Patient-specific finite element simulation of peripheral artery percutaneous transluminal angioplasty to evaluate the procedure outcome without stent implantation.

The purpose of this work is to present a patient-specific (PS) modeling approach for simulating percutaneous transluminal angioplasty (PTA) endovascular treatment and assessing the balloon sizing influence on short-term outcomes in peripheral arteries, i.e. without stent implantation. Two 3D PS stenosed femoral artery models, one with a dominant calcified atherosclerosis while the other with a lipidic plaque, were generated from pre-operative computed tomography angiography images. Elastoplastic constitutive laws were implemented within the plaque and artery models. Implicit finite element method (FEM) was used to simulate the balloon inflation and deflation for different sizings. Besides vessel strains, results were mainly evaluated in terms of the elastic recoil ratio (ERR) and lumen gain ratio (LGR) attained immediately after PTA. Higher LGR values were shown within the stenosed region of the lipidic patient. Simulated results also showed a direct and quantified correlation between balloon sizing and LGR and ERR for both patients after PTA, with a more significant influence on the lumen gain. The max principal strain values in the outer arterial wall increased at higher balloon sizes during inflation as well, with higher rates of increase when the plaque was calcified. Results show that our model could serve in finding a compromise for each stenosis type: maximizing the achieved lumen gain after PTA, but at the same time without damaging the arterial tissue. The proposed methodology can serve as a step toward a clinical decision support system to improve angioplasty balloon sizing selection prior to the surgery.

Stretched reconstruction based on 2D freehand ultrasound for peripheral artery imaging.

PURPOSE: Endovascular revascularization is becoming the established first-line treatment of peripheral artery disease (PAD). Ultrasound (US) imaging is used pre-operatively to make the first diagnosis and is often followed by a CT angiography (CTA). US provides a non-invasive and non-ionizing method for the visualization of arteries and lesion(s). This paper proposes to generate a 3D stretched reconstruction of the femoral artery from a sequence of 2D US B-mode frames. METHODS: The proposed method is solely image-based. A Mask-RCNN is used to segment the femoral artery on the 2D US frames. In-plane registration is achieved by aligning the artery segmentation masks. Subsequently, a convolutional neural network (CNN) predicts the out-of-plane translation. After processing all input frames and re-sampling the volume according to the vessel's centerline, the whole femoral artery can be visualized on a single slice of the resulting stretched view. RESULTS: 111 tracked US sequences of the left or right femoral arteries have been acquired on 18 healthy volunteers. fivefold cross-validation was used to validate our method and achieve an absolute mean error of 0.28 ± 0.28 mm and a median drift error of 8.98%. CONCLUSION: This study demonstrates the feasibility of freehand US stretched reconstruction following a deep learning strategy for imaging the femoral artery. Stretched views are generated and can give rich diagnosis information in the pre-operative planning of PAD procedures. This visualization could replace traditional 3D imaging in the pre-operative planning process, and during the pre-operative diagnosis phase, to identify, locate, and size stenosis/thrombosis lesions.

Fusion Imaging with a Mobile C-Arm for Peripheral Arterial Disease.

BACKGROUND: Fusion imaging makes it possible to improve endovascular procedures and is mainly used in hybrid rooms for aortic procedures. The objective of this study was to evaluate the feasibility of fusion imaging for femoropopliteal endovascular procedures with a mobile flat plane sensor and dedicated software to assist endovascular navigation. MATERIALS AND METHODS: Between May and December 2017, 41 patients requiring femoropopliteal endovascular revascularization were included. Interventions were carried out in a conventional surgical room equipped with a mobile plane sensor (Cios Alpha, Siemens). The numerical video stream was transmitted to an angionavigation station (EndoNaut (EN), Therenva). The software created an osseous and arterial panorama of the treated limb from the angiographies carried out at the beginning of procedure. After each displacement of the table, the software relocated the current image on the osseous panorama, with 2D-2D resetting, and amalgamated the mask of the arterial panorama. The success rates of creation of osseous and arterial panorama and the success of relocation were evaluated. The data concerning irradiation, the volume of contrast (VC) injected, and operative times were recorded. RESULTS: Osseous panoramas could be automatically generated for the 41 procedures, without manual adjustment in 33 cases (80.5%). About 35 relocations based on a 2D-2D resetting could be obtained in the 41 procedures, with a success rate of 85%. The causes of failure were a change in table height or arch angulation. The average duration of intervention was 74.5 min. The irradiation parameters were duration of fluoroscopy 17.8 ± 13.1 min, air kerma 80.5 ± 68.4 mGy, and dose area product 2140 ± 1599 µGy m2. The average VC was 24.5 ± 14 mL. CONCLUSIONS: This preliminary study showed that fusion imaging is possible in a nonhybrid room for peripheral procedures. Imagery of mobile C-arms can be improved for femoropopliteal endovascular procedures without heavy equipment. These imagery tools bring an operative comfort and could probably reduce irradiation and the injected VC. The clinical benefit must be evaluated in more patients in a randomized comparative study with a rigorous methodology.

Use of Numerical Simulation to Predict Iliac Complications During Placement of An Aortic Stent Graft.

BACKGROUND: During endovascular aneurysm repair (EVAR), complex iliac anatomy is a source of complications such as unintentional coverage of the hypogastric artery. The aim of our study was to evaluate ability to predict coverage of the hypogastric artery using a biomechanical model simulating arterial deformations caused by the delivery system. METHODS: The biomechanical model of deformation has been validated by many publications. The simulations were performed on 38 patients included retrospectively, for a total of 75 iliac arteries used for the study. On the basis of objective measurements, two groups were formed: one with "complex" iliac anatomy (n = 38 iliac arteries) and the other with "simple" iliac anatomy (n = 37 iliac arteries). The simulation enabled measurement of the lengths of the aorta and the iliac arteries once deformed by the device. Coverage of the hypogastric artery was predicted if the deformed renal/iliac bifurcation length (Lpre) was less than the length of the implanted device (Lstent-measured on the postoperative computed tomography [CT]) and nondeformed Lpre was greater than Lstent. RESULTS: Nine (12%) internal iliac arteries were covered unintentionally. Of the coverage attributed to perioperative deformations, 1 case (1.3%) occurred with simple anatomy and 6 (8.0%) with complex anatomy (P = 0.25). All cases of unintentional coverage were predicted by the simulation. The simulation predicted hypogastric coverage in 35 cases (46.7%). There were therefore 26 (34.6%) false positives. The simulation had a sensitivity of 100% and a specificity of 60.6%. On multivariate analysis, the factors significantly predictive of coverage were the iliac tortuosity index (P = 0.02) and the predicted margin between the termination of the graft limb and the origin of the hypogastric artery in nondeformed (P = 0.009) and deformed (P = 0.001) anatomy. CONCLUSIONS: Numerical simulation is a sensitive tool for predicting the risk of hypogastric coverage during EVAR and allows more precise preoperative sizing. Its specificity is liable to be improved by using a larger cohort.

Fusion Imaging for EVAR with Mobile C-arm.

BACKGROUND: Fusion imaging is a technique that facilitates endovascular navigation but is only available in hybrid rooms. The goal of this study was to evaluate the feasibility of fusion imaging with a mobile C-arm in a conventional operating room through the use of an angionavigation station. METHODS: From May 2016 to June 2017, the study included all patients who underwent an aortic stent graft procedure in a conventional operating room with a mobile flat-panel detector (Cios Alpha, Siemens) connected to an angionavigation station (EndoNaut, Therenva). The intention was to perform preoperative 3D computerized tomography/perioperative 2D fluoroscopy fusion imaging using an automatic registration process. Registration was considered successful when the software was able to correctly overlay preoperative 3D vascular structures onto the fluoroscopy image. For EVAR, contrast dose, operation time, and fluoroscopy time (FT) were compared with those of a control group drawn from the department's database who underwent a procedure with a C-arm image intensifier. RESULTS: The study included 54 patients, and the procedures performed were 49 EVAR, 2 TEVAR, 2 IBD, and 1 FEVAR. Of the 178 registrations that were initialized, it was possible to use the fusion imaging in 170 cases, that is, a 95.5% success rate. In the EVAR comparison, there were no difference with the control group (n = 103) for FT (21.9 ± 12 vs. 19.5 ± 13 min; P = 0.27), but less contrast agent was used in the group undergoing a procedure with the angionavigation station (42.3 ± 22 mL vs. 81.2 ± 48 mL; P < 0.001), and operation time was shorter (114 ± 44 vs. 140.8 ± 38 min; P < 0.0001). CONCLUSIONS: Fusion imaging is feasible with a mobile C-arm in a conventional operating room and thus represents an alternative to hybrid rooms. Its clinical benefits should be evaluated in a randomized series, but our study already suggests that EVAR procedures might be facilitated with an angionavigation system.

A hybrid image fusion system for endovascular interventions of peripheral artery disease.

PURPOSE: Interventional endovascular treatment has become the first line of management in the treatment of peripheral artery disease (PAD). However, contrast and radiation exposure continue to limit the feasibility of these procedures. This paper presents a novel hybrid image fusion system for endovascular intervention of PAD. We present two different roadmapping methods from intra- and pre-interventional imaging that can be used either simultaneously or independently, constituting the navigation system. METHODS: The navigation system is decomposed into several steps that can be entirely integrated within the procedure workflow without modifying it to benefit from the roadmapping. First, a 2D panorama of the entire peripheral artery system is automatically created based on a sequence of stepping fluoroscopic images acquired during the intra-interventional diagnosis phase. During the interventional phase, the live image can be synchronized on the panorama to form the basis of the image fusion system. Two types of augmented information are then integrated. First, an angiography panorama is proposed to avoid contrast media re-injection. Information exploiting the pre-interventional computed tomography angiography (CTA) is also brought to the surgeon by means of semiautomatic 3D/2D registration on the 2D panorama. Each step of the workflow was independently validated. RESULTS: Experiments for both the 2D panorama creation and the synchronization processes showed very accurate results (errors of 1.24 and [Formula: see text] mm, respectively), similarly to the registration on the 3D CTA (errors of [Formula: see text] mm), with minimal user interaction and very low computation time. First results of an on-going clinical study highlighted its major clinical added value on intraoperative parameters. CONCLUSION: No image fusion system has been proposed yet for endovascular procedures of PAD in lower extremities. More globally, such a navigation system, combining image fusion from different 2D and 3D image sources, is novel in the field of endovascular procedures.

Influencing factors of sac shrinkage after endovascular aneurysm repair.

OBJECTIVE: Sac shrinkage is considered a reliable surrogate marker of success after endovascular aneurysm repair (EVAR). Whereas sac shrinkage is the best expected outcome, predictive factors of sac shrinkage remain unclear. The aim of this study was to identify the role of preoperative and postoperative influencing factors of sac reduction after EVAR. METHODS: Online searches across MEDLINE, Embase, and Cochrane Library medical databases were simultaneously performed. Study effects were pooled using a random-effects model, and forest plots were generated for every potential influencing factor. RESULTS: A total of 24 studies with 14,754 patients were included (mean age, 73.4 years; 76% male). At a mean follow-up of 24 months, the pooled shrinkage proportion was 47%. Random-effects meta-analysis revealed that renal impairment (odds ratio [OR], 0.74; 95% confidence interval [CI], 0.57-0.96), type I endoleaks (OR, 0.17; 95% CI, 0.08-0.39), type II endoleaks (OR, 0.21; 95% CI, 0.14-0.33), and combined type I and type II endoleaks (OR, 0.32; 95% CI, 0.22-0.47) were found to prevent sac shrinkage, whereas hypercholesterolemia (OR, 1.24; 95% CI, 1.02-1.51) and smoking (OR, 1.32; 95% CI, 1.17-1.49) have a significant positive impact on sac shrinkage. In addition, there was a trend toward the association between shrinkage and statin therapy (OR, 4.07; 95% CI, 1.02-16.32) and nearly significant negative impacts of coronary artery disease (OR, 0.84; 95% CI, 0.70-1.01), diabetes (OR, 0.79; 95% CI, 0.60-1.04), and sac thrombus (OR, 0.88; 95% CI, 0.77-1.01) on sac shrinkage. CONCLUSIONS: In this large meta-analysis of patients undergoing EVAR, we found that several comorbidity and postoperative factors were associated with postoperative sac shrinkage. These findings may contribute to a better understanding of the shrinkage process of patients undergoing EVAR.

Generic thrombus segmentation from pre- and post-operative CTA.

PURPOSE: Abdominal aortic aneurysm (AAA) is a localized, permanent and irreversible enlargement of the artery, with the formation of thrombus into the inner wall of the aneurysm. A precise patient-specific segmentation of the thrombus is useful for both the pre-operative planning to estimate the rupture risk, and for post-operative assessment to monitor the disease evolution. This paper presents a generic approach for 3D segmentation of thrombus from patients suffering from AAA using computed tomography angiography (CTA) scans. METHODS: A fast and versatile thrombus segmentation approach has been developed. It is composed of initial centerline detection and aorta lumen segmentation, an optimized pre-processing stage and the use of a 3D deformable model. The approach has been designed to be very generic and requires minimal user interaction. The proposed method was tested on different datasets with 145 patients overall, including pre- and post-operative CTAs, abdominal aorta and iliac artery sections, different calcification degrees, aneurysm sizes and contrast enhancement qualities. RESULTS: The thrombus segmentation approach showed very accurate results with respect to manual delineations for all datasets ([Formula: see text] and [Formula: see text] for abdominal aorta sections on pre-operative CTA, iliac artery sections on pre-operative CTAs and aorta sections on post-operative CTA, respectively). Experiments on the different patient and image conditions showed that the method was highly versatile, with no significant differences in term of precision. Comparison with the level-set algorithm also demonstrated the superiority of the 3D deformable model. Average processing time was [Formula: see text]. CONCLUSION: We presented a near-automatic and generic thrombus segmentation algorithm applicable to a large variability of patient and imaging conditions. When integrated in an endovascular planning system, our segmentation algorithm shows its compatibility with clinical routine and could be used for pre-operative planning and post-operative assessment of endovascular procedures.

Evaluation by Magnetic Resonance Imaging of Silent Brain Infarcts in Preoperative and Postoperative Asymptomatic Carotid Surgery.

BACKGROUND: To report the prevalence of silent brain infarcts (SBI) at magnetic resonance imaging (MRI) before and after surgery for asymptomatic high grade carotid stenosis. METHODS: This is a single center retrospective observational study. Asymptomatic patients who underwent carotid endarterectomy between October 2012 and October 2014 were included. The preoperative assessment included a Doppler and a computed tomographic (CT) scan dating less than 3 months. A neurological examination was performed during the anesthesia consultation and in the 15 days before surgery. An MRI angiography was performed the day before and 3 days after surgery and was analyzed by an independent neuroradiologist. Preoperative analysis focused on the presence of ischemic events at MRI. The type of plaque, the supra aortic trunk lesions, and the quality of the circle of Willis were analyzed using Doppler and CT scanning. Postoperatively, we searched for signs of postoperative ischemic events at MRI. RESULTS: Forty-one patients were included (85.4% of men), and the mean age was 72.4 ± 8.3 years. We noted 7 (17.1%) contralateral stenoses (>50%) and 2 (4.9%) contralateral thromboses, 6 (14.6%) vertebral stenoses, and 7 (17.1%) abnormalities of the circle of Willis. The morphological analysis described 6 unstable plaques including 4 ulcerated, 1 pseudodissection, and 1 intraplaque hemorrhage. Preoperatively, we noted the presence of 21 (51.2%) ischemic lesions including 9 (21.9%) multiple lacunar ischemic events and 12 (29.3%) silent arterial territory infarcts. Eversion was performed for all patients except for 6 (14.6%), for whom a bypass was necessary. No deaths or major complications were observed in the 30 postoperative days. Postoperatively, MRI showed 3 (7.3%) asymptomatic recent ischemic strokes, 1 ipsilateral middle cerebral artery (MCA) stroke, and 2 contralateral (cerebellar and MCA) strokes. CONCLUSIONS: Patients with asymptomatic significant carotid stenosis show many preoperative SBI indicating a significant embolic risk. It is difficult to conclude about intraoperative embolic risk, but we hope that more data could demonstrate the importance of MRI for the preoperative evaluation of carotid plaques and brain parenchyma, to identify high-risk embolic patients.

Interest of fusion imaging and modern navigation tools with hybrid rooms in endovascular aortic procedures.

Because of the emergence of hybrid operating rooms, cone-beam CT scans (CBCT) allow new intraoperative imaging to be produced. Image fusion (3D preoperative CT scan overlaid onto 2D live fluoroscopy image) is the most popular application and makes it possible to navigate throughout the aorta and its branches without having to make use of an additional injection, and allows a reduction to be achieved in the quantity of contrast medium and irradiation required during complex procedures. Planning-oriented software available in hybrid rooms makes it possible to adjust to the patient and the nature of the procedure, the information that is relevant during the operation. CBCT can also be used as a diagnostic tool at the end of a procedure for the detection of endoleaks and could replace routine CT scans made during the first month following the procedure, indirectly contributing again to a reduction of X-ray and contrast agent doses.

Systematic Review and Meta-Analysis of Preoperative Risk Factors of Type II Endoleaks after Endovascular Aneurysm Repair.

BACKGROUND: Type II endoleaks (T2Es) remain the Achilles heel of endovascular aneurysm repair (EVAR), involving a close follow-up and sometimes leading to reintervention. Identifying risk factors impacting T2Es is of concern to improve decision making and optimize follow-up. However, it has led to contradictory results, with supporting evidence for the majority of factors being weak. METHODS: A systematic review and meta-analysis was conducted to study risk factors of T2Es following EVAR to identify risk factors and measure their dedicated strength of association. Using a literature search of MEDLINE, EMBASE, and the Cochrane Library, 31 retrospective studies including a total of 15,793 patients were identified and fulfilled the strict specified inclusion criteria. Random-effects meta-analysis was conducted for each factor to combine effect estimate across studies. A total of 21 factors related to demography, preoperative treatment, comorbidity, and morphology were statistically pooled. RESULTS: On the basis of the pooled odds ratios and their 95% confidence intervals, patency of aortic side branches, represented by the patency of the inferior mesenteric artery, lumbar arteries, or total number of aortic side branches, were found to be significant harmful risk factors of T2Es. Women were also found to have nearly significant higher risk of developing T2Es than men. On the contrary, the following were found to have a significant protective role: smoking, peripheral artery disease, and thrombus load, represented by the maximum thickness at the maximum aneurysm diameter, the presence of circumferential thrombus, or the presence of thrombus at the level of inferior mesenteric artery. CONCLUSION: Identifying significant risk factors of development of T2Es is mandatory to improve decision making and optimize surveillance planning in EVAR.

Predictive Models of Complications after Endovascular Aortic Aneurysm Repair.

BACKGROUND: The risk of long-term complications after endovascular aneurysm repair (EVAR) is still higher than open surgery and is a critical issue. This study aims to make available reliable statistical predictive models of complications after EVAR. METHODS: Two hundred and thirteen patients who underwent EVAR between 2002 and 2012 were included in this study. The preoperative computed tomography scans were analyzed with a dedicated workstation to provide spatially correct 3-dimensional data. Age, gender, operation-related factors, and 21 morphologic variables were measured and included in the analyses. Five postoperative outcomes were studied. After an initial selection of predictors based on univariate analysis, binomial logistic regression models were proposed for each outcome. The ability to predict each outcome was assessed with receiver operating characteristic curves considering that an area under the curve (AUC) > 0.70 is generally considered sufficiently accurate. RESULTS: The mean age was 74.8 ± 8.6 years with a mean follow-up of 43.8 ± 22.1 months. Respectively, rates and risk factors of each outcome were 25.3% (n = 51) for abdominal aortic aneurysm (AAA) enlargement (age, number of patent sac branches, iliac calcifications and tortuosity, aneurysmal thrombus), 7% (n = 15) for type IA endoleak (neck calcification and AAA diameter), 3.7% (n = 8) for type IB endoleak (iliac tortuosity, AAA diameter, neck thrombus), 19.8% (n = 40) for type II endoleak (female, number of patent sac branches), and 25.9% (n = 55) for reintervention from any cause (neck calcification). The risk associated to each outcome can be calculated with a combination of these different preoperative variables. AUC for each outcome were 79.6% for AAA enlargement, 70.4% for reintervention, 81.3% for type IA endoleak, 92.3% for type IB endoleak, 70.6% for type II endoleak. CONCLUSIONS: This study shows that an exhaustive description of the preoperative anatomy before EVAR is a powerful and reliable tool to predict the risk of developing the most common complications after EVAR.

Endovascular Treatment of Infrarenal Aneurysms: Comparison of the Results of Second- and Third-Generation Stent Grafts.

BACKGROUND: The stent grafts used for endovascular abdominal aortic repair (EVAR) profited from many technological changes since their appearance. The objective of this study was to compare the medium-term results of the second- and third-generation stent grafts. METHODS: Three hundred thirty-four patients treated by EVAR between 2005 and 2013 were included in this retrospective study. Demographic, anatomical, perioperative, and follow-up data were collected in a prospective way in an electronic database and compared between 2 groups. The preoperative angio-computed tomographies were all analyzed in depth on a suitable three-dimensional work station. Group 1 (n = 219) represented the patients treated by second-generation stent grafts (Medtronic Talent(®), Cook Medical Zenith Flex(®), Vascutek-Terumo Anaconda(®), Gore Excluder low-porosity(®)) and group 2 (n = 115) represented the patients treated with third-generation stent grafts (Medtronic Enduring I and II(®), Cook Medical Zenith LP(®), Gore Excluder C3(®)). RESULTS: The mean follow-up was 42.4 ± 26.8 months with a longer duration in group 1 (52.4 ± 27.2 vs. 23.2 ± 10.9 months, P < 0.0001). The patients of group 2 had significantly more risk factors and cardiovascular comorbidities (coronary disease, tobacco addiction, dyslipidemia, peripheral arterial disease, chronic renal insufficiency). Anatomical characteristics were similar in the 2 groups, in particular regarding the iliac arteries which were significantly more calcified and had a smaller diameter in group 2. The rate of perioperative complications was similar in the 2 groups, in particular for complications related to the iliac axes (3.7% vs. 2.6%, P = 0.96). During the follow-up, there was no significant difference between the 2 groups in the rates of survival, reinterventions, or endoleaks and the progression of the aneurysmal sac. CONCLUSIONS: This study shows that third-generation stent grafts allow results comparable with those of the second-generation stent grafts in spite of more complex iliac anatomies. These results make it possible to expand the indications of EVAR to patients presenting more cardiovascular comorbidities without increasing the risk of complications in the short and medium term.

Sealing zones have a greater influence than iliac anatomy on the occurrence of limb occlusion following endovascular aortic aneurysm repair.

Limb occlusion is a well-known complication following endovascular aortic aneurysm repair (EVAR), and it very often leads to reoperation. The aim of this study is to identify predictive factors for limb occlusion following EVAR. Two hundred and twenty-four patients undergoing EVAR between 2004 and 2012 were included in this retrospective study. Demographics, anatomic, and follow-up data were compared between two groups (with or without thrombosis). Preoperative anatomy was analyzed with a dedicated workstation, using the Society of Vascular Surgery reporting standards. Eleven (4.9%) patients presented with a limb occlusion during follow-up (46 ± 12 months). Univariate analyses were first performed to investigate the influence of preoperative variables on limb occlusion. Then, variables with a p value <0.1 were included in the multivariate analysis and showed that in the occlusion group there was a greater rate of chronic renal failure (18.2% vs. 3.8%, p = 0.012), a more frequent occurrence of distal landing zones in the external iliac artery (15.4% vs. 2.1%, p = 0.006), and a smaller aortic neck diameter (21.0 ± 2.9 mm vs. 23.6 ± 3.3 mm, p = 0.014). Although iliac anatomy does not appear to have a significant influence on limb occlusion rate in the multivariate analysis, proximal and distal sealing zones appear to be involved in this complication.

Finite element simulation of the insertion of guidewires during an EVAR procedure: example of a complex patient case, a first step toward patient-specific parameterized models.

Deformations of the vascular structure due to the insertion of tools during endovascular treatment of aneurysms of the abdominal aorta, unless properly anticipated during the preoperative planning phase, may be the source of intraoperative or postoperative complications. We propose here an explicit finite element simulation method which enables one to predict such deformations. This method is based on a mechanical model of the vascular structure which takes into account the nonlinear behavior of the arterial wall, the prestressing effect induced by the blood pressure and the mechanical support of the surrounding organs and structures. An analysis of the model sensitivity to the parameters used to represent this environment is done. This allows determining the parameters that have the largest influence on the quality of the prediction and also provides realistic values for each of them as no experimental data are available in the literature. Moreover, for the first time, the results are compared with 3D intraoperative data. This is done for a patient-specific case with a complex anatomy in order to assess the feasibility of the method. Finally, the predictive capability of the simulation is evaluated on a group of nine patients. The error between the final simulated and intraoperatively measured tool positions was 2.1 mm after the calibration phase on one patient. It results in a 4.6 ± 2.5 mm in average error for the blind evaluation on nine patients.

Combined frozen elephant trunk and endovascular repair for extensive thoracic aortic aneurysms.

BACKGROUND: We describe a 1-step treatment of extensive arch and descending aortic aneurysm by combination of frozen elephant trunk (FET) (hybrid endoprosthesis) and of conventional endoprosthesis deployment. METHODS: In a single-center, prospective, treatment-only study, the clinical data of 4 patients receiving combined FET and distal endoprosthesis deployment in the descending aorta were prospectively collected. Thoracic endoprostheses were deployed either retrogradely (off-pump from the femoral arterial access) or antegradely (from the aortic arch during hypothermic arrest). A distal-first approach was used ("trombone" mechanism). Spinal cord protection was achieved by transposition of the left subclavian artery to the left common carotid artery and selective antegrade cerebral perfusion. Preoperative computed tomography scan was performed to identify the collateral circulation. Preoperative planning was assisted by a sizing software (Endosize, Therenva Inc.). RESULTS: The aortic coverage was extended down to the orifice of the celiac trunk in one case and to the T8 level in the remainders. There was no operative mortality, 1 transient paraparesis, and 1 case of renal insufficiency. Follow-up results were satisfying (no device migration, no endoleak, no endotension, and no late neurologic complications). CONCLUSIONS: The present strategy may abolish the risks connected with the waiting time between the surgical first step and the later completion (aortic-related adverse events and drop-out) and deserves further investigations to determine its safety and feasibility profile.

Mid-term results of elective repair of extensive thoracic aortic pathology by the Evita Open Plus hybrid endoprosthesis only.

OBJECTIVES: To describe the early and mid-term clinical and instrumental results of the frozen elephant trunk (FET) procedure using the recent Evita Open Plus hybrid endoprosthesis for elective one-stage treatment of extensive thoracic aortic disease. METHODS: We reviewed 16 patients undergoing FET for post-dissection aneurysm (50%), true aneurysm (31%) or other aetiologies (19%), through median sternotomy and hypothermic circulatory arrest. An average 14 ± 7.6-month follow-up with regular contrast-enhanced control computed tomography scans was available. Four patients received preliminary carotid-subclavian bypass to improve spinal cord protection. Distal extension through endovascular deployment of stent-grafts into the descending aorta was performed during the same procedure in 3 patients. Concomitant procedures on the ascending aorta/root were done in 25% of cases. RESULTS: There were no cases of operative mortality. Cases of neither cerebral stroke nor postoperative paraplegia were observed. Two cases of transient paraparesis and 1 case of Brown-Séquard syndrome occurred. At follow-up, there were no cases of endoleak or endotension. One patient was reoperated for distal completion (thoracoabdominal aortic replacement). CONCLUSIONS: The FET using the Evita Open Plus device is a reliable and versatile treatment for one-step management of extensive disease of the aortic arch and the descending aorta. This strategy should be reserved for patients having limited preoperative comorbidities and good functional status.

Prediction of deformations during endovascular aortic aneurysm repair using finite element simulation.

During endovascular aortic aneurysm repair (EVAR), the introduction of medical devices deforms the arteries. The aim of the present study was to assess the feasibility of finite element simulation to predict arterial deformations during EVAR. The aortoiliac structure was extracted from the preoperative CT angiography of fourteen patients underwent EVAR. The simulation consists in modeling the deformation induced by the stiff wire used during EVAR. The results of the simulation were projected onto the intraoperative images, using a 3D/2D registration. The mean distance between the real and simulated guidewire was 2.3±1.1mm. Our results demonstrate that finite element simulation is feasible and appear to be reproducible in modeling device/tissue interactions and quantifying anatomic deformations during EVAR.

Finite-element-based matching of pre- and intraoperative data for image-guided endovascular aneurysm repair.

Endovascular repair of abdominal aortic aneurysms is a well-established technique throughout the medical and surgical communities. Although increasingly indicated, this technique does have some limitations. Because intervention is commonly performed under fluoroscopic control, 2-D visualization of the aneurysm requires the injection of a contrast agent. The projective nature of this imaging modality inevitably leads to topographic errors, and does not give information on arterial wall quality at the time of deployment. A specially adapted intraoperative navigation interface could increase deployment accuracy and reveal such information, which preoperative 3-D imaging might otherwise provide. One difficulty is the precise matching of preoperative data (images and models) and intraoperative observations affected by anatomical deformations due to tool-tissue interactions. Our proposed solution involves a finite-element-based preoperative simulation of tool-tissue interactions, its adaptive tuning regarding patient specific data, and the matching with intraoperative data. The biomechanical model was first tuned on a group of ten patients and assessed on a second group of eight patients.

Computer-aided surgery: concepts and applications in vascular surgery.

Computer-aided surgery makes use of a variety of technologies and information sources. The challenge over the past 10 years has been to apply these methods to tissues that deform, as do vessels when relatively rigid flexible objects are introduced into them (Lunderquist rigid guide wire, aortic prosthesis, etc) Three stages of computer-aided endovascular surgery are examined: sizing, planning, and intraoperative assistance. The authors' work shows that an approach based on optimized use of the imaging data acquired during the various observation phases (pre- and intraoperative), involving only lightweight computer equipment that is relatively transparent for the user, makes it possible to provide useful (ie, necessary and sufficient) information at the appropriate moment, in order to aid decision making and enhance the security of endovascular procedures.