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Biomedical subjects

M J Gardner

Publications and source records attributed to M J Gardner.

At least 163 records · Page 9Linked to original sources
PubMed1986

Non-Q-wave acute myocardial infarction: body surface potential map and ventriculographic patterns.

Day 5 body surface map and radionuclide angiographic patterns were compared among 56 patients with first non-Q-wave or Q-wave acute myocardial infarction (AMI). Three radionuclide angiographic patterns were recognized in patients with non-Q infarction: no wall motion abnormalities (n = 8), single-segment wall motion abnormalities (n = 10) and multiple-segment wall motion abnormalities (n = 9). In contrast, only 2 radionuclide angiographic patterns were identified in patients with Q-wave infarction: multiple-segment wall motion abnormalities (n = 25) and single-segment wall motion abnormalities (n = 4). The Q-wave distributions of 14 of 18 patients with non-Q infarction with 0 or 1 wall motion abnormalities were normal; 2 patients had "missed" anterior; 1 patient had inferior; and 1 had posterior AMI patterns. Of 9 patients with non-Q infarction who had multiple-segment wall motion abnormalities, 8 had infarct Q waves on the posterior torso. Q-wave patterns in patients with anterior (n = 17) and inferior (n = 12) Q-wave infarctions were typical and homogeneous for each group. Quantitative analysis of minimum Q-zone integral, sigma Q-wave integrals, ST-integral maximum, wall motion abnormality score and ejection fraction revealed no differences between patients with non-Q-wave and those with inferior Q-wave infarction. In contrast, patients with anterior AMI had significantly more abnormal values of all variables than either of the other groups. Overall, the data support the concept of non-Q-wave AMI as a distinct, if heterogeneous, pathophysiologic entity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Micromethod for the analysis of evans blue in plasma using ion-pair high-performance liquid chromatography.

A micromethod for the determination of Evans Blue in plasma has been developed. Effective release of the dye from the dye-albumin complex was accomplished using a solution of urea and 2-mercaptoethanol. Ion-pairing techniques were used to extract the dye as well as the internal standard (Naphthol Blue Black B) from plasma. Separation involved ion-pair high-performance liquid chromatography. Eluent was monitored at 605 nm. The technique results in a linear response over the concentration range of approximately 1.0-30.0 micrograms/ml. Assay performance was verified by estimating plasma volume in the rat.

Animals↗
PubMed1986

Use of check lists in assessing the statistical content of medical studies.

Two check lists are used routinely in the statistical assessment of manuscripts submitted to the "BMJ." One is for papers of a general nature and the other specifically for reports on clinical trials. Each check list includes questions on the design, conduct, analysis, and presentation of studies, and answers to these contribute to the overall statistical evaluation. Only a small proportion of submitted papers are assessed statistically, and these are selected at the refereeing or editorial stage. Examination of the use of the check lists showed that most papers contained statistical failings, many of which could easily be remedied. It is recommended that the check lists should be used by statistical referees, editorial staff, and authors and also during the design stage of studies.

Clinical Trials as Topic↗
PubMed1986

Confidence intervals rather than P values: estimation rather than hypothesis testing.

Overemphasis on hypothesis testing--and the use of P values to dichotomise significant or non-significant results--has detracted from more useful approaches to interpreting study results, such as estimation and confidence intervals. In medical studies investigators are usually interested in determining the size of difference of a measured outcome between groups, rather than a simple indication of whether or not it is statistically significant. Confidence intervals present a range of values, on the basis of the sample data, in which the population value for such a difference may lie. Some methods of calculating confidence intervals for means and differences between means are given, with similar information for proportions. The paper also gives suggestions for graphical display. Confidence intervals, if appropriate to the type of study, should be used for major findings in both the main text of a paper and its abstract.

Adult↗
PubMed1986

Electrocardiographic and ventriculographic recovery patterns in Q wave myocardial infarction.

To further define the capacity for recovery after acute phase electrical and mechanical injury in patients with Q wave myocardial infarction who were treated with standard measures, 120 lead body surface potential maps and radionuclide angiograms were recorded at day 5 before discharge and month 6 after infarction in 23 patients with a first infarction (12 anterior and 11 inferior by standard 12 lead electrocardiographic criteria). In addition to assessment of spatial changes in electrocardiographic and wall motion patterns, five quantitative variables were evaluated: minimal Q zone integral, sigma Q wave integral, maximal ST integral, left ventricular ejection fraction and left ventricular wall motion abnormality score. From day 5 to month 6 after infarction, the only change in the inferior infarction group was a gain in sigma Q wave (-91 +/- 40 mu V X s X 10(2) to -68 +/- 24 mu V X s X 10(2); p less than 0.05). In contrast, all variables improved over the same time period in the anterior infarction group: Q zone minimum, -34 +/- 20 to -24 +/- 13 mu V X s (p less than 0.05); sigma Q wave, -160 +/- 122 X 10(2) to -120 +/- 90 mu V X s X 10(2) (p less than 0.05); ST maximum, 44 +/- 19 to 18 +/- 9 mu V X s (p less than 0.01); ejection fraction, 54 +/- 7 to 63 +/- 17% (p less than 0.05); and wall motion score, 6 +/- 3 to 3 +/- 3 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1986

Follow up study of workers manufacturing chrysotile asbestos cement products.

A cohort study has been carried out of 2167 subjects employed between 1941 and 1983 at an asbestos cement factory in England. The production process incorporated the use of chrysotile asbestos fibre only, except for a small amount of amosite during four months in 1976. Measured airborne fibre concentrations available since 1970 from personal samplers showed mean levels below 1 fibre/ml, although higher levels had probably occurred previously in certain areas of the factory. No excess of lung cancer was observed in the mortality follow up by comparison with either national or local death rates, and analyses of subgroups of the workforce by job, exposure level, duration of employment, duration since entry, or calendar years of employment gave no real suggestion of an asbestos related excess for this cause of death. There was one death from pleural mesothelioma and one with asbestosis mentioned as an associated cause on the death certificate, but neither is thought to be linked to asbestos exposure at this factory. Other suggested asbestos related cancers, such as laryngeal and gastrointestinal, did not show raised risks. Although the durations of exposure were short in this study, the findings are consistent with two other studies of workers exposed to low concentrations of chrysotile fibre in the manufacture of asbestos cement products which reported no excess mortality.

Asbestos↗
PubMed1986

Vulnerability to ventricular arrhythmia: assessment by mapping of body surface potential.

It is now well established that the vulnerability of the ventricular myocardium to repetitive dysrhythm increases in the presence of greater than normal disparity local recovery times. Local recovery is reflected in the electrocardiographic waveform as an area of the ventricular deflection (QRST time integral), and thus disparate ventricular recovery may be manifested in the body surface distribution of this quality. To assess this possibility, we obtained simultaneous 120-lead electrocardiograms from both the anterior and posterior torso in 140 subjects (ages 8 to 75) grouped as follows: group A, 97 normal subjects; group B, 16 patients resuscitated from ventricular fibrillation or sustained ventricular tachycardia; and group C, 27 patients 6 to 12 months after myocardial infarction but without clinically significant arrhythmia. In each subject, the QRST integral was evaluated for each lead and isointegral contour maps were plotted. A score was assigned to each map, based on the number of extrema; each maximum or minimum scored one point, with the exception of simultaneously occurring anterior and posterior minima on the right shoulder (frequently occurring in normal subjects), which scored together only one point. All but one group A subject had dipolar QRST integral maps (mean +/- SD score 2.11 +/- 0.2). Conversely, 10 of 16 (62.5%) group B patients had scores of 3 or more (mean 3.16 +/- 1.08; p less than .01 vs group A). Group C patients had intermediate values, with eight of 27 (29.6%) scoring 3 or more (mean 2.46 +/- 83); this was less than in group B (p less than .01), but more (p less than .05) than in group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Stimulatory and cytotoxic effects of an antiserum to adipocyte plasma membranes on adipose tissue metabolism in vitro and in vivo.

Antibodies to rat adipocyte plasma membranes raised in sheep had a dual effect in vitro; at low concentrations they mimicked the actions of insulin whilst higher concentrations inhibited glucose incorporation into lipid. The insulin-like effects of the antibody appeared to be due to direct activation of the glucose transport system since the antibodies did not bind to the insulin receptor, as judged by their inability to immunoprecipitate the receptor or to inhibit insulin binding, and antibodies were able to stimulate glucose transport in cells which had had their insulin receptors removed by trypsinization. The inhibitory effects of the antiserum were due to cytotoxicity since, in the presence of antiserum, adipocytes began to release large quantities of the intracellular enzyme, lactate dehydrogenase, and were ultimately lysed. This cytotoxic effect of the antiserum was complement-dependent since heat-inactivated antiserum or a crude immunoglobulin fraction of the serum possessed only stimulatory effects on lipid metabolism. When injected into rats for 4 days the antiserum produced gross abnormality of adipose tissue depots. Dissolution of adipocytes and massive infiltration by lymphocytes and polymorphs were evident. Preliminary observations suggest that such treatment results in long-term reduction of the number of adipocytes in internal fat depots.

Adipose Tissue↗
PubMed1986

Mortality study of workers in the man-made mineral fiber production industry in the United Kingdom.

The workforces of two factories in the United Kingdom have been followed up to the end of 1984 as part of the collaborative European study of the health of workers in the man-made mineral fiber industry. In the cohort from an English glass-wool plant there was no suggestion of any excess mortality compared to national or local rates, except for lung cancer among men in comparison to the national level. However, the data indicate that the workers were largely local persons by place of birth, occupation, and death, and they therefore suggest that the national comparison was inappropriate. Lung cancer mortality showed little relationship to length of employment, duration of time since first exposure, occupational classification, or level of exposure. In the cohort from a continuous-filament plant in Northern Ireland no excess mortality from cancer was found. There were, however, raised death rates from violent causes and cardiovascular disease, but these rates were not exceptional for the area of the country in which the factory was located. No deaths from mesothelioma were reported in either cohort.

Construction Materials↗
PubMed1985

Mesothelioma of the peritoneum during 1967-82 in England and Wales.

The time-trend and geographical distribution of mesothelioma of the peritoneum during the years 1967-82 in England and Wales have been studied from the Mesothelioma Register held by the Medical Division of the Health and Safety Executive. Over the 16-year period the annual number of cases registered rose from about 15-20 to about 30-50. Although the number occurring in men was double that in women, the trend was similar for both sexes. There is likely to be some further increase before any improvement due to the recent diminished usage of asbestos is seen. Local Authority areas with raised rates have been identified, and the geographical pattern is similar to that of the distribution of the asbestos-using industry in the past. In both sexes there are high registration rates on the east side of London but, in contrast to mesothelioma of the pleura, a concentration of cases among men in the major ports where shipbuilding and ship repairing were carried out is not so apparent.

Adult↗
PubMed1985

Effect of myocardial ischemia and type I antiarrhythmic drug therapy on exercise QT intervals.

Direct measurement of the QT interval during exercise is the preferred method to assess duration of this interval with changes in heart rate. The influence of exercise induced ischemia or type I antiarrhythmic drugs on the exercise QT interval has not been well studied. Exercise electrocardiograms and thallium scintigraphy were performed in three groups-normals, patients with coronary artery disease, and patients taking type I antiarrhythmic drugs. The change in QT interval with heart rate increases during exercise was compared among the three groups. The QT interval shortened progressively in the normal group. Demonstrable myocardial ischemia (positive thallium scan) had no effect on the QT interval. Type I antiarrhythmic drugs prolong the QT interval at rest compared to normals, but the interval shortened to the same degree as in normals during exercise. Thus, normal values can be used to compare QT intervals in patients with coronary artery disease. These values do not apply to patients receiving type I antiarrhythmic drugs.

Anti-Arrhythmia Agents↗
PubMed1985

Sudden cardiac death: the search for a non-invasive means to detect the electrical substrate for the development of life-threatening cardiac arrhythmias.

Cardiovascular diseases remain the major cause of death in the adult North American population. Most of these deaths are sudden, occurring secondary to ventricular tachycardia/fibrillation (VT/VF). Based on the results of recent clinical trials, it seems likely that many of these deaths could be prevented if reliable means were available to select those patients at highest risk. To date, however, no totally satisfactory means to establish risk has been identified. The purpose of this paper is to review the currently utilized techniques and to draw attention to some new and potentially useful technology involving computer processing of surface recorded electrocardiographic (ECG) signals. ECG monitoring during rest and activity is neither sensitive nor specific. Invasive studies, using programmed ventricular stimulation to reproduce clinical arrhythmias, have proven extremely useful in the management of patients with recurrent VT/VF; this technique allows the selection of effective therapy as documented by subsequent inability to induce the arrhythmia. However, this technique does not have broad applicability given the complexity of these studies and the significant potential for morbidity. Recent efforts have focused on the detection of the abnormal electrical substrate giving rise to VT/VF by using body-surface electrocardiographic recording. Two approaches are being investigated. In one, high-gain, signal-averaged ECG signals are being utilized to detect (delayed) depolarization potentials occurring during the repolarization process - an electrophysiologic state known to give rise to re-entrant arrhythmias. Initial results with this technique are encouraging. We have focused on another approach - that of body-surface potential mapping.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1984

Formaldehyde in the British chemical industry. An occupational cohort study.

This paper reports the mortality experience of a cohort of 7680 men who had first been employed before 1965 in one of six factories in the British chemical or plastics industry where formaldehyde had been manufactured or used. All the jobs undertaken by each man were classified, on the basis of subjective information, into four categories in terms of exposure to formaldehyde. More than 98% of the workforce were traced to the end of 1981. No deaths from nasal cancer were reported (1.07 expected), and no excess mortality was found for cancers at any of the sites previously reported to be possibly associated with formaldehyde. In one factory a significantly high mortality from lung cancer was found (standardised mortality ratio 124; 95% confidence limits 104, 148) when the mortality rates of England and Wales were used as a standard, but not when an adjustment was made based on the local area mortality. Within the factory the increased mortality was limited to men who had been exposed to "high" levels of formaldehyde. There were no trends of increasing mortality with duration of work or interval since first exposure. This result may be a chance finding or reflect the influence of smoking or some other factor. Although a carcinogenic action of formaldehyde seems less likely as an explanation it cannot be excluded. The statistical power of the study to detect various risks of nasal cancer is described.

Chemical Industry↗