Correlation of vectorcardiogram and electrocardiogram with coronary arteriogram

Present results and methods of vectorcardiographic diagnostics of ischemic heart disease

This article presents an overview of existing approaches to perform vectorcardiographic (VCG) diagnostics of ischemic heart disease (IHD). Individual methodologies are divided into categories to create a comprehensive and clear overview of electrical cardiac activity measurement, signal pre-processing, features extraction and classification procedures. An emphasis is placed on methods describing the electrical heart space (EHS) by several features extraction techniques based on spatiotemporal characteristics or signal modelling and signal transformations. Performance of individual methodologies are compared depending on classification of extent of ischemia, acute forms - myocardial infarction (MI) and myocardial scars localization. Based on a comparison of imaging methods, the advantages of VCG over the standard 12-leads ECG such as providing a 3D orthogonal leads imaging, better performance, and appropriate computer processing are highlighted. The issues of electrical cardiac activity measurements on body surface, the lack of VKG databases supported by a more accurate imaging method, possibility of comparison with the physiology of individual cases are outlined as potential reserves for future research.

Representative QRS loop of the VCG record evaluation

Introduction: This study proposes an algorithm for preprocessing VCG records to obtain a representative QRS loop. Methods: The proposed algorithm uses the following methods: Digital filtering to remove noise from the signal, wavelet-based detection of ECG fiducial points and isoelectric PQ intervals, spatial alignment of QRS loops, QRS time synchronization using root mean square error minimization and ectopic QRS elimination. The representative QRS loop is calculated as the average of all QRS loops in the VCG record. The algorithm is evaluated on 161 VCG records from a database of 58 healthy control subjects, 69 patients with myocardial infarction, and 34 patients with bundle branch block. The morphologic intra-individual beat-to-beat variability rate is calculated for each VCG record. Results and Discussion: The maximum relative deviation is 12.2% for healthy control subjects, 19.3% for patients with myocardial infarction, and 17.2% for patients with bundle branch block. The performance of the algorithm is assessed by measuring the morphologic variability before and after QRS time synchronization and ectopic QRS elimination. The variability is reduced by a factor of 0.36 for healthy control subjects, 0.38 for patients with myocardial infarction, and 0.41 for patients with bundle branch block. The proposed algorithm can be used to generate a representative QRS loop for each VCG record. This representative QRS loop can be used to visualize, compare, and further process VCG records for automatic VCG record classification.

Reliable Detection of Myocardial Ischemia Using Machine Learning Based on Temporal-Spatial Characteristics of Electrocardiogram and Vectorcardiogram

Background: Myocardial ischemia is a common early symptom of cardiovascular disease (CVD). Reliable detection of myocardial ischemia using computer-aided analysis of electrocardiograms (ECG) provides an important reference for early diagnosis of CVD. The vectorcardiogram (VCG) could improve the performance of ECG-based myocardial ischemia detection by affording temporal-spatial characteristics related to myocardial ischemia and capturing subtle changes in ST-T segment in continuous cardiac cycles. We aim to investigate if the combination of ECG and VCG could improve the performance of machine learning algorithms in automatic myocardial ischemia detection.

Methods: The ST-T segments of 20-second, 12-lead ECGs, and VCGs were extracted from 377 patients with myocardial ischemia and 52 healthy controls. Then, sample entropy (SampEn, of 12 ECG leads and of three VCG leads), spatial heterogeneity index (SHI, of VCG) and temporal heterogeneity index (THI, of VCG) are calculated. Using a grid search, four SampEn and two features are selected as input signal features for ECG-only and VCG-only models based on support vector machine (SVM), respectively. Similarly, three features (S_I, THI, and SHI, where S_I is the SampEn of lead I) are further selected for the ECG + VCG model. 5-fold cross validation was used to assess the performance of ECG-only, VCG-only, and ECG + VCG models. To fully evaluate the algorithmic generalization ability, the model with the best performance was selected and tested on a third independent dataset of 148 patients with myocardial ischemia and 52 healthy controls.

Results: The ECG + VCG model with three features (S_I,THI, and SHI) yields better classifying results than ECG-only and VCG-only models with the average accuracy of 0.903, sensitivity of 0.903, specificity of 0.905, F1 score of 0.942, and AUC of 0.904, which shows better performance with fewer features compared with existing works. On the third independent dataset, the testing showed an AUC of 0.814.

Conclusion: The SVM algorithm based on the ECG + VCG model could reliably detect myocardial ischemia, providing a potential tool to assist cardiologists in the early diagnosis of CVD in routine screening during primary care services.

The Vectorcardiogram and the Main Dromotropic Disturbances

Until the mid-1980s, it was believed that the vectorcardiogram (VCG) presented a greater specificity, sensitivity and accuracy in comparison to the 12-lead electrocardiogram (ECG), in the cardiology diagnosis. Currently, the VCG still is superior to the ECG in specific situations, such as in the evaluation of myocardial infarctions when associated with intraventricular conduction disturbances, in the identification and location of accessory pathways in ventricular preexcitation, in the differential diagnosis of patterns varying from normal of electrical axis deviation, in the evaluation of particular aspects of Brugada syndrome, Brugada phenocopies, concealed form of arrhythmogenic right ventricular cardiomyopathy and zonal or fascicular blocks of the right bundle branch on right ventricular free wall.VCG allows us to analyze the presence of left septal fascicular block more accurately than ECG and in the diagnosis of the interatrial blocks and severity of some chambers enlargements. The three-dimensional spatial orientation of both the atrial and the ventricular activity provides a far more complete observation tool than the linear ECG. We believe that the ECG/VCG binomial simultaneously obtained by the technique called electro-vectorcardiography (ECG/VCG) brought a significant gain for the differential diagnosis of several pathologies. Finally, in the field of education and research, VCG provided a better and more rational tridimensional insight into the electrical phenomena that occurs spatially, and represented an important impact on the progress of electrocardiography.

Q waves and coronary artery disease

In a consecutive series of 234 patients admitted for selective coronary arteriography, 78 had pathological Q waves. In 32 of these 78 patients, ECG showed left ventricular hypertrophy, QRS duration of greater than or equal to 0.12 sec, incomplete left bundle branch block, or left axis deviation. Fourteen (44%) of these 32 patients had coronary artery disease (CAD), while 40 (87%) of the remaining 46 patients without these ECG changes had CAD (p less than 0.0005). Among the 46 patients, 34 of 35 with angina pectoris had CAD compared to 6 of 11 without angina pectoris (p less than 0.01). Our study thus shows that Q waves may be reliable predictors of CAD especially in patients with angina pectoris.

A critique of the Women's Health Initiative hormone therapy study

OBJECTIVE

This review critiques The Women's Health Initiative (WHI) study, focusing on aspects of the study design contributing to the adverse events resulting in the study's discontinuation.

CONCLUSION(S)

Two aspects of the design contributed to the adverse events: [1] The decision to administer continuous combined conjugated equine estrogen (CEE)/medroxyprogesterone acetate (MPA) or E alone as a standard regimen to a population with little previous hormonal treatment, ranging in age from 50-79 years, who, because of their age, were predisposed to coronary and cerebral atherosclerosis. [2] Selection of an untested regimen of continuous combined CEE plus MPA, which we hypothesize, negated the protective effect of E on the cardiovascular and cerebrovascular systems. Multiple observational studies that preceded the WHI study concluded that the use of E alone and E plus cyclic (not daily) progestin combination treatments initiated in early menopause had beneficial effects. The therapeutic regimens resulted in prevention of atherosclerosis and reductions in coronary artery disease mortality. It is our conclusion that the WHI hormonal replacement study had major design flaws that led to adverse conclusions about the positive effects of hormone therapy. An alternative hormonal regimen is proposed that, on the basis of data supporting its beneficial cardiovascular effects, when initiated appropriately in a population of younger, more recently menopausal women, has promise to yield a more favorable risk/benefit outcome.

Electrocardiographic and coronary arteriographic correlations during acute myocardial infarction

One hundred fifty-two patients underwent cardiac catheterization and coronary arteriography within 6.3 +/- 6.0 hours from the onset of acute myocardial infarction (AMI). All had standard 12-lead electrocardiograms recorded within 1 hour of cardiac catheterization. The electrocardiographic abnormalities present were correlated with the infarct-related artery as determined by coronary arteriography. ST-segment elevation was the most common finding in patients with the left anterior descending (LAD) or right coronary artery as the infarct-related artery. ST-segment depression was the most common abnormality in patients with the left circumflex (LC), artery as the infarct-related artery. A classic pattern of anteroseptal AMI was seen in 93% of all patients with the LAD as the infarct-related artery. A classic pattern of inferior AMI was seen in 53% of patients with right of LC narrowing taken as 1 group. The pattern of true posterior and isolated lateral wall AMI in the absence of classic changes in the inferior leads was highly specific and predictive of LC narrowing. In contrast, the pattern of an inferior wall AMI, in the absence of true posterior or lateral wall changes, was highly specific and predictive of right coronary artery narrowing. Fifty-six percent of patients with LC artery as the infarct-related artery presented with non-classic electrocardiographic abnormalities. The electrocardiographic patterns in patients with subtotal occlusions were similar to those of patients with total occlusions. Thus, the electrocardiogram obtained in the first few hours of AMI is reliable in localizing the LAD as the infarct-related artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Implications of normal exercise electrocardiographic results in patients with angiographically documented coronary artery disease. Correlation with left ventricular function and myocardial perfusion

The purpose of this study was to examine the incidence and implications of false-negative exercise electrocardiographic results among 216 consecutive patients with angiographically documented coronary artery disease (50 percent diameter narrowing or greater of one or more vessels). Exercise electrocardiography gave negative (false-negative) results in 23 patients and positive (true-positive) results in 102 patients, and were nondiagnostic in the rest. Exercise thallium-201 imaging was performed in 88 patients. The extent of coronary artery disease was quantitated by a scoring system that takes into consideration the degree and site of narrowing in the major vessels and their branches. The exercise heart rate was higher in patients with false-negative than in patients with true-positive exercise electrocardiographic results (161 +/- 18 versus 133 +/- 24 beats per minute, mean +/- SD; p less than 0.0001). Q-wave infarction was present in two patients (9 percent) with false-negative and 20 patients (20 percent) with true-positive exercise electrocardiographic results (p = NS); left ventricular asynergy at rest was observed in 13 patients (57 percent) with false-negative and in 74 patients (74 percent) with true-positive results (p = NS). Patients with false-negative results had less extensive coronary disease than did patients with true-positive results (score 5.8 +/- 3.6 versus 9.2 +/- 5.0; p = 0.0025). Angina during exercise was less frequent in patients with false-negative results (p less than 0.01). Abnormal exercise thallium-201 images were seen in 15 of 20 patients (75 percent) with false-negative results and in 56 of 68 patients (82 percent) with true-positive results (p = NS). It is concluded that (1) false-negative exercise electrocardiographic results are infrequent (10 percent) among patients with coronary artery disease and are associated with less extensive coronary artery disease; (2) the frequency of Q-wave infarction and left ventricular asynergy is the same in patients with false-negative results as in patients with true-positive exercise electrocardiographic results; (3) exercise thallium images can identify 75 percent of patients with coronary disease and false-negative results of exercise electrocardiography.

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.

Vectorcardiographic diagnosis of diaphragmatic myocardial infarction

Vectorcardiograms of 31 patients with arteriographic evidence of complete occlusion of the right coronary artery were analyzed in order to evaluate and attempt to improve the vectorcardiographic criteria for the diagnosis of an old diaphragmatic myocardial infarction. The electrocardiogram showed no evidence of a diaphragmatic infarction in 48 percent of these patients. This was advantageous, since the intent of the study was to develop vectorcardiographic criteria that exceeded the capability of the electrocardiogram. The criteria that appeared optimal were: (1) an instantaneous 0.02 second QRS vector equal or superior to 315 degrees (-45 degrees) in the sagittal plane, or (2) ratio of voltages of 0 to left x-intercept to maximal QRS vector greater than 0.22 in the frontal plane. These criteria identified a diaphragmatic infarction in 77 percent of patients (24 of 31) with complete occlusion of the right coronary artery. There were no false positive findings in 40 normal subjects. A group of criteria previously defined by others, based upon rotation, contour of initial forces, duration of superior forces relative to the contour, magnitude of 0 to left x-intercept, and maximal QRS vecotr, was equally sensitive. Other previously defined criteria were less sensitive. The criteria developed in this study, when tested in 22 patients with prominent Q waves indicative of an old diaphragmatic infarction, properly diagnosed the infarction in all 22 patients. All previous criteria also successfully detected infarction in these patients. However, the new criteria identified a greater number of patients without electrocardiographic evidence of diaphragmatic infarction than were identified with previously defined vectorcardiographic criteria unless the latter were complex.

Correlation of polarcardiographic criteria for myocardial infarction with arteriographic and ventriculographic findings (substantiation of transmural and presentation of non-transmural criteria)

Sensitivity and specificity of polarcardiographic criteria for myocardial infarction were compared with those of electrocardiographic criteria in 108 patients with chest pain syndromes who were referred for coronary arteriography and left ventriculography. With the combination of total occlusion of at least one coronary artery and abnormal systolic contraction of at least part of the left ventricle as the best available documentation of myocardial disease, sensitivity and specificity were 70% and 67%, respectively, using electrocardiographic criteria and 80% and 73% using polarcardiographic criteria, for both anterior and inferior myocardial infarction. Another polarcardiographic criterion--rightward shift in R latitude at 10 msec after onset of QRS--occurred concurrently with vessel occulusion in 16 of 17 patients (94%), in four of whom this was the only objective evidence of myocardial infarction, and three of whom there was no manifest abnormality of wall contraction. This criterion is considered evidence of non-transmural myocardial infarction, probably in the subendocardial layer near the apex of the left ventricle. When such evidence is added, sensitivity of polarcardiographic criteria increased to 84%, and specificity decreased to equal that of the electrocardiographic criteria (67%).

Correlation of abnormal Q waves, coronary pathology, and ventricular contractility

Four hundred and ninety-two patients with coronary artery disease underwent analysis of their electrocardiograms, coronary arteriograms, and ventriculograms. Significant Q-waves were correlated with critical coronary occlusions (greater than or equal 75 per cent obstruction) and ventricular contractility. It was found that Q-waves correlate equally well with ventriculographic abnormalities and critical coronary occlusions. The Q-wave correlation varied from 77 to 87 per cent, depending on the area of myocardium under consideration, except for true posterior myocardial infarction, which correlated 55 per cent with ventriculographic abnormalities and 55 per cent with critical coronary occlusions. Significant Q-waves in Leads II, III, and aVF are better indicators of ventriculographic abnormality than in Leads III and aVF alone, whereas Q-waves in the latter two leads are more definitive than in Lead III alone. Patients who have critical coronary occlusions and normal electrocardiograms have normal ventriculograms in 71 to 78 per cent of the cases, again depending on the area of the myocardium under consideration. Thus, the normal electrocardiogram correlates better with the ventriculogram than with coronary pathology. The abnormal electrocardiogram correlates equally well with both.

Diagnostic value of vectorcardiogram in strictly posterior infarction

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