Special value of the vectorcardiogram in pediatric cardiology.
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Arrhythmias, Cardiac↗
Biomedical subjects
C R Brohet
Publications and source records attributed to C R Brohet.
Evaluation of ECG interpretation results obtained by computer and cardiologists.
In an international project investigators from 25 institutes are trying to establish a common reference library and evaluation methods for testing the diagnostic performance of various ECG computer programs and of cardiologists, based on ECG-independent clinical information. A first set of 500 validated ECGs was collected and analyzed by fifteen different computer programs and nine cardiologists, seven of who analysed the ECG and five the VCG. A coding scheme was used to map individual diagnostic statements onto a common set. Combined program and referee results were obtained by weighted averaging. Preliminary results indicate that the classification accuracy of several programs can still be improved. However, it was also apparent that the results of the best 12-lead ECG computer programs proved to be almost as accurate as the best of seven cardiologists in classifying seven main disease categories, i.e., normal, left, right and biventricular hypertrophy, anterior, inferior and combined myocardial infarction. Evaluation of rhythm statements and conduction disturbances was not included in the study. The data collection is still being pursued in order to reach over 1,000 cases. In this way a common diagnostic database is being established for comparative testing of diagnostic computer programs. This should lead to consumer protection and improve the accuracy and reliability of computerized electrocardiography.
Cardiovascular Diseases↗
Methodology of ECG interpretation in the Louvain program.
The Louvain program performs the analysis and interpretation of the vectorcardiogram (VCG) to increase the clinical utility of ECG analysis. Among its original features, there are (1) a high-resolution vector-loop display for visual analysis, (2) quantitative analysis of the spatial VCG using age-sex stratified limits, (3) separate software for adult and pediatric series and (4) complementary deterministic and statistical methods of diagnostic classification. Using objective, ECG-independent evidence as a reference standard, the Louvain program has shown satisfactory levels of diagnostic accuracy in most basic categories. However, its usefulness is especially marked in "borderline" or "complex" situations, where the 12-lead ECG cannot provide a clear answer. It corresponds to the concept of "computer-assisted ECG interpretation" as opposed to "computer ECG analysis".
Adult↗
Comparison between two classification systems of the electrocardiogram in epidemiologic investigations. The Minnesota code and the Washington D.C., code.
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Adult↗
Non-invasive data provide independent prognostic information in patients with chest pain without previous myocardial infarction: findings in male patients who have had cardiac catheterization.
From 1978 to 1985, 470 consecutive male patients with complaints of chest pain underwent a maximal exercise test with a thallium scan and coronary angiography (CA). Patients with a history of myocardial infarction (MI) were excluded. During the follow-up (from 12 to 96 months), 32 patients died and 30 had a non-fatal MI. Survival (SR) and event-free rates (EFR) were estimated by actuarial methods; the influence of non-invasive and invasive variables were examined in univariate and multivariate models using Cox analysis. The five-year SR was 89% and EFR was 81%. Among historical data, age (less than 0.001), type of complaints (less than 0.01) and pretest likelihood of CAD (less than 0.01) were univariate predictors of EFR; by multivariate analysis, age was the only significant predictor (less than 0.001). Most of the maximal-exercise (MEX) test data were good univariate predictors; by multivariate analysis, workload (less than 0.001) and the maximal-exercise test score (less than 0.001) were the significant predictors. From history and maximal-exercise test data, multivariate analysis indicated that the prognostic information was given by age (less than 0.05) and maximal-exercise test score (less than 0.001). Among the invasive data, the number of diseased vessels (less than 0.001) and ejection fraction were the predictors. The combination of invasive and non-invasive data indicated that age, MEX score, number of diseased vessels and ejection fraction contributed significantly and independently to the estimation of prognosis. Among 242 patients with two or three diseased vessels, the prognosis was determined by the maximal workload (less than 0.01); ejection fraction (less than 0.07) was no longer significant.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
[Left ventricle in Noonan's syndrome. Electro-vecto-echo and angiocardiographic aspects].
The electrocardiographic features of Noonan's syndrome have been known for several years, but the discordance between these electrical findings and the underlying haemodynamic disorders remains unexplained. In an attempt to elucidate the genesis of electrical abnormalities, we present here a retrospective study of 14 children with Noonan's disease, aged from a few days to 16 years and evaluated by electrocardiography, vectography, one- or two-dimensional echocardiography, angiography and His bundle electrophysiology. The electrocardiographic abnormalities observed concerned ventricular depolarization and intracardiac electric conduction with, notably, a QRS axis directed towards the right upper part of the electric field and a first degree infra-hisian atrioventricular block (His bundle potentials). Vectography showed in some cases an image of inferior pseudo-necrosis due to the absence of initial inferior forces; this image is highly characteristic. In other cases the QRS loop showed an image of left segmental block which is unusual in this type or cardiac pathology (pulmonary stenosis with or without atrial septal defect of the ostium secundum type).
Adolescent↗
The normal pediatric Frank orthogonal electrocardiogram: variations according to age and sex.
Quantitative computerized analysis of QRS and ST-T parameters of the Frank orthogonal electrocardiogram and vectorcardiogram was undertaken in a large series of 1317 normal infants, children and adolescents stratified according to age and sex. This study confirms the influence of these two constitutional variables, age and sex, over the normal VCG in the whole time span between birth and late adolescence. As children mature, the mid-portion of the spatial QRS loop shifts leftward and posteriorly with relatively little change in the initial and terminal vectors. The spatial T loop shifts anteriorly but at a different rate in males and in females. Unidirectional changes in many amplitude parameters are observed until age 19 in males whereas in females these changes stop earlier or even show a reverse trend around puberty, leading to more important differences between adolescent males and females. Sex-related differences are the most marked for parameters representing the repolarization process. Infants under six months of age form a distinct group with larger dispersions and more disparate variations in the values of vectorcardiographic parameters than in older children. In the newborn period larger sample size might be necessary in order to reduce the normal ranges of vectorcardiographic parameters.
Adolescent↗
The normal pediatric Frank orthogonal electrocardiogram: influence of weight, height and chest circumference.
The influence of body weight, height and chest circumference on the pediatric Frank vectorcardiogram (VCG) was investigated in a population of 1317 normal infants, children and adolescents. Simple linear regression analysis showed that 94, 96 and 57 VCG variables were significantly correlated with weight, height and chest circumference, respectively. These numbers were reduced to 10, 18 and 6 VCG variables after a stepwise multiple correlation analysis. The relationship between the VCG and the somatic variables was also studied in ten different age/sex subgroups. Simple regression analysis showed a residual significant correlation between the VCG and all three somatic variables in each group. The multiple correlation analysis allowed us to define a minimum set of VCG variables, from one to six, which could explain all the variation produced by the somatic variables. The coefficient of multiple correlation between VCG and weight was the highest in babies 0 to 6 months old (R = 0.73). For height, the strongest correlation was found in females two to five years old (R = 0.76). In subjects older than two years of age, the correlation between chest circumference and VCG (R = 0.30 to 0.69) was weaker than between VCG and pediatric VCG after stratification for age and sex, especially in the youngest groups.
Adolescent↗
Diagnostic value of computerized exercise testing in men without previous myocardial infarction. A multivariate, compartmental and probabilistic approach.
The value of exercise testing for the diagnosis of coronary artery disease is disputed but very few studies have taken advantage of all recent improvements, namely computer averaging of the ECG signals, multivariate analysis of the data, a compartmental diagnostic approach and probabilistic interpretation of the results. These methods were tested in a group of 387 men who had a computer-assisted multistage maximal exercise test; none had a history of myocardial infarction. In 284 symptomatic patients, the diagnosis was made by arteriography; 103 ostensibly healthy men were also included. The computer-averaged ECG signals (X, Y, Z) recorded at maximal exercise, maximal heart rate, blood pressure and workload, and the onset of angina pectoris during exercise were submitted to a multivariate stepwise discriminant analysis. The pretest likelihood for CAD was calculated from age and history; the post-test likelihood was calculated from Bayes' theorem and the average information content of several diagnostic methods was assessed in categorical and compartmental models. By multivariate analysis, 5 variables collected at maximal exercise were selected, namely the heart-rate, the ST60 segment level, the onset of angina during the test, the workload and the slope of the ST segment in lead X. The average information content of the analysis using 5 variables was 44% in a categorical model versus 55% in a compartmental model (P less than 0.001). For comparison, the information content of the analysis using the ST60 segment level alone was only 16% in the categorical model and 27% in the compartmental model. The clinical value of these diagnostic methods (categorical versus compartmental, univariate versus multivariate) was assessed by a probabilistic classification of the patients. The classification provided by the analysis of the ST60 segment changes was barely better than that one provided by the simple history. The probabilistic use of a multivariate and compartmental analysis of the data led to a significantly better and more accurate classification of the patients (83% of correct classification).
Adult↗
Computer interpretation of pediatric orthogonal electrocardiograms: statistical and deterministic classification methods.
Statistical multivariate and conventional deterministic methods of computerized interpretation of the electrocardiogram (ECG) were compared in the analysis of 1711 pediatric orthogonal ECGs validated by nonelectrocardiographic criteria on the basis of clinical and anatomic diagnoses. Among 642 children catheterized for the evaluation of congenital heart disease, there were 140 patients with left ventricular hypertrophy, 299 with right ventricular hypertrophy, and 203 with biventricular hypertrophy. A group of 1069 obviously healthy school children was studied as a control. The overall accuracy of multigroup ECG diagnosis was 85% and 79% for the statistical and deterministic methods, respectively. The diagnostic performances of both methods expressed in terms of sensitivity and predictive value were the highest for normal children and those with right ventricular hypertrophy and lowest for children with biventricular hypertrophy. The statistical method was more sensitive in the diagnosis of left ventricular hypertrophy (74% vs 64%), right ventricular hypertrophy (86% vs 83%), and biventricular hypertrophy (62% vs 50%). Mutual agreement for a correct diagnosis by the two methods was 83% for normal children and 82% for those with right ventricular hypertrophy but only 61% for children with left ventricular hypertrophy and 39% for those with biventricular hypertrophy. In conclusion, better classification results are obtained with statistical multivariate techniques as compared with conventional deterministic analysis, but both methods of ECG interpretation are complementary and their combination in the same electrocardiographic computer program can improve diagnostic accuracy.
Adolescent↗
Clinical evaluation of automated processing of electrocardiograms by the Veterans Administration program (AVA 3.4).
Automated processing of electrocardiograms by the Veterans Administration program was evaluated for both agreement with physician interpretation and interpretative accuracy as assessed with nonelectrocardiographic criteria. One thousand unselected electrocardiograms were analyzed by two reviewer groups, one familiar and the other unfamiliar with the computer program. A significant number of measurement errors involving repolarization changes and left axis deviation occurred; however, interpretative disagreements related to statistical decision were largely language-related. Use of a printout with a more traditional format resulted in agreement with physician interpretation by both reviewer groups in more than 80 percent of cases. Overall sensitivity based on agreement with nonelectrocardiographic criteria was significantly greater with use of the computer program than with use of the conventional criteria utilized by the reviewers. This difference was particularly evident in the subgroup analysis of myocardial infarction and left ventricular hypertrophy. The degree of overdiagnosis of left ventricular hypertrophy and posteroinferior infarction was initially unacceptable, but this difficulty was corrected by adjustment of probabilities. Clinical acceptability of the Veterans Administration program appears to require greater physician education than that needed for other computer programs of electrocardiographic analysis; the flexibility of interpretation by statistical decision offers the potential for better diagnostic accuracy.
Cardiomegaly↗
Vectorcardiographic diagnosis of right ventricular hypertrophy in the presence of right bundle branch block in young subjects.
Two groups of young patients, one with right bundle branch block complicated by right ventricular hypertrophy due to congenital heart disease, the other with right bundle branch block and no right ventricular hypertrophy, could be separated on the basis of a few quantitative vectorcardiographic and electrocardiographic criteria. Vectorcardiographic criteria proved better than electrocardiographic criteria in detecting right ventricular hypertropy in individual patients with complete right bundle branch block. Criteria based on the configuration of the QRS loop were also specific but much less sensitive for the diagnosis of this association. In a similar population, that is, young patients with postoperative right bundle branch block, the existence of a residual right ventricular overload would be strongly suggested by the presence of any one of the following criteria: (1) a clockwise rotation of the QRS loop in the horizontal plane, (2) a ratio of the magnitude of the R wave to that of the S wave (R/S ratio) in lead X at less than 2.0, (3) a mean QRS vector in lead X more negative than--10 mv.msec, or (4) a maximal QRS vector located between 90 degrees and 270 degrees in the horizontal plane. In contrast, an R/S ratio in lead X that was equal or superior to 2.0 or an azimuth angle of the mean spatial QRS vector that was not between 90 degrees and 180 degrees would indicate that the right ventricular conduction defect is probably uncomplicated.
Adolescent↗
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'.
Diagnosis, Computer-Assisted↗
Spatial Frank vectorcardiogram in left posterior fascicular block. Criteria and correlation with clinical and electrocardiographic data.
Computer processing of spatial QRS parameters (Frank vectorcardiogram) was used to study left posterior fascicular block. The best set of vectorcardiographic criteria was sought in order to characterise the classic pattern of left posterior fascicular block. Using these criteria, 18 cases were selected from a group of 4600 patients and 340 healthy subjects; isolated left posterior fascicular block was seen in 10 cases, and was associated with right bundle-branch block in 8 cases. It is shown that some external factors can influence the aspect of the spatial QRS loop in left posterior fascicular block: cardiomegaly tends to produce a superior displacement of the main QRS forces: right bundle-branch block enhances the superior displacement of the initial forces and shifts the main QRS forces more anteriorly and to the right. The 'masquerading effect' of the left posterior fascicular block on a concomitant inferior myocardial infarct was also shown. The most important diagnostic feature was the opposite direction of the initial forces (left anterosuperior) and the maximal vector (right postero-inferior): the angle between these two vectors averaged 152 degrees. Other criteria, such as the direction of rotation or the axis of the frontal loop, the vertical direction of the spatial loop, the presence of a Q wave in leads II, III, and aVF of the electrocardiogram, are not mandatory for the diagnosis of left posterior fascicular block.
Adolescent↗
Reassessment of the diagnostic value of the vectorcardiogram in cystic fibrosis (correlation with clinical score, pulmonary function tests and echocardiogram).
In 21 children with cystic fibrosis, the vectorcardiogram (VCG) was correlated with various indices of the severity of the disease. The best correlation was found between (1) the azimuth angle of the spatial QRS loop area, representing the rightward and posterior shift of the main electrical forces, and pulmonary function tests (PFT): FEV1 % predicted (r = -0.671, P less than 0.005) and VC% predicted (r = -0.607, P less than 0.005), and (2) the right ventricular anterior wall index measured echocardiographically (r = 0.472, P less than 0.05). More VCG parameters correlated significantly with PFT than with the echocardiogram. This shows the major influence of pulmonary changes on the VCG of those patients. In several subgroups with different clinical scores, the VCG were analyzed and compared to normal limits of age- and sex-matched controls. In this small series, the VCG was a specific but not very sensitive method for predicting the degree of severity of the disease. Echocardiography and vectorcardiography can be considered as two complementary techniques in the evaluation of cystic fibrosis.
Adolescent↗
P-wave abnormalities in right and left ventricular overload: electrocardiographic and hemodynamic correlations.
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Aortic Valve Insufficiency↗
P wave abnormalities in the orthogonal electrocardiogram: Correlation with ventricular overload in pulmonic and aortic valvular heart disease.
The correlation between several P wave measurements form the orthogonal electrocardiogram (SVEC III lead system) extracted by computer analysis and simple hemodynamic parameters related to ventricular dysfunction was studied in two groups of patients. Group I consisted of 32 patients with pulmonic valvular stenosis and intact interventricular septum. There was a significant correlation between electrocardiographic criteria of right atrial overload and the two hemodynamic parameters studied: peak pulmonic systolic pressure gradient and right ventricular end diastolic pressure (r = 0.502, p smaller than 0.005 and r = 0.661, p smaller than 0.001 respectively). Group II consisted of 49 patients with aortic valve disease. In this group, a significant correlation between the electrocardiographic parameters of left atrial overload and the left ventricular end diastolic pressure could be demonstrated only be a multivariate regression analysis (r = 0.630, p smaller than 0.005). The P wave measurements that are well correlated with the ventricular end diastolic pressure can be considered as valuable criteria for atrial enlargement secondary to a decrease of ventricular compliance, such as seen in ventricular hypertrophy, failure or in ventricular constrictive or restrictive diseases. The pathophysiologic mechanisms of the influence of the ventricular overload (dysfunction) on the atrial function and the resulting P wave changes are discussed.
Adolescent↗
Quantative analysis of the vectorcardiogram in obesity. The effects of weight reduction.
Vectorcardiograms (VCG) recorded in 37 subjects with marked chronic EXOGENOUS OBESITY (AVERAGE WEIGHT: 285 LBS.) WERE COMPARED before and after a significant weight reduction (average weight loss: 86 lbs). They were also compared with the VCGs of 293 age and sex matched controls with normal body weight. The SVEC III corrected orthogonal lead system was used, and out of several hundred vectorcardiographic measurements obtained by computer processing, 59 measurements representing various scalar, planar and spatial voltage and angular measurements were selected for study and comparisons. No significant differences were found between the measurements of obese subjects and those of the controls. Of 59 VCG measurements, 13 showed significant differences after weight reduction (paired t test) although they remained within the range of normal controls. There was a trend toward decrease of P and QRS amplitudes after weight reduction. There were no significant changes in the angular measurements. Although they are statistically significant these changes in voltage are too small to be detected in clinical vectorcardiography. The possible decrease of a preexisting myocardial hypertrophy superimposed onto the changes in the anatomy of the thorax might explain the effects of weight reduction. In general the reproducibility of VCG measurements obtained by the SVEC III system was greater than that reported in day-to-day operation with the Frank system in normal subjects.
Adipose Tissue↗