1
|
Thirugnanasambandam M, Canchi T, Piskin S, Karmonik C, Kung E, Menon PG, Avril S, Finol EA. Design, Development, and Temporal Evaluation of a Magnetic Resonance Imaging-Compatible In Vitro Circulation Model Using a Compliant Abdominal Aortic Aneurysm Phantom. J Biomech Eng 2021; 143:1096849. [PMID: 33493273 DOI: 10.1115/1.4049894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Indexed: 11/08/2022]
Abstract
Biomechanical characterization of abdominal aortic aneurysms (AAAs) has become commonplace in rupture risk assessment studies. However, its translation to the clinic has been greatly limited due to the complexity associated with its tools and their implementation. The unattainability of patient-specific tissue properties leads to the use of generalized population-averaged material models in finite element analyses, which adds a degree of uncertainty to the wall mechanics quantification. In addition, computational fluid dynamics modeling of AAA typically lacks the patient-specific inflow and outflow boundary conditions that should be obtained by nonstandard of care clinical imaging. An alternative approach for analyzing AAA flow and sac volume changes is to conduct in vitro experiments in a controlled laboratory environment. In this study, we designed, built, and characterized quantitatively a benchtop flow loop using a deformable AAA silicone phantom representative of a patient-specific geometry. The impedance modules, which are essential components of the flow loop, were fine-tuned to ensure typical intraluminal pressure conditions within the AAA sac. The phantom was imaged with a magnetic resonance imaging (MRI) scanner to acquire time-resolved images of the moving wall and the velocity field inside the sac. Temporal AAA sac volume changes lead to a corresponding variation in compliance throughout the cardiac cycle. The primary outcome of this work was the design optimization of the impedance elements, the quantitative characterization of the resistive and capacitive attributes of a compliant AAA phantom, and the exemplary use of MRI for flow visualization and quantification of the deformed AAA geometry.
Collapse
Affiliation(s)
- Mirunalini Thirugnanasambandam
- University of Texas at San Antonio, UTSA/UTHSCSA Joint Graduate Program in Biomedical Engineering, San Antonio, TX 78249
| | - Tejas Canchi
- Department of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
| | - Senol Piskin
- Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249; Department of Mechanical Engineering, Istinye University, Istanbul 34010, Turkey
| | | | - Ethan Kung
- Department of Mechanical Engineering, Clemson University Clemson, SC 29634
| | - Prahlad G Menon
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260
| | - Stephane Avril
- Ecole Nationale Supérieure des Mines, Center for Biomedical and Healthcare Engineering, St-Etienne 75006, France
| | - Ender A Finol
- University of Texas at San Antonio, UTSA/UTHSCSA Joint Graduate Program in Biomedical Engineering, San Antonio, TX 78249; Department of Mechanical Engineering, University of Texas at San Antonio, Room EB 3.04.08 One UTSA Circle, San Antonio, TX 78249
| |
Collapse
|
2
|
Li FD, Kang R, Nie H, Wang XM, Zheng YH. An association of spleen volume and aortic diameter in patients and in mice with abdominal aortic aneurysm. BMC Surg 2017; 17:134. [PMID: 29246140 PMCID: PMC5731055 DOI: 10.1186/s12893-017-0328-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 11/27/2017] [Indexed: 12/21/2022] Open
Abstract
Background To investigate the potential mechanism of splenic enlargement in Ang II/APOE model and the associations between the spleen volume and the indices of abdominal aortic aneurysm (AAA) in human. Methods To investigate the changes of spleen volume on AAA formation, apolipoprotein E knockout (Apo E−/−) mice were treated with Ang II (1000 ng/kg/min) up to 28 days to generate AAA. We used Magnetic Resonance Imaging (MRI), liquid measurement, H&E and immunohistochemistry to analyze the morphological or pathological changes of spleen. To investigate the changes of spleen volume in human, a retrospective case-control study involving 30 male AAA patients and 25 male controls were performed. Spleen volume was measured on computed tomography images. Univariate analysis and multivariable sequential logistic regression analyses were used to analyze the association between spleen volume and maximal diameter (Dmax). Results In Ang II/APOE model, we found splenic enlargement in mice with AAA compared with the sham group. Histopathological investigations revealed hypertrophies of splenic follicles and increased populations of CD3+ T cells. In clinic cohort study, univariate analysis revealed higher values in large AAA (Dmax > 5.5 cm,n = 15) compared with the small (Dmax < 5.5 cm,n = 15) for spleen volume (230.6 ± 64.5 cm3 vs. 170.0 ± 32.8 cm3; P = 0.0030). Regression analysis revealed a statistically significant positive linear correlation of spleen volume and Dmax of AAA (r = 0.3611;P = 0.0423). Conclusions Mimicking the splenic pathology observed in murine AAA model, there is a strong positive correlation between spleen volume and the Dmax in male AAA patients. As Dmax is a valuable predictor of AAA rupture, the spleen enlargement may be another indicator.
Collapse
Affiliation(s)
- Fang-Da Li
- Department of Vascular Surgery, Peking Union Medical College Hospital, No.1 Shuaifuyuan, Dongdan, Dongcheng District, Beijing, 100730, China
| | - Rui Kang
- Shandong Medical Imaging Research Institute, Shandong Provincial Key Laboratory of Diagnosis and Treatment of Cardio-Cerebral Vascular Diseases, Shandong University, NO, 324, Jingwu Road, Jinan, Shandong, 250021, China
| | - Hao Nie
- Department of Vascular Surgery, Peking Union Medical College Hospital, No.1 Shuaifuyuan, Dongdan, Dongcheng District, Beijing, 100730, China
| | - Xi-Ming Wang
- Shandong Medical Imaging Research Institute, Shandong Provincial Key Laboratory of Diagnosis and Treatment of Cardio-Cerebral Vascular Diseases, Shandong University, NO, 324, Jingwu Road, Jinan, Shandong, 250021, China.
| | - Yue-Hong Zheng
- Department of Vascular Surgery, Peking Union Medical College Hospital, No.1 Shuaifuyuan, Dongdan, Dongcheng District, Beijing, 100730, China.
| |
Collapse
|
3
|
Zommorodi S, Roy J, Steuer J, Hultgren R. High proportion of known abdominal aortic aneurysm in patients with rupture indicates surveillance deficiency. J Vasc Surg 2016; 64:949-955.e1. [PMID: 27666443 DOI: 10.1016/j.jvs.2016.04.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 04/06/2016] [Indexed: 12/13/2022]
Abstract
OBJECTIVE This study assessed the proportion of previously known abdominal aortic aneurysm (AAA) in patients presenting with a ruptured AAA (rAAA) and analyzed the reasons for nontreatment at the time of the initial AAA diagnosis. METHODS This retrospective, observational study included all patients with rAAA admitted to a hospital in the counties of Stockholm and Gotland during 2009 to 2013. The patients' records were retrospectively reviewed, with extraction of data on previously detected AAA, demographics, and mortality at 30 and 90 days. RESULTS We identified 283 patients (76% men) with a mean age of 78.7 years. An AAA had been previously detected in 85 (30%). The overall mortality was higher (68% vs 53%; P = .018) and the intervention rate was lower in patients with a previously detected AAA (59% vs 82%, P < .001). The 90-day mortality rate for all treated rAAA was 43%. Reasons for nontreatment at the initial AAA detection were denial of elective surgery in 31 (36%), patient choice in 15 (18%), size-related in 11 (13%), and surveillance deficiency in 26 (31%). The latter group included patients who failed to comply, missed referral for computed tomography scans, and lack of follow-up of radiology reports. At the time of rupture, 22 patients (85%) were treated, with 30-day and 90-day mortality rates both at 41% (n = 9). CONCLUSIONS One-third of patients admitted with a rAAA had a previously detected AAA. The surgeons' decision to deny elective surgery and surveillance deficiency were the two main reasons for nontreatment at time of the AAA diagnosis. Improved patient-specific protocols to reduce the surveillance gaps and new methods of determining rupture risk in each case of AAA could be two possible future strategies to reduce the incidence of rupture.
Collapse
Affiliation(s)
- Sayid Zommorodi
- Department of Surgery, Section for Vascular Surgery, Södersjukhuset, Stockholm, Sweden; Department of Clinical Science and Education, Karolinska Institutet, Stockholm, Sweden
| | - Joy Roy
- Department of Vascular Surgery, Karolinska University Hospital, Stockholm, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Johnny Steuer
- Department of Surgery, Section for Vascular Surgery, Södersjukhuset, Stockholm, Sweden; Department of Clinical Science and Education, Karolinska Institutet, Stockholm, Sweden
| | - Rebecka Hultgren
- Department of Vascular Surgery, Karolinska University Hospital, Stockholm, Sweden; Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
| |
Collapse
|
4
|
Lujan R, Nguyen A, Donayre C, Lee L, Wallot I, Kopchock G, Lippmann M, White R. Impact of Endoluminal Treatment on Small Abdominal Aortic Aneurysm: Aneurysm Sac Regression and Secondary Interventions With 5 Years of Follow-Up. Vasc Endovascular Surg 2016; 41:294-300. [PMID: 17704331 DOI: 10.1177/1538574407301142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Does early repair of small abdominal aortic aneurysms (AAAs) lead to faster aneurysm sac regression or less secondary intervention? Computed tomography scans and reconstructions from M2S of all patients undergoing endovascular AAA repair at our institution from 1996 to 2006 were retrospectively reviewed. A small aneurysm is defined as an aneurysm sac to renal diameter ratio of less than 2. There were 374 patients with endovascular AAA repair that had complete imaging studies. There were 75 patients (20%) with small AAAs; of those, 19 patients (25.3%) had endoleak compared with 108 patients (36.1%) with a large aneurysm ( P = .1). Over a mean follow-up time of 42 months (range, 1-109), 11 small AAAs (14.7%) had secondary interventions compared with 58 (19.4%) of the large AAAs ( P = .41). Small AAAs at 5 years had a 2.5% volume sac regression but a 3.0% increase in diameter. Those with a large aneurysm had a slight increase in sac volume and diameter at 1 month (3.3%, 1.4%) and then steadily decreased to —13.4% and —8.8% at 5 years. Patients with Endologix (Endologix Inc., Irvine, Calif) devices have the most regression when compared with patients with AneuRx (Medtronic Inc., Minneapolis, Minn) and Talent (Medtronic Inc., Minneapolis, Minn) devices. Early endovascular intervention in small AAAs does not result in faster aneurysm sac regression or secondary intervention. Aneurysm sac regression is significantly affected by endoleak, aneurysm size, and device used.
Collapse
|
5
|
Driffield T, Smith PC. A Real Options Approach to Watchful Waiting: Theory and an Illustration. Med Decis Making 2016; 27:178-88. [PMID: 17409367 DOI: 10.1177/0272989x06297390] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Watchful waiting is a form of clinical management under which immediate curative treatment is not given. Instead, the patient undergoes a period of observation during which periodic tests monitor the progression of the illness. Hitherto, little attention has been given to how such patient management should be modeled from an economic perspective. Watchful waiting preserves an “option” to start treatment some time in the future, and evaluating a watchful waiting regime therefore has close analogies with pricing a financial option in the derivatives market. This article demonstrates how the methods used to price financial options can be used to decide when to pursue a watchful waiting strategy for a particular patient. The principles of option pricing are illustrated with the example of abdominal aortic aneurysm. A simple trinomial model of disease progression is used, in which patients are periodically monitored, and their health state can remain unchanged, deteriorate, or improve. Backward induction is used to solve the model at each period, with optimal treatment recommendations depending on the current health state. At very low levels of expected net benefits, the patient is discharged. At high levels, the patient is treated immediately. At intermediate levels, watchful waiting continues. The authors argue that option pricing methods offer important insights into the evaluation of a watchful waiting strategy. The methods also have potential applications in other domains of medical care. Key words: watchful waiting; option pricing; cost-effectiveness analysis. (Med Decis Making 2007;27:178—188)
Collapse
|
6
|
van Disseldorp EMJ, Hobelman KH, Petterson NJ, van de Vosse FN, van Sambeek MRHM, Lopata RGP. Influence of limited field-of-view on wall stress analysis in abdominal aortic aneurysms. J Biomech 2016; 49:2405-12. [PMID: 26924662 DOI: 10.1016/j.jbiomech.2016.01.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 01/29/2016] [Indexed: 11/29/2022]
Abstract
Abdominal aortic aneurysms (AAAs) are local dilations of the aorta which can lead to a fatal hemorrhage when ruptured. Wall stress analysis of AAAs has been widely reported in literature to predict the risk of rupture. Usually, the complete AAA geometry including the aortic bifurcation is obtained by computed tomography (CT). However, performing wall stress analysis based on 3D ultrasound (3D US) has many advantages over CT, although, the field-of-view (FOV) of 3D US is limited and the aortic bifurcation is not easily imaged. In this study, the influence of a limited FOV is examined by performing wall stress analysis on CT-based (total) AAA geometries in 10 patients, and observing the changes in 99th percentile stresses and median stresses while systematically limiting the FOV. Results reveal that changes in the 99th percentile wall stresses are less than 10% when the proximal and distal shoulders of the aneurysm are in the shortened FOV. Wall stress results show that the presence of the aortic bifurcation in the FOV does not influence the wall stresses in high stress regions. Hence, the necessity of assessing the complete FOV, including the aortic bifurcation, is of minor importance. When the proximal and distal shoulders of the AAA are in the FOV, peak wall stresses can be detected adequately.
Collapse
Affiliation(s)
- Emiel M J van Disseldorp
- Cardiovascular Biomechanics Group, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Department of Vascular Surgery, Catharina Hospital Eindhoven, Eindhoven, The Netherlands.
| | - Koen H Hobelman
- Cardiovascular Biomechanics Group, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Niels J Petterson
- Cardiovascular Biomechanics Group, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Frans N van de Vosse
- Cardiovascular Biomechanics Group, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Marc R H M van Sambeek
- Department of Vascular Surgery, Catharina Hospital Eindhoven, Eindhoven, The Netherlands
| | - Richard G P Lopata
- Cardiovascular Biomechanics Group, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| |
Collapse
|
7
|
Lin JB, Phillips EH, Riggins TE, Sangha GS, Chakraborty S, Lee JY, Lycke RJ, Hernandez CL, Soepriatna AH, Thorne BRH, Yrineo AA, Goergen CJ. Imaging of small animal peripheral artery disease models: recent advancements and translational potential. Int J Mol Sci 2015; 16:11131-77. [PMID: 25993289 PMCID: PMC4463694 DOI: 10.3390/ijms160511131] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Accepted: 03/10/2015] [Indexed: 12/11/2022] Open
Abstract
Peripheral artery disease (PAD) is a broad disorder encompassing multiple forms of arterial disease outside of the heart. As such, PAD development is a multifactorial process with a variety of manifestations. For example, aneurysms are pathological expansions of an artery that can lead to rupture, while ischemic atherosclerosis reduces blood flow, increasing the risk of claudication, poor wound healing, limb amputation, and stroke. Current PAD treatment is often ineffective or associated with serious risks, largely because these disorders are commonly undiagnosed or misdiagnosed. Active areas of research are focused on detecting and characterizing deleterious arterial changes at early stages using non-invasive imaging strategies, such as ultrasound, as well as emerging technologies like photoacoustic imaging. Earlier disease detection and characterization could improve interventional strategies, leading to better prognosis in PAD patients. While rodents are being used to investigate PAD pathophysiology, imaging of these animal models has been underutilized. This review focuses on structural and molecular information and disease progression revealed by recent imaging efforts of aortic, cerebral, and peripheral vascular disease models in mice, rats, and rabbits. Effective translation to humans involves better understanding of underlying PAD pathophysiology to develop novel therapeutics and apply non-invasive imaging techniques in the clinic.
Collapse
Affiliation(s)
- Jenny B Lin
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Evan H Phillips
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Ti'Air E Riggins
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Gurneet S Sangha
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Sreyashi Chakraborty
- School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
| | - Janice Y Lee
- Psychological Sciences, Purdue University, West Lafayette, IN 47907, USA.
| | - Roy J Lycke
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Clarissa L Hernandez
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Arvin H Soepriatna
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Bradford R H Thorne
- School of Sciences, Neuroscience, Purdue University, West Lafayette, IN 47907, USA.
| | - Alexa A Yrineo
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| | - Craig J Goergen
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, Room 3025, West Lafayette, IN 47907, USA.
| |
Collapse
|
8
|
Chandra S, Raut SS, Jana A, Biederman RW, Doyle M, Muluk SC, Finol EA. Fluid-structure interaction modeling of abdominal aortic aneurysms: the impact of patient-specific inflow conditions and fluid/solid coupling. J Biomech Eng 2013; 135:81001. [PMID: 23719760 DOI: 10.1115/1.4024275] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 04/22/2013] [Indexed: 11/08/2022]
Abstract
Rupture risk assessment of abdominal aortic aneurysms (AAA) by means of biomechanical analysis is a viable alternative to the traditional clinical practice of using a critical diameter for recommending elective repair. However, an accurate prediction of biomechanical parameters, such as mechanical stress, strain, and shear stress, is possible if the AAA models and boundary conditions are truly patient specific. In this work, we present a complete fluid-structure interaction (FSI) framework for patient-specific AAA passive mechanics assessment that utilizes individualized inflow and outflow boundary conditions. The purpose of the study is two-fold: (1) to develop a novel semiautomated methodology that derives velocity components from phase-contrast magnetic resonance images (PC-MRI) in the infrarenal aorta and successfully apply it as an inflow boundary condition for a patient-specific fully coupled FSI analysis and (2) to apply a one-way-coupled FSI analysis and test its efficiency compared to transient computational solid stress and fully coupled FSI analyses for the estimation of AAA biomechanical parameters. For a fully coupled FSI simulation, our results indicate that an inlet velocity profile modeled with three patient-specific velocity components and a velocity profile modeled with only the axial velocity component yield nearly identical maximum principal stress (σ1), maximum principal strain (ε1), and wall shear stress (WSS) distributions. An inlet Womersley velocity profile leads to a 5% difference in peak σ1, 3% in peak ε1, and 14% in peak WSS compared to the three-component inlet velocity profile in the fully coupled FSI analysis. The peak wall stress and strain were found to be in phase with the systolic inlet flow rate, therefore indicating the necessity to capture the patient-specific hemodynamics by means of FSI modeling. The proposed one-way-coupled FSI approach showed potential for reasonably accurate biomechanical assessment with less computational effort, leading to differences in peak σ1, ε1, and WSS of 14%, 4%, and 18%, respectively, compared to the axial component inlet velocity profile in the fully coupled FSI analysis. The transient computational solid stress approach yielded significantly higher differences in these parameters and is not recommended for accurate assessment of AAA wall passive mechanics. This work demonstrates the influence of the flow dynamics resulting from patient-specific inflow boundary conditions on AAA biomechanical assessment and describes methods to evaluate it through fully coupled and one-way-coupled fluid-structure interaction analysis.
Collapse
Affiliation(s)
- Santanu Chandra
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
| | | | | | | | | | | | | |
Collapse
|
9
|
Silaghi H, Branchereau A, Malikov S, Andercou A. Management of small asymptomatic abdominal aortic aneurysms - a review. Int J Angiol 2012; 16:121-7. [PMID: 22477326 DOI: 10.1055/s-0031-1278264] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
Abstract
The approach for abdominal aortic aneurysms (AAAs) larger than 55 mm is well defined due to the risk of rupture being higher than 10% per year, and a 30-day perioperative mortality rate between 2.5% and 5%. However, the approach for small asymptomatic AAAs is less well defined.There are different definitions given to describe a small AAA. The one the authors accepted and applied is "a localized, permanent and irreversible dilation of the aorta of at least 50% in relation to the normal adjacent infrarenal or suprarenal aorta, with a maximum diameter between 30-55 mm".The investigators of the largest study on small AAAs (United Kingdom Small Aneurysm Trial [UK-SAT]) concluded, in brief, that ultrasound monitoring is the most appropriate solution because the results do not support a policy of surgical restoration for AAAs with a diameter of between 40 mm and 55 mm.The aim of the present review article is to highlight several challenges that could change the limits or create a more flexible deciding factor in the management of AAAs. There are multiple factors that influence surgical decision-making, and the limit on aneurysm diameter that indicates surgery should depend on the patient's age, life expectancy, general status, associated diseases, diameter in relation to body mass, risk factors, sex, anxiety and compliance during the follow-up period. Monitoring is an acceptable alternative for AAAs between 40 mm and 55 mm, and is probably the best solution for high-risk patients. Surgery is the most reasonable solution for patients who are at moderate risk, have a significant life expectancy, are less than 70 to 75 years of age, and/or have aortic aneurysms larger than 50 mm.
Collapse
Affiliation(s)
- H Silaghi
- Surgical Clinic II, UMPh Cluj-Napoca, Cluj-Napoca, Romania
| | | | | | | |
Collapse
|
10
|
Buckley CJ, Rutherford RB, Buckley SD. Influence and critique of the PIVOTAL and the EVAR 2 Trials. Semin Vasc Surg 2012; 24:149-52. [PMID: 22153024 DOI: 10.1053/j.semvascsurg.2011.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Management of a condition that has potentially life-threatening consequences may not lend itself effectively to the scrutiny of a randomized clinical trial when an observation or no treatment option is offered as part of the trial. This type of trial often experiences a significant rate of crossover of subjects from no treatment to treatment, and when results are analyzed on an intent-to-treat basis, they may fail to resolve the issue under study. These trials are frequently used as Level 1 medical evidence and the potential impact on clinical decision-making and reimbursement can be quite significant and long-lasting. The authors observed this phenomenon during participation in the Positive Impact of Endovascular Options for Treating Aneurysms Early (PIVOTAL) trial and have observed it in an analysis of the Endovascular Aneurysm Repair 2 (EVAR 2) trial. Possible solutions to mitigate the high crossover effect are offered for consideration. Some clinical conditions dealing with potentially life-threatening problems probably do not lend themselves to be studied in randomized prospective clinical trials containing an observation or no treatment arm.
Collapse
Affiliation(s)
- Clifford J Buckley
- Division of Vascular Surgery, Texas A&M University College of Medicine, Scott & White Hospital, Temple, TX 76508, USA.
| | | | | |
Collapse
|
11
|
Meyer E, Rees R. Watchfully waiting: medical intervention as an optimal investment decision. JOURNAL OF HEALTH ECONOMICS 2012; 31:349-358. [PMID: 22425768 DOI: 10.1016/j.jhealeco.2012.02.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 01/29/2012] [Accepted: 02/02/2012] [Indexed: 05/31/2023]
Abstract
Watchfully waiting involves monitoring a patient's health state over time and deciding whether to undertake a medical intervention, or to postpone it and continue observing the patient. In this paper, we consider the timing of medical intervention as an optimal stopping problem. The development of the patient's health state in the absence of intervention follows a stochastic process (geometric Brownian motion). Spontaneous recovery occurs in case the absorbing state of "good health" is reached. We determine optimal threshold values for initiating the intervention, and derive comparative statics results with respect to the model parameters. In particular, an increase in the degree of uncertainty over the patient's development in most cases makes waiting more attractive. However, this may not hold if the patient's health state has a tendency to improve. The model can be extended to allow for risk aversion and for sudden, Poisson-type shocks to the patient's health state.
Collapse
Affiliation(s)
- Elisabeth Meyer
- Helmholtz Center Munich, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany.
| | | |
Collapse
|
12
|
Li ZY. Computed wall stress may predict the growth of abdominal aortic aneurysm. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2010:2626-9. [PMID: 21096184 DOI: 10.1109/iembs.2010.5626610] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Growth rate of abdominal aortic aneurysm (AAA) is thought to be an important indicator of the potential risk of rupture. Wall stress is also thought to be a trigger for its rupture. However, stress change during the expansion of an AAA is unclear. Forty-four patients with AAAs were included in this longitudinal follow-up study. They were assessed by serial abdominal ultrasonography and computerized tomography (CT) scans if a critical size was reached or a rapid expansion occurred. Patient-specific 3-dimensional AAA geometries were reconstructed from the follow-up CT images. Structural analysis was performed to calculate the wall stresses of the AAA models at both baseline and final visit. A non-linear large-strain finite element method was used to compute the wall stress distribution. The average growth rate was 0.66 cm/year (range 0-1.32 cm/year). A significantly positive correlation between shoulder tress at baseline and growth rate was found (r=0.342; p=0.02). A higher shoulder stress is associated with a rapidly expanding AAA. Therefore, it may be useful for estimating the growth expansion of AAAs and further risk stratification of patients with AAAs.
Collapse
Affiliation(s)
- Zhi-Yong Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096 China.
| |
Collapse
|
13
|
Xenos M, Bluestein D. Biomechanical Aspects of Abdominal Aortic Aneurysm (AAA) and its Risk of Rupture: Fluid Structure Interaction (FSI) Studies. STUDIES IN MECHANOBIOLOGY, TISSUE ENGINEERING AND BIOMATERIALS 2011. [DOI: 10.1007/8415_2011_72] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
14
|
Inherent problems with randomized clinical trials with observational/no treatment arms. J Vasc Surg 2010; 52:237-41. [PMID: 20620768 DOI: 10.1016/j.jvs.2010.02.255] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 02/18/2010] [Accepted: 02/18/2010] [Indexed: 11/21/2022]
Abstract
Randomized clinical trials (RCTs) offering an observation/no treatment (OBS/NoRx) arm as control and which are focused on the management of a condition with potentially life-threatening consequences, however small the risk, often experience a significant rate of crossover to treatment by those randomized to the OBS/NoRx arm. Results of these trials when analyzed on intent-to-treat basis often fail to resolve the issue at which they were directed. The authors have observed this in trials of abdominal aortic aneurysms with this design and use these to exemplify the dilemmas RCTs of such design create, with crossovers ranging from 27% to over 60% (EVAR II, UKSAT, ADAM, PIVOTAL). Results of these trials are frequently used as level I medical evidence and their potential impact on clinical decision making and reimbursement can be quite significant and long-lasting. Recommendations regarding trial end points and suggestions to mitigate the high crossover effect are offered. It may be that some clinical conditions dealing with potentially life-threatening problems should not be studied in randomized prospective clinical trials containing an OBS/NoRx arm.
Collapse
|
15
|
Rissland P, Alemu Y, Einav S, Ricotta J, Bluestein D. Abdominal aortic aneurysm risk of rupture: patient-specific FSI simulations using anisotropic model. J Biomech Eng 2009; 131:031001. [PMID: 19154060 DOI: 10.1115/1.3005200] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Abdominal aortic aneurysm (AAA) rupture represents a major cardiovascular risk, combining complex vascular mechanisms weakening the abdominal artery wall coupled with hemodynamic forces exerted on the arterial wall. At present, a reliable method to predict AAA rupture is not available. Recent studies have introduced fluid structure interaction (FSI) simulations using isotropic wall properties to map regions of stress concentrations developing in the aneurismal wall as a much better alternative to the current clinical criterion, which is based on the AAA diameter alone. A new anisotropic material model of AAA that closely matches observed biomechanical AAA material properties was applied to FSI simulations of patient-specific AAA geometries in order to develop a more reliable predictor for its risk of rupture. Each patient-specific geometry was studied with and without an intraluminal thrombus (ILT) using two material models-the more commonly used isotropic material model and an anisotropic material model-to delineate the ILT contribution and the dependence of stress distribution developing within the aneurismal wall on the material model employed. Our results clearly indicate larger stress values for the anisotropic material model and a broader range of stress values as compared to the isotropic material, indicating that the latter may underestimate the risk of rupture. While the locations of high and low stresses are consistent in both material models, the differences between the anisotropic and isotropic models become pronounced at large values of strain-a range that becomes critical when the AAA risk of rupture is imminent. As the anisotropic model more closely matches the biomechanical behavior of the AAA wall and resolves directional strength ambiguities, we conclude that it offers a more reliable predictor of AAA risk of rupture.
Collapse
Affiliation(s)
- Peter Rissland
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794-8181, USA
| | | | | | | | | |
Collapse
|
16
|
Lall P, Gloviczki P, Agarwal G, Duncan AA, Kalra M, Hoskin T, Oderich GS, Bower TC. Comparison of EVAR and open repair in patients with small abdominal aortic aneurysms: can we predict results of the PIVOTAL trial? J Vasc Surg 2009; 49:52-9. [PMID: 19174250 DOI: 10.1016/j.jvs.2008.07.085] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Revised: 07/31/2008] [Accepted: 07/31/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Data from multicenter studies support observation of small abdominal aortic aneurysms (AAAs) over open repair (OR), but the role of endovascular repair (EVAR) is unclear pending outcome of the Positive Impact of EndoVascular Options for Treating Aneurysm earLy (PIVOTAL) trial. Our goal was to predict the outcome of the trial by comparing results of small AAA repair using EVAR vs OR at a tertiary institution. METHODS Using selection criteria of PIVOTAL trial, we reviewed clinical data of 194 consecutive patients, who underwent EVAR or OR for 4.0-5.0 cm AAAs between 1997 and 2004. All-cause and aneurysm-related deaths, complications, reinterventions, ruptures, and conversions were documented; factors affecting outcome were analyzed using chi(2) tests, Wilcoxon rank-sum tests, logistic regression Kaplan-Meier method with log-rank tests, and Cox proportional hazards regression. Median follow-up was 3.9 years (range, 1 month to 9 years). RESULTS A total of 194 patients, 162 males, 32 females (mean age: 71 years, range, 46-86) underwent 162 OR and 32 EVAR. EVAR patients were older (mean 74 +/- 6 vs 71 +/- 7, P = .002), had lower ejection fraction (mean 54 +/- 11 vs 61 +/- 13, P = .0002), and less likely to have ever smoked (69% vs 85%, P = .03) than OR patients. Thirty-day mortality was 1.3% (2/162) for OR and 0% for EVAR (0/33) (P = not significant [NS]). There were 49 systemic complications (7 EVAR, 42 OR, P = NS) and 10 local complications (3 EVAR, 7 OR, P = NS). During follow-up, there were no conversions and no ruptures. Freedom from reinterventions at 5 years was 83.1% +/- 6.9% for EVAR and 95.3% +/- 1.8% for OR (P = 0.02). There were 26 deaths (3 EVAR, 23 OR); but no procedure or aneurysm-related death was confirmed after 30 days (cause unknown in 16 deaths, 62%). Survival rates at 1-year were 96.6% +/- 3.4% for EVAR and 97.4% +/- 1.3% for OR; 5-year rates were 86.9% +/- 7.2% +/- EVAR and 86.9% +/- 3.3% for OR (P = 0.69). Multivariate analysis revealed age (hazard ratio = 1.1 per year, P = .0496) and AAA size (hazard ratio = 13.8 per 1 cm, P = .03) were associated with death but EVAR vs OR was not (P = .23). CONCLUSION For repair of small AAAs, results of EVAR vs OR are not different at 5 years at a tertiary institution. Multicenter studies confirmed OR were not superior to observation in these patients. We predict the PIVOTAL study will conclude EVAR is not superior to observation.
Collapse
Affiliation(s)
- Purandath Lall
- Division of Vascular and Endovascular Surgery, Mayo Clinic, Rochester, Minnesota 55905, USA
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Armstrong PW. What do we know? Limitations of the two methods most commonly used to estimate the length of the prospective wait. Health Serv Manage Res 2009; 22:8-16. [PMID: 19182093 DOI: 10.1258/hsmr.2008.008014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Health service researchers, policy analysts and other commentators have overlooked the limitations of existing approaches to the estimation of waiting times. If urgent cases are given priority, there are no instances when census-based data can supply accurate estimates of the length of the prospective wait. But there are three occasions when event-based data supply accurate estimates of the prospective wait of those who chose to enrol and we can predict the direction of error when the relevant conditions are violated if we know whether the list was open or closed, and whether it grew in size or shrank. Without this additional information, we cannot determine whether the changes we observe over time or the differences we see between one list and the next are spurious or not. The period life-table provides a timely and bias-free alternative to the existing cross-sectional approaches for a modest increase in the complexity of calculation.
Collapse
Affiliation(s)
- Paul W Armstrong
- School of Health and Bioscience, University of East London, Romford Road, Stratford, London, UK.
| |
Collapse
|
18
|
Rutherford RB. Management of Abdominal Aortic Aneurysms: Which Risk Factors Play a Role in Decision-Making? Semin Vasc Surg 2008; 21:124-31. [DOI: 10.1053/j.semvascsurg.2008.05.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
19
|
Li ZY, U-King-Im J, Tang TY, Soh E, See TC, Gillard JH. Impact of calcification and intraluminal thrombus on the computed wall stresses of abdominal aortic aneurysm. J Vasc Surg 2008; 47:928-35. [DOI: 10.1016/j.jvs.2008.01.006] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 12/11/2007] [Accepted: 01/06/2008] [Indexed: 11/16/2022]
|
20
|
Frauenfelder T, Boutsianis E, Alkadhi H, Marincek B, Schertler T. [Simulation of blood flow within the abdominal aorta. Computational fluid dynamics in abdominal aortic aneurysms before and after interventions]. Radiologe 2007; 47:1021-8. [PMID: 17982738 DOI: 10.1007/s00117-007-1576-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The goal of numeric analysis of aortic blood flow is to evaluate the mechanisms leading to an aortic aneurysm with regard to the risk of a rupture and to describe the effect of interventional therapy. Numeric analysis is based on virtual models of vascular structures and the physical characteristics of the vessel wall, of blood as fluidum, and the blood flow. Using this information, numeric analysis solves the appropriate equations. The results can be displayed quantitatively and qualitatively. The results of numeric flow simulation show that in abdominal aortic aneurysms the wall pressure, which is of vital importance for the risk of rupture, depends on several factors, one being the location of the intraluminal thrombus. In models of aneurysms after stent grafting, numeric analysis can be used to evaluate factors leading to stent migration. Although numeric analysis of aortic blood flow still has several limitations, recent studies have shown that this method has the potential for improved estimation of the rupture risk of aortic aneurysms in the near future.
Collapse
Affiliation(s)
- T Frauenfelder
- Institut für Diagnostische Radiologie, Universitätsspital Zürich, Rämistrasse 100, Zürich, Switzerland.
| | | | | | | | | |
Collapse
|
21
|
Discussion. J Vasc Surg 2007. [DOI: 10.1016/j.jvs.2007.05.063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
22
|
Armstrong PA, Back MR, Bandyk DF, Lopez AS, Cannon SK, Johnson BL, Shames ML. Optimizing compliance, efficiency, and safety during surveillance of small abdominal aortic aneurysms. J Vasc Surg 2007; 46:190-5; discussion 195-6. [PMID: 17540533 DOI: 10.1016/j.jvs.2007.03.038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Accepted: 03/13/2007] [Indexed: 10/23/2022]
Abstract
BACKGROUND Outcome data documenting safety for observation of small abdominal aortic aneurysms (AAA 4.0 to 5.4 cm) are lacking outside of large clinical trials but requires near perfect patient compliance. This study describes a clinical pathway for AAA surveillance using a prospective database utilizing a nurse practitioner oversight to provide efficient use of clinic visits while maintaining a high level of patent participation. METHODS Over a 7-year period (June 1999 through June 2006), 334 patients were enrolled in an AAA surveillance pathway at our academic veterans hospital. To minimize patient travel, clinic visitation was reserved for an initial examination with patient education and for discussion of intervention options in patients demonstrating AAA growth (>5.4 cm or expansion >1 cm/yr) during follow-up. Biannual ultrasound or CT imaging was scheduled and results discussed (after physician review) via telephone or "same day" direct patient contact. An electronic database was used to update patient information and plan follow-up. RESULTS Compliance with the AAA surveillance pathway was achieved in 98.5% of patients, with only three patients (0.9%) lost to follow-up and two others (0.6%) choosing early repair at civilian institutions. At a mean interval of 29 months (+/-20 mo), surgical repair was performed in 225 (67%) patients by open (n = 143) or endovascular (n = 82) techniques for AAA growth to >5.4 cm (n = 219) or expansion by >1cm/yr (n = 6). One hundred six patients currently remain in surveillance. A single AAA rupture resulting in death occurred during surveillance (0.3%) and perioperative mortality (<60 days) was 0.9% in patients needing intervention for AAA growth. Cumulative aneurysm-related mortality was 0.9% for patients compliant with the AAA surveillance pathway. CONCLUSIONS Use of a prospectively-maintained surveillance database managed by a non-physician provider with a reliance on telephone contact resulted in a high degree of patient compliance, reduced unnecessary patient travel, and provided practical clinic use. Limited additional resources were needed to implement our pathway and a similar approach may prove useful for large volume hospital, clinic, or practice systems.
Collapse
Affiliation(s)
- Paul A Armstrong
- University of South Florida, Division of Vascular and Endovascular Surgery, Tampa, FL 33606, USA.
| | | | | | | | | | | | | |
Collapse
|
23
|
Schermerhorn M. Should usual criteria for intervention in abdominal aortic aneurysms be "downsized," considering reported risk reduction with endovascular repair? Ann N Y Acad Sci 2007; 1085:47-58. [PMID: 17182922 DOI: 10.1196/annals.1383.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Two randomized trials have demonstrated the safety of waiting until abdominal aortic aneurysm (AAA) diameter reaches 5.5 cm for repair in most patients. Other recent randomized trials have demonstrated lower perioperative mortality and morbidity with endovascular aneurysm repair (EVAR) compared to open surgery. Therefore, it is logical to assume that endovascular repair may change the appropriate threshold for intervention. However, endovascular repair is not as durable as open surgery and is associated with ongoing risks of rupture and reintervention. Decision analysis based on data available in 1998 showed that endovascular repair should not change the threshold for intervention. Since that time retrospective data have emerged to suggest that outcomes with endovascular repair are improved in smaller AAAs, although this may simply represent selection bias and the natural history of small AAAs. Randomized trials are appropriate to determine whether improved endovascular outcomes in small AAAs reduce late rupture and reintervention enough to justify early intervention in patients with appropriate anatomy. In the absence of data from these trials, the threshold for intervention should not be changed.
Collapse
Affiliation(s)
- Marc Schermerhorn
- Beth Israel Deaconess Medical Center, 110 Francis St. 5B, Boston, MA 02215, USA.
| |
Collapse
|
24
|
Björck M, Wanhainen A. Invited commentary for "From innumeracy to insight: the uncertainty of help versus harm in treatment of asymptomatic aortic aneurysms" by Legemate and Bossuyt. Eur J Vasc Endovasc Surg 2006; 32:624-6. [PMID: 16931072 DOI: 10.1016/j.ejvs.2006.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 07/06/2006] [Indexed: 11/30/2022]
Affiliation(s)
- M Björck
- Department of Surgical Sciences, Section of Vascular Surgery, Uppsala University Hospital, Uppsala, Sweden.
| | | |
Collapse
|
25
|
Hirsch AT, Haskal ZJ, Hertzer NR, Bakal CW, Creager MA, Halperin JL, Hiratzka LF, Murphy WRC, Olin JW, Puschett JB, Rosenfield KA, Sacks D, Stanley JC, Taylor LM, White CJ, White J, White RA, Antman EM, Smith SC, Adams CD, Anderson JL, Faxon DP, Fuster V, Gibbons RJ, Hunt SA, Jacobs AK, Nishimura R, Ornato JP, Page RL, Riegel B. ACC/AHA 2005 Practice Guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Peripheral Arterial Disease): endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation; National Heart, Lung, and Blood Institute; Society for Vascular Nursing; TransAtlantic Inter-Society Consensus; and Vascular Disease Foundation. Circulation 2006; 113:e463-654. [PMID: 16549646 DOI: 10.1161/circulationaha.106.174526] [Citation(s) in RCA: 2167] [Impact Index Per Article: 120.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
26
|
Hirsch AT, Haskal ZJ, Hertzer NR, Bakal CW, Creager MA, Halperin JL, Hiratzka LF, Murphy WR, Olin JW, Puschett JB, Rosenfield KA, Sacks D, Stanley JC, Taylor LM, White CJ, White J, White RA, Antman EM, Smith SC, Adams CD, Anderson JL, Faxon DP, Fuster V, Gibbons RJ, Halperin JL, Hiratzka LF, Hunt SA, Jacobs AK, Nishimura R, Ornato JP, Page RL, Riegel B. ACC/AHA 2005 Guidelines for the Management of Patients With Peripheral Arterial Disease (Lower Extremity, Renal, Mesenteric, and Abdominal Aortic): A Collaborative Report from the American Association for Vascular Surgery/Society for Vascular Surgery,⁎Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Peripheral Arterial Disease). J Am Coll Cardiol 2006. [DOI: 10.1016/j.jacc.2006.02.024] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
27
|
Surgical Treatment of Abdominal Aortic Aneurysms. Vasc Med 2006. [DOI: 10.1016/b978-0-7216-0284-4.50045-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
28
|
Scotti CM, Shkolnik AD, Muluk SC, Finol EA. Fluid-structure interaction in abdominal aortic aneurysms: effects of asymmetry and wall thickness. Biomed Eng Online 2005; 4:64. [PMID: 16271141 PMCID: PMC1298313 DOI: 10.1186/1475-925x-4-64] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Accepted: 11/04/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Abdominal aortic aneurysm (AAA) is a prevalent disease which is of significant concern because of the morbidity associated with the continuing expansion of the abdominal aorta and its ultimate rupture. The transient interaction between blood flow and the wall contributes to wall stress which, if it exceeds the failure strength of the dilated arterial wall, will lead to aneurysm rupture. Utilizing a computational approach, the biomechanical environment of virtual AAAs can be evaluated to study the affects of asymmetry and wall thickness on this stress, two parameters that contribute to increased risk of aneurysm rupture. METHODS Ten virtual aneurysm models were created with five different asymmetry parameters ranging from beta = 0.2 to 1.0 and either a uniform or variable wall thickness to study the flow and wall dynamics by means of fully coupled fluid-structure interaction (FSI) analyses. The AAA wall was designed to have a (i) uniform 1.5 mm thickness or (ii) variable thickness ranging from 0.5-1.5 mm extruded normally from the boundary surface of the lumen. These models were meshed with linear hexahedral elements, imported into a commercial finite element code and analyzed under transient flow conditions. The method proposed was then compared with traditional computational solid stress techniques on the basis of peak wall stress predictions and cost of computational effort. RESULTS The results provide quantitative predictions of flow patterns and wall mechanics as well as the effects of aneurysm asymmetry and wall thickness heterogeneity on the estimation of peak wall stress. These parameters affect the magnitude and distribution of Von Mises stresses; varying wall thickness increases the maximum Von Mises stress by 4 times its uniform thickness counterpart. A pre-peak systole retrograde flow was observed in the AAA sac for all models, which is due to the elastic energy stored in the compliant arterial wall and the expansion force of the artery during systole. CONCLUSION Both wall thickness and geometry asymmetry affect the stress exhibited by a virtual AAA. Our results suggest that an asymmetric AAA with regional variations in wall thickness would be exposed to higher mechanical stresses and an increased risk of rupture than a more fusiform AAA with uniform wall thickness. Therefore, it is important to accurately reproduce vessel geometry and wall thickness in computational predictions of AAA biomechanics.
Collapse
Affiliation(s)
- Christine M Scotti
- Biomedical Engineering Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Alexander D Shkolnik
- Department of Mathematical Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Satish C Muluk
- Division of Vascular Surgery, Allegheny General Hospital, Pittsburgh, Pennsylvania, USA
| | - Ender A Finol
- Institute for Complex Engineered Systems and Biomedical Engineering Department, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| |
Collapse
|
29
|
Ghansah JN, Murphy JT. Complications of major aortic and lower extremity vascular surgery. Semin Cardiothorac Vasc Anesth 2005; 8:335-61. [PMID: 15583793 DOI: 10.1177/108925320400800406] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Atheromatous disease and invasive intervention of the aortoiliac and distal arteries are common. Morbidity and mortality have been reduced through understanding and management of patient risk factors. Complications of this form of treatment affect all organ systems; mortality is most frequently caused by a cardiovascular complication (eg, myocardial infarction). Infection, leading to aortoenteric fistula is a dreaded complication, and paraplegia, though rare, is a devastating outcome. Multiorgan failure and death may result from a systemic inflammatory response syndrome. Vascular surgery for infrainguinal disease also has a significant cardiovascular complication rate. Resulting complications may affect all organs; loss of an extremity may occur. The first part of this article reviews perioperative and postoperative complications of open aortic repair and lower-extremity revascularization and addresses the issue of regional anesthesia for major vascular surgery. The second part reviews endovascular aortic repair (EVAR). EVAR is a new intervention that combines surgery and radiology. Complications of EVAR are similar to open repair, but early results suggest they may be less frequent. New technology leads to new complications; endoleaks, migration of the endoprosthesis, and surgical conversion are unique to EVAR. The benefits of EVAR may be less blood loss, shorter hospitalization, and less cardiovascular stress; the risks may be aneurysm recurrence, prolonged surveillance and repeated secondary procedures. The development of EVAR, the complications, and the anesthesia-related concerns of EVAR, including its use in management of acute abdominal aortic aneurysm are reviewed.
Collapse
Affiliation(s)
- J Nana Ghansah
- Department of Anesthesiology, University of Kentucky, College of Medicine, H A Chandler Medical Center, Lexington, KY 40536-0293, USA
| | | |
Collapse
|
30
|
Shakibaie F, Hall JC, Norman PE. Indications for operative management of abdominal aortic aneurysms. ANZ J Surg 2004; 74:470-6. [PMID: 15191485 DOI: 10.1111/j.1445-1433.2004.03033.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The increasing incidence of abdominal aortic aneurysms, along with the more frequent use of screening techniques, has resulted in greater numbers of patients with small abdominal aortic aneurysms. The questions of frequency of surveillance and timing of intervention are the two most controversial issues faced by surgeons dealing with this condition. Most management decisions are based on the size of the aneurysm but other factors must also be considered. This review makes recommendations on the management of small abdominal aortic aneurysms according to the current available evidence.
Collapse
Affiliation(s)
- Faraz Shakibaie
- School of Surgery and Pathology, The University of Western Australia, Perth, Western Australia, Australia
| | | | | |
Collapse
|
31
|
Branchereau A. Small Aortic Aneurysms: Is Evidence Evident? Eur J Vasc Endovasc Surg 2004; 27:363-5. [PMID: 15015184 DOI: 10.1016/j.ejvs.2004.01.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2004] [Indexed: 11/26/2022]
Affiliation(s)
- A Branchereau
- Faculté de Médecine de Marseille, Université de la Méditerranée, Assistance Publique Hôpitaux de Marseille-Hôpital La Timone, Département de Chirurgie Vasculaire, Marseille, France
| |
Collapse
|
32
|
Brewster DC, Cronenwett JL, Hallett JW, Johnston KW, Krupski WC, Matsumura JS. Guidelines for the treatment of abdominal aortic aneurysms. Report of a subcommittee of the Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. J Vasc Surg 2003; 37:1106-17. [PMID: 12756363 DOI: 10.1067/mva.2003.363] [Citation(s) in RCA: 508] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Decision-making in regard to elective repair of abdominal aortic aneurysms (AAA) requires careful assessment of factors that influence rupture risk, operative mortality, and life expectancy. Individualized consideration of these factors in each patient is essential, and the role of patient preference is of increasing importance. It is not possible or appropriate to recommend a single threshold diameter for intervention which can be generalized to all patients. Based upon the best available current evidence, 5.5 cm is the best threshold for repair in an "average" patient. However, subsets of younger, good-risk patients or aneurysms at higher rupture risk may be identified in whom repair at smaller sizes is justified. Conversely, delay in repair until larger diameter may be best for older, higher-risk patients, especially if endovascular repair is not possible. Intervention at diameter <5.5 cm appears indicated in women with AAA. If a patient has suitable anatomy, endovascular repair may be considered, and it is most advantageous for older, higher-risk patients or patients with a hostile abdomen or other technical factors that may complicate standard open repair. With endovascular repair, perioperative morbidity and recovery time are clearly reduced; however, there is a higher reintervention rate, increased surveillance burden, and a small but ongoing risk of AAA rupture. There is no justification at present for different indications for endovascular repair, such as earlier treatment of smaller AAA. Until long-term outcome of endoluminal repair is better defined and results of randomized trials available, the choice between endovascular and open repair will continue to rely heavily on patient preference.
Collapse
|
33
|
Abstract
The purpose of this chapter is to provide a brief overview of the current place of open surgical repair for abdominal aortic aneurysms with respect to the factors influencing clinical decision-making, the operative techniques most frequently used, and some of the complications commonly encountered in the postoperative period.
Collapse
Affiliation(s)
- Murray L Shames
- Section of Vascular Surgery, Washington University School of Medicine, 9901 Wohl Hospital, 4960 Children's Place, St. Louis, MO 63110, USA
| | | |
Collapse
|
34
|
|
35
|
Rockman CB, Lamparello PJ, Adelman MA, Jacobowitz GR, Therff S, Gagne PJ, Nalbandian M, Weiswasser J, Landis R, Rosen R, Riles TS. Aneurysm morphology as a predictor of endoleak following endovascular aortic aneurysm repair: do smaller aneurysm have better outcomes? Ann Vasc Surg 2002; 16:644-51. [PMID: 12183772 DOI: 10.1007/s10016-001-0200-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Since the Food and Drug Administrations' approval of endovascular devices for abdominal aortic aneurysm (AAA) repair, clinicians have been relaxing the strict inclusion criteria present during the clinical trials. Although the long-term natural history of endoleaks remains unclear, attachment site leaks (type I) are believed to represent an ongoing risk for future rupture. We reviewed our experience with endovascular AAA repair to elucidate factors that predispose toward the development of endoleaks and found that larger AAAs are significantly more likely to have a short proximal neck and severe proximal angulation. These factors likely contribute to the significantly increased rate of type I endoleaks that occurred after endovascular repair of large AAAs. Small AAAs (<5) had the lowest rate of endoleaks overall (8.3%) and of type I endoleaks in particular (0%). We conclude that AAA size and morphology can be used to predict which aneurysms will experience attachment site endoleaks in their course; AAAs from 4.5 to 5 cm in diameter may be particularly well suited for endovascular repair in this regard.
Collapse
Affiliation(s)
- Caron B Rockman
- Division of Vascular Surgery, New York University Medical Center, New York, NY 10016, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
|
37
|
Di Martino ES, Guadagni G, Fumero A, Ballerini G, Spirito R, Biglioli P, Redaelli A. Fluid-structure interaction within realistic three-dimensional models of the aneurysmatic aorta as a guidance to assess the risk of rupture of the aneurysm. Med Eng Phys 2001; 23:647-55. [PMID: 11755809 DOI: 10.1016/s1350-4533(01)00093-5] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Abdominal aortic aneurysm (AAA) disease is a degenerating process whose ultimate event is the rupture of the vessel wall. Rupture occurs when the stresses acting on the wall rise above the strength of the AAA wall tissue. The complex mechanical interaction between blood flow and wall dynamics in a three dimensional custom model of a patient AAA was studied by means of computational coupled fluid-structure interaction analysis. Real 3D AAA geometry is obtained from CT scans image processing. The results provide a quantitative local evaluation of the stresses due to local structural and fluid dynamic conditions. The method accounts for the complex geometry of the aneurysm, the presence of a thrombus and the interaction between solid and fluid. A proven clinical efficacy may promote the method as a tool to determine factual aneurysm risk of rupture and aid the surgeon to refer elective surgery patients.
Collapse
Affiliation(s)
- E S Di Martino
- Department of Bioengineering, Politecnico of Milano, Milan, Italy
| | | | | | | | | | | | | |
Collapse
|
38
|
Crouch DS, McLafferty RB, Karch LA, Mattos MA, Ramsey DE, Henretta JP, Hodgson KJ, Sumner DS. A prospective study of discharge disposition after vascular surgery. J Vasc Surg 2001; 34:62-8. [PMID: 11436076 DOI: 10.1067/mva.2001.115597] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The purpose of this study was to determine what factors are predictive of a decline in independent living after vascular surgery during recovery. METHODS Demographics, risk factors, operations, complications, wound status, and discharge disposition for all patients admitted to a tertiary vascular surgery service for any surgical procedure were prospectively recorded at the time of discharge. The declining order of dispositions at discharge were home (no professional assistance), home (professional assistance), rehabilitation facility, and skilled nursing facility. RESULTS Over a 15-month period, 380 patients underwent 442 primary operations. Primary operations included 74 (17%) carotid procedures, 38 (8%) aortic procedures, 186 (42%) extremity revascularizations, 29 (7%) major amputations, 45 (10%) minor amputations, and 70 (16%) other. There were 148 (33%) complications and 85 (20%) subsequent operations (same hospitalization); 159 (36%) open wounds occurred. Forty-six percent of the patients were discharged to home (no professional assistance), 28% to home (professional assistance), 3% to a rehabilitation facility, and 18% to a skilled nursing facility; 5% died. At discharge, 51% of patients required professional assistance, 39% had a decline in disposition, and 12% went from home (+/- professional assistance) to a facility. By multivariate regression analysis, a hospital stay more than 6 days, emergency operation, open operative wound, systemic complications, and minor amputation were significantly associated (P <.001) with a decline in disposition at discharge (odds ratios: 5.5, 3.7, 3.6, 3.6, and 2.8, respectively). CONCLUSIONS Prospective study reveals that a large proportion of patients (39%) had a decline in disposition after vascular surgery. A hospital stay more than 6 days, emergency operation, open operative wound, systemic complications, and minor amputation were strong independent predictors of decline. This information suggests modifications in treatment strategies may improve independent living status after vascular surgery and decrease the intense use of extended care resources required for this patient population during recovery.
Collapse
Affiliation(s)
- D S Crouch
- Division of Vascular Surgery, Southern Illinois University, School of Medicine, Springfield, 62794-9638, USA
| | | | | | | | | | | | | | | |
Collapse
|