Correlation of electrocardiogram and vectorcardiogram with coronary occlusion and myocardial contraction abnormality

Comparison of cardiogoniometry and ECG at rest versus myocardial perfusion scintigraphy

BACKGROUND

Cardiogoniometry (CGM) is a novel resting electrocardiac method based on computer-generated three-dimensional data derived from cardiac potentials. The purpose of this study was to determine CGM's and electrocardiography's (ECG) accuracy for detecting myocardial ischemia and/or lesions in comparison with stress/rest myocardial perfusion scintigraphy (single photon emission computer tomography [SPECT]).

METHOD

A cohort of consecutively enrolled patients (n = 100) with suspected or known coronary artery disease (mean age 67.8 years, 52% female) were examined by CGM and resting ECG before stress/rest myocardial scintigraphy.

RESULTS

Pathological scintigraphy findings at adenosine stress perfusion (ASP) and/or rest were conclusively identified in 21 patients. Diagnostic sensitivity was 71% for CGM and 24% for ECG, specificity was 70% for CGM and 95% for ECG. Reversible ischemia was diagnosed in 16 of 21 patients with pathological scintigraphy results. In this subgroup, sensitivity was 67% for CGM and 25% for ECG.

CONCLUSIONS

At rest, the sensitivity of a CGM significantly surmounts that of a standard 12-lead ECG for detection of isolated myocardial ischemia or myocardial lesions revealed by scintigraphy/SPECT; specificity is in a reasonable range. CGM's ease of use and its considerable agreement with the results of myocardial scintigraphy, suggests a possible role for patient screening in the primary care setting.

Comparison of cardiogoniometry and electrocardiography with perfusion cardiac magnetic resonance imaging and late gadolinium enhancement

AIMS

Cardiogoniometry (CGM) is a spatio-temporal five-lead resting electrocardiographic method utilizing automated analysis. The purpose of this study was to determine CGM's and electrocardiography (ECG)'s accuracy for detecting myocardial ischaemia and/or lesions in comparison with perfusion cardiac magnetic resonance imaging (CMRI) and late gadolinium enhancement (LGE).

METHODS AND RESULTS

Forty (n= 40) patients with suspected or known stable coronary artery disease were examined by CGM and resting ECG directly prior to CMRI including adenosine stress perfusion (ASP) and LGE. The investigators visually reading the CMRI were blinded to the CGM and ECG results. Half of the patients (n= 20) had a normal CMRI while the other half presented with either abnormal ASP and/or detectable LGE. Cardiogoniometry yielded an accuracy of 83% (sensitivity 70%) and ECG of 63% (sensitivity 35%) compared with CMRI.

CONCLUSIONS

In this pilot study CGM compares more favourably than ECG with the detection of ischaemia and/or structural myocardial lesions on CMRI.

Electrocardiologic and related methods of non-invasive detection and risk stratification in myocardial ischemia: state of the art and perspectives

Background: Electrocardiographic methods still provide the bulk of cardiovascular diagnostics. Cardiac ischemia is associated with typical alterations in cardiac biosignals that have to be measured, analyzed by mathematical algorithms and allegorized for further clinical diagnostics. The fast growing fields of biomedical engineering and applied sciences are intensely focused on generating new approaches to cardiac biosignal analysis for diagnosis and risk stratification in myocardial ischemia.

Objectives: To present and review the state of the art in and new approaches to electrocardiologic methods for non-invasive detection and risk stratification in coronary artery disease (CAD) and myocardial ischemia; secondarily, to explore the future perspectives of these methods.

Methods: In follow-up to the Expert Discussion at the 2008 Workshop on "Biosignal Analysis" of the German Society of Biomedical Engineering in Potsdam, Germany, we comprehensively searched the pertinent literature and databases and compiled the results into this review. Then, we categorized the state-of-the-art methods and selected new approaches based on their applications in detection and risk stratification of myocardial ischemia. Finally, we compared the pros and cons of the methods and explored their future potentials for cardiology.

Results: Resting ECG, particularly suited for detecting ST-elevation myocardial infarctions, and exercise ECG, for the diagnosis of stable CAD, are state-of-the-art methods. New exercise-free methods for detecting stable CAD include cardiogoniometry (CGM); methods for detecting acute coronary syndrome without ST elevation are Body Surface Potential Mapping, functional imaging and CGM. Heart rate variability and blood pressure variability analyses, microvolt T-wave alternans and signal-averaged ECG mainly serve in detecting and stratifying the risk for lethal arrythmias in patients with myocardial ischemia or previous myocardial infarctions. Telemedicine and ambient-assisted living support the electrocardiological monitoring of at-risk patients.

Conclusions: There are many promising methods for the exercise-free, non-invasive detection of CAD and myocardial ischemia in the stable and acute phases. In the coming years, these new methods will help enhance state-of-the-art procedures in routine diagnostics. The future can expect that equally novel methods for risk stratification and telemedicine will transition into clinical routine.

Cardiogoniometric parameters for detection of coronary artery disease at rest as a function of stenosis localization and distribution

Cardiogoniometry (CGM), a spatiotemporal electrocardiologic 5-lead method with automated analysis, may be useful in primary healthcare for detecting coronary artery disease (CAD) at rest. Our aim was to systematically develop a stenosis-specific parameter set for global CAD detection. In 793 consecutively admitted patients with presumed non-acute CAD, CGM data were collected prior to elective coronary angiography and analyzed retrospectively. 658 patients fulfilled the inclusion criteria, 405 had CAD verified by coronary angiography; the 253 patients with normal coronary angiograms served as the non-CAD controls. Study patients--matched for age, BMI, and gender--were angiographically assigned to 8 stenosis-specific CAD categories or to the controls. One CGM parameter possessing significance (P < .05) and the best diagnostic accuracy was matched to one CAD category. The area under the ROC curve was .80 (global CAD versus controls). A set containing 8 stenosis-specific CGM parameters described variability of R vectors and R-T angles, spatial position and potential distribution of R/T vectors, and ST/T segment alterations. Our parameter set systematically combines CAD categories into an algorithm that detects CAD globally. Prospective validation in clinical studies is ongoing.

Minimal influence of anaesthesia and abdominal surgery on computerized vectorcardiography recordings

Myocardial infarction still represents a major cause of morbidity and mortality following surgical procedures. Continuous computerized on-line vector-ECG has previously been shown to be useful in the detection of myocardial ischaemia, in acute myocardial infarction and unstable angina pectoris and for ischaemia monitoring after PTCA procedures. This method was presently tested for the possible influence of anaesthesia and surgery during cholecystectomy under general anaesthesia (n = 9), and during inguinal hernia repairs using a spinal block (n = 5). The patients had no history, symptoms or signs of ischaemic heart disease. Analyses of vectorcardiographic changes were made in relation to predefined standardized anaesthetic and surgical procedures, all of which potentially could influence the vector-ECG. Three vectorcardiographic trendparameters were studied: QRS-vector difference, ST-vector magnitude and ST-change vector magnitude. The overall vectorcardiographic changes were minimal and smaller than vectorcardiographic changes previously reported during myocardial ischaemia and infarction. Since anaesthetic and surgical procedures per se had only minor effects on the vector ECG recordings, it is concluded that continuous computerized on-line vectorcardiography will not be skewed by these procedures. Hence, vectorcardiography has the potential of becoming a new monitor for the detection of perioperative myocardial ischaemia.

Vectorcardiogram more sensitive than 12-lead ECG in the detection of inferior myocardial infarction

The vectorcardiogram (VCG) is commonly stated to be more sensitive than the 12-lead electrocardiogram (ECG) for the diagnosis of inferior myocardial infarction. However, a recent study indicated that VCG is not superior to ECG for this diagnosis. The purpose of this study was to compare the performance of VCG and ECG criteria and to indicate possible explanations for the disagreement between earlier studies. Accordingly, we studied 65 patients with inferior myocardial infarction verified by left ventriculography or 201-TI myocardial scintigraphy and 351 normal subjects. Sensitivity was 69% (45/65) and 43% (28/65) for the VCG and ECG criteria, respectively. This difference was highly significant (P less than 0.001). Among the normal subjects there were only three with false positive ECG. We conclude that both VCG and ECG criteria for the diagnosis of inferior myocardial infarction are highly specific and that VCG criteria have greater sensitivity than ECG criteria.

The predictive accuracy of the electrocardiogram in identifying the presence and location of myocardial infarction and coronary artery disease

In summary, the electrocardiogram is limited in its ability to detect a myocardial infarction. Its sensitivity is compromised seriously by a substantial number of patients (table; see text) with non-Q wave infarction or regression of Q waves. Once a Q wave occurs, the predictive accuracy of those changes, in delineating the location of the infarction, is quite high. The ability of Q waves or ST segment elevation to predict or identify the "culprit artery" is less strong, primarily due to the variation in coronary anatomy commonly found. The relationship between anterior or inferior lead changes and anterior or inferior myocardial damage is close. However, lateral lead changes may more accurately represent anterolateral (I, AVL) or apical (V5-V6) infarction. Tall R waves in anterior precordial leads is most often associated with posterolateral infarction.

The value of body surface potential maps in detecting abnormal ventricular wall motion

In an effort to enlarge the clinical application of body surface potential maps (BSPMs), the authors studied the relationship between abnormal ventricular wall motion and BSPMs in 98 consecutive patients with angiographically proven coronary artery disease (CAD). Forty-nine of the patients (50%) had wall motion abnormalities as seen on single-plane left cine ventriculograms. During early ventricular depolarization, normal BSPMs have a potential maximum that is greater than the absolute value of the potential minimum; this reverses in late depolarization such that the absolute value of the potential minimum is the greater. The patients showed a significantly early reversal (p less than 0.001), and 55 (56.1%) had abnormal "early reversal" BSPMs. This abnormal "early reversal" is closely related to abnormal ventricular wall motion. Using it as an indicator of abnormal wall motion, the authors obtained the sensitivity, specificity, positive predictive value, and negative predictive value of the following conditions: LAD lesions, LCX, RCA, LAD and RCA lesions, LAD and LCX, and three-vessel disease, and for all patients. A relatively high sensitivity (85%) and specificity (80%) was found in patients with LAD lesions only or multivessel lesions in addition to LAD lesions.

Electrocardiographic diagnosis of remote posterior wall myocardial infarction using unipolar posterior lead V9

The accuracy of four electrocardiographic criteria for diagnosing remote posterior myocardial infarction was assessed prospectively in 369 patients undergoing exercise treadmill testing with thallium scintigraphy. Criteria included the following: 1) R-wave width greater than or equal to 0.04 s and R-wave greater than or equal to S-wave in V1; 2) R-wave greater than or equal to S-wave in V2; 3) T-wave voltage in V2 minus V6 greater than or equal to 0.38 mV (T-wave index); 4) Q-wave greater than or equal to 0.04 s in left paraspinal lead V9. Twenty-seven patients (7.3 percent) met thallium criteria for posterior myocardial infarction, defined as a persistent perfusion defect in the posterobase of the left ventricle. Sensitivities for the four criteria ranged from 4 to 56 percent, and specificities ranged from 64 to 99 percent. Posterior paraspinal lead V9 provided the best overall predictive accuracy (94 percent), positive predictive value (58 percent), and ability to differentiate patients with and without posterior myocardial infarction of any single criterion (p less than .0001). Combining the T-wave index with lead V9 further enhanced the diagnostic yield: the sensitivity for detecting posterior infarction by at least one of these criteria was 78 percent, and when both criteria were positive, specificity was 98.5 percent. It is concluded that a single, unipolar posterior lead in the V9 position is superior to standard 12-lead electrocardiographic criteria in diagnosing remote posterior myocardial infarction, and that combining V9 with the T-wave index maximizes the diagnostic yield.

A comprehensive analysis of myocardial infarction due to left circumflex artery occlusion: comparison with infarction due to right coronary artery and left anterior descending artery occlusion

Forty consecutive patients with creatine kinase-MB confirmed myocardial infarction due to circumflex artery occlusion (Group 1) were prospectively evaluated and compared with 107 patients with infarction due to right coronary artery occlusion (Group 2) and 94 with left anterior descending artery occlusion (Group 3). All 241 patients underwent exercise thallium-201 scintigraphy, radionuclide ventriculography, 24 h Holter electrocardiographic (ECG) monitoring and coronary arteriography before hospital discharge and were followed up for 39 +/- 18 months. There were no significant differences among the three infarct groups in age, gender, number of risk factors, prevalence and type of prior infarction, Norris index, Killip class and frequency of in-hospital complications. Acute ST segment elevation was present in only 48% of patients in Group 1 versus 71 and 72% in Groups 2 and 3, respectively (p = 0.012), and 38% of patients with a circumflex artery-related infarct had no significant ST changes (that is, elevation or depression) on admission (versus 21 and 20% for patients in Groups 2 and 3, respectively) (p = 0.001). Abnormal R waves in lead V1 were more common in Group 1 than in Group 2 (p less than 0.003) as was ST elevation in leads I, aVL and V4 to V6 (p less than or equal to 0.048). These differences in ECG findings between Group 1 and 2 patients correlated with a significantly higher prevalence of posterior and lateral wall asynergy in the group with a circumflex artery-related infarct. Infarct size based on peak creatine kinase levels and multiple radionuclide variables was intermediate in Group 1 compared with that in Group 2 (smallest) and Group 3 (largest). During long-term follow-up, the probability of recurrent cardiac events was similar in the three infarct groups. When patients with a circumflex artery-related infarct were stratified according to the presence or absence of abnormal R waves in lead V1 or V2, the abnormal R wave group had more admission ST elevation (p = 0.025), a larger infarct (p less than 0.05) and more extensive coronary artery disease (p = 0.027). In fact, all patients with a circumflex artery-related infarct and an abnormal R wave in lead V1 had multivessel disease. An abnormal R wave in lead V1 had a 96% specificity for circumflex versus right coronary artery-related infarction but a sensitivity of only 21%. Discriminate function analysis of all admission historical and ECG variables identified inferior and lateral ST elevation as independent predictors of circumflex artery-related infarction...

Comparative diagnostic value of a new computerized vectorcardiographic method (cardiogoniometry) and other noninvasive tests in medically treated patients with chest pain

The diagnostic value of cardiogoniometry (CGM), a new computerized vectorcardiographic method, for the identification of coronary artery disease was compared with other noninvasive tests in 48 medically treated patients with chest pain. Coronary angiography revealed one-vessel disease in 18, two- or three-vessel disease in 21, and normal coronary arteries in 9 patients. Cardiogoniometry was less sensitive (63%) than thallium-201 (201T1) scanning (82%), but slightly more sensitive than the exercise ECG (50%) or a recently proposed parameter of exercise performance (50%). On the other hand, specificity was comparable among these tests (exercise ECG 78%, thallium-201 scanning 72%, CGM 67%, new parameter of exercise performance 66%). Moreover, the false negative rate of noninvasive testing was reduced from 8 to 3% when CGM was added to thallium-201 scanning and exercise ECG. Our findings indicate that in view of the easier feasibility with computerized technology, the future role of vectorcardiographic methods such as CGM in the noninvasive diagnosis of coronary artery disease should be redefined.

Prevalence and severity of circumflex coronary artery disease in electrocardiographic posterior myocardial infarction

To determine the coronary anatomy responsible for electrocardiographic posterior myocardial infarction, the prevalence and severity of disease in the right coronary and left circumflex coronary arteries were compared in 21 patients with electrocardiographic posterior infarction (17 of whom had associated inferior infarction) and 23 patients with isolated electrocardiographic inferior infarction. Significant circumflex coronary artery disease (greater than or equal to 75% stenosis) was more prevalent in patients with posterior or inferoposterior infarction (17 of 21) than in those with isolated inferior infarction (11 of 23) (p less than 0.02). Significant right coronary artery disease was less prevalent in patients with posterior or inferoposterior infarction (16 of 21) than in those with isolated inferior infarction (23 of 23) (p less than 0.05). Among the 21 patients with posterior or inferoposterior infarction, disease was more severe in the circumflex coronary artery in 10 and the right coronary artery in 5 and was of equal severity in 6. Among the 23 patients with isolated inferior infarction, the more diseased artery was the right coronary artery in 21 and the circumflex artery in 2 (p less than 0.001 by chi-square analysis). Variant patterns of coronary artery dominance accounted for only 4 of the 17 patients with inferoposterior infarction. These data suggest that the likely substratum for electrocardiographic posterior or inferoposterior infarction is severe circumflex coronary artery disease, usually in association with significant right coronary artery disease. The pattern of tall, wide R waves in leads V1 or V2 (RV1,2) in patients with inferior infarction is highly predictive of at least two vessel coronary artery disease.

T loop in posterior myocardial infarction: a useful clue to vectorcardiographic diagnosis

In order to differentiate posterior (posterolateral) myocardial infarction (PMI) from the anterior shift of the QRS loop in "normal variant" cases using a vectorcardiogram, the T loop as well as the QRS loop in the transverse plane (TP) were analyzed in 34 elderly Japanese males with angiographically-proven PMI and in 197 elderly Japanese males with normal coronary arteries and ventricles. T loops in the TP were longer, narrower and more anterior in PMI cases. After this analysis, we propose new criteria for PMI: (A and B) A: maximal T vector equal or anterior to 60 degrees in TP B: at least two of the following three: maximal QRS voltage/maximal T voltage in TP equal to or less than 3.0; QRS-T angle equal to or less than 75 degrees in TP; width/length of T equal to or less than 0.15 in TP. These new criteria for PMI are more specific (p less than 0.01) and more sensitive (p less than 0.05) than Hoffman's criteria.

Is anterior ST depression with acute transmural inferior infarction due to posterior infarction? A vectorcardiographic and scintigraphic study

The hypothesis that anterior ST segment depression represents concomitant posterior infarction was tested in 49 patients admitted with a first transmural inferior myocardial infarction. Anterior ST depression was defined as 0.1 mV or more ST depression in leads V1, V2 or V3 on an electrocardiogram recorded within 18 hours of infarction. Serial vectorcardiograms and technetium pyrophosphate scans were obtained. Eighty percent of the patients (39 of 49) had anterior ST depression. Of these 39 patients, 34% fulfilled vectorcardiographic criteria for posterior infarction, and 60% had pyrophosphate scanning evidence of posterior infarction. Early anterior ST depression was neither highly sensitive (84%) nor specific (20%) for the detection of posterior infarction as defined by pyrophosphate imaging. Of patients with persistent anterior ST depression (greater than 72 hours), 87% had posterior infarction detected by pyrophosphate scan. In patients with inferior myocardial infarction, vectorcardiographic evidence of posterior infarction correlated poorly with pyrophosphate imaging data. Right ventricular infarction was present on pyrophosphate imaging in 40% of patients with pyrophosphate changes of posterior infarction but without vectorcardiographic evidence of posterior infarction. It is concluded that: 1) the majority of patients with acute inferior myocardial infarction have anterior ST segment depression; 2) early anterior ST segment depression in such patients is not a specific marker for posterior infarction; and 3) standard vectorcardiographic criteria for transmural posterior infarction may be inaccurate in patients with concomitant transmural inferior myocardial infarction or right ventricular infarction, or both.

Prognostic value of Q waves, R/S ratio, loss of R wave voltage, ST-T segment abnormalities, electrical axis, low voltage and notching: correlation of electrocardiogram and left ventriculogram

Data on the correlation of left ventricular segmental wall motion and electrocardiographic findings are, except for Q waves and ST segment elevation, still controversial. Therefore, in addition to Q waves and ST segment elevation, eight features of the electrocardiogram were studied in 265 patients, 61 with normal coronary arteries and 204 with coronary artery disease. Patients with a QRS duration of 0.12 second or greater were excluded. Left ventricular wall motion was assessed in the 30 degrees right anterior oblique and the 60 degrees left anterior oblique projections and analyzed by the Stanford method and a modification of that method, respectively. Asynergy of a particular segment correlated well with the presence of Q waves in the corresponding electrocardiographic lead or leads, but was also found in other segments. There was a significant (p less than 0.001) correlation between the number of leads with Q waves and the degree of extension of asynergy. The R/S ratio in lead V1 and Q waves in lead V6 appeared to be the most informative about the posterior wall. Loss of R wave voltage had a lower predictive value for segmental asynergy than did Q waves in the same lead. Among patients with electrocardiographic findings of an infarct, asynergy was found in 83 to 94%. Patients having Q waves in combination with ST segment elevation manifested more severe asynergy than did patients whose Q waves were not associated with ST elevation. New data are presented for lateral and posterior infarction. Patients having left-axis deviation, low voltage and QRS notching had severe asynergy.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic value of electrocardiogram and vectorcardiogram in postinfarction ventricular asynergy

The ability of ECG-VCG to predict the severity of postinfarction LV asynergy was evaluated in 152 patients with previous myocardial infarction who underwent left cineventriculography in the right anterior oblique view. Various ECG and VCG signs were examined in order to predict the existence of severe asynergy in general (dyskinesia or akinesia or severe hypokinesia) and of dyskinesia in particular. In patients with inferior myocardial infarction (Group A) persistent ST segment elevation was the only specific ECG sign (100%) of severe asynergy; it had a poor sensitivity (6.2%). Four frontal VCG signs (presence of terminal bite, y- greater than 0.18 mV, maximum early superior vector along x axis = MESV greater than or equal to 1.3 mV, duration of initial superior forces = DISF greater than 50 msec) increased the sensitivity of the ECG-VCG method to 75.8% while maintaining a 100% specificity. Regarding the diagnosis of dyskinesia, only the ECG sign of persistent ST segment elevation and the VCG sign of y- greater than or equal to 0.3 mV had a 100% specificity. The sensitivity of the ECG-VCG method was 33.3% (16.6% ECG and 16.6% VCG). In patients with anterior myocardial infarction (Group B), concerning the diagnosis of severe asynergy, the ECG signs of sigma ST greater than 3 mm in anterior leads; pathologic Q wave in four or more anterior leads (including D1 and aVL); and the presence of LAH or LAH + RBBB, had a 100% specificity and a good sensitivity (60.5%). The VCG sign of a narrow horizontal QRS loop increased the sensitivity of the ECG-VCG method to 71% while maintaining a 100% specificity. As for the diagnosis of dyskinesia, the ECG signs with a 100% specificity were sigma ST greater than or equal to 5 mm in anterior leads, a pathologic Q wave in more than five anterior leads (including I and a VL) and RBBB + LAH; these variables had a sensitivity of 48.3%. The VCG sign of a narrow horizontal QRS loop increased the sensitivity of the ECG-VCG method to 79.3% while maintaining a 100% specificity. In patients with inferior plus anterior myocardial infarction (Group A + B) the signs mentioned above for each group were evaluated, confirming a 100% specificity. Regarding the diagnosis of severe asynergy, the ECG signs had a sensitivity of 61.3%, while VCG increased the sensitivity of the ECG-VCG method to 90.3%.(ABSTRACT TRUNCATED AT 400 WORDS)

Significance of the upright T wave in precordial lead V1 in adults with coronary artery disease

To determine the prevalence and evaluate the significance of an upright T wave in precordial lead V1, the 12 lead electrocardiograms of 218 patients undergoing diagnostic catheterization for the evaluation of chest pain were reviewed. Of this total, 184 patients had severe coronary artery disease (greater than or equal to 75% luminal narrowing) and 34 patients had minimal or no coronary artery disease. An upright T wave in lead V1 (greater than or equal to 0.15 mV) was present in 3 subjects (9%) without coronary artery disease; in 19 (20%) of 96 patients with one vessel disease; in 14 (27%) of 51 patients with two vessel disease and in 13 (35%) of 37 patients with three vessel disease. Among the patients with one vessel disease, an upright T wave was more frequent in patients with left circumflex artery disease than in patients with left anterior descending or right coronary artery disease (probability [p] less than 0.001). Among patients with two vessel disease, an upright T wave was more frequent in patients with disease of the right coronary and left circumflex coronary arteries than in the remaining patients (p less than 0.005). It is concluded that an upright T wave in precordial lead V1 is common in patients with isolated left circumflex artery disease but is rare in those with isolated left anterior descending artery disease. Similarly, in patients with multivessel disease, an upright T wave is common when the left circumflex artery is diseased. This finding, along with other noninvasive tests, may prove useful in patient evaluation.

Accuracy of various techniques in the measurement of the duration of the Q wave: a possible source of error in diagnosing myocardial infarction by electrocardiography

The method of measuring the width of the Q wave on electrocardiogram is one of the variables contributing to conflicting findings regarding the accuracy of the ECG in the diagnosis of myocardial infarction. This study assesses the accuracy of a variety of methods of measuring the width of the Q wave recorded by direct-writing electrocardiographic instruments. The assessment was made by comparing the width of the Q wave as inscribed by thermal direct-writing electrocardiographs to the width of the Q wave as measured from an oscilloscopic display, the latter representing the "true" width of the Q wave. The measurement of the width as obtained from the upper edge of the tracing obtained with direct-writing electrocardiographs underestimated the true width of the Q wave, while the opposite was the case by measuring the width along the lower edge of the tracing. The most reliable ways to obtain the true width of the Q wave are: (1) to average the measurements as obtained along the upper and lower edge, (2) to measure the width along an ideal line in the middle of the tracing, or (3) to measure the width along the trailing edge of the deflection.

Improved electrocardiographic criteria for the diagnosis of inferior myocardial infarction

New electrocardiographic (ECG) criteria for the diagnosis of inferior myocardial infarction (IMI) are proposed. The criteria are based upon the relationships between portions of the vectorcardiographic (VCG) QRS loop in the frontal plane and the corresponding portions of the ECG QRS complexes recorded in leads II and III. The application of the proposed criteria requires that the tracings be obtained with three-channel ECG machines so that the temporal relationships between the QRS complexes in lead II and those in simultaneously recorded lead III can be inspected. This type of analysis of the ECG permits important features of the contour of the VCG QRS loop to be predicted. The proposed ECG criteria for the diagnosis of IMI are: in the absence of counterclockwise rotation in the frontal plane, (1) Q waves of 30 msec or longer in lead II or (2) regression of initial inferior forces from lead III to lead II. The proposed ECG criteria were evaluated in an initial series of 333 patients and, using a blind experimental design, in a confirmatory series of 94 patients. The performance of the proposed criteria was statistically superior to that of two sets of ECG Q-wave criteria and comparable to that of the VCG criteria of Starr et al.

[Pattern quantification of coronary artery stenosis by computerized analysis of multiple ECG parameters (author's transl)]

Coronary angiograms of 200 patients with coronary artery disease were studied. The distribution of stenoses was analyzed and classified utilizing a special score, taking into account coronary supply pattern (according to Baroldi et al.), localization and severity of stenosis, as well as collateralization. Frank-lead vectorcardiograms were obtained and analyzed by computer. 140 scalar and spatial vector parameters were evaluated. A statistical comparison was made in 36 patients with highgrade stenoses of the left anterior descending branch of the left coronary artery with 37 patients without such vascular narrowing. Utilizing 4 ECG-parameters a mathematical formula can be derived which separates the two groups. Another equation based on 5 parameters allows the calculation of a score from conventional electrocardiograms. By discriminance analysis a specificity of 78.4% and a sensibility of 77.8 in prediction results for the group with stenosis. For the control group a specificity of 75.7% and a sensibility of 77.8% were computed. Correlation between the score obtained by calculation on the one hand, and the score derived from direct analysis of the arteriogram was highly significant with an r = 0.796.

Revaluation of the vectorcardiographic criteria in cases of myocardial infarction: a comparative study of the vectorcardiogram, the left ventriculogram and the scintigram

The results of vectorcardiograms were compared with those of the left ventriculograms and scintigrams with thallium-201 in cases of myocardial infarction to confirm the vectorcardiographic criteria of the present authors. The percentage of agreement between the VCG and scintigram was 82.5% and higher than the percentage of agreement between the VCG and the left ventriculogram. The percentage of disagreement between the negative finding in the VCG and the positive finding in the scintigram was 5.1% and consequently, a close relation was found between the VCG and scintigram. However, as the possibility of infarction was high in cases in which the scintigram finding was positive, the vectorcardiographic criteria in cases in which the VCG findings were negative were rechecked and partially corrected. Consequently the percentage of negative findings were decreased to 3.2%. Our next step was to perform the following prospective study which confirmed that the disagreement found in the corrected criteria (1.0%) was in fact less than what had been observed in the initial criteria (5.0%). Accordingly, it can be concluded that the corrected vectorcardiographic criteria in myocardial infarction may be the more reliable and useful in determining the location of the infarcted area.

XYZ data interpreted by a 12-lead computer program using the derived electrocardiogram

The 12-lead electrocardiogram (ECG) derived from the Frank xyz signals was compared with the conventional 12-lead ECG using the Telemed computer system. In 100 cases studied. Telemed's interpretations were essentially similar in 77, but substantially different in 23. In the 23 cases, interpretations of the derived tracings tended to be more accurate in 14 cases, and less accurate in four cases. In the diagnosis of infarction the probability that the interpretation of the derived tracing will be correct more often was 90%. The better performance may have been related to closer agreement with the vectorcardiogram (VCG). As a substitute for the conventional ECG, the derived ECG offers the prospect of a computerized system that is more practical and more versatile than most currently used systems.

Predictive value of electrocardiographic patterns in localizing left ventricular asynergy in coronary artery disease

Transmural myocardial infarction by ECG (ECG-MI) was correlated with left ventricular asynergy by biplane left cineventriculography in 200 patients with coronary artery disease. The ability of individual ECG-MI patterns to predict and correctly localize asynergy was: anterior--98 per cent (43 of 44), inferior--82 per cent (36 of 44), true posterior--73 per cent (11 of 15). Of various combinations of criteria for true posterior ECG-MI, the pattern of an R wave and upright T wave in Lead V1 was most predictive of posterior asynergy--80 per cent (8 of 10). The LAO projection demonstrated a wall motion abnormality not appreciated in the RAO in 8 per cent (10 of 122) of cases of inferoposterior asynergy and enhanced assessment of asynergy in 30 per cent (36 of 122) of cases. It is concluded that: (1) ECG-MI has a high predictive accuracy for left ventricular asynergy, (2) an R-wave and upright T wave in Lead V1 is the best ECG predictor of posterior asynergy, and (3) the LAO projection makes an important contribution to the assessment of regional asynergy in coronary artery dieseas.

Electrocardiographic poor R wave progression. I: correlation with the Frank vectorcardiogram

Fifty-six patients with "poor R wave progression" (PRWP) on the electrocardiogram (ECG) were studied by Frank vectorcardiography in an attempt to define discriminators for subgroups. Criteria were prospectively applied to a test group with achievement of comparable sensitivity and specificity. Four subgroups were identified in the patients with PRWP: Group I - anterior myocardial infarction (AMI) (20/56, 35%); Group II - left ventricular hypertrophy (LVH) (8/56, 14%); Group III - right ventricular hypertrophy (RVH) (7/56, 13%); AND Group IV - leftward axis (LA) (21/56, 38%). The best discriminator for vectorcardiogram (VCG) AMI was RV3 less than or equal to 1.5mm or R1 less than or equal to 4.0mm (18/20, 90% sensitivity; 26/36, 72% specificity). RVH and LVH were identified by R1 less than or equal to 4.0mm and S1 greater than or equal to 1.0mm and standard LVH voltage criteria respectively. Group IV patients (PRWP without VCG criteria for AMI, LVH or RVH) were identified by exclusion. "Reversed R wave progression" (RRWP) was more specific for AMI than was simple PRWP. The same discriminators, however, were applicable. It is clinically useful to note that 72% (26/36) of patients with either PRWP or RRWP who did not exhibit VCG AMI could be identified by 12 lead ECG with only 2/28 (7%) VCG false negative AMI.

A computer system automatic analysis of vectorcardiograms

This computer system performs the analysis of orthogonal electrocardiograms for vectorcardiographic (VCG) display and classification. The data acquisition can be performed 'on-line' with the complete analysis in 'real-time', or off-line by processing a magnetic tape. The original computational methods for beat averaging and wave recognition are described. Some features, such as the quality of the visual display of the VCG traces, the availability of a measurement matrix allowing the quantitative analysis of the VCG and the use of a data bank for storage, retrieval and statistical studies make this system very efficient for clinical purposes, introducing the concept of 'Computer Assisted Vectorcardiography'.