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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
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↗
PubMed1979

An evaluation of six kits of technetium 99m human serum albumin injection for cardiac blood pool imaging.

We have investigated the suitability of five different commercially available kits which provide human serum albumin (HSA) labelled with technetium 99m (99mTc) for cardiac blood pool imaging. Four of these products were one-step processes using stannous chloride as the reducing agent; the fifth was based on an electrolytic reduction. In addition, we also assessed our own modification of the electrolytic method. We measured the radiochemical purity by precipitation with trichloroacetic acid and by gel filtration on a Biogel P4 column. In addition, we measured the clearance of radioactivity from the blood at frequent time intervals after intravenous injection. Each product was assessed in separate groups of six patients. The labelling efficiency of the one-step kits varied between 73 and 93% compared with 94 and 98% for the electrolytically labelled albumin. The blood clearance for all one-step kits was significantly faster than that obtained for the radiopharmaceuticals prepared by the electrolytic method. We conclude that HSA labelled with 99mTc by the electrolytic method is to be preferred.

Cardiac Volume↗
PubMed1977

Simplified method of determining left ventricular ejection fraction from a radionuclide bolus.

A method which does not require an online computer has been developed to measure left ventircular ejection fraction from a bolus of 99mTc-pertechnetate. The passage of the bolus through the cardiac chambers was imaged using a gamma camera and recorded on video tape. On replay a region of interest corresponding to the left ventricle was selected directly at the gamma camera console. Counts detected in this region were analysed in 30ms intervals. The data were corrected for the contribution from extra-cardiac activity and were then digitally filtered to remove statistical noise. Ejection fractions measured in 13 patients by this technique agreed well with those determined by contrast ventriculography (r=0.97, P less than 0.001).

Cardiac Output↗
PubMed1977

The assessment of left ventricular ejection fraction in patients with ischaemic heart disease by contrast ventriculography and nuclear angiography.

1. In 18 patients with ischaemic heart disease left ventricular ejection fraction, measured by two different nuclear angiographic methods, has been compared with ejection fraction measured by single-plane contrast angiography. 2. The first nuclear angiographic technique involves detection of variation in the radio-activity from the left ventricle during the initial passage of a bolus of 99Tcm-labelled human serum albumin injected intravenously; the second is our own modification of a "gated" method, which accumulates the radioactivity detected during the continuing recirculation of the plasma bound radioisotope, so presenting an "averaged" ventricular volume curve. 3. Ejection fraction, measured by the "bolus" method, is lower than that measured either by contrast ventriculography or by the "gated" method. This may be due to a damping effect. 4. Ejection fraction measured by the "gated" method is well correlated with that measured by contrast ventriculography (r = 0-89). 5. Our modification of the "gated" method, which presents the changes in ventricular volume throughout the cardiac cycle, without needing computer facilities, is a useful non-invasive means for assessment of left ventricular function.

Angiography↗
PubMed1975

A novel fast neutron dosemeter based on fission chambers. Part I: Principles of operation and theoretical response in neutron therapy radiation fields.

A novel method is proposed of accurately measuring fast neutron doses of interest in radiotherapy. The technique, which utilizes calculated neutron fluence-to-kerma conversion factors, is based upon the combination of measurements with calibrated neptunium-237 and uranium-238 pulse fission chambers to obtain a response which matches the variation of kerma with neutron energy. The theoretical performance of a practical instrument has been assessed for a variety of neutron spectra to evaluate the spectrum dependence of the dosemeter. The overall systematic uncertainty using this absolute method of determining the neutron dose under charged particle equilibrium conditions is comparable to that encountered with ionization chamber techniques.

Hot Temperature↗