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Biomedical subjects

R M Greenhalgh

Publications and source records attributed to R M Greenhalgh.

At least 91 records · Page 5Linked to original sources
PubMed1993

Prevalence of intermittent claudication and risk factors for its development in patients on renal replacement therapy.

The prevalence of symptomatic intermittent claudication (IC) was assessed using a standard cardiovascular questionnaire in a cohort of 325 patients on renal replacement therapy (RRT). IC was found in 19% of patients, 77% of whom were smokers and 22% diabetic. It was more common in men than women and in smokers than non-smokers (p < 0.001). Those with IC were significantly older (61 years vs. 50 years p < 0.001), smoked more (23 pack years vs. 12 pack years p = 0.002), had higher median systolic blood pressures (143 mmHg vs. 140 mmHg p = 0.041) and median triglyceride levels (2.07 mmol/l vs. 1.60 mmol/l p = 0.023) than those renal patients without IC. A case control study matching for age, sex and treatment revealed patients with IC to have higher median systolic blood pressure (147 mmHg vs. 140 mmHg p = 0.031), cholesterol (6.70 mmol/l vs. 5.90 mmol/l p = 0.029), LDL cholesterol (4.64 mmol/l vs. 3.86 mmol/l p = 0.011), and contained a greater proportion of smokers (78% vs. 50% p < 0.001). IC is common in patients on RRT. Whilst smoking was prevalent among those with IC it was much less frequent than in the general population with IC. Other factors such as hypertension, lipid abnormalities or the uraemic state itself may also be important in the development of IC in these patients.

Adult↗
PubMed1993

The influence of smoking and lipids on restenosis after carotid endarterectomy.

Factors associated with restenosis were investigated in 107 patients undergoing carotid endarterectomy for symptomatic disease. The patients, 71 men and 36 women with mean age 68 +/- 8 years, were followed up for 1 year by serial Duplex scanning. Carotid restenosis of > or = 50% developed in 18 patients (17%), 11 men and seven women. Restenosis was not influenced by age, sex, diabetes or hypertension. Continuing smokers, serum cotinine > 200 nmol/l, had a significantly higher incidence of > or = 50% restenosis after 1 year (39%), compared with only 16% of non-smokers, p = 0.023. Restenosis > or = 50% also was associated significantly with below median body mass index (p = 0.027). Women undergoing carotid endarterectomy had higher levels of cholesterol (median 7.4 mmol/l) and apolipoprotein B (median 0.81 g/l) than men (median cholesterol 6.4 mmol/l, median apolipoprotein B 0.69 g/l), p < 0.01. For men only, restenosis of > or = 50% was associated with low levels of serum cholesterol (median 5.7 mmol/l), p = 0.002. For women cholesterol levels were higher (median 8.1 mmol/l) in those with > or = 50% restenosis. Smoking adversely influences early restenosis (1 year) after carotid endarterectomy. Hyperlipidaemia is not a risk factor for restenosis in men, but may be associated with restenosis in women.

Adult↗
PubMed1993

Urgent carotid surgery for high risk patients.

Carotid surgery was performed urgently on 22 occasions out of 300 (7%). Of 15 patients with progressing stroke, in all, progression of stroke was arrested. Six patients recovered virtually completely and eight had improving neurological deficit after surgery, i.e. 14 of 15 (93%) benefitted. The other patient had arrest of stroke for a week and then suffered ipsilateral stroke. Of the seven patients operated upon for crescendo transient ischaemic attacks, five had no deficit after surgery or further attacks. The sixth patient had no further attacks but was found to have a tiny, neurological deficit. In these six patients (87%), surgery was greatly beneficial. The remaining patient had a fatal stroke following operation.

Acute Disease↗
PubMed1993

Risk factors for atherosclerosis in men with stenosing or aneurysmal disease of the abdominal aorta.

Risk factors associated with atherosclerosis were compared in 2 groups of men: with aneurysmal dilatation (AAA) or stenosing disease (SAD) of the infrarenal aorta. In the AAA group (N = 114) the median aortic diameter was 6.9 cm and 89% of patients had undergone elective or emergency surgical repair. In the SAD group (N = 57) an equal proportion had had an aortobifemoral bypass, the median aortic diameter was 1.8 cm. Men with AAA were older (73 years vs 68 years; p < 0.001). There were no differences in total cholesterol and triglycerides between the two but men with AAA had a higher HDL-cholesterol concentration (1.22 mmol/l vs 1.08 mmol/l; p = 0.019). Tobacco consumption in the 2 groups was similar (36.5 pack years vs 35.0 pack years; p = 0.387). After correction for age, diastolic blood pressure was significantly higher in the AAA group. In both groups there is extensive aortic atherosclerosis but differences between the two groups indicate that stenosing and dilating disease are distinct pathological entities.

Age Factors↗
PubMed1992

Community clinics for leg ulcers and impact on healing.

OBJECTIVE: To evaluate the effectiveness of community clinics for leg ulcers. DESIGN: All patients with leg ulceration were invited to community clinics that offered treatment developed in a hospital research clinic. Patients without serious arterial disease (Doppler ankle/brachial index > 0.8) were treated with a high compression bandage of four layers. SETTING: Six community clinics held in health centres in Riverside District Health Authority supported by the Charing Cross vascular surgical service. PATIENTS: All patients referred to the community services with leg ulceration, irrespective of cause and duration of ulceration. MAIN OUTCOME MEASURES: Time to complete healing by the life table method. RESULTS: 550 ulcerated legs were seen in 475 patients of mean (SD) age 73.8 (11.9) years. There were 477 venous ulcers of median size 4.2 cm2 (range 0.1-117 cm2), 128 being larger than 10 cm2. These ulcers had been present for a median of three months (range one week to 63 years) with 150 present for over one year. Four layer bandaging in the community clinics achieved complete healing in 318 (69%) venous ulcers by 12 weeks and 375 (83%) by 24 weeks. There were 56 patients with an ankle/brachial arterial pressure index < 0.8, indicating arterial disease. The 50 patients with pressure index < 0.8 > 0.5 were treated with reduced compression, and 24 (56%) healed by 12 weeks and 31 (75%) by 24 weeks. The figures for overall healing for all leg ulcers were 351/550 (67%) at 12 weeks and 417/550 (81%) at 24 weeks, compared with only 11/51 (22%) at 12 weeks before the community clinics were set up. CONCLUSIONS: Community clinics for venous ulcers offer an effective means of achieving healing in most patients with leg ulcers.

Aged↗
PubMed1992

Selection for screening for familial aortic aneurysms.

The reported familial clustering of abdominal aortic aneurysm (AAA) indicates the possible rewards of family-based screening programmes with respect both to the number of asymptomatic aneurysms detected and to identifying associated genes. Ultrasonographic screening of 28 families (25 brothers and 28 sisters) was carried out together with collecting a history and a blood sample for analysis of the cholesterol level and genetic markers. Among the screened siblings six (11 per cent), all > 60 years old, had an AAA > or = 3.0 cm in diameter. A further 11 siblings (21 per cent), six of whom were < 60 years old, had a wide (2.5-2.9 cm) aorta. The presence of an aneurysmal or wide aorta was significantly associated with smoking (P = 0.027), male sex (P = 0.008) and a proband age of < 60 years (P = 0.031). Polymorphic genetic markers for type III collagen and haptoglobin were not informative in these families. These results indicate that the efficiency of screening siblings of patients with AAA could be improved by limiting it to brothers with a smoking history and/or siblings of younger patients. The familial component appears to be greatest in these younger patients.

Adult↗
PubMed1992

Colour-coded duplex ultrasonography in the selection of patients for endovascular surgery.

Endovascular surgery using angioplasty or atherectomy may potentially relieve the symptoms of claudicants with minimal morbidity, but results are best when short stenoses are treated. In this study, colour-coded duplex ultrasonography has been compared with angiography. In aortoiliac segments duplex examination had a sensitivity of 88 per cent and a specificity of 100 per cent; in femoropopliteal disease the sensitivity was 100 per cent and duplex scanning identified more disease than angiography. Subsequently, 73 symptomatic limbs with femoropopliteal disease were scanned to assess their suitability for endovascular surgery. Of these limbs, 27 (37 per cent) had suitable lesions and the remaining 46 (63 per cent) were spared angiography. Colour-coded duplex ultrasonography can reliably be used to select patients for endovascular surgery.

Aorta, Abdominal↗
PubMed1992

Mechanical properties of the aneurysmal aorta.

The mechanical properties of the abdominal aorta were investigated non-invasively in 30 patients with aortic aneurysm and 11 with peripheral arterial disease. The distensibility of the aorta was measured using M-mode ultrasonography, permitting non-invasive assessment of the pressure--strain elastic modulus or aortic stiffness, Ep. The median Ep value increased from 4.0 N/cm2 in control subjects in their third decade of life (n = 10) to 10.4 N/cm2 in middle age (n = 11) to 14.0 N/cm2 in the elderly (n = 13). In the presence of a normal diameter, peripheral arterial disease with aortic atherosclerosis had little effect on aortic stiffness, median Ep being 16.0 N/cm2. Aneurysmal dilatation was associated with a significant increase in aortic stiffness, median Ep being 31.3 N/cm2 (P < 0.001). For aortas of normal diameter, Ep was at all ages dependent on mean arterial pressure. In patients with aortic aneurysms there was no clear relationship between Ep and mean arterial pressure or aortic diameter. Of the patients studied, 15 underwent aortic reconstruction; increasing aortic stiffness (log Ep) was associated with a decreased medial elastin content of the aortic biopsy (r = -0.63, P < 0.02). This study demonstrates the marked stiffness or inelasticity of dilated or aneurysmal vessels, part of which is attributable to the loss of elastin.

Adult↗
PubMed1992

Prevalence, progression and natural history of asymptomatic carotid stenosis: is there a place for carotid endarterectomy?

The purpose of this study was to determine the prevalence, progression and prognosis of asymptomatic carotid artery stenosis in a population of 1198 patients with peripheral arterial disease (n = 986) or aortic aneurysm (n = 212), mean age 67.7 (S.D. = 10.0) years. Patients were recruited from 1985 to 1989 with annual assessment of carotid artery stenosis of over 50% using Doppler peak frequency analysis. Patients were followed up annually until 1990 or their first event, transient ischaemic attack (TIA), amaurosis fugax (AFx), stroke without antecedent TIA, or death (mean follow up 20 months). Life tables were used to determine risk of events in different patient groups. Only 164 (13.7%) patients had a stenosis of over 50% in either of the common or internal carotid arteries, disease was bilateral in 33 (2.8%) patients. A total of 33 patients (2.8%) had over 80% stenosis in common or internal carotid arteries. During follow up 37 (3.1%) patients developed a stenosis greater than 50%. Only 27 (2.3%) patients developed a stroke, 11 of which were fatal. A further 33 (2.8%) suffered a TIA or AFx and a total of 155 patients died during follow up. The total neurological event rate (TIA, AFx and stroke) was significantly associated with the presence of over 50% stenosis, [relative risk (RR) = 2.98, 95% confidence interval (95% C.I.) 1.68-5.29, p less than 0.001] and carotid bruit (RR = 1.16, 95% C.I. 1.23-3.81, p = 0.010). Although risk of stroke was higher in patients with a 50% stenosis, this failed to achieve statistical significance (RR = 1.78, 95% C.I. 0.66-4.80, p = 0.275).(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Aneurysm↗
PubMed1992

The reproducibility of colour-coded duplex scanning in measuring arterial wall dimensions.

Intimal hyperplasia continues to be a major problem following vascular surgery but experimental evidence suggests that it can be reduced pharmacologically. For clinical studies an accurate, reproducible and non-invasive image of the intima and lumen is required. We have assessed the value of the Acuson 128 Colour Duplex for such studies. Ten patients had their common femoral arteries scanned at a fixed point by two experienced observers on two separate occasions. External vessel diameter, luminal diameter and internal diameter (i.e. the diameter within the internal elastic lamina) were measured in both longitudinal and cross-sectional views. Cross-sectional area and degree of stenosis were all measured and all parameters expressed as limits of agreement. The mean external diameter of the common femoral arteries was 10.5 +/- 1.6 mm. Measurements in the longitudinal view were highly reproducible with limits of agreement ranging from -0.67 - +0.25 mm (internal diameter) to -1.49 - +1.31 mm (luminal diameter). In order to detect a meaningful change in longitudinal external diameter a real difference of 0.86 mm is required representing a change of less than 10%. Cross-sectional diameter measurements were similarly reproducible (-0.73 - +0.47 mm to -1.97 - +1.79 mm). However, cross-sectional area measurements had a wide variation so that the error in degree of stenosis was -25.4 - +30.2%. Thus, duplex ultrasound reproducibly images the layers of the arterial wall. Prospective studies of intimal hyperplasia are feasible but must be based on longitudinal and cross-sectional diameters rather than cross-sectional areas.

Aged↗
PubMed1991

Limitations of ultrasonography in surveillance of small abdominal aortic aneurysms.

The repeatability, observer bias and instrument bias of aortic diameter measurement by ultrasonography, were investigated in ten patients with small (3-6 cm by computed tomography) infrarenal abdominal aortic aneurysm. The repeatability of maximum aortic diameter measurement by ultrasonography was much better for anterior-posterior than transverse diameter, with coefficients of repeatability 3.0-7.5 mm and 10-15 mm respectively. The repeatability of suprarenal aortic diameter measurement was poor. Surprisingly, maximum diameter using ultrasonography was larger than that using computed tomography, the difference being least for anterior-posterior measurements. At best a single, experienced observer, using the same instrument may provide aortic diameters using ultrasonography accurate to within 5 mm, but more commonly such aortic diameter is only accurate to within 8 mm.

Aorta, Abdominal↗
PubMed1991

Influence of apolipoproteins on the anatomical distribution of arterial disease.

The association of raised triglyceride levels with peripheral arterial disease has indicated that different interactions of environmental, biochemical and genetic risk factors promote atherosclerosis in particular sites. This hypothesis was investigated in patients presenting with atherosclerotic disease in the carotid (n = 23) or peripheral arteries (n = 94) before the age of 50 years; symptomatic coronary artery disease was also present in some patients (n = 35). Patients presenting with carotid disease had the highest levels of cholesterol (mean 7.6 mmol/l, P less than 0.05), apolipoproteins B (mean 1.02 g/l) and CIII (median 22.8 mg/dl, P less than 0.05) but normal levels of apolipoprotein AI. Patients presenting with peripheral arterial disease were the heaviest smokers and this was the only group where hypertriglyceridaemia was observed. Patients with coronary artery disease had the lowest levels of apolipoprotein AI (mean 1.15 g/l, P less than 0.05). Although polymorphic variation in the apolipoprotein genes did not appear to influence the distribution of symptomatic disease, genetic variation at two polymorphic sites in the apolipoprotein AI-CIII-AIV gene cluster was associated with differences in triglyceride levels. The control of the metabolism of triglyceride rich particles by apolipoproteins may predispose to atherosclerosis in specific sites, low levels of apolipoprotein AI selectively promoting coronary artery atherosclerosis and high levels of apolipoprotein CIII selectively promoting carotid artery atherosclerosis.

Adult↗
PubMed1991

PTFE or HUV for femoro-popliteal bypass: a multi-centre trial.

Despite wide clinical experience the choice between human umbilical vein (HUV) or polytetrafluoroethylene (PTFE) when the saphenous vein is inadequate remains unclear. In a multi-centre trial of 801 femoro-popliteal bypasses, autogenous vein could not be used in 252 (31%), of which 191 were randomised to either HUV or PTFE and started on aspirin 300 mg plus dipyridamole 150 mg (ASA + DPM) twice daily. Graft patency measured objectively by independent trial coordinators was expressed on an "intention to treat" basis by life table and analysed statistically by log rank and confidence intervals (95% CI). Overall, 101 grafts failed and cumulative patency was 53% (45-61%) at 3 years compared with 60% (55-65%) in 549 vein grafts. Prosthetic bypass patency above knee was 65% (55-75%); markedly better than 35% (23-47%) below knee (p less than 0.001) and comparable with 62% (55-69%) in 217 above knee saphenous vein grafts. Most failures occurred early at a rate of 52/1000 patient-months in the first 3 months (43/1000 for vein) falling to 21/1000 by 6 to 12 months and around 10/1000 subsequently. Randomisation produced comparable groups of 87 HUV and 104 PTFE grafts. Cumulative primary patency for HUV was 68, 63 and 57% at 1, 2 and 3 years, respectively compared with 61, 56 and 48% for PTFE with wide confidence intervals for the difference at 3 years (-20 to 38%, p = 0.27).(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗
PubMed1991

Genetic variants of collagen III and abdominal aortic aneurysm.

Collagens provide the tensile strength of the aortic wall. Variations in collagen structure are recognised in Ehlers Danlos syndrome type IV and could also be associated with a predisposition to aortic aneurysm. The frequency of some minor genetic variants of type III collagen, present in the normal population, can be detected by restriction enzyme digestion of genomic DNA from peripheral leucocytes. The frequency of a minor collagen type III allele demonstrated with the restriction enzyme Ava II was compared in patients with abdominal aortic aneurysm (n = 70) and aortoiliac stenosis (n = 47). The frequency of the minor allele was significantly higher in aneurysm patients (0.30) compared with patients with aortoiliac stenosis (0.17), p less than 0.05. The presence of the minor allele was associated with a less elastic aneurysm wall (median pressure strain elastic modulus 4575, n = 7), compared with patients homozygous for the common allele (median pressure strain elastic modulus 1990, n = 6), p less than 0.05. These results indicate that genetic variants of type III collagen may influence the extensile properties of the aortic wall and that mutations in the type III collagen gene may be associated with aortic aneurysms.

Aged↗