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Biomedical subjects

W J Hannan

Publications and source records attributed to W J Hannan.

At least 19 recordsLinked to original sources
PubMed1995

Body mass index as an estimate of body fat.

Body mass index (BMI) was compared with percentage body fat (%Fat) measured by dual energy X-ray absorptiometry (DXA) in 233 adolescent schoolgirl volunteers and 179 adult female patients. Repeat measurements were made on 67 of the adolescents and 51 of the adults. The correlations between BMI and %Fat were established from the 300 adolescent measurements and the 230 adult measurements. Although highly significant relationships were found between BMI and %Fat, only 58% of the variance in %Fat in adolescents and 66% in adults could be predicted by BMI. At the 95% confidence levels, a BMI of 20 kg m-2 can correspond to a range of 18-33% body fat in adolescents and 13-32% in adults. Without any change in BMI, an adolescent's percentage fat can change by as much as -3% to +7%. For an individual adult the same BMI can correspond to changes in fat of +/-5%. Since the strength of prediction of percentage body fat from BMI is poor, caution should be exercised in its use for eating disorders research.

Absorptiometry, Photon↗
PubMed1995

Exercise-induced left ventricular dysfunction in alcoholic and non-alcoholic cirrhosis.

BACKGROUND/AIMS: Autonomic and cardiac dysfunction have been reported in patients with cirrhosis. We studied left ventricular and autonomic function in 20 patients with both alcoholic and non-alcoholic cirrhosis. METHODS: Autonomic function was assessed by a standard battery of cardiovascular reflex tests. Supine exercise radionuclide ventriculography was used to assess the cardiac response to exercise. RESULTS: Exercise capacity was reduced in all patients in association with marked chronotropic incompetence (peak heart rates 120.5 +/- 6 bpm). Unlike normal subjects there was no increase in left ventricular ejection fraction on exercise. Stroke volume increased by 23 +/- 6%, mediated by an increase in end-diastolic.volume of > 20%. Cardiac output was subnormal at maximal exercise, increasing by only 96 +/- 14% and 97 +/- 11% in alcoholic and non-alcoholic groups respectively. The majority (83%) of our patients had autonomic reflex abnormalities. CONCLUSIONS: Patients with cirrhosis of alcohol and non-alcohol related aetiologies have significantly impaired cardiovascular responses to exercise, which are similar to those of a denervated heart. This may have important clinical implications for the ability of these patients to withstand cardiovascular stress.

Autonomic Nervous System↗
PubMed1995

Improved prediction of bone mineral content and density.

To establish improved predictive values for normal bone mineral content (BMC) and density (BMD) in adolescent girls a community based study of schoolgirl volunteers was carried out by dual energy x ray absorptimetry. Measurements were performed on 216 subjects aged 11.0 to 17.9 years; measurements were repeated one year later on 84 of the girls, providing a total of 300 studies. For total body BMC the standard error of the prediction was improved from 290.9 g to 134.1 g when weight, height, and shoulder width were added to the normal variable of age. For spine BMD the standard error of the prediction was improved from 0.105 g/cm2 to 0.066 g/cm2 when height, weight, and shoulder width were added to the normal variable of age. Significant improvements were also obtained for total BMD and spine BMC. Despite the normal practice of predicting bone density from age alone this was not selected as the first variable in a multiple stepwise regression for either total body or spine. The prediction of BMC and BMD can be significantly improved by the inclusion of simple body habitus parameters in the prediction equations. As the mean (SE) z score derived from the manufacturer's normal data was - 0.36 (0.02) these American data are probably not appropriate for use in adolescents in the UK.

Absorptiometry, Photon↗
PubMed1994

Low bone mineral density in Crohn's disease, but not in ulcerative colitis, at diagnosis.

BACKGROUND/AIMS: The pathogenesis of low bone mineral density in patients with inflammatory bowel disease is unclear, and the relevance of secondary osteopenic influences is controversial. Our aim was to study bone mineral density in newly diagnosed patients. METHODS: Bone mineral density and biochemical parameters of bone metabolism were measured in 15 patients with Crohn's disease and 15 patients with ulcerative colitis, all of whom were newly diagnosed. Lumbar and forearm bone mineral densities were measured by dual energy x-ray absorptiometry, and Z scores were obtained by comparison with age- and sex-matched normal values. Twenty-three patients had repeat measurements 1 year later, and 20 had received systemic steroids. RESULTS: At diagnosis, the mean Z score for patients with Crohn's disease (spine, -1.06 +/- 0.86; forearm, -1.04 +/- 0.86) was significantly lower than that for patients with ulcerative colitis (spine, -0.03 +/- 1.16; forearm, 0.11 +/- 1.24). Inflammatory activity, disease localization, body mass index, smoking habits, sex, physical activity, or biochemical parameters did not account for this difference. Spine and forearm Z scores were significantly correlated. Mean Z scores after 1 year were not significantly different from initial Z scores. CONCLUSIONS: At diagnosis, low bone mineralization is a feature of Crohn's disease but not ulcerative colitis. Treatment with corticosteroids did not result in further bone loss in 1 year.

Adolescent↗
PubMed1994

Oral progestogen-only contraception may protect against loss of bone mass in breast-feeding women.

BACKGROUND AND OBJECTIVES: A worldwide trend towards increasing life expectancy has meant that osteoporosis is emerging as an important public health problem. The loss of bone mineral density and its restoration in association with a premenopausal but physiological hypo-oestrogenic state may serve as an important model for research into the pathogenesis and prevention of osteoporosis. With this in mind we have undertaken a longitudinal study of changes in bone mineral density over one year in women after childbirth. DESIGN: Observational study of 31 women in the first year following childbirth; 11 intending to breast-feed and use barrier methods of contraception, 9 intending to breastfeed and to use the progestogen-only pill and 10 intending to artificially feed and to use barrier methods. PATIENTS: Recruitment was from the antenatal clinics of the Simpson Memorial Maternity Pavilion. Only non-smokers who had regular menstrual cycles prior to conception were included. MEASUREMENTS: Bone mineral density was measured at the lumbar spine within 3 weeks of childbirth and repeated at 6 and 12 months post partum. Plasma oestradiol, prolactin and osteocalcin concentrations were measured at each visit. RESULTS: Breast-feeding women using barrier methods lost a mean +/- SE of 4.9 +/- 1.5% of bone mineral density in the first 6 months following delivery. This was however reversible since by one year the bone mineral density was no different from that measured immediately post partum. Breast-feeding women using the progestogen-only pill lost a significantly smaller percentage of bone mineral density in 6 months and by one year bone mineral density was 2.95 +/- 0.75% higher than post partum. Artificially feeding women had a steady increase in bone mineral density in the first year and bone mineral density was on average 4.3 +/- 1.2% higher. CONCLUSION: Breast-feeding results in a reversible reduction in spinal bone mineral density. The small amounts of gestagen in the progesterone-only pill would appear to protect against this loss. The mechanism of this loss in bone mineral density and the potentially bone protective effects of gestagens require further study.

Adult↗
PubMed1990

The haemodynamic effects of long term felodipine therapy in previously untreated essential hypertension.

Sixteen patients with previously untreated mild/moderate hypertension (WHO Stage I) were studied: 7 women and 9 men, mean age 56.2 y. Haemodynamics, central and pulmonary blood volumes were measured by radionuclide techniques and repeated after 8 weeks felodipine therapy. To achieve a target diastolic blood pressure of less than 95 mm Hg 12 patients required 5 mg bid, 2 10 mg bid and 1 2.5 mg bid; 1 withdrew after 2 weeks. Mean (SD) arterial blood pressure (mm Hg) was 189/106 before, and 182/103 after 2 weeks placebo treatment and fell to 148/84 after 8 weeks felodipine therapy. Relative systemic vascular resistance fell by 19% from 2146 to 1734 dyn.s.cm-5. There were no significant changes in heart rate, cardiac index, total blood volume, pulmonary blood volume or left ventricular ejection fraction. Plasma renin activity did not rise significantly. Short lived vasodilator side effects occurred in 7/16 patients during initial treatment and mild ankle oedema persisted in 4/16 patients. In contrast to the haemodynamic changes seen acutely with felodipine, the only sustained changes after 8 weeks therapy are reductions in systemic vascular resistance and blood pressure.

Adult↗
PubMed1990

Evaluation of bioelectrical impedance analysis for body composition measurements in anorexia nervosa.

Many established methods of measuring body composition are time consuming and require complex equipment which is not generally available. Bioelectrical impedance analysis is a technique which utilises the difference in conductivity between fat and lean tissues at radiofrequencies. It uses inexpensive equipment which is simple to use and does not involve the use of ionising radiation. We have evaluated this technique in 44 studies on 38 anorexic females with a wide range of body mass index. Fat free mass was obtained from the mean of three established methods. The initial calibration was derived from 21 studies on 19 anorexics. Fat free mass was regressed against impedance and body habitus parameters to establish the prediction equation with the smallest standard error (1.12 kg). Values of fat free mass derived using this prediction equation were then compared with the other methods in a prospective study. The error of the bioelectrical impedance technique compares favourably with the established methods, even in anorexic patients with very low body mass index.

Adult↗
PubMed1990

Radionuclide studies of left ventricular function in normal subjects.

The effects of age and exercise on cardiac function in a normal male population have been assessed by ECG-gated radionuclide ventriculography. Fifty-nine subjects aged from 25 to 54 years were studied (mean 44 +/- 10 S.D. years). Resting left ventricular ejection fraction (LVEF) was 0.54 +/- 0.07 and this increased by 0.07 +/- 0.05 during supine submaximal exercise at 75 watts. The mean increase in cardiac output on exercise was 93 +/- 30%. Stroke volume increased on exercise by 23 +/- 13% and end-systolic volume decreased by 10 +/- 16%. There was a weak correlation (P less than 0.05) between age and change in LVEF on exercise but the increase in cardiac output on exercise was not age dependent. It is important to use an age matched control population in any study of cardiac function.

Adult↗
PubMed1989

Acute and chronic arterial and venous effects of captopril in congestive cardiac failure.

OBJECTIVE: To determine whether captopril alters peripheral venous tone in patients with congestive cardiac failure. DESIGN: Open study of patients at start of captopril treatment and three months later. SETTING: A hospital gamma camera laboratory. PATIENTS: 16 Men with congestive cardiac failure in New York Heart Association class II or III, aged 57-73. INTERVENTIONS: Patients were initially given 500 micrograms sublingual glyceryl trinitrate followed by 25 mg oral captopril. The study was then repeated after three months' captopril treatment. MAIN OUTCOME MEASURES: Previously validated non-invasive radionuclide techniques were used to measure changes in central haemodynamic variables and peripheral venous volumes in the calf. RESULTS: After 25 mg captopril there were falls in blood pressure and relative systemic vascular resistance and increases in cardiac index and left ventricular ejection fraction. This was accompanied by a 16% increase in peripheral venous volume (95% confidence interval 13.4% to 18.4%, p less than 0.01), which compared with an 11% increase after 500 micrograms glyceryl trinitrate (10% to 12%, p less than 0.01). Eleven patients were restudied after three months' continuous treatment with captopril. The resting venous volume was higher than it had been initially, by about 10%, and increased by a further 8.4% after 25 mg captopril (5.4% to 11.4%, p less than 0.05). CONCLUSIONS: Captopril is an important venodilator. Venous and arterial dilatation are produced short term and during long term treatment.

Aged↗
PubMed1989

An introduction to body composition models used in nutritional studies.

Chemical analysis of cadavers has led to the definition of 'reference' man but diseases may result in significant changes in body composition. By measuring body composition in patient groups the nature of disease progression can be followed and management regimens evaluated. Various techniques are available which attempt to measure body composition in vivo. Several models of body composition have evolved with the introduction of new measurement techniques. A description of these models is presented. The limitations of the models and the techniques adopted for their measurement are discussed.

Body Composition↗
PubMed1986

Clinical value of radionuclide oesophageal transit measurement.

We have reviewed our experience of 150 patients to assess the clinical value of radionuclide oesophageal transit measurements in relation to established oesophageal motility investigations. Achalasia and conditions characterised by incoordinate oesophageal motor activity were detected with equal frequency by manometry and radionuclide transit measurement. Radionuclide transit measurements identified abnormalities not detected by manometry in 18 patients, and manometry was abnormal in 26 patients with normal radionuclide studies, including all patients with nutcracker oesophagus and most with hypertensive lower oesophageal sphincter. The overall sensitivity of radionuclide transit measurements in detecting oesophageal dysmotility was 75%, the sensitivity of manometry was 83% and that of conventional barium radiology 30%. We conclude that radionuclide transit measurement is a useful test for patients with suspected oesophageal motility disorders. Although it has limitations as a screening test, it provides additional information which complements oesophageal manometry.

Adolescent↗
PubMed1986

Diagnosis and prognosis of right ventricular infarction.

The values of several non-invasive methods for the diagnosis of right ventricular necrosis in inferior myocardial infarction were compared in 51 consecutive patients who underwent serial radionuclide ventriculography, pyrophosphate scintigraphy, and cross sectional echocardiography. In addition a unipolar electrocardiographic lead V4R was recorded on admission, daily, and during episodes of further pain. Profound right ventricular dysfunction was evident in 50% of patients studied by radionuclide methods after inferior myocardial infarction but recognition on clinical groups alone was poor. Functionally important right ventricular infarction was best detected and followed serially by radionuclide ventriculography. Echocardiographic methods for evaluating right ventricular ejection fraction correlated poorly with radionuclide methods. Increased uptake of radioactivity by the right ventricle on pyrophosphate scintigraphy usually indicated poor right ventricular function, but a scan that was negative in the right ventricular territory did not exclude dysfunction. ST segment elevation in V4R was not specific for right ventricular infarction and its routine use may lead to overdiagnosis of this condition. Serial measurements suggest that profound right ventricular dysfunction persists after acute inferior infarction and is associated with considerable morbidity and mortality. Of 25 patients with severe right ventricular dysfunction, six died in the late hospital period. In the remaining 19 patients mean right ventricular ejection fraction over a two month period did not improve; six patients had persistent right ventricular dyskinesia and features of chronic right ventricular failure developed in three survivors.

Adult↗
PubMed1985

Afterload reduction by nifedipine--the acute haemodynamic response to exercise in hypertensive subjects.

In 16 people with essential hypertension, heart rate (HR), blood pressure (BP) and relative cardiac volumes were measured at rest and during submaximal upright exercise before and after 10 mg of sublingual nifedipine using radionuclide ventriculography. In 10 patients who had had no previous therapy (BP 152/103 +/- 5/3 mmHg) nifedipine produced a fall in BP of 6/12 +/- 3/3 mmHg (SEM) and a rise in HR of 15 +/- 5 bpm (P less than 0.001). This was associated with a rise in LVEF of 0.07 +/- 0.02 (P less than 0.005) and in cardiac output of 44 +/- 9%, presumably as a result of ventricular offloading. The cardiac response to exercise given the different starting values, was unchanged by nifedipine. Thus the HR was 101 +/- 6 bpm at rest after nifedipine and on exercise rose to 124 +/- 6 bpm (P less than 0.001): stroke volume was +22 +/- 8% at rest after nifedipine and rose to +43 +/- 12% on exercise. Thus cardiac output which had increased by 44 +/- 9% after nifedipine increased by 100 +/- 10% from the initial value. In 6 patients pre-treated with atenolol (100 mg) and with similar resting BP (158/101 +/- 5/4 mmHg) there was a fall in BP of 32/15 +/- 3/2 mmHg after nifedipine which was greater than in the previously untreated group (P less than 0.01). In this group HR increased by 8 +/- 3 bpm (P less than 0.05). Following nifedipine the exercise response was similar given the different starting values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Regional tidal volume assessed by gated lung imaging.

We have measured regional lung tidal volumes and functional residual capacities by accumulating and framing iso-volumic images while the patient rebreathes 127Xe. As the lung changes shape during ventilation corrections for changes in geometry were obtained by simultaneous collection of 99Tcm counts from the gated perfusion scan. Regions of interest were made to vary throughout the respiratory cycle so that a region had always the same value of 99Tcm counts. From the corrected 127Xe counts regional tidal volumes (TVr) and functional residual capacities (FRCr) were derived. In patients with established chronic bronchitis and emphysema FRCr were greater and the ratio TVr/FRCr decreased compared with patients with relatively normal static and dynamic lung volumes. Preliminary studies suggest that this ratio was a better discriminator between normal and abnormal regional function than estimates of regional xenon washout. Studies with xenon-133 have contributed to our understanding of the physiology of ventilation but have contributed somewhat less to routine clinical practice. This results in part from the unsatisfactory physical properties of xenon-133. Its relatively low gamma ray energy of 80 keV results in significant self-absorption losses and the activity which may be administered is limited by the radiation dose from the associated beta particles so that relatively poor counting statistics are obtained. With inhaled technetium-99m (99Tcm) microspheres imaging conditions are greatly improved but the distribution of these particles may not equate with the distribution of ventilation particularly if wet particles are used. Moreover, simultaneous microsphere perfusion scans with technetium-99m as a label are impossible. Krypton-81m gas has a suitable energy but the short half-life of the rubidium-81m generator (4.7 h) makes supply difficult and the ultrashort half-life of the krypton-81m gas (13 s) leads to problems in calculating the indices of ventilation. Xenon-127 (127Xe) gas has a more favourable dosimetry profile than xenon-133 because it does not have associated beta particles. Further it has an energy (203 keV) suitable for modern gamma cameras and may be used in the presence of injected 99Tcm microspheres to provide simultaneous ventilation/perfusion imaging. Conventional techniques have assumed that a static image of a dynamic process is adequate. As the lungs move during imaging, some account of this respiratory movement should be made.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Effects of felodipine on resistance and capacitance vessels in patients with essential hypertension.

The acute cardiovascular effects of oral felodipine (0.05 mg/kg and 0.1 mg/kg) were studied using radionuclide methods in 14 hypertensive patients. Eight were previously untreated and 6 had been treated with atenolol 100mg daily for a least 1 month. The maximal effects were observed 60 minutes after the first oral dose and no greater effect was observed with the higher dose. Felodipine caused a reduction in systemic vascular resistance, with a fall in blood pressure and an increase in cardiac output and left ventricular ejection fraction. Those responses were presumably mediated by the reduction in afterload, as they were not modified by pretreatment with atenolol. There were no changes in venous capacitance and the overall pattern of response was similar to that noted with hydralazine. Thus, in hypertensive subjects felodipine acts as a potent arteriolar vasodilator. The results suggest the drug may be an effective means of controlling hypertension, particularly when given in combination with other antihypertensive therapy.

Adult↗
PubMed1985

Left ventricular performance in subclinical hypothyroidism.

Normal plasma thyroid hormones with elevation of thyrotrophin levels in asymptomatic patients is known as subclinical hypothyroidism. Radionuclide angiography was used to study left ventricular function in 10 such patients before and after establishment of normal thyrotrophin levels with thyroxine. Resting left ventricular ejection fraction was similar in both states but exercise left ventricular ejection fraction was less in the subclinical hypothyroid (61 +/- 3 per cent) compared with the euthyroid (68 +/- 3 per cent; p less than 0.025) state. Sodium nitroprusside caused similar increases in resting cardiac output but in subclinical hypothyroidism this resulted from a large increase in heart rate (26 +/- 4 beats/min) and reduction in stroke volume (11 +/- 4 per cent) whereas in the euthyroid state, the heart rate increment was less (14 +/- beats/min) and stroke volume was unchanged. Analysis of left ventricular pressure-volume relationships at end-systole during exercise showed a steeper pressure-volume slope in the euthyroid compared with the subclinical hypothyroid state (p less than 0.05). Subtle impairment of left ventricular function is detectable in subclinical hypothyroidism and may justify use of hormone replacement.

Adult↗