Development and Validation of Medical Decision Tools in Detection and Treatment of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a permanent dilatation of the infrarenal segment of the abdominal aorta which can be fatal if the aneurysm ruptures. Ruptured AAA is the second leading cause of global surgical mortality, and prophylactic AAA repair can decrease mortality by a tenfold if surgery is performed as an elective procedure. While screening and repair of AAA could potentially reduce AAA-related mortality, selecting patients that are likely to benefit from repair remains a complex medical decision process which has been compounded by an improved life expectancy of the general population, minimal invasive treatment methods and the increased prevalence of AAA in the elderly. The overall aim of this thesis was to improve detection and management of AAA and to develop a predictive decision tool that can assist in clinical management. This thesis has been conducted, to shed some light into issues highlighted above using New Zealand and international data. The format of this thesis was categorized into three main domains: First, the prevalence of AAA and the influence of aortic size on late survival was documented in a large cohort of individuals undergoing CT colonography for gastrointestinal symptoms in Canterbury, New Zealand; Second, a systematic review and meta-analysis of prognostic factors that might influence late survival following AAA repair were performed, and the national clinical and administrative AAA repair databases were interrogated to provide epidemiological and outcome data; Third, the factors identified from this review were applied into developing a discrete event-simulation model to predict survival following AAA repair. The model developed has been externally validated against existing national databases of patients undergoing AAA repair and it appears sufficiently accurate to predict five- year survival. The results and conclusions presented throughout this thesis fill some of the gap in AAA knowledge, and such predictive decision-making tools might help improve AAA management

One-year follow-up after active aortic aneurysm sac treatment with shape memory polymer devices during endovascular aneurysm repair

Objective: To determine the safety and efficacy of treating abdominal aortic aneurysm (AAA) sacs with polyurethane shape memory polymer (SMP) devices during endovascular aneurysm repair (EVAR), using a technique to fully treat the target lumen after endograft placement (aortic flow volume minus the endograft volume). SMP devices self-expand in the sac to form a porous scaffold that supports thrombosis throughout its structure. Methods: Two identical prospective, multicenter, single-arm studies were conducted in New Zealand and the Netherlands. The study population was adult candidates for elective EVAR of an infrarenal AAA (diameter of ≥55 mm in men and ≥50 mm in women). Key exclusion criteria were an inability to adequately seal a common iliac artery aneurysm, patent sac feeding vessels of &gt;4 mm, and a target lumen volume of &lt;20 mL or &gt;135 mL. Target lumen volumes were estimated by subtracting endograft volumes from preprocedural imaging-based flow lumen volumes. SMP devices were delivered immediately after endograft deployment via a 6F sheath jailed in a bowed position in the sac. The primary efficacy end point was technical success, defined as filling the actual target lumen volume with fully expanded SMP at the completion of the procedure. Secondary efficacy outcome measures during follow-up were the change in sac volume and diameter, rate of type II endoleak and type I or III endoleaks, and the rate of open repair and related reinterventions, with data collection at 30 days, 6 months, and 1 year (to date). Baseline sac volumes and diameters for change in sac size analyses were determined from 30-day imaging studies. Baseline and follow-up volumes were normalized by subtraction of the endograft volume. Results: Of 34 patients treated with SMP devices and followed per protocol, 33 patients were evaluable at 1 year. Preprocedural aneurysm volume was 181.4 mL (95% confidence interval [CI], 150.7-212.1 mL) and preprocedural aneurysm diameter was 60.8 mm (95% CI, 57.8-63.9 mm). The target lumen volume was 56.3 mL (95% CI, 46.9-65.8 mL). Technical success was 100% and the ratio of SMP fully expanded volume to estimated target lumen volume was 1.4 ± 0.3. Baseline normalized sac volume and diameter were 140.7 mL (95% CI, 126.6-154.9 mL) and 61.0 mm (95% CI, 59.7-62.3 mm). The adjusted mean percentage change in normalized volume at 1 year was −28.8% (95% CI, −35.3 to −22.3%; P &lt; .001). The adjusted mean change in sac diameter at 1 year was −5.9 mm (95% CI, −7.5 to −4.4 mm; P &lt; .001). At 1 year, 81.8% of patients (95% CI, 64.5%-93.0%) achieved a ≥10% decrease in normalized volume and 57.6% of patients (95% CI, 39.2%-74.5%) achieved a ≥5 mm decrease in diameter. No device- or study procedure-related major adverse events occurred through 1 year after the procedure. Conclusions: Treatment of AAA sacs with SMP devices during EVAR resulted in significant sac volume and diameter regression at 1 year with an acceptable safety profile in this prospective study.</p

The impact of COVID-19 pandemic on vascular registries and clinical trials.

Quality improvement programs and clinical trial research experienced disruption due to the coronavirus disease 2019 (COVID-19) pandemic. Vascular registries showed an immediate impact with significant declines in second-quarter vascular procedure volumes witnessed across Europe and the United States. To better understand the magnitude and impact of the pandemic, organizations and study groups sent grass roots surveys to vascular specialists for needs assessment. Several vascular registries responded quickly by insertion of COVID-19 variables into their data collection forms. More than 80% of clinical trials have been reported delayed or not started due to factors that included loss of enrollment from patient concerns or mandated institutional shutdowns, weighing the risk of trial participation on patient safety. Preliminary data of patients undergoing vascular surgery with active COVID-19 infection show inferior outcomes (morbidity) and increased mortality. Disease-specific vascular surgery study collaboratives about COVID-19 were created for the desire to study the disease in a more focused manner than possible through registry outcomes. This review describes the pandemic effect on multiple VASCUNET registries including Germany (GermanVasc), Sweden (SwedVasc), United Kingdom (UK National Vascular Registry), Australia and New Zealand (bi-national Australasian Vascular Audit), as well as the United States (Society for Vascular Surgery Vascular Quality Initiative). We will highlight the continued collaboration of VASCUNET with the Vascular Quality Initiative in the International Consortium of Vascular Registries as part of the Medical Device Epidemiology Network coordinated registry network. Vascular registries must remain flexible and responsive to new and future real-world problems affecting vascular patients

Editor's Choice - The Impact of Centralisation and Endovascular Aneurysm Repair on Treatment of Ruptured Abdominal Aortic Aneurysms Based on International Registries

Objectives: Current management of ruptured abdominal aortic aneurysms (RAAA) varies among centres and countries, particularly in the degree of implementation of endovascular aneurysm repair (EVAR) and levels of vascular surgery centralisation. This study assesses these variations and the impact they have on outcomes. Materials and methods: RAAA repairs from vascular surgical registries in 11 countries, 2010-2013, were investigated. Data were analysed overall, per country, per treatment modality (EVAR or open aortic repair [OAR]), centre volume (quintiles IV), and whether centres were predominantly EVAR (>= 50% of RAAA performed with EVAR [EVAR(p)]) or predominantly OAR [OAR(p)]. Primary outcome was peri-operative mortality. Data are presented as either mean values or percentages with 95% CI within parentheses, and compared with chi-square tests, as well as with adjusted OR. Results: There were 9273 patients included. Mean age was 74.7 (74.5-74.9) years, and 82.7% of patients were men (81.9-83.6). Mean AAA diameter at rupture was 7.6 cm (7.5-7.6). Of these aneurysms, 10.7% (10.0-11.4) were less than 5.5 cm. EVAR was performed in 23.1% (22.3-24.0). There were 6817 procedures performed in OAR(p) centres and 1217 performed in EVAR(p) centres. Overall peri-operative mortality was 28.8% (27.9-29.8). Peri-operative mortality for OAR was 32.1% (31.0-33.2) and for EVAR 17.9% (16.3-19.6), p 22 repairs per year), 23.3% (21.2-25.4) than in QII-V, 30.0% (28.9-31.1), p <.001. Peri-operative mortality after OAR was lower in high volume centres compared with the other centres, 25.3% (23.0-27.6) and 34.0% (32.7-35.4), respectively, p <.001. There was no significant difference in peri-operative mortality after EVAR between centres based on volume. Conclusions: Peri-operative mortality is lower in centres with a primary EVAR approach or with high case volume. Most repairs, however, are still performed in low volume centres and in centres with a primary OAR strategy. Reorganisation of acute vascular surgical services may improve outcomes of RAAA repair. (C) 2018 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Transatlantic Delphi Consensus on the Common Iliac Artery Sealing Zone in Endovascular Aorto-Iliac Aneurysm Repair (the DECIDE Study)

Objective: Knowledge of hostile factors and their influence on long-term seal in the iliac landing zone is limited. Currently endorsed clinical practice guidelines lack structural evidence on how the iliac landing zone should be assessed in the pre-, intra-, and postoperative phases. The goal of this study was to obtain an international, expert-based consensus on the definition of a hostile iliac landing zone, on how to size and plan stent-grafts to optimize sustainable distal seal, and on the postprocedural follow-up protocol. Methods: Delphi consensus methodology was used, involving a panel of international vascular surgeons experienced in endovascular aneurysm repair (EVAR). The first round consisted of open-ended and multiple-choice questions to explore current practices, with subsequent rounds refining statements through a 4-point Likert scale. Consensus was defined as &gt;75% agreement or disagreement, and the analysis included stability testing and strength of consensus. Results: The study engaged 77 international vascular surgeons, reflecting diverse geographic locations and hospital affiliations. Consensus was achieved on critical preoperative planning elements for EVAR, including a clear definition for a hostile iliac landing zone. The importance of computed tomography angiography for postoperative follow-up imaging was emphasized, including evaluating distal seal length and recommending specific timing for follow-up computed tomography scans and intervention strategies for diminishing iliac seal. Conclusions: This international expert-based Delphi consensus establishes a comprehensive set of consensus-driven recommendations focused on the definition and management of hostile iliac landing zones in EVAR. The key recommendation of this study is the definition of a hostile iliac landing zone as short (&lt;15 mm), wide (&gt;24 mm), or conical (&gt;10% diameter difference along the landing zone). Although consensus was achieved on several critical aspects, the study also reveals ongoing debates and considerations that warrant further exploration, including how to tackle diminishing seal without a type IB endoleak. Clinical Impact: This Delphi consensus introduces a standardized definition of a hostile iliac landing zone as short (&lt;15 mm), wide (&gt;24 mm), or conical (&gt;10% diameter difference), clinicians now have a clearer framework for assessing complex anatomies. This study provides a comprehensive set of consensus-driven recommendations focused on the definition and management of hostile iliac landing zones in EVAR which gives guidance where current guidelines lack specificity, particularly for distal iliac sealing. The study also reveals ongoing debates and considerations that warrant further exploration, including how to tackle diminishing seal without a type IB endoleak.</p

Great saphenous vein versus expanded polytetrafluoroethylene graft in patients undergoing elective treatment of popliteal artery aneurysm with posterior approach

Background: Aim of this study is to compare 30-day and 5-year outcomes of great saphenous vein (GSV) vs. expanded polytetrafluoroethylene (ePTFE) graft in patients undergoing elective treatment of popliteal artery aneurysm (PAA) using a posterior approach. Methods: Between January 2010 and December 2023, a retrospectively maintained dataset of all consecutive asymptomatic PAAs who underwent open repair with posterior approach or endovascular repair in 40 centers was investigated. Out of of 971 cases, 525 patients were included in the present analysis. These were further divided into: posterior approach with GSV graft (252, GSV Group), and posterior approach with ePTFE graft (273, ePTFE Group). Thirty-day outcomes were assessed and compared. During follow-up, survival, primary patency, secondary patency, freedom from reintervention(s), and amputation-free survival were compared between the two groups using log-rank tests. Uni- and multivariate Cox regression analyses were performed in ePTFE Group to find predictive factors of poor outcomes. Results: Two groups were homogeneous in terms of preoperative risk factors and morphological data. Median follow-up duration was similar [24 months (IQR 10 - 36) GSV Group vs. 21 months (IQR 7-47) ePTFE Group; p = .123]. At 5 years, there were no differences between the two groups in terms of survival (84.7% GSV Group vs. 86.1% ePTFE Group; p = .097, log-rank = 2.756), secondary patency (94.9% GSV Group vs. 89.4% ePTFE Group; p = .068, log-rank = 3.336), and amputation-free survival (99.1% GSV Group vs. 99.6% ePTFE Group; p = .567, log-rank = .328). Five-year primary patency (89.5% GSV Group vs. 76.2% ePTFE Group; p = .007, log-rank = 7.239), and freedom from reintervention(s) (92.8% GSV Group vs. 80.6% ePTFE Group; p = .011, log-rank = 6.449) were significantly higher in GSV Group. Using multivariate analysis in ePTFE Group, factors compromising primary patency were patients on dialysis (p = .054, OR = 3.641), and patients that were not on any preoperative antiplatelet therapy or anticoagulation (p = .019, OR = 5.532), whilst none of the perioperative factors affected freedom from reintervention(s). Conclusion: GSV as graft guaranteed better primary patency with less reinterventions rates at mid-term follow-up after treatment of PAAs via a posterior approach. Patients on dialysis and who were not on any preoperative antiplatelet therapy or anticoagulation had lower patency rates

Long-term risk prediction after major lower limb amputation: 1-year results of the PERCEIVE study

Background: Decision-making when considering major lower limb amputation is complex and requires individualized outcome estimation. It is unknown how accurate healthcare professionals or relevant outcome prediction tools are at predicting outcomes at 1-year after major lower limb amputation. Methods: An international, multicentre prospective observational study evaluating healthcare professional accuracy in predicting outcomes 1 year after major lower limb amputation and evaluation of relevant outcome prediction tools identified in a systematic search of the literature was undertaken. Observed outcomes at 1 year were compared with: healthcare professionals' preoperative predictions of death (surgeons and anaesthetists), major lower limb amputation revision (surgeons) and ambulation (surgeons, specialist physiotherapists and vascular nurse practitioners); and probabilities calculated from relevant outcome prediction tools. Results: A total of 537 patients and 2244 healthcare professional predictions of outcomes were included. Surgeons and anaesthetists had acceptable discrimination (C-statistic = 0.715), calibration and overall performance (Brier score = 0.200) when predicting 1-year death, but performed worse when predicting major lower limb amputation revision and ambulation (C-statistics = 0.627 and 0.662 respectively). Healthcare professionals overestimated the death and major lower limb amputation revision risks. Consultants outperformed trainees, especially when predicting ambulation. Allied healthcare professionals marginally outperformed surgeons in predicting ambulation. Two outcome prediction tools (C-statistics = 0.755 and 0.717, Brier scores = 0.158 and 0.178) outperformed healthcare professionals' discrimination, calibration and overall performance in predicting death. Two outcome prediction tools for ambulation (C-statistics = 0.688 and 0.667) marginally outperformed healthcare professionals. Conclusion: There is uncertainty in predicting 1-year outcomes following major lower limb amputation. Different professional groups performed comparably in this study. Two outcome prediction tools for death and two for ambulation outperformed healthcare professionals and may support shared decision-making

Development and Validation of Medical Decision Tools in Detection and Treatment of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a permanent dilatation of the infrarenal segment of the abdominal aorta which can be fatal if the aneurysm ruptures. Ruptured AAA is the second leading cause of global surgical mortality, and prophylactic AAA repair can decrease mortality by a tenfold if surgery is performed as an elective procedure. While screening and repair of AAA could potentially reduce AAA-related mortality, selecting patients that are likely to benefit from repair remains a complex medical decision process which has been compounded by an improved life expectancy of the general population, minimal invasive treatment methods and the increased prevalence of AAA in the elderly. The overall aim of this thesis was to improve detection and management of AAA and to develop a predictive decision tool that can assist in clinical management. This thesis has been conducted, to shed some light into issues highlighted above using New Zealand and international data. The format of this thesis was categorized into three main domains: First, the prevalence of AAA and the influence of aortic size on late survival was documented in a large cohort of individuals undergoing CT colonography for gastrointestinal symptoms in Canterbury, New Zealand; Second, a systematic review and meta-analysis of prognostic factors that might influence late survival following AAA repair were performed, and the national clinical and administrative AAA repair databases were interrogated to provide epidemiological and outcome data; Third, the factors identified from this review were applied into developing a discrete event-simulation model to predict survival following AAA repair. The model developed has been externally validated against existing national databases of patients undergoing AAA repair and it appears sufficiently accurate to predict five- year survival. The results and conclusions presented throughout this thesis fill some of the gap in AAA knowledge, and such predictive decision-making tools might help improve AAA management