Development of an Artificial Intelligence Tool for Intraoperative Guidance During Endovascular Abdominal Aortic Aneurysm Repair.

BACKGROUND: Adverse events during surgery can occur in part due to errors in visual perception and judgment. Deep learning is a branch of artificial intelligence (AI) that has shown promise in providing real-time intraoperative guidance. This study aims to train and test the performance of a deep learning model that can identify inappropriate landing zones during endovascular aneurysm repair (EVAR). METHODS: A deep learning model was trained to identify a "No-Go" landing zone during EVAR, defined by coverage of the lowest renal artery by the stent graft. Fluoroscopic images from elective EVAR procedures performed at a single institution and from open-access sources were selected. Annotations of the "No-Go" zone were performed by trained annotators. A 10-fold cross-validation technique was used to evaluate the performance of the model against human annotations. Primary outcomes were intersection-over-union (IoU) and F1 score and secondary outcomes were pixel-wise accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). RESULTS: The AI model was trained using 369 images procured from 110 different patients/videos, including 18 patients/videos (44 images) from open-access sources. For the primary outcomes, IoU and F1 were 0.43 (standard deviation ± 0.29) and 0.53 (±0.32), respectively. For the secondary outcomes, accuracy, sensitivity, specificity, NPV, and PPV were 0.97 (±0.002), 0.51 (±0.34), 0.99 (±0.001). 0.99 (±0.002), and 0.62 (±0.34), respectively. CONCLUSIONS: AI can effectively identify suboptimal areas of stent deployment during EVAR. Further directions include validating the model on datasets from other institutions and assessing its ability to predict optimal stent graft placement and clinical outcomes.

Assessing the robustness of negative vascular surgery randomized controlled trials using their reverse fragility index.

OBJECTIVE: The reverse fragility index (RFI) describes the number of event conversions needed to convert a statistically nonsignificant dichotomous outcome to a significant one. The objective of the present study was to assess the RFI of vascular surgery randomized controlled trials (RCTs) comparing endovascular vs open surgery for the treatment of abdominal aortic aneurysms (AAAs), carotid artery stenosis (CAS), and peripheral artery disease (PAD). METHODS: MEDLINE and Embase were searched for RCTs that had investigated AAAs, CAS, or PAD with statistically nonsignificant binary primary outcomes. The primary outcome for the present study was the median RFI. Calculation of the RFI was performed by creating two-by-two contingency tables and subtracting events from the group with fewer events and adding nonevents to the same group until a two-tailed Fisher exact test had produced a statistically significant result (P ≤ .05). RESULTS: Of 4187 reports, 49 studies reporting 103 different primary end points were included. The overall median RFI was 7 (interquartile range [IQR], 5-13). The specific RFIs for AAA, CAS, and PAD were 10 (IQR, 6-15.5), 6 (IQR, 5-9.5), and 7 (IQR, 5.5-10), respectively. Of the 103 end points, 42 (47%) had had a loss to follow-up greater than the RFI, of which 10 were AAA trials (24%), 23 were CAS trials (55%), and 9 were PAD trials (21%). The Pearson correlation demonstrated a significant positive relationship between a study's RFI and the impact factor of its publishing journal (r = 0.38; 95% confidence interval [CI], 0.20-0.54; P < .01), length of follow-up (r = 0.43; 95% CI, 0.26-0.58; P < .01), and sample size (r = 0.28; 95% CI, 0.09-0.45; P < .01). CONCLUSIONS: A small number of events (median, 7) was required to change the outcome of negative RCTs from statistically nonsignificant to significant, with 47% of the studies having missing data that could have reversed the finding of its primary outcome. Reporting of the RFI relative to the loss to follow-up could be of benefit in future trials and provide confidence regarding the robustness of the P value.

Using machine learning to predict outcomes following open abdominal aortic aneurysm repair.

OBJECTIVE: Prediction of outcomes following open abdominal aortic aneurysm (AAA) repair remains challenging with a lack of widely used tools to guide perioperative management. We developed machine learning (ML) algorithms that predict outcomes following open AAA repair. METHODS: The Vascular Quality Initiative (VQI) database was used to identify patients who underwent elective open AAA repair between 2003 and 2023. Input features included 52 preoperative demographic/clinical variables. All available preoperative variables from VQI were used to maximize predictive performance. The primary outcome was in-hospital major adverse cardiovascular event (MACE; composite of myocardial infarction, stroke, or death). Secondary outcomes were individual components of the primary outcome, other in-hospital complications, and 1-year mortality and any reintervention. We split our data into training (70%) and test (30%) sets. Using 10-fold cross-validation, six ML models were trained using preoperative features (Extreme Gradient Boosting [XGBoost], random forest, Naïve Bayes classifier, support vector machine, artificial neural network, and logistic regression). The primary model evaluation metric was area under the receiver operating characteristic curve (AUROC). Model robustness was evaluated with calibration plot and Brier score. The top 10 predictive features in our final model were determined based on variable importance scores. Performance was assessed on subgroups based on age, sex, race, ethnicity, rurality, median area deprivation index, proximal clamp site, prior aortic surgery, and concomitant procedures. RESULTS: Overall, 12,027 patients were included. The primary outcome of in-hospital MACE occurred in 630 patients (5.2%). Compared with patients without a primary outcome, those who developed in-hospital MACE were older with more comorbidities, demonstrated poorer functional status, had more complex aneurysms, and were more likely to require concomitant procedures. Our best performing prediction model for in-hospital MACE was XGBoost, achieving an AUROC of 0.93 (95% confidence interval, 0.92-0.94). Comparatively, logistic regression had an AUROC of 0.71 (95% confidence interval, 0.70-0.73). For secondary outcomes, XGBoost achieved AUROCs between 0.84 and 0.94. The calibration plot showed good agreement between predicted and observed event probabilities with a Brier score of 0.05. These findings highlight the excellent predictive performance of the XGBoost model. The top three predictive features in our algorithm for in-hospital MACE following open AAA repair were: (1) coronary artery disease; (2) American Society of Anesthesiologists classification; and (3) proximal clamp site. Model performance remained robust on all subgroup analyses. CONCLUSIONS: Open AAA repair outcomes can be accurately predicted using preoperative data with our ML models, which perform better than logistic regression. Our automated algorithms can help guide risk-mitigation strategies for patients being considered for open AAA repair to improve outcomes.

Machine learning to predict outcomes following endovascular abdominal aortic aneurysm repair.

BACKGROUND: Endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) carries important perioperative risks; however, there are no widely used outcome prediction tools. The aim of this study was to apply machine learning (ML) to develop automated algorithms that predict 1-year mortality following EVAR. METHODS: The Vascular Quality Initiative database was used to identify patients who underwent elective EVAR for infrarenal AAA between 2003 and 2023. Input features included 47 preoperative demographic/clinical variables. The primary outcome was 1-year all-cause mortality. Data were split into training (70 per cent) and test (30 per cent) sets. Using 10-fold cross-validation, 6 ML models were trained using preoperative features with logistic regression as the baseline comparator. The primary model evaluation metric was area under the receiver operating characteristic curve (AUROC). Model robustness was evaluated with calibration plot and Brier score. RESULTS: Some 63 655 patients were included. One-year mortality occurred in 3122 (4.9 per cent) patients. The best performing prediction model for 1-year mortality was XGBoost, achieving an AUROC (95 per cent c.i.) of 0.96 (0.95-0.97). Comparatively, logistic regression had an AUROC (95 per cent c.i.) of 0.69 (0.68-0.71). The calibration plot showed good agreement between predicted and observed event probabilities with a Brier score of 0.04. The top 3 predictive features in the algorithm were 1) unfit for open AAA repair, 2) functional status, and 3) preoperative dialysis. CONCLUSIONS: In this data set, machine learning was able to predict 1-year mortality following EVAR using preoperative data and outperformed standard logistic regression models.

Editor's Choice - Meta-Analysis of Compliance with Endovascular Aneurysm Repair Surveillance: The EVAR Surveillance Paradox.

OBJECTIVE: To compare the survival of patients who attended surveillance after endovascular aneurysm repair (EVAR) with those who were non-compliant. DATA SOURCES: MEDLINE and Embase were searched using the Ovid interface. REVIEW METHODS: A systematic review was conducted complying with the PRISMA guidelines. Eligible studies compared survival in EVAR surveillance compliant patients with non-compliant patients. Non-compliance was defined as failure to attend at least one post-EVAR follow up. The risk of bias was assessed with the Newcastle-Ottawa scale, and the certainty of evidence using the GRADE framework. Primary outcomes were survival and aneurysm related death. Effect measures were the hazard ratio (HR) or odds ratio (OR) and 95% confidence interval (CI) calculated using the inverse variance or Mantel-Haenszel statistical method and random effects models. RESULTS: Thirteen cohort studies with a total of 22 762 patients were included. Eight studies were deemed high risk of bias. The pooled proportion of patients who were non-compliant with EVAR surveillance was 43% (95% CI 36 - 51). No statistically significant difference was found in the hazard of all cause mortality (HR 1.04, 95% CI 0.61 - 1.77), aneurysm related mortality (HR 1.80, 95% CI 0.85-3.80), or secondary intervention (HR 0.66, 95% CI 0.31 - 1.41) between patients who had incomplete and complete follow up after EVAR. The odds of aneurysm rupture were lower in non-compliant patients (OR 0.63, 95% CI 0.39 - 1.01). The certainty of evidence was very low for all outcomes. Subgroup analysis for patients who had no surveillance vs. those with complete surveillance showed no significant difference in all cause mortality (HR 1.10, 95% CI 0.43 - 2.80). CONCLUSION: Patients who were non-compliant with EVAR surveillance had similar survival to those who were compliant. These findings question the value of intense surveillance in all patients post-EVAR and highlight the need for further research on individualised or risk adjusted surveillance.

The Impact of Sex on Outcomes following Carotid Endarterectomy.

BACKGROUND: Previous studies have demonstrated significant sex differences in vascular surgery outcomes. We assessed stroke or death rates following carotid endarterectomy (CEA) in women versus men. METHODS: The Vascular Quality Initiative was used to identify all patients who underwent CEA between 2010 and 2019. Demographic, clinical, and procedural characteristics were recorded and differences between women and men were assessed using independent t-test and chi-squared test. The primary outcomes were 30-day and 1-year stroke or death. Associations between sex and outcomes were assessed using univariate/multivariate logistic regression and Cox proportional hazards analysis. RESULTS: Overall, 52,137 women and 79,974 men underwent CEA in Vascular Quality Initiative sites during the study period. Women were younger (70.3 vs. 70.5 years, P < 0.001) and more likely to have hypertension (89.2% vs. 88.9%, P < 0.05) and diabetes (36.2% vs. 35.8%, P < 0.001) but less likely to be diagnosed with coronary artery disease (23.2% vs. 31.0%, P < 0.001). A greater proportion of men were receiving cardiovascular risk reduction medications and had symptomatic carotid stenosis (28.5% vs. 26.7%, P < 0.001). Women had shorter procedure times (113 vs. 122 min, P < 0.001) and were less likely to receive electroencephalography neuromonitoring (27.9% vs. 28.8%, P < 0.001), drain (35.9% vs. 37.3%, P < 0.001), and protamine (67.4% vs. 68.0%, P < 0.01). Stroke or death at 30 days (1.9% vs. 1.8%, P = 0.60) and 1 year (hazard ratio [HR] 0.98, 95% confidence interval [CI] 0.94-1.01, P = 0.20) were similar between groups, which persisted in asymptomatic patients (HR 0.97, 95% CI 0.93-1.01, P = 0.17) and symptomatic patients (HR 0.99, 95% CI 0.93-1.05, P = 0.71). The similarities in 1-year stroke or death rates existed in both the United States (HR 0.96, 95% CI 0.92-1.01, P = 0.09) and Canada (HR 1.21, 95% CI 0.47-3.11, P = 0.70). CONCLUSIONS: Despite sex differences in clinical and procedural characteristics, women and men have similar 30-day and 1-year outcomes following CEA.

Management and In-hospital Mortality of 2203 Patients With a Traumatic Intimal Tear of the Thoracic Aorta.

OBJECTIVE: Our goal was to describe contemporary management and inhospital mortality associated with blunt thoracic aortic intimal tears (IT) within the American College of Surgeons Trauma Quality Improvement Program. SUMMARY BACKGROUND DATA: The evidence basis for nonoperative expectant management of traumatic iT of the thoracic aorta remains weak. METHODS: All adult patients with a thoracic aortic IT following blunt trauma were captured from Level I and II North American Centers enrolled in Trauma Quality Improvement Program from 2010 to 2017. For each patient, we extracted demographics, injury characteristics, the timing and approach of thoracic aortic repair and in-hospital mortality. Mortality attributable to IT was calculated by comparing IT patients to a propensity-score matched control cohort of severely injured blunt trauma patients without aortic injury. RESULTS: There were 2203 IT patients across 315 facilities. Injury most often resulted from motor vehicle collision (75%). A total of 758 patients (34%) underwent operative management, with 93% (N = 708) of repairs performed via an endovascular approach. Median time to surgery was 11 hours (IQR 4- 40). The frequency of operative management was higher in patients without traumatic brain injury (TBI) (35%, N = 674) compared to those with TBI (29%, N = 84) (P = 0.024). Compared to severely injured blunt trauma patients without aortic injury, ITwas not associated with additional in-hospital mortality (10.7% for IT vs 11.7% for no IT, absolute risk difference: -1.0%, 95% CI: -2.9% to 0.8%). CONCLUSIONS: The majority of blunt thoracic IT are managed nonoperatively and IT does not confer additional in-hospital mortality risk. Future studies should focus on the risk of injury progression.

Thresholds for abdominal aortic aneurysm repair in Canada and United States.

BACKGROUND: Previous studies have demonstrated significant geographic variations in the management of abdominal aortic aneurysms (AAA) despite standard guidelines. Differences in patient selection, operative technique, and outcomes for AAA repair in Canada versus United States were assessed. METHODS: The Vascular Quality Initiative was used to identify all patients who underwent elective endovascular or open AAA repair between 2010 and 2019 in Canada and the United States. Demographic, clinical, and procedural characteristics were recorded and differences between countries were assessed using independent t test and χ2 test. The primary outcome was the percentage of AAA repaired below recommended diameter thresholds (men, <5.5 cm; women, <5.0 cm). The secondary outcomes were in-hospital and 1-year mortality rates. Associations between region and outcomes were assessed using univariate/multivariate logistic regression and Cox proportional hazards analysis. RESULTS: There were 51,455 U.S. patients and 1451 Canadian patients who underwent AAA repair in Vascular Quality Initiative sites during the study period. There was a higher proportion of endovascular repairs in the United States (83.7% vs 68.4%; odds ratio [OR], 2.38; 95% confidence interval [CI], 2.13-2.63; P < .001). U.S. patients had more comorbidities, including hypertension, congestive heart failure, chronic kidney disease, and prior revascularization. The percentage of AAA repaired below recommended thresholds was significantly higher in the United States (38.8% vs 15.2%; OR, 3.57; 95% CI, 3.03-4.17; P < .001). This difference persisted after controlling for demographic, clinical, and procedural characteristics (adjusted OR, 3.57; 95% CI, 2.63-4.17; P < .001). Factors that predicted AAA repair below recommended thresholds were U.S. region (adjusted OR, 3.57; 95% CI, 3.03-4.17), male sex (adjusted OR, 2.89; 95% CI, 2.72-3.07), and endovascular repair (adjusted OR, 2.08; 95% CI, 1.95-2.21). The in-hospital mortality rate was low (1.0% vs 0.8%) and the 1-year rate mortality was similar between countries (hazard ratio, 0.96; 95% CI, 0.70-1.31; P = .79). CONCLUSIONS: There are significant variations in AAA management between Canada and the United States. A greater proportion of U.S. patients underwent AAA repair below the recommended diameter thresholds. This finding is partly driven by a higher percentage of endovascular repairs. Despite these differences, the perioperative and 1-year mortality rates are similar. Future studies should investigate reasons for these variations and quality improvement projects are needed to standardize care.

Analysis of spin in vascular surgery randomized controlled trials with nonsignificant outcomes.

OBJECTIVE: Spin is the manipulation of language that distorts the interpretation of objective findings. The purpose of this study is to describe the characteristics of spin found in statistically nonsignificant randomized controlled trials (RCT) comparing carotid endarterectomy with carotid artery stenting for carotid artery stenosis (CS), and endovascular repair with open repair (OR) for abdominal aortic aneurysms (AAA). METHODS: A search of MEDLINE, EMBASE, and the Cochrane Controlled Register of Trials was performed in June 2020 for studies published describing AAA or CS. All phase III RCTs with nonsignificant primary outcomes comparing open repair with endovascular repair or carotid endarterectomy to carotid artery stenting were included. Studies were appraised for the characteristics and severity of spin using a validated tool. Binary logistic regression was performed to assess the association of spin grade to (1) funding source (commercial vs noncommercial) and (2) the publishing journal's impact factor. RESULTS: Thirty-one of 355 articles captured were included for analysis. Spin was identified in 9 abstracts (9/18) and 13 main texts (13/18) of AAA articles and 7 abstracts (7/13) and 10 main texts (10/13) of CS articles. For both AAA and CS articles, spin was most commonly found in the discussion section, with the most commonly used strategy being the interpretation of statistically nonsignificant primary results to show treatment equivalence or rule out adverse treatment effects. Increasing journal impact factor was associated with a statistically significant lower likelihood of spin in the study title or abstract conclusion (ß odds ratio, 0.96; 95% confidence interval, 0.94-0.98; P < .01); no significant association could be found with funding source (ß odds ratio, 1.33; 95% confidence interval, 0.30-5.92; P = .71). CONCLUSIONS: A large proportion of statistically nonsignificant RCTs contain interpretations that are inconsistent with their results. These findings should prompt authors and readers to appraise study findings independently and to limit the use of spin in study interpretations.

Trends in operative case volumes of Canadian vascular surgery trainees.

OBJECTIVE: Vascular surgery has evolved with increasing use of endovascular therapies and a decline in open surgery. The influence of these changes, in addition to a new vascular surgery training program introduced in 2012, on case volumes of vascular trainees is not known. We sought to evaluate trends in operative case volumes of Canadian vascular surgery trainees. METHODS: A survey was administered to graduates of the Canadian Royal College-accredited Vascular Fellowships (VFs) and Integrated Vascular Surgery Residency (IVSR) programs (2007-2019) to record cases performed during their final 2 years of training. Procedures of interest were open abdominal aortic aneurysm (oAAA) repair, open thoracic/thoracoabdominal aortic (oTAA/TAAA) repair, lower extremity bypass (LEB), carotid endarterectomy (CEA), lower extremity endovascular intervention (LEEI), and endovascular abdominal, advanced, and thoracic aortic repair (EVAR, aEVAR, and TEVAR). Case volumes were analyzed overall, and by graduation year, type of training program, and resident demographics. RESULTS: A total of 60 participants (10% female) from all the 10 Canadian training institutions responded (response rate, 63%). There was a declining trend in overall procedures performed since the introduction of IVSR in 2012 (median, 427 [interquartile range (IQR), 304-496] in 2007-2012 vs median, 342 [IQR, 279-405] in 2013-2019; P = .055), driven by a significant decline in open vascular surgery cases (median, 273 [IQR, 221-339] in 2007-2012 vs median, 156 [IQR, 128-181] in 2013-2019; P = .001). Case volumes of oAAA, LEB, and CEA declined by 44%, 40%, and 45%, respectively. Compared with vascular fellows, IVSR residents logged ∼2.5 times more aEVARs (median, 8; IQR, 2-11 vs median, 19; IQR, 8-27; P = .001) and ∼1.5 times more LEEIs (median, 60; IQR, 40-99 vs median, 93; IQR, 69-120; P = .018). Trainees were most confident (range, 90%-100%) in performing oAAA, EVAR, LEB, LEEI, and CEA after training, and least confident in performing oTAA/TAAA and aEVAR (20% and 49% confidence, respectively). CONCLUSIONS: Operative case volumes of Canadian vascular surgery trainees since the introduction of IVSR program in 2012 have decreased, driven by declining exposure to open cases. However, trainees continue to receive adequate operative exposure to perform most standard vascular procedures confidently upon graduation.

Risk factors associated with long-term mortality and complications after thoracoabdominal aortic aneurysm repair.

OBJECTIVE: We sought to determine the risk factors associated with late mortality or complications (thoracoabdominal aortic aneurysm [TAAA] life-altering events [TALE]: a composite of mortality, permanent paraplegia, permanent dialysis, and stroke) for patients who had undergone endovascular or open TAAA repair. METHODS: We performed a population-based study of patients who had undergone TAAA repair in Ontario, Canada, from 2006 to 2017. The association of baseline risk factors with mortality and complications after repair was examined using Cox hazards models with hospital-specific random effects. The survival of patients who had undergone TAAA repair was compared with that of controls without TAAAs. The two groups were matched by age, sex, area of residence, and average annual household income. The type of repair (endovascular vs open) was included in all models. RESULTS: We identified 664 adults (mean age, 69.3 ± 10.6 years; 71% men) who had undergone TAAA repair. At 5 and 8 years, survival was 55.0% (95% confidence interval [CI], 49.8%-60.1%) and 44.6% (95% CI, 40.4%-49.6%) for patients who had undergone TAAA repair vs 85.6% (95% CI, 83.9%-87.1%) and 76.3% (95% CI, 73.8%-78.8%) for the control population, respectively (hazard ratio [HR], 1.97; 95% CI, 1.67-2.32; P < .01). For the TAAA group, freedom from TALE was 49.2% (95% CI, 44.7%-53.7%) and 37.3% (95% CI, 33.1%-42.4%) at 5 and 8 years of follow-up, respectively. On multivariable analysis, the risk factors associated with mortality during follow-up included older age (HR, 1.21 per 5-year increase; 95% CI, 1.13-1.28), peripheral artery disease (HR, 1.46; 95% CI, 1.03-2.09), hypertension (HR, 1.58; 95% CI, 1.03-2.43), congestive heart failure (HR, 1.78; 95% CI, 1.34-2.36), and urgent procedures (HR, 2.27; 95% CI, 1.74-3.00). A lower rate of death was observed for those with previous coronary revascularization (HR, 0.63; 95% CI, 0.41-0.96) and those who had undergone repair at high-volume institutions (>60 TAAA repairs during the study period; HR, 0.71; 95% CI, 0.55-0.91). Older age, chronic kidney disease, congestive heart failure, and urgent procedures were associated with a higher rate of TALE. The type of repair (endovascular vs open) was not associated with mortality or TALE. CONCLUSIONS: TAAA repair was associated with reduced long-term survival compared with the general population, regardless of the mode of treatment. Urgent or emergent repair was the most profound risk factor for late adverse events. The type of repair (endovascular vs open) was not a predictor of long-term death or complications. Previous coronary revascularization and treatment performed at a high-volume institution were associated with improved late outcomes for patients undergoing TAAA repair.

Society for Vascular Surgery clinical practice guidelines for management of extracranial cerebrovascular disease.

Management of carotid bifurcation stenosis in stroke prevention has been the subject of extensive investigations, including multiple randomized controlled trials. The proper treatment of patients with carotid bifurcation disease is of major interest to vascular surgeons and other vascular specialists. In 2011, the Society for Vascular Surgery published guidelines for the treatment of carotid artery disease. At the time, several randomized trials, comparing carotid endarterectomy (CEA) and carotid artery stenting (CAS), were reported. Since the 2011 guidelines, several studies and a few systematic reviews comparing CEA and CAS have been reported, and the role of medical management has been reemphasized. In the present publication, we have updated and expanded on the 2011 guidelines with specific emphasis on five areas: (1) is CEA recommended over maximal medical therapy for low-risk patients; (2) is CEA recommended over transfemoral CAS for low surgical risk patients with symptomatic carotid artery stenosis of >50%; (3) the timing of carotid intervention for patients presenting with acute stroke; (4) screening for carotid artery stenosis in asymptomatic patients; and (5) the optimal sequence of intervention for patients with combined carotid and coronary artery disease. A separate implementation document will address other important clinical issues in extracranial cerebrovascular disease. Recommendations are made using the GRADE (grades of recommendation assessment, development, and evaluation) approach, as was used for other Society for Vascular Surgery guidelines. The committee recommends CEA as the first-line treatment for symptomatic low-risk surgical patients with stenosis of 50% to 99% and asymptomatic patients with stenosis of 70% to 99%. The perioperative risk of stroke and death in asymptomatic patients must be <3% to ensure benefit for the patient. In patients with recent stable stroke (modified Rankin scale score, 0-2), carotid revascularization is considered appropriate for symptomatic patients with >50% stenosis and should be performed as soon as the patient is neurologically stable after 48 hours but definitely <14 days after symptom onset. In the general population, screening for clinically asymptomatic carotid artery stenosis in patients without cerebrovascular symptoms or significant risk factors for carotid artery disease is not recommended. In selected asymptomatic patients with an increased risk of carotid stenosis, we suggest screening for clinically asymptomatic carotid artery stenosis as long as the patients would potentially be fit for and willing to consider carotid intervention if significant stenosis is discovered. For patients with symptomatic carotid stenosis of 50% to 99%, who require both CEA and coronary artery bypass grafting, we suggest CEA before, or concomitant with, coronary artery bypass grafting to potentially reduce the risk of stroke and stroke/death. The sequencing of the intervention depends on the clinical presentation and institutional experience.

A Systematic Review and Bibliometric Analysis of Applications of Artificial Intelligence and Machine Learning in Vascular Surgery.

BACKGROUND: Artificial intelligence (AI) and machine learning (ML) have seen increasingly intimate integration with medicine and healthcare in the last 2 decades. The objective of this study was to summarize all current applications of AI and ML in the vascular surgery literature and to conduct a bibliometric analysis of published studies. METHODS: A comprehensive literature search was conducted through Embase, MEDLINE, and Ovid HealthStar from inception until February 19, 2021. Reporting of this study was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Title and abstract screening, full-text screening, and data extraction were conducted in duplicate. Data extracted included study metadata, the clinical area of study within vascular surgery, type of AI/ML method used, dataset, and the application of AI/ML. Publishing journals were classified as having either a clinical scope or technical scope. The author academic background was classified as clinical, nonclinical (e.g., engineering), or both, depending on author affiliation. RESULTS: The initial search identified 7,434 studies, of which 249 were included for a final analysis. The rate of publications is exponentially increasing, with 158 (63%) studies being published in the last 5 years alone. Studies were most commonly related to carotid artery disease (118, 47%), abdominal aortic aneurysms (51, 20%), and peripheral arterial disease (26, 10%). Study authors employed an average of 1.50 (range: 1-6) distinct AI methods in their studies. The application of AI/ML methods broadly related to predictive models (54, 22%), image segmentation (49, 19.4%), diagnostic methods (46, 18%), or multiple combined applications (91, 37%). The most commonly used AI/ML methods were artificial neural networks (155/378 use cases, 41%), support vector machines (64, 17%), k-nearest neighbors algorithm (26, 7%), and random forests (23, 6%). Datasets to which these AI/ML methods were applied frequently involved ultrasound images (87, 35%), computed tomography (CT) images (42, 17%), clinical data (34, 14%), or multiple datasets (36, 14%). Overall, 22 (9%) studies were published in journals specific to vascular surgery, with the majority (147/249, 59%) being published in journals with a scope related to computer science or engineering. Among 1,576 publishing authors, 46% had exclusively a clinical background, 48% a nonclinical background, and 5% had both a clinical and nonclinical background. CONCLUSIONS: There is an exponentially growing body of literature describing the use of AI and ML in vascular surgery. There is a focus on carotid artery disease and abdominal aortic disease, with many other areas of vascular surgery under-represented. Neural networks and support vector machines composed most AI methods in the literature. As AI/ML continue to see expanded applications in the field, it is important that vascular surgeons appreciate its potential and limitations. In addition, as it sees increasing use, there is a need for clinicians with expertise in AI/ML methods who can optimize its transition into daily practice.

Rates of Intervention for Claudication versus Chronic Limb-Threatening Ischemia in Canada and United States.

BACKGROUND: Previous studies have demonstrated important geographic variations in peripheral artery disease (PAD) management despite existing guidelines. We assessed differences in patient characteristics, procedural technique, and outcomes for PAD interventions in Canada versus United States. METHODS: The Vascular Quality Initiative (VQI) was used to identify all patients who underwent endovascular intervention or surgical bypass for PAD between 2010 and 2019 in Canada and United States. Independent t-test and chi-square test were performed to assess differences between countries in terms of demographic, clinical, and procedural characteristics. The primary outcome was the percentage of interventions performed for claudication versus chronic limb-threatening ischemia (CLTI). Perioperative outcomes were in-hospital mortality and index limb amputation. The long-term outcome was 1-year amputation-free survival. Univariate/multivariate logistic regression and Cox proportional hazards analysis were performed to investigate associations between region and outcomes. RESULTS: A total of 246,770 US patients and 3,467 Canadian patients underwent revascularization for PAD during the study period. There was a higher proportion of endovascular interventions in the US (75.9% vs. 69.2%, OR 1.41 [95% CI 1.31-1.51], P< 0.001). American patients were younger with more comorbidities, including hypertension, diabetes, and coronary artery disease. The percentage of interventions performed for claudication was significantly higher in the US (42.3% vs. 35.7%, OR 1.31 [95% CI 1.22-1.44], P< 0.001). This persisted after controlling for demographic, clinical, and procedural characteristics (adjusted OR 1.05 [95% CI 1.01-1.10], P = 0.02). Perioperative outcomes were similar between countries after adjustment for baseline differences: in-hospital mortality (adjusted OR 1.07 [95% CI 0.69-1.62], P= 0.75) and index limb amputation (adjusted OR 0.67 [95% CI 0.43-1.07], P= 0.09). However, 1-year amputation-free survival was higher in the US (84.1% vs. 71.0%, HR 1.61 [95% CI 1.47-1.76], P< 0.001). Multivariable Cox proportional hazards analysis demonstrated that the factor most strongly associated with index limb amputation or death at 1-year was intervention for CLTI (HR 1.56 [95% CI 1.54-1.58], P< 0.001). CONCLUSIONS: There are significant variations in PAD management between US and Canada. In particular, a higher proportion of interventions are performed for claudication rather than CLTI in the US compared to Canada. This is an important contributor to the higher 1-year amputation-free survival rate in US patients. Reasons for these differences should be assessed by future studies and evidence-based care may be standardized by targeted quality improvement projects.

Symptom Status of Patients Undergoing Carotid Endarterectomy in Canada and United States.

BACKGROUND: Previous studies have demonstrated significant geographic variations in the management of carotid artery stenosis despite standard guidelines. To further characterize these practice variations, we assessed differences in patient selection, operative technique, and outcomes for carotid endarterectomy (CEA) in Canada vs. United States. METHODS: The Vascular Quality Initiative (VQI) was used to identify all patients who underwent CEA between 2010 and 2019 in Canada and United States. Demographic, clinical, and procedural characteristics were recorded and differences between countries were assessed using independent t-test and chi-square test. The primary outcome was the percentage of CEA performed for asymptomatic versus symptomatic disease. The secondary outcomes were 30-day and long-term stroke or death. Associations between country and outcomes were assessed using univariate/multivariate logistic regression and Cox proportional hazards analysis. RESULTS: During the study period, 131,411 US patients and 701 Canadian patients underwent CEA in VQI sites. Patients from the US were older with more comorbidities including hypertension, diabetes, congestive heart failure, and chronic kidney disease. The use of a shunt, patch, drain, or protamine was less common in the US. Most patients had 70 - 99% stenosis, with no difference between regions. The percentage of CEA performed for asymptomatic disease was significantly higher in the US even after adjusting for demographic, clinical, and procedural characteristics (72.4% vs. 30.7%, adjusted OR 3.91 [95% CI 3.21 - 4.78], p < 0.001). Thirty-day stroke/death was low (1.8% vs. 1.9%) and 1-year stroke/death was similar between groups (HR 0.98 [95% CI 0.69 - 1.39], P = 0.89). The similarities in 1-year stroke/death persisted in asymptomatic patients (HR 0.70 [95% CI 0.37 - 1.30], P = 0.26) and symptomatic patients (HR 1.14 [95% CI 0.74 - 1.73], P = 0.56). CONCLUSIONS: There are significant variations in CEA practice between Canada and US. In particular, most US patients are treated for asymptomatic disease, whereas most Canadian patients are treated for symptomatic disease. Furthermore, adjunctive procedures including shunting, patch use, and protamine administration are performed less commonly in the US. Despite these differences, perioperative and 1-year stroke/death rates are similar between countries. Future studies should investigate reasons for these variations and quality improvement projects are needed to standardize care.

Outcomes of abdominal aortic aneurysm repair among patients with rheumatoid arthritis.

OBJECTIVE: In the present study, we compared the outcomes of elective abdominal aortic aneurysm (AAA) repair in patients with and without rheumatoid arthritis (RA) stratified by the type of surgery. METHODS: A retrospective population-based cohort study was conducted from 2003 to 2016. Linked administrative health data from Ontario, Canada were used to identify all patients aged ≥65 years who had undergone elective open or endovascular AAA repair during the study period. Patients were identified using validated procedure and billing codes and matching using propensity scores. The primary outcome was survival. The secondary outcomes were major adverse cardiovascular events (MACE)-free survival (defined as freedom from death, myocardial infarction, and stroke), reintervention, and secondary rupture. RESULTS: Of 14,816 patients undergoing elective AAA repair, a diagnosis of RA was present for 309 (2.0%). The propensity-matched cohort included 234 pairs of RA and control patients. The matched cohort was followed up for a mean ± standard deviation of 4.93 ± 3.35 years, and the median survival was 6.76 and 7.31 years for the RA and control groups, respectively. Cox regression analysis demonstrated no statistically significant differences in the hazards for death, MACE, reintervention, or secondary rupture. Analysis of the differences in outcomes stratified by repair approach also showed no statistically significant differences in the hazards for death, MACE, reintervention, or secondary rupture. CONCLUSIONS: We found no statistically significant differences in survival, MACE, reintervention, or secondary rupture among patients with RA undergoing elective AAA repair compared with controls. Further studies are required to evaluate the impact of comorbidities and antirheumatic medications on the outcomes of elective AAA repair.

Health care costs of endovascular compared with open thoracoabdominal aortic aneurysm repair.

OBJECTIVE: To compare 1-year health care costs between endovascular and open thoracoabdominal aortic aneurysm (TAAA). METHODS: Population-based administrative health databases were used to capture TAAA repairs performed in Ontario, Canada, between January 2006 and February 2017. All health care costs incurred by the Ministry of Health from a single-payer universal health care system were included. Costs of the aortic endografts and ancillary devices for the index procedure were estimated as C$44,000 per endovascular case vs C$1000 for open cases, based on previous reports. Costs (2017 Canadian dollars) were calculated in phases (1, 1-3, 3-6, and 6-12 months from surgery) with censoring for death. For each phase, propensity score matching of endovascular and open cases based on preoperative patient and hospital characteristics was used. The association between preoperative characteristics (including repair approach) and the first month postprocedure cost was characterized through multivariable analysis. RESULTS: Overall 664 TAAA repairs were identified (open, n = 361 [54.5%] and endovascular, n = 303 [45.6%]). At 1 month, the median cost was higher for endovascular TAAA repair in the prematching cohort (C$64,892 vs C$36,647; P < .01). Similarly, in 241 well-balanced endovascular/open patient pairs after propensity score matching, the median health care costs were higher in endovascular TAAA cases during the first month (C$62,802 vs C$33,605; P < .01). The 1- to 3-month median cost was not statistically different between endovascular and open TAAA cases either before matching (C$2781 vs C$2618; P = .71) or after matching (C$2762 vs C$2092; P = .58). Likewise, in the 3- to 6-month and 6- to 12-month postprocedure intervals, there were no significant differences in the median health care costs between groups. On multivariable analysis, older age (5-year increments) (relative change [RC] in mean cost, 1.05; 95% confidence interval [CI], 1.04-1.06; P = .01), urgent procedures (RC, 1.29; 95% CI, 1.10-1.52; P < .01), and history of stroke (RC, 1.34; 95% CI, 1.00-1.78; P = .05) were associated with higher costs in the first postoperative month, whereas open relative to endovascular TAAA repair was associated with a decreased 1-month cost (RC, 0.65; 95% CI, 0.56-0.74; P < .01). CONCLUSIONS: TAAA repair is expensive regardless of technique. Compared with open TAAA repair, endovascular repair was associated with a higher early cost, owing to the upfront cost of the endograft and aortic ancillary devices. There was no difference in cost from 1 to 12 months after repair. A decrease in the cost of endovascular devices might allow equivalent costs between endovascular and open TAAA repair.

Reporting standards for endovascular aortic repair of aneurysms involving the renal-mesenteric arteries.

Endovascular aortic aneurysm repair of complex aortic aneurysms requires incorporation of side branches using specially designed aortic stent grafts with fenestrations, directional branches, or parallel stent grafts. These techniques have been increasingly used and reported in the literature. The purpose of this document is to clarify and to update terminology, classification systems, measurement techniques, and end point definitions that are recommended for reports dealing with endovascular repair of complex abdominal and thoracoabdominal aortic aneurysms involving the renal and mesenteric arteries.

Calibration of an Electrical Analog Model of Liver Hemodynamics in Fontan Patients.

Fontan associated liver disease is a common complication in patients with Fontan circulation, who were born with a single functioning heart ventricle. The hepatic venous pressure gradient (HVPG) is used to assess liver health and is a surrogate measure of the pressure gradient across the entire liver (portal pressure gradient (PPG)). However, it is thought to be inaccurate in Fontan patients. The main objectives of this study were (1) to apply an existing detailed lumped parameter model (LPM) of the liver to Fontan patients using patient-specific clinical data and (2) to determine whether HVPG is a suitable measurement of PPGs in these patients. An existing LPM of the liver blood circulation was applied and tuned to simulate patient-specific liver hemodynamics. Geometries were collected from seven adult Fontan patients and used to evaluate model parameters. The model was solved and tuned using waveform measurements of flows, inlet and outlet pressures. The predicted ratio of portal to hepatic venous pressures is comparable to in vivo measurements. The results confirmed that HVPG is not suitable for Fontan patients, as it would underestimate the portal pressures gradient by a factor of 3 to 4. Our patient-specific liver model provides an estimate of the pressure drop across the liver, which differs from the clinically used metric HVPG. This work represents a first step toward models suitable to assess liver health in Fontan patients and improve its long-term management.

Final results from a postmarket registry of an iliac leg graft with a continuous, spiral nitinol stent.

OBJECTIVE: To evaluate clinical outcomes from a postmarket registry of the Zenith Spiral-Z abdominal aortic aneurysm iliac leg graft with a continuous, spiral nitinol stent that was designed for improved conformability, kink, and migration resistance. METHODS: This prospective, multicenter registry was designed to evaluate physician-reported outcomes of the Spiral-Z leg graft in up to 600 patients who underwent endovascular repair of abdominal aortic or aortoiliac aneurysms at up to 30 investigative sites in the United States and Canada. Study outcomes were focused on iliac limb occlusion, limb-related reintervention, limb-related endoleak, component separation, and device integrity. Short-term data were collected during an interval of 1 to 6 months, with longer term data collected at 12 months. RESULTS: Between March 2012 and March 2015, 599 patients (mean age 74 ± 8 years; 87% male; 26% with aortoiliac aneurysm) were treated, with Spiral-Z iliac leg grafts placed in 564 left iliac arteries and 559 right iliac arteries. The mean iliac inner diameters (both left and right) were 9 ± 3 mm; moderate/severe occlusive disease, calcification, and vessel tortuosity were present in 14%, 25%, and 36% and 15%, 25%, and 34% of the left and right iliac arteries, respectively. Iliac artery adjunctive procedures (iliac artery angioplasty and/or stent placement) were performed intraoperatively in 112 patients (19%; bilateral in 52 patients). Mortality within 30 days was 1.7% (10/599); cumulative mortality at 1 year was 6.2% (37/599). There were no aortic ruptures and only one open conversion (0.2%). Limb occlusions occurred in 11 of 599 patients (2%; 3 within 30 days and 8 after 30 days, all unilateral, none had received procedural iliac artery adjuncts at implantation); of these, 7 patients underwent reinterventions. Other limb-related reinterventions were performed on eight patients for nonocclusive kink, compression, or thrombus (six within 30 days and three after 30 days). In total, 13 patients (2%) underwent 15 limb-related reinterventions (7 for occlusions and 8 for nonocclusive causes). In one patient, a distal type I endoleak and device migration (>10 mm) involving a right iliac leg was noted at the 12-month follow-up visit. No other limb-related endoleak, migration, component separation, or stent fracture was reported during a mean follow-up of 11 ± 6 months. CONCLUSIONS: The Spiral-Z leg graft demonstrated excellent patency and required infrequent limb-related reinterventions in routine clinical care in a postmarket registry.