological analysis was calculated using the point-count method and compared with electrocardiographic findings in the precordial leads. In specimens from 19 patients with abnormal Q waves, the percent of fibrosis ranged between 38% and 100% (mean, 61 +/- 17%). Fifteen patients had small q waves or decreased r waves, and the percent of fibrosis in these patients ranged between 20% and 45% (mean, 38 +/- 10%). Specimens from 45 patients with normal QRS complexes had between 3% and 27% (mean, 11 +/- 5%) fibrosis of the entire thickness of the anterior wall. Thus, small q waves or decreased r wave amplitude in the precordial leads indicates a lesser degree of myocardial loss than the presence of abnormal Q waves.

Evaluation of a laboratory health examination programme in a Swedish industry (Volvo)

The records of 117 subjects, workers who had participated in a health examination at a Swedish industry, were studied retrospectively in order to find out which measures had been taken as a consequence of the results from the different examinations. The extensive laboratory examination programme that had been carried out seemed to be of limited value. It is concluded that the extensive examination programmes carried out in many industries should be re-evaluated more critically.

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%.

R peak delay in V6. Diagnostic implications in coronary heart disease

Epimyocardial excitation is delayed in areas overlying infarcted myocardium. On the assumption that a delayed R peak in V6 could indicate anterior myocardial infarction (AMI) in the absence of diagnostic Q waves, the findings of angiocardiography (n = 148) and thallium scanning (n = 46) of 194 patients with suspected coronary heart disease (CHD) were compared with regard to two criteria: A (R peak in V6 precedes S peak in V2, or both peaks occur simultaneously, n = 158) and B (R peak in V6 is later than S peak in V2 [R peak delay in V6], n = 36). Of 92 patients with unconfirmed CHD, 4 fit criterion B, and 3 of these had hypertensive heart disease. In 102 patients with confirmed CHD, B was present in 15 of 79 evaluated with angiocardiography and in 17 of 23 patients who had nuclear scanning. Anterior akinesis or dyskinesis was more prevalent in group B (13 cases, 86%) than in group A (17 cases, 26.6%; p = 0.000), as were irreversible anterior thallium defects, with 16 cases in group B (94.1% and 3 cases in group A (50%) (p = 0.016). Two of the three false positives had anterior hypokinesis and one had hypertensive cardiovascular disease. B was less sensitive (59.2%) but demonstrated a specificity of 95.2% and a positive predictive value of 80.6% for the detection of AMI. If used in conjunction with C (poor or reverse R wave progression from V1 to V4, notching at the R upstroke or rsR' in V4, V5, or V6), sensitivity was decreased (38.6%) but false positives were eliminated (specificity and positive predictive value reached 100%). Thus, in the setting of CHD, B can be recommended as a marker of non-Q wave AMI, and its diagnostic reliability is maintained, even in systemic arterial hypertension, if C is taken into consideration.

Vectorcardiogram synthesized from a 12-lead ECG: superiority of the inverse Dower matrix

Vectorcardiographic (VCG) criteria for the diagnosis of, for example, myocardial infarction and right ventricular hypertrophy, are superior to the corresponding 12-lead ECG criteria. Contour and rotation of the QRS loops are important parts of these VCG criteria that have no direct counterpart in the 12-lead ECG. Therefore, attempts have been made to synthesize VCGs from 12-lead ECGs for diagnostic purposes. Visual comparison of QRS loops from the Frank VCG and three different synthesized VCGs was made by three independent observers to determine which method produces the most Frank-like QRS loops. The inverse transformation matrix of Dower proved to be the best method of synthesis. Normal limits for some clinically important measurements in VCG interpretation were calculated for this synthesis method and the Frank VCG.

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.

Enhancement of an old diagnostic tool, the standard 12-lead ECG

The standard 12-lead electrocardiogram (ECG) has long been a reliable clinical tool for diagnosis of myocardial infarction (MI). Minutes may be crucial in the decision regarding urgent interventions for the salvage of severely ischemic myocardium during an acute MI. Besides history and physical findings the ECG may be the only clinical tool immediately available in deciding to initiate acute coronary thrombolysis or balloon angioplasty. Most of the newer techniques are difficult to perform and time consuming, and thus are not immediately available. Recent studies have indicated that there may be important information revealed by the amplitude and direction of the ST-T vectors on the admission ECG that will correlate with the final infarct size which evolves during the next few hours. The Selvester QRS scoring system, based on computer simulations of the human heart activation sequence, uses quantitative information in the 12-lead ECG to estimate the size of an MI. This system, which can be automated, has been examined for specificity in a large database of normals, and validated in a series of comprehensive post-mortem studies, and in other clinical estimates of prognosis and MI size. The QRS scoring system is limited by its inability to differentiate between small MIs and normal myocardium and by the confounding effects on the ECG of ventricular hypertrophy, conduction defects, and multiple MIs. Current studies are expected to overcome most of these limitations. Computer technology further augments the clinical utility of the ECG by providing unique assessment of a patient from individualized demographic and historical characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the classification ability of the electrocardiogram and vectorcardiogram

Controversy exists over the classification ability of the standard 12-lead electrocardiogram (EGG) and the vectorcardiogram (VCG). In this study the diagnostic information content and classification performance of the ECG and VCG were examined using multivariate statistical techniques and a large validated data base of 3,266 cases. Logistic classification models were developed to differentiate between 7 diagnostic entities: normal (n = 538), left (n = 557), right (n = 323) and biventricular (n = 437) hypertrophy, and anterior (n = 390), inferior (n = 657) and combined (n = 364) myocardial infarction. The models were obtained from a learning sample (n = 2,446) using an optimal set of computer derived ECG and VCG measurements. They were subsequently applied to a test sample (n = 820). In the learning sample, the discrimination models resulted in a total correct classification rate of 69.6% for the ECG and 69.4% for the VCG. The total accuracy rate was slightly lower in the test set: 66.3% for the ECG and 67.1% for the VCG. The combined use of the best ECG and VCG variables did not increase total diagnostic accuracy. When cases with biventricular hypertrophy and combined infarction were deleted, accuracy rates of more than 80% were achieved for both lead systems. Differences in the classification rates for the subgroups were not statistically significant. Thus, the conventional 12-lead ECG is as good as the VCG for the differential diagnosis of 7 main entities, provided identical procedures are used in the design of the classifiers.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic significance for coronary artery disease of abnormal Q waves in the "lateral" electrocardiographic leads

To determine the diagnostic significance for coronary artery disease of abnormally large Q waves in leads I, aVL, V5 and V6--the "lateral" electrocardiographic leads--the electrocardiograms of 240 patients who had undergone cardiac catheterization were studied. First, the electrocardiograms of 99 subjects proved normal by cardiac catheterization (group 1) were studied to determine the values of the durations of Q waves in leads I, aVL, V5 and V6 that should be exceeded to be considered abnormal. These values were 30, 30, 20 and 25 ms, respectively. Then, 67 patients were identified who had abnormal Q waves in at least 1 of these leads (group 2) and 74 patients with at least 1 angiographic abnormality but without abnormal Q waves in any of these leads (group 3). Group 2 had generally more extensive left ventricular disease and a higher prevalence of anterior, inferior and apical healed myocardial infarction (MI) than group 3. However, compared with group 3, group 2 had lower prevalences of significant narrowing of the coronary arteries that supply the left ventricular lateral wall. Within group 2, abnormal Q waves in leads I and aVL (traditionally designated high lateral MI) were associated with anterior as well as apical MI, and abnormal Q waves in leads V5 and V6 (traditionally designated anterolateral MI) were associated with inferior as well as apical MI. Thus, abnormal Q waves in leads I, aVL, V5 and V6 tend to reflect apical rather than lateral MI and the term anterolateral MI is especially misleading.

Importance of the distance and velocity of electrical forces in the diagnosis of inferior wall healed myocardial infarction: a vectorcardiographic study

The vectorcardiograms of 41 patients with angiographically proved inferior myocardial infarction (MI) and 51 normal subjects were analyzed to determine whether it is the time (in milliseconds) or the distance (in millivolts) of the initial superiority directed forces of ventricular depolarization that is increased more by inferior MI, and whether parameters derived from both the initial superior time and distance can be used to detect inferior MI. The 10 best individual and the 10 best paired criteria for inferior MI involve superior distance, either alone or used in the calculation of average velocity (in volts per second), and the product of initial superior time and distance (in millivolts per second). The 2 best individual criteria for inferior MI are: inferior velocity more than 0.0065 V/s (sensitivity 71%, specificity 100%) and superior distance more than 0.39 mV (sensitivity 68%, specificity 100%). These diagnostic performances are superior to those of the best criterion that involves only the duration of the initial superior forces, i.e., initial superior time longer than 28 ms (sensitivity 49%, specificity 98%) (chi 2 = 8.42, p less than 0.005 and chi 2 = 6.31, p less than 0.025, respectively). Initial superior distance and parameters calculated from both initial superior distance and time are better vectorcardiographic criteria for inferior MI than are criteria that involve only initial superior time.

Comparison of optimal scalar electrocardiographic, orthogonal electrocardiographic and vectorcardiographic criteria for diagnosing inferior and anterior myocardial infarction

A scalar electrocardiogram (ECG), orthogonal ECG and vectorcardiogram (VCG) were recorded in 46 normal persons, 38 patients with inferior myocardial infarction (MI) and 22 patients with anterior MI proved at cardiac catheterization. The diagnostic information provided by the scalar ECG, orthogonal ECG and VCG was quantitatively analyzed and the optimal criteria for diagnosing inferior and anterior MI exhibited by each method were identified. The optimal scalar electrocardiographic, orthogonal electrocardiographic and vectorcardiographic criteria, respectively, are: For inferior MI: initial superior duration in lead aVF greater than 30 ms (sensitivity 63%, specificity 100%), superior/inferior amplitude ratio in lead Y greater than or equal to 0.2 (sensitivity 63%, specificity 96%), initial superior duration greater than 29 ms or initial superior distance greater than 0.4 mV in the frontal plane loop (sensitivity 68%, specificity 100%). For anterior MI: initial anterior duration in lead V2 less than 20 ms or initial anterior duration in lead V3 less than 25 ms (sensitivity 91%, specificity 100%), anterior/posterior duration ratio in lead Z less than 0.3 (sensitivity 73%, specificity 98%), initial anterior duration less than 15 ms in the transverse plane loop (sensitivity 64%, specificity 98%). There were no significant differences among the performances of the optimal scalar ECG, orthogonal ECG and the VCG for diagnosing inferior MI. However, the performance of the optimal scalar ECG was superior to that of the optimal orthogonal ECG and the optimal VCG for diagnosing anterior MI (chi-square = 5.20, p less than 0.02 and chi-square = 7.14, p greater than 0.01, respectively).