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OBJECTIVE: To assess the incidence and outcome of graft limb occlusions after endovascular aortic repair (EVAR) of abdominal aortic aneurysm (AAA) in a high volume single centre. To quantify iliac artery tortuosity in patients with AAA and correlate this with limb occlusion.DESIGN: Data were collected consecutively and prospectively, and analyzed retrospectively.MATERIALS: Patients treated with Zenith bifurcated stent grafts from January 2000 to December 2010 at a tertiary referral vascular unit were analyzed. Routine regular office follow-up with computed tomography angiography (CTA) and, subsequently, duplex ultrasound imaging was performed. Patients with limb occlusions were identified. For each index patient, two controls were obtained, one immediately preceding and one following the index patient in the consecutive cohort of EVAR patients.METHODS: Demographics and CTA data on limb graft occlusions were recorded and compared with a defined control group. Three different indices were used to describe the tortuosity of the iliac vessels based on preoperative CTA: pelvic artery index of tortuosity (PAI), common iliac artery index of tortuosity (CAI), and a visual description of vessel tortuosity - the double iliac sign (DIS). Demographic data and indices were correlated for later occurring limb occlusion.RESULTS: 504 patients underwent EVAR and 18 patients experienced graft limb occlusion during a median follow-up of 28 months (range 0-133). Primary graft patency was 97% at 1 year and 96% at 3 years. Logistic regression showed that iliac artery tortuosity (DIS) (p = .001) and body mass index (p = .007) had a significant impact on graft patency.CONCLUSION: A tortuous vessel on the preoperative CTA is associated with an increased risk of limb occlusion after EVAR. Adjunctive stenting of iliac segments deemed at risk is suggested, which is achieved without compromise of the aneurysm repair.

Objective Increased glucocorticoid metabolite excretion and enhanced expression and activity of 11-hydroxysteroid dehydrogenase type 1 in adipose tissue are closely correlated with obesity and its detrimental consequences. Weight loss ameliorates the latter. The aim of this study was to explore whether increased glucocorticoid exposure in obesity is improved with substantial weight loss and thus is a consequence rather than a cause of obesity. Design and patients A prospective cohort study in 31 women. Measurements 11-HSD type 1 expression and activity, urinary glucocorticoid metabolite excretion, body composition including regional adipose tissue depots and insulin resistance by HOMA-IR before and 2years after gastric bypass surgery. Results After weight loss, excretion of cortisol and cortisone metabolites decreased. Both cortisol and cortisone metabolite excretion correlated with central obesity, where the intraabdominal fat depot showed the strongest association. Cortisol metabolites correlated with 11-HSD type 1 activity in abdominal subcutaneous adipose tissue. The ratio of cortisol to cortisone metabolites [(5-tetrahydrocortisol (5THF)+tetrahydrocortisol (THF)+-cortol)/(tetrahydrocortisone (THE)+-cortolone)] and the ratio of 5-THF/THF both decreased after stable weight loss, reflecting a downregulation of the net activities of 11-HSD type 1 and 5-reductase. Conclusion Long-term weight loss in women is not only followed by reduced glucocorticoid production, but also favourably decreases the global and tissue-specific activity of the cortisol-activating enzyme 11 -HSD type 1, possibly contributing to the health benefits of bariatric surgery.

Cigarette smoking is the leading self-inflicted risk factor for cardiovascular diseases; it causes arterial stiffening with serious sequelea including atherosclerosis and abdominal aortic aneurysms. This work presents a new interpretation of arterial stiffening caused by smoking based on data published for rat pulmonary arteries. A structurally motivated "four fiber family" constitutive relation was used to fit the available biaxial data and associated best-fit values of material parameters were estimated using multivariate nonlinear regression. Results suggested that arterial stiffening caused by smoking was reflected by consistent increase in an elastin-associated parameter and moreover by marked increase in the collagen-associated parameters. That is, we suggest that arterial stiffening due to cigarette smoking appears to be isotropic, which may allow simpler phenomenological models to capture these effects using a single stiffening parameter similar to the approach in isotropic continuum damage mechanics. There is a pressing need, however, for more detailed histological information coupled with more complete biaxial mechanical data for a broader range of systemic arteries.

Objectives To study the construct validity and reliability of a novel endovascular global rating scale, Structured Assessment of endoVascular Expertise (SAVE). Design A Clinical, experimental study. Materials Twenty physicians with endovascular experiences ranging from complete novices to highly experienced operators performed a video-recorded simulated contra-lateral iliac-artery-stenting procedure. The virtual-patient case was a novel technically challenging procedure presenting the distal arteries below the knee. Methods Three experts assessed the performances blinded to operator identity. Validity was analysed by correlating experience with performance results. Reliability was analysed according to generalisability theory. Results The mean score on the 29 items of the SAVE scale correlated well with clinical experience (R = 0.84, P < 0.01) and was found discriminative even among the more experienced participants having performed up to 500 endovascular procedures in total. Only the most experienced participants (>5000 procedures) obtained maximum scores. The inter-rater reliability was high (G = 0.94 and G = 0.95). The procedure time (median 69 min, range 32–86) correlated moderately with clinical experience (R = -0.53, P < 0.05), whereas the fluoroscopy time and amount of contrast fluid did not correlate. Conclusions The construct validity and reliability of assessment with the SAVE scale was high when applied to performances in a simulation setting with advanced realism. No ceiling effect was present in the assessment situation.

AIM: The aim of this study was to estimate the incidence of the post-implantation syndrome/systemic inflammatory response syndrome (SIRS) after endovascular aortic repair. METHODS: All patients, undergoing elective primary endovascular repair of an asymptomatic infrarenal abdominal aortic aneurysm during 2007, were retrospectively evaluated for SIRS within the first 5 postoperative days. The only exclusion-criteria were missing data. SIRS was assessed using the criteria defined by the American College of Chest Physicians and Society of Critical Care Medicine Consensus Conference Committee. RESULTS: Sixty-six patients were included, 40 (60%) met the SIRS criteria within the first 5 postoperative days (95% of the 40 patients met the criteria within 3 days). We found no significant differences between the SIRS and the non-SIRS group in baseline characteristics or other data including volume of the contrast media used, type of groin access, adjunctive procedures and duration of surgery. In total, 11 (28%) patients in the SIRS group and 4 (15%) patients in the non-SIRS group underwent re-interventions. Median follow-up period was 26 (range 20-32) months. Thirty-day mortality did not differ in the groups (3% in the SIRS group vs. none in the non-SIRS group). CONCLUSION: The high incidence of SIRS after EVAR is unexpected considering the minimally invasive procedure. Further studies on the cause of this response and measures to attenuate the response seem appropriate.

The structural integrity of the abdominal aorta is maintained by elastin, collagen, and vascular smooth muscle cells. Changes with age in the structure can lead to develop-ment of aneurysms. This paper presents initial work to capture these changes in a finite element model (FEM) of a structural-ly-motivated anisotropic constitutive relation for the “four fiber family” arterial model. First a 2D implementation is used for benchmarking the FEM implementation to fitted biaxial stress-strain data obtained experimentally from four different groups of persons; 19-29 years, 30-60 years, 61-79 years and abdominal aortic aneurysm (AAA) patients. Next the constitu-tive model is implemented in an anisotropic 3D FEM formula-tion for future simulation of intact aortic geometries. The 2D simulations of the biaxial test experiment show good agree-ment with experimental data with a standard deviation below 0.5% in all cases. The maximum axial and hoop stress in the group of AAA patients was 94.9 kPa (±0.283 kPa) and 94.3 kPa (±0.224 kPa) at maximum stretch ratios of 1.043 and 1.037, respectively. In the 3D simulations, the maximum stress is also found to occur in the AAA patient group, with the highest stress in the circumferential direction (275 kPa). Comparison with an already published isotropic model indicates that the latter underestimates the peak stress significantly. Based on these results it is concluded that the four fiber family model has been successfully implemented into a 3D anisotropic finite element model and that this model can provide more accurate insight into the stress conditions in aortic aneurysms.

Cigarette smoking is the leading self-inflicted risk factor for cardiovascular diseases; it causes arterial stiffening with serious sequelea including atherosclerosis and abdominal aortic aneurysms. This work presents a new interpretation of arterial stiffening caused by smoking based on data published for rat pulmonary arteries. A structurally motivated ‘‘four fiber family’’ constitutive relation was used to fit the available biaxial data and associated best-fit values of material parameters were estimated using multivariate nonlinear regression. Results suggested that arterial stiffening caused by smoking was reflected by consistent increase in an elastin-associated parameter and moreover by marked increase in the collagen-associated parameters. That is, we suggest that arterial stiffening due to cigarette smoking appears to be isotropic, which may allow simpler phenomenological models to capture these effects using a single stiffening parameter similar to the approach in isotropic continuum damage mechanics. There is a pressing need, however, for more detailed histological information coupled with more complete biaxial mechanical data for a broader range of systemic arteries.

To explore what characterises the development of endovascular expertise and to construct a novel global assessment instrument.

Udgivelsesdato: 2009-Aug, Endovascular aneurysm repair (EVAR) represents one of the greatest advances in vascular surgery over the past 50 years. In contrast to conventional aneurysm repair, EVAR requires accurate preoperative imaging and stringent postoperative surveillance. Duplex ultrasound (DUS), transesophageal echocardiography, intravascular ultrasound, computed tomography (CT) and magnetic resonance (MR), each provide useful information for patient selection, choice of endograft type and surveillance. Today most interventionists and surgeons will rely on CT or MR to assess aortic morphology, evaluate access artery patency and locate side branch orifices. However, recent developments in cross-sectional imaging, including advanced image postprocessing, multi-modality image fusion and new contrast agents have resulted in improved spatial resolution for preoperative planning. Advanced reconstruction algorithms, like dynamic CTA and MRA, provide valuable information on dynamic changes in aneurysm morphology that might have an important impact on endograft selection. During follow-up, imaging of the graft and aneurysm is of utmost importance to identify patients in need of secondary intervention. This has led to rigorous follow-up protocols including duplex ultrasound and regular CT examinations. The use of these intense follow-up protocols has recently been questioned because of high radiation dose and the frequent use of nephrotoxic contrast agents. New imaging modalities like contrast enhanced DUS, dynamic MR and dual-source CT could reduce radiation dose and obviate the need for nephrotoxic contrast. Up-to-date knowledge of non-invasive vascular imaging and image processing is crucial for EVAR planning and is essential for the development of follow-up programs involving reduced risk of harmful side effects.

Udgivelsesdato: 2009-Feb, The aim of this study was to validate a recently proposed MRI-based T(1)-mapping method for analysis of whole-body adipose tissue (AT) using an established CT protocol as reference and to include results from dual energy X-ray absorptiometry (DEXA). 10 subjects, drawn from the Swedish Obese Subjects Sibling-pairs study, were examined using CT, MRI and DEXA. The CT analysis was based on 28 imaged slices. T(1) maps were calculated using contiguous MRI data from two different gradient echo sequences acquired using different flip angles. CT and MRI comparison was performed slice-wise and for the whole-body region. Fat weights were compared between all three modalities. Strong correlations (r > or = 0.977, p<0.0001) were found between MRI and CT whole-body and AT volumes. MRI visceral AT volume was underestimated by 0.79 +/- 0.75 l (p = 0.005), but total AT was not significantly different from that estimated by CT (MRI - CT = -0.61+/-1.17 l; p = 0.114). DEXA underestimated fat weights by 5.23 +/- 1.71 kg (p = 0.005) compared with CT. MRI underestimated whole-body volume by 2.03 +/- 1.61 l (p = 0.005) compared with CT. Weights estimated either by CT or by DEXA were not significantly different from weights measured using scales. In conclusion, strong correlations were found between whole-body AT results from CT, MRI-based T(1) mapping and DEXA. If the differences between the results from T(1)-mapping and CT-based analysis are accepted, the T(1)-mapping method allows fully automated post-processing of whole-body MRI data, allowing longitudinal whole-body studies that are also applicable for children and adolescents.

Udgivelsesdato: 2009-Jan, BACKGROUND: Static vascular filling pressures suffer from poor predictive power in identifying the volume-responsive heart. The use of dynamic arterial pressure variables, including pulse pressure variation (PPV) has instead been suggested to guide volume therapy. The aim of the present study was to evaluate the performance of several clinically applicable haemodynamic parameters to predict volume responsiveness in a pig closed chest model of acute left ventricular myocardial infarction. METHODS: Fifteen anaesthetized, mechanically ventilated pigs were studied following acute left myocardial infarction by temporary coronary occlusion. Animals were instrumented to monitor central venous (CVP) and pulmonary artery occlusion (PAOP) pressures and arterial systolic variations (SPV) and PPV. Cardiac output (CO) was measured using the pulmonary artery catheter and by using the PiCCO monitor also giving stroke volume variation (SVV). Variations in the velocity time integral by pulsed-wave Doppler echocardiography were determined in the left (DeltaVTI(LV)) and right (DeltaVTI(RV)) ventricular outflow tracts. Consecutive boluses of 4 ml/kg hydroxyethyl starch were administered and volume responsiveness was defined as a 10% increase in CO. RESULTS: Receiver-operator characteristics (ROC) demonstrated the largest area under the curve for DeltaVTI(RV) [0.81 (0.70-0.93)] followed by PPV [0.76 (0.64-0.88)] [mean (and 95% CI)]. SPV, DeltaVTI(LV) and SVV did not change significantly during volume loading. CVP and PAOP increased but did not demonstrate significant ROC. CONCLUSION: PPV may be used to predict the response to volume administration in the setting of acute left ventricular myocardial infarction.

AIM: Endovascular repair of complicated type B dissections has evolved as a promising alternative to open repair. Previous studies have indicated that continued false lumen flow is a predictor of continued aortic dilatation and risk of rupture during follow-up. This multicenter study was conducted to analyze the postoperative changes of the false lumen after endografting of complicated type B dissections. METHODS: All patients treated with endovascular stent grafts for thoracic type B dissections at 5 major Vascular Centers in Sweden were identified through local databases. Review of charts and all available pre- and postoperative CT scans were performed to identify demographics, indications for repair as well as postoperative changes of the aorta and false lumen. RESULTS: A total of 129 patients treated for type B dissections between 1994 and December 2005 were identified. Median radiological follow-up was 14 months. Fourteen patients died perioperatively leaving 115 patients available for analysis. Seventy-four of these had CT imaging of sufficient quality for morphological analysis. The vast majority of acute patients were treated for rupture or end-organ ischemia whereas most chronic patients were treated for asymptomatic aneurysms. In 80% of patients, the false lumen thrombosed along the stent graft but it remained perfused distal to the stent graft fixation in 50% of patients. Only 5% of patients presented with aortic enlargement of the stent grafted area when adequate proximal sealing was achieved. The distal, uncovered aorta displayed expansion in 16% of patients. CONCLUSIONS: The stent grafted thoracic aorta after type B dissection appears to be stabilized by covering the primary entry site with a stent graft in the majority of both acute and chronic dissections. The uncovered portion of the aorta distal to the stent graft, however, remains at risk of continuous dilatation. Stent grafting for complicated type B thoracic dissections seems to be a treatment o