| 1. |
- Biasetti, Jacopo, et al.
(författare)
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Hemodynamics of the Normal Aorta Compared to Fusiform and Saccular Abdominal Aortic Aneurysms with Emphasis on a Potential Thrombus Formation Mechanism
- 2010
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Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 38:2, s. 380-390
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Tidskriftsartikel (refereegranskat)abstract
- Abdominal Aortic Aneurysms (AAAs), i.e., focal enlargements of the aorta in the abdomen are frequently observed in the elderly population and their rupture is highly mortal. An intra-luminal thrombus is found in nearly all aneurysms of clinically relevant size and multiply affects the underlying wall. However, from a biomechanical perspective thrombus development and its relation to aneurysm rupture is still not clearly understood. In order to explore the impact of blood flow on thrombus development, normal aortas (n = 4), fusiform AAAs (n = 3), and saccular AAAs (n = 2) were compared on the basis of unsteady Computational Fluid Dynamics simulations. To this end patient-specific luminal geometries were segmented from Computerized Tomography Angiography data and five full heart cycles using physiologically realistic boundary conditions were analyzed. Simulations were carried out with computational grids of about half a million finite volume elements and the Carreau-Yasuda model captured the non-Newtonian behavior of blood. In contrast to the normal aorta the flow in aneurysm was highly disturbed and, particularly right after the neck, flow separation involving regions of high streaming velocities and high shear stresses were observed. Naturally, at the expanded sites of the aneurysm average flow velocity and wall shear stress were much lower compared to normal aortas. These findings suggest platelets activation right after the neck, i.e., within zones of pronounced recirculation, and platelet adhesion, i.e., thrombus formation, downstream. This mechanism is supported by recirculation zones promoting the advection of activated platelets to the wall.
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| 2. |
- Domeij-Arverud, Erica, et al.
(författare)
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Ageing, deep vein thrombosis and male gender predict poor outcome after acute Achilles tendon rupture
- 2016
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Ingår i: The Bone & Joint Journal. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 2049-4394. ; 98B98-B:12, s. 1635-1641
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patients with acute Achilles tendon rupture (ATR) exhibit prolonged healing, high incidence of deep venous thrombosis (DVT) and a wide variation of functional outcome. This extensive discrepancy in outcome may be explained by a lack of knowledge of detrimental factors, and subsequent shortage of adequate interventions. Methods: A total of 111 patients (84 men, 16 women; mean age 40.3±8.4) with acute total ATR were prospectively assessed. At one year post-operatively a uniform outcome score, Achilles Combined Outcome Score (ACOS), was obtained by combining three validated, independent, outcome measures: Achilles tendon Total Rupture Score, heel-rise height test, and limb symmetry heel-rise height. Candidate predictors of ACOS included; treatment, sex, age, smoking, body mass index (BMI), time to surgery, physical activity level pre- and post-injury, symptoms, quality of life and DVT-incidence. Results: Three independent variables correlated significantly with the dichotomized outcome score ACOS, while the other factors demonstrated no correlation. Low age (40 or less=0; above 40=1) was the strongest independent predictor of developing a good outcome at one year after ATR (OR= 0.20, 95 % C.I. 0.08 – 0.51), followed by female gender (Man= 1; Woman= 2) (OR= 4.18, 95 % C.I. 1.01 – 17.24). Notably, patients without a DVT (No=0, Yes=1) during post-operative immobilization experienced a better outcome (OR= 0.31, 95 % C.I. 0.12 – 0.80). Conclusion: DVT during leg immobilization, aging and male gender are independent negative predictors of outcome in patients with acute ATR. Age and gender should be further studied as to pinpoint the underlying causes leading to poor outcome. To enhance the outcome after ATR the first clinical focus should be on DVT-prevention during immobilization, possibly by usage of mechanical compression therapy and early weight bearing and mobilization.
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| 3. |
- Domeij-Arverud, Erica, et al.
(författare)
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Intermittent pneumatic compression reduces the risk of deep vein thrombosis during post-operative lower limb immobilisation : a prospective randomised trial of acute ruptures of the Achilles tendon
- 2015
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Ingår i: The Bone & Joint Journal. - Stockholm : Karolinska Institutet, Dept of Molecular Medicine and Surgery. - 2049-4394. ; 97B97-B:5, s. 675-680
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Tidskriftsartikel (refereegranskat)abstract
- Deep vein thrombosis is a common complication when immobilising the lower limb after surgery. We hypothesised that adjuvant intermittent pneumatic compression (IPC) during post-operative outpatient immobilisation of the lower limb could reduce the incidence of deep vein thrombosis (DVT). A total of 150 patients with acute Achilles tendon rupture were randomised to either treatment with IPC for six hours daily (n = 74) under an orthosis or treatment as usual (n = 74) in a plaster cast. At two weeks post-operatively the incidence of DVT was assessed using compression duplex ultrasound (CDU) by two ultrasonographers blinded to treatment. After the IPC intervention had ended, all patients were immobilised in the orthosis for another four weeks and a second CDU was performed. Trial registration: www.clinicaltrials.gov; NCT01317160. At two weeks the DVT rate was 21% in the IPC group and 38% in the control group (OR = 2.36; 95% CI 1.11 to 5.01). Age > 39 years was found to be a strong risk factor for DVT (OR = 4.84; 95% CI 2.14 to 10.96). Treatment with IPC corrected for age reduced the risk significantly (OR = 0.36; 95% CI 0.16 to 0.80). At six weeks, however, the frequency of DVT was 49% in the IPC group and 51% in the control group (OR = 0.94; 95% CI 0.49 to 1.83). IPC seems to be an effective method of reducing the risk of early DVT in leg-immobilised outpatients. A high risk of DVT during prolonged immobilisation warrants further study.
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| 4. |
- Giampaolo, Martufi, et al.
(författare)
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Abdominal Aortic Aneurysm development over time : Experimental evidence and constitutive modeling
- 2010
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Ingår i: Proceedings of the 6th World Congress of Biomechanics. - : Springer. - 9783642145148
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Konferensbidrag (refereegranskat)abstract
- Abdominal Aortic Aneurysms (AAAs) are defined as a localized permanent dilatation of the infrarenal aorta at least 50 % of its normal diameter. AAAs are frequently diagnosed in the elderly male population and evaluating rupture risk is critically important as aneurysm rupture carries high mortality rates. Growth predictors might be helpful to assess AAA rupture risk and could therefore give a better graded indication for elective repair in order to reduce related mortality without unnecessarily increasing the rate of interventions. Factors associated with AAA growth are still limited but there are some evidence that higher initial AAA diameter is related to faster AAA expansion [1]. The initial dilatation is dependent on elastin degradation, but strength of the AAA is maintained by increased production of collagen. It has been suggested that rupture occurs when collagen production is insufficient to counteract load-bearing at high pressure [2]. AAA growth quantification 30 patients with infrarenal AAAs were included in this study. Criteria for inclusion were 1-year follow-up and availability of at least two high-resolution Computer Tomography-Angiography (CTA) scans. Consequently, 60 CT-A scans were systematically segmented, reconstructed and analyzed (A4research, VASCOPS GmbH), in order to investigate geometrical and mechanical factors likely to be correlated with AAA growth. Derived results were analyzed with an especially developed (automatic) analyzing schema (MatLab, The MathWorks), and the derived information aims at guiding the development of an analytical growth model for AAAs. Constitutive Modeling Collagen is a structural protein responsible for the mechanical strength, stiffness and toughness of biological tissues like skin, tendon, bone, cornea, lung and vasculature. In the present study we considered the enlargement of the aneurysm as a consequence of a pathological degradation and synthesis of collagen, i.e. malfunction of collagen turn-over. Consequently, the vascular wall is modeled by an (inert) matrix material representing the elastin, which is reinforced by a dynamic structure of bundles of collagen. Specifically, collagen is formed by a continuous stress-mediated process and deposited in the current configuration [3] and removed by a constant degradation rate. Finally the micro-plane concept [4] is used for the Finite Element implementation [5] of the constitutive model. Results and conclusions The quantitative description of AAA growth by examining patient follow-up data revealed novel insights into the natural history of this disease. Most interestingly not all portions of the AAA seem to enlarge, some might be stable or even shrink over time; a feature that has not yet been considered by models reported in the literature. The model proposed within this study has a strong biological motivation and captures saline feature of AAA growth. Besides that, the micro-plane approach allows a straight forward FE implementation and preliminary results indicate its numerical robustness. References [1] F.J.V. Schlösser, et al., J Vasc Surg, 47:1127–1133 2008. [2] E. Choke, et al., Eur.j.Vasc.endovasc.surg, 30(3):227-44 2005. [3] J.D.Humphrey, J Biomech Eng, 121:591–597 1999. [4] Z.P. Bazant and P.C. Prat, J Eng Mech, 113(7) 1050-1064 1987. [5] S. Federico and T.C Gasser, J R Soc Interface (in press)
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| 5. |
- Labruto, Fausto
(författare)
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Modifications of cardiovascular response to ischemia and trauma
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ischemia and trauma are two clinical problems characterized by a common response: inflammation and potentially deleterious effects on the organism. Surgery is a form of trauma, and the most advanced surgical operations, including open heart surgery, aortic surgery, and organ transplantation, cause trauma and ischemia of the cardiovascular system. It is a big challenge to develop pharmacological and surgical methods of organ protection in this situation. Organ protection can be achieved by preconditioning, an intrinsic defence mechanism triggered by brief episodes of ischemia and reperfusion. Unravelling the mechanisms underlying preconditioning may provide new therapeutic options in the treatment of inflammatory disease. The aims of this thesis were to investigate a possible therapeutic effect of lazaroid pretreatment and its mechanism of action in a model of hemorrhagic shock and trauma, with focus on heat shock protein (HSP) 72 induction; to study the role of intraperitoneal injection and intermittent limb ischemia on heart function and the role of mitogen activated protein kinases, inducible nitric oxide synthase and nuclear factor kappa-B (NFkappaB) in the signaling of protection; to explore the role of tumor necrosis factor alpha (TNFalpha) and NFkappaB in preconditioning by hyperoxia and in bum injuryinduced myocardial intolerance to ischemia. Rats were subjected to controlled hemorrhagic shock and trauma. The outcome of hemorrhagic shock was improved in rats pretreated with the second-generation corticosteroid analogue drug U-83836E, evident as improved maintenance of blood pressure and acid-base balance. This improvement concurred with an increased cardiac production of HSP72. Mice were subjected to intraperitoneal injections of fluid, and 24 hours later their hearts were isolated and Langendorff-perfused with induced global ischemia and reperfusion. Intraperitoneal injection provided a preconditioning-like protection of the heart with improved postischemic function and reduced infarct size. The myocardial protection did not involve signalling with activation of NFkappaB or phosphorylation of mitogen activated protein kinases. Intermittent episodes of hind limb ischemia and reperfusion protected the heart 24 hours later, activating NFkappaB in hearts and skeletal muscle, and increasing cardiac expression of inducible nitric oxide synthase. When hind limb preconditioning was performed in mice deficient of the NFkappaB p105 subunit or of inducible nitric oxide synthase, the protective effect was abolished. When mice were exposed to hyperoxia (>95% oxygen) before heart isolation, postischemic function was improved and infarct size reduced. Pulmonary expression of TNFalpha and its synthetizing enzyme TACE was increased after hyperoxic exposure. Hyperoxic pretreament did not afford myocardial protection of mice genetically mutated to lack TNFalpha or its receptor 1. Hyperoxic pretreatment was also efficient in protecting vascular function from the detrimental effects of exposure to TNFalpha. TNFalpha, but not NFkappaB, was increased in hearts of mice subjected to minor cutaneous bums, which suffered an increased susceptibility to ischemia/reperfusion. Pharmacological blockade of TNFalpha by etanercept abolished this effect. In conclusion, cardiovascular protection can be obtained by different stimuli that induce a state of self protection, resulting in tolerance to trauma and ischemia. Lazaroids induce expression of the beneficial HSP72. The main findings of this thesis are that some components of innate immunity, such as NFkappaB and the proinflammatory cytokine TNFalpha, are necessary to evoke organ protection by preconditioning. However, TNFalpha is also important for developing decreased tolerance to ischemia following bum injury. Finding the balance between the protective and detrimental effects for pharmacological treatment of patients undergoing major surgery is a challenge for the future.
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| 6. |
- Larsson, Emma, et al.
(författare)
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Analysis of aortic wall stress and rupture risk in patients with abdominal aortic aneurysm with a gender perspective
- 2011
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Ingår i: Journal of Vascular Surgery. - : Elsevier BV. - 0741-5214 .- 1097-6809. ; 54:2, s. 295-299
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The most commonly used predictor of rupture of an abdominal aortic aneurysm (AAA) is the diameter; however, this does not estimate the true risk for each patient. Why women with AAAs have an increased growth rate, weaker aortic wall, and increased risk for rupture is yet unclear. It is likely that geometrical and biomechanical properties contribute to found gender differences. Several studies have shown that peak wall stress (PWS) and peak wall rupture risk (PWRR), predicted by a finite element (FE) analysis of AAAs derived from computed tomography (CT), is a better predictor of rupture than maximum diameter. The purpose of this study was to investigate if women with AAAs have an increased PWS and PWRR using an FE model compared to men. Method: Fifteen men and 15 women (AAAs 4-6 cm) were included. AAA geometry was derived from CT scans, and PWS and PWRR were estimated using the FE method. Comparisons were made by t test and Mann-Whitney test. Results: Mean age (women 73 years old vs men 71 years old) and mean AAA diameter was similar (49.7 mm vs 50.1 mm) for women and men. PWS did not differ for women 184 and men 198 kPa. PWRR was 0.54 (0.28-0.85) for women and 0.43 (0.24-0.66) for men, P = .06. Conclusion: This is the first analysis of stress and strength of the aneurysm wall with a gender perspective. The reported higher rupture risk for women has previously not been tested with geometrical and biomechanical properties. PWS did not differ, but the PWRR was slightly higher in women. However, the difference did not reach statistical significance, probably due to the small sample size. In summary, the results in the present study suggest that differences in biomechanical properties could be a contributing explanation for the higher rupture risk reported for female patients with AAAs. (J Vase Surg 2011;54:295-9.)
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| 7. |
- Latifi, Ali, et al.
(författare)
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Does enteral contrast increase the accuracy of appendicitis diagnosis?
- 2011
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Ingår i: Radiologic Technology. - 0033-8397 .- 1943-5657. ; 82:4, s. 294-299
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Several approaches traditionally have helped opacify the bowel when computed tomography (CT) is used to diagnose appendicitis. With the development of multidetector row CT (MDCT), the need for enteral contrast agents is less obvious. Purpose The objective of this study was to evaluate retrospectively the accuracy of MDCT demonstration of appendicitis using enteral contrast agents. METHODS: We reviewed radiologic reports of all 246 adult patients with suspected appendicitis who underwent 16-slice MDCT during 2005-2006 at our department. The use of enteral contrast agents and the route of administration were documented by one investigator. A radiologist evaluated whether the responses in the reports were consistent with diagnosis of appendicitis. The accuracy of the radiologic reports was assessed using the results of surgery, histopathology and 3 to 21 months of follow-up. RESULTS: Of patients studied, 14.6% received no enteral contrast agent, 8.5% received both oral contrast and rectal contrast (enema), 46.7% received oral contrast and 30.1% received rectal contrast enemas. The accuracies for the CT diagnosis of appendicitis with different combinations of agents ranged from 95% to 100%, with no significant difference among groups. CONCLUSION: Our study shows that the accuracy for diagnosis of appendicitis by abdominal 16-slice MDCT is high regardless of enteral contrast use. Therefore, further use of enteral contrast agents for CT diagnosis of appendicitis in adults cannot be recommended.
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| 8. |
- Latifi, Ali, et al.
(författare)
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The accuracy of focused abdominal CT in patients presenting to the emergency department
- 2009
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Ingår i: Emergency Radiology. - : Springer Science and Business Media LLC. - 1070-3004 .- 1438-1435. ; 16:3, s. 209-215
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Tidskriftsartikel (refereegranskat)abstract
- Focused computed tomography(CT) examination (FCT) is CT limited to a specific abdominal area in an attempt to reduce radiation exposure. We wanted to evaluate FCT on the basis of information from the request form and thus reduce radiation dose to the patient without missing relevant findings. We retrospectively analyzed 189 consecutive acute abdominal CT, dividing the findings as localized in the upper or lower abdomen. Another researcher blindly determined where the CT should be focused to, based only on information provided in the request form. The sensitivity and specificity of FCT in patients with symptoms from only upper abdomen was 100%. Sensitivity, specificity, and accuracy of FCT in patients with symptom from only lower abdomen were 79%, 100%, and 92%, respectively. Our study suggests that among patients with symptoms from the lower abdomen, not examining the upper abdomen would lead to missing relevant findings.
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| 9. |
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| 10. |
- Torkzad, Michael R., et al.
(författare)
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Impact of COVID-19 on the incidence of CT-diagnosed appendicitis and its complications in the UK and Sweden
- 2022
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Ingår i: International Journal of Colorectal Disease. - : Springer Nature. - 0179-1958 .- 1432-1262. ; 37:6, s. 1375-1383
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Tidskriftsartikel (refereegranskat)abstract
- Aim To compare the number of appendicitis cases and its complications, during the first months of the COVID-19 pandemic in Sweden and the UK and the corresponding time period in 2019. Method Reports of emergency abdominopelvic CT performed at 56 Swedish hospitals and 38 British hospitals between April and July 2020 and a corresponding control cohort from 2019 were reviewed. Two radiologists and two surgeons blinded to the date of cohorts analyzed all reports for diagnosis of appendicitis, perforation, and abscess. A random selection of cases was chosen for the measurement of inter-rater agreement. Result Both in Sweden (6111) and the UK (5591) fewer, abdominopelvic CT scans were done in 2020 compared to 2019 (6433 and 7223, respectively); p < 0.001. In the UK, the number of appendicitis was 36% lower in April-June 2020 compared to 2019 but not in Sweden. Among the appendicitis cases, there was a higher number of perforations and abscesses in 2020, in Sweden. In the UK, the number of perforations and abscesses were initially lower (April-June 2020) but increased in July 2020. There was a substantial inter-rater agreement for the diagnosis of perforations and abscess formations (K = 0.64 and 0.77). Conclusion In Sweden, the number of appendicitis was not different between 2019 and 2020; however, there was an increase of complications. In the UK, there was a significant decrease of cases in 2020. The prevalence of complications was lower initially but increased in July. These findings suggest variability in delay in diagnosis of appendicitis depending on the country and time frame studied.
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