Search PubMed⌕ Search

Biomedical subjects

R A Dunn

Publications and source records attributed to R A Dunn.

14 recordsLinked to original sources
PubMed1979

Performance of conventional orthogonal and multiple-dipole electrocardiograms in estimating left ventricular muscle mass.

For estimating left ventricular mass (LVM), ECG criteria for left ventricular hypertrophy (LVH) were selected from conventional 12-lead ECGs, orthogonal three-lead ECGs, and multiple-dipole ECGs (MDECG). The three cardiograms were recorded in 139 patients for whom the degree of LVH was independently determined from biplane ventriculograms. Tested ECG criteria included Sokolow-Lyon measurements for the 12-lead ECG; for the orthogonal ECG, maximal QRS magnitude in the horizontal plane, R duration in the z-lead and Jxyz (spatial magnitude of point J); and for the 126 leads of the MDECG, the dipole activity (DA) of the septum and the free left ventricular wall. Correlation coefficients between LVM and the 12-lead ECG, three-lead ECG and MDECG were 0.61, 0.78 and 0.89, respectively, with corresponding errors of estimated LVM of 103, 82 and 60 g. More complex recording and analytic methods clearly led to increased accuracy in LVM estimates. However, the large error of estimate may limit practical applicability of such correlations. For classification of subjects into normal and above-normal categories, a likelihood ratio was also used and led to a maximum performance index of 86% with MDECG measurements.

Electrocardiography↗
PubMed1977

Computer analysis of changes in frank vectorcardiograms of 666 normal infants in the first 72 hours of life.

Frank vectorcardiograms (VCGs) were collected on magnetic tape for 666 normal newborn infants at 1, 6, 12, 24, 36, 48, 60, and 72 hours after birth and analyzed by computers. The final total included 1,337 VCGs for white babies and 413 for blacks. No previous report has been made for the normal neonate with such a large sample, and no previous substantiation exists of possible age or sex differences at this early age. This study establishes a statistically significant change in vectorcardiographic patterns over the first three days, specifically in the measurements P duration, QRS duration, maximal spatial QRS amplitude, S in lead x, and T in lead z, as well as for several time-normalized QRS vectors. (P less than or equal to .005.) Racial differences were significant for T waves in lead z. This study supports the use of vectorcardiographic standards sensitive to the age of the newborn as well as to race.

Age Factors↗
PubMed1977

Serial electrocardiograms in hypertensive cardiovascular disease.

A graphic method for depicting serial changes in electrocardiograms is described and demonstrated for patients being treated in an antihypertension clinic. For these patients, the diagnostic categories, normal, left ventricular hypertrophy, and biventricular hypertrophy, are of primary interest. For each electrocardiogram, 14 measurements are used to compute posterior probabilities for each of the three categories. A triangular grid is used to plot each set of probabilities for an electrocardiogram as one point, which by its position in the triangle can be related to the three categories simultaneously. Points representing successive electrocardiograms can be plotted in the same triangle, giving a pattern of change with time. This pattern of change has been corroborated with associated clinical information on a number of patients. This display, which can be produced quickly and efficiently on a computer graphics terminal, should be considered as a possible tool in evaluating the status of individual hypertensive patients in terms of increase or decrease of ventricular hypertrophy and the efficacy of therapeutic measures.

Aged↗
PubMed1975

Clinical application of a second generation electrocardiographic computer program.

An electrocardiographic computer program based on multivariate analysis of orthogonal leads (Frank) was applied to records transmitted daily by telephone from the Veterans Administration Hospital, West Roxbury, Mass., to the Veterans Administration Hospital, Washington, D. C. A Bayesian classification procedure was used to compute probabilities for all diagnostic categories that might be encountered in a given record. Computer results were compared with interpretations of conventional 12 lead tracings. Of 1,663 records transmitted, 1,192 were selected for the study because the clinical diagnosis in these cases could be firmly established on the basis of independent, nonelectrocardiographic information. Twenty-one percent of the records were obtained from patients without evidence of cardiac disease and 79 percent from patients with various cardiovascular illnesses. Diagnostic electrocardiographic classifications were considered correct when in agreement with documented clinical diagnoses. Of the total sample of 1,192 recordings, 86 percent were classified correctly by computer as compared with 68 percent by conventional 12 lead electrocardiographic analysis. Improvement in diagnostic recognition by computer was most striking in patients with hypertensive cardiovascular disease or chronic obstructive lung disease. The multivariate classification scheme functioned most efficiently when a problem-oriented approach to diagnosis was simulated. This was accomplished by a simple method of adjusting prior probabilities according to the diagnostic problem under consideration.

Analysis of Variance↗
PubMed1975

Receptor synapses without synaptic ribbons in the cochlea of the cat.

This report describes recepto-neural junctions thought to be chemical synapses without synaptic ribbons or vesicle aggregates. Such synapses occur in the cat between the outer hair cells of the cochlea and auditory nerve fibers. These synapses are formed by flat or indented junctions having symmetric membrane complexes associated with smooth endoplasmic reticulum and coated vesicles in the outer hair cell cytoplasm. Inner hair cells have receptoneural junctions with asymmetric membrane complexes; synaptic ribbons and vesicles gather at one type of junction, while the other type associates with endoplasmic reticulum. Gap junctions are not seen at cochlear synapses but do link supporting cells. The results suggest that inner and outer hair cell synapses have different properties and raise questions about the role of synaptic vesicles and endoplasmic reticulum in the storage and release of transmitters.

Animals↗
PubMed1975

The program of the cooperative study of the Veterans Administration.

A computer program for the automatic analysis of the electrocardiogram is described with details about wave recognition, measurements, and the calculation of the posterior probabilities of each diagnosis. The advantages and disadvantages of this multivariate statistical procedure are discussed. Classification statements result from separate analysis of the QRS-T complex, P wave, and ST segment. Criteria for inclusion of the patients forming the data base are given, with tables of measurements, means and standard deviation, as well as investigation of agreement between calculated and observed probabilities. Estimated error rates are given in the form of misclassification matrices, computed from large numbers of tracings collected by a Veteran Administration Cooperative Study, where the correct diagnoses are taken from clinical, laboratory, and autopsy information.

Cardiomegaly↗