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Biomedical subjects

A L Muir

Publications and source records attributed to A L Muir.

At least 55 records · Page 3Linked to original sources
PubMed1986

Clinical effects and kinetic properties of intravenous APSAC--anisoylated plasminogen-streptokinase activator complex (BRL 26921) in acute myocardial infarction.

Fifty patients with a first myocardial infarction presenting within 4 hours of the onset of symptoms were treated with intravenous anisoylated plasminogen-streptokinase activator complex (APSAC-BRL 26921). Vessel patency with good flow was documented in 88%. The left ventricular ejection fraction declined with the duration of symptoms before treatment (r = -0.53, P less than 0.001). The correlation persisted for the group with anterior infarction (r = -0.46, P less than 0.05) where the mean left ventricular ejection fraction prior to discharge from hospital was 36 +/- 9% compared to 49 +/- 7% for the group with inferior infarction. Reinfarction developed in 12% and mortality at 6 months for the whole group was 6%. A degree of systemic fibrinolysis did occur with a fall in mean plasma fibrinogen from 3.20 g/l to 1.08 g/l. A pharmacokinetic study was performed in six patients demonstrating a clearance half-life of fibrinolytic activity of 87.5 +/- 5.0 min. APSAC is an effective intravenous thrombolytic agent with a relatively long half-life of fibrinolytic activity.

Adult↗
PubMed1986

Felodipine as a replacement for minoxidil in the treatment of severe hypertension.

The new calcium antagonist felodipine has been compared with minoxidil in the management of severe hypertension in a group of 17 men. Satisfactory control of blood pressure was achieved in all patients with a combination of beta blocker, loop diuretic and minoxidil after inadequate control on a standard regimen of beta blocker, thiazide and vasodilator. The optimal dose of felodipine was titrated after a placebo phase. In a double blind crossover trial blood pressure on felodipine (150/88 +/- 19/8 mmHg, SD) was the same as on minoxidil (148/87 +/- 23/11 mmHg, NS) and the postural difference was similar (NS) on both drug regimens. Body weight was lower on the felodipine regimen (P less than 0.01), as was supine heart rate (P less than 0.05). There was a small rise in plasma liver enzymes on felodipine therapy (P less than 0.01). Felodipine was well tolerated and may be useful in the management of severe hypertension.

Aged↗
PubMed1986

The preparation and in vivo behaviour of 111In-oxine labelled neutrophils separated from whole blood using mono-poly resolving medium.

using a single step separation procedure, we have developed a method for labelling human neutrophils with 111In-oxine. This method allows a rapid separation of neutrophils from whole blood, with negligible mononuclear or red cell contamination. Preliminary studies using 111In-labelled neutrophils show minimal lung retention and early accumulation in the spleen consistent with viable cells. In addition, focal accumulation of 111In has been imaged in patients with localized inflammation or sepsis.

Cell Separation↗
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↗
PubMed1986

A comparison of the effects of almitrine or oxygen breathing on pulmonary arterial pressure and right ventricular ejection fraction in hypoxic chronic bronchitis and emphysema.

Almitrine bismesylate is a new, orally administered, respiratory stimulant that improves arterial blood gas tensions in patients with chronic bronchitis and emphysema, and it may have an effect on the pulmonary circulation and on right ventricular performance. We have, therefore, compared the effects of Almitrine with those of oxygen (given as 3 L/min by nasal prongs) on arterial blood gas tensions, mean pulmonary arterial pressure (Ppa), and right ventricular ejection fraction (RVEF) measured both at rest and during exercise in patients with chronic hypoxemia caused by chronic bronchitis and emphysema. Arterial oxygen tension improved significantly both at rest and during exercise after either 100 mg Almitrine by mouth or when breathing oxygen, both at rest and during exercise. Almitrine increased the mean Ppa at rest from 22 +/- 4 to 35 +/- 5 mmHg (p less than 0.001), and mean Ppa rose further during exercise from 38 +/- 5 mmHg before Almitrine to 49 +/- 7 mmHg (p less than 0.001) after Almitrine. In contrast, oxygen breathing did not change Ppa when at rest but reduced the amount of rise in Ppa during exercise. The change in Ppa after Almitrine correlated with the plasma Almitrine concentration (r = 0.69, p less than 0.05) and was associated with a fall in RVEF at rest from 0.38 +/- 0.03 to 0.32 +/- 0.02 (p less than 0.001). In 5 of the patients who received 50 mg of Almitrine by mouth twice daily for 3 months, the Ppa both at rest and during exercise remained significantly higher than in the control study before receiving Almitrine, but RVEF was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Use of nifedipine as the drug of third choice in management of hypertension.

Nifedipine has been used in the management of hypertension in 36 consecutive patients who could not tolerate, or were not controlled by, atenolol and thiazide diuretics. Mean supine blood pressure was reduced from 193/110 +/- 5/2 (SEM) mmHg to 162/91 +/- 5/2 mmHg at eight weeks and remained at that level for the six months of follow-up. Blood pressure reduction at four weeks was not always a predictor of final BP level. Eight patients could not tolerate atenolol, nine patients could not tolerate thiazide diuretics and four patients could not tolerate nifedipine. No significant changes in plasma urea, creatinine, sodium, potassium urate, 'total CO2' or glucose were observed. We conclude that nifedipine is a well-tolerated drug and may be useful after beta-blockers and thiazide have been tried in the management of hypertension.

Adult↗
PubMed1986

The effect of captopril on blood pressure and glucose tolerance in hypertensive non-insulin dependent diabetics.

Thirteen hypetensive non-insulin dependent diabetics (9 male, 4 female, mean age 61.6 +/- 6 years) were given 6 weeks treatment with captopril in a dose range 75-150 mg/day. Each patient underwent a standard glucose tolerance test and had blood pressure profiles recorded before and after captopril. Supine systolic blood pressure (mmHg) improved from 181 (+/- 16) to 162 (+/- 17) and diastolic blood pressure from 103 (+/- 11) to 89 (+/- 9). A similar improvement was seen in erect systolic (174 +/- 19 to 156 +/- 19) and diastolic (103 +/- 14 to 87 +/- 11) blood pressures. Following treatment there was no significant change in glucose tolerance although the 120 minute plasma glucose value improved from 15.3 +/- 4.2 to 13.9 +/- 3.4 mmol/l (P less than 0.05). The drug was well tolerated and free of adverse effects. Captopril would therefore appear to be an effective and safe anti-hypertensive agent in non-insulin dependent diabetes and did not result in any deterioration of glucose tolerance.

Aged↗
PubMed1985

Characterisation of acute myocardial infarction by gated magnetic resonance imaging.

In studies with gated nuclear magnetic resonance imaging, patients with recent transmural myocardial infarction showed significantly longer spin-lattice relaxation times (T1) in the infarct area than did healthy volunteers or patients with non-ischaemic or chronic ischaemic heart disease. 10 of the 13 patients had a T1 longer than that found in any healthy subject or in any patient with other heart disease. Changes in T1 should prove useful in the assessment of interventions designed to limit infarct size.

Adult↗
PubMed1985

Clinical significance of "reciprocal" S-T segment depression in acute myocardial infarction. Relative contributions of infarct size and ischemia at a distance.

The early electrocardiographic results in 100 patients surviving their first myocardial infarction who thereafter underwent serial radionuclide ventriculography were reviewed. Site of infarction was anterior in 46 and inferior in 54, with lateral extension in two patients. Those with "reciprocal" S-T segment depression of more than 1 mm in the acute phase (n = 53) sustained larger infarcts on the basis of enzyme criteria (mean peak serum creatine kinase, +/- SD, 2,203 +/- 1,271 versus 1,544 +/- 1,197 IU/liter, p less than 0.02), with a higher incidence of ventricular akinesis and dyskinesis. Reciprocal change was more common during inferior infarction (n = 33) than anterior infarction (n = 20). Despite equivalent peak enzyme levels following anterior and inferior infarction with reciprocal S-T depression (mean peak creatine kinase 2,330 versus 2,128, NS), there was marked sparing of left ventricular function in the latter group (mean left ventricular ejection fraction 0.31 +/- 0.14 versus 0.42 +/- 0.09, p less than 0.01). Of 17 patients who died within two years of infarction, 14 had reciprocal changes. Patients who died after anterior infarction with reciprocal changes (n = 5) had poor left ventricular function compared with those who died after inferior infarction (n = 9; left ventricular ejection fraction, +/- SD, 0.21 +/- 0.05 versus 0.38 +/- 0.11, p less than 0.01). One third of those recovering from inferior infarction with reciprocal changes subsequently had positive results on exercise testing, and of the nine patients who died, five had good left ventricular function (left ventricular ejection fraction 0.44 to 0.50). Infarct size and ventricular wall motion abnormality proved to be of major importance in the production of inferior reciprocal S-T change during anterior infarction, and subsequent mortality was related to poor left ventricular function. The proximity of the precordial leads to left ventricular myocardium may increase the detection of concomitant anterior ischemia during inferior infarction, and those who exhibit reciprocal change are presumably at risk from left main stem or anterior descending lesions but with reasonably good ventricular function represent a more attractive population for invasive investigation.

Creatine Kinase↗
PubMed1985

Haemodynamic and endocrine responses of the kidney to frusemide in mild essential hypertension.

Prostaglandin-dependent, frusemide-induced changes in renal plasma flow, glomerular filtration rate and plasma renin activity were measured in 14 patients with mild essential hypertension. The renal haemodynamic responses to frusemide were the same as in 10 normal subjects. Frusemide-induced changes in urinary PGE and kallikrein excretion were also the same as in normal subjects. Impaired renal release of vasodilator prostaglandins in essential hypertension is likely to be secondary to the hypertension rather than an underlying factor in its development.

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

Are the clinical benefits of oral prenalterol in ischaemic heart failure due to beta blockade? A six month randomised double blind comparison with placebo.

The clinical effects of the oral beta 1 partial agonist, prenalterol, were investigated in 37 patients (29 male, eight female; mean age 57 years) with chronic ischaemic left ventricular failure using a placebo controlled randomised double blind protocol over six months. All patients were limited by dyspnoea (New York Heart Association class III) despite treatment with digoxin and diuretics. Twenty eight patients completed the protocol. Moderate clinical improvement was seen in the prenalterol group, whereas there was little change in the placebo group. Bicycle exercise capacity increased over six months in the prenalterol and placebo groups but only achieved statistical significance for prenalterol when compared with baseline values. Maximum exercise heart rate was significantly reduced in the prenalterol group compared with placebo. Radionuclide left ventricular ejection fraction at rest and during exercise and cardiothoracic ratio showed no significant improvement in either group over six months. Prenalterol was well tolerated and produced no increase in frequency of angina or ventricular arrhythmias. Prenalterol produced clinical benefits and improved exercise tolerance while reducing exercise heart rate. A moderate placebo response was noted. The apparent beta blocking effect of prenalterol may be as important as the beta 1 agonist effect in producing these benefits. Prenalterol has, however, been withdrawn because of side effects in animals.

Adrenergic beta-Agonists↗
PubMed1985

Coronary thrombolysis with intravenous anisoylated plasminogen-streptokinase complex BRL 26921.

BRL 26921 is a protected plasminogen-streptokinase complex with selective affinity for thrombus. When given intravenously within three hours of the onset of a first acute myocardial infarction angiographic patency of the infarct related vessel was seen in all 16 patients receiving the active drug compared with only two of 16 receiving a placebo. There was relative sparing of left ventricular function in the active treatment group with anterior infarction (mean left ventricular ejection fraction 37% compared with 23% for placebo), but no significant difference in left ventricular function between the active and placebo groups was seen in patients with inferior infarction. Intravenous BRL 26921 is highly effective in causing coronary reperfusion and may help to preserve left ventricular function when given early in the course of anterior infarction.

Adult↗
PubMed1985

Nuclear magnetic resonance in hypertrophic cardiomyopathy.

The large differences in the spin lattice relaxation times (T1) of blood and myocardium (measured by nuclear magnetic resonance) allow the heart to be visualised without the use of contrast media. The findings using nuclear magnetic resonance in 11 unselected patients with hypertrophic cardiomyopathy were compared with those in equal numbers of normal subjects and patients with electrocardiographic features of left ventricular hypertrophy. In patients with hypertrophic cardiomyopathy characteristic septal hypertrophy was noted together with variable and sometimes pronounced hypertrophy of the left ventricular free wall, which is consistent with the heterogeneous nature of this disease. The mean (SD) ratio of septal to free wall thickness was 1.5(0.8) for patients with hypertrophic cardiomyopathy, 0.8(0.2) for those with left ventricular hypertrophy, and 0.9(0.2) for normal subjects. Although septal measurements by nuclear magnetic resonance were greater than those obtained by echocardiography there was a significant correlation between the two. Septal and free wall area were significantly smaller in normal subjects. There were no differences in septal or free wall T1 values between the three groups. Non-gated nuclear magnetic resonance can detect septal and free wall hypertrophy. With the addition of multiple slice acquisition, rapid estimation of myocardial mass will be possible allowing the potentially important assessment of progression or regression of myocardial hypertrophy.

Adult↗