Variations in carotid sinus anatomy and their relevance to carotid interventions.

BACKGROUND: The carotid sinus (CS) is a dilatation in the carotid bifurcation usually at the origin of proximal internal carotid artery (ICA). It contains baroreceptors which influence blood pressure. Variations in the location of the CS are of importance as atheromatous plaque commonly forms in this area and procedures such as carotid endarterectomy are performed to reduce the risk of stroke. Inadvertent stimulation of the CS baroreceptors during interventions can have profound effects on the patient's haemodynamic status both intra- and postoperatively, causing serious complications. The aim of this study is to determine the inter- and intra-individual variations in the location of the CS. MATERIALS AND METHODS: Eighty-two carotid arteries were dissected bilaterally from 41 cadavers. The locations of the CS were noted and divided into four potential sites. RESULTS: The commonest site is the origin of the ICA (74.3%), but the CS can also be found in the distal part of the common carotid artery (CCA) inferior to the bifurcation (17.1%); at the bifurcation involving the distal CCA and origins of both the external carotid artery (ECA) and ICA (7.32%); and at the origin of the ECA (1.22%). In individual cadavers, the CS was located at the origin of the ICA in 97.6% on at least one side. The sites of the CS were asymmetrical in 34.1%. CONCLUSIONS: Clinicians performing carotid interventions should be aware of these anatomical variations to avoid inadvertent stimulation of the CS which can cause profound bradycardia and hypotension.

ClariVein® - Early results from a large single-centre series of mechanochemical endovenous ablation for varicose veins.

Objectives This study assessed the effectiveness and patient experience of the ClariVein® endovenous occlusion catheter for varicose veins from a large single-centre series in the UK. Methods A total of 300 patients (371 legs) underwent ClariVein® treatment for their varicose veins; 184 for great saphenous vein (GSV) incompetence, 62 bilateral GSV, 23 short saphenous vein (SSV), 6 bilateral SSV and 25 combined unilateral great saphenous vein and SSV. Patients were reviewed at an interval of two months post procedure and underwent Duplex ultrasound assessment. Postoperative complications were recorded along with patient satisfaction. Results All 393 procedures were completed successfully under local anaesthetic. Complete occlusion of the treated vein was initially achieved in all the patients, but at eight weeks' follow-up, there was only partial obliteration in 13/393 (3.3%) veins. These were all successfully treated with ultrasound-guided foam sclerotherapy. Procedures were well tolerated with a mean pain score of 0.8 (0-10). No significant complications were reported. Conclusions ClariVein® can be used to ablate long and short saphenous varicose veins on a walk-in-walk-out basis. Bilateral procedures can be successfully performed, and these are well tolerated as can multiple veins in the same leg. Early results are promising but further evaluation and longer term follow-up are required.

Remote preconditioning and major clinical complications following adult cardiovascular surgery: systematic review and meta-analysis.

BACKGROUND: A number of 'proof-of-concept' trials suggest that remote ischaemic preconditioning (RIPC) reduces surrogate markers of end-organ injury in patients undergoing major cardiovascular surgery. To date, few studies have involved hard clinical outcomes as primary end-points. METHODS: Randomised clinical trials of RIPC in major adult cardiovascular surgery were identified by a systematic review of electronic abstract databases, conference proceedings and article reference lists. Clinical end-points were extracted from trial reports. In addition, trial principal investigators provided unpublished clinical outcome data. RESULTS: In total, 23 trials of RIPC in 2200 patients undergoing major adult cardiovascular surgery were identified. RIPC did not have a significant effect on clinical end-points (death, peri-operative myocardial infarction (MI), renal failure, stroke, mesenteric ischaemia, hospital or critical care length of stay). CONCLUSION: Pooled data from pilot trials cannot confirm that RIPC has any significant effect on clinically relevant end-points. Heterogeneity in study inclusion and exclusion criteria and in the type of preconditioning stimulus limits the potential for extrapolation at present. An effort must be made to clarify the optimal preconditioning stimulus. Following this, large-scale trials in a range of patient populations are required to ascertain the role of this simple, cost-effective intervention in routine practice.

High-resolution magnetic resonance imaging-based biomechanical stress analysis of carotid atheroma: a comparison of single transient ischaemic attack, recurrent transient ischaemic attacks, non-disabling stroke and asymptomatic patient groups.

BACKGROUND: Vulnerable carotid plaques are associated with cerebrovascular ischaemic events. High-resolution magnetic resonance (MR) imaging not only allows the morphological assessment of such plaques, but also provides geometrical data, which can be used for biomechanical stress analysis. We assess its utility to assess the plaque stress profiles of symptomatic (transient ischaemic attack (TIA) and non-disabling stroke) and asymptomatic patients. METHODS: A total of 70 consecutive patients with confirmed underlying carotid artery disease underwent carotid MR imaging of their carotid artery in a 1.5-T MR system using a standard carotid atheroma imaging protocol. MR images were manually segmented for different plaque components and used for biomechanical stress analysis. The maximum critical stress (M-CStress) for various clinical groups was determined and compared. RESULTS: M-CStress of symptomatic plaques (n = 45) was significantly higher than for asymptomatic plaques (n = 25) (median (interquartile range (IQR): 275 kPa (190-390) vs. 165 kPa (120-200), p = 0.0001)). Within the symptomatic group, no M-CStress differences were present between the TIA (n = 30) and stroke (n = 15) patients (260 kPa (190-370) vs. 295 kPa (200-510), p = 0.31). Within the TIA patient cohort, those who had presented with recurrent TIAs (n = 6) had significantly higher stresses than patients who had suffered a single episode (n = 24) (425 kPa (285-580) vs. 250 kPa (180-310), p = 0.001). CONCLUSIONS: Symptomatic carotid plaques, particularly those associated with recurrent TIAs, have high biomechanical stresses. As there is pre-existing evidence to suggest that high biomechanical stresses are associated with plaque vulnerability, MR-imaging-based stress analysis has the potential to identify high-risk patients with vulnerable plaques.

Temporal dependence of in vivo USPIO-enhanced MRI signal changes in human carotid atheromatous plaques.

INTRODUCTION: Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI has been shown to be a useful modality to image activated macrophages in vivo, which are principally responsible for plaque inflammation. This study determined the optimum imaging time-window to detect maximal signal change post-USPIO infusion using T1-weighted (T1w), T2*-weighted (T2*w) and quantitative T2* (qT2*) imaging. METHODS: Six patients with an asymptomatic carotid stenosis underwent high resolution T1w, T2*w and qT2* MR imaging of their carotid arteries at 1.5 T. Imaging was performed before and at 24, 36, 48, 72 and 96 h after USPIO (Sinerem, Guerbet, France) infusion. Each slice showing atherosclerotic plaque was manually segmented into quadrants and signal changes in each quadrant were fitted to an exponential power function to model the optimum time for post-infusion imaging. RESULTS: The power function determining the mean time to convergence for all patients was 46, 41 and 39 h for the T1w, T2*w and qT2* sequences, respectively. When modelling each patient individually, 90% of the maximum signal intensity change was observed at 36 h for three, four and six patients on T1w, T2*w and qT2*, respectively. The rates of signal change decrease after this period but signal change was still evident up to 96 h. CONCLUSION: This study showed that a suitable imaging window for T1w, T2*w and qT2* signal changes post-USPIO infusion was between 36 and 48 h. Logistically, this would be convenient in bringing patients back for one post-contrast MRI, but validation is required in a larger cohort of patients.

Hepatic artery aneurysm repair: a case report.

INTRODUCTION: Hepatic artery aneurysms remain a clinically significant entity. Their incidence continues to rise slowly and mortality from spontaneous rupture is high. Repair is recommended in those aneurysms greater than 2 cm in diameter. It is not surprising that vascular comorbidities, such as ischaemic heart disease, are common in surgical patients, particularly those with arterial aneurysms such as these. The decision of when to operate on patients who require urgent surgery despite having recently suffered an acute coronary syndrome remains somewhat of a grey and controversial area. We discuss the role of delayed surgery and postoperative followup of this vascular problem. CASE PRESENTATION: A 58-year-old man was admitted with a 5.5 cm hepatic artery aneurysm. The aneurysm was asymptomatic and was an incidental finding as a result of an abdominal computed tomography scan to investigate an episode of haemoptysis (Figure 1). Three weeks prior to admission, the patient had suffered a large inferior myocardial infarction and was treated by thrombolysis and primary coronary angioplasty. Angiographic assessment revealed a large aneurysm of the common hepatic artery involving the origins of the hepatic, gastroduodenal, left and right gastric arteries and the splenic artery (Figures 2 and 3). Endovascular treatment was not considered feasible and immediate surgery was too high-risk in the early post-infarction period. Therefore, surgery was delayed for 3 months when aneurysm repair with reconstruction of the hepatic artery was successfully performed. Graft patency was confirmed with the aid of an abdominal arterial duplex. Plasma levels of conventional liver function enzymes and of alpha-glutathione-S-transferase were within normal limits. This was used to assess the extent of any hepatocellular damage perioperatively. The patient made a good recovery and was well at his routine outpatient check-ups. CONCLUSION: There is no significant difference in cardiac risk in patients who have undergone vascular surgery within 6 months of a myocardial infarction compared with those who have had the operation in the 6 to12 month time frame. Use of alpha-glutathione-S-transferase gives an indication of the immediate state of hepatic function and should be used in addition to traditional liver function tests to monitor hepatic function postoperatively.

Utility of USPIO-enhanced MR imaging to identify inflammation and the fibrous cap: a comparison of symptomatic and asymptomatic individuals.

BACKGROUND AND PURPOSE: Inflammation is a risk factor the vulnerable atheromatous plaque. This can be detected in vivo on high-resolution magnetic resonance (MR) imaging using a contrast agent, Sinerem, an ultra-small super-paramagnetic iron oxide (USPIO). The aim of this study was to explore whether there is a difference in the degree of MR defined inflammation using USPIO particles, between symptomatic and asymptomatic carotid plaques. We report further on its T(1) effect of enhancing the fibrous cap, which may allow dual contrast resolution of carotid atheroma. METHODS: Twenty patients with carotid stenosis (10 symptomatic and 10 asymptomatic) underwent multi-sequence MR imaging before and 36 h post-USPIO infusion. Images were manually segmented into quadrants and signal change in each quadrant was calculated following USPIO administration. Mean signal change across all quadrants were compared between the two groups. RESULTS: Symptomatic patients had significantly more quadrants with a signal drop than asymptomatic individuals (75% vs. 32%, p<0.01). Asymptomatic plaques had more quadrants with signal enhancement than symptomatic ones (68% vs. 25%, p<0.05); their mean signal change was also higher (46% vs. 15%, p<0.01) and this appeared to correlate with a thicker fibrous cap on histology. CONCLUSIONS: Symptomatic patients had more quadrants with signal drop suggesting larger inflammatory infiltrates. Asymptomatic individuals showed significantly more enhancement possibly suggesting greater stability as a result of thicker fibrous caps. However, some asymptomatic plaques also had focal areas of signal drop, suggesting an occult macrophage burden. If validated by larger studies, USPIO may be a useful dual contrast agent able to improve risk stratification of patients with carotid stenosis and inform selection for intervention.

Radiation exposure during endovascular aneurysm repair.

BACKGROUND: Endovascular stent-grafting is an established option for the repair of abdominal aortic aneurysm (AAA) that can involve prolonged manipulation under radiological control. The aim was to determine the average radiation exposure sustained during endovascular aneurysm repair (EVAR) and the first year of postoperative surveillance. METHODS: Prospective radiation dose data were recorded and used to calculate dose area product (DAP) values for 96 patients undergoing EVAR. The DAP data were then used to determine the entrance skin dose (ESD), an indicator of potential skin damage, and the effective dose, an indicator of long-term cancer risk, for each patient. RESULTS: The median ESD during EVAR was 0.85 (interquartile range 0.51-3.74) Gy. The threshold for possible radiation-induced skin damage of 2 Gy was exceeded in 29 per cent of procedures. The effective dose of radiation in the first year following EVAR was 79 mSv. CONCLUSION: Radiation doses administered during EVAR were higher than previously thought, with a potential risk of radiation-induced skin damage and later malignancy.

Assessment of pre-operative delays in the management of elective abdominal aortic aneurysms.

INTRODUCTION: Successful endovascular aneurysm repair (EVAR) requires detailed pre-operative imaging to allow device planning. This process may delay surgery and some aneurysms may rupture prior to intervention. The aim of this study was to quantify these delays. PATIENTS AND METHODS: Data were collected prospectively on all patients presenting with non-ruptured abdominal aortic aneurysms (AAAs) between January 2003 and October 2005. The delay between referral, the first out-patient visit, CT-scan, follow-up appointment and surgery were quantified in all patients and compared between two groups undergoing open repair and EVAR. RESULTS: A total of 146 patients underwent AAA repair during the study (48 EVAR versus 98 open repair). There was no significant differences in the wait for CT scans between the groups (median 42 days for EVAR versus 47 days for open repairs [P = 0.48]) or the median interval between decision to operate and surgery (56 days versus 42 days [P = 0.075]). However, the median delay between referral and surgery was significantly longer in those patients undergoing EVAR at 129 days versus 77 days for open repair (P = 0.02). CONCLUSIONS: Patients presenting electively with AAAs experienced significant delay from referral to surgery. This delay was significantly greater in those patients undergoing endovascular repair. Inevitably, some patients will rupture whilst waiting and strategies aimed at reducing delay should be pursued.

Characterisation of carotid atheroma in symptomatic and asymptomatic patients using high resolution MRI.

BACKGROUND AND PURPOSE: To prospectively evaluate differences in carotid plaque characteristics in symptomatic and asymptomatic patients using high resolution MRI. METHODS: 20 symptomatic and 20 asymptomatic patients, with at least 50% carotid stenosis as determined by Doppler ultrasound, underwent preoperative in vivo multispectral MRI of the carotid arteries. Studies were analysed both qualitatively and quantitatively in a randomised manner by two experienced readers in consensus, blinded to clinical status, and plaques were classified according to the modified American Heart Association (AHA) criteria. RESULTS: After exclusion of poor quality images, 109 MRI sections in 18 symptomatic and 19 asymptomatic patients were available for analysis. There were no significant differences in mean luminal stenosis severity (72.9% vs 67.6%; p = 0.09) or plaque burden (median plaque areas 50 mm(2) vs 50 mm(2); p = 0.858) between the symptomatic and asymptomatic groups. However, symptomatic lesions had a higher incidence of ruptured fibrous caps (36.5% vs 8.7%; p = 0.004), haemorrhage or thrombus (46.5% vs 14.0%; p<0.001), large necrotic lipid cores (63.8% vs 28.0%; p = 0.002) and complicated type VI AHA lesions (61.5% vs 28.1%; p = 0.001) compared with asymptomatic lesions. The MRI findings of plaque haemorrhage or thrombus had an odds ratio of 5.25 (95% CI 2.08 to 13.24) while thin or ruptured fibrous cap (as opposed to a thick fibrous cap) had an odds ratio of 7.94 (95% CI 2.93 to 21.51) for prediction of symptomatic clinical status. CONCLUSIONS: There are significant differences in plaque characteristics between symptomatic and asymptomatic carotid atheroma and these can be detected in vivo by high resolution MRI.

Perioperative fluid management: prospective audit.

BACKGROUND: Postoperative fluid management is a core surgical skill but there are few data regarding current fluid management practice and the incidence of potential fluid-related complications in general surgical units. We conducted a prospective audit of postoperative fluid management and fluid-related complications in a consecutive cohort of patients undergoing midline laparotomy. METHODS: Over a 6-month period, the peri-operative fluid management of 106 consecutive patients was prospectively audited. Serum electrolyte data, fluid balance data, co-morbidities, operative and anaesthetic variables and quantities of fluid and electrolytes prescribed were recorded. The development of fluid-related and other complications was noted. RESULTS: There were no correlations between routinely available fluid balance parameters and the quantities of fluid and electrolytes prescribed, suggesting that doctors do not consult fluid balance data when prescribing. Fifty-seven patients (54%) developed at least one fluid-related complication. These patients received significantly greater volumes of fluid and sodium each day postoperatively. They had higher rates of other non-fluid-related complications and death. They had a longer hospital stay. In a multivariate model, mean daily fluid load predicted the development of fluid-related complications. CONCLUSION: Fluid prescription practice in general surgical units is sub-optimal, resulting in avoidable iatrogenic complications. Involvement of senior staff, education and possibly the introduction of prescribing protocols may improve the situation.

Correlation of carotid atheromatous plaque inflammation with biomechanical stress: utility of USPIO enhanced MR imaging and finite element analysis.

OBJECTIVE: The aim of this study was to explore whether there is a relationship between the degree of MR-defined inflammation using ultra small super-paramagnetic iron oxide (USPIO) particles, and biomechanical stress using finite element analysis (FEA) techniques, in carotid atheromatous plaques. METHODS AND RESULTS: 18 patients with angiographically proven carotid stenoses underwent multi-sequence MR imaging before and 36 h after USPIO infusion. T(2)(*) weighted images were manually segmented into quadrants and the signal change in each quadrant normalised to adjacent muscle was calculated after USPIO administration. Plaque geometry was obtained from the rest of the multi-sequence dataset and used within a FEA model to predict maximal stress concentration within each slice. Subsequently, a new statistical model was developed to explicitly investigate the form of the relationship between biomechanical stress and signal change. The Spearman's rank correlation coefficient for USPIO enhanced signal change and maximal biomechanical stress was -0.60 (p=0.009). CONCLUSIONS: There is an association between biomechanical stress and USPIO enhanced MR-defined inflammation within carotid atheroma, both known risk factors for plaque vulnerability. This underlines the complex interaction between physiological processes and biomechanical mechanisms in the development of carotid atheroma. However, this is preliminary data that will need validation in a larger cohort of patients.

Perioperative myocardial injury after elective open abdominal aortic aneurysm repair predicts outcome.

OBJECTIVE: Myocardial injury, detected by rises in cardiac troponin I (TnI), is common and associated with decreased survival following open AAA surgery. We examined the relationship between perioperative myocardial injury and postoperative outcome. DESIGN: Observational Cohort Study. METHODS: Forty-three consecutive patients who underwent elective open AAA repair were screened for perioperative myocardial injury or infarction using serial TnI measurements (taken on days 1, 3, and 7), ECG and clinical assessment. The primary outcome was survival free of cardiac failure, or myocardial infarction (MI) at follow-up. RESULTS: Twenty (47%) of the 43 patients had a TnI elevation. Of these, 11 (26%) patients met the criteria for MI. At a mean (+/-SD) follow-up of 1.5+/-0.8 years, 12 (28%) subjects had experienced at least one endpoint event. Survival free of cardiac failure or MI was 55% in patients who had TnI rises compared to 87% in those without (P=0.02). Logistic regression revealed that TnI elevation was an independent predictor of outcome with an odds ratio of 5.4 (95% CI 1.2-2.4, P=0.03). CONCLUSION: Perioperative myocardial injury after elective open AAA repair predicts outcome after surgery. Routine TnI measurement should be considered in all patients, especially in those with high cardiovascular risk.

Doppler-guided intra-operative fluid management during major abdominal surgery: systematic review and meta-analysis.

BACKGROUND: Peri-operative fluid therapy is a controversial area with few randomised trials to guide practice. Recently, a number of trials have suggested that intra-operative therapy guided by oesophageal Doppler acquired haemodynamic variables may improve postoperative outcome. METHODS: Abstract databases and conference proceedings were searched to identify randomised controlled trials comparing Doppler-guided intra-operative fluid management to standard practice in patients undergoing major abdominal surgery. Pooled odds ratios (POR) and weighted mean differences (WMD) were calculated for categorical and continuous outcomes respectively. RESULTS: Four trials, comprising 393 patients, were identified. Use of an oesophageal Doppler-guided fluid management algorithm resulted in fewer postoperative complications (POR 0.32; 95% CI: 0.19-0.52; p < 0.0001) and shorter hospital stays (WMD 1.68 days; 95% CI: 2.39-0.98; p < 0.0001). There were no significant differences in the quantities of intra-operative fluids administered although there was some evidence of heterogeneity with respect to this outcome. CONCLUSION: Oesophageal Doppler-guided fluid management may improve outcome following major intra-abdominal surgery. However, comparison with fluid restriction strategies, including a cost-effectiveness analysis are required.

Five day antibiotic prophylaxis for major lower limb amputation reduces wound infection rates and the length of in-hospital stay.

OBJECTIVE: To compare wound infection, revision rates and hospital stay after major lower limb amputation between patients receiving 24 hours versus 5 days of prophylactic antibiotics. METHODS: The outcomes of a consecutive series of 40 major lower limb amputations in patients receiving a short 24-hour course of combined prophylactic antibiotics (flucloxacillin/vancomycin + gentamicin/ciproxin + metronidazole) were retrospectively analysed. Following this a further consecutive group of 40 major lower limb amputations were studied prospectively following the institution of a 5-day combined regime using the same antibiotics. RESULTS: The 2 groups of patients were similar in terms of demographics, vascular risk factors and level of amputation. The 5-day antibiotic regime led to a significant reduction in wound infection rates (5% vs. 22.5%, P=0.023) and a reduced length of hospital stay (22 vs. 34 days, P=0.001). Revision rates were lower (2.5% vs. 10%) but did not reach statistical significance (P=0.36). More patients in the prospective 5-day antibiotic series were operated on by the vascular trainee. (77.5% vs. 55% P=0.033). CONCLUSIONS: This data supports the use of a prolonged 5-day course of combined antibiotics after major lower limb amputation. This appears to reduce stump infection rates leading to shorter in-hospital stay.

Cardioprotection by remote ischaemic preconditioning.

Perioperative myocardial infarction is a leading cause of morbidity and mortality after major non-cardiac surgery. Pharmacological agents such as beta-blockers may reduce the risk but are associated with side-effects and may be contra-indicated in some patients. Basic scientific experiments and preliminary clinical trials in humans suggest that remote ischaemic preconditioning (RIPC), where brief ischaemia in one tissue confers resistance to subsequent sustained ischaemic insults in another tissue, may provide a simple, cost-effective means of reducing the risk of perioperative myocardial ischaemia. The Medline and Pubmed databases were searched for articles concerning RIPC. The mechanism may be humoral, neural, or a combination of both, and involves adenosine, opioids, bradykinins, protein kinase C, and K-ATP channels, although the precise end-effector remains unclear. Small randomized trials in humans undergoing major surgery suggest that RIPC induced by brief lower limb ischaemia significantly reduces myocardial injury. It may also reduce other ischaemic complications of surgery and anaesthesia. Small studies provide some evidence that RIPC could reduce myocardial injury and other ischaemic complications of surgery. However, large-scale clinical trials to assess the effect of RIPC on mortality and morbidity are required before RIPC can be recommended for routine clinical use.

Comparison of risk-scoring methods in predicting the immediate outcome after elective open abdominal aortic aneurysm surgery.

BACKGROUND & OBJECTIVES: The aim of this study was to apply three simple risk - scoring systems to prospectively collected data on all elective open Abdominal Aortic Aneurysm (AAA) operations in the Cambridge Academic Vascular Unit over a 6 - year period (January 1998 to January 2004), to compare their predictive values and to evaluate their validity with respect to prediction of mortality and post-operative complications. METHODS: 204 patients underwent elective open infra-renal AAA repair. Data were prospectively collected and risk assessment scores were calculated for mortality and morbidity according to the Glasgow Aneurysm Score (GAS), VBHOM (Vascular Biochemistry and Haematology Outcome Models) and Estimation of Physiologic Ability and Surgical Stress (E-PASS). RESULTS: The mortality rate was 6.3% (13/204) and 59% (121/204) experienced a post-operative complication (30-day outcome). For GAS, VBHOM and E-PASS the receiver operating characteristics (ROC) curve analysis for prediction of in-hospital mortality showed area under the curve (AUC) of 0.84 (95% confidence interval [CI], 0.76 to 0.92; p<0.0001), 0.82 (95% CI, 0.68 to 0.95; p=0.0001) and 0.92 (95% CI, 0.87 to 0.97; p<0.0001) respectively. There were also significant correlations between post-operative complications and length of hospital stay and each of the three scores, but the correlation was substantially higher in the case of E-PASS. CONCLUSIONS: All three scoring systems accurately predicted the risk of mortality and morbidity in patients undergoing elective open AAA repair. Among these, E-PASS seemed to be the most accurate predictor in this patient population.

POSSUM models in open abdominal aortic aneurysm surgery.

OBJECTIVES: This study evaluated the Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (POSSUM), Portsmouth (P) POSSUM and Vascular (V) POSSUM. The primary aim was to assess the validity of these scoring systems in a population of patients undergoing elective and emergency open AAA repair. The secondary intention was in the event that these equations did not fit all patients with an aneurysm; a new model would be developed and tested using logistic regression from the local data (Cambridge POSSUM). METHODS: POSSUM data items were collected prospectively in a group of 452 patients undergoing elective and emergency open AAA repair over an eight-year period. The operative mortality rates were compared with those predicted by POSSUM, P-POSSUM, V-POSSUM and Cambridge POSSUM. RESULTS: All models except V-POSSUM (physiology only) showed significant lack of fit when predicting mortality after open AAA surgery. It was found that the locally generated single unified model (Cambridge POSSUM) could successfully describe both elective and ruptured AAA mortality with good discrimination (chi(2)=9.24, 7 d.f., p=0.236, c-index=0.880). CONCLUSIONS: POSSUM, V-POSSUM and P-POSSUM may not be robust tools for comparing mortality between populations undergoing elective and emergency open AAA repair as once thought. The development and successful validation of Cambridge POSSUM provides a unified model to describe both elective and emergency AAAs together and should be validated in other geographical settings.