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A H Davies

Publications and source records attributed to A H Davies.

At least 19 recordsLinked to original sources
PubMed2002

Randomised trial of pre-operative colour duplex marking in primary varicose vein surgery: outcome is not improved.

OBJECTIVE: the ability of colour duplex to accurately locate incompetent venous sites has been widely published; its value in pre-operative marking in simple primary varicose vein surgery is evaluated in this study. DESIGN OF STUDY: prospective randomised controlled trial. SETTING: regional vascular service, hospital patients. SUBJECTS: consecutive patients (149) undergoing primary varicose vein surgery where the only difference was one group of patients received duplex marking prior to surgery. Six weeks and 12 months post-operatively all patients had a colour duplex scan to determine the accuracy of surgery and the presence of residual/recurrent varicose veins and completed the Aberdeen, SF-36, and EuroQol quality of life questionnaires. INTERVENTIONS: varicose vein surgery. MAIN OUTCOME MEASURES: Duplex evidence of venous incompetence, quality of life measures using the SF-36 and Aberdeen Varicose Veins Questionnaire. RESULTS: pre-operative marking of primary varicose veins by skilled duplex ultrasonography does not improve the accuracy or recurrence rate following surgery. Quality of life improved significantly following surgery in both groups, however there was no difference in this improvement between the groups. CONCLUSION: the trial has not demonstrated any additional benefit of pre-operative colour duplex marking over that of clinical and hand held Doppler marking in terms of satisfactory varicose vein surgery performance at 6 weeks or 12 months in patients with primary varicose veins of the long saphenous system. It role in the short saphenous system is less clear.

Female↗
PubMed2002

Outcome of ProCol, a bovine mesenteric vein graft, in infrainguinal reconstruction.

OBJECTIVES: historically infrainguinal reconstruction using heterogenous grafts has given poor results due to degradation and aneurysmal dilatation of the graft. A recently introduced heterogenous graft, the ProCol (bovine mesenteric vein) graft, may yield improved results. There are no published reports with respect to ProCol in infrainguinal reconstruction and hence we have reviewed our initial experience with this graft. METHODS: retrospective analysis of six patients in whom infrainguinal reconstruction with ProCol was undertaken between March and August 2001. RESULTS: the primary patency rate was 0% at 3 months, with grafts failing between 4 and 113 days. Two grafts underwent aneurysmal dilatation. CONCLUSION: we are unable to recommend use of the ProCol graft in infrainguinal reconstruction.

Aged↗
PubMed2001

Optimisation and evaluation of an electromagnetic tracking device for high-accuracy three-dimensional ultrasound imaging of the carotid arteries.

Electromagnetic tracking devices provide a flexible, low cost solution for three-dimensional ultrasound (3-D US) imaging. They are, however, susceptible to interference. A commercial device (Ascension pcBIRD) was evaluated to assess the accuracy in locating the scan probe as part of a digital, freehand 3-D US imaging system aimed at vascular applications. The device was optimised by selecting a measurement rate and filter setting that minimised the mean deviation in repeated position and orientation measurements. Experimental evaluation of accuracy indicated that, overall, absolute errors were small: the RMS absolute error was 0.2 mm (range: -0.7 to 0.5 mm) for positional measurements over translations up to 90 mm, and 0.2 degrees (range: -0.8 to 0.9 degrees ) for rotational measurements up to 30 degrees. In the case of position measurements, the absolute errors were influenced by the location of the scanner relative to the scan volume. We conclude that the device tested provides an accuracy sufficient for use within a freehand 3-D US system for carotid artery imaging.

Carotid Arteries↗
PubMed2001

Accuracy of an electromagnetic three-dimensional ultrasound system for carotid artery imaging.

Freehand, three-dimensional (3-D) ultrasound (US) systems, which incorporate an electromagnetic tracking device to register the 3-D spatial location of images acquired using a standard linear array scan-probe, are a flexible and cost-effective solution for many clinical applications. The reconstruction accuracy of one such system was investigated by using a precision-made phantom. The error in 3-D distance measurements, under conditions appropriate to US investigations of the carotid arteries, was found to be -0.45 +/- 1.30 mm, equivalent to -0.53 +/- 3.39% (mean +/- SD). The results are relevant to data acquired using a single sweep scan and for distances in the range 25.00 to 79.06 mm. Both the overall accuracy and precision in point-target location were found to be relatively unaffected by scan depth, and the precision of point-target location was found to be poorest in the elevational direction. In conclusion, the system tested in our laboratory performed with high accuracy, adopting a setup and scan-sweep identical to that used for imaging of the carotid arteries in 3-D.

Calibration↗
PubMed2001

Fibrin monomer and fibrinopeptide B act additively to increase DNA synthesis in smooth muscle cells cultured from human saphenous vein.

PURPOSE: We investigated the hypothesis that fibrinogen increased DNA synthesis (and cell proliferation) of smooth muscle cells (SMCs) cultured from human saphenous vein and that the increased DNA synthesis was attenuated when cells were cultured on polymeric collagen. METHODS: SMCs were cultured from human saphenous vein on plastic, fibronectin, monomeric, and polymeric collagen. Fibrinogen products were prepared by proteolytic digestion. DNA synthesis was measured by bromodeoxyuridine incorporation into DNA, cell proliferation by cell counting, cyclic adenosine monophosphate by enzyme-linked immunosorbent assay, and fibrinopeptide B labeled with iodine 125 used for binding studies. RESULTS: Fibrin monomer (0.003-0.1 micromol/L) stimulated a concentration-dependent increase in DNA synthesis of up to 10-fold, which could be inhibited by the peptide Bbeta15-42. The stimulation of DNA synthesis was highest for cells cultured on plastic and lowest for cells cultured on type I collagen polymer. Much higher concentrations of fibrinogen (0.3-1 micromol/L) were required to effect similar increases in DNA synthesis. Fibrinogen had a particular effect to augment DNA synthesis, up to 14-fold, when cells were cultured on monomeric type I collagen. This augmented DNA synthesis was inhibited by a neutralizing antibody to urokinase-type plasminogen activator. Incubation of cells cultured on collagen monomer with fibrinogen resulted in production of fibrinopeptide B. Fibrinopeptide B (5 micromol/L) increased DNA synthesis by fourfold and had additive effects with fibrin monomer to increase DNA synthesis. Iodinated tyrosine fibrinopeptide B bound to SMCs (dissociation constant 0.6 micromol/L). CONCLUSION: Cultured human saphenous vein SMCs appear to have high-affinity receptors for fibrin monomer and fibrinopeptide B, the engagement of which stimulates DNA synthesis. These mechanisms may be pertinent to the association between fibrinogen and vein graft stenosis in vivo.

Bromodeoxyuridine↗
PubMed2001

Determinants of carotid microembolization.

PURPOSE: Earlier studies have highlighted risk factors for perioperative stroke after carotid endarterectomy, such as female sex, preoperative symptoms, and cerebral infarction. In this study, we investigated the relationship between these factors and perioperative microembolization. METHODS: A total of 235 patients were entered in the study at two centers. Transcranial Doppler ultrasound scanning was possible in 190 patients (81%) and was performed for 1 hour preoperatively and continuously intraoperatively as a means of detecting microemboli and monitoring mean middle cerebral artery velocity. The findings of transcranial Doppler ultrasound scanning were related to perioperative risk factors by means of univariate analysis. RESULTS: Microemboli were detected in 28 (15%), 79 (42%), and 98 (52%) patients preoperatively, during carotid artery dissection, and after closure of the artery, respectively. Having 10 or more emboli after carotid artery closure was more common in women (P = .04) and in patients with symptomatic carotid artery disease (P = .04) and was demonstrated in three of the six patients who had a perioperative stroke. These three patients also had preoperative evidence of cerebral infarction and an intraoperative middle cerebral artery velocity less than 40 cm/s. CONCLUSION: In this study, perioperative microembolization was more common in women and patients with symptomatic carotid artery disease. These findings may explain the increased risk of carotid surgery in these patients.

Adult↗
PubMed2001

Pressure flow study data in a group of asymptomatic male control patients 45 years old or older.

PURPOSE: The role of pressure flow studies in the routine evaluation of patients with benign prostatic hyperplasia remains a controversial issue in urological practice. There are little data on age matched asymptomatic control groups. We evaluated pressure flow findings in such a group. MATERIALS AND METHODS: A total of 24 male patients 47 to 80 years old (mean age 62.5) attending a general surgical clinic were recruited for study after ethical committee approval. The volunteers had never sought medical attention for urinary symptoms and did not perceive themselves as having a urological problem. Volunteers were assessed by International Prostate Symptom Score (I-PSS) and Madsen symptom score, clinical examination, free uroflowmetry, post-void residual ultrasound, repeat pressure flow studies and transrectal ultrasonography. Pressure flow tracings were manually analyzed for standard urodynamic values and the degree of bladder outflow obstruction according to recognized International Continence Society, Abrams-Griffith nomogram, linear passive urethral resistance relation and urethral resistance factor classifications. RESULTS: Median I-PSS was 2.0 (interquartile range 1.2 to 5.7). For I-PSS quality of life the median was 1.0 (interquartile range 0.75 to 2.0). On pressure flow studies 3 patients (13%) had unequivocal obstruction, 7 (29%) were in the equivocal area and 14 (58%) had no obstruction, while 15 (63%) had unstable contractions on medium fill cystometry. CONCLUSIONS: The data show that a surprising number of apparently normal men are obstructed by commonly used criteria. This finding confirms asymptomatic obstruction, suggesting that obstruction may be less important in the development of symptoms than previously thought. Also, until the natural history of obstruction is more clearly defined surgery in obstructed asymptomatic patients is probably unwise.

Aged↗
PubMed2001

Diagnosis and initial management of stroke and transient ischemic attack across UK health regions from 1992 to 1996: experience of a national primary care database.

BACKGROUND AND PURPOSE: The aim of this study was to establish the difference in burden of cerebrovascular disease across the different health regions of the United Kingdom and to determine whether the initial management of new cases of stroke and transient ischemic attack (TIA) was uniform across the United Kingdom: METHODS: The General Practice Research Database (GPRD) is a national database used for epidemiological studies. This was a cohort study identifying incident cases of stroke and TIA over a 5-year study period between 1992 and 1996. The population studied was patients registered with general practitioners contributing to the GPRD across the different health regions of the United Kingdom: Outcome measures were new diagnoses of stroke and TIA, new prescriptions for antiplatelet and anticoagulant agents, and referrals made for specialist opinion. RESULTS: The age-adjusted annual incidence rate across all regions was 151 per 100 000 for stroke and 190 per 100 000 for TIA. There was almost a 2-fold difference in the incidence of cerebrovascular disease between the regions. The management of stroke and TIA in terms of antiplatelet prescription and of referral onward for further opinion to hospital specialists varied significantly between regions. CONCLUSIONS: Reported stroke and TIA incidence on the GPRD was comparable to that of other European studies. There were striking regional differences in the incidence of disease. The primary care management, both in prescription and referral rates, varied significantly between the different regions. There was a marked underuse of antiplatelet and anticoagulant agents, and referral rates for specialists' opinions were low.

Anticoagulants↗
PubMed2000

From genes to proteins: high-throughput expression and purification of the human proteome.

The development of high-throughput methods for gene discovery has paved the way for the design of new strategies for genome-scale protein analysis. Lawrence Livermore National Laboratory and Onyx Pharmaceuticals, Inc., have produced an automatable system for the expression and purification of large numbers of proteins encoded by cDNA clones from the IMAGE (Integrated Molecular Analysis of Genomes and Their Expression) collection. This high-throughput protein expression system has been developed for the analysis of the human proteome, the protein equivalent of the human genome, comprising the translated products of all expressed genes. Functional and structural analysis of novel genes identified by EST (Expressed Sequence Tag) sequencing and the Human Genome Project will be greatly advanced by the application of this high-throughput expression system for protein production. A prototype was designed to demonstrate the feasibility of our approach. Using a PCR-based strategy, 72 unique IMAGE cDNA clones have been used to create an array of recombinant baculoviruses in a 96-well microtiter plate format. Forty-two percent of these cDNAs successfully produced soluble, recombinant protein. All of the steps in this process, from PCR to protein production, were performed in 96-well microtiter plates, and are thus amenable to automation. Each recombinant protein was engineered to incorporate an epitope tag at the amino terminal end to allow for immunoaffinity purification. Proteins expressed from this system are currently being analyzed for functional and biochemical properties.

Cloning, Molecular↗
PubMed2000

The association of platelet-derived growth factor receptor expression, plaque morphology and histological features with symptoms in carotid atherosclerosis.

Platelet-derived growth factor may influence smooth muscle cell migration and proliferation and, therefore, carotid plaque composition and stenosis. Platelet-derived growth factor receptor expression and histological features were compared in carotid plaques from symptomatic and asymptomatic patients. Immunocytochemistry and histology determined platelet-derived growth factor-alpha and -beta receptor expression, white blood cell infiltration, smooth muscle cell, elastin, cholesterol, collagen and intraplaque haemorrhage in carotid artery plaques removed at surgery or the post-mortem. Plaques with > 70% stenosis from asymptomatic (n = 10) and symptomatic patients (n = 27) had higher expression of platelet-derived growth factor and beta receptors and higher scores for macrophages and intraplaque haemorrhage than plaques with < 70% stenosis from asymptomatic patients (n = 33). Plaques with > 70% stenosis from symptomatic patients had significantly lower alpha receptor expression than plaques with > 70% stenosis from asymptomatic patients. The reduction of alpha receptor expression, which may inhibit smooth muscle cell migration, suggests that differential expression of platelet-derived growth factor receptor subunits in plaques may be related to symptoms.

Aged↗
PubMed2000

Exercise therapy or angioplasty? A summation analysis.

OBJECTIVES: To compare the outcome of exercise therapy or angioplasty for the treatment of patients with intermittent claudication. DESIGN: A summation analysis. METHODS: A search using MEDLINE and PUBMED between 1966 and April 1999 followed by a review of the manuscripts yielded 54 studies involving angioplasty and 27 studies involving exercise therapy for intermittent claudication. Studies were only included (12 angioplasty and nine exercise series) when results were available for patients with intermittent claudication alone, and when outcome was assessed in terms of symptoms at a minimum of 6 months. RESULTS: The total number of claudicants undergoing exercise therapy was 294 patients, with a mean symptomatic success rate of 38. 4% and a mean improvement in maximum walking distance of 189.7% at 6 months. The total number of claudicants undergoing angioplasty was 2071, with a mean overall symptomatic success rate of 76.6%. The mean overall complication rate was 9% and mean major complication rate was 2.7% for the angioplasty studies. CONCLUSION: Although the result demonstrates an advantage of angioplasty over exercise therapy at 6 months, there is a small risk of major complications. However, comparison of studies was impaired due to disparity in patient numbers, limited follow-up time and lack of uniformity in outcome assessment. In order to achieve a valid comparison of these therapies in a future randomised study, a validated disease-specific instrument for the assessment of symptomatic outcome for claudicants is required.

Angioplasty, Balloon↗
PubMed2000

Measuring the quality of life in patients with venous ulcers.

PURPOSE: This prospective study aimed to validate a newly designed specific measure of quality of life for patients with venous ulcers. METHODS: The study was set in a London teaching hospital and surrounding community clinics. Items for the questionnaire were selected by means of patient interviews, a literature review, and expert opinion. The questionnaire and the Short Form 36-item (SF-36) Health Survey were given to a prospective consecutive cohort of 98 patients with proven venous ulcers that were diagnosed by means of clinical and color duplex examination. Fifty-eight of the patients were women (60%), and the median age of patients was 76 years. The questionnaire was assessed for reliability, validity, and responsiveness. RESULTS: The ulcer-specific questionnaire showed good reliability, as assessed by means of the internal consistency (Cronbach alpha = 0.93) and test-retest analysis (r = 0.84). Factor analysis identified four important health factors: social function, domestic activities, cosmesis, and emotional status. Validity was demonstrated by means of a high correlation with all eight domains of the SF-36 general health measure (r > 0.55, P <.001). Responsiveness was demonstrated by means of a significant reduction in the score on the ulcer questionnaire as ulcers healed at 6 and 11 weeks (P <.05). CONCLUSION: Good evidence exists that a clinically derived measure for patients with venous ulcers has validity to measure the quality of life.

Activities of Daily Living↗
PubMed2000

Chlamydia pneumoniae does not influence atherosclerotic plaque behavior in patients with established carotid artery stenosis.

BACKGROUND AND PURPOSE: Research for infectious agents in the etiology of atherosclerosis has identified Chlamydia pneumoniae as a possible candidate. While there is evidence of an association between presence of this microorganism and atherosclerosis, it is unclear whether infection has a genuinely etiologic role in this disease, whether its presence influences clinical outcomes, and, if so, at which stages of disease this occurs. We have approached this issue in patients with advanced carotid artery atherosclerosis using molecular biological detection methods and clinically relevant indicators of pathology in carotid artery atheroma to determine whether the presence of C pneumoniae correlates with plaque instability. METHODS: C pneumoniae was detected with the use of a sensitive nested polymerase chain reaction. Preoperative embolization and preoperative infarcts were recorded with the use of transcranial Doppler insonation of the middle cerebral artery and cerebral CT, respectively. RESULTS: C pneumoniae DNA was detected in 25.5% of a cohort of 98 symptomatic patients. There was no significant difference in plaque stability as measured by embolization rates between the chlamydial-positive and -negative specimens. There was also no correlation between the number of ipsilateral hemispheric infarcts in the territory of the middle cerebral artery and chlamydial status. CONCLUSIONS: This study confirms that C pneumoniae is a common finding in atherosclerotic plaques of the carotid artery but suggests that the presence of the infectious organism has little detectable impact on plaque instability when measured by clinically significant markers. This raises important questions for the rationale of antibiotic therapy in atherosclerosis.

Aged↗
PubMed2000

The symptomatic carotid plaque.

BACKGROUND: The natural histories of equally severe symptomatic and asymptomatic carotid stenoses are very different, which suggests dichotomy in plaque behavior. The vascular biology of the symptomatic carotid plaque is presented in this review. SUMMARY OF REVIEW: Histology studies comparing asymptomatic and symptomatic plaques were identified from MEDLINE. Reports in which stenosis severity was not stated or not similar for symptomatic and asymptomatic patients were excluded. In vitro studies and reports from the coronary circulation were reviewed with regard to the vascular biology of the plaque. Histology studies comparing carotid plaques removed from symptomatic and asymptomatic patients reveal characteristic features of unstable plaques: surface ulceration and plaque rupture (48% of symptomatic compared with 31% of asymptomatic, P<0.001), thinning of the fibrous cap, and infiltration of the cap by greater numbers of macrophages and T cells. In vitro studies suggest that macrophages and T cells release cytokines and proteinase, which stimulate breakdown of cap collagen and smooth muscle cell apoptosis and thereby promote plaque rupture. CONCLUSIONS: Infiltration of inflammatory cells to the surface of carotid plaques may be a critical step in promoting plaque rupture and resultant embolization or carotid occlusion. Further understanding of cell recruitment and behavior in carotid atherosclerosis may allow better detection of unstable plaques and therapeutic methods of plaque stabilization.

Carotid Arteries↗
PubMed2000

Systematic comparison of the early outcome of angioplasty and endarterectomy for symptomatic carotid artery disease.

BACKGROUND AND PURPOSE: Endoluminal treatment is being increasingly used for carotid artery disease. The aim of this study was to compare the stroke and death risk within 30 days of endovascular treatment or endarterectomy for symptomatic carotid artery disease. METHODS: systematic comparison of the 30-day outcome of angioplasty with or without stenting and endarterectomy for symptomatic carotid artery disease reported in single-center studies, published since 1990, was performed. RESULTS: Thirty-three studies (13 angioplasty and 20 carotid endarterectomy) were included in this analysis. Carotid stents were deployed in 44% of angioplasty patients. Mortality within 30 days of angioplasty was 0.8% compared with 1.2% after endarterectomy (OR 0.68, 95% CI 0.43 to 1.05; P=0.6). The stroke rate was 7.1% for angioplasty and 3.3% for endarterectomy (OR 2.22, CI 1.62 to 3.04; P<0.001), while the risk of fatal or disabling stroke was 3.2% and 1.6%, respectively (OR 2.09, CI 1.3 to 3.33; P<0.01). The risk of stroke or death was 7.8% for angioplasty and 4% for endarterectomy (OR 2.02, CI 1.49 to 2.75; P<0.001), while disabling stroke or death was 3.9% after angioplasty and 2.2% after endarterectomy (OR 1.86, CI 1.22 to 2.84; P<0.01). CONCLUSIONS: In the treatment of symptomatic carotid artery disease, the risk of stroke is significantly greater with angioplasty than carotid endarterectomy. At present, carotid angioplasty is not recommended for the majority of patients with symptomatic carotid artery disease.

Angioplasty, Balloon↗