Clinical Performance of the Low Profile Zenith Alpha Abdominal Endovascular Graft: 2 Year Results from the ZEPHYR Registry.

OBJECTIVE: The midterm outcomes of the low profile Zenith Alpha Abdominal Endovascular Graft from the ZEnith alPHa for aneurYsm Repair (ZEPHYR) registry are reported. METHODS: The ZEPHYR registry is a physician initiated, multicentre, non-randomised, core laboratory controlled, prospective registry. Inclusion criteria were patients with a non-ruptured abdominal aortic aneurysm with a maximum diameter ≥ 50 mm or enlargement > 5 mm within 6 months, with a site reported infrarenal neck length of ≥ 10 mm and with the intention to electively implant the Zenith Alpha abdominal endograft. Patients from 14 sites across Germany, Belgium, and the Netherlands were included. The primary endpoint was treatment success, defined as technical success and clinical success. Technical success was defined as successful delivery and deployment of the endograft in the planned position without unintentional coverage of internal iliac or renal arteries, with successful removal of the delivery system. Clinical success was defined as freedom from aneurysm sac expansion > 5 mm, type I or type III endoleaks, aneurysm rupture, stent graft migration > 10 mm, open conversion, and stent graft occlusion. RESULTS: Three hundred and forty-seven patients were included in the ZEPHYR registry. The median clinical follow up was 743 days (interquartile range [IQR] 657, 806) with a median imaging follow up of 725 days (IQR 408, 788). Treatment success at 6 months, 1, and 2 years was 92.5%, 90.4%, and 85.3%, respectively. Freedom from secondary intervention was 94.3%, 93.4%, and 86.9%, respectively. The predominant reason for secondary intervention was limb complications. Freedom from limb occlusion (per patient) at 6 months, 1, and 2 years was 97.2%, 95.8%, and 92.5%, respectively. Univariable and multivariable Cox regression analyses could not identify any independent predictor for limb complications. CONCLUSION: While treatment success is comparable with other commercially available grafts, the rate of limb complications at 2 years is of concern. The manufacturer's instructions for use should be followed closely. Further studies are necessary to investigate the root cause of the increased rate of limb complications with the Zenith Alpha Abdominal Endovascular Graft.

Co-prevalence of arterial aneurysm location - a correlation analysis based on a retrospective cross-sectional observational study.

Background: The aim of this retrospective single-centre cross-sectional observational study was to investigate co-prevalence of arterial aneurysm location systematically. Patients and methods: Patients with the diagnosis of any arterial aneurysm from January 2006 to January 2016 were investigated in a single centre. Patients with hereditary disorders of connective tissue, systemic inflammatory disease, or arterial pathologies other than true aneurysms were excluded. Aneurysm locations were assessed for every patient included. For patients with at least two co-existing aneurysms, co-prevalence of aneurysm location was investigated by calculating correlation coefficients and applying Fisher's exact test. This study report is prepared according to the STROBE statement. Results: Of 3107 identified patients with arterial aneurysms, 918 were excluded. Of the remaining 2189 patients, 951 patients with at least two aneurysms were included in the study. Bilateral aneurysm combinations of paired iliac, femoral and popliteal arteries showed the highest correlation (ϕ=0.35 to 0.67), followed by bilateral combinations of subclavian (ϕ=0.36) and internal carotid (ϕ=0.38) arteries. Abdominal aortic aneurysms in combination with visceral artery aneurysms (ϕ=-0.24 to -0.12), popliteal arteries (ϕ=-0.22) and the ascending aorta (ϕ=-0.19) showed the lowest correlation, followed by the descending aorta in combination with the common iliac arteries (ϕ=-0.12 to -0.13). Conclusions: In our study sample, aneurysm co-prevalence was highly non-random. This should be considered in the context of aneurysm screening programs.

A New Method for Common Femoral Arterial Access Using a Mixed Reality-Assisted Technique on a Phantom Model.

PURPOSE: The purpose of this study was to investigate the technical feasibility and usability of a mixed reality (MiR)-assisted common femoral arterial (CFA) access technique using a sonography-assisted registration method. MATERIALS AND METHODS: A total of 60 CFA punctures were performed on a phantom model by 2 observers. Thirty punctures were performed using MiR (MiR group) and 30 punctures were performed using a conventional sonography-guided access procedure (control group). In the MiR group, a virtual object was created based on a computed tomography (CT) angiography scan of the model and registered to the physical patient in an MiR environment utilizing a software prototype that allowed registration based on a sonography scan. Positional error assessment encompassed 4 measurements using cone beam CT scans: (1) distance of the needle tip to the centerline, (2) distance of the needle entry site from the mid-level of the ostium of the profound femoral artery, (3) angle of entry of the needle in coronal, and (4) sagittal planes. Technical success rates as well as positional errors were compared between both groups. In addition, the usability of the system was assessed according to the system usability scale (SUS). RESULTS: Technical success was 96.7% and 100% in the MiR and control groups, respectively. The median distance between the needle tip and the centerline was 3.0 (interquartile range [IQR]: 2.0-4.6) in the MiR group and 3.2 mm (IQR: 2.3-3.9) (p=0.63) in the control group. Similarly, the median distance from the needle entry site to the mid-level of the ostium of the profound femoral artery was 3.0 mm (IQR: 2.0-5.0) in the MiR group and 4.5 mm (IQR: 2.0-7.8) (p=0.18) in the control group. The median coronal angles of needle entry were 7.5° (IQR: 6-11) and 6° (IQR: 2-12) (p=0.13), and the median sagittal angles were 50° (IQR: 47-51) and 51° (IQR: 50-55) (p<0.01) in the MiR and control groups, respectively. The mean SUS score provided by both observers was 51.3. CONCLUSION: The feasibility of an MiR-assisted CFA access technique could be demonstrated on a phantom model. Further studies are needed to investigate the technique beyond phantom model experiments and in different anatomical settings. CLINICAL IMPACT: This study demonstrates the technical feasibility of a Mixed-Reality-assisted common femoral arterial access procedure on a phantom model. The positional accuracy was comparable to a conventional sonography-guided technique. However, there are several limitations that need to be resolved prior to potential implementation into clinical practice. Further studies are needed to investigate its performance beyond phantom model experiments and the prototypical application requires further technical refinement to increase its usability.

Persisting Type 2 Endoleaks Following EVAR for AAA Are Associated With AAA Expansion.

PURPOSE: To determine the evolution of abdominal aortic aneurysm (AAA) diameter in the presence of persisting type 2 endoleaks (pEL2) following endovascular abdominal aortic aneurysm repair (EVAR). MATERIALS AND METHODS: This is a retrospective, single-center, case-control study. All patients with pEL2 (pEL2 group, persisting for > 12 months) between 2004 and 2018 were identified and compared with a 1:1 age- and gender-matched control with no endoleak (control group). Primary outcome measures were freedom from AAA expansion and freedom from AAA shrinkage over time. AAA diameter measurements were performed on computed tomography angiography (CTA). Secondary outcome measures were survival, AAA-related mortality, reinterventions for pEL2, incidence of secondary type 1 endoleaks (EL1), and infrarenal aortic branch vessel anatomy. RESULTS: A total of 773 patients were treated with EVAR for AAA between 2004 and 2018. Of them, 286 patients demonstrated type 2 endoleaks (EL2) in postoperative CTA or intraoperative angiography (37%). Forty-five of 286 EL2 (15.7%) were pEL2 (pEL2 group). Freedom from AAA expansion in the pEL2 group was 100%, 96.7%, 85.2%, and 54.3% after 1, 2, 3, and 4 years, respectively, compared with 100% after 1, 2, 3, and 4 years in the control group (p<0.01). Freedom from AAA shrinkage in the pEL2 group after 1, 2, 3, and 4 years was 95.5%, 90.4%, 90.4%, and 79.1%, respectively, compared with 86.7%, 34.8%, 19.3%, and 19.3% in the control group (p<0.01). Overall survival at 1, 2, 3, and 4 years was 100%, 97.6%, 95.0% and 95.0% in the pEL2 group and 100% at 1, 2, 3, and 4 years in the control group (p=0.17). There were no AAA-related deaths in either group. Patients with pEL2 had a significantly increased number of infrarenal aortic branches (p<0.05, respectively). Eighteen patients (40.0%) in the pEL2 group underwent 34 reinterventions for pEL2, with a median follow-up (FU) of 925 days (0-4173). Clinical success was achieved in 9 patients (50.0%). Four patients (8.9%) with pEL2 developed secondary EL1 after a median FU of 1278 days (662-2121). CONCLUSION: pEL2 are associated with AAA expansion during midterm FU. Further studies are warranted to evaluate the association of AAA expansion due to pEL2 with clinical outcomes to allow recommendations with regard to treatment indications.

Systematic Review on Abdominal Penetrating Atherosclerotic Aortic Ulcers: Outcomes of Endovascular Repair.

PURPOSE: To systematically review existing evidence on outcomes of endovascular repair of abdominal atherosclerotic penetrating aortic ulcers (PAUs). MATERIAL AND METHODS: Cochrane Central Registry of Registered Trials (CENTRAL), MEDLINE (via PubMed), and Web of Science databases were systematically searched. The systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis protocol (PRISMA-P 2020). The protocol was registered in the international registry of systematic reviews (PROSPERO CRD42022313404). Studies reporting on technical and clinical outcomes of endovascular PAU repair in 3 or more patients were included. Random effects modeling was used to estimate pooled technical success, survival, reinterventions, and type 1 and type 3 endoleaks. Statistical heterogeneity was assessed using the I2 statistic. Pooled results are reported with 95% confidence intervals (CIs). Study quality was assessed using an adapted version of the Modified Coleman Methodology Score. RESULTS: Sixteen studies including 165 patients with a mean/median age ranging from 64 to 78 years receiving endovascular therapy for PAU between 1997 and 2020 were identified. Pooled technical success was 99.0% (CI: 96.0%-100%). In all, 30-day mortality was 1.0% (CI: 0%-6.0%) with an in-hospital mortality of 1.0% (CI: 0.0%-13.0%). There were no reinterventions, type 1, or type 3 endoleaks at 30 days. Median/mean follow-up ranged from 1 to 33 months. Overall, there were 16 deaths (9.7%), 5 reinterventions (3.3%), 3 type 1 (1.8%), and 1 type 3 endoleak (0.6%) during follow-up. The quality of studies was rated low according to the Modified Coleman score at 43.4 (+/- 8.5) of 85 points. CONCLUSION: There is low-level evidence on outcomes of endovascular PAU repair. While in the short-term endovascular repair of abdominal PAU seems safe and effective, mid-term and long-term data are lacking. Recommendations with regard to treatment indications and techniques in asymptomatic PAU should be made cautiously. CLINICAL IMPACT: This systematic review demonstrated that evidence on outcomes of endovascular abdominal PAU repair is limited. While in the short-term endovascular repair of abdominal PAU seems safe and effective, mid-term and long-term data are lacking. In the context of a benign prognosis of asymptomatic PAU and lacking standardization in current reporting, recommendations with regard to treatment indications and techniques in asymptomatic PAUs should be made cautiously.

Mixed reality for the assessment of aortoiliac anatomy in patients with abdominal aortic aneurysm prior to open and endovascular repair: Feasibility and interobserver agreement.

OBJECTIVES: The objective is to evaluate the feasibility and interobserver agreement of a Mixed Reality Viewer (MRV) in the assessment of aortoiliac vascular anatomy of abdominal aortic aneurysm (AAA) patients. METHODS: Fifty preoperative computed tomography angiographies (CTAs) of AAA patients were included. CTAs were assessed in a mixed reality (MR) environment with respect to aortoiliac anatomy according to a standardized protocol by two experienced observers (Mixed Reality Viewer, MRV, Brainlab AG, Germany). Additionally, all CTAs were independently assessed applying the same protocol by the same observers using a conventional DICOM viewer on a two-dimensional screen with multi-planar reconstructions (Conventional viewer, CV, GE Centricity PACS RA1000 Workstation, GE, United States). The protocol included four sets of items: calcification, dilatation, patency, and tortuosity as well as the number of lumbar and renal arteries. Interobserver agreement (IA, Cohen's Kappa, κ) was calculated for every item set. RESULTS: All CTAs could successfully be displayed in the MRV (100%). The MRV demonstrated equal or better IA in the assessment of anterior and posterior calcification (κMRV: 0.68 and 0.61, κCV: 0.33 and 0.45, respectively) as well as tortuosity (κMRV: 0.60, κCV: 0.48) and dilatation (κMRV: 0.68, κCV: 0.67). The CV demonstrated better IA in the assessment of patency (κMRV: 0.74, κCV: 0.93). The CV also identified significantly more lumbar arteries (CV: 379, MRV: 239, p < 0.01). CONCLUSIONS: The MRV is a feasible imaging viewing technology in clinical routine. Future efforts should aim at improving hologram quality and enabling accurate registration of the hologram with the physical patient.

Outcomes of endovascular repair of infrarenal penetrating aortic ulcers.

Background: To report technical success as well as perioperative outcomes of patients who underwent endovascular aortic repair (EVAR) of penetrating abdominal aortic ulcers ≤35 mm in diameter (PAU). Patients and methods: The abdominal aortic aneurysm (AAA) quality registry of the German institute for vascular research (DIGG) was used to identify patients with standard EVAR for infrarenal PAU ≤35 mm between 1/1/2019 and 12/31/2021. Infectious, traumatic, inflammatory PAUs, PAUs associated with connective tissue disease, PAUs following aortic dissection as well as true aneurysms were excluded. Demographics, cardiovascular comorbidity, technical success as well as perioperative morbidity and mortality were determined. Results: Amongst 11 537 patients who underwent EVAR during the study period, 405 with PAU ≤35 mm were eligible from 95 participating hospitals across Germany (22% women, 20.5% octogenarians). The median aortic diameter was 30 mm (Interquartile range 27-33). Cardiovascular comorbidities were frequent with coronary artery disease (34.8%), chronic heart failure (30.9%), history of myocardial infarction (19.8%), hypertension (76.8%), diabetes (21.7%), smoking (20.8%), history of stroke (9.4%), symptomatic lower extremity peripheral arterial disease (20%), chronic kidney disease (10.4%) and chronic obstructive pulmonary disease (9.6%). Most patients were asymptomatic (89.9%). Among the symptomatic patients, 13 presented with distal embolization (3.2%) and 3 with contained ruptures (0.7%). Technical success of endovascular repair was 98.3%. Both, percutaneous (37.1%) or femoral cut-down access approaches (58.5%) were registered. Endoleaks of any type were present with type 1 (0.5%), type 2 (6.4%) and type 3 (0.3%) endoleaks. Overall mortality was 0.5%. Perioperative complications occurred in 12 patients (3.0%). Conclusions: According to this registry data, endovascular repair of PAU is technically feasible with acceptable perioperative outcomes, but further studies investigating mid- and long-term data are needed before invasive treatment of PAU disease in an elderly and comorbid patient population should be recommended.

"Mixed Reality" in patient education prior to abdominal aortic aneurysm repair.

Background: To investigate the usability of Mixed-Reality (MR) during patient education in patients scheduled for abdominal aortic aneurysm (AAA) repair. Patients and methods: Consecutive patients scheduled for elective AAA repair were block-randomized in either the Mixed-Reality group (MR group) or the conventional group (control group). Patients of both groups were educated about open and endovascular repair of their respective AAA. The MR group was educated using a head-mounted display (HMD) demonstrating a three-dimensional virtual reconstruction of the respective patient's vascular anatomy. The control group was educated using a conventional two-dimensional monitor to display the patient's vasculature. Outcomes were informational gain as well as patient satisfaction with the educational process. (DRKS-ID: DRKS00025174). Results: 50 patients were included with 25 patients in either group. Both groups demonstrated improvements in scores in the Informational Gain Questionnaire (IGQ) when comparing pre- and post-education scores. (MR group: 6.5 points (±1.8) versus 7.9 points (±1.5); Control group: 6.2 points (±1.8) versus 7.6 points (±1.6); p<0.01) There was no significant difference between the MR group and the control group either in informational gain (MR group: 1.4±1.8; Control group: 1.4±1.8; p=0.5) nor in patient satisfaction scores (MR group: mean 18.3 of maximum 21 points (±3.7); Control group: mean 17 of 21 points (±3.6); p=0.1) Multiple regression revealed no correlation between the use of MR and informational gain or patient satisfaction. Usability of the system was rated high, and patients' subjective assessment of MR was positive. Conclusions: The use of MR in patient education of AAA patients scheduled for elective repair is feasible. While patients reported positively on the use of MR in education, similar levels of informational gain and patient satisfaction can be achieved with MR and conventional methods.

Thirty-day Results from the ZEPHYR Registry: Outcomes of EVAR Using the Zenith Alpha™ Abdominal Endovascular Graft for the Treatment of AAA in 347 Patients.

BACKGROUND: To report technical and clinical 30-day results following treatment with the Zenith Alpha™ abdominal stent graft from the ZEnith alPHa for aneurYsm Repair Registry (ZEPHYR). METHODS: Multicenter, nonrandomized, single arm, core laboratory-controlled, prospective registry collecting data on the Zenith Alpha Abdominal Endovascular Graft being used in subjects with abdominal aortic aneurysms (AAA) from sites in Germany, Belgium, and The Netherlands between December 2016 and December 2019. Inclusion criteria were non-ruptured AAAs with a maximum diameter ≥50 mm or enlargement >5 mm over 6 months with an AAA neck length ≥10 mm (site reported). Primary outcome measure was treatment success at 30 days. Treatment success was defined as a combined endpoint consisting of technical and clinical success. Technical success was defined as successful stent graft delivery and deployment as well as successful removal of the delivery system. Clinical success at 30 days was defined as freedom from type I and III endoleak, aneurysm rupture, conversion to open surgery and stent graft occlusion. RESULTS: Three hundred forty-seven subjects were included from 14 sites with a median age of 73.0 years (IQR 68.0-79.0). Thirty-four patients were female (9.8%). The median AAA diameter was 58.3 mm (IQR 55.0-63.5). The median proximal neck diameter was 23.6 mm (IQR 22.0-25.2) with a median proximal neck length of 24.4 mm (IQR 15.0-34.8) and a median infrarenal neck angulation of 24.5° (IQR 15.0-35.0). The right and left common iliac diameter were 16.1 mm (IQR 14.1-19.4) and 16.2 mm (IQR 14.1-19.1), respectively. The treatment success rate at 30 days was 94.8% (N = 329). Technical success was achieved in 333 patients (96.0%). The clinical success rate at 30 days was 98.8% (N = 343). Three patients had limb occlusions at 30 day follow up (0.9%). One patient had a type Ib endoleak (0.3%). Seventy percent of vascular access approaches were percutaneous. The reintervention rate was 1.7% (N = 6) within 30 days. Indications for reinterventions were a false aneurysm at puncture site (N = 1), limb complications (N = 2), stentgraft-associated renal artery occlusions (N = 2), and an external iliac artery thrombosis (N = 1). CONCLUSIONS: Endovascular aneurysm repair using the Zenith Alpha Abdominal Endovascular Graft is effective in the short term. Long term results will be reported in the future.

[Mixed Reality in Vascular Surgery - a Scoping Review]. / Mixed Reality in der Gefäßchirurgie ­ ein Scoping Review.

BACKGROUND: "Mixed reality" (MR) allows the projection of virtual objects into the user's field of view through a head-mounted display (HMD). In the interventional and surgical treatment of vascular diseases MR applications could be of future benefit. The following scoping review aims to provide orientation on the current application of the aforementioned technologies in the field of vascular surgery and to define research goals for the future. METHODS: A systematic literature search was performed in PubMed (MEDLINE) using the search terms "aorta", "intervention", "endovascular intervention", "vascular surgery", "aneurysm", "endovascular", "vascular access", each in combination with "mixed reality" or "augmented reality". The search was performed according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines for scoping reviews. RESULTS: From 547 references 8 relevant studies were identified. The search results could be classified into two categories: (1) MR aimed at information management and improving periprocedural ergonomics (n = 3) and (2) MR aimed at intraoperative navigation (n = 5). The registration of the physical patient with the virtual object and the tracking of instruments in the MR environment for intraoperative navigation is currently the focus of scientific interest and could be demonstrated on phantom and animal models with technical success. However, the methods presented so far are associated with high infrastructural costs and important limitations. CONCLUSION: The use of MR in the field of vascular surgery is promising. For the future, alternative, pragmatic registration methods with appropriate quantification of the positional error should be aimed at. The developed software and hardware solutions should be adapted to the requirements of vascular surgery. Electromagnetic instrument tracking appears to be a useful complementary technology for the implementation of MR-assisted navigation.

Midterm single-center results after endovascular aneurysm sealing reveal a high rate of stent graft migration, secondary aneurysm ruptures, and device-related reinterventions.

OBJECTIVE: To report procedural results and mid-term follow-up outcomes of patients treated with endovascular aneurysm sealing (EVAS) for abdominal aortic disease. METHODS: In this retrospective observational study, all patients treated with EVAS between March 2013 and January 2018 for abdominal aortic aneurysm (AAA) or abdominal penetrating aortic ulcer were included. The datasets included demographics, aneurysm morphology, and procedural and clinical surveillance outcomes. Furthermore, patients treated within the original instructions for use (IFU-group) were compared with patients treated outside the IFU (non-IFU-group) with regard to survival, reintervention-free survival, freedom from type I endoleak, and freedom from stent graft migration. RESULTS: Seventy patients were included (67 male; median age, 72.5 years). Sixty-five patients were treated for AAA and 5 patients for abdominal penetrating aortic ulcer. Sixty-nine cases were treated electively (98.6%). Technical success was achieved in 68 cases (97.1%). The median clinical follow-up was 50.5 months (interquartile range, 29.3-62.7 months) with a median computed tomography angiographic follow-up of 38.5 months (interquartile range, 17.1-60.2 months). There were five deaths during the study period (7.1%), four of which were aneurysm related (5.7%). Five secondary AAA ruptures were detected (7.1%). Overall, 25 of 70 patients (35.7%) underwent 35 reinterventions, mostly owing to thrombotic complications (18.6%), stent graft migration (17.1%), and type I endoleak (12.9%). Fifteen patients were treated outside of the IFU (non-IFU-group) (21.4%). The estimated reintervention-free survival for the entire cohort at 30 days and 1, 3, and 5 years was 94.3%, 88.5%, 72%, and 56.9%, respectively. Freedom from stent graft migration at 1, 3, and 5 years was 98.6%, 82.0%, and 47.3%, respectively. The estimated freedom from type I endoleak at 30 days and 1, 3, and 5 years in the IFU-group was 100%, 100%, 94.9% and, 91.1% and significantly different when compared with the non-IFU-group with 79.5%, 72.2%, 72.2%, and 72.2% (P = .012). CONCLUSIONS: Although the technical and initial results were satisfying, the mid-term results were disappointing. The enforcement of a close follow-up protocol for all patients treated with EVAS, especially vigilant for stent graft migration to prevent secondary type I endoleak and rupture, is strongly recommended.

Comparing Different Registration and Visualization Methods for Navigated Common Femoral Arterial Access-A Phantom Model Study Using Mixed Reality.

Mixed reality (MxR) enables the projection of virtual three-dimensional objects into the user's field of view via a head-mounted display (HMD). This phantom model study investigated three different workflows for navigated common femoral arterial (CFA) access and compared it to a conventional sonography-guided technique as a control. A total of 160 punctures were performed by 10 operators (5 experts and 5 non-experts). A successful CFA puncture was defined as puncture at the mid-level of the femoral head with the needle tip at the central lumen line in a 0° coronary insertion angle and a 45° sagittal insertion angle. Positional errors were quantified using cone-beam computed tomography following each attempt. Mixed effect modeling revealed that the distance from the needle entry site to the mid-level of the femoral head is significantly shorter for navigated techniques than for the control group. This highlights that three-dimensional visualization could increase the safety of CFA access. However, the navigated workflows are infrastructurally complex with limited usability and are associated with relevant cost. While navigated techniques appear as a potentially beneficial adjunct for safe CFA access, future developments should aim to reduce workflow complexity, avoid optical tracking systems, and offer more pragmatic methods of registration and instrument tracking.

Simulation of thoracic endovascular aortic repair in a perfused patient-specific model of type B aortic dissection.

PURPOSE: Complicated type B Aortic dissection is a severe aortic pathology that requires treatment through thoracic endovascular aortic repair (TEVAR). During TEVAR a stentgraft is deployed in the aortic lumen in order to restore blood flow. Due to the complicated pathology including an entry, a resulting dissection wall with potentially several re-entries, replicating this structure artificially has proven to be challenging thus far. METHODS: We developed a 3d printed, patient-specific and perfused aortic dissection phantom with a flexible dissection flap and all major branching vessels. The model was segmented from CTA images and fabricated out of a flexible material to mimic aortic wall tissue. It was placed in a pulsatile hemodynamic flow loop. Hemodynamics were investigated through pressure and flow measurements and doppler ultrasound imaging. Surgeons performed a TEVAR intervention including stentgraft deployment under fluoroscopic guidance. RESULTS: The flexible aortic dissection phantom was successfully incorporated in the hemodynamic flow loop, a systolic pressure of 112 mmHg and physiological flow of 4.05 L per minute was reached. Flow velocities were higher in true lumen with a up to 35.7 cm/s compared to the false lumen with a maximum of 13.3 cm/s, chaotic flow patterns were observed on main entry and reentry sights. A TEVAR procedure was successfully performed under fluoroscopy. The position of the stentgraft was confirmed using CTA imaging. CONCLUSIONS: This perfused in-vitro phantom allows for detailed investigation of the complex inner hemodynamics of aortic dissections on a patient-specific level and enables the simulation of TEVAR procedures in a real endovascular operating environment. Therefore, it could provide a dynamic platform for future surgical training and research.

Recurrent neural networks for generalization towards the vessel geometry in autonomous endovascular guidewire navigation in the aortic arch.

PURPOSE: Endovascular intervention is the state-of-the-art treatment for common cardiovascular diseases, such as heart attack and stroke. Automation of the procedure may improve the working conditions of physicians and provide high-quality care to patients in remote areas, posing a major impact on overall treatment quality. However, this requires the adaption to individual patient anatomies, which currently poses an unsolved challenge. METHODS: This work investigates an endovascular guidewire controller architecture based on recurrent neural networks. The controller is evaluated in-silico on its ability to adapt to new vessel geometries when navigating through the aortic arch. The controller's generalization capabilities are examined by reducing the number of variations seen during training. For this purpose, an endovascular simulation environment is introduced, which allows guidewire navigation in a parametrizable aortic arch. RESULTS: The recurrent controller achieves a higher navigation success rate of 75.0% after 29,200 interventions compared to 71.6% after 156,800 interventions for a feedforward controller. Furthermore, the recurrent controller generalizes to previously unseen aortic arches and is robust towards size changes of the aortic arch. Being trained on 2048 aortic arch geometries gives the same results as being trained with full variation when evaluated on 1000 different geometries. For interpolation a gap of 30% of the scaling range and for extrapolation additional 10% of the scaling range can be navigated successfully. CONCLUSION: Adaption to new vessel geometries is essential in the navigation of endovascular instruments. Therefore, the intrinsic generalization to new vessel geometries poses an essential step towards autonomous endovascular robotics.

Learning-based autonomous vascular guidewire navigation without human demonstration in the venous system of a porcine liver.

PURPOSE: The navigation of endovascular guidewires is a dexterous task where physicians and patients can benefit from automation. Machine learning-based controllers are promising to help master this task. However, human-generated training data are scarce and resource-intensive to generate. We investigate if a neural network-based controller trained without human-generated data can learn human-like behaviors. METHODS: We trained and evaluated a neural network-based controller via deep reinforcement learning in a finite element simulation to navigate the venous system of a porcine liver without human-generated data. The behavior is compared to manual expert navigation, and real-world transferability is evaluated. RESULTS: The controller achieves a success rate of 100% in simulation. The controller applies a wiggling behavior, where the guidewire tip is continuously rotated alternately clockwise and counterclockwise like the human expert applies. In the ex vivo porcine liver, the success rate drops to 30%, because either the wrong branch is probed, or the guidewire becomes entangled. CONCLUSION: In this work, we prove that a learning-based controller is capable of learning human-like guidewire navigation behavior without human-generated data, therefore, mitigating the requirement to produce resource-intensive human-generated training data. Limitations are the restriction to one vessel geometry, the neglected safeness of navigation, and the reduced transferability to the real world.

Mixed-Reality-Assisted Puncture of the Common Femoral Artery in a Phantom Model.

Percutaneous femoral arterial access is daily practice in a variety of medical specialties and enables physicians worldwide to perform endovascular interventions. The reported incidence of percutaneous femoral arterial access complications is 3-18% and often results from suboptimal puncture location due to insufficient visualization of the target vessel. The purpose of this proof-of-concept study was to evaluate the feasibility and the positional error of a mixed-reality (MR)-assisted puncture of the common femoral artery in a phantom model using a commercially available navigation system. In total, 15 MR-assisted punctures were performed. Cone-beam computed tomography angiography (CTA) was used following each puncture to allow quantification of positional error of needle placements in the axial and sagittal planes. Technical success was achieved in 14/15 cases (93.3%) with a median axial positional error of 1.0 mm (IQR 1.3) and a median sagittal positional error of 1.1 mm (IQR 1.6). The median duration of the registration process and needle insertion was 2 min (IQR 1.0). MR-assisted puncture of the common femoral artery is feasible with acceptable positional errors in a phantom model. Future studies should aim to measure and reduce the positional error resulting from MR registration.

Comparison of endovascular aneurysm sealing and repair with respect to contrast use and radiation in comparable patient cohorts.

BACKGROUND: Due to recent advances in endograft design and percutaneous access, technical success could be increased during endovascular aneurysm repair (EVAR). Beside EVAR, endovascular aneurysm sealing (EVAS) provides an alternative procedure to treat aneurysms. To compare the two methods, additional benchmark criteria should be evaluated: Screening time, dose area product (DAP), procedure time and contrast use. In this study these technical variables are analyzed for EVAS vs. EVAR in comparable patient cohorts. METHODS: It is a retrospective, single-center study. Only elective cases of infrarenal aortic aneurysms were included, all treated by the same surgeon (D.B.). Procedures were performed within the instructions for use without additional procedures. All operations were undertaken in a hybrid operating theatre. For EVAR, only the Medtronic Endurant® and the Gore C3 Excluder® were included. For EVAS the Nellix® from Endologix was used. RESULTS: Between 2012 and 2016, 67 patients were treated with EVAS and 40 with EVAR; of these 20 and 16 could be introduced into the study respectively. Median age was 73 and 72 years respectively (only men). The two groups were comparable in terms of BMI, GFR and ASA-status. Screening time was reduced for EVAS (10.6 vs. 14.5 min., P<0.01), while the DAP was not significantly different. Procedural time and contrast use were increased for EVAS (120 vs. 96 min., 120 vs. 79 mL, P<0.01). CONCLUSIONS: Especially the younger EVAS-procedure requires ongoing review in order to further reduce contrast agent. Reduced screening time for EVAS does not have a significant impact on radiation dose.