The influence of prototype testing in three-dimensional aortic models on fenestrated endograft design

Systematic Review on the Use of 3D-Printed Models for Planning, Training and Simulation in Vascular Surgery

The use of 3D-printed models in simulation-based training and planning for vascular surgery is gaining interest. This study aims to provide an overview of the current applications of 3D-printing technologies in vascular surgery. We performed a systematic review by searching four databases: PubMed, Web of Science, Scopus, and Cochrane Library (last search: 1 March 2024). We included studies considering the treatment of vascular stenotic/occlusive or aneurysmal diseases. We included papers that reported the outcome of applications of 3D-printed models, excluding case reports or very limited case series (≤5 printed models or tests/simulations). Finally, 22 studies were included and analyzed. Computed tomography angiography (CTA) was the primary diagnostic method used to obtain the images serving as the basis for generating the 3D-printed models. Processing the CTA data involved the use of medical imaging software; 3DSlicer (Brigham and Women's Hospital, Harvard University, Boston, MA), ITK-Snap, and Mimics (Materialise NV, Leuven, Belgium) were the most frequently used. Autodesk Meshmixer (San Francisco, CA, USA) and 3-matic (Materialise NV, Leuven, Belgium) were the most frequently employed mesh-editing software during the post-processing phase. PolyJet™, fused deposition modeling (FDM), and stereolithography (SLA) were the most frequently employed 3D-printing technologies. Planning and training with 3D-printed models seem to enhance physicians' confidence and performance levels by up to 40% and lead to a reduction in the procedure time and contrast volume usage to varying extents.

Three-Dimensional Printing Application in a Challenging Case of Type II Endoleak

PURPOSE

To highlight the importance of 3-dimensional (3D) arterial printing in a case of type II endoleak (EL) embolization.

CASE REPORT

An 81-year-old patient, previously treated with endovascular aortic repair (EVAR), developed a type II EL requiring treatment. The EL's main origin was the median sacral artery (MSA). Initial attempts in embolization via a transsealing and transarterial approach were unsuccessful owing to extremely tortuous arterial communications between the left hypogastric artery and the MSA. The construction of a clear resin 3D model of the aorta and iliolumbar arteries improved anatomy understanding and moreover allowed a preoperative simulation. The subsequent transarterial attempt in embolization was resolutive, significantly reducing total procedural time and radiation dose.

CONCLUSION

Printing of clear resin 3D arterial models facilitates type II EL transarterial embolization, improving anatomy understanding and allowing simple fluoroscopy-free simulations.

CLINICAL IMPACT

The aim of our work is to highlight the additional value of three-dimensional (3D) printing during preoperative planning of challenging endovascular cases. To our best knowledge, this is the first report about 3D printing use in a case of type II endoleak (EL). We believe that realizing life-size aortic models in selected cases where a complex type II EL embolization procedure is indicated, could lead to a better understanding of arterial anatomy, thus allowing to increase procedural success and reduce operative and most importantly fluoroscopy time.

Clinical situations for which 3D Printing is considered an appropriate representation or extension of data contained in a medical imaging examination: vascular conditions

BACKGROUND

Medical three-dimensional (3D) printing has demonstrated utility and value in anatomic models for vascular conditions. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (3DPSIG) provides appropriateness recommendations for vascular 3D printing indications.

METHODS

A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with vascular indications. Each study was vetted by the authors and strength of evidence was assessed according to published appropriateness ratings.

RESULTS

Evidence-based recommendations for when 3D printing is appropriate are provided for the following areas: aneurysm, dissection, extremity vascular disease, other arterial diseases, acute venous thromboembolic disease, venous disorders, lymphedema, congenital vascular malformations, vascular trauma, vascular tumors, visceral vasculature for surgical planning, dialysis access, vascular research/development and modeling, and other vasculopathy. Recommendations are provided in accordance with strength of evidence of publications corresponding to each vascular condition combined with expert opinion from members of the 3DPSIG.

CONCLUSION

This consensus appropriateness ratings document, created by the members of the 3DPSIG, provides an updated reference for clinical standards of 3D printing for the care of patients with vascular conditions.

Physician-Modified Stent-Grafts Created in the Three-Dimensionally Aortic Template Have Better Reliability and Greater Alignment With the Target Vessels Than Stent-Grafts Modified Based on Measurements From Computed Tomography

PURPOSE

Physician-modified stent-grafts (PMSG) are widely used, especially when a patient's condition precludes waiting for a custom-made device. In recent years, the modification process has been upgraded using 3-dimensional (3D) aortic templates. Nonetheless, the reliability of PMSG and accuracy of fenestration alignment with the target vessel are not known. Thus, the study is aimed to fulfill the gap in current knowledge.

MATERIALS AND METHODS

Ten computed tomographic (CT) scans of aortic aneurysm previously treated with the fenestrated endovascular repair were selected to 3D-print aortic templates and elastic vessel phantoms. Two vascular surgeons performed fenestrations using the 3D template and modification plan based on CT measurements. Two operators each performed 10 fenestrated stent-grafts in the aortic template and 10 using CT measurements, for a total of 40 fenestrated stent-grafts. Then, stent-grafts were implanted in elastic vessel phantoms, which served to evaluate fenestration alignment with the target vessel. The alignment was judged in a 5-point scale: 0%, 1% to 25%, 26% to 50%, 51% to 75%, and 76% to 100%. The distances between fenestrations served to calculate interobserver variability for both methods. The measurements were processed as interclass correlation coefficient (ICC), Pearson and Spearman correlation, and Bland-Altman plots.

RESULTS

PMSG created with a 3D template had higher interclass correlation coefficient values and Pearson/Spearman correlation than fenestrations created from CT measurements. The rate of fenestration alignment with the target vessel was higher for PMSG created with a 3D template (p=0.007).

CONCLUSIONS

PMSGs created with a 3D template are more reliable and have better fenestration alignment with the target vessel than PMSGs created based on CT measurements.

Can the Fenestrated Anaconda™ salvage failed competitor endografts? An international frame of reference

INTRODUCTION

An abdominal aortic aneurysm (AAA) is a life-threatening abnormal dilation of the abdominal aorta that can be repaired either endovascularly or with open surgery. However, endovascular aortic repair (EVAR) has become the main treatment modality for AAA due to its more optimal results. EVAR devices can either be standard, fenestrated, or branched, with fenestrated EVAR (FEVAR) seemingly achieving superior prospects. Although EVAR is associated with excellent outcomes, it still carries a risk of certain complications requiring reintervention or 'rescue'. Several commercial EVAR devices are available on the global market, nevertheless, the Fenestrated Anaconda developed by Terumo Aortic can be considered the superior device due to the wide range of endovascular solutions that it offers along with its unique custom-made approach, excellent results and its highly promising potential to be used as a 'rescue' device for failed competitor endografts.

MATERIALS AND METHODS

The current study represents a 9-year cross-sectional international analysis of a custom-made Fenestrated Anaconda™ device. For the statistical analysis, SPSS 28 for Windows and R were utilised. Pearson Chi-square analysis was used to assess differences in cumulative distribution frequencies between select variables. Statistical significance for all two-tailed tests was set at p < 0.05.

RESULTS

Out of 5058 EVARs performed using the Fenestrated Anaconda, 2987 (59%) were 'rescue' procedures for migrated Gore (n = 252) and Medtronic (n = 2735) devices. The Fenestrated Anaconda™ was indicated as the reintervention device either due to unsuitable/complex anatomy for the competitor (n = 2411) or based on surgeon preference (n = 576). Overall, the Fenestrated Anaconda was utilised to rescue 3466 (68.5%) failed previous EVARs using competitor devices. Yet, the primary endovascular solution offered by the Fenestrated Anaconda was FEVAR (91.3%), with 112 (2.2%) devices using custom-made iliac stents.

DISCUSSION

The use of the Fenestrated Anaconda endograft as a 'rescue' device to salvage failed competitor devices is well-established in the literature with excellent clinical outcomes achieved. The evidence in the literature also highlights the distinctive custom-made approach that the Fenestrated Anaconda offers which enables it to treat extremely complex aortic anatomy.

The Effect of Age on Peri-Operative Outcomes after FEVAR

INTRODUCTION

Fenestrated endovascular aortic repair (FEVAR) has become a popular custom-made treatment option for juxtarenal and pararenal aneurysms. It has been previously investigated whether octogenarians as a distinct subgroup are at increased risk for adverse outcomes after FEVAR. With diverging results and an inconclusive understanding of age as a risk factor in general, an analysis of the historical data of a single center was conducted to add to the available body of evidence and further investigate the effect of age as a continuous risk factor.

METHODS

A retrospective data analysis of a prospectively maintained single-center database of all patients who underwent FEVAR at a single department of vascular surgery was performed. The main endpoint was post-operative survival. In addition to association analyses, potential confounders such as co-morbidities, complication rates, or aneurysm diameter were examined. In terms of sensitivity analyses, logistic regression models were created for the dependent variables of interest.

RESULTS

During the observation period from April 2013 to November 2020, 40 patients over the age of 80 and 191 patients under the age of 80 were treated by FEVAR. The 30-day survival showed no significant difference between the groups (95.1% in octogenarians and 94.3% in patients under 80 years of age). The sensitivity analyses conducted also showed no difference between the two groups, and complication and technical success rates were comparable. The aneurysm diameter was 67 ± 13 mm in the study group and 61 ± 15 mm in those under 80 years of age. Additionally, the sensitivity analyses showed that age as a continuous variable exhibits no effect on the outcomes of interest.

DISCUSSION

In the present study, age was not associated with adverse peri-operative outcomes after FEVAR, including mortality, lower technical success rates, complications, or length of hospital stay. Essentially, the most highly associated factor with hospital and ICU length of stay was time spent in surgery. However, octogenarians had a significantly larger aortic diameter at the time of treatment, which might indicate the potential introduction of bias by pre-interventional patient selection. Nevertheless, the usefulness of research on octogenarians as a distinct subgroup might be questionable regarding the scalability of results, and future studies might focus on age as a continuous risk factor instead.

Fenestrated Endovascular Aortic Repair After Failed Endovascular Aortic Repair

PURPOSE

Fenestrated endovascular aortic repair (FEVAR) is technically more challenging when performed after a failing EVAR procedure (FEVAR after EVAR). This study aims to assess the technical outcome of FEVAR after EVAR and to identify factors that may influence complication rates.

METHODS

A retrospective observational study was conducted at a single department of vascular and endovascular surgery. The rate of FEVAR after EVAR compared to primary FEVAR is reported. Complication and primary unconnected fenestration (PUF) rates as well as survival were assessed for the FEVAR after EVAR cohort. PUF rates and operating time were also compared to all primary FEVAR patients. Patient characteristics and technical factors such as number of fenestrations or use of a steerable sheath were assessed as possible influencers on technical success when performing FEVAR after EVAR.

RESULTS

Two hundred and nine fenestrated devices were implanted during the study period (2013 to April 2020). Thirty-five patients (16.7% of all FEVAR patients) had undergone FEVAR after EVAR and were included in the study. Overall survival at last follow-up (20.2±19.1 months) was 82.9% in FEVAR after EVAR patients. Rates of technical failure dropped significantly after 14 procedures (42.9% vs. 9.5%; p=0.03). Primary unconnected fenestrations were seen in 3 cases of FEVAR after EVAR (8.6%) and 14 of 174 primary FEVAR cases (8.0%; p>0.99). Operating time for FEVAR after EVAR was significantly higher than for primary FEVAR (301.1±110.5 minutes vs. 253.9±103.4 minutes; p=0.02). The availability of a steerable sheath was a significant predictor of reduced risk of PUFs, whereas age and gender, number of fenestrations or suprarenal fixation of the failed EVAR did not significantly influence PUF rates.

CONCLUSION

Fewer technical complications were seen over the study period in FEVAR after EVAR patients. While rates of PUFs were not different from primary FEVAR, operating time was significantly longer in patients undergoing FEVAR for failed EVAR. Fenestrated EVAR can be a valuable and safe tool to treat patients with progression of aortic disease or type Ia endoleak after EVAR but may be more complex to achieve than primary FEVAR.

CLINICAL IMPACT

This retrospective study assesses the technical outcome of fenestrated endovascular aortic repair (fenestrated EVAR; FEVAR) after prior EVAR. While rates of primary unconnected fenestrations were not different from primary FEVAR, operating time was significantly longer in patients undergoing FEVAR for failed EVAR. Fenestrated EVAR after prior EVAR may be technically more challenging than primary FEVAR procedures, but could be performed with equally good results in this patient cohort. FEVAR offers a feasible treatment option for patients with progression of aortic disease or type Ia endoleak after EVAR.

Quality assurance in 3D-printing: A dimensional accuracy study of patient-specific 3D-printed vascular anatomical models

3D printing enables the rapid manufacture of patient-specific anatomical models that substantially improve patient consultation and offer unprecedented opportunities for surgical planning and training. However, the multistep preparation process may inadvertently lead to inaccurate anatomical representations which may impact clinical decision making detrimentally. Here, we investigated the dimensional accuracy of patient-specific vascular anatomical models manufactured via digital anatomical segmentation and Fused-Deposition Modelling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), and PolyJet 3D printing, respectively. All printing modalities reliably produced hand-held patient-specific models of high quality. Quantitative assessment revealed an overall dimensional error of 0.20 ± 3.23%, 0.53 ± 3.16%, -0.11 ± 2.81% and -0.72 ± 2.72% for FDM, SLA, PolyJet and SLS printed models, respectively, compared to unmodified Computed Tomography Angiograms (CTAs) data. Comparison of digital 3D models to CTA data revealed an average relative dimensional error of -0.83 ± 2.13% resulting from digital anatomical segmentation and processing. Therefore, dimensional error resulting from the print modality alone were 0.76 ± 2.88%, + 0.90 ± 2.26%, + 1.62 ± 2.20% and +0.88 ± 1.97%, for FDM, SLA, PolyJet and SLS printed models, respectively. Impact on absolute measurements of feature size were minimal and assessment of relative error showed a propensity for models to be marginally underestimated. This study revealed a high level of dimensional accuracy of 3D-printed patient-specific vascular anatomical models, suggesting they meet the requirements to be used as medical devices for clinical applications.

Precision Medicine in Vascular and Endovascular Surgery

Personalized medicine and precision medicine are terms often used to refer to treatment strategies tailored specifically to individual characteristics of patients, as opposed to a one-size fits all approach [...].

3D printing in the planning and teaching of endovascular procedures

BACKGROUND

The introduction of 3D printing in the medical field led to new possibilities in the planning of complex procedures, as well as new ways of training junior physicians. Especially in the field of vascular interventions, 3D printing has a wide range of applications.

METHODOLOGICAL INNOVATIONS

3D-printed models of aortic aneurysms can be used for procedural training of endovascular aortic repair (EVAR), which can help boost the physician's confidence in the procedure, leading to a better outcome for the patient. Furthermore, it allows for a better understanding of complex anatomies and pathologies. In addition to teaching applications, the field of pre-interventional planning benefits greatly from the addition of 3D printing. Especially in the preparation for a complex endovascular aortic repair, prior orientation and test implantation of the stent grafts can further improve outcomes and reduce complications. For both teaching and planning applications, high-quality imaging datasets are required that can be transferred into a digital 3D model and subsequently printed in 3D. Thick slice thickness or suboptimal contrast agent phase can reduce the overall detail of the digital model, possibly concealing crucial anatomical details.

CONCLUSION

Based on the digital 3D model created for 3D printing, another new visualization technique might see future applications in the field of vascular interventions: virtual reality (VR). It enables the physician to quickly visualize a digital 3D model of the patient's anatomy in order to assess possible complications during endovascular repair. Due to the short transfer time from the radiological dataset into the VR, this technique might see use in emergency situations, where there is no time to wait for a printed model.

3D printing in aortic endovascular therapies

Endovascular treatment of aortic disease, including aneurysm or dissection, is expanding at a rapid pace. Often, the specific patient anatomy in these cases is complex. Additive manufacturing, also known as three-dimensional (3D) printing, is especially useful in the treatment of aortic disease, due to its ability to manufacture physical models of complex patient anatomy. Compared to other surgical procedures, endovascular aortic repair can readily exploit the advantages of 3D printing with regard to operative planning and preoperative training. To date, there have been numerous uses of 3D printing in the treatment of aortic pathology as an adjunct in presurgical planning and as a basis for training modules for fellows and residents. In this review, we summarize the current uses of 3D printing in the endovascular management of aortic disease. We also review the process of producing these models, the limitations of their applications, and future directions of 3D printing in this field.

Abdominal Aortic Aneurysm: Can the Anaconda™ Custom-Made Device Deliver? An International Perspective

Introduction

Since the introduction of endovascular aortic repair (EVAR), it has demonstrated excellent clinical outcomes and has replaced open surgical repair (OSR) in the treatment of abdominal aortic aneurysms (AAA). AAA is a life-threatening abnormal dilation of the abdominal aorta to 1.5 times its normal diameter. Several commercial EVAR devices exist on the global market, with the Terumo Aortic Fenestrated Anaconda™ graft showing superiority. In this study, we sought to provide an international perspective using multicenter-multinational data on the Anaconda™ device characteristics, design, and delivery, and discuss relevant literature.

Materials and Methods

This study represents a cross-sectional international analysis of custom-made fenestrated Anaconda™ device. Ethical and legal approval for data collection was obtained from each of the local authorities. For the statistical analysis, SPSS 28 for Windows and R were utilized. Pearson’s chi-square analysis was used to assess differences in cumulative distribution frequencies between select variables. Statistical significance for all two-tailed tests was set at p < 0.05.

Results

A total of 5,030 Anaconda™ devices were implanted during the 9-year study period in 27 countries spanning 6 continents. The predominant device category was bifurcate (83.6%), whereas the most common proximal ring stent configuration being standard (64.5%). All devices were delivered within 8 weeks of diagnosis, with most being implanted within 6–8 weeks (55.4%). The Anaconda™ was indicated in the 3,891 (77.4%) patients due to competitor rejection/inability to treat unsuitable/complex aortic anatomy. In the remaining 1,139 (22.6%) patients, it was utilized based on surgeon preference. Almost all devices (95%) were delivered along with a prototype. Of the total 5,030 Anaconda™ devices, 438 (8.7%) used 0–1 fenestrations, 2,349 (46.7%) used 2–3, while 2,243 (44.6%) utilized 4, 5, or 6 fenestrations.

Discussion

The Terumo Aortic Fenestrated Anaconda™ device features a highly unique and innovative design that enables it to treat highly complex aortic anatomy while achieving excellent results. The Anaconda™’s custom-made approach allows it to be tailored to individual patient anatomy, in addition to the device prototype provided by Terumo Aortic optimize clinical outcomes. Finally, the fenestrated Anaconda™ is a highly versatile device offering a wide range of device categories, configurations, and sizes.

Embolization using patient-specific vascular models created by a 3D printer for difficult cases: a report of two cases

With the widespread use of three-dimensional printers, organ models created by these printers are now being used in the medical field for preoperative planning of surgeries. In this article, we report two cases in which embolization was expected to be difficult, and the three-dimensional printer-based vascular modeling was helpful in planning the surgery. The first case involved an aneurysm of the splenic artery. We attempted to embolize the aneurysm but were unable to advance the catheter into the distal artery and discontinued the procedure. The second case was a perianal varicose vein, which was initially treated with percutaneous transhepatic obliteration but was recanalized and required embolization. However, we expected difficulty in selecting the inferior mesenteric vein. In both cases, the vascular models were created using a 3D printer from the patients' computed tomography images. Preoperative planning, including treatment simulation, was based on these models. The time required to print a three-dimensional vascular model was approximately 12 hours at a cost of less than $10 each. Patient-specific vascular models using a three-dimensional printer can be a simple and inexpensive tool that can increase the success of embolization in difficult cases.

Assessment of fenestrated Anaconda stent graft design by numerical simulation: Results of a European prospective multicenter study

OBJECTIVE

A crucial step in designing fenestrated stent grafts for treatment of complex aortic abdominal aneurysms is the accurate positioning of the fenestrations. The deployment of a fenestrated stent graft prototype in a patient-specific rigid aortic model can be used for design verification in vitro, but is time and human resources consuming. Numerical simulation (NS) of fenestrated stent graft deployment using the finite element analysis has recently been developed; the aim of this study was to compare the accuracy of fenestration positioning by NS and in vitro.

METHODS

All consecutive cases of complex aortic abdominal aneurysm treated with the Fenestrated Anaconda (Terumo Aortic) in six European centers were included in a prospective, observational study. To compare fenestration positioning, the distance from the center of the fenestration to the proximal end of the stent graft (L) and the angular distance from the 0° position (C) were measured and compared between in vitro testing (L1, C1) and NS (L2, C2). The primary hypothesis was that ΔL (|L2 - L1|) and ΔC (|C2 - C1|) would be 2.5 or less mm in more than 80% of the cases. The duration of both processes was also compared.

RESULTS

Between May 2018 and January 2019, 50 patients with complex aortic abdominal aneurysms received a fenestrated stent graft with a total of 176 fenestrations. The ΔL and ΔC was 2.5 mm or less for 173 (98%) and 174 (99%) fenestrations, respectively. The NS process duration was significantly shorter than the in vitro (2.1 days [range, 1.0-5.2 days] vs 20.6 days [range, 9-82 days]; P < .001).

CONCLUSIONS

Positioning of fenestrations using NS is as accurate as in vitro and could significantly decrease delivery time of fenestrated stent grafts.

Multicentre experience with an iliac fenestrated device

OBJECTIVES

The aim of this study was to present a multicentre experience of technical results and mid-term follow-up using a custom-made iliac fenestrated device (Terumo Aortic, Inchinnan, Renfrewshire, UK) for the treatment of iliac aneurysms and endoleaks.

METHODS

A multicentre retrospective evaluation of 22 patients (3-12 per institution) with either an iliac artery aneurysm or endoleak treated with an iliac fenestrated device was performed. Data were gathered from 3 departments of vascular and endovascular surgery at 3 European institutions.

RESULTS

Ten of the included patients (45.5%) were treated for an endoleak and 12 had aorto-iliac aneurysms (54.5%). Two patients underwent bilateral fenestrated device implantation for a total of 24 devices included in this analysis. Primary technical success was 91.7% (22 of 24 implanted devices). One of the 24 internal iliac arteries could not be cannulated and was covered (primary assisted technical success rate 95.8%) and 1 patient required a relining of the stent graft due to a mid-grade stenosis opposite the internal iliac artery fenestration. Survival at the last available follow-up (mean 15.2 ± 12.0 months, range 0.5-36.6 months) was 90.9%.

CONCLUSIONS

The present investigation adds to a growing body of literature on custom-made endografts and their usefulness in achieving endovascular repair without compromising blood flow via important arterial branch vessels, such as the internal iliac artery. It presents encouraging technical and mid-term follow-up data from consecutive patients treated for iliac aneurysms or endoleaks using this custom-made device. The technique may help avoid adverse sequelae associated to a coil-and-cover approach when iliac branch devices are not feasible.

Utility of 3D printed abdominal aortic aneurysm phantoms: a systematic review

BACKGROUND

3D printed (3DP) abdominal aortic aneurysm (AAA) phantoms are emerging in the literature as an adjunct for the visualization of complex anatomy, particularly for presurgical device selection and simulation. This is the first systematic review to provide a comprehensive overview of 3DP for endovascular aneurysm repair (EVAR) planning and intervention, evaluating the readiness of current levels of technology for mainstream implementation.

METHODS

A systematic literature search of PubMed and MEDLINE was performed as per PRISMA guidelines using the terms '3D Printing', 'AAA' OR 'EVAR' and related index terms, and further relevant articles were appraised via a snowballing approach. Our last search was conducted on 14 November 2020.

RESULTS

Twenty-five articles were identified for critical analysis, with 14 cases or technical reports. Nineteen publications utilized 3DP AAA phantoms to aid presurgical decision making, device selection and design. Four publications explored the utility of 3DP phantoms as EVAR trainers, and one publication examined the technology as a tool for patient education. Flexible, transparent phantoms were deemed most useful; however, the cost and availability of higher end machines limited accessibility.

CONCLUSION

3DP phantoms have been used in EVAR to facilitate visualization of complex patient anatomy, appropriate device selection, in predicting navigational difficulties and the shape and position of endograft after deployment. These phantoms show promise in reducing known complications such as endoleak, stent graft occlusion and migration; however, larger scale prospective studies are required to validate its impacts on patient outcomes and cost savings to the healthcare system.

A systematic review of three-dimensional printed template-assisted physician-modified stent grafts for fenestrated endovascular aneurysm repair

OBJECTIVE

Fenestrated endovascular aneurysm repair has yet to gain widespread adoption owing to the technical complexity and increased risk of complications. Three-dimensional (3D) printed templates to guide fenestrated physician-modified stent grafts (PMSGs) are a novel technique that may have the potential to increase the accuracy of fenestration alignment, and to disrupt both the cost and timing of the current commercial fenestrated endograft supply chain. We have conducted a critical appraisal of the emerging literature to assess this.

METHODS

A systematic literature search was performed using PubMed and OVID Medline as guided by the PRISMA statement on April 30, 2020. We used "3D printing" and "physician modified" or "surgeon modified" and all related search terms. We identified 50 articles which met our search criteria. None articles were included as being of direct relevance to 3D-printed template-assisted PMSGs for fenestrated endovascular aneurysm repair. Abstracts were screened individually by each investigator to ensure relevance.

RESULTS

Nine relevant articles were identified for critical analysis. These included one technical report, five case reports or series, two prospective trials, and one letter to the editor.

CONCLUSIONS

These 3D-printed templates are a promising new avenue to assist with the placement of fenestrations in PMSGs, particularly in urgent or emergent cases where custom fenestrated endografts are unavailable, with larger scale studies warranted. Further work to validate the key stages of the template workflow are required, as well as further investigation into the most suitable manufacturing and distribution methods before the mainstream implementation of this novel technique.

Off-pump coronary artery bypass grafting for patients with severely reduced ventricular function-A justified strategy?

BACKGROUND AND AIM

Low ejection fraction (EF) has been identified as a main risk factor for perioperative complications and mortality after coronary artery bypass grafting (CABG). The purpose of this study was to compare the efficacy and early as well as midterm outcomes of off-pump CABG (OPCAB) and conventional CABG (ONCAB) surgery in patients with reduced EF.

METHODS

We performed a retrospective review of patient demographics, preoperative risk factors, operative and postoperative outcomes of patients with left ventricular EF (LV-EF) ≤35%, who underwent CABG at our institution between January 2015 and December 2017. Propensity score and multivariate logistic regression analysis were used to compare risk adjusted outcomes between groups.

RESULTS

Overall, 111 consecutive CABG-patients with LV-EF ≤ 35% underwent either ONCAB (46 patients, 41.4%) or OPCAB surgery (65 patients, 58.6%). There was no difference in early mortality (5% vs. 7.5%, p = .64) between groups. After propensity score matching, OPCAB-patients required significantly less re-sternotomies for bleeding (20% vs. 2.5%, p = .03) and consequently received significantly less blood transfusions (57.5% vs. 32.5%, p = .03). Fewer OPCAB-patients experienced low cardiac output syndrome (22.5% vs. 42.5%, p = .06) and suffered from postoperative delirium (22.5% vs. 42.5%, p = .06). There were no differences in completeness of revascularization between groups (median 1 (1.0-1.33; 1.0-1.33) OPCAB versus median 1 (1-1.33; 0.67-2) ONCAB, p = .95). Survival after 6 months, one year and three years was similar for ONCAB- and OPCAB-patients (ONCAB 92.3%, 89.4%, and 89.4% vs. OPCAB 89.8%, 85.7%, and 82.1%; p = .403). More ONCAB-patients needed a coronary re-intervention during follow-up (8.6% vs. 2.3%, p = .402).

CONCLUSION

OPCAB-surgery is a safe and effective option for patients with reduced EF. Furthermore, it does not come at the expense of less complete revascularization or increased coronary re-intervention during early follow-up.

Accessing 3D Printed Vascular Phantoms for Procedural Simulation

Introduction: 3D printed patient-specific vascular phantoms provide superior anatomical insights for simulating complex endovascular procedures. Currently, lack of exposure to the technology poses a barrier for adoption. We offer an accessible, low-cost guide to producing vascular anatomical models using routine CT angiography, open source software packages and a variety of 3D printing technologies.

Methods: Although applicable to all vascular territories, we illustrate our methodology using Abdominal Aortic Aneurysms (AAAs) due to the strong interest in this area. CT aortograms acquired as part of routine care were converted to representative patient-specific 3D models, and then printed using a variety of 3D printing technologies to assess their material suitability as aortic phantoms. Depending on the technology, phantoms cost $20–$1,000 and were produced in 12–48 h. This technique was used to generate hollow 3D printed thoracoabdominal aortas visible under fluoroscopy.

Results: 3D printed AAA phantoms were a valuable addition to standard CT angiogram reconstructions in the simulation of complex cases, such as short or very angulated necks, or for positioning fenestrations in juxtarenal aneurysms. Hollow flexible models were particularly useful for device selection and in planning of fenestrated EVAR. In addition, these models have demonstrated utility other settings, such as patient education and engagement, and trainee and anatomical education. Further study is required to establish a material with optimal cost, haptic and fluoroscopic fidelity.

Conclusion: We share our experiences and methodology for developing inexpensive 3D printed vascular phantoms which despite material limitations, successfully mimic the procedural challenges encountered during live endovascular surgery. As the technology continues to improve, 3D printed vascular phantoms have the potential to disrupt how endovascular procedures are planned and taught.

Numerical simulation of fenestrated graft deployment: Anticipation of stent graft and vascular structure adequacy

Fenestrated endovascular aneurism repair (FEVAR) is a minimally invasive technique, and its success depends on the adequacy of the correspondence between the visceral arteries ostia and position of the fenestrations of the stent graft (SG) during its deployment in juxtarenal aneurisms. However, the fenestration position is generally determined from a preoperative computerised tomography (CT) scan, without considering the vascular deformation induced by the insertion of the endovascular tools. Catheterisation difficulties may occur during clinical procedures. Accordingly, the objective of this work is to present an initial proof of concept aimed at anticipating and optimising the position of the fenestrations, while considering the vascular deformation induced by the insertion of the endovascular tools. The proposed method relies on the finite element method to simulate the SG deployment in a vascular structure (VS), and considers the vascular deformation induced by the tools. After determining the optimal simulation parameters for a patient-specific case, the robustness of the method is demonstrated on six other representative anatomies. The simulated SG is also compared with post-deployment CT observations, and demonstrates good adequacy. The results show that the numerically corrected fenestration positions, as determined from the simulated results following the insertion of the endovascular tools, deviate from those of the standard plan (as determined from the preoperative CT scan). This indicates that the SG-VS adequacy could be improved via simulation-based planning, to anticipate potential catheterisation difficulties.

The Italian Multicentre Registry of Fenestrated Anaconda™ Endografts for Complex Abdominal Aortic Aneurysms Repair

OBJECTIVE

The aim was to describe the outcomes of the Anaconda™ Fenestrated endograft Italian Registry for complex aortic aneurysms (AAAs), unsuitable for standard endovascular aneurysm repair (EVAR).

METHODS

Between 2012 and 2018 patients with a proximal neck unsuitable for standard EVAR, treated with the fenestrated Anaconda™ endograft, were prospectively enrolled in a dedicated database. Endpoints were peri-operative technical success (TS) and evaluation of type Ia/b or 3 endoleaks (T1/3 EL), target visceral vessel (TVV) occlusion, re-interventions, and AAA related mortality at 30 days, six months, and later follow up.

RESULTS

One hundred twenty seven patients (74 ± 7 years, American Society Anesthesiology (ASA) II/III/IV: 12/85/30) were included in the study in 49 Italian Vascular Surgery Units (83 juxta/para-renal AAA, 13 type IV thoraco-abdominal AAA, 16 T1aEL post EVAR, and 15 short neck AAA). Configurations with one, two, three, and four fenestrations were used in 5, 56, 39, and 27 cases, respectively, for a total of 342 visceral vessels. One hundred and eight (85%) bifurcated and 19 (15%) tube endografts were implanted. In 35% (44/127) of cases the endograft was repositioned during the procedure, and 37% (128/342) of TVV were cannulated from brachial access. TS was 87% (111/127): five T1EL, six T3EL (between fenestration and vessel stent), and six loss of visceral vessels (one patient with a Type Ia EL had also a TVV loss) occurred. Thirty day mortality was 4% (5/127). Two of the five T1EL resolved spontaneously at 30 days. The overall median follow up was 21 ± 16 months; one T1EL (5%) occurred at six months and one T3EL (4%) at the three year follow up. Another two (3%) TVV occlusions occurred at six months and five (3%) at three years. The re-intervention rate at the 30 days, six months, and three year follow up was 5%, 7%, and 18 ± 5%, respectively.

CONCLUSION

The fenestrated Anaconda™ endograft is effective in the treatment of complex AAA. Some structure properties, such as the re-positionability and the possibility of cannulation from above, are specific characteristics helpful for the treatment of some complex anatomies.

Assessment of Pull-out Forces in TEVAR and ANACONDA FEVAR Combination and Early Clinical Results: Creation of a Proximal Landing Zone for FEVAR in Patients with Extent I and Extent IV TAAAs

BACKGROUND

Although recent data on the treatment of thoracoabdominal aortic aneurysms (TAAAs) are promising, in some cases, the paravisceral segment of the aorta may not be suitable for a branched endograft due to space restrictions. A combination of a fenestrated aneurysm repair (FEVAR) with a thoracic aneurysm repair (TEVAR) may represent a feasible treatment option. The current investigation was performed to assess the stability of a fenestrated Anaconda device implanted into a set of thoracic endografts from different manufacturers. We then assessed our clinical results with the FEVAR/TEVAR combination.

METHODS

Pull-out forces were measured in vitro after docking a fenestrated Anaconda graft within the distal end of different TEVAR devices. Anaconda devices were implanted in 28- or 30-mm thoracic tube grafts (oversizing of at least 2 mm: 13.3-21.4; minimum overlap of 15 mm). Continuously increasing longitudinal pull forces of up to 100 N were applied on an Instron Tensile Tester. Initial break point and damage to the endografts were documented. Clinical results of patients treated with such an FEVAR/TEVAR combination at our institution are presented as a second part of this study.

RESULTS

Median pull-out forces ranged from 2.38 N to 55.0 N. The highest stability was achieved with 34-mm Anaconda devices in 28-mm thoracic tube grafts. Grafts with either thinner Dacron material or those featuring a polytetrafluorethylene membrane seemed especially vulnerable to punctures and tears caused by the downward-looking hooks of the Anaconda device. Between April 1, 2013 and December 31, 2018, in 28 of 172 patients treated with a fenestrated Anaconda device, prior implantation of a thoracic tube graft was necessary to create a sufficient proximal landing zone. In 25 cases (89.3%), the aneurysm was successfully treated. Although the 30-day reintervention rate in this subgroup was relatively high at 28.6%, none of these was due to a failure of the FEVAR/TEVAR combination. Upon an average follow-up of 15 months, no failure of the graft connection and no type III endoleak due to membrane damage were observed.

CONCLUSIONS

The combination of a thoracic tube graft and a fenestrated Anaconda device is a viable option for the treatment of patients with Extent I or IV TAAAs with no adequate landing zone above the celiac trunk. Although pull-out testing has shown good stability with most assessed grafts, the thoracic devices with thicker Dacron membranes seemed to be especially suitable.

Trends in use of 3D printing in vascular surgery: a survey

INTRODUCTION

The purpose of the following research was to provide a systematic survey on the use of additive manufacturing in vascular surgery. The survey focuses on applications of 3D printing in endovascular surgery like endovascular aneurysm repair (EVAR), a quite unexplored application domain. 3D printing is an additive production process of three-dimensional objects starting from a three-dimensional digital model. This kind of manufacturing process is getting great attention in the medical field and new applications have emerged in recent years especially thanks to the combination of additive printing with 3D imaging techniques. The purpose of the study is to reflect on additive manufacturing and its potential as an inclusive manufacturing practice which can provide benefits at economic and societal level.

EVIDENCE ACQUISITION

The article first introduces the use of 3D printing in surgery by summarizing the results of previous reviews which reveal three main usages of 3D printing: anatomic models, surgical tools, implants and prostheses. These studies point out that vascular surgery is still an unexplored field of application of 3D printing. Starting from this result, a new survey was carried out in databases Pubmed, Elsevier, Research Gate and ACM Digital Library for terms related to 3D printing in vascular surgery using the following keywords: 3D printing, vascular surgery, EVAR, aneurysm. The search screened articles published up to 2019 for relevance and practical application of the technology in vascular surgery, in particular the topic is related to the treatment of complex abdominal aortic aneurysm.

EVIDENCE SYNTHESIS

Initially 437 records published up to 2019 were found, but then were narrowed down to 29 full-text articles. The findings reveal that in addition to the applications found in the previous studies, new experiments are ongoing related to the use of 3D printing in the "Off label" practice to manually fenestrate the stent to improve the accuracy of the EVAR.

CONCLUSIONS

Different applications of the use of 3D printing and digital imaging in vascular surgery have been experimented with a different maturity level. Whilst the technology has increased its potential in the latest years, the number of studies documented in the literature is still quite narrow. Further research is necessary to fully test the potential of 3D printing, also in combination with other technologies (e.g. 3D imaging and CNC cutting). Early experimentations show that these technologies have the potential to radically change the vascular surgery practice in the near future, in particular in treatment like EVAR, to improve the planning and therefore the success of the surgery.

Simulation of Endovascular Aortic Repair Using 3D Printed Abdominal Aortic Aneurysm Model and Fluid Pump

BACKGROUND

Abdominal aortic aneurysm (AAA) models can be manufactured with 3D printing technology. This study describes detailed methodology and validation of endovascular aortic repair (EVAR) simulation using 3D printed AAA model connected to hemodynamic pump.

METHOD

The AAA model was printed with Objet500 Connex3 (Stratasys, Eden Prairie, MN) and connected to BDC PD-0500 fluid pump (BDC Laboratories, Wheat Ridge, CO). EVAR procedure metrics were benchmarked in two expert implanters and compared to 20 vascular surgical trainees with different levels of EVAR experience (< 20 or ≥ 20 cases). All simulations were performed using commercially available stent grafts, guidewires, catheters, fluoroscopic guidance and digital subtraction angiography. Studied outcomes included ability to complete the procedure independently, time to deploy aortic component, ability to cannulate contralateral gate and complete the repair, and total fluoroscopy and procedure times.

RESULTS

A total of 22 EVAR simulation procedures were performed with mean procedure time of 37 ± 12 min. Experienced trainees had significantly lower total procedural time (32 ± 9 vs. 44 ± 6 min, P = 0.003) and fluoroscopic time (13 ± 5 vs. 23 ± 8 min, P = 0.005). All experienced trainees completed the procedure independently in < 45 min, compared to six (46%) of those with less EVAR experience (P = 0.016). Among less experienced trainees, only two (15%) completed the entire procedure independently (P < 0.001). Benchmark implanters performed significantly better than both trainee groups in nearly all EVAR metrics.

CONCLUSION

EVAR simulation was feasible and simulated all procedural steps with high fidelity. This model may be applicable for assessment of technical competencies and standard endovascular skill acquisition within vascular surgery training curricula.

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): guidelines for medical 3D printing and appropriateness for clinical scenarios

Medical three-dimensional (3D) printing has expanded dramatically over the past three decades with growth in both facility adoption and the variety of medical applications. Consideration for each step required to create accurate 3D printed models from medical imaging data impacts patient care and management. In this paper, a writing group representing the Radiological Society of North America Special Interest Group on 3D Printing (SIG) provides recommendations that have been vetted and voted on by the SIG active membership. This body of work includes appropriate clinical use of anatomic models 3D printed for diagnostic use in the care of patients with specific medical conditions. The recommendations provide guidance for approaches and tools in medical 3D printing, from image acquisition, segmentation of the desired anatomy intended for 3D printing, creation of a 3D-printable model, and post-processing of 3D printed anatomic models for patient care.

Principles of three-dimensional printing and clinical applications within the abdomen and pelvis

Improvements in technology and reduction in costs have led to widespread interest in three-dimensional (3D) printing. 3D-printed anatomical models contribute to personalized medicine, surgical planning, and education across medical specialties, and these models are rapidly changing the landscape of clinical practice. A physical object that can be held in one's hands allows for significant advantages over standard two-dimensional (2D) or even 3D computer-based virtual models. Radiologists have the potential to play a significant role as consultants and educators across all specialties by providing 3D-printed models that enhance clinical care. This article reviews the basics of 3D printing, including how models are created from imaging data, clinical applications of 3D printing within the abdomen and pelvis, implications for education and training, limitations, and future directions.

Artificial vascular models for endovascular training (3D printing)

The endovascular technique has led to a revolution in the care of patients with vascular disease; however, acquiring and maintaining proficiency over a broad spectrum of procedures is challenging. Three-dimensional (3D) printing technology allows the production of models that can be used for endovascular training. This article aims to explain the process and technologies available to produce vascular models for endovascular training, using 3D printing technology. The data are based on the group experience and a review of the literature. Different 3D printing methods are compared, describing their advantages, disadvantages and potential roles in surgical training. The process of 3D printing a vascular model based on an imaging examination consists of the following steps: image acquisition, image post-processing, 3D printing and printed model post-processing. The entire process can take a week. Prospective studies have shown that 3D printing can improve surgical planning, especially in complex endovascular procedures, and allows the production of efficient simulators for endovascular training, improving residents’ surgical performance and self-confidence.

A 3-Dimensional Printed Aortic Arch Template to Facilitate the Creation of Physician-Modified Stent-Grafts

PURPOSE

To demonstrate the utility of a 3-dimensional (3D) printed template of the aortic arch in the construction of a fenestrated and scalloped physician-modified stent-graft (PMSG).

CASE REPORT

A 73-year-old woman with descending thoracic aneurysm was scheduled for thoracic endovascular aortic repair after being disqualified for open surgery. Computed tomography angiography (CTA) revealed no proximal landing zone as the aneurysm began from the level of the left subclavian artery, so a fenestrated/scalloped PMSG was planned. To facilitate accurate placement of the openings in the graft, a 3D printed aortic arch template was prepared from the CTA data and gas sterilized. In the operating room, a Valiant stent-graft was inserted into the 3D printed template and deployed. Using ophthalmic cautery, a fenestration and a scallop were created; radiopaque markers were added. The PMSG was successfully deployed with no discrepancy between the openings and the target vessels.

CONCLUSION

A 3D printed aortic arch template facilitates handmade fenestrations and scallops in PMSGs and may improve accuracy and quality.

The Role of Three-Dimensional Printing in Contemporary Vascular and Endovascular Surgery: A Systematic Review

BACKGROUND

Three-dimensional (3D) printing, also known as rapid prototyping or additive manufacturing, is a novel adjunct in the medical field. The aim of this systematic review is to evaluate the role of 3D printing technology in the field of contemporary vascular surgery in terms of its technical aspect, practicability, and clinical outcome.

METHODS

A systematic search of literatures published from January 1, 1980 to July 15, 2017 was identified from the EMBASE, MEDLINE, and Cochrane library database with reference to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. The predefined selection inclusion criterion was clinical application of 3D printing technology in vascular surgery of large and small vessel pathology.

RESULTS

Forty-two articles were included in this systematic review, including 2 retrospective cohorts and 1 prospective case control study. 3D printing was mostly applied to abdominal aortic aneurysm (n = 20) and thoracic aorta pathology (n = 8), other vessels included celiac, splenic, carotid, subclavian, femoral artery, and portal vein (n = 10). The most commonly quoted materials were acrylonitrile-butadiene-styrene (n = 2), polylactic acid (n = 4), polyurethane resin (n = 3) and nylon (n = 3). The cost per replica ranged from USD $4-2,360. Cost for a commercial printer was around USD $2,210-50,000.

CONCLUSION

3D printing was recognized and gradually incorporated as a useful adjunct in the field of vascular and endovascular surgery. The production of an accurate anatomic patient-specific replica was shown to bring significant impact in patient management in terms of anatomic understanding, procedural planning, and intraoperative navigation, education, and academic research as well as patient communication. Further analysis on cost-effectiveness was indicated to guide decisions on applicability of such promising technology on a routine basis.

Three-dimensional (3D) printing and its applications for aortic diseases

Three-dimensional (3D) printing is a process which generates prototypes from virtual objects in computer-aided design (CAD) software. Since 3D printing enables the creation of customized objects, it is a rapidly expanding field in an age of personalized medicine. We discuss the use of 3D printing in surgical planning, training, and creation of devices for the treatment of aortic diseases. 3D printing can provide operators with a hands-on model to interact with complex anatomy, enable prototyping of devices for implantation based upon anatomy, or even provide pre-procedural simulation. Potential exists to expand upon current uses of 3D printing to create personalized implantable devices such as grafts. Future studies should aim to demonstrate the impact of 3D printing on outcomes to make this technology more accessible to patients with complex aortic diseases.