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Biomedical subjects

A L Muir

Publications and source records attributed to A L Muir.

At least 37 records · Page 2Linked to original sources
PubMed1990

Assessment of the right ventricle by magnetic resonance imaging in chronic obstructive lung disease.

Right ventricular wall and chamber volume were measured by magnetic resonance imaging in 16 patients with stable chronic obstructive lung disease who subsequently underwent measurement of pulmonary haemodynamics by right heart catheterisation. The patients had a forced expiratory volume in one second of 0.7 (SD 0.3) litres, a forced vital capacity of 2.4 (1.0) l, an arterial oxygen tension (PaO2) of 6.5 (1.3) kPa, an arterial carbon dioxide tension (PaCO2) of 6.5 (1.0) kPa, and a mean pulmonary arterial pressure 30 (10) mm Hg. The mean right ventricular free wall volume was 57.1 (22.6) cm3, compared with a mean value of 115.0 (44.3) cm3 for the left ventricle and interventricular septal volume. The right ventricular chamber volume at end systole was 44.8 (23.4) cm3, whereas the left ventricular end systolic chamber volume was 51.1 (35.1) cm3. The right ventricular free wall volume correlated with the right ventricular chamber volume (r = 0.71), systolic (r = 0.74) and mean (r = 0.72) pulmonary arterial pressure, pulmonary vascular resistance (r = 0.67), and PaCO2 (r = 0.56). There was no significant correlation between the right ventricular free wall volume and PaO2 or the right ventricular ejection fraction, measured by radionuclide ventriculography. Assessment of the right ventricle by magnetic resonance imaging may help to better define patients with cor pulmonable and assess the long term effects of treatment in such patients.

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

A trial of the calcium antagonist felodipine in hypertensive type 2 diabetic patients.

Although calcium antagonists may impair insulin release in vitro, clinical studies have produced conflicting results. Felodipine is a highly selective dihydropyridine calcium antagonist effective in the treatment of hypertension. The efficacy of felodipine was assessed in a double-blind randomized placebo cross-over study of 21 Type 2 diabetic patients with primary hypertension, 13 men and 8 women, with an age of 61 (range 46-73) years. Thirteen were controlled on oral hypoglycaemic therapy and 8 on diet alone. Mean (SD) blood pressure (mmHg) was 176(20)/102(8) after a 2-4 week placebo run-in period, 169(21)/101(8) during the subsequent placebo period compared with 151(15)/88(9) after 4 weeks felodipine therapy (p less than 0.001). Nineteen patients required 5 mg twice daily and 2 patients 10 mg twice daily to achieve a target diastolic pressure of 95 mmHg. Side-effects seen with felodipine included ankle oedema, facial flushing, headache, and dizziness. During oral glucose tolerance tests performed after the felodipine and placebo phases, mean (SD) fasting blood glucose was 9.5(3.1) and 9.0(3.0) mmol l-1, respectively (NS), and the 90 min (peak) blood glucose was 19.1(4.8) and 18.1(4.8) mmol l-1, respectively (NS). Glycosylated haemoglobin and fructosamine concentrations likewise showed no significant changes.

Apolipoproteins↗
PubMed1988

Myocardial involvement in systemic lupus erythematosus detected by magnetic resonance imaging.

Myocardial involvement in systemic lupus erythematosus is commonly found at autopsy but seldom recognized clinically or by routine cardiological investigations. As the magnetic resonance relaxation parameter, T1, is altered by changes in tissue cellularity, we carried out magnetic resonance imaging in 10 patients with systemic lupus erythematosus. Five had active systemic lupus erythematosus when assessed using the lupus activity criteria count. The mean (+/- SD) T1 was 319 +/- 12 in normal volunteers and 321 +/- 10 in a second control group with hypertrophic cardiomyopathy. In the group with systemic lupus erythematosus, there was a higher mean value of 336 ms with a wider scatter of individual results (SD +/- 22 ms). In the subgroup of patients with active disease, T1 was significantly higher (349 +/- 24) than in either of the two control groups. In addition, there was an inverse correlation between serum complement and myocardial T1 in patients with systemic lupus erythematosus. Myocardial abnormalities in systemic lupus erythematosus were demonstrated by magnetic resonance imaging even where other non-invasive cardiac investigations were negative. We conclude that T1 calculated from magnetic resonance imaging is often abnormal in systemic lupus erythematosus and probably indicates myocardial involvement.

Adult↗
PubMed1988

Altered lung vascular permeability during intermittent haemodialysis.

Hypoxia is known to develop during intermittent haemodialysis. To investigate if increased pulmonary capillary permeability to protein contributes to this phenomenon, a dual-isotope technique using Indium-labelled transferrin and Technetium-labelled red blood cells was used. Lung vascular permeability was measured in eight patients with dialysis-dependent chronic renal failure immediately before and during intermittent haemodialysis with cuprophane membranes. As a group there was a significant increase in lung vascular permeability during the early stages of haemodialysis, compared to predialysis values (P less than 0.05) and this increase occurred during the period when the patients were leucopenic and maximally hypoxic. During the haemodialysis period, but not the predialysis period, the permeability index was also significantly increased compared to a group of eight controls (P less than 0.05). These results suggest that increased vascular permeability may contribute to dialysis-induced hypoxia and that this may relate to neutrophil activation within the pulmonary vascular bed.

Adolescent↗
PubMed1988

Serial changes in the T1 magnetic relaxation parameter after myocardial infarction in man.

A low field resistive nuclear magnetic resonance imaging system (0.08 Tesla) was used to study the in vivo changes in the relaxation parameter T1 of the left ventricular myocardium from the first day to six months after acute myocardial infarction in 41 consecutive patients admitted to a coronary care unit. T1 maps were constructed from transverse and coronal images at various times after infarction. Thrombolytic treatment had been successful in 28 patients. Thirty three of the 34 patients studied within two weeks of infarction had a significantly increased T1 value but this developed only after the third day in four. At day 1-3 the mean (1 SD) maximum T1 was 413 (29) ms (n = 23) compared with 430 (41) ms (n = 22) at day 4-7, 433 (35) ms (n = 24) at day 8-14, 420 (34) at one month (n = 22), 388 (39) (n = 20) at three months, and 361 (24) (n = 14) at six months. The number of regions of interest with an increased T1 followed a similar time course. Although the increase in T1 measured at three months correlated with the initial maximum creatine kinase and with the left ventricular ejection fraction measured at one month, the number of regions with abnormal T1 from day 4 through to one month correlated best with left ventricular ejection fraction. There was no significant difference in T1 between patients with or without reperfusion. The rise in T1 over the first few days together with the prolonged time course of T1 increase suggests that the increase in T1 may reflect cellular infiltration as much or more than tissue oedema.

Adult↗
PubMed1988

Does right ventricular function predict survival in patients with chronic obstructive lung disease?

Non-invasive measurements of the right ventricular ejection fraction by radionuclide ventriculography were made in 115 patients with chronic obstructive lung disease. Survival was assessed over a mean period of 918 days. The right ventricular ejection fraction was reasonably normal in most patients (mean 0.42, range 0.10-0.66) but was lower in those with peripheral oedema, indicating cor pulmonale (mean 0.31 (SD 0.07); p less than 0.0001). Right ventricular ejection fraction was related to survival, but the relationship was weak (p = 0.03) by comparison with the association between the arterial oxygen and carbon dioxide tensions and survival (both p less than 0.0001). It is concluded that, although right ventricular function is predictive of survival in patients with chronic obstructive lung disease, it is probably a reflection of severity of disease and does not directly affect the prognosis.

Adult↗
PubMed1988

Regional distribution of ventilation in chronic obstructive lung disease and the effect of salbutamol.

Regional distribution of ventilation was assessed in 5 normal volunteers, and 19 patients with symptomatic chronic obstructive lung disease (COAD) using the technique of gated lung ventilation imaging with 127Xe. The results of this technique were compared with the more conventional assessment of regional ventilation by analysis of 127Xe wash-out curves. Both techniques demonstrate loss of the normal gravitational distribution of ventilation in patients with severe COAD which is significantly reduced from normals in upper, middle and lower zones of each lung, being most marked in the lower zones (p less than 0.01). Gated lung imaging also shows a significant reduction of regional ventilation in patients with mild to moderate COAD compared to normals but only in the lower zones (p less than 0.05). Gated lung imaging provides a better quantitative method of assessing regional lung function than wash-out analysis and confirms loss of the normal gravitational distribution of ventilation in patients with obstructive lung disease and relates this to severity of disease. The distribution of ventilation was also assessed in 6 patients with severe COAD before and after placebo or salbutamol. There was a significant improvement of the distribution of ventilation to the lung bases after salbutamol (p less than 0.05).

Adult↗
PubMed1988

Pulmonary hypertension and right ventricular function in patients with COPD.

In 100 patients with chronic obstructive pulmonary disease (COPD), we found no significant correlation between simultaneous measurements of right ventricular ejection fraction, using radionuclide ventriculography, and pulmonary arterial pressure. There was, however, a weak but significant correlation between right ventricular ejection fraction and the pulmonary vascular resistance (r = 0.40, p less than 0.005). In 52 of these patients, 37 with pulmonary hypertension, right ventricular end-systolic volume index was 53 +/- 21 ml.m-2 and end-diastolic volume index was 86 +/- 27 ml.m-2, compared with a calculated mean of 33 ml.m-2 and 79 ml.m-2, respectively, for normal subjects. In 24 of these patients where the measurements were made at rest and on exercise, the mean right ventricular end-systolic volume increased from 66 +/- 20 ml.m-2 to 87 +/- 32 ml.m-2, with an increase in right ventricular systolic pressure from 28 +/- 9 mm Hg to 55 +/- 15 mm Hg. Analysis of the slope of the right ventricular end-systolic pressure volume relationship at rest and on exercise suggested relatively normal right ventricular contractility in the majority of patients. Thus, in these patients with stable COPD, despite the presence of pulmonary hypertension, right ventricular contractility remained relatively normal.

Blood Pressure↗
PubMed1987

The acute inflammatory response to myocardial infarction: imaging with indium-111 labelled autologous neutrophils.

The uptake of indium-111 labelled neutrophils was examined in 30 patients with acute myocardial infarction by planar imaging and single photon emission computed tomography. The time from venepuncture to reinjection of the autologous labelled neutrophils was less than 2.5 hours and imaging was carried out 24 hours later. Twenty three patients had a positive uptake of neutrophils in the myocardium and imaging was improved by single photon emission computed tomography. There was a significant difference between the intervals from the onset of chest pain to injection of labelled neutrophils between patients with positive and negative images; early reinjection was more likely to produce a positive image. Indeed, all nine patients reinjected within 18 hours of the onset of symptoms had positive images. The results suggest that the stimulus for activation and migration of neutrophils is transient; this is an important factor if neutrophil release products play a role in cell damage after coronary occlusion.

Acute Disease↗
PubMed1987

Carbonated drinks, thiamine deficiency and right ventricular failure.

A 69 year old male presented with clinical features of right ventricular failure. A dilated poorly contracting right ventricle was confirmed by echocardiography and radionuclide ventriculography, with subsequent improvement following thiamine replacement. Wet beriberi is a result of thiamine deficiency and is uncommon in Europe and North America except in association with chronic alcohol abuse. We report a patient with beriberi presenting unusually with severe right-sided cardiac failure, with documented impairment of right ventricular function, which improved with thiamine replacement. His dietary intake of thiamine was low because of excess intake of carbonated drinks and carbohydrates.

Aged↗
PubMed1987

Left ventricular function after anisoylated plasminogen streptokinase activator complex.

Limitation of the reduction in left ventricular function after acute myocardial infarction is an important indicator of benefit following thrombolytic therapy. Therefore, left ventricular function was studied by radionuclide ventriculography in 91 patients entering 3 separate studies of anisoylated plasminogen streptokinase activator complex (APSAC) administered within 4 hours of acute myocardial infarction. Global left ventricular ejection fraction was measured at 10 days and at 6 months to assess early and late effects of therapy, with particular emphasis on the timing of treatment and the site of infarction. Successful therapy with APSAC in anterior infarction resulted in preservation of left ventricular function at 10 days. The magnitude of benefit declined with increasing symptom duration before treatment, and was maintained at 6 months in those patients without reocclusion. The benefit of successful therapy was less marked in the inferior infarct group at 10 days. By 6 months, no significant benefit was detected because of an increase in ejection fraction in the placebo and occlusion or reocclusion group with inferior infarction. Early therapy results in greater preservation of left ventricular function, and recovery of function may be more rapid than with later treatment. More emphasis on early administration of thrombolytic therapy is indicated.

Anistreplase↗
PubMed1987

The use of felodipine in the treatment of severe hypertension.

To investigate the use of felodipine in severe hypertension 2 separate studies were carried out. In the first study, 101 patients on a fixed combination of atenolol 100mg and chlorthalidone 25mg who required additional or 'third line' therapy for proper control, were randomised to either felodipine or hydralazine and the dosage was increased if the supine diastolic blood pressure was greater than 90mm Hg. Felodipine reduced blood pressure more effectively than hydralazine and the incidence of adverse reactions was similar in both groups. In the second study, 17 patients with severe hypertension (WHO stage III), who had not been controlled by therapy with atenolol, thiazide diuretic and hydralazine, prazosin or nifedipine were studied. Patients were subsequently controlled by a combination of atenolol, frusemide or bumetanide, and minoxidil. Once stabilised, the patients then took part in a double-blind crossover study comparing minoxidil and felodipine. The patients' blood pressure was the same on both treatment regimes but their bodyweight was lower after felodipine administration. Felodipine is probably more effective than hydralazine and as effective as minoxidil in treating severe hypertension. As felodipine is usually well tolerated it should prove a useful drug in treating refractory hypertension.

Antihypertensive Agents↗
PubMed1987

The use of captopril and captopril plus frusemide as antihypertensive agents in non-insulin dependent diabetes.

After all previous antihypertensive treatment had been stopped, blood pressure and glucose tolerance were measured in 16 hypertensive non-insulin treated diabetics before and again six weeks after treatment with captopril, an angiotensin-converting enzyme inhibitor. Supine blood pressure fell from 184 +/- 4.1/103 +/- 2.6 to 165 +/- 5.2/88 +/- 2.1 mmHg (P less than 0.001) and erect from 179 +/- 5.2/102 +/- 3.2 to 158 +/- 5.6/87 +/- 2.6 mmHg (P less than 0.005). The area under the oral glucose tolerance curve fell from 2313.6 +/- 154 to 2192.8 +/- 146 mmol/min/l (P less than 0.02). There was no change in plasma insulin, total glycosylated haemoglobin or fructosamine. Four patients who failed to show lowering of supine diastolic pressure below 95 mmHg were additionally given oral frusemide with further improvement in blood pressure and no alteration in carbohydrate intolerance. It was concluded that captopril alone is usually an effective antihypertensive agent in non-insulin dependent diabetes with the addition of frusemide benefiting resistant cases. Glucose intolerance did not worsen with either captopril alone or captopril plus frusemide.

Blood Glucose↗