| 1. |
- Bogdanovic, Marko, et al.
(författare)
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Limb Graft Occlusion Following Endovascular Aneurysm Repair for Infrarenal Abdominal Aortic Aneurysm with the Zenith Alpha, Excluder, and Endurant Devices : a Multicentre Cohort Study
- 2021
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier. - 1078-5884 .- 1532-2165. ; 62:4, s. 532-539
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Limb graft occlusion (LGO) is a serious complication after endovascular aneurysm repair (EVAR) and while device development enables treatment of increasingly complex aortic anatomy, little is known about how endograft type affects the risk of occlusion. This observational study aimed to explore the incidence of LGO after EVAR for three major endograft systems.Methods: All patients with standard EVAR as the primary intervention for infrarenal abdominal aortic aneurysm (AAA), between January 2012 and December 2018, at five Swedish vascular surgery centres, were included in this multicentre retrospective cohort study. LGO was defined as a total limb occlusion regardless of symptoms, or a treated significant stenosis. A nested case control (NCC) design with incidence density sampling of 1:3 was used for analysis of potential per-operative and morphological risk factors. Conditional logistic regression was used to estimate multivariable odds ratios (OR) with 95% confidence intervals (CI)Results: A total of 924 patients were included. The majority were male (84%), the mean age was 76 years (+/- 7.5 SD), and median AAA diameter was 59 mm (IQR 55, 67). Patients were treated with Zenith Alpha (n = 315, ZISL limbs), Excluder (n = 152, PLC/PXC limbs), and Endurant (n = 457, ETLW/ ETEW limbs). During median follow up of 37 months (IQR 21, 62), 55 occlusions occurred (5.9%); 39 with Zenith Alpha (12.4%), one with Excluder (0.7%), and 15 with Endurant (3.3%). In the NCC analysis, the Zenith Alpha device (OR 5.31, 95% CI 1.97 - 14.3), external iliac artery (EIA) landing (OR 5.91, 95% CI 1.30 - 26.7), and EIA diameter < 10 mm (OR 4.99, 95% CI 1.46 - 16.9) were associated with an increased risk of LGO.Conclusion: Endograft device type is an independent risk factor for LGO after EVAR. Specifically, the Zenith Alpha demonstrated an increased risk of LGO compared with the Endurant and Excluder devices. In addition, a narrow EIA and landing zone in EIA are also risk factors for LGO.
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| 2. |
- Liljeqvist, Moritz Lindquist, et al.
(författare)
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Gender, smoking, body size, and aneurysm geometry influence the biomechanical rupture risk of abdominal aortic aneurysms as estimated by finite element analysis
- 2017
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Ingår i: Journal of Vascular Surgery. - : Elsevier. - 0741-5214 .- 1097-6809. ; 65:4, s. 1014-1021
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Finite element analysis (FEA) has been suggested to be superior to maximal diameter measurements in predicting rupture of abdominal aortic aneurysms (AAAs). Our objective was to investigate to what extent previously described rupture risk factors were associated with FEA-estimated rupture risk. Methods: One hundred forty-six patients with an asymptomatic AAA of a 40-to 60-mm diameter were retrospectively identified and consecutively included. The patients' computed tomography angiograms were analyzed by FEA without (neutral) and with (specific) input of patient-specific mean arterial pressure (MAP), gender, family history, and age. The maximal wall stress/wall strength ratio was described as a rupture risk equivalent diameter (RRED), which translated this ratio into an average aneurysm diameter of corresponding rupture risk. Results: In multivariate linear regression, RREDneutral increased with female gender (3.7 mm; 95% confidence interval [CI], 0.13-7.3) and correlated with patient height (0.27 mm/cm; 95% CI, 0.11-0.43) and body surface area (BSA, 16 mm/m(2); 95% CI, 8.3-24) and inversely with body mass index (BMI,-0.40 mm/kg m(-2); 95% CI, -0.75 to -0.054) in a wall stress-dependent manner. Wall stress-adjusted RREDneutral was raised if the patient was currently smoking (1.1 mm; 95% CI, 0.21-1.9). Age, MAP, family history, and patient weight were unrelated to RREDneutral. In specific FEA, RREDspecific increased with female gender, MAP, family history positive for AAA, height, and BSA, whereas it was inversely related to BMI. All results were independent of aneurysm diameter. Peak wall stress and RRED correlated with aneurysm diameter and lumen volume. Conclusions: Female gender, current smoking, increased patient height and BSA, and low BMI were found to increase the mechanical rupture risk of AAAs. Previously described rupture risk factors may in part be explained by patient characteristic-dependent variations in aneurysm biomechanics.
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| 3. |
- Liljeqvist, Moritz Lindquist, et al.
(författare)
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Geometric and biomechanical modeling aided by machine learning improves the prediction of growth and rupture of small abdominal aortic aneurysms
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- It remains difficult to predict when which patients with abdominal aortic aneurysm (AAA) will require surgery. The aim was to study the accuracy of geometric and biomechanical analysis of small AAAs to predict reaching the threshold for surgery, diameter growth rate and rupture or symptomatic aneurysm. 189 patients with AAAs of diameters 40-50 mm were included, 161 had undergone two CTAs. Geometric and biomechanical variables were used in prediction modelling. Classifications were evaluated with area under receiver operating characteristic curve (AUC) and regressions with correlation between observed and predicted growth rates. Compared with the baseline clinical diameter, geometric-biomechanical analysis improved prediction of reaching surgical threshold within four years (AUC 0.80 vs 0.85, p = 0.031) and prediction of diameter growth rate (r = 0.17 vs r = 0.38, p = 0.0031), mainly due to the addition of semiautomatic diameter measurements. There was a trend towards increased precision of volume growth rate prediction (r = 0.37 vs r = 0.45, p = 0.081). Lumen diameter and biomechanical indices were the only variables that could predict future rupture or symptomatic AAA (AUCs 0.65-0.67). Enhanced precision of diameter measurements improves the prediction of reaching the surgical threshold and diameter growth rate, while lumen diameter and biomechanical analysis predicts rupture or symptomatic AAA.
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| 4. |
- Mattila, Robert, et al.
(författare)
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A Markov Decision Process Model to Guide Treatment of Abdominal Aortic Aneurysms
- 2016
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Ingår i: 2016 IEEE CONFERENCE ON CONTROL APPLICATIONS (CCA). - : IEEE. ; , s. 436-441
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Konferensbidrag (refereegranskat)abstract
- An abdominal aortic aneurysm (AAA) is an enlargement of the abdominal aorta which, if left untreated, can progressively widen and may rupture with fatal consequences. In this paper, we determine an optimal treatment policy using Markov decision process modeling. The policy is optimal with respect to the number of quality adjusted life-years (QALYs) that are expected to be accumulated during the remaining life of a patient. The new policy takes into account factors that are ignored by the current clinical policy (e.g. the life-expectancy and the age-dependent surgical mortality). The resulting optimal policy is structurally different from the current policy. In particular, the policy suggests that young patients with small aneurysms should undergo surgery. The robustness of the policy structure is demonstrated using simulations. A gain in the number of expected QALYs is shown, which indicates a possibility of improved care for patients with AAAs.
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| 5. |
- Siika, Antti, et al.
(författare)
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A large proportion of patients with small ruptured abdominal aortic aneurysms are women and have chronic obstructive pulmonary disease
- 2019
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Ingår i: PLOS ONE. - : Public Library Science. - 1932-6203. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- Objective In a population-based cohort of ruptured abdominal aortic aneurysms (rAAAs), our aim was to investigate clinical, morphological and biomechanical features in patients with small rAAAs. Methods All patients admitted to an emergency department in Stockholm and Gotland, a region with a population of 2.1 million, between 2009-2013 with a CT-verified rupture (n = 192) were included, and morphological measurements were performed. Patients with small rAAAs, maximal diameter (Dmax) <= 60 mm were selected (n = 27), and matched 2: 1 by Dmax, sex and age to intact AAA (iAAAs). For these patients, morphology including volume and finite element analysis-derived biomechanics were assessed. Results The mean Dmax for all rAAAs was 80.8 mm (SD = 18.9 mm), women had smaller Dmax at rupture (73.4 +/- 18.4 mm vs 83.1 +/- 18.5 mm, p = 0.003), and smaller neck and iliac diameters compared to men. Aortic size index (ASI) was similar between men and women (4.1 +/- 3.1 cm/m(2) vs 3.8 +/- 1.0 cm/m(2)). Fourteen percent of all patients ruptured at Dmax <= 60 mm, and a higher proportion of women compared to men ruptured at Dmax <= 60 mm: 27% (12/45) vs. 10% (15/147), p = 0.005. Also, a higher proportion of patients with a chronic obstructive pulmonary disease ruptured at Dmax <= 60 mm (34.6% vs 14.6%, p = 0.026). Supra-renal aortic size index (14.0, IQR 13.3-15.3 vs 12.8, IQR = 11.4-14.0) and peak wall rupture index (PWRI, 0.35 +/- 0.08 vs 0.43 +/- 0.11, p = 0.016) were higher for small rAAAs compared to matched iAAAs. Aortic size index, peak wall stress and aneurysm volume did not differ. Conclusion More than one tenth of ruptures occur at smaller diameters, women continuously suffer an even higher risk of presenting with smaller diameters, and this must be considered in surveillance programs. The increased supra-renal aortic size index and PWRI are potential markers for rupture risk, and patients under surveillance with these markers may benefit from increased attention, and potentially from timely repair.
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| 6. |
- Siika, Antti, et al.
(författare)
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Aortic Lumen Area Is Increased in Ruptured Abdominal Aortic Aneurysms and Correlates to Biomechanical Rupture Risk
- 2018
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Ingår i: Journal of Endovascular Therapy. - : Sage Publications. - 1526-6028 .- 1545-1550. ; 25:6, s. 750-756
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate how 2-dimensional geometric parameters differ between ruptured and asymptomatic abdominal aortic aneurysms (AAAs) and provide a biomechanical explanation for the findings. Methods: The computed tomography angiography (CTA) scans of 30 patients (mean age 77 +/- 10 years; 23 men) with ruptured AAAs and 60 patients (mean age 76 +/- 8 years; 46 men) with asymptomatic AAAs were used to measure maximum sac diameter along the center lumen line, the cross-sectional lumen area, the total vessel area, the intraluminal thrombus (ILT) area, and corresponding volumes. The CTA data were segmented to create 3-dimensional patient-specific models for finite element analysis to compute peak wall stress (PWS) and the peak wall rupture index (PWRI). To reduce confounding from the maximum diameter, 2 diameter-matched groups were selected from the initial patient cohorts: 28 ruptured AAAs and another with 15 intact AAAs (diameters 74 +/- 12 vs 73 +/- 11, p=0.67). A multivariate model including the maximum diameter, the lumen area, and the ILT area of the 60 intact aneurysms was employed to predict biomechanical rupture risk parameters. Results: In the diameter-matched subgroup comparison, ruptured AAAs had a significantly larger cross-sectional lumen area (1954 +/- 1254 vs 1120 +/- 623 mm(2), p=0.023) and lower ILT area ratio (55 +/- 24 vs 68 +/- 24, p=0.037). The ILT area (2836 +/- 1462 vs 2385 +/- 1364 mm(2), p=0.282) and the total vessel area (3956 +/- 1170 vs 4338 +/- 1388 mm(2), p=0.384) did not differ statistically between ruptured and intact aneurysms. The PWRI was increased in ruptured AAAs (0.80 vs 0.48, p<0.001), but the PWS was similar (249 vs 284 kPa, p=0.194). In multivariate regression analysis, lumen area was significantly positively associated with both PWS (p<0.001) and PWRI (p<0.01). The ILT area was also significantly positively associated with PWS (p<0.001) but only weakly with PWRI (p<0.01). The lumen area conferred a higher risk increase in both PWS and PWRI when compared with the ILT area. Conclusion: The lumen area is increased in ruptured AAAs compared to diameter-matched asymptomatic AAAs. Furthermore, this finding may in part be explained by a relationship with biomechanical rupture risk parameters, in which lumen area, irrespective of maximum diameter, increases PWS and PWRI. These observations thus suggest a possible method to improve prediction of rupture risk in AAAs by measuring the lumen area without the use of computational modeling.
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| 7. |
- Siika, Antti
(författare)
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Biomechanical and morphological aspects of abdominal aortic aneurysm growth and rupture
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abdominal aortic aneurysms (AAAs) are dilatations of the abdominal aorta that pose a risk of rupture. The only effective treatment is intervention prior to rupture, but this is also associated with mortality and morbidity. It is therefore important to weigh the risks of intervention with the potential benefit. Current treatment guidelines recommend using the maximal aneurysm diameter (Dmax) as the indicator for rupture risk, and rec- ommend considering intervention in men with AAAs > 55 mm, and >50 mm in women. Patients with small AAAs are put in surveillance, and the Dmax is followed until it reaches the threshold. The current policy is relatively efficient on a population-level but lacks specificity for individuals. Some patients rupture before this threshold, and many remain stable despite passing it. Aneurysm growth is often described as erratic, but measure- ments are affected by several levels of uncertainty. Biomechanical assessment, where 3D models of AAAs from computed tomography angiographies (CTAs) are analysed by finite element analysis, may improve risk prediction. In the first study a population-based cohort of 192 patients with ruptured AAAs and CT imaging available at rupture were studied. A significant portion of patients ruptured with AAAs smaller than 60 mm, 10% of men and 27 % of women. When normalizing Dmax for body surface area (so-called aortic size index) there was, however, was not difference between the sexes. In an analysis of small, ruptured AAAs compared to Dmax, age and sex-matched asymptomatic AAAs, peak wall rupture index (PWRI), but not peak wall stress (PWS) was increased in the ruptured AAAs. In the second study, a cohort of 100 patients with at least three computed tomog- raphy examinations were analysed with 3D morphological and biomechanical analysis. The growth pattern of AAAs appeared continuous and conferred well to a linear growth model. The evolution of the different analysed indices, Dmax, aneurysm volume and bio- mechanical stress did, however, not parallel each other. Intraluminal thrombus (ILT) grew faster than the lumen, but lumen volume growth was more closely related to increase in biomechanical stress. In the third study, a cohort of 67 patients with 109 CTA examinations prior to rupture were identified. The relation between biomechanical variables and time-to-rupture was investigated. In small and medium sized AAAs (< 70 mm), PWRI, but not PWS, was associ- ated with time-to-rupture, also when adjusting for potential confounders, aneurysm size and sex. The results further show that women have an approximately two-fold increased hazard ratio for AAA rupture, compared to men, when adjusted for AAA size. In the fourth study lumen area is indicated as a potentially useful rupture risk marker. Ruptured AAAs, compared to Dmax-matched asymptomatic AAAs, have a larger luminal area, and the luminal area is related to biomechanical stress, even when adjusting for an- eurysm size, or ILT area. In conclusion, the results of this thesis indicate areas of potential improvement in the current care of patients with AAAs, explores the 3D growth of AAAs, and strengthens the potential role for biomechanical analysis. These results may in the future have rele- vance for personalizing timing of treatment for patients with AAAs, and the evaluation of pharmacological therapy for AAAs.
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| 8. |
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| 9. |
- Siika, Antti, et al.
(författare)
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Peak wall rupture index is associated with risk of rupture of abdominal aortic aneurysms, independent of size and sex
- 2024
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Ingår i: British Journal of Surgery. - : Oxford University Press. - 0007-1323 .- 1365-2168. ; 111:5
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Tidskriftsartikel (refereegranskat)abstract
- Background: Information on the predictive determinants of abdominal aortic aneurysm rupture from CT angiography are scarce. The aim of this study was to investigate biomechanical parameters in abdominal aortic aneurysms and their association with risk of subsequent rupture. Methods: In this retrospective study, the digital radiological archive was searched for 363 patients with ruptured abdominal aortic aneurysms. All patients who underwent at least one CT angiography examination before aneurysm rupture were included. CT angiography results were analysed to determine maximum aneurysm diameter, aneurysm volume, and biomechanical parameters (peak wall stress and peak wall rupture index). In the primary survival analysis, patients with abdominal aortic aneurysms less than 70mm were considered. Sensitivity analyses including control patients and abdominal aortic aneurysms of all sizes were performed. Results: A total of 67 patients who underwent 109 CT angiography examinations before aneurysm rupture were identified. The majority were men (47, 70%) and the median age at the time of CTA examination was 77 (71-83) years. The median maximum aneurysm diameter was 56 (interquartile range 46-65) mm and the median time to rupture was 2.13 (interquartile range 0.64-4.72) years. In univariable analysis, maximum aneurysm diameter, aneurysm volume, peak wall stress, and peak wall rupture index were all associated with risk of rupture. Women had an increased HR for rupture when adjusted for maximum aneurysm diameter or aneurysm volume (HR 2.16, 95% c.i. 1.23 to 3.78 (P = 0.007) and HR 1.92, 95% c.i. 1.06 to 3.50 (P = 0.033) respectively). In multivariable analysis, the peak wall rupture index was associated with risk of rupture. The HR for peak wall rupture index was 1.05 (95% c.i. 1.03 to 1.08) per % (P < 0.001) when adjusted for maximum aneurysm diameter and 1.05 (95% c.i. 1.02 to 1.08) per % (P < 0.001) when adjusted for aneurysm volume. Conclusion: Biomechanical factors appear to be important in the prediction of abdominal aortic aneurysm rupture. Women are at increased risk of rupture when adjustments are made for maximum aneurysm diameter alone.
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| 10. |
- Siika, Antti, et al.
(författare)
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Three-dimensional growth and biomechanical risk progression of abdominal aortic aneurysms under serial computed tomography assessment
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Growth of abdominal aortic aneurysms (AAAs) is often described as erratic and discontinuous. This study aimed at describing growth patterns of AAAs with respect to maximal aneurysm diameter (Dmax) and aneurysm volume, and to characterize changes in the intraluminal thrombus (ILT) and biomechanical indices as AAAs grow. 384 computed tomography angiographies (CTAs) from 100 patients (mean age 70.0, standard deviation, SD = 8.5 years, 22 women), who had undergone at least three CTAs, were included. The mean follow-up was 5.2 (SD = 2.5) years. Growth of Dmax was 2.64 mm/year (SD = 1.18), volume 13.73 cm3/year (SD = 10.24) and PWS 7.3 kPa/year (SD = 4.95). For Dmax and volume, individual patients exhibited linear growth in 87% and 77% of cases. In the tertile of patients with the slowest Dmax-growth (< 2.1 mm/year), only 67% belonged to the slowest tertile for volume-growth, and 52% and 55% to the lowest tertile of PWS- and PWRI-increase, respectively. The ILT-ratio (ILT-volume/aneurysm volume) increased with time (2.6%/year, p < 0.001), but when adjusted for volume, the ILT-ratio was inversely associated with biomechanical stress. In contrast to the notion that AAAs grow in an erratic fashion most AAAs displayed continuous and linear growth. Considering only change in Dmax, however, fails to capture the biomechanical risk progression, and parameters such as volume and the ILT-ratio need to be considered.
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