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Biomedical subjects

A R Naylor

Publications and source records attributed to A R Naylor.

At least 73 records · Page 4Linked to original sources
PubMed2000

Increased matrix metalloproteinase-9 activity in unstable carotid plaques. A potential role in acute plaque disruption.

BACKGROUND AND PURPOSE: Acute disruption of atherosclerotic plaques precedes the onset of clinical syndromes, and studies have implicated a role for matrix metalloproteinases (MMPs) in this process. The aim of this study was to establish the character, level, and expression of MMPs in carotid plaques and to correlate this with clinical status, cerebral embolization, and histology. METHODS: Plaques were obtained from 75 consecutive patients undergoing carotid endarterectomy and divided into 4 groups according to symptomatology (group 1, asymptomatic; group 2, symptomatic >6 months before surgery; group 3, symptomatic within 1 to 6 months; group 4, symptomatic within 1 month). All patients underwent preoperative and intraoperative transcranial Doppler monitoring. Plaques were subjected to histological examination and quantification of MMPs by zymography and ELISA. RESULTS: The level of MMP-9 was significantly higher in group 4 (median 125.7 ng/mL for group 4, median <32 ng/mL for all other groups; P=0.003), with no difference in the levels of MMPs 1, 2, or 3. Furthermore, the MMP-9 concentration was significantly higher in plaques undergoing spontaneous embolization (P=0.019) and those with histological evidence of plaque instability (P<0.03). In situ hybridization demonstrated increased MMP-9 expression in highly symptomatic plaques in areas of intense inflammatory infiltrate. CONCLUSIONS: The concentration, production, and expression of MMP-9 is significantly higher in unstable carotid plaques. If this proves to be a causal relationship, MMP-9 may be a strong candidate for pharmacotherapy aimed at stabilizing plaques and preventing stroke.

Aged↗
PubMed2000

Making carotid surgery safer.

Carotid surgery has been shown to be beneficial in level one randomised trials. However, evidence suggests that current outcomes do not match those published in 1991. In order to make carotid endarterectomy safer in the future, it is essential to optimise patient selection and risk factor management and to maintain an obsessional approach to surgical technique. A planned strategy of monitoring and quality control assessment can also contribute towards a sustained reduction in the peri-operative risk.

Endarterectomy, Carotid↗
PubMed1999

Angiogenesis and the atherosclerotic carotid plaque: an association between symptomatology and plaque morphology.

PURPOSE: Symptomatic carotid disease resulting from generation of thromboemboli has been associated with plaque instability and intraplaque hemorrhage. These features of the lesion could be influenced by the fragility and position of neovessels within the plaque. The purpose of this study was to determine whether any association exists between neovessel density, position, morphology, and thromboembolic sequelae. METHODS: Carotid endarterectomy samples were collected from 15 asymptomatic patients with greater than 80% stenoses and from 13 highly symptomatic patients who had suffered ipsilateral carotid stenotic events within 1 month of surgery. Both groups were matched for gender, age, risk factors, degree of carotid artery stenosis, and plaque size. Samples were stained with hematoxylin/eosin and van Geison. Immunohistochemistry was performed by using an endothelial specific antibody to CD31. Plaques were assessed for histologic characteristics, and neovessels were counted and characterized by size, site, and shape. RESULTS: There were significantly more neovessels in plaques (P <.00001) and fibrous caps (P <.0001) in symptomatic compared with asymptomatic plaques. Neovessels in symptomatic plaques were larger (P <.004) and more irregular. There was a significant increase in plaque necrosis and rupture in symptomatic plaques. Plaque hemorrhage and rupture were associated with more neovessels within the plaque (P <.017, P <.001) and within the fibrous cap (P <.046, P <.004). Patients with preoperative and intraoperative embolization had significantly more plaque and fibrous cap neovessels (P <.025, P <.001). CONCLUSION: Symptomatic carotid disease is associated with increased neovascularization within the atherosclerotic plaque and fibrous cap. These vessels are larger and more irregular and may contribute to plaque instability and the onset of thromboembolic sequelae.

Arteriosclerosis↗
PubMed1999

In situ replacement of infected aortic grafts with rifampicin-bonded prostheses: the Leicester experience (1992 to 1998)

PURPOSE: Prosthetic graft infection after aortic aneurysm surgery is a life-threatening complication. Treatment options include total graft excision and extra-anatomic bypass grafting or in situ replacement of the graft. The latter option is gaining increasing popularity, but the long-term outcome remains uncertain, particularly in light of the increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA). We performed a prospective nonrandomized study to assess the outcome after graft excision and in situ replacement with a rifampicin-bonded prosthesis for the treatment of major aortic graft infection. METHODS: In a 6-year period from January 1992 to December 1997, 11 patients (eight men, three women) with major aortic graft infection underwent total graft excision and in situ replacement with a rifampicin-bonded prosthesis. The median age of the patients was 66 years (range, 49 to 78 years). Four patients had a hemorrhage from an aortoenteric fistula, three had a retroperitoneal abscess, two had graft occlusion, one had a perigraft collection shown by means of computed tomography, and one had a ruptured suprarenal false aneurysm. Organisms were cultured from 10 patients. RESULTS: MRSA was isolated in two patients, both of whom had originally undergone repair of a ruptured abdominal aortic aneurysm. Two patients died (18.2%) within 30 days, and three patients (27.6%) had nonfatal complications (peritoneal candidiasis, transient renal impairment, and profound anorexia). Two patients died late in the follow-up period. Seven patients remain alive and clinically free of infection. CONCLUSION: The long-term results after total graft excision and in situ replacement with a rifampicin-bonded prosthesis appear to be favorable. However, MRSA aortic graft infection appears to be associated with a poor prognosis.

Aged↗
PubMed1999

Prevalence of true vein graft aneurysms: implications for aneurysm pathogenesis.

BACKGROUND: Circumstantial evidence suggests that arterial aneurysms have a different cause than atherosclerosis and may form part of a generalized dilating diathesis. The aim of this study was to compare the rates of spontaneous aneurysm formation in vein grafts performed either for popliteal aneurysms or for occlusive disease. The hypothesis was that if arterial aneurysms form a part of a systemic process, then the rates of vein graft aneurysms should be higher for patients with popliteal aneurysms than for patients with lower limb ischemia caused by atherosclerosis. METHODS: Infrainguinal vein grafting procedures performed from 1990 to 1995 were entered into a prospective audit and graft surveillance program. Aneurysmal change was defined as a focal increase in the graft diameter of 1.5 cm or greater, excluding false aneurysms and dilatations after graft angioplasty. RESULTS: During the study period, 221 grafting procedures were performed in 200 patients with occlusive disease and 24 grafting procedures were performed in 21 patients with popliteal aneurysms. Graft surveillance revealed spontaneous aneurysm formation in 10 of the 24 bypass grafts (42%) for popliteal aneurysms but in only 4 of the 221 grafting procedures (2%) that were performed for chronic lower limb ischemia. CONCLUSION: This study provides further evidence that aneurysmal disease is a systemic process, and this finding has clinical implications for the treatment of popliteal aneurysms.

Adult↗
PubMed1999

Cerebral perfusion monitored using transcranial Doppler during acute anaphylaxis.

We present a case of severe acute anaphylaxis that occurred during preparation of a patient for carotid endarterectomy. Intra-arterial blood pressure and transcranial Doppler monitoring had been established before the anaphylactic reaction began and therefore the changes in arterial blood pressure and middle cerebral artery blood-flow velocity could be observed as they happened. This made it possible to assess directly the effectiveness of our management, which followed the resuscitation guidelines issued by the Association of Anaesthetists. In particular, this was a rare opportunity to confirm whether the recommended management is effective in restoring cerebral blood flow, and not just blood pressure, in a 'real life' situation, as most resuscitation information is based on laboratory-based animal studies. Evidence is presented which suggests that the administration of adrenaline in this setting is associated with increases in cerebral blood flow that are independent of arterial blood pressure.

Aged↗
PubMed1999

Colour-coded duplex imaging and dependent Doppler ultrasonography in the assessment of cruropedal vessels.

BACKGROUND: It has been suggested that ultrasonography could replace diagnostic arteriography in the assessment of patients who present with leg ischaemia. This study investigated a group of consecutive patients who had femorodistal bypass and who were assessed before operation with colour-coded duplex and dependent Doppler insonation alone. METHODS: Thirty-seven consecutive patients with critical lower limb ischaemia underwent surgical exploration with a view to femorodistal bypass. Results of preoperative colour-coded duplex and dependent Doppler insonation were compared with intraoperative arteriograms and surgical findings. RESULTS: There was very good agreement between colour-coded duplex imaging and dependent Doppler insonation with intraoperative angiography and surgical findings in the prediction of the optimal run-off vessel (kappa = 1.0) and the site of the distal anastomosis (kappa = 0.85; 95 per cent confidence interval 0.71-1.0). There was also very good agreement between dependent Doppler insonation and intraoperative arteriography (kappa = 1.0) in predicting pedal arch patency and the predominant feeding vessel. CONCLUSION: Assessment of leg arteries before femorodistal bypass can be performed accurately with non-invasive colour-coded duplex imaging and dependent Doppler insonation alone, thus obviating the need for preoperative arteriography.

Adult↗
PubMed1999

Role of superficial venous surgery in the treatment of venous ulceration.

BACKGROUND: The aim of this study was to determine the ability of superficial venous surgery to heal venous ulcers in lower legs with isolated superficial venous incompetence. METHODS: This was a prospective study of patients recruited from a venous ulcer assessment clinic. Ulcers were considered venous if the ankle : brachial pressure index was greater than 0.8 and duplex imaging showed venous reflux. Patients with isolated superficial venous incompetence were offered saphenofemoral and/or saphenopopliteal surgery. Neither perforator surgery, skin grafting nor postoperative compression hosiery or bandaging was used. RESULTS: A total of 122 legs with normal deep veins underwent superficial venous surgery. Ninety procedures (74 per cent) were done under local and 32 (26 per cent) under general anaesthesia. Sixty operations (49 per cent) were done as a day case. The median time to healing was 18 (95 per cent confidence interval 14-21) weeks and the cumulative 6-, 12- and 18-month healing rates were 57, 74 and 82 per cent respectively. CONCLUSION: In patients with venous ulceration and isolated superficial venous incompetence, superficial venous surgery can produce ulcer healing in the majority of patients without the need for perforator surgery, postoperative compression bandaging or skin grafting.

Adult↗
PubMed1999

Infrainguinal revascularisation in the era of vein-graft surveillance--do clinical factors influence long-term outcome?

OBJECTIVES: To investigate the variables affecting the long-term outcome of infrainguinal vein bypass grafts that have undergone postoperative surveillance. DESIGN: A retrospective analysis. PATIENTS AND METHODS: Details of 299 consecutive infrainguinal vein grafts performed in 275 patients from a single university hospital were collected and analysed. All grafts underwent postoperative duplex surveillance. Factors affecting patency, limb salvage and survival rates were examined. These factors were gender, diabetes, hypertension, aspirin, warfarin, ischaemic heart disease, run-off, graft type, early thrombectomy, level of anastomoses and indication for surgery. RESULTS: The 6-year primary, primary assisted and secondary patency rates were 23, 47, and 57%, respectively. Six-year limb salvage and patient survival were 68 and 45%, respectively. Primary patency was adversely influenced by the use of composite vein grafts. Early thrombectomy was the only factor that significantly influenced secondary patency. Limb salvage was worse in diabetic limbs, limbs with poor run-off and in grafts that required early thrombectomy. Postoperative survival was better in males, claudicants and in patients who took aspirin. CONCLUSIONS: Although co-morbid factors did not influence graft patency rates, diabetes did adversely effect limb salvage. This study, like others before it, confirms that aspirin significantly reduces long-term mortality in patients undergoing infrainguinal revascularisation.

Angioplasty↗
PubMed1999

A policy of quality control assessment helps to reduce the risk of intraoperative stroke during carotid endarterectomy.

OBJECTIVES: A pilot study in our unit suggested that a combination of transcranial Doppler (TCD) plus completion angioscopy reduced incidence of intra-operative stroke (i.e. patients recovering from anaesthesia with a new deficit) during carotid endarterectomy (CEA). The aim of the current study was to see whether routine implementation of this policy was both feasible and associated with a continued reduction in the rate of intraoperative stroke (IOS). MATERIALS AND METHODS: Prospective study in 252 consecutive patients undergoing carotid endarterectomy between March 1995 and December 1996. RESULTS: Continuous TCD monitoring was possible in 229 patients (91%), while 238 patients (94%) underwent angioscopic examination. Overall, angioscopy identified an intimal flap requiring correction in six patients (2.5%), whilst intraluminal thrombus was removed in a further six patients (2.5%). No patient in this series recovered from anaesthesia with an IOS, but the rate of postoperative stroke was 2.8%. CONCLUSIONS: Our policy of TCD plus angioscopy has continued to contribute towards a sustained reduction in the risk of IOS following CEA, but requires access to reliable equipment and technical support. However, a policy of intraoperative quality control assessment may not necessarily alter the rate of postoperative stroke.

Aged↗
PubMed1999

Transcranial Doppler directed dextran therapy in the prevention of carotid thrombosis: three hour monitoring is as effective as six hours.

BACKGROUND: Six hours' monitoring by transcranial Doppler (TCD) has been successful in directing Dextran therapy in patients at high risk of thrombotic stroke after carotid endarterectomy (CEA). OBJECTIVES: Is 3 h of routine monitoring as effective as 6 h in the prevention of early postoperative thrombotic stroke? DESIGN: Prospective, consecutive study in all patients with an accessible cranial window. METHODS: One hundred and sixty-six patients undergoing CEA underwent 3 h of postoperative monitoring by TCD. Any patient with > 25 emboli detected in any 10 min period or those with emboli that distorted the arterial waveform were commenced on an incremental infusion of dextran 40. RESULTS: The majority of patients destined to embolise will do so within the first 2 postoperative hours. Dextran therapy was instituted in nine patients (5%) and rapidly controlled this phase of embolisation although the dose had to be increased in three (33%). No patient suffered a postoperative carotid thrombosis but one suffered a minor stroke on day 5 and was found to have profuse embolisation on TCD; high dose dextran therapy was again instituted, the embolus count rate fell rapidly and he made a good recovery thereafter. Overall, the death and disabling stroke rate was 1.2% and the death/any stroke rate was 2.4%. CONCLUSION: Three hours of postoperative TCD monitoring is as effective as 6 h in the prevention of postoperative carotid thrombosis.

Adult↗