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Biomedical subjects

I Graham

Publications and source records attributed to I Graham.

At least 37 records · Page 2Linked to original sources
PubMed1988

Effect of combining electrocardiographic interpretation results on diagnostic accuracy.

In order to test the diagnostic performance of various ECG computer programs a reference library of ECGs is being established and evaluation methods are being developed in an international co-operative project. A pilot study was undertaken in which 250 validated electrocardiograms (ECG) and vectorcardiograms (VCG) comprising seven diagnostic groups i.e., normal, left, right and bi-ventricular hypertrophy, anterior, inferior and combined infarction have been analysed independently by 11 different computer programs as well as by six cardiologists. A coding scheme was applied to assign individual diagnostic statements to a common set and to obtain combined program and cardiologist interpretation results. Preliminary results indicate that the accuracy of classification by different programs varies widely. Total accuracy varied between 57.2% and 75.8% (median 69.4%). The cardiologists had a higher accuracy (median 74.3%) than the majority of programs, at least when using the standard ECG. As it is considered premature to stress individual program results, in view of the current sample size, the enhancement in diagnostic accuracy obtained by combining interpretation results is highlighted. Indeed combined cardiologist and program results demonstrated the highest accuracy i.e., respectively 78.7% and 76.1%, higher than the result of any individual reader or program. The combined result of the five most accurate programs was 78.4%, that of the six least accurate was 71.5%, which is again higher than the respective individual components. These findings demonstrate that the combination of expert knowledge of computer programs can, similar to panel review and group analysis in clinical practice, enhance diagnostic accuracy.

Diagnosis, Computer-Assisted↗
PubMed1987

A reference data base for multilead electrocardiographic computer measurement programs.

In an effort to standardize and evaluate the performance of electrocardiographic computer measurement programs, a 15 lead reference library has been developed based on simultaneously recorded standard 12 lead and orthogonal XYZ lead data. A set of 250 electrocardiograms (ECGs) with selected abnormalities was analyzed by a group of five referee cardiologists and 11 different 12 lead and 6 XYZ computer programs. Attention was focused on the exact determination of the onsets and offsets of P, QRS and T waves. The referees performed their task on highly amplified, selected complexes from the library in a two round process. Median results of the referees coincided best with the median derived from all programs. An analysis of stability proved that the combined program median was a robust reference. However, some individual program results were widely divergent. Paired t tests demonstrated earlier onset for P and QRS (p less than 0.001), as well as later offset for P and T waves in the median 12 lead than in the XYZ results. Significant differences also existed among results obtained by programs analyzing all standard ECG leads at one time, the so-called multilead programs, and those obtained by the conventional standard three lead analysis programs. As a consequence, the derived P, PR, QRS and QT interval measurements varied quite widely among the various programs. Significant differences were also observed among measurements of Q, R and S duration. Some programs showed Q waves that were on the average 6 ms (p less than 0.001) longer than those of others. This may significantly influence diagnostic performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography↗
PubMed1987

Testing the performance of ECG computer programs: the CSE diagnostic pilot study.

In an international project investigators from 21 institutes are trying to establish a common reference library and evaluation methods for testing the diagnostic performance of various ECG computer programs using ECG independent clinical information. Preliminary results indicate that the classification accuracy of different programs varies widely.

Electrocardiography↗
PubMed1986

Myocardial hypertrophy, fibrosis and infarction following exposure of the heart to radiation for Hodgkin's disease.

A 35 year old man was treated for stage IIA Hodgkin's disease by radiation to the upper thorax, axillae and neck. Three years later he presented with intractable and ultimately fatal congestive heart failure. Autopsy revealed massive biventricular hypertrophy with widespread subendocardial fibrosis and myocardial infarction, but with little coronary artery disease. Such a complex of features has not previously been described after radiation therapy and cannot be adequately explained by other known causes of heart muscle disease. Ventricular hypertrophy with extensive subendocardial fibrosis may be part of the spectrum of radiation heart disease.

Adult↗
PubMed1985

Kinetics and thermodynamics of calcium-induced lateral phase separations in phosphatidic acid containing bilayers.

The effects of calcium on the mixing of synthetic diacylphosphatidylcholines (PC's) and diacylphosphatidylethanolamines (PE's) with the corresponding phosphatidic acids (PA's) have been examined by high-sensitivity differential scanning calorimetry and by measurements of the fluorescence of labeled PA or PC species in PA-PC bilayers. Calorimetrically derived phase diagrams for dimyristoyl- and dielaidoyl-substituted PA-PC and PA-PE mixtures indicate that these species are readily miscible in the absence of calcium but phase-separate very extensively in the presence of high levels of calcium (30 mM). The limiting solubilities of PA (Ca2+) in liquid-crystalline PC or PE bilayers are less than or equal to 10 and approximately 5 mol %, respectively, while approximately 20 mol % of PC or PE can be introduced into the "cochleate" phase of PA (Ca2+) before a distinct PC-rich (or PE-rich) phase appears. The kinetics of calcium-induced lateral phase separations were examined for dioleoyl- and dielaidoyl-substituted PA-PC unilamellar vesicles labeled with fluorescent (C12-NBD-acyl) PA or PC, whose fluorescence becomes partially quenched upon phase separation. Our results indicate that, for the PA-PC system, lateral phase separation is very rapid (approximately less than 1 s) after calcium addition and develops partially (possibly in only one face of the bilayer) when calcium is present only on one side of the bilayer. Moreover, phase separations can develop at a rate faster than that of vesicle diffusion when calcium is added to dilute suspensions of vesicles, suggesting that interbilayer contacts are not essential to promote phase separations.

Calcium↗
PubMed1985

Calcium-induced lateral phase separations in phosphatidylcholine-phosphatidic acid mixtures. A Raman spectroscopic study.

The effects of calcium ions on mixed membranes of dimyristoylphosphatidic acid (DMPA) and dimyristoylphosphatidylcholine (DMPC) with either the PA or the PC component deuterated have been studied by Raman spectroscopy. The spectra of the pure components show that the acyl chains of hydrated DMPA bilayers are less tightly packed and have more trans bonds than those of DMPC. This behavior appears to be due to the particular arrangement of the polar head groups of DMPA for which the glycerol chain is oriented parallel to the bilayer surface. In agreement with the calorimetrically determined phase diagram [Graham, I., Gagné, J., & Silvius, J. R. (1985) Biochemistry (preceding paper in this issue)], the Raman results show that, in the absence of calcium, DMPA and DMPC are completely miscible at an equimolar ratio but undergo extensive phase separation in the presence of excess calcium. DMPC in phase-separated DMPC-DMPA (Ca2+) mixtures has a conformation that is very similar to that of pure DMPC bilayers, but it is packed more tightly since, depending on the temperature, it is at least partly incorporated into either a solid solution in DMPA or a DMPA-Ca2+-rich "cochleate" phase. This latter shows the same characteristics as the cochleate phase of pure DMPA-Ca2+ which is highly ordered and does not give rise to a thermotropic transition between 5 and 100 degrees C. However, the cochleate phase in DMPA (Ca2+)-DMPC mixtures contains some 20 mol % of DMPC trapped in small domains. These clusters do not melt cooperatively but become as fluid as pure DMPC at 50 degrees C.

Calcium↗
PubMed1985

Diet and 20-year mortality from coronary heart disease. The Ireland-Boston Diet-Heart Study.

In a prospective epidemiologic study of 1001 middle-aged men, we examined the relation between dietary information collected approximately 20 years ago and subsequent mortality from coronary heart disease. The men were initially enrolled in three cohorts: one of men born and living in Ireland, another of those born in Ireland who had emigrated to Boston, and the third of those born in the Boston area of Irish immigrants. There were no differences in mortality from coronary heart disease among the three cohorts. In within-population analyses, those who died of coronary heart disease had higher Keys (P = 0.06) and modified Hegsted (P = 0.02) dietary scores than did those who did not (a high score indicates a high intake of saturated fatty acids and cholesterol and a relatively low intake of polyunsaturated fatty acids). These associations were significant (P = 0.03 for the Keys and P = 0.04 for the modified Hegsted scores) after adjustment for other risk factors for coronary heart disease. Fiber intake (P = 0.04) and a vegetable-foods score, which rose with increased intake of fiber, vegetable protein, and starch (P = 0.02), were lower among those who died from coronary heart disease, though not significantly so after adjustment for other risk factors. A higher Keys score carried an increased risk of coronary heart disease (relative risk, 1.60), and a higher fiber intake carried a decreased risk (relative risk, 0.57). Overall, these results tend to support the hypothesis that diet is related, albeit weakly, to the development of coronary heart disease.

Adult↗
PubMed1979

The implementation of a large-scale self-instructional course in medical information resources.

The implementation of library orientation and bibliographic instruction in health sciences centers presents some interesting as well as perplexing problems. The Rowland Medical Library at The University of Mississippi Medical Center had to confront and reexamine these problems when faced with the requirement to teach 298 freshman and sophomore medical students in one ten-week quarter. This paper outlines the development and implementation of a large-scale self-instructional approach to library instruction. The package consisted of an audiotape, a videotape, a written program, self-teaching quizzes, a performance test, and a student evaluation. Performance test results and student evaluation data are presented which indicate that this format can successfully be employed to meet course objectives and to be accepted by students.

Audiovisual Aids↗