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Biomedical subjects

I Graham

Publications and source records attributed to I Graham.

At least 73 records · Page 4Linked to original sources
PubMed1989

Percussion of the chest re-visited: a comparison of the diagnostic value of ausculatory and conventional chest percussion.

Percussion of the chest is thought to be insensitive in detecting small or deeply situated chest lesions. A newer technique, ausculatory percussion, has been reported as having a far higher sensitivity. In a controlled blind study the diagnostic value of conventional chest percussion compared with ausculatory percussion was defined using the chest x-ray as a gold standard. The prevalence of disease in 100 lung fields was 26%. The majority of lesions were not detected by either technique resulting in very low sensitivities of 15.4% for conventional percussion and 19.2% for ausculatory percussion. A positive result with ausculatory percussion was twice as likely to be false as true (positive predictive value 31.2%). The technique did not add to the diagnostic value of conventional percussion. Both techniques have major limitations. Patients with suspected lung disease still require chest x-ray examination if percussion is normal.

Auscultation↗
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↗
PubMed1984

Mortality from coronary heart disease-trends for the Republic of Ireland.

A study of certified mortality between 1968 and 1981 indicates that mortality from all causes commenced to decline from the mid 1970s in the Republic of Ireland. This trend was apparent for both sexes and for all ages except for men aged 55-64 years. A similar trend of lesser magnitude is suggested for coronary heart disease mortality in males, but not in females. The decrease in the percentage of male cigarette smokers in the population which is also reflected in a marked decline of smoking among male coronary patients, may be related to the trends in mortality.

Adult↗
PubMed1984

Factors affecting dietary compliance in coronary patients included in a secondary prevention programme.

Nutrient intake was altered favourably in the diets of 38 cardiac patients who were followed up for 1 year as part of a rehabilitation programme. Total energy intake was reduced from 3540 kcal (14.9 MJ) to 2484 kcal (10.4 MJ). Fat intake was reduced from 41 to 37 per cent of energy intake with an accompanying increase in P : S ratio from 0.18 to 0.60. Cholesterol intake was reduced from 564 to 332 mg. Carbohydrate was increased from 38 to 41 per cent of energy intake with an increase in fibre intake from 18 to 24 g. The energy contributed by alcohol was reduced from 6 to 5 per cent. Patients varied in their compliance but all patients made some changes in their dietary intake. Changes in body weight, serum cholesterol levels, cigarette-smoking status and levels of physical activity tended to correspond with the recorded changes in nutrient intake. A low level of education, low socio-economic group, lack of understanding of the illness by the patient and inadequate communication were associated with reduced compliance. Initial motivation and anxiety levels in hospital had less effect on compliance.

Adult↗