Value of diffusion-weighted MRI during carotid angioplasty and stenting.

INTRODUCTION: The incidence of neurological injury following carotid angioplasty and stenting is of great interest to those advocating it as an alternative to endarterectomy in the management of critical carotid stenosis. A significant inter-observer variation exists in determining the presence or absence of a neurological deficit following the procedure objective imaging would be advantageous. In this study, we sought to assess diffusion weighted MRI as a diagnostic tool in evaluating the incidence of neurological injury following carotid angioplasty and stenting (CAS). PATIENTS AND METHODS: The first 110 cases of CAS in our unit were included in this series. The procedure was abandoned in three patients. Patients underwent intracranial and extracranial MR angiography, together with diffusion-weighted MRI (DWI) prior to and following CAS and had a formal neurological assessment in the intensive care unit after the procedure. RESULTS: One hundred and ten Procedures were attempted in 98 patients. Twenty-eight percent were asymptomatic. Following CAS, 7.2% of patients had a positive neurological exam (two major strokes with one fatality) and 21% had positive DWI scans, equating to a sensitivity of 86% and a specificity of 85% for DWI in detecting cerebral infarction following CAS. The positive predictive value of the test was 0.3 and negative predictive value 0.99. The major stroke and death rate was 1.8%. While the use of a cerebral protection device appeared to significantly reduce the incidence of cerebral infarction (5% vs. 25%, p = 0.031) this may be a reflection of the learning curve encountered during the study. CONCLUSION: The incidence of subclinical DWI detected neurological injury was significantly higher than clinical neurological deficit following CAS. Conventional methods of neurological assessment of patients undergoing CAS may be too crude to detect subtle changes and more sensitive tests of cerebral function are required to establish whether these subclinical lesions are relevant.

Does the Mediterranean paradox extend to abdominal aortic aneurysm?

BACKGROUND: We sought to test, in men undergoing ultrasound screening for abdominal aortic aneurysms (AAA) in Western Australia, clinical impressions that the prevalence of AAA is high in Dutch migrants and low in migrants from Mediterranean countries. METHODS: In a population-based trial, men undergoing screening for AAA completed a questionnaire covering their place of birth, smoking habits and consumption of alcohol, meat, fish, salt and milk. We examined the variation by place of birth in the mean, median, 95th and 99th centiles of infrarenal aortic diameter and the prevalences of AAA defined by criteria of 30 mm, 50 mm and by the 95th and 99th centiles, in men born in Australia, of aortic diameter adjusted for height. FINDINGS: Overall, 12,203 (70.5%) of the 19 583 men took up the invitation to undergo ultrasound screening. The prevalence of AAA defined by absolute diameter was higher than average in men born in The Netherlands or Scotland (more of whom had ever smoked or smoked currently) and lower in men of Mediterranean origin (more of whom drank alcohol currently). There were no consistent relationships with simple dietary data. Correction of aortic diameter for height eliminated the significant heterogeneity in prevalence of large AAA, although a threefold variation in prevalence of AAA exceeding the 95th centile of height-adjusted diameter in Australian men persisted. INTERPRETATION: In our cohort of men, which is subject to both 'healthy migrant' and 'survivor' effects, if it exists at all, any 'Mediterranean paradox' for AAA is more modest than that for coronary disease.

Analytical modeling and numerical simulation of forces in an endoluminal graft.

PURPOSE: To utilize mathematical analysis and computational fluid dynamics (CFD) to investigate the forces acting within the pressurized aorta and upon a stent-graft and how these forces may affect the ongoing performance of the stent-graft. METHODS: Analytical force balance analysis and CFD simulations using the Fluent code were used to mimic blood flow through a bifurcated stent-graft in a person at rest. Steady-state blood flow was assumed in which the inlet pressure approximated the mean blood pressure (100 mm Hg) and the blood flow velocity was an approximation of the peak systolic flow rate (0.6 m/s). Two sizes of endoluminal grafts were analyzed: the larger graft had an inlet diameter of 3 cm and outlet diameters of 1 cm; the smaller graft diameters measured 2.4 cm proximally and 1.2 cm distally. The endografts were studied in 2 configurations: with the limbs straight and with one bent. RESULTS: For the larger graft model, the normal peak blood flow induced a downward force of 7 to 9 N on the bifurcated grafts. Bending one of the limbs of the graft produced a sideways force of 1.3 N. For the smaller endograft, the downward force was in the range of 3.1 to 5.1 N and the sideways force on a curved limb was approximately 1.5 N. The magnitude of the forces given by the analytical formulae and the CFD results agreed to within 2 significant figures. CONCLUSIONS: These results suggest that the downward force on a bifurcated stent-graft, which may exceed the force required to dislodge it when relying on radial attachment alone, is determined mostly by the proximal graft diameter. Curvature of the graft limbs creates an additional sideways force that works to displace the distal limbs of the graft from the iliac arteries.

Carotid arterial stent placement: results and follow-up in 53 patients.

PURPOSE: To describe the results, complications, and follow-up data after stent placement for occlusive internal carotid arterial disease and to compare the results with those in the literature. MATERIALS AND METHODS: Carotid arterial stent placement was attempted in 57 arteries in 53 patients. Thirty-six (68%) of 53 patients were symptomatic. Forty-two (79%) of 53 patients had one to three clinically important comorbidities and were considered at high risk. All patients underwent pre- and postprocedural independent neurologic examinations. Follow-up consisted of serial duplex ultrasonography and clinical assessment. RESULTS: The immediate technical success rate of stent deployment was 97%. Periprocedurally, three (three [5%] of 57 interventions) transient ischemic attacks and three (three [5%] of 57 interventions) minor strokes occurred. Two deaths occurred in the first 30 days (one myocardial infarction, one renal failure). One ipsilateral major stroke occurred 3 weeks after the procedure. The 30-day ipsilateral major stroke and death rate was 5% (three of 57 interventions). At 30 days, one of three patients with minor stroke had mild residual dysphasia. Treatment remained clinically successful in 48 (96%) of 50 patients. The restenosis rate was 4% (two patients). CONCLUSION: Carotid arterial stent placement in a high-risk population has morbidity and mortality rates comparable to those of carotid endarterectomy in a lower risk population. Carotid arterial stent placement can be performed with a low restenosis rate.

Long-term relative survival following surgery for abdominal aortic aneurysm: a review.

BACKGROUND: The literature reporting the long-term survival following surgery for abdominal aortic aneurysm (AAA) tends to be confusing. As a result, many clinicians looking after patients with AAA may be uncertain about the five-year survival of a given patient. This is in marked contrast to the situation for patients with malignant disease. With the current interest in population screening and endoluminal stenting for AAA, an understanding of long-term survival is increasingly important. METHODS: Thirty two publications in the English language over the last 20 years, containing data pertaining to five-year survival following routine elective surgery for AAA in unselected patients, were identified using Medline searches. RESULTS AND CONCLUSIONS: A range of important methodological differences were noted. The mean five-year crude survival was about 70% while the expected survival of a matched population was close to 80%. Survival was further reduced by about 10% in cases with significant coronary heart disease. Age alone is not a predictor of long-term relative survival with octogenarians who survive beyond 30 days surviving longer than an age-matched population.

Initial results of ultrasound screening for aneurysm of the abdominal aorta in Western Australia: relevance for endoluminal treatment of aneurysm disease.

BACKGROUND: Increased life expectancy in men during the last thirty years is largely due to the decrease in mortality from cardiovascular disease in the age group 29--69 yr. This change has resulted in a change in the disease profile of the population with conditions such as aneurysm of the abdominal aorta (AAA) becoming more prevalent. The advent of endoluminal treatment for AAA has encouraged prophylactic intervention and fueled the argument to screen for the disease. The feasibility of inserting an endoluminal graft is dependent on the morphology and growth characteristics of the aneurysm. This study used data from a randomized controlled trial of ultrasound screening for AAA in men aged 65--83 yr in Western Australia for the purpose of determining the norms of the living anatomy in the pressurized infrarenal aorta. AIMS: To examine (1) the diameters of the infra-renal aorta in aneurysmal and non-aneurysmal cases, (2) the implications for treatment modalities, with particular reference to endoluminal grafting, which is most dependent on normal and aneurysmal morphology, and (3) any evidence to support the notion that northern Europeans are predisposed to aneurysmal disease. METHODS: Using ultrasound, a randomized control trial was established in Western Australia to assess the value of a screening program in males aged 65--83 yr. The infra-renal aorta was defined as aneurysmal if the maximum diameter was 30 mm or more. Aortic diameter was modelled both as a continuous (in mm) and as a binary outcome variable, for those men who had an infra-renal diameter of 30 mm or more. ANOVA and linear regression were used for modelling aortic diameter as a continuum, while chi-square analysis and logistic regression were used in comparing men with and without the diagnosis of AAA. FINDINGS: By December 1998, of 19,583 men had been invited to undergo ultrasound screening for AAA, 12,203 accepted the invitation (corrected response fraction 70.8%). The prevalence of AAA increased with age from 4.8% at 65 yr to 10.8% at 80 yr (chi(2)=77.9, df=3, P<0.001). The median (IQR) diameter for the non-aneurysmal group was 21.4 mm (3.3 mm) and there was an increase (chi(2)=76.0, df=1, P<0.001) in the diameter of the infra-renal aorta with age. Since 27 mm is the 95th centile for the non-aneurysmal infra-renal aorta, a diameter of 30 mm or more is justified as defining an aneurysm. The risk of AAA was higher in men of Australian (OR=1.0) and northern European origin (OR=1.0, 95%CL: 0.9, 1.2) compared with those of Mediterranean origin (OR=0.5, 95%CL: 0.4, 0.7). CONCLUSION: Although screening has not yet been shown to reduce mortality from AAA, these population-based data assist the understanding of aneurysmal disease and the further development and use of endoluminal grafts for this condition.

Fenestration in endovascular grafts for aortic aneurysm repair: new horizons for preserving blood flow in branch vessels.

PURPOSE: To describe techniques for deploying fenestrated stent-grafts that use partial graft deployment and guided tracking of the fenestration to the arterial orifice. TECHNIQUE: Fenestrations have been added to custom-made tube grafts and commercially manufactured Zenith stent-graft systems to preserve perfusion of aortic side branches. Partial device deployment, orientation markers on the endograft, and intraoperative angiography enable maneuvering of the fenestration over the orifice of the target vessel with the aid of guiding catheters. Placement of a Palmaz stent overlapping the fenestration and vessel orifice secures the junction. Two variations of fenestration have preserved blood flow in renal arteries during endovascular repair of abdominal aortic aneurysms (AAAs); similar techniques have maintained flow to the celiac axis in a thoracic aortic aneurysm. CONCLUSIONS: Accurate placement of a fenestration over the orifice of a target vessel is feasible, but long-term maintenance of position is dependent on secure graft fixation. This capability brings us a step closer to overcoming the problem of inadequate necks in infra-renal AAAs, especially when the neck is foreshortened by asymmetry of the renal origins. It may also pave the way for the eventual replacement of the entire aorta with an endoluminal graft.

Screening for abdominal aortic aneurysm: lessons from a population-based study.

OBJECTIVES: To test the acceptability of screening and to identify modifiable risk factors for abdominal aortic aneurysm (AAA) in men. DESIGN: A trial of ultrasound screening for AAA in a population-based random sample of men aged 65-83 years, and a cross-sectional case-control comparison of men in the same sample. PARTICIPANTS: 12,203 men who had an ultrasound examination of their abdominal aorta, and completed a questionnaire covering demographic, behavioural and medical factors. MAIN OUTCOME MEASURES: Prevalence of AAA, and independent associations of AAA with demographic, medical and lifestyle factors. RESULTS: Invitations to screening produced a corrected response of 70.5%. The prevalence of AAAs (> 30 mm) rose from 4.8% in men aged 65-69 years to 10.8% in those aged 80-83 years. The overall prevalence of large (> 50 mm) aneurysms was 0.69%. In a multivariate logistic model Mediterranean-born men had a 40% lower risk of AAA (> 30 mm) compared with men born in Australia (odds ratio [OR], 0.6; 95% CI, 0.4-0.8), while ex-smokers had a significantly increased risk of AAA (OR, 2.3; 95% CI, 1.9-2.8), and current smokers had even higher risks. AAA was significantly associated with established coronary and peripheral arterial disease and a waist:hip ratio greater than 0.9; men who regularly undertook vigorous exercise had a lower risk (OR, 0.8; 95% CI, 0.7-1.0). CONCLUSION: Ultrasound screening for AAA is acceptable to men in the likely target population. AAA shares some but not all of the risk factors for occlusive vascular disease, but the scope for primary prevention of AAA in later life is limited.

Influence of gender on outcome from ruptured abdominal aortic aneurysm.

BACKGROUND: The aim of the present study was to compare outcomes following ruptured abdominal aortic aneurysm (AAA) in men and women. METHODS: Overall mortality from ruptured AAA was compared in men and women using the Western Australia Health Services Research Database. The linked chains of de-identified hospital morbidity and death records were selected using the ICD-9-CM (International Classification of Diseases - Clinical Modification) diagnostic and procedure codes pertaining to AAA. Cases were divided into three groups for analysis: patients who died without admission to hospital, those admitted to hospital with a ruptured AAA but who did not undergo operation, and patients who underwent operation for ruptured AAA. RESULTS: Ruptured AAA occurred in 648 men and 225 women over the age of 55 years during the decade 1985-1994. Only 50 per cent of women, compared with 59 per cent of men, were admitted to hospital. Of those admitted to hospital only 37 per cent of women underwent operation, compared with 63 per cent of men. The overall mortality rate from ruptured AAA was 90 per cent in women and 76 per cent in men (chi2 = 50.34, 1 d.f., P < 0.0001). Although women were, on average, 6 years older than men, this unfavourable pattern occurred across all age groups. CONCLUSION: Women with a ruptured AAA are more likely to die than men. More research is required to identify the causes of this sex difference.

The potential for a selective screening strategy for abdominal aortic aneurysm.

OBJECTIVES: To investigate the feasibility of selective screening for abdominal aortic aneurysm (AAA) based on identification of a target group of manageable size defined by risk factors for AAA. SETTING: Male residents of Perth, Western Australia, aged 65-83 years, who participated in a randomised controlled trial of ultrasound screening for AAA. METHODS: Eligible men were identified from the electoral roll and invited to attend a screening clinic. Those who attended completed a questionnaire, had a limited physical examination, and underwent an ultrasound examination to identify the maximum diameter of the infrarenal aorta. Data on risk factors collected from the first 8995 men seen were used to calculate a multivariate risk score for the remaining 2755 men who were screened. Centiles of the risk score were used to define potential target groups for screening and the sensitivity and specificity of each of these selective screening strategies were calculated. We repeated the calculation separately for AAAs of at least 30 mm, 40 mm, and 50 mm in diameter. RESULTS: We found that screening half of the male population aged 65-83 years would find approximately 75% of AAAs, regardless of their size, whereas screening only current smokers in this population would find approximately 20% of AAAs. CONCLUSIONS: Selective screening for AAA using easily recognisable risk factors is feasible but is not worthwhile as approximately 25% ofclinically significant cases would be missed.

Long term relative survival after surgery for abdominal aortic aneurysm in western Australia: population based study.

OBJECTIVE: To determine the long term relative survival of all patients who had surgery for abdominal aortic aneurysm in Western Australia during 1985-94. DESIGN: Population based study. SETTING: Western Australia. SUBJECTS: All patients who had had surgery for abdominal aortic aneurysm in Western Australia during 1985-94. MAIN OUTCOME MEASURES: Morbidity and mortality data of patients admitted and surgically treated for abdominal aortic aneurysm in Western Australia during 1985-94. Elective, ruptured, and acute non-ruptured cases were analysed separately. Independent analyses for sex and patients aged 80 years or more were also undertaken. Postoperative (>30 days) relative survival was assessed against age and sex matched controls. RESULTS: Overall, 1475 (1257 men, 218 women) cases were identified. The crude five year survival after elective surgery, including deaths within 30 days of surgery, was 79% for both men and women. When compared with a matched population the five year relative survival after elective surgery was 94.9% (95% confidence interval 89.9% to 99.9%) for men but only 88.0% (76.3% to 99.7%) for women. The five year relative survival of those aged 80 years and over was good: 116.6% (89.1% to 144.0%) compared with 92.4% (87.7% to 97.0%) for those under 80 years of age (men and women combined). Cardiovascular disease caused 57.8% of the 341 deaths after 30 days. CONCLUSION: In a condition such as abdominal aortic aneurysm, which occurs in elderly patients, relative survival is more clinically meaningful than crude survival. The five year relative survival in cases of elective and ruptured abdominal aortic aneurysm was better in men than in women. This is probably because of greater comorbidity in women with abdominal aortic aneurysm and this deserves more attention in the future. The long term survival outcome in octogenarians supports surgery in selected cases.

Population-based record linkage study of the incidence of abdominal aortic aneurysm in Western Australia in 1985-1994.

BACKGROUND: The incidence of abdominal aortic aneurysm (AAA) has increased steadily during the past 30 years. METHODS: Trends in the incidence and surgical intervention for AAA in Western Australia were reviewed for the interval 1985-1994. A population-based health database was used to link morbidity and mortality records of all patients aged 55 years or more who died from rupture or were admitted and treated surgically for AAA. Three groups were separated for analysis: patients with a ruptured AAA, those admitted for elective repair and those admitted as an emergency with an acute (non-ruptured) aneurysm. RESULTS: There was a decline in the incidence of both emergency and elective procedures for AAA after 1992. While the mortality rate from ruptured AAA has also fallen since 1991, the overall case fatality rate for ruptured AAA has fallen by only 1.3 per cent (from 80.7 to 79.3 per cent). CONCLUSION: The decline in mortality rate and emergency procedures may result from a fall in the incidence of ruptured AAA, due to an increasing rate of elective surgery before 1992. The decline in elective procedures from 1992 may be due to a fall in the prevalence of AAA owing to high rates of elective surgery, or to a fall in the incidence of the disease itself.

The Quality of Surgical Care Project: benchmark standards of open resection for abdominal aortic aneurysm in Western Australia.

BACKGROUND: The Quality of Surgical Care Project (QSCP) was established in May 1996, to evaluate surgical outcomes and where indicated, recommend changes to improve the quality of surgical care in Western Australia (WA). The purpose of this study is to establish benchmark standards in WA for operative mortality, 5-year survival and length of stay in all patients who were surgically treated for aneurysm of the abdominal aorta (AAA) in WA. METHODS: The WA Linked Database was used to link the morbidity and mortality records of all patients admitted and surgically treated for AAA in WA from 1985 to 1994. The linked chains of de-identified hospital morbidity and death records were selected using diagnostic and procedure codes pertaining to AAA. Three groups were separated for analysis: those admitted for rupture, those admitted for elective repair, and those who were admitted to hospital as an emergency without mention of rupture but who underwent repair for AAA. Independent analysis for gender and patients 80 years or more were included in the study. Patients were excluded from the study if they were less than 55 years of age. RESULTS: A total of 1475 cases (1257 males, 218 females) were identified. The mean age in elective cases was 70.4 years in males and 72.4 years in females, and for rupture the mean ages were 71.9 and 74.8 years, respectively. Median length of stay for males was 12 days for elective cases. Admission type or age did not significantly influence length of stay. Thirty-day mortality in males was 4.4% for elective repair and 36.7% for ruptured AAA and 5-year survival was 71.7 and 47.7%, respectively. The overall case fatality rate for ruptured AAA was 79.3% which included those cases who died from rupture without being admitted to hospital. CONCLUSIONS: These community-wide data provide a realistic measure of surgical performance for open repair of AAA. The outcomes for elective and rupture repair for AAA compare favourably with standards reported by international centres of excellence. They also support the use of this procedure in patients over 80 years of age with rupture. This information can be used for ongoing audit purposes and as a benchmark for the introduction of new treatment modalities.

The Quality of Surgical Care Project: a model to evaluate surgical outcomes in Western Australia using population-based record linkage.

BACKGROUND: The aim of this study is to establish a model to evaluate surgical outcomes and, where indicated, recommend changes to improve the quality of surgical care in Western Australia (WA). Open resection for aneurysm of the abdominal aorta was the first procedure evaluated and the results are reported in an accompanying paper. METHODS: The Quality of Surgical Care Project (QSCP) is conducted under the aegis of the Royal Australasian College of Surgeons (RACS) in WA, and brings together a multidisciplinary team of surgeons, public health researchers and health service administrators. The Western Australia Health Services Research Linked Database (the WA Linked Database) is used to provide linked chains of patients records residing in the state health department from the following sources: hospital morbidity data system, birth and death records, mental health services data, cancer registrations and midwives' notifications. This links 16 years of population-based patient records from 1980, including all public and private hospital admissions and re-admissions. The Quality of Surgical Care Project was established to use and to correlate the data from the WA Linked Database. RESULTS: The result is a powerful database for a contained population that is available for scientific analysis by a multidisciplinary team of clinical epidemiologists, surgeons and health service managers. Users will have the ability to establish benchmark standards for the outcomes of surgical procedures in WA for use in quality improvement programmes run by the College and will facilitate self-directed performance auditing activities as a commitment to greater community accountability. CONCLUSIONS: The Quality of Surgical Care Project provides a potential model of benefits to be realized by both the medical profession and the community through multidisciplinary collaboration supported by adequate information. Although migration from WA is relatively low, future linkage to the state electoral roll will allow correction for any population change.

Endovascular conversion procedure for failed primary endovascular aortic stent-grafts.

Initial failure of successful deployment of endovascular aortic stent-grafts can be due to a variety of factors and frequently requires surgical intervention. We describe an endovascular technique for salvaging initially failed tubular aortic and bifurcated aortoiliac stent-grafts with reference to three cases.

Comparison of transperitoneal and retroperitoneal approaches for infrarenal aortic surgery: early and late results.

The retroperitoneal approach to the infrarenal aorta was purported to have a shorter recovery and reduced degree of surgical stress than the transperitoneal approach. Hence, this study aimed to determine any advantages of one approach over the other. One hundred patients undergoing infrarenal aortic surgery between 1989 and 1992 were randomized to the transperitoneal or retroperitoneal approach; 64 operations were for aneurysms (32 transperitoneal, 32 retroperitoneal) and 36 for occlusive disease (18 transperitoneal, 18 retroperitoneal). Parameters monitored were operating time, cross-clamp time, blood loss, fluid requirement in first 24 h, analgesia requirements, gastrointestinal function, morbidity, mortality and length of stay in intensive care and hospital. A minimum 3-year follow-up was obtained to assess mortality and wound problems. Inter-group demographic data were comparable. There was no significant difference between the two approaches for: operating time 190 versus 202 min, P = 0.26); cross-clamp time (72 versus 81 min, P = 0.93); blood loss (1095 versus 1072 ml, P = 0.56); 24-hour fluid requirements (6900 versus 7000 ml, P = 0.45); analgesia requirements (60 versus 55 mg, P = 0.37), gastrointestinal function, morbidity (P = 0.75), mortality, and length of stay in intensive care (2 versus 2 days, P = 0.80) and hospital (10.5 versus 10 days, P = 0.76). In the long term there were significantly more wound problems (bulging, hernias and wound pain) in the retroperitoneal group. Long-term mortality was similar in both groups.

The Perth endoluminal bifurcated graft system--development and early experience.

The study aim was to develop a reliable endoluminal graft system that would enable the deployment of a bifurcated graft for infrarenal abdominal aortic aneurysms. A life-size plastic model was made of an abdominal aorta and iliac arteries, with a 50-mm infrarenal abdominal aortic aneurysm. This model was used to develop and test self-expanding graft systems, based on a barbed Gianturco stent and series of stainless-steel 'Z' stents within a woven Dacron graft. The bifurcated system developed involves a trouser graft with one long leg and one short. This graft-system is delivered through one femoral artery with deployment of the proximal aortic end infrarenally and the longer trouser leg within the ipsilateral common iliac artery. The short trouser leg is left hanging free within the distal end of the aneurysm cavity, just above the bifurcation. It is held open by a self-expanding stent and is cannulated from the contralateral femoral artery with a guide wire. A simple straight self-expanding stented graft is then deployed to extend this short trouser leg down into the common iliac artery, effectively creating an extension to the short leg. The graft system has been deployed in 21 patients with satisfactory exclusion of the aneurysm in 17 (81%). There has been one mortality and no conversion to open repair. All 17 aneurysms remain excluded at median follow-up of 30 (range 4-60) weeks. None of the four graft stents that leaked (two proximal and two distal) sealed spontaneously. Deployment of the uncovered Gianturco stent across the renal artery origins in 18 cases (85%) has not been associated with renal artery occlusion or deterioration in renal function at a median follow-up of 30 (range 4-60) weeks. The ability to deploy a bifurcated system increases the potential for endoluminal treatment of abdominal aortic aneurysm.