A primer on cohort studies in vascular surgery research.

Vascular research questions can be answered using various study designs. Observational studies are used frequently to address a wide range of clinical questions when randomized clinical trials are not feasible or practical. One of the powerful vascular research tools is the cohort study. The cohort study is a reliable observational study design in which individuals who share a common characteristic (a cohort) are followed over time and their outcomes are assessed at various intervals. This review focuses on the essential characteristics, design, implementation, bias, validity, and clinical significance of cohort studies and provides illustrative examples. A cohort study can be either a prospective or a retrospective study, depending on whether the outcome occurred before or after the enrollment of the cohort. Each type has its advantages and disadvantages. Confounding, selection, and information biases can all occur in cohort studies. Applications of the cohort study design include studying the natural history of a disease, describing a condition's frequency, and investigating multiple outcomes simultaneously.

MRI in CFD for chronic type B aortic dissection: Ready for prime time?

OBJECTIVES: Better tools are needed for risk assessment of Type B aortic dissection (TBAD) to determine optimal treatment for patients with uncomplicated disease. Magnetic resonance imaging (MRI) has the potential to inform computational fluid dynamics (CFD) simulations for TBAD by providing individualised quantification of haemodynamic parameters, for assessment of complication risks. This systematic review aims to present an overview of MRI applications for CFD studies of TBAD. METHODS: Following PRISMA guidelines, a search in Medline, Embase, and the Scopus Library identified 136 potentially relevant articles. Studies were included if they used MRI to inform CFD simulation in TBAD. RESULTS: There were 20 articles meeting the inclusion criteria. 19 studies used phase contrast MRI (PC-MRI) to provide data for CFD flow boundary conditions. In 12 studies, CFD haemodynamic parameter results were validated against PC-MRI. In eight studies, geometric models were developed from MR angiography. In three studies, aortic wall or intimal flap motion data were derived from PC/cine MRI. CONCLUSIONS: MRI provides complementary patient-specific information in CFD haemodynamic studies for TBAD that can be used for personalised care. MRI provides structural, dynamic and flow data to inform CFD for pre-treatment planning, potentially advancing its integration into clinical decision-making. The use of MRI to inform CFD in TBAD surgical planning is promising, however further validation and larger cohort studies are required.

STABILISE; treatment of aortic dissection, a single Centre experience.

PURPOSE: To outline the process of the STABILISE technique and its use; reporting patient outcomes and midterm follow up for complicated aortic dissection. MATERIALS AND METHODS: Single centre retrospective analysis from January 2011 to January 2021 using the STABILISE technique which utilises balloon assistance to facilitate intimal disruption and promote aortic relamination. RESULTS: Sixteen patients underwent endovascular aortic repair with the STABILISE technique for aortic dissection over the study period. Fourteen patients (14/16; 88%) had acute dissection. Two of 16 (12%) were chronic. The median age of the patient cohort was 61 years (range 32-80 years) and consisted of a male majority (n = 11; 69%). The median time from diagnosis to intervention was 5 days (1-115 days; IQR 1-17.3). More than half (56%) had surgical repair of a acute type A aortic dissection prior to radiological intervention. The procedure was technically successful with no procedural mortality. Two patients were lost to follow up and two died in the post-operative period. Twelve patients had ongoing follow up with an average number of 2.9 ± 1.6 scans performed. Follow up was available in thirteen patients (81%) with a median follow up period of 1097 days (IQR 707-1657). The rate of re-intervention (n = 2/16; 13%) requiring additional stenting was in line with published re-intervention data (15%). Follow up showed a reduction in false lumen size following treatment with total luminal dimensions remaining stable over the follow-up period. CONCLUSION: The STABILISE technique as a procedure for complicated aortic dissection, either acute or chronic, appears safe with stable mid-term aortic remodelling and patient outcomes. LEVEL OF EVIDENCE: Level 3, Retrospective cohort study.

A look to the future: Pandemic-induced digital technologies in vascular surgery.

Like many areas of medicine, vascular surgery has been transformed by the COVID-19 (coronavirus disease 2019) pandemic. Public health precautions to minimize disease transmission have led to reduced attendance at hospitals and clinics in elective and emergency settings; fewer face-to-face and hands-on clinical interactions; and increased reliance on telemedicine, virtual attendance, investigations, and digital therapeutics. However, a "silver lining" to the COVID-19 pandemic may be the mainstream acceptance and acceleration of telemedicine, remote monitoring, digital health technology, and three-dimensional technologies, such as three-dimensional printing and virtual reality, by connecting health care providers to patients in a safe, reliable, and timely manner, and supplanting face-to-face surgical simulation and training. This review explores the impact of these changes in the delivery of vascular surgical care.

3D Printed Patient-Specific Complex Hip Arthroplasty Models Streamline the Preoperative Surgical Workflow: A Pilot Study.

Introduction: Surgical planning for complex total hip arthroplasty (THA) often presents a challenge. Definitive plans can be difficult to decide upon, requiring unnecessary equipment to be ordered and a long theatre list booked. We present a pilot study utilising patient-specific 3D printed models as a method of streamlining the pre-operative planning process. Methods: Complex patients presenting for THA were referred to the research team. Patient-specific 3D models were created from routine Computed Tomography (CT) imaging. Simulated surgery was performed to guide prosthesis selection, sizing and the surgical plan. Results: Seven patients were referred for this pilot study, presenting with complex conditions with atypical anatomy. Surgical plans provided by the 3D models were more detailed and accurate when compared to 2D CT and X ray imaging. Streamlined equipment selection was of great benefit, with augments avoided post simulation in three cases. The ability to tackle complex surgical problems outside of the operating theatre also flagged potential complications, while also providing teaching opportunities in a low risk environment. Conclusion: This study demonstrated that 3D printed models can improve the surgical plan and streamline operative logistics. Further studies investigating the optimal 3D printing material and workflow, along with cost-benefit analyses are required before this process is ready for routine use.

Open versus Endovascular Abdominal Aortic Aneurysm Repair in the Australian Private Sector Over Twenty Years.

PURPOSE: Over the past two decades, the proliferation of endovascular surgery has changed the approach to abdominal aortic aneurysm (AAA) repair. In Australia, close to two-thirds of surgical procedures are performed in the private healthcare system. We aimed to describe the trends in AAA repair in the Australian private sector throughout the early 21st century. MATERIALS AND METHODS: Medicare Benefits Schedule (MBS) statistics were accessed to determine the number of infrarenal open AAA repair (OAR) and endovascular AAA repair (EVAR) procedures performed between January 2000 and December 2019. Population data were extracted from the Australian Bureau of Statistics and used to calculate incidence per 100,000 population. Further analysis was performed according to age, gender, and state. RESULTS: During the study period, 13,193 (67.0%) EVARs and 6504 (33.0%) OARs were performed in the Australian private sector. OARs fell from 70.5% (n=567) of AAA repairs in 2000 to 15.7% (n=237) in 2019, while EVARs rose from 29.5% (n=151) to 84.3% (n=808). The frequency of EVAR surpassed OAR in 2004. The overall incidence of AAA repair varied minimally over the time period (range: 4.9-6.5 per 100,000 adults per year). AAA repair was more common in males than females (9.7 vs 1.7 per 100,000 population) and more common in older age groups. There was a 4-fold increase in EVAR among males older than 85 years (12.8-57.4 per 100,000 population), the largest rise of any group. The overall EVAR:OAR ratio increased from 0.4 to 5.4. There were considerable state-based discrepancies. CONCLUSION: The landscape of AAA repair in Australian private sector has drastically changed with a clear preference toward EVAR. EVAR saw increased use across all genders, age groups and states, despite stable rates of AAA surgery. Further research is necessary to compare our findings to national trends in the Australian public sector.

The strength of the online vascular community during the COVID-19 pandemic.

The spread of coronavirus disease 2019 has drastically altered the medical landscape and profoundly affected the way we conduct our vascular surgery practices. The pandemic was a time of change, not only in the way health care was provided, but also in how people in the health care systems interacted. Social media has rapidly become a crucial communication tool, combining physical distancing and digital connectedness. This article provides an overview of the use of online platforms in vascular surgery as a response of our community to the pandemic.

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.

Teaching Radial Endobronchial Ultrasound with a Three-Dimensional-printed Radial Ultrasound Model.

BACKGROUND: Peripheral pulmonary lesion (PPL) incidence is rising because of increased chest imaging sensitivity and frequency. For PPLs suspicious for lung cancer, current clinical guidelines recommend tissue diagnosis. Radial endobronchial ultrasound (R-EBUS) is a bronchoscopic technique used for this purpose. It has been observed that diagnostic yield is impacted by the ability to accurately manipulate the radial probe. However, such skills can be acquired, in part, from simulation training. Three-dimensional (3D) printing has been used to produce training simulators for standard bronchoscopy but has not been specifically used to develop similar tools for R-EBUS. OBJECTIVE: We report the development of a novel ultrasound-compatible, anatomically accurate 3D-printed R-EBUS simulator and evaluation of its utility as a training tool. METHODS: Computed tomography images were used to develop 3D-printed airway models with ultrasound-compatible PPLs of "low" and "high" technical difficulty. Twenty-one participants were allocated to two groups matched for prior R-EBUS experience. The intervention group received 15 minutes to pretrain R-EBUS using a 3D-printed model, whereas the nonintervention group did not. Both groups then performed R-EBUS on 3D-printed models and were evaluated using a specifically developed assessment tool. RESULTS: For the "low-difficulty" model, the intervention group achieved a higher score (21.5 ± 2.02) than the nonintervention group (17.1 ± 5.7), reflecting 26% improvement in performance (P = 0.03). For the "high-difficulty" model, the intervention group scored 20.2 ± 4.21 versus 13.3 ± 7.36, corresponding to 52% improvement in performance (P = 0.02). Participants derived benefit from pretraining with the 3D-printed model, regardless of prior experience level. CONCLUSION: 3D-printing can be used to develop simulators for R-EBUS education. Training using these models significantly improves procedural performance and is effective in both novice and experienced trainees.

Accuracy of non-contrast quiescent-interval single-shot and quiescent-interval single-shot arterial spin-labelled magnetic resonance angiography in assessment of peripheral arterial disease in a diabetic population.

INTRODUCTION: Diabetic patients with peripheral arterial disease (PAD) are challenging to assess. Non-contrast magnetic resonance angiography (MRA) offers a safe alternative in patients with renal impairment. The study objective is to evaluate accuracy of lower limb quiescent-interval single-shot (QISS) MRA and pedal QISS-arterial spin-labelled (ASL) MRA for detection of significant stenosis in diabetic patients with PAD. METHODS: Combined QISS and QISS-ASL MRA was performed in 32 diabetic PAD patients (20 male, 12 female; mean 69 years; 8 with critical ischaemia). Two readers assessed haemodynamically significant (>50%) stenosis and diagnostic confidence on MRA, against digital subtraction angiography (DSA) as the reference standard, with subgroup analysis of patients with severe renal impairment (n = 7). Inter-reader agreement of stenosis and diagnostic confidence were evaluated. Test-retest reproducibility was evaluated in 10 subjects who underwent repeat MRA on a different day. RESULTS: At DSA, 262/645 segments (40.6%) had haemodynamically significant stenoses. MRA accuracy was 78.1% (478/612) and 75.6% (464/614), sensitivity 64.7% (161/249) and 77.5% (193/249), and specificity 87.3% (317/363) and 74.2% (271/365) for 2 readers. MRA accuracy was 80.9% and 80.7% for readers 1 and 2, respectively, in patients with severe renal impairment. QISS MRA but not pedal QISS-ASL MRA was considered of diagnostic image quality. Inter-reader agreement was moderate for stenosis (ĸ = 0.60) and diagnostic confidence (ĸ = 0.41). Test-retest reproducibility was high (ĸ = 0.87) and moderate (ĸ = 0.54) for individual readers. CONCLUSIONS: Quiescent-interval single-shot MRA has reasonable accuracy in a diabetic PAD population with high burden of disease, providing a non-contrast option in patients with renal impairment. QISS-ASL MRA requires further optimisation to be clinically feasible.

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.

Three-dimensional printing in orthopaedic preoperative planning improves intraoperative metrics: a systematic review.

BACKGROUND: Three-dimensional (3D) printing has seen increasing interest in surgery, where it improves the visualization of difficult anatomy in complex cases. This literature review investigates the benefits and limitations of 3D printed models in preoperative planning in the field of orthopaedic surgery. METHODS: A literature search was performed using the Ovid platform on the Embase and MEDLINE databases using the terms '3D printing', 'Orthopaedics' and 'Surgical Planning'. Studies using 3D printed models as a part of preoperative planning were included. All others were excluded. Data regarding the metrics used to assess the benefit of the use of 3D models, surgical outcome, and surgeon or patient opinion on the technology were extracted. RESULTS: A total of 41 studies resulted. Eight (19.5%) were case-control studies, the remainder were case reports or case series. Assessment of benefit was mostly subjective, although the case-control studies included objective metrics such as operation time, intraoperative blood loss and intraoperative fluoroscopy time. The use of 3D printing technology showed subjective benefit for both patient and surgeon as well as indicating clinically significant improvements in intraoperative metrics. CONCLUSION: Despite the current absence of large scale trials, 3D printing has clear benefits in preoperative planning, particularly when utilized in complex cases. A streamlined workflow for case selection, in-house model creation and preoperative rehearsals is still required to be developed before the process is ready for routine use. Evidence supports an improvement in intraoperative metrics and patient engagement but data to support improved clinical outcome is lacking.

Review of 20 years of vascular surgery research in Australasia: Defining future directions.

OBJECTIVES: High-quality research is fundamental to the advancement of surgical practice. Currently, there is no quantitative assessment of the research output of vascular surgeons in Australia and New Zealand. By conducting this bibliometric analysis, we aim to provide an objective representation of the trends in vascular surgery and guide future research. METHODS: A list of all current vascular surgeons in Australia and New Zealand was compiled from the Royal Australasian College of Surgeons 'Find a Surgeon' website tool and correlated with the Australia and New Zealand Society for Vascular Surgery database. A Scopus search of each surgeon's author profile over the last 20 years was conducted. RESULTS: In total, 2120 articles were published by 208 Australasian vascular surgeons between 1998 and July 2018, with an overall increase in publications over time. Audits or case series were the most published type of study and only 8% of the publications were of high-level evidence. The most popular topics were thoracoabdominal aortic pathologies (24%), followed by peripheral arterial disease (15%). Chronological analysis illustrates an increasing volume of peripheral arterial disease research over time and there is a clear trend towards more endovascular and hybrid surgery publications. The top 10 (5%) highest publishing authors by h-index account for 41% of all publications and 49% of all citations and are also responsible for producing significantly more high-level evidence research. CONCLUSION: Australasian vascular surgeons have made a significant contribution to medical research. However, the majority of these articles are of low-level evidence. In this time, there has been an increasing number of publications on endovascular and hybrid surgery in keeping with the trend in clinical practice. These areas, as well as research regarding peripheral arterial disease, show potential for high-evidence research in the future.