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Biomedical subjects

R A Stewart

Publications and source records attributed to R A Stewart.

At least 37 records · Page 2Linked to original sources
PubMed1997

Imaging and pathological features of primary malignant rhabdoid tumours of the brain and spine.

In this article two cases of primary malignant extrarenal rhabdoid tumour are described. In the affected children the brain and the spinal cord were the primary sites of origin of the tumour. The imaging findings are presented and the pathology discussed. Although the imaging features are non-specific, rhabdoid tumour should be included in the differential diagnosis of childhood intracranial and spinal neoplasms.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Pictorial review: the imaging features of male breast disease.

Although breast carcinoma in men is rare, the presentation of a male patient with evidence of breast enlargement or of a palpable lump, is not uncommon. In such patients, radiological assessment may be requested to exclude malignant change. Mammography has been traditionally the dominant modality of investigation, although ultrasound, using high-frequency linear transducers, is playing an increasingly important role for both imaging and biopsy and the two techniques should be regarded as complementary. In this article the pathological conditions which may affect the male breast are reviewed and the imaging findings presented.

Adult↗
PubMed1997

Association between activity at onset of symptoms and outcome of acute myocardial infarction.

OBJECTIVES: This study sought to compare the clinical features and outcome of a first myocardial infarction with onset of symptoms during or within 30 min of exercise, at rest and in bed. BACKGROUND: It is not known whether activity at onset influences outcome of acute myocardial infarction. METHODS: Information collected using a standard questionnaire was used to relate activity at the onset of symptoms to in-hospital outcome in 2,468 consecutive patients admitted to a coronary care unit with a first myocardial infarction between 1975 and 1993. RESULTS: Patients with exercise-related onset were more likely to be younger and male. Those with onset in bed were more likely to be older and have a history of stable or unstable angina. Compared with patients whose symptoms began at rest, those with exercise-related onset had a lower in-hospital mortality rate after adjusting for age, gender and year of admission (odds ratio [OR] 0.60, 95% confidence interval [CI] 0.40 to 0.89), and patients with onset in bed had a higher mortality rate (OR 1.38, 95% CI 1.03 to 1.85). The incidence of cardiac failure requiring diuretic therapy was also lower for exercise-related onset (OR 0.83, 95% CI 0.67 to 1.04) and higher when onset was in bed (OR 1.36, 95% CI 1.11 to 1.66). CONCLUSIONS: There is an association between activity at onset and outcome of acute myocardial infarction. Differences in pathophysiology or in the population at risk could explain this observation.

Aged↗
PubMed1997

Progression of the culprit lesion in unstable coronary artery disease with warfarin and aspirin versus aspirin alone: preliminary study.

OBJECTIVES: This study assessed whether combination therapy with aspirin and warfarin for 10 weeks reduces the risk of progression or reocclusion of the unstable coronary artery lesion. BACKGROUND: Reocclusion of the culprit coronary artery occurs in up to one third of patients during the 3 months after myocardial infarction (MI) or unstable angina and is associated with increased morbidity and mortality. METHODS: Fifty-seven patients presenting with unstable angina or MI who had an identifiable culprit lesion at coronary angiography were randomized in double-blind manner to receive warfarin (target international normalized ratio [INR] 2.0 to 2.5) or placebo in addition to aspirin (150 mg daily). Changes in the culprit lesion were assessed by quantitative angiography in 50 patients after 10 weeks of therapy or after a clinical event. Progression of the culprit lesion was defined as a decrease in minimal lumen diameter > 0.4 mm or a new total occlusion. Regression was defined as an increase in minimal lumen diameter > 0.4 mm. RESULTS: In subjects randomized to receive warfarin, the culprit lesion was less likely to progress (1 [4%] vs. 8 [33%]) and more likely to regress (5[19%] vs. 2[9%]) than in subjects receiving placebo (p = 0.02). Recurrent MI or a new occlusion at angiography occurred in 2 (7%) of 29 patients receiving warfarin versus 11 (39%) of 28 patients receiving placebo (p = 0.005). CONCLUSIONS: In patients with an acute coronary syndrome, combined therapy with aspirin and warfarin with a target INR of 2.0 to 2.5 for 10 weeks reduces the risk of progression or reocclusion of the culprit coronary lesion.

Angina, Unstable↗
PubMed1997

Serial angiography in cocaine-induced myocardial infarction.

A young man suffered an acute inferior myocardial infarction following clinical use of cocaine as topical anesthesia. Coronary angiography showed occlusion of both the posterior descending and posterolateral arteries which was resistant to intracoronary administration of nitroglycerin and verapamil, a finding consistent with thrombotic occlusion. A subsequent angiogram 3 months later showed no residual lesions.

Adult↗
PubMed1996

The effect of exercise on gait patterns in older women: a randomized controlled trial.

BACKGROUND: This study was undertaken to determine (a) whether a program of regular exercise can improve gait patterns in older women, and (b) whether any such improvement in gait is mediated by increased lower limb muscle strength. METHOD: A 22-week randomized controlled trial of exercise was conducted as part of the Randwick Falls and Fractures Study in Sydney, Australia. Subjects were 160 women aged 60-83 years (Mean age 71.1, SD = 5.2) who were randomly recruited from the community. Exercise and control subjects were tested prior to and at the end of the trial. At initial testing, exercisers and controls performed similarly in the strength and gait parameters. They were well matched in terms of age and a number of health and life-style characteristics. RESULTS: At the end of the trial, the exercise subjects showed improved strength in five lower limb muscle groups, increased walking speed, cadence, stride length, and shorter stride times as indicated by both reduced swing and stance duration. There were no significant improvements in any of the strength or gait parameters in the controls. Within the exercise group, increased cadence was associated with improved ankle dorsiflexion strength, and increased stride length was associated with improved hip extension strength. Exercise subjects with initial slow walking speed showed greater changes in velocity, stride length, cadence, and stance duration than those with initial fast walking speed. CONCLUSION: These findings show that exercise can increase gait velocity and related parameters in older persons, and that part of this increase may be mediated by improved lower limb muscle strength.

Aged↗
PubMed1995

Time course of "warm-up" in stable angina.

Warm-up exercise can significantly reduce the severity of myocardial ischemia on exercise after a 10-minute rest, but this benefit is significantly less after a 30-minute rest. Further study is needed to clarify the mechanisms responsible for warm-up. The results of this study are consistent with a change in myocardial metabolism similar to ischemic preconditioning or a delayed increase in myocardial perfusion to the ischemic territory, which has returned toward baseline after 30 minutes.

Aged↗
PubMed1995

Identifying tumor suppressors in genetic mosaics: the Drosophila lats gene encodes a putative protein kinase.

We have identified recessive overproliferation mutations by screening and examining clones of mutant cells in genetic mosaics of the fruitfly Drosophila melanogaster. This type of screen provides a powerful approach for identifying and studying potential tumor suppressors. One of the identified genes, lats, has been cloned and encodes a putative protein kinase that shares high levels of sequence similarity with three proteins in budding yeast and Neurospora that are involved in regulation of the cell cycle and growth. Mutations in lats cause dramatic overproliferation phenotypes and various developmental defects in both mosaic animals and homozygous mutants.

Amino Acid Sequence↗
PubMed1994

Coronary artery ectasia: local pathology or diffuse disease?

It is not known whether general or local factors influence the pathogenesis of coronary ectasia. We analyzed prospectively coronary angiograms from 2,186 consecutive patients with 32 patients (1.5%), identified as having coronary artery ectasia. Sixteen subjects had coronary ectasia in more than one segment of the same or a different artery. In 20 of 72 (28%) ectatic segments there was a proximal, related stenosis. In these cases ectasia was more often saccular than fusiform (16 vs. 4) compared to ectasia without a proximal, related stenosis (21 vs. 31, P = 0.003), and the mean length of the ectatic segment was shorter (8.0 vs. 15.1 mm, P = 0.013). Subjects with ectasia after a stenosis often had other ectatic segments unrelated to stenoses. The high incidence of multisegment involvement suggests that coronary ectasia results from a diffuse abnormality of the vessel wall. In predisposed individuals localized ectasia may follow a stenosis, suggesting poststenotic dilatation.

Constriction, Pathologic↗
PubMed1992

Adjustment for the influence of age and heart rate on Doppler measurements of left ventricular filling.

OBJECTIVE: To determine the normal range of pulsed Doppler measurements of left ventricular filling adjusted for age and heart rate. DESIGN: Multiple regression was used to measure the effects of age and heart rate on pulsed Doppler indices of left ventricular filling in normal subjects. These regression equations were used to calculate a predicted normal value and 95% confidence interval (95% CI) for any subject from his age and heart rate. PARTICIPANTS: 61 subjects with no evidence of cardiovascular disease, aged 20 to 90 years, with a resting heart rate of 47-89 beats/min. RESULTS: The effect of a 10 year increase in age was peak atrial filling velocity +15% (95% CI 12.0% to 18.5%); peak early filling velocity -3.2% (-6.0% to 0%); isovolumic relaxation time +6.2% (3.9% to 8.4%); acceleration time -3.8% (-6.0% to -1.5%); deceleration time +7.9% (5.1% to 10.8%). The effect of a 10 beat/min increase in heart rate was: peak atrial filling velocity +5.5% (1.2% to 10.1%); peak early filling velocity -4.0% (-8.1% to 2.0%); isovolumic relaxation time -2.5% (-4.6% to 0.6%); acceleration time -3.1% (-6.4% to 0.4%); deceleration time -1.8% (-4.0% to 3.8%). CONCLUSION: For any individual, comparison of the predicted normal measurement and 95% CI with the observed measurement allows an assessment of the effects of disease on left ventricular filling that is independent of age and heart rate.

Adult↗
PubMed1991

Prospective, double-blind, placebo-controlled trial of low-dose amiodarone in patients with severe heart failure and asymptomatic frequent ventricular ectopy.

Sudden cardiac death is a common cause of mortality in patients with congestive heart failure. To determine if low-dose amiodarone could reduce sudden death among these patients, a prospective, placebo-controlled, double-blind pilot trial was conducted. One hundred one patients with ejection fractions less than 30%, New York Heart Association class III or IV symptoms, and frequent but asymptomatic spontaneous ventricular ectopy (Lown class II to V) were randomly assigned to treatment with low-dose amiodarone (400 mg/day for 4 weeks and then 200 mg/day) or placebo. Mean follow-up was 357 days (range 4 to 1009 days). Side effects were infrequent and there was no difference in the incidence of side effects between the treatment groups. The frequency of spontaneous ventricular ectopy in the group receiving amiodarone fell from 4992 +/- 1240 beats/24 hours at baseline to 1135 +/- 494 beats/24 hours after 1 month of treatment (p = 0.02) and remained low after 6 months, while there was no change in ventricular ectopy among the patients receiving placebo. Despite the reduction in ectopy, there was no improvement in mortality or decrease in the incidence of sudden death. One-year mortality by Kaplan-Meier analysis was 28% in the group receiving amiodarone and 19% in the group receiving placebo (p = NS). One-year mortality in patients with greater than 75% reduction in ventricular ectopy after 1 month of treatment was 31% versus 17% in patients with less than or equal to 75% ectopic suppression (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Assessment of diastolic filling indexes obtained by radionuclide ventriculography.

This study assesses how differences in residual volume and heart rate influence the measurement and interpretation of commonly used indexes of left ventricular filling obtained by radionuclide ventriculography. Thirty patients with hypertrophic cardiomyopathy (HC) and 26 normal subjects were studied. The time to peak filling rate (168 +/- 42 vs 139 +/- 35 ms; p = 0.006) and time to 30% filling (154 +/- 32 vs 131 +/- 29 ms; p = 0.009 were prolonged in patients with HC compared to normal subjects, suggesting impaired early diastolic filling. However the peak filling rate, measured in end-diastolic counts/s, was greater in patients with HC (3.31 +/- 0.89 vs 3.06 +/- 0.51, p = 0.19). This measurement was influenced by the relative residual volume (HC r = 0.41, p less than 0.001; normal r = 0.29, difference not significant), which was smaller in patients with HC (22.4 +/- 8.0 vs 35.5 +/- 5.6%; p less than 0.0001). The peak filling rate measured in stroke volume counts did not vary with the relative residual volume (HC r = 0.10, difference not significant; normal r = 0.21, difference not significant) and was less than normal in patients with HC (4.27 +/- 0.69 vs 4.72 +/- 1.0; p = 0.58). There was a strong association between the first third filling fraction and the heart rate (HC r = 0.66, p less than 0.001; normal r = 0.71, p less than 0.001), reflecting its dependence on the duration of the first third of diastole.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Good prognosis for dilated cardiomyopathy without severe heart failure or arrhythmia.

In 124 patients with dilated cardiomyopathy, symptoms of heart failure and ventricular arrhythmia at initial assessment were related to outcome a mean of 43 months later. Using life table analysis, the two-year mortality from progressive heart failure was 59 per cent (90 per cent symptoms, six per cent (1-11 per cent) for patients with class 2 symptoms and zero for patients with class 1 symptoms. The two-year mortality from sudden death was 18 per cent (5-32 per cent) for patients with class 3 symptoms, eight per cent (3-14 per cent) for patients with class 2 symptoms and seven per cent (0-17 per cent) for patients with class 1 symptoms. Sudden death was more frequent in patients with ventricular tachycardia or frequent ventricular ectopics, irrespective of the severity of heart failure (15 per cent (7-23 per cent) vs. three per cent (0-8 per cent) at two years). These findings suggest that patients with dilated cardiomyopathy and mild symptoms often have a benign clinical course. However, occult ventricular arrhythmia is associated with an increased risk of sudden death.

Arrhythmias, Cardiac↗
PubMed1989

Enalapril for severe heart failure in infancy.

Eight infants aged between 4 days and 12 weeks with severe heart failure that was refractory to optimal conventional treatment with diuretics were treated with enalapril. The starting dose was 0.1 mg/kg/day, increasing according to response to 0.12-0.43 mg/kg/day. One infant with severe myocarditis did not tolerate enalapril because of hypotension and later died of intractable heart failure. Six of the remaining patients had congenital systemic to pulmonary shunts and one had a simple aortic coarctation. Two weeks after starting enalapril the clinical features of heart failure had improved in all the infants, the mean (SEM) plasma sodium concentration had increased from 129 (2.4) to 136 (1.1) mmol/l and plasma urea concentration had fallen from 7.0 (0.85) to 2.9 (0.85) mmol/l. These data suggest that enalapril is a potentially useful treatment for severe heart failure in infancy.

Dose-Response Relationship, Drug↗