Biomedical subjects
Publications and source records attributed to J R Boyle.
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BACKGROUND: Inflammatory abdominal aortic aneurysms (IAAA) are a variant of aortic aneurysm characterised by extensive peri-aneurysmal fibrosis, thickened walls and dense adhesions and represent between 3 and 10% of all abdominal aortic aneurysms (AAA). Surgery is technically challenging and is still associated with an increased morbidity and mortality. Controversy exists about aetiology and pathogenesis. METHODS: We review the literature on the current theories, the available imaging modalities and the current thinking on management of IAAA. A Medline database search was performed. Articles were cross-referenced. RESULTS AND CONCLUSIONS: Aneurysm development is multifactorial with important genetic and environmental factors. The literature supports the theory that IAAA arise from the same antigenic stimulus that is responsible for the non-IAAA, representing one extreme of an inflammatory spectrum. The results after open repair have improved and there is now little difference in the mortality between non-IAAA and IAAA repair. However, there is likely to be a role for endovascular stenting in IAAA management and this requires further study. It is clear that closer follow-up of patients after IAAA repair with either technique is necessary to monitor the inflammatory process. No evidence-based follow-up protocol exists but three to six-monthly monitoring of renal function and erythrocyte sedimentation rate (ESR) for 24 months post-repair would seem a reasonable regime.
OBJECTIVES: The greatest benefit of endovascular AAA repair (EVAR) may be in the management of rupture (RAAA). However, the detailed anatomical assessment required for EVAR has lead to concerns of surgical delay and death during cross-sectional imaging. In this study, we prospectively assessed patients with RAAA and correlated time of hospital arrival with time of surgery or death to ascertain whether these concerns are justified. METHODS: All patients presenting with RAAA between October 2000 and December 2002 were included. The hospital arrival time, onset of surgery or time of death, were recorded, as were demographic and physiological parameters. RESULTS: One hundred consecutive patients were studied, median age 75 years (range 54-94). Seventy-nine patients underwent attempted conventional surgical repair and 21 were palliated. The median delay from arrival to operation was 159 min (range 16-1450 min). Mortality in the surgical group was not affected by the length of delay (p = 1.0) or by CT scanning (p = 0.34). The median time from arrival to death in the non-surgical group was 435 min (15 min-6 days). CONCLUSIONS: Most patients who present with ruptured AAA experience a significant delay prior to surgery. This study suggests it is safe to assess the majority of RAAA patients for EVAR.
OBJECTIVES: Case selection for surgery in patients presenting with ruptured abdominal aortic aneurysms (RAAA) is often difficult. A previous retrospective review identified five pre-operative risk factors associated with mortality [J Vasc Surg 23 (1996) 123]. In this study we aimed to identify whether these criteria could be usefully applied prospectively in patients presenting with RAAA. METHODS: All patients presenting with RAAA from October 2000 to December 2002 were included. The criteria were recorded with the time they were available and the time surgery commenced. The decision to operate was made on clinical grounds and no patient was refused surgery on the basis of these criteria. RESULTS: One hundred consecutive patients were studied, median age 75 (range 54-94). The operative mortality was 32.9% (26/79 patients). Surgical mortality increased with the number of positive criteria and was 8% (2/24), 24% (7/29), 55% (11/20) and 100% (6/6) for scores, 0, 1, 2 and > or =3, respectively. Age and conscious level were available in every patient. However, an ECG, haemoglobin and creatinine results were only available in 94, 81, and 69%, respectively. CONCLUSIONS: The scoring system accurately predicted operative mortality. The score was available in the majority of cases and may help the surgeon give informed consent to patients and relatives prior to surgical intervention.
This paper briefly describes the framework of artificial human vision systems and identifies several image processing techniques which could enhance the information content of artificially-induced images. We describe our own research in this area, which aims to assess the performance of proposed devices, specifically the usefulness of low quality images associated with electronic visual prostheses. Our subjective assessment studies using representative test patterns have investigated how much information and what types of information are needed to recognise or perceive a scene. 174 normally sighted subjects viewed a set of low quality (low spatial resolution and low grey-scale) static images. Results from this testing has identified informative image processing operations which lead to improved understanding of picture content.
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BACKGROUND: The Portsmouth Physiological and Operative Severity Score for enUmeration of Mortality and morbidity (P-POSSUM) equation permits comparative audit that allows for differences in case mix. The methodology has previously been shown accurately to model general surgical and vascular surgical patients. Patients with a ruptured abdominal aortic aneurysm (AAA) are, however, very different from elective patients and it may be hypothesized that they require their own specific risk model. METHODS: POSSUM data on 444 (213 emergency, 231 elective) admissions for AAA surgery between August 1993 and July 2000 were analysed using the P-POSSUM equation for general surgery and the P-POSSUM equations developed for vascular surgery. RESULTS: All equations successfully modelled the elective aneurysms but failed to fit the emergency aneurysms, and the elective and emergency aneurysms combined. This suggested that admission method (not a POSSUM data item) is an important factor for patients with AAA. However, with these data it was not possible to generate a model, including admission method, that successfully modelled the combined elective and emergency data. The 213 emergency aneurysm repairs were divided into two groups by operation date. The first 106 (training set) were used to form logistic regression models following the P-POSSUM methodology. These models were found successfully to fit the remaining 107 records (test set) on prospective application (chi2 = 4.50, 4 d.f., P = 0.345). CONCLUSION: Ruptured AAAs appear to be different from elective AAAs and other vascular cases and require their own risk model.
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PURPOSE: To quantify the inflammatory and renal parameters in comparative cohorts of patients undergoing surgical or endovascular repair of abdominal aortic aneurysms (AAAs). METHODS: Forty-three patients (41 men; ages 58-81 years) underwent endovascular or conventional aneurysm surgery according to aortic morphology. All patients received a standard general anesthetic and had 12 serial blood and urine samples collected during the perioperative period. Samples underwent analysis for the cytokines interleukin (IL) 1beta tumor necrosis factor-alpha (TNF-alpha), and IL-6. White cell and platelet activation were estimated indirectly by measuring sL-selectin and 11-dehydrothromboxane B2, respectively. The urinary albumin:creatinine ratio (ACR) and N-acetyl-beta-D-glucosaminidase (NAG) activity were estimated to assess renal injury. Fibrinogen and fibrinogen degradation products were calculated to assess activation of the clotting cascade. RESULTS: Twenty-three patients underwent endovascular AAA repair and 20 had conventional surgery. Concentrations of IL-6 (p < 0.002) and TNF-alpha (p < 0.0004) were significantly higher in the conventional group. The ACR (p < 0.002) and urinary NAGs (p < 0.0009) were also significantly higher in this group, suggesting greater renal injury. Platelet activity was significantly greater in the endovascular group (p < 0.01), perhaps indicating thrombus organization within the aneurysm sac. CONCLUSIONS: These data suggest that the inflammatory response associated with conventional aneurysm repair is largely obviated by endovascular techniques. This may potentially translate to a lower incidence of multiple organ failure after endovascular surgery.
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BACKGROUND: Abdominal aortic aneurysms are characterized by degradation of the extracellular matrix, with a reduction in the elastin concentration of the arterial media. These changes have been linked to increased levels of endogenous metalloproteinases (MMPs) within the aorta, particularly MMP-2 and MMP-9. This provides a potential therapeutic target for pharmacological agents aimed at reducing the growth rate of small aneurysms. In this study, the ability of marimastat (an MMP inhibitor) to reduce matrix degradation was assessed in a previously described model of aneurysm disease. METHODS: Porcine aortic segments (n = 12) were preincubated in exogenous pancreatic elastase for 24 h before culture in standard conditions for 13 days with marimastat 10(-5), 10(-6) and 10(-7) mol/l. Control segments were cultured both without marimastat and without elastase. At the termination of culture, MMPs were extracted from the tissue and quantified by substrate gel enzymography. The volume fractions of elastin and collagen were determined by stereological analysis of sections stained with Miller's elastin and van Gieson's stain. RESULTS: Stereological analysis demonstrated preservation of elastin in aorta treated with marimastat at 10(-6) and 10(-5) mol/l; this was significant at the latter concentration (P = 0.007). This was accompanied by a significant reduction in active MMP-2 activity in the samples treated with marimastat 10(-5) mol/l (P < 0.01). CONCLUSION: Marimastat significantly inhibited elastin degradation and active MMP-2 production within aortic organ cultures.
OBJECTIVES: To compare changes in plasma catecholamines, acid-base status and cardiovascular dynamics in patients undergoing endovascular or conventional infrarenal abdominal aortic aneurysm (AAA) repair under standard general anaesthesia. DESIGN: Prospective cohort study. MATERIALS: 30 patients scheduled for elective infrarenal AAA repair. METHODS: Plasma epinephrine and norepinephrine concentrations, acid-base status and cardiovascular measurement were compared before surgery, and 5 min after aortic clamping and clamp release (conventional group) or occlusion and release (endovascular group) in patients undergoing endovascular (n = 15) or conventional AAA repair (n = 15). RESULTS: Arterial pH (p < 0.005) and base deficit (p < 0.05) increased, and plasma bicarbonate decreased (p < 0.005) during aortic cross-clamping in the conventional group. pH decreased further (p < 0.005), and base deficit and pCO2 increased (both p < 0.005) after clamp release. These changes were significantly greater than during endovascular repair, in whom within-group changes were not statistically significant. Values were similar in the two groups 30 min after reperfusion. Plasma epinephrine concentrations increased during conventional surgery (p < 0.05) and were greater than in the endovascular group (p < 0.05). Plasma norepinephrine concentrations increased during surgery in both groups but the changes were not statistically significant. CONCLUSIONS: Plasma catecholamine concentrations, changes in cardiovascular variables and acid-base status were increased during conventional compared with endovascular AAA repair.
Respiratory function, assessed by pre- and postoperative spirometry, and overnight pulse oximetry recordings, was compared prospectively in patients undergoing infrarenal abdominal aortic aneurysm repair by endovascular or conventional surgery. Episodic hypoxaemia was common in both groups before operation and up to the fifth night after operation. The frequency and severity of hypoxaemia were greater in the conventional group (P < 0.05). FEV1 and FVC decreased significantly on the third and fifth days after operation in both groups (P < 0.05); decreases in FVC were greater in patients undergoing conventional surgery. On the fifth day after operation, FVC had recovered to 86% and 64% of preoperative values in the endovascular and conventional groups, respectively (P < 0.05). Duration of surgery was greater (P < 0.05) and duration of postoperative artificial ventilation significantly less (P < 0.05) after endovascular repair. Postoperative PCA morphine consumption and duration of use were significantly greater (P < 0.05) in patients undergoing conventional abdominal aortic aneurysm surgery.
Endoluminal repair of abdominal aortic aneurysm (AAA) is being adopted as a less invasive alternative to conventional open repair in many centers worldwide. Although the initial results are encouraging, the long-term durability of this procedure remains unknown. Endoluminal AAA repair in 29 patients using three different devices (EVT tube Endograft(R), aortouniiliac device, and Stentortrade mark bifurcated system) is described. Overall, 24 procedures (83%) were completed successfully. Complications included two deaths due to microembolization, five early conversions, two chest infections, three patients with buttock claudication, and three patients with trashed foot. Perigraft leaks were detected in four patients (three proximal, one distal) treated with the EVT tube Endograft. Continued aneurysm expansion was observed in three of the patients. One of the leaks was discovered at the 1-year follow-up. In this patient the aneurysmal process was not retarded by endoluminal repair. The findings in this patient may have implications for the durability of this technique. Therefore, careful long-term evaluation of this procedure is recommended prior to its widespread use.
PURPOSE: Abdominal aortic aneurysms are characterized by degradation of the extracellular matrix, with a reduction in the elastin concentration of the arterial media. These changes are mediated by increased levels of endogenous metalloproteinases (MMPs) within the aorta, which provide a potential therapeutic target for pharmacologic agents aimed at reducing the growth rate of small aneurysms. In this study, the ability of doxycycline--an MMP inhibitor--to reduce matrix degradation was assessed in a previously described model of aneurysmal disease that used a brief pulse of elastase to induce MMP production and elastin degradation in arterial organ cultures. METHODS: Porcine aortic segments (n = 8) were preincubated in exogenous pancreatic elastase for 24 hours before culture in standard conditions for 13 days with both 1 and 10 mg/L doxycycline. Control segments were cultured both without doxycycline and without elastase. At the termination of culture, MMPs were extracted from the tissue and quantified by a combination of substrate gel enzymography and immunoblotting. The volume fractions of elastin and collagen were determined by stereologic analysis of sections stained with Miller's elastin and van Gieson's stain. RESULTS: Stereologic analysis demonstrated a significant preservation of elastin in aorta treated with doxycycline 10 mg/L (p < 0.001) and demonstrated that this preservation was accompanied by a significant reduction in MMP-9 activity (p < 0.02). Immunoblotting for tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) showed no decreased production in the doxycycline-treated groups. CONCLUSIONS: Therapeutic ranges of doxycycline significantly inhibited elastin degradation and MMP-9 production within aortic organ cultures. These data suggest that doxycycline may have a potential application in reducing the growth rates of small abdominal aortic aneurysms.
AIMS: Abdominal aortic aneurysms are characterised by changes in the extracellular matrix of the arterial media, in particular a reduction in elastin concentration. These changes are mediated by increased levels of endogenous matrix metalloproteinases (MMPs). Recently, calcium channel blockers have been shown to increase the proteolytic activity of MMP-2 secreted by vascular smooth muscle cells. It may therefore by hypothesised that calcium antagonists may potentiate the activity of MMPs in aneurysmal disease and thus accelerate AAA expansion. In this study, the ability of amlodipine--a calcium antagonist--to influence elastin degradation, was assessed in a previously described model of aneurysmal disease. METHODS: Porcine aortic segments (n = 8) were pre-incubated in exogenous pancreatic elastase for 24 h prior to culture in standard conditions for 6 days with 10 and 100 micrograms/l amlodipine. Control segments were cultured both with and without amlodipine and without elastase. At the termination of culture MMPs were extracted from the tissue and quantified by a combination of substrate gel enzymography and immunoblotting. The volume fractions of elastin and collagen were determined by stereological analysis of EVG stained sections. RESULTS: Gel enzymography demonstrated significantly increased MMP-9 activity in the amlodipine treated segments, median 4.218 vs. 2.809 arbitrary units (p < 0.01) and this elevated activity was reflected in a significant destruction of medial elastin 27.0 vs. 40.5% (p < 0.05). CONCLUSION: Therapeutic ranges of amlodipine significantly enhanced elastin degradation and potentiated MMP-9 activity within the aortic organ cultures.
BACKGROUND: Computed tomography (CT) has been used to assess patients following endovascular aneurysm repair to determine the need for secondary endoluminal or operative procedures. This prospective study compared CT and duplex imaging to evaluate aneurysm morphology following endoluminal aortic grafting. METHODS: Twenty patients were evaluated at regular intervals following successful endoluminal aneurysm repair. CT and duplex scanning were compared in their ability to determine aneurysm and aortic diameter, the presence of perigraft extravasation (endoleaks) and technical defects in the endograft. RESULTS: In 20 patients who were assessed 6 months after operation, duplex imaging identified four endoleaks (two early, two late; one proximal, three distal). In three cases, the aneurysm diameter progressively increased after operation. In patients with a thrombosed aneurysm sac, the aneurysm regressed at a median of 0.40 (range 0.13-0.8) cm per year. The CT findings were similar (median regression 0.43 (range 0-1.0) cm per year), although CT was unable to predict the site of the leak as accurately as duplex imaging. CT demonstrated that the diameter of the juxtarenal aorta increased following endografting. CONCLUSION: Duplex imaging is a less invasive, less costly alternative to CT in the follow-up of patients after endoluminal aortic surgery. Increase in size of the aneurysm sac following endovascular aneurysm repair strongly suggests the presence of an endoleak.