PubMed Health⌕ Search

Biomedical subjects

J Pardaens

Publications and source records attributed to J Pardaens.

At least 19 recordsLinked to original sources
PubMed1987

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)

Cardiomegaly↗
PubMed1987

Acute myocardial infarction in the very elderly. A comparison with younger age groups.

In a consecutive series of 2312 patients with acute myocardial infarction (AMI) admitted from 1973 till 1979, 188 were 80 years or older (group III). They were compared with 1167 patients younger than 65 years (group I) and 957 aged 65 to 79 years (group II). The sex ratio (males/females) fell from 5.46 in group I to 0.9 in group III. Group III patients had more frequently a history of previous heart failure and more often atypical or no chest pain before admission. Less group III patients were admitted within 4 hours after onset of symptoms, but the incidence of heart failure, pulmonary edema and cardiogenic shock on admission and during CCU stay was definitely higher than in younger patients. Atrial arrhythmias, 2nd and 3rd degree atrioventricular block, complete bundle branch block and intraventricular conduction disturbances occurred more frequently in group III. The electrocardiographic extent and location of the infarction and peak enzyme levels were similar in the three groups. Mortality in group III was 43.6% at the 28th day and 76.6% at one year after AMI. At different intervals after the onset of AMI mortality increased progressively from group I to III. Age by itself, probably on the basis of definite structural changes of the heart and of other organs occurring during aging, leads to higher early and late mortality in very elderly people.

Aged↗
PubMed1985

Critical evaluation of quadratic logistic discriminant analysis methods: a case study.

Electrocardiographic measurements from two groups, patients with left ventricular hypertrophy and clinically normal cases, were analyzed to illustrate the performance of the linear logistic discrimination method in the case of very unequal covariance matrices. Two quadratic extensions of the linear model were critically investigated. The use of graphical methods to check the model has been stressed and illustrated.

Biometry↗
PubMed1985

Multivariate survival analysis for the assessment of prognostic factors and risk categories after recovery from acute myocardial infarction: the Belgian situation.

Twenty-one and a half per cent of the patients with acute myocardial infarction, admitted consecutively to the coronary care unit of the University Hospitals of Leuven in the period 1973-1979, died within 28 days. The 1,669 who recovered were followed between three and nine years. The mortality rate was 13.1% during the first year and fell to below 5% in the succeeding yearly intervals. Univariate and life table analysis were performed on noninvasive, clinical data collected during the coronary care unit stay for the total population and various subgroups. The Cox proportional hazards model was applied to the data in order to determine the prognostic factors for long-term survival. Of the 34 initially selected variables, the most dominant factors were age, Killip class III and IV, peripheral vascular disease, abnormal chest x-ray findings, previous infarction, and the use of digitalis or diuretics. The model, which was validated extensively, allowed the establishment of risk categories. Mortality five years after the acute event was 8.2 times more frequent in the highest risk quintile than in the lowest one. From this study one may conclude that multivariate techniques based on noninvasive variables collected during the coronary care unit stay are valuable for the determination of the long-term prognosis of patients with myocardial infarction.

Actuarial Analysis↗
PubMed1984

Early risk stratification using clinical findings in patients with acute myocardial infarction.

The value of non-invasive, clinical variables in predicting short-term outcome after acute myocardial infarction has been prospectively studied using multivariate analysis in a learning population of 1724 patients and a validation sample of 588 cases. Early risk stratification of CCU mortality could be made with 89.4% accuracy by using 7 simple clinical variables (Killip class, systolic blood pressure, heart rate, age, intraventricular conduction disturbance, localization of infarction and obesity index) recorded on admission. A discriminant function formula could also be constructed resulting in a maximal classification of 89.3% and predictive values of 91.8% and 77.9%, respectively, for 28-day survival and early death prediction in the learning population. Accuracy figures dropped only slightly (1 to 5%) in the independent test set. Predictions could be made with a high degree of accuracy, especially in the upper and lower ranges of the discriminant risk score. This investigation demonstrates that a fairly good estimation of prognosis can be made by means of discriminant analysis of clinical findings gathered routinely in most CCU's.

Aged↗
PubMed1979

Influence of lung inflation on the elastic properties of intra-and extrapulmonary airways in man.

In excised human lungs, the proximal intrapulmonary airways and distal extrapulmonary airways were isolated in situ, by means of the technique of Takishima el al. (1975), and submitted to varying transmural pressures at constant lung inflation. Both intra-and extrapulmonary airways became stiffer, i.e. showed a decreased collapsibility, at higher levels of lung inflation. The altered mechanical behavior of the intrapulmonary airways with lung inflation, observed also by Hughes et al. (1974) and Takishima et al. (1975), has been attributed to a tethering action of the lung parenchyma on these airways. The same mechanism may be operating on the distal extrapulmonary airways, to the extent that the pleura and hilar structures transmit the stresses of the lung parenchyma. Alternatively, the elongation of the bronchi occurring during lung inflation might be responsible for their increasing resistance to collapse with lung volume. A separate study showed, indeed, that stretching of the bronchi reduces their collapsibility.

Bronchi↗
PubMed1975

Simulation of frequency dependence of compliance and resistance in healthy man.

The frequency dependence of effective compliance, Ceff, and resistance, Reff, are reproduced by means of a two- or four-compartment linear mathematical model with pleural pressure as a sinusoidal input. The model simulates the mechanical properties of lung parenchyma, alveolar gas, bronchial wall, and cheeks, as well as the distribution of gaseous resistances and inertances within the airways. Values, representative for a young healthy adult, are assigned to these various parametersmit appears from this study: 1) that the gas inertance produces a very marked increase of Ceff, noticeable already below 1 cycle/smto obtain a frequency independence of Ceff between 0 and 2 cycles/s, it is necessary to introduce a marked inhomogeneity in the model. 2) Such an inhomogeneity is realized by simulating a pleural pressure difference of 6 cmH2O between the compartments of the bialveolar model. It can be shown that this corresponds to a total pleural pressure difference of about 9 cmH2O in a model consisting of an infinite number of compartments. 3) The influence of the compressibility of alveolar gas and of mechanical properties of the bronchial wall and of the cheeks on Ceff and Reff is small or negligible.

Airway Resistance↗
PubMed1975

Simulation of regional lung emptying during slow and forced expirations.

Regional lung emptying was simulated by means of a bialveolar lung model. The influence of bronchial asymmetry and the vertical pleural pressure gradient was evaluated. The model suggests that 1) in vivo the influence of the pleural pressure gradient prevails over that of the bronchial asymmetry; 2) in the presence of this gradient, the shape of phases III and IV of the single-breath washout curves obtained following inspiration of a tracer gas bolus at residual volume is determined by the recoil pressure-volume curve of the lung, by the vertical displacements of the alveoli, and,, at higher flow rates, by the elastic characteristics of the airways; 3) if the pleural pressure gradient is independent of lung volume and of flow rate, the factors mentioned in 2 suffice to produce single-breath washout curves (phases III and IV) and regional vs. overall lung volume relationships corresponding to those observed in vivo; 4) the configuration of the maximal expiratory flow-volume curve is relatively insensitive to pulmonary and bronchial asymmetry, at least in healthy individuals.

Bronchi↗
PubMedDate not supplied

Action of isoprenaline on the mechanical properties of lungs and airways in healthy people and patients with obstructive lung diseases.

Lung volumes, maximal expiratory flows, pulmonary resistance and static recoil pressure-volume curves were measured before and after inhalation of isoprenaline in four groups of subjects: heqlthy patients with mild and severe chronic bronchitis and asthmatics. The observed changes were qualitatively similar in the four groups. Whereas total lung capacity and dynamic compliance were not influenced, there was an increase in vital capacity (not in healthy subjects and mild bronchitics), in FEV1, in maximal expiratory flows and a decrease in pulmonary resistance. The static recoil pressure-volume relationship was shifted to the left over its ascending part. The effect of isoprenaline tended to be larger in patients. Among the latter, the increase of vital capacity was especially pronounced in the severe bronchitics, whereas the maximal flows increased most in asthmatics. We suggest that the influence of isoprenaline on maximal flows results from a bronchodilation, associated with an increased collapsibility of the central intrathoracic airways, whereas the influence of VC might reflect a delayed onset of small airway closure.

Adult↗