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Biomedical subjects

A L Muir

Publications and source records attributed to A L Muir.

At least 19 recordsLinked to original sources

Computer skills and attitudes to computer-aided learning among medical students.

One hundred and forty-four third-year medical students at the University of Edinburgh were surveyed as to levels of computing skills and confidence in carrying out computing tasks. Attitudes to computer-aided learning for clinical teaching were also measured. Thirty-one per cent of students had not used a computer in the previous year and 38% had not used a computer outside supervised laboratory work. Twenty-two per cent had never used the university library computerized catalogue and 43% had never carried out a medline search using the library CD-ROM. Students were not confident of their ability to carry out simple computing tasks. Fifty-four per cent said they would need support or instruction in printing out a document, 69% were not confident they could copy a file onto a disk and 74% did not believe they could independently create a graph in a document. Students who had completed an intercalated honours year were significantly more skilled and confident in computing tasks. Attitudes to computer-aided learning were related to computing confidence. Medical students who have not acquired basic computer information technology (IT) skills by the third year of undergraduate training are unlikely to do so in the final hospital-based years. Undergraduate curricula for medical students must incorporate specific computer (IT) training.

Attitude to Computers↗

Acute effects of intravenous phosphodiesterase inhibition in chronic heart failure: simultaneous pre- and afterload reduction with a single agent.

Intravenous phosphodiesterase inhibition with milrinone is known to have a beneficial effect on haemodynamics in chronic heart failure. Its effect on lower limb capacitance vessels has not been previously investigated. We have studied the effect of intravenous milrinone in 10 patients with severe chronic heart failure. Thirty minutes after commencement of treatment mean cardiac index had risen by 26% and pulmonary artery wedge pressure, systemic vascular resistance and right atrial pressure had fallen by 51, 24 and 89%, respectively (p less than 0.05 for all changes). These changes were maintained for the 2 h observation period with no evidence of tolerance and were accompanied by a 17% increase in venous volume (p less than 0.01) and a 42% increase in ejection fraction (p less than 0.001) at 30 min; at 120 min the improvement in ejection fraction had been maintained and a further increase in venous volume to 38% above baseline was evident. The increase in venous volume was strongly correlated with the decrease in mean pulmonary artery wedge pressure and mean right atrial pressure at 30 min and 2 h (r = -0.80 and -0.69 for mean pulmonary artery wedge pressure, r = -0.88 and -0.56 for mean right atrial pressure). Milrinone therefore has clinically important venodilating properties, in addition to its known effects as an arterial vasodilator and a positive inotrope.

Aged↗

Haemodynamic responses to glyceryl trinitrate: influence of rate and duration of delivery.

Glyceryl trinitrate (GTN) is known to be a potent venodilator, but the effects might differ depending on the regime of administration. Using a radionuclide blood pool method we examined the changes in peripheral (and pulmonary) venous volume induced by GTN administered in three ways: short (4 min) intravenous infusions at 75 micrograms.min-1 (n = 7), prolonged intravenous infusion at 50 micrograms.min-1 (n = 7) or 500 micrograms sublingual tablet (n = 5). Sublingual GTN and the prolonged infusion caused similar decreases in systolic blood pressure (-23 +/- 12, -24 +/- 10 mmHg) and increases in calf venous volume (12 +/- 4%, 12 +/- 5%). For both, the peak effect occurred around 20 min after starting GTN administration (blood pressure 18 +/- 12 vs 25 +/- 12 min, venous volume 21 +/- 1 vs 22 +/- 7 min). Only the prolonged infusion caused a significant fall in diastolic pressure (-14 +/- 6 mmHg). The short infusion had a similar effect on systolic pressure (-21 +/- 16 mmHg) to the other two regimes, but caused a significantly smaller increase in venous volume (6 +/- 2%), which occurred much earlier (5 +/- 2 min). Anterior lung blood volume decreased in response to intravenous GTN and the posterior lung blood volume did not change, suggesting this alteration was secondary to peripheral venodilatation. In conclusion, GTN causes venous dilatation at low levels of delivery with the maximum response occurring after 20 min. In contrast, arterial effects are seen more rapidly and at higher rates of delivery.

Administration, Sublingual↗

Lack of variation in venous tone potentiates vasovagal syncope.

OBJECTIVE: To investigate the peripheral venous response to head up tilting in malignant vasovagal syndrome. PATIENTS: 31 Patients with unexplained syncope or dizziness referred from the cardiology department. METHODS: Changes in calf venous volume were studied by a radionuclide technique during 45 degrees head up tilt testing. RESULTS: During tilt testing six patients became syncopal but 25 were symptom free. The syncopal group had greater increases in calf venous volume after the change in posture and perhaps more importantly considerably less variability in the venous volume during the tilted period. CONCLUSIONS: The venous response was different in the syncopal patients. The lack of response of the peripheral venous circulation to changes in the central circulation may be responsible for triggering the Bezold-Jarisch reflex and malignant vasovagal syncope.

Adolescent↗

Early vasodilator treatment in myocardial infarction: appropriate for the majority or minority?

OBJECTIVE: To assess the influence of vasodilator treatment started early after myocardial infarction on left ventricular size and function. SETTING: Coronary care unit, Royal Infirmary, Edinburgh. PATIENTS: 105 patients with acute myocardial infarction (systolic blood pressure > 90 mm Hg) were randomised within 24 hours of the start of pain. Unlike previous studies 88% of the patients received thrombolysis. METHODS: Double blind randomised placebo controlled study with either 12.5 mg of captopril three times daily or 20 mg of isosorbide mononitrate three times daily for 28 days. MAIN OUTCOME MEASURES: Clinical outcome and left ventricular size and function assessed by echocardiography, radionuclide ventriculography, and magnetic resonance imaging. RESULTS: There was no difference in left ventricular size or function in either treatment group as measured one week after the end of the trial. Even the placebo group tended to decrease left ventricular diameter over the four week study period (one week: 5.0 (0.1) v, five weeks: 4.8 (0.1) cm, NS). Four patients had an adverse clinical outcome in the placebo group whereas no adverse outcome was seen in the captopril group. CONCLUSIONS: Vasodilator treatment may be of limited value or of no benefit for most infarct patients, particularly those treated with thrombolytic agents. Captopril, however, may benefit patients at high risk.

Captopril↗

Neutrophil count and activation in vascular disease.

An elevated peripheral leucocyte count is associated with an increased risk of myocardial infarction and progression of coronary artery disease. The aim of this study was to determine neutrophil count and activation, measured as an increase in plasma neutrophil elastase, in patients with stable ischaemic heart disease, insulin-dependent diabetes mellitus and essential hypertension compared with a comparable group of control subjects. Neutrophil count and neutrophil elastase were raised significantly for patients with ischaemic heart disease (p less than 0.005; p less than 0.002), diabetes mellitus (p less than 0.001; p less than 0.01) and hypertension (p less than 0.05; p less than 0.0001) respectively compared to the control subjects. Neutrophil elastase did not correlate with subject age or leucocyte count. This study confirms the association between leucocyte count and vascular disease, and is consistent with neutrophil activation contributing to the progression of vascular disease.

Adult↗

Central and peripheral haemodynamic responses to felodipine in congestive heart failure.

Using non-invasive radionuclide techniques, we studied the arterial and venous effects of 0.1 mg/kg oral felodipine in 12 men with heart failure due to ischaemic heart disease aged 37-72 y. All were in New York Heart Association Class II or III, required frusemide 40-120 mg daily and were clinically stable. Felodipine produced significant falls in blood pressure (-19%) and systemic vascular resistance (-39%) with increases in cardiac index (+34%), heart rate (+12%) and left ventricular ejection fraction (from 0.25 to 0.32). Peripheral venous volume fell by 10.6% after felodipine indicating venoconstriction rather than venodilatation and may be caused by an acute sympathetic reflex associated with the increase in heart rate. Our results confirm that felodipine is an arterial vasodilator. The previously observed changes in cardiac filling pressures may simply represent improved ventricular function as a consequence of reduced afterload, not venodilatation.

Adult↗

Modulation of venous tone in heart failure.

Venodilatation may be an important property in drugs used to treat heart failure. Deductions about venous tone from standard hemodynamic studies may be misleading since filling pressures may be reduced by improved left ventricular function. To study the venodilator properties of drugs, we have modified a radionuclide blood pool method and shown that venous volume is increased by 10% after glyceryl trinitrate but is unchanged after the arteriolar dilator hydralazine. In patients with congestive cardiac failure, the calcium channel blocker, felodipine, causes a marked reduction in systemic vascular resistance and left ventricular filling pressures, but venous volume remains unchanged. In a similar group of patients comparable arterial and central effects are seen after the administration of captopril, but venous volume increases by 16%, and this increased venous volume is sustained after 3 months of long-term treatment. Milrinone has been used to treat both acute and chronic heart failure. As expected of a phosphodiesterase inhibitor, it exhibits inotropic properties in animals and humans and also causes arterial vasodilatation. We have studied its effects on venous tone in 10 patients with severe heart failure (New York Heart Association classes III to IV). Milrinone was given intravenously at a loading dose of 50 micrograms/kg followed by an infusion of 0.5 micrograms/kg/min. After treatment, cardiac index, which was measured by thermodilution, increased from 1.8 +/- 0.48 to 2.3 +/- 0.65 L/min/m2 (p less than 0.001); pulmonary artery wedge pressure fell from 23 +/- 6 to 11 +/- 5 mm Hg (p less than 0.001); and systemic vascular resistance index decreased from 4296 to 3168 dynes.sec.cm-5/m2 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Captopril↗

The effects of captopril vs atenolol on memory, information processing and mood: a double-blind crossover study.

1. Measures of memory, information processing ability, mood states and trait anxiety were estimated in a double-blind, double-dummy, randomised cross-over trial which compared the effects of atenolol (50 or 100 mg once daily) and captopril (25 or 50 mg twice daily), each taken for 6 weeks. Eighteen patients with mild to moderately severe hypertension were included. 2. There were no significant differences in systolic or diastolic blood pressure reduction between the two drugs. Pulse rate was slower after atenolol treatment (P less than 0.05). 3. Patients undertook practice on the psychological test battery prior to the treatment phases of the study in order to minimise practice effects. 4. There were no significant differences between the treatments on any of the measures of memory or information processing. 5. Patients reported feeling less anxious during treatment with atenolol (P = 0.02). 6. There were no differences between the drugs in their cognitive effects. The present study has the advantages of using an extensive battery of standard tests in a group of well-practised patients. The decreased anxiety reported with atenolol treatment may have clinical value and probably reflects the well-known effect of beta-adrenoceptor antagonist drugs on the somatic symptoms of situational anxiety.

Adult↗

Estimating the size of myocardial infarction by magnetic resonance imaging.

OBJECTIVE: To develop a method to measure myocardial infarct size by magnetic resonance imaging and to compare the results with pyrophosphate scanning by single photon emission computed tomography. DESIGN: All patients underwent magnetic resonance imaging and pyrophosphate scanning 5-7 days after the onset of symptoms. Both measurements of infarct size were compared with the release of creatine kinase MB and with ventricular performance estimated by radionuclide ventriculography. PATIENTS: 19 patients (age 40-68 years) who had sustained their first uncomplicated myocardial infarction and who had not been treated with thrombolytic therapy. RESULTS: The site of infarction was clearly shown by both imaging techniques and was identical in each patient. The volume of infarcted tissue measured by magnetic resonance imaging agreed well with the infarct size measured by single photon emission tomography (mean difference 2.7 cm3). Correlations of both imaging techniques with the release of creatine kinase MB were best when total release rather than peak release was used. Both imaging techniques correlated closely with the subsequent ventricular performance. CONCLUSIONS: Magnetic resonance imaging after acute infarction allows measurement of infarct size and this may prove useful in assessing new treatments designed to salvage myocardium.

Adult↗

A preliminary study of the dopamine DA1 agonist fenoldopam in the treatment of chronic left ventricular failure due to ischaemic heart disease.

The effects of chronic oral fenoldopam in the treatment of NYHA grade II-III heart failure secondary to ischaemic heart disease, were studied in a placebo controlled, double blind, randomised, parallel group fashion in 20 patients. Nine patients taking placebo and six taking fenoldopam completed the study. Adverse events were similar in each group. There were no significant changes in exercise capacity, ejection fraction, body weight or symptom questionnaires with either treatment. This preliminary study has not revealed any benefit of fenoldopam in heart failure due to ischaemic heart disease.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

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↗

Imaging the pathology of myocardial infarction.

In order to measure the effectiveness of new therapies a technique is needed which can measure quantitatively in vivo pathology. In cardiology, the introduction of thrombolytic agents, which lyse the initial thrombus, has given added stimulus to the search for techniques which would fill this role. In this paper the extent to which nuclear medicine and magnetic resonance imaging can meet the requirements is discussed.

Humans↗

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↗

Inflammatory response, neutrophil activation, and free radical production after acute myocardial infarction: effect of thrombolytic treatment.

Activated neutrophils releasing proteolytic enzymes and oxygen free radicals have been implicated in extending myocardial injury after myocardial infarction. Neutrophil elastase was used as a marker of neutrophil activation and the non-peroxide diene conjugate of linoleic acid was used as an indicator of free radical activity in 32 patients after acute myocardial infarction; 17 were treated by intravenous thrombolysis. Patients with acute myocardial infarction had higher plasma concentrations of neutrophil elastase and the non-peroxide diene conjugated isomer of linoleic acid than normal volunteers or patients with stable ischaemic heart disease. Patients treated by thrombolysis had an early peak of neutrophil elastase at eight hours while those who had not been treated by thrombolysis showed a later peak 40 hours after infarction. The plasma concentration of non-peroxide conjugated diene of linoleic acid was highest 16 hours after the infarction irrespective of treatment by thrombolysis. Quantitative imaging with single photon emission tomography showed decreased uptake of indium-111 labelled neutrophils in the infarcted myocardium (as judged from technetium-99m pyrophosphate) in those who had received thrombolysis, suggesting a decreased inflammatory response. The results indicate increased neutrophil activation and free radical production after myocardial infarction; they also suggest that thrombolysis does not amplify the inflammatory response and may indeed suppress it.

Adult↗