Comparative analysis of the outcomes of elective abdominal aortic aneurysm repair in England and Sweden.

BACKGROUND: There is substantial international variation in mortality after abdominal aortic aneurysm (AAA) repair; many non-operative factors influence risk-adjusted outcomes. This study compared 90-day and 5-year mortality for patients undergoing elective AAA repair in England and Sweden. METHODS: Patients were identified from English Hospital Episode Statistics and the Swedish Vascular Registry between 2003 and 2012. Ninety-day mortality and 5-year survival were compared after adjustment for age and sex. Separate within-country analyses were performed to examine the impact of co-morbidity, hospital teaching status and hospital annual caseload. RESULTS: The study included 36 249 patients who had AAA treatment in England, with a median age of 74 (i.q.r. 69-79) years, of whom 87·2 per cent were men. There were 7806 patients treated for AAA in Sweden, with a median of age 73 (68-78) years, of whom 82·9 per cent were men. Ninety-day mortality rates were poorer in England than in Sweden (5·0 versus 3·9 per cent respectively; P < 0·001), but were not significantly different after 2007. Five-year survival was poorer in England (70·5 versus 72·8 per cent; P < 0·001). Use of EVAR was initially lower in England, but surpassed that in Sweden after 2010. In both countries, poor outcome was associated with increased age. In England, institutions with higher operative annual volume had lower mortality rates. CONCLUSION: Mortality for elective AAA repair was initially poorer in England than Sweden, but improved over time alongside greater uptake of EVAR, and now there is no difference. Centres performing a greater proportion of EVAR procedures achieved better results in England.

Preoperative morphology influences thoracic aortic aneurysm sac expansion after endovascular repair.

BACKGROUND: The fate of the aneurysm sac after thoracic endovascular aortic repair (TEVAR) remains poorly defined. The aim of this study was to characterize the incidence of aneurysm sac expansion after TEVAR, and to determine the effect of aneurysm morphology on postoperative sac behaviour. METHODS: Preoperative and postoperative CT angiography (CTA) images were analysed from a proprietary database (M2S). TEVARs undertaken for thoracic aortic aneurysms from 2004 to 2013 were included. Preoperative aortic morphology was available for each patient. Post-TEVAR sac expansion was defined as an increase in aortic diameter of at least 5 mm. The influence of aortic morphological variables on sac expansion was assessed using Cox regression and Kaplan-Meier analysis. RESULTS: CTA images were available for 899 patients who underwent TEVAR. Median follow-up was 2·1 (i.q.r. 1·7-2·4) years. Some 46·0 per cent had a maximum aneurysm diameter of 55 mm or more at the time of repair. The 5-year rate of freedom from sac expansion of at least 5 mm was 60·9 per cent. The sac expansion rate after 3 years was higher when the proximal sealing zone was over 38 mm in diameter (freedom from expansion 51·2 per cent versus 76·6 per cent for diameter 38 mm or less; P < 0·001), or 20 mm or less in length (freedom from expansion 67·3 per cent versus 77·1 per cent for length exceeding 20 mm; P = 0·022). Findings for the distal sealing zone were similar. The risk of sac expansion increased according to the number of adverse morphological risk factors (freedom from expansion rate 79·1 per cent at 3 years in patients with 2 or fewer risk factors versus 45·7 per cent in those with more than 2; P < 0·001). CONCLUSION: Sac expansion was common in this cohort of patients undergoing TEVAR for thoracic aortic aneurysm. Aneurysm sac expansion was significantly influenced by adverse morphological features in the aortic stent-graft sealing zones.

Comparison of long-term mortality after ruptured abdominal aortic aneurysm in England and Sweden.

BACKGROUND: Concern has been raised regarding international discrepancies in perioperative mortality after repair of ruptured abdominal aortic aneurysm (rAAA). The variation in in-hospital mortality is difficult to interpret, owing to international differences in discharge strategies. This study compared 90-day and 5-year mortality in patients who had a rAAA in England and Sweden. METHODS: Patients undergoing rAAA repair were identified from English Hospital Episode Statistics and the Swedish Vascular Registry (Swedvasc) between 2003 and 2012. Ninety-day and 5-year mortality were compared after matching for age and sex. Within-country analyses examined the impact of co-morbidity, teaching hospital status or hospital annual caseload, adjusted with causal inference techniques. RESULTS: Some 12 467 patients underwent rAAA repair in England, of whom 83.2 per cent were men; the median (i.q.r.) age was 75 (70-80) years. A total of 2829 Swedish patients underwent rAAA repair, of whom 81.3 per cent were men; their median (i.q.r.) age was 75 (69-80) years. The 90-day mortality rate was worse in England (44.0 per cent versus 33.4 per cent in Sweden; P < 0.001), as was 5-year mortality (freedom from mortality 38.6 versus 46.3 per cent respectively; P < 0.001). In England, lower mortality was seen in teaching hospitals with larger bed capacity, higher annual caseloads and greater use of endovascular aneurysm repair (EVAR). In Sweden, lower mortality was associated with EVAR, high annual caseload, or surgery on weekdays compared with weekends. CONCLUSION: Short- and long-term mortality after rAAA repair was higher in England. In both countries, mortality was lowest in centres performing greater numbers of AAA repairs per annum, and more EVAR procedures.

Cardiovascular risk prevention and all-cause mortality in primary care patients with an abdominal aortic aneurysm.

BACKGROUND: Perioperative mortality is low for patients undergoing abdominal aortic aneurysm (AAA) repair, but long-term survival remains poor. Although patients diagnosed with AAA have a significant burden of cardiovascular disease and associated risk factors, there is limited understanding of the contribution of cardiovascular risk management to long-term survival. METHODS: General practice records within The Health Improvement Network (THIN) were examined. Patients with a diagnosis of AAA and at least 1 year of registered medical history were identified from 2000 to 2012. Medical therapies for cardiovascular risk were classified as antiplatelet, statin or antihypertensive agents. Progression to death was investigated using the G-computation formula with time-dependent co-variables to account for differences in exposure to cardiovascular risk-modifying treatments and the confounding between exposure, co-morbidities and death. RESULTS: Some 12 485 patients had a recorded diagnosis of AAA. From 2000 to 2012, prescription of medications that modify cardiovascular risk increased: from 26·6 to 76·7 per cent for statins, from 56·5 to 73·9 per cent for antiplatelet agents and from 75·3 to 84·0 per cent for antihypertensive drugs. Adjusted Kaplan-Meier curves demonstrated a better 5-year survival rate in patients receiving statins (68·4 versus 42·2 per cent), antiplatelet agents (63·6 versus 39·7 per cent) or antihypertensive agents (61·5 versus 39·1 per cent), compared with rates in patients not receiving each therapy. CONCLUSION: Appropriate risk factor modification could significantly reduce long-term mortality in patients with AAA. In the UK, up to 30 per cent of patients are not currently receiving these medications.

Epidemiological investigations on the potential transmissibility of a rare disease: the case of atypical scrapie in Great Britain.

Multiple cases of atypical scrapie in the same holding and co-existence with classical scrapie have been reported in Great Britain. A two-stage simulation tool was developed by combining a sampling algorithm and a hierarchical Bayesian model to simulate the number of positive cases of atypical scrapie from: (i) random sampling and (ii) using the actual sampled population in Great Britain, being the output probability of detection of flocks with one and more cases. Cluster analysis was conducted to assess the level of geographical over- and under-sampling over the years. The probability of detecting at least two cases of atypical scrapie in the same holding is much lower in simulated random data than in simulated actual data for all scenarios. Sampling bias in the selection of sheep for testing led to multiple sampling from fewer but larger holdings, Scotland, and areas of Wales were under-sampled and the South-West and East of England oversampled. The pattern of atypical scrapie cases observed is unlikely to be explained by a multi-case event epidemiologically linked. The co-existence of classical and atypical scrapie is a rare event with 19 holdings detected in GB and does not suggest an epidemiological link between the two types of disease.

Association of hospital structures with mortality from ruptured abdominal aortic aneurysm.

BACKGROUND: There is significant variation in the mortality rates of patients with a ruptured abdominal aortic aneurysm (rAAA) admitted to hospital in England. This study sought to investigate whether modifiable differences in hospital structures and processes were associated with differences in patient outcome. METHODS: Patients diagnosed with rAAA between 2005 and 2010 were extracted from the Hospital Episode Statistics database. After risk adjustment, hospitals were grouped into low-mortality outlier, expected mortality and high-mortality outlier categories. Hospital Trust-level structure and process variables were compared between categories, and tested for an association with risk-adjusted 90-day mortality and non-corrective treatment (palliation) rate using binary logistic regression models. RESULTS: There were 9877 patients admitted to 153 English NHS Trusts with an rAAA during the study. The overall combined (operative and non-operative) mortality rate was 67·5 per cent (palliation rate 41·6 per cent). Seven hospital Trusts (4·6 per cent) were high-mortality and 15 (9·8 per cent) were low-mortality outliers. Low-mortality outliers used significantly greater mean resources per bed (doctors: 0·922 versus 0·513, P < 0·001; consultant doctors: 0·316 versus 0·168, P < 0·001; nurses: 2·341 versus 1·770, P < 0·001; critical care beds: 0·045 versus 0·019, P < 0·001; operating theatres: 0·027 versus 0·019, P = 0·002) and performed more fluoroscopies (mean 12·6 versus 9·2 per bed; P = 0·046) than high-mortality outlier hospital Trusts. On multivariable analysis, greater numbers of consultants, nurses and fluoroscopies, teaching status, weekday admission and rAAA volume were independent predictors of lower mortality and, excluding rAAA volume, a lower rate of palliation. CONCLUSION: The variability in rAAA outcome in English National Health Service hospital Trusts is associated with modifiable hospital resources. Such information should be used to inform any proposed quality improvement programme surrounding rAAA.

International validation of a risk score for complications and reinterventions after endovascular aneurysm repair.

BACKGROUND: Lifelong surveillance is considered mandatory after endovascular repair (EVAR) of abdominal aortic aneurysms to detect endograft complications and prevent aneurysm rupture. Current protocols are not cost-effective or clinically effective. The international validity of the St George's Vascular Institute (SGVI) score for EVAR complications was examined. METHODS: The ENGAGE registry recruited patients undergoing EVAR at 79 centres in 30 countries. Reinterventions and endograft complications were recorded for up to 3 years after surgery. Preoperative aneurysm morphology was extracted from the registry database, and used to predict whether patients would be at low or high risk of complications after EVAR based on the SGVI score. Kaplan-Meier analysis was used to compare the incidence of endograft complications and reinterventions in patients predicted to be at low risk compared with those predicted to be at high risk. RESULTS: Some 1207 patients underwent EVAR, with follow-up of up to 3 years. The SGVI score accurately discriminated freedom from reinterventions (90·5 versus 79·3 per cent in low- versus high-risk patients; P < 0·001), freedom from endograft complications (77·9 versus 69·6 per cent in low- versus high-risk patients; P = 0·012), and freedom from a composite outcome measure of reinterventions or endograft complications (75·0 versus 66·1 per cent in low- versus high-risk patients; P = 0·006) during mid-term follow-up. CONCLUSION: This study has provided international validation of a morphological risk score that predicts mid-term reinterventions and endograft complications. The results may enable risk-stratified surveillance after EVAR.

Predicting aortic complications after endovascular aneurysm repair.

BACKGROUND: Lifelong surveillance is standard after endovascular repair of abdominal aortic aneurysm (EVAR), but remains costly, heterogeneous and poorly calibrated. This study aimed to develop and validate a scoring system for aortic complications after EVAR, informing rationalized surveillance. METHODS: Patients undergoing EVAR at two centres were studied from 2004 to 2010. Preoperative morphology was quantified using three-dimensional computed tomography according to a validated protocol, by investigators blinded to outcomes. Proportional hazards modelling was used to identify factors predicting aortic complications at the first centre, and thereby derive a risk score. Sidak tests between risk quartiles dichotomized patients to low- or high-risk groups. Aortic complications were reported by Kaplan-Meier analysis and risk groups were compared by log rank test. External validation was by comparison of aortic complications between risk groups at the second centre. RESULTS: Some 761 patients, with a median age of 75 (interquartile range 70-80) years, underwent EVAR. Median follow-up was 36 (range 11-94) months. Physiological variables were not associated with aortic complications. A morphological risk score incorporating maximum aneurysm diameter (P < 0·001) and largest common iliac diameter (measured 10 mm from the internal iliac origin; P = 0·004) allocated 75 per cent of patients to a low-risk group, with excellent discrimination between 5-year rates of aortic complication in low- and high-risk groups at both centres (centre 1: 12 versus 31 per cent, P < 0·001; centre 2: 12 versus 45 per cent, P = 0·002). CONCLUSION: The risk score uses commonly available morphological data to stratify the rate of complications after EVAR. The proposals for rationalized surveillance could provide clinical and economic benefits.

The shortfall in long-term survival of patients with repaired thoracic or abdominal aortic aneurysms: retrospective case-control analysis of hospital episode statistics.

OBJECTIVE: To report the contemporary life expectancy of patients undergoing abdominal (AAA) or thoracic aortic aneurysm (TAA) repair in England, relative to a healthy control population. METHODS: A retrospective observational case-control study was carried out of Hospital Episode Statistics (HES) data, an administrative dataset covering the entire English National Health Service. Patients undergoing elective repair of an abdominal or thoracic aortic aneurysm in an English NHS hospital between April 2006 and March 2011 were included. Outcome measures were 5-year all-cause mortality (in- and out-of-hospital) and adverse cardiovascular events (myocardial infarction, stroke, emergency amputation or limb revascularisation). RESULTS: 19,505 AAA and 730 TAA repairs were identified, with 75,260 and 2,721 control participants, respectively, and 27.5 (1.0-60.0) months' median (range) follow-up. Five-year survival was 67.4% for AAA against 81.1% for control participants, and 65.3% for TAA against 89.1% for control participants (p < .001). Freedom from adverse cardiovascular events was 86.1% for AAA against 93% for control participants and 89.1% for TAA against 94.4% for control participants (p < .001). CONCLUSION: Long-term survival remains poor after aneurysm repair and adverse cardiovascular events are common relative to the wider population. Further research is required to characterise and optimise cardiovascular risk prevention in patients with aortic aneurysms.

Factors limiting the health of semi-scavenging ducks in Bangladesh.

Duck rearing is well suited to coastal and lowland areas in Bangladesh. It is an important component of sustainable livelihood strategies for poor rural communities as an additional source of household income. An epidemiological study was conducted during January 2005-June 2006 on 379 households in Chatkhil of the Noakhali District, Bangladesh which were using the recently devised "Bangladesh duck model". The overall objective of the study was to identify factors that significantly contributed to mortality and constrained productivity and to generate sufficient knowledge to enable establishment of a disease surveillance system for household ducks. The overall mortality was 15.0% in Chatkhil, with predation causing a significantly higher mortality compared with diseases (p < 0.001). Common diseases were duck plague and duck cholera. Morbid ducks frequently displayed signs associated with diseases affecting the nervous and digestive systems. Haemorrhagic lesions in various organs and white multiple foci on the liver were frequently observed in dead ducks. Epidemiological analysis with a shared frailty model that accounted for clustering of data by farm was used to estimate the association between survival time and risk factors. The overall mortality rate due to disease was significantly lower in vaccinated than in non-vaccinated ducks in all zones except zone 2 (p < 0.001). Only vaccinated ducks survived in zone 1. In conclusion, duck mortality and untimely sale of ducks appeared to be important constraints for household duck production in Chatkhil. Vaccination against duck plague appears to be an effective preventive strategy in reducing the level of associated duck mortality. A successful network was established amongst farmers and the surveillance team through which dead ducks, with accompanying information, were readily obtained for analysis. Therefore, there is an opportunity for establishing a long-term disease surveillance programme for rural ducks in Chatkhil of the Noakhali District of Bangladesh.

Experimental bovine spongiform encephalopathy: detection of PrP(Sc) in the small intestine relative to exposure dose and age.

European regulations for the control of bovine spongiform encephalopathy (BSE) decree destruction of the intestines from slaughtered cattle, therefore producers have been obliged to import beef casings from countries with a negligible BSE risk. This study applies immunohistochemical and biochemical approaches to investigate the occurrence and distribution of disease-associated prion protein (PrP(Sc)) in the duodenum, jejunum and ileum of cattle orally exposed to a 1 g or 100 g dose of a titrated BSE brainstem homogenate. Samples were derived from animals at various times post exposure. Lymphoid follicles were counted and the frequency of affected follicles recorded. No PrP(Sc) was detected in the duodenum or jejunum of animals exposed to a 1 g dose or in the duodenum of animals receiving a 100 g dose. PrP(Sc) was detected in the lymphoid tissue of the ileum of 1/98 (1.0%) animals receiving the 1 g dose and in the jejunum and ileum of 8/58 (13.8%) and 45/99 (45.5%), respectively, of animals receiving the 100 g dose. The frequency of PrP(Sc)- positive follicles was less than 1.5% per case and biochemical tests appeared less sensitive than immunohistochemistry. The probability of detecting lymphoid follicles in the ileum declined with age and for the 100 g exposure the proportion of positive follicles increased, while the proportion of positive animals decreased with age. Detection of PrP(Sc) in intestinal neural tissue was rare. The results suggest that the jejunum and duodenum of BSE-infected cattle contain considerably less BSE infectivity than the ileum, irrespective of exposure dose. In animals receiving the low exposure dose, as in most natural cases of BSE, the rarity of PrP(Sc) detection compared with high-dose exposure, suggests a very low BSE risk from food products containing the jejunum and duodenum of cattle slaughtered for human consumption.