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.

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.

Prediction of bird-beak configuration in thoracic endovascular aortic repair preoperatively using patient-specific finite element simulations

Objectives

Formation of bird-beak configuration in thoracic endovascular aortic repair (TEVAR) has been shown to be correlated with the risk of complications such as type Ia endoleaks, stent graft migration, and collapse. The aim of this study was to use patient-specific computational simulations of TEVAR to predict the formation of bird-beak configuration preoperatively.

Methods

Patient-specific TEVAR computational simulations are developed using a retrospective cohort of patients treated for thoracic aortic aneurysm. The preoperative computed tomography images were segmented to develop three-dimensional geometry of the thoracic aorta. These geometries were used in finite element simulations of stent graft deployment during TEVAR. Simulated results were compared against the postoperative computed tomography images to assess the accuracy of simulations in predicting the proximal position of a deployed stent graft and presence of bird-beak. In cases with a bird-beak configuration, the length and angle of the bird-beak were measured and compared between the simulated and postoperative results.

Results

Twelve TEVAR patient cases were simulated. Computational simulations were able to accurately predict whether the proximal stent graft was fully apposed, proximal bare stents were protruded, or bird-beak configuration was present. In three cases with bird-beak configuration, simulations predicted the length and angle of the bird-beak with less than 10% and 24% error, respectively. Other factors such as a small aortic arch angle, small oversizing value, and landing zones close to the arch apex may have played a role in formation of bird-beak in these patients.

Conclusions

Computational simulations of TEVAR accurately predicted the proximal position of a deployed stent graft and the presence of bird-beak preoperatively. The computational models were able to predict the length and angle of bird-beak configurations with good accuracy. These simulations can provide insight into the surgical planning process with the goal of minimizing bird-beak occurrence.

A modeling framework for computational simulations of thoracic endovascular aortic repair

Thoracic endovascular aortic repair (TEVAR) is a minimally invasive treatment for thoracic aortic conditions including aneurysms and is associated with a number of postoperative stent graft related complications. Computational simulations of TEVAR have the potential to predict surgical outcomes and complications preoperatively. When using simulations for stent graft design and prediction of complications in a population, it is difficult to generalize patient-specific TEVAR computational models due to patient variability. This study proposes a novel modeling framework for creating realistic population-based computational models of TEVAR focused on aneurysms that allow for developing various clinically relevant geometric configurations and scenarios that are not easily attainable with limited patient data. The framework includes a methodology for developing population-based thoracic aortic geometries and defining age-dependent aortic tissue material models, as well as detailed steps and boundary conditions for finite element modeling of stent graft deployment during TEVAR. The simulation framework is illustrated for predicting the formation of a bird-beak configuration, a wedge-shaped gap at the proximal end of the deployed stent graft in TEVAR that leads to incomplete seal. A baseline TEVAR simulation model was developed along with three simulations in which the value of aortic curvature, aortic arch angle, or aortic tissue properties varied from the baseline model. Analyzing the length and angle of the bird-beak configuration in each case shows that the bird-beak size is sensitive to different values of the aortic geometry highlighting the importance of using realistic parameter values.

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.

Ascending aortic geometry and its relationship to the biomechanical properties of aortic tissue

Objective

The objective of this study was to evaluate the relationship between ascending aortic geometry and biomechanical properties.

Methods

Preoperative computed tomography scans from ascending aortic aneurysm patients were analyzed using a center line technique (n = 68). Aortic length was measured from annulus to innominate artery, and maximal diameter from this segment was recorded. Biaxial tensile testing of excised tissue was performed to derive biomechanical parameters energy loss (efficiency in performing the Windkessel function) and modulus of elasticity (stiffness). Delamination testing (simulation of dissection) was performed to derive delamination strength (strength between tissue layers).

Results

Aortic diameter weakly correlated with energy loss (r ² = 0.10; P < .01), but not with modulus of elasticity (P = .13) or delamination strength (P = .36). Aortic length was not associated with energy loss (P = .87), modulus of elasticity (P = .13) or delamination strength (P = .90). Using current diameter guidelines, aortas >55 mm (n = 33) demonstrated higher energy loss than those <55 mm (n = 35; P = .05), but no difference in modulus of elasticity (P = .25) or delamination strength (P = .89). A length cutoff of 110 mm was proposed as an indication for repair. Aortas >110 mm (n = 37) did not exhibit a difference in energy loss (P = .40), modulus of elasticity (P = .69), or delamination strength (P = .68) compared with aortas <110 mm (n = 31). Aortas above diameter and length thresholds (n = 21) showed no difference in energy loss (P = .35), modulus of elasticity (P = .55), or delamination strength (P = .61) compared with smaller aortas (n = 47).

Conclusions

Aortic geometry poorly reflects the mechanical properties of aortic tissue. Weak association between energy loss and diameter supports intervention at larger diameters. Further research into markers that better capture aortic biomechanics is needed.

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 vs. men.

METHODS

The Vascular Quality Initiative (VQI) was used to identify all patients who underwent CEA between 2010-2019. Demographic, clinical, and procedural characteristics were recorded and differences between women vs. men were assessed using independent t-test and chi-square 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

52,137 women and 79,974 men underwent CEA in VQI 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 minutes, 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 (HR 0.98 [95% 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 US (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 carotid endarterectomy.

Sex Differences in Outcomes Following Ruptured Abdominal Aortic Aneurysm Repair

IMPORTANCE

Sex differences in aortic surgery outcomes are commonly reported. However, data on ruptured abdominal aortic aneurysm (rAAA) repair outcomes in women vs men are limited.

OBJECTIVE

To assess differences in perioperative and long-term mortality following rAAA repair in women vs men.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, retrospective cohort study was conducted using the Vascular Quality Initiative database, which prospectively captures information on patients who undergo vascular surgery across 796 academic and community hospitals in North America. All patients who underwent endovascular or open rAAA repair between January 1, 2003, and December 31, 2019, were included. Outcomes were assessed up to January 1, 2020.

EXPOSURES

Patient sex.

MAIN OUTCOMES AND MEASURES

Demographic, clinical, and procedural characteristics were recorded, and differences between women vs men were assessed using independent t test and χ2 test. The primary outcomes were in-hospital and 8-year mortality. Associations between sex and outcomes were analyzed using univariable and multivariable logistic regression and Cox proportional hazards regression analysis.

RESULTS

A total of 1160 (21.9%) women and 4148 (78.1%) men underwent rAAA repair during the study period. There was a similar proportion of endovascular repairs in women and men (654 [56.4%] vs 2386 [57.5%]). Women were older (mean [SD] age, 75.8 [9.3] vs 71.7 [9.6] years), more likely to have chronic kidney disease (718 [61.9%] vs 2184 [52.7%]), and presented with ruptured aneurysms of smaller diameters (mean [SD] 68 [18.2] vs 78 [30.2] mm). In-hospital mortality was higher in women (34.4% vs 26.6%; odds ratio, 1.44; 95% CI, 1.25-1.66), which persisted after adjusting for demographic, clinical, and procedural characteristics (adjusted odds ratio, 1.36; 95% CI, 1.12-1.66; P = .002). Eight-year survival was lower in women (36.7% vs 49.5%; hazard ratio, 1.25; 95% CI, 1.04-1.50; P = .02), which persisted when stratified by endovascular and open repair. This survival difference existed in both the US and Canada. Variables associated with long-term mortality in women included older age and chronic kidney disease.

CONCLUSIONS AND RELEVANCE

Women who underwent rAAA repair had higher perioperative and 8-year mortality rates following both endovascular and open repair compared with men. Older age and higher rates of chronic kidney disease in women were associated with higher mortality rates. These findings suggest that future studies should assess the reasons for these disparities and whether opportunities exist to improve AAA care for women.

Risk factors, risk stratification and risk-specific surveillance strategies after endovascular aneurysm repair: study protocol for a Delphi study by the International RIsk Stratification in EVAR (IRIS-EVAR) working group

INTRODUCTION

Several risk factors for adverse events after endovascular aneurysm repair (EVAR) have been described, but there is no consensus on their comparative prognostic significance, use in risk stratification and application in determining postoperative surveillance.

METHODS AND ANALYSIS

A scoping review of the literature was conducted to identify risk factors for adverse events after EVAR. Main adverse events were considered post-EVAR abdominal aortic aneurysm rupture and reintervention. Risk factors were grouped into four domains: (1) preoperative anatomy, (2) aortic device, (3) procedure performance and (4) postoperative surveillance. The Delphi methodology will be used to steer a group of experts in the field towards consensus organised into three tiers. In tier 1, participants will be asked to independently rate risk factors for adverse events after EVAR. In tier 2, the panel will be asked to independently rate a range of combinations of risk factors across the four domains derived from tier 1. A risk-stratification tool will then be built, which will include algorithms that map responses to signalling questions onto a proposed risk judgement for each domain. Domain-level judgements will in turn provide the basis for an overall risk judgement for the individual patient. In tier 3, risk factor-informed surveillance strategies will be developed. Each tier will typically include three rounds and rating will be conducted using a 4-point Likert scale, with an option for free-text responses.

ETHICS AND DISSEMINATION

Research Ethics Committee and Health Research Authority approval has been waived, since this is a professional staff study and no duty of care lies with the National Health Service to any of the participants. The results will be presented at regional, national and international meetings and will be submitted for publication in peer-reviewed journals. The risk stratification tool and surveillance algorithms will be made publicly available for clinical use and validation.

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

INTRODUCTION

Artificial intelligence (AI) and machine learning (ML) have seen increasingly intimate integration with medicine and healthcare in the last two 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 the 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 meta-data, the clinical area of study within vascular surgery, type of AI/ML method used, data set, and the application of AI/ML. Publishing journals were classified as having either a clinical scope or technical scope. Author academic background was classified as clinical, non-clinical (e.g., engineering) or both, depending on author affiliation.

RESULTS

The initial search identified 7434 studies, of which 249 were included for final analysis. The rate of publications is exponentially increasing, with 158 (63%) studies being published in the last 5 years. 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%). Data sets to which these AI/ML methods were applied frequently involved ultrasound images (87, 35%), CT images (42, 17%), clinical data (34, 14%) or multiple data sets (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 1576 publishing authors, 46% had exclusively a clinical background, 48% a non-clinical background, and 5% had both a clinical and non-clinical background.

CONCLUSION

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 underrepresented. Neural networks and support vector machines composed most AI methods in the literature. As AI/ML continues to see more expanded applications in the field, it is important that vascular surgeons appreciate its potential and limitations. Additionally, 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.

A multicenter retrospective cohort study of blunt traumatic injury to the common or internal carotid arteries

OBJECTIVE

Current EAST guidelines recommend against routine carotid intervention for patients with blunt carotid artery injury (BCI), but offer limited information on its role for BCI patients presenting with neurological deficit. Our goal was to describe the contemporary management and outcomes of patients presenting with BCI and neurological deficit unrelated to head injury.

METHODS

We identified all adults who sustained a BCI between 2010 and 2017 in the American College of Surgeons Trauma Quality Improvement Program. We extracted patient demographics, injury characteristics (carotid and non-carotid), as well as the frequency, timing and approach of carotid intervention. Presence of neurological deficit unrelated to head injury at presentation was determined using Abbreviated Injury Scale codes. The main outcomes were in-hospital mortality and home discharge. Patients with and without neurological deficit at presentation were compared through multivariable logistic regression modeling. Among those with neurological deficit at presentation, the associations between carotid intervention (open or endovascular) and the outcomes were also assessed through multivariable logistic regression.

RESULTS

We identified 5,788 patients with BCI of whom 383 (7%) presented with neurological deficit unrelated to head injury. Among the 296 patients (5%) who underwent carotid intervention, 36 (12%) had presented with neurological deficit unrelated to head injury. Interventions were most often endovascular (68% [200/296]) and within a median time of 32 h (IQR 5-203). In-hospital mortality was 16% (918/5,788), and in-hospital stroke prevalence was 6% (336/5,788). When comparing patients with and without neurological deficit at presentation, those with deficits were more frequently managed with an intervention. After adjustment, the likelihood of mortality was higher (OR [95% CI] = 2.16 [1.63-2.85]) and the likelihood of home discharge lower (OR [95% CI] = 0.29 [0.21-0.40]) among patients presenting with neurological deficit. Among those with neurological deficit, carotid intervention was positively associated with home discharge (OR [95% CI] = 2.96 [1.21-7.23]), but not with in-hospital mortality (OR [95% CI] = 0.87 [0.36-2.10]). Results were similar in the subgroup of patients with isolated BCI (2,971/5,788).

CONCLUSIONS

Intervention in BCI patients presenting with neurological deficit may contribute to a greater likelihood of home discharge but not reduced in-hospital mortality.

ANALYSIS OF SPIN IN VASCULAR SURGERY RANDOMIZED CONTROLLED TRIALS WITH NONSIGNIFICANT OUTCOMES

OBJECTIVES

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 (CEA) to carotid artery stenting (CAS) for carotid stenosis (CS), and endovascular repair (EVAR) to 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 three RCTs with nonsignificant primary outcomes comparing OR to EVAR or CEA to CAS 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 non-commercial) and (2) the publishing journal's impact factor.

RESULTS

Thirty-one of 355 articles captured were included for analysis. Spin was identified in nine abstracts (9/18) and 13 main texts (13/18) of AAA articles and seven abstracts (7/13) and ten main texts (10/13) of CS articles. For both AAA and CS articles, spin was most commonly found in the manuscript discussion section, with the most commonly employed 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 (βOR = 0.96, 95% CI: 0.94 - 0.98, p < 0.01) while no significant association could be found with funding source (βOR = 1.33, 95% CI: 0.30-5.92, p = 0.71).

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.

Aspirin nonsensitivity in patients with vascular disease: Assessment by light transmission aggregometry (aspirin nonsensitivity in vascular patients)

BACKGROUND

Aspirin is a key antiplatelet therapy for the prevention of thrombotic events in patients with cardiovascular disease. Studies suggest that ≈20% of patients with cardiac disease suffer from aspirin nonsensitivity, a phenomenon characterized by the inability of 81 mg aspirin to inhibit platelet aggregation and/or prevent adverse cardiovascular events.

OBJECTIVES

To investigate aspirin nonsensitivity in patients with vascular disease and assess the consequences of aspirin nonsensitivity.

METHODS

One hundred fifty patients presenting to St. Michael's Hospital's outpatient clinics with evidence of vascular disease (peripheral arterial disease or carotid artery stenosis) and a previous prescription of 81 mg of aspirin were recruited in this study. Light transmission aggregometry with arachidonic acid induction was used to determine sensitivity to aspirin. Patients with a maximum aggregation ≥20% in response to arachidonic acid were considered aspirin nonsensitive, as per previous studies.

RESULTS

Of the 150 patients recruited, 36 patients (24%) were nonsensitive to 81 mg of aspirin. Of these 36 nonsensitive patients, 30 patients provided a urine sample for urine salicyluric acid analysis (a major metabolite of aspirin). Urine analysis demonstrated that 14 patients were compliant and 16 were noncompliant with their aspirin therapy. Major adverse cardiovascular events and major adverse limb events were significantly higher in the nonsensitive patients compared to sensitive patients (hazard ratio, 3.68; P < 0.001).

CONCLUSION

These data highlight the high prevalence of aspirin nonsensitivity and noncompliance in patients with vascular disease and emphasizes the urgent need for improved medical management options for this patient population.

Fatty acid binding protein 3 is associated with peripheral arterial disease

Background

Peripheral arterial disease (PAD) affects more than 150 million people worldwide and is associated with high rates of lower extremity amputation, myocardial infarction, stroke and death. Fatty acid binding protein 3 (FABP3) is released into circulation in patients with skeletal muscle injury. In this pilot study, we investigated a possible association between PAD and blood levels of FABP3.

Methods

Blood samples were collected from patients with clinical symptoms and diagnostic findings indicative of PAD (PAD group; ankle-brachial index [ABI] <0.9; n = 75) and in those without clinical or diagnostic features of PAD (non-PAD group; ABI >0.9; n = 75) presenting to vascular surgery ambulatory clinics at St. Michael's Hospital. Plasma samples were analyzed by protein multiplex to quantify FABP3 levels.

Results

PAD patients were found to have higher blood levels of FABP3 compared to patients without PAD (mean 3.90 ± 1.69 vs 2.03 ± 0.78; P < .001). A subgroup analysis demonstrated that the FABP3 levels were increased by almost two-fold in patients with PAD, independent of coronary artery disease (P < .001) or diabetes mellitus status (P < .001). Moreover, a significant negative correlation between FABP3 and the ABI was observed in PAD and patients without PAD matched groups (r = –0.51; P = .001). Last, immunohistochemistry demonstrated elevated expressions of FABP3 within skeletal muscle obtained from patients with the most severe form of PAD, chronic limb-threatening ischemia, when compared with patients without PAD.

Conclusions

Patients with PAD have elevated plasma levels of FABP3. An increasing severity of PAD is associated with higher FABP3 levels.

There is a pressing need for a simple, readily accessible, blood-based biomarker for PAD. In this study, we found elevated levels of FABP3 in patients with PAD. This increase in FABP3 was irrespective of history of coronary artery disease or diabetes. Furthermore, our data suggest that an increasing severity of PAD is associated with higher FABP3 levels. Subsequently, FABP3 may be a potential diagnostic biomarker for PAD. However, further studies are needed to confirm the capability of FABP3 to serve as a valid and reliable biomarker for PAD.

Risk factors Associated with Long Term Mortality and Complications Following Thoracoabdominal Aortic Aneurysm Repair

OBJECTIVE

To determine the risk factors associated with late mortality or complications (Thoracoabdominal aortic Aneurysm Life-altering Events (TALE): composite of mortality, permanent paraplegia, permanent dialysis, and stroke) in patients undergoing endovascular or open thoracoabdominal aortic aneurysm (TAAA) repair.

METHODS

Population-based study of patients undergoing TAAA repair in Ontario, Canada, between 2006 - 2017. The association of baseline risk factors with mortality post repair and complications was examined with Cox hazards models with hospital-specific random effects. The survival of patients undergoing TAAA repair was compared to matched controls who were free from TAAA, matching on age, sex, area of residence, and average annual household income. Type of repair (endovascular vs open) was included in all models.

RESULTS

We identified 664 adults (mean age 69.3 ± 10.6, 71% men) undergoing 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 undergoing 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 ((HR 1.97, 95% CI 1.67-2.32, p<.01). In patients undergoing TAAA, 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, risk factors associated with mortality during follow-up included older age (hazard ratio (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 in those with previous coronary revascularization (HR 0.63, 95%CI 0.41-0.96) and 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 higher rate of TALE. The type of repair (endovascular or open) was not associated with mortality or TALE.

CONCLUSIONS

TAAA repair is associated with reduced long-term survival compared to the general population regardless of mode of treatment. Urgent/emergent repair was the most profound risk factor late adverse events. Type of repair (endovascular or open) was not a predictor for long-term death or complications. Previous coronary revascularization and having the procedure performed at a high-volume institution were associated with improved late outcomes in patients undergoing TAAA repair.

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 US 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). US 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 US 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 US 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.

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.

Patient engagement study to identify and improve surgical experience

BACKGROUND

Patient engagement is the establishment of active partnerships between patients, families, and health professionals to improve healthcare delivery. The objective of this project was to conduct a series of patient engagement workshops to identify areas to improve the surgical experience and develop strategies to address areas identified as high priority.

METHODS

Faculty surgeons and patients were invited to participate in three in-person meetings. Evaluation included identifying and developing strategies for three priority areas to improve the surgical experience and level of engagement achieved at each meeting.

RESULTS

Sixteen faculty surgeons and 32 patients participated. Some 63 themes to improve the surgical experience were identified; the three highest-priority themes were physician communication, discharge process, and expectations at home after discharge. Individual improvement strategies for these three prioritized themes (12, 36 and 6 respectively) were used to develop a formal strategic plan, and included a physician communication survey, discharge process worksheet and video, and guideline regarding what to expect at home after discharge. Overall, the level of engagement achieved was considered high by over 85 per cent of the participants.

CONCLUSION

A high level of patient engagement was achieved. Priorities were identified with patients and surgeons to improve surgical experience, and strategies were developed to address these areas.

Ascending Aortic Length and Its Association With Type A Aortic Dissection

Background

The aim of this study was to determine the role of ascending aortic length and diameter in type A aortic dissection.

Methods and Results

Computed tomography scans from patients with acute type A dissections (n=51), patients with proximal thoracic aortic aneurysms (n=121), and controls with normal aortas (n=200) were analyzed from aortic annulus to the innominate artery using multiplanar reconstruction. In the control group, ascending aortic length correlated with diameter (r²=0.35, P<0.001), age (r²=0.17, P<0.001), and sex (P<0.001). As a result of immediate changes in aortic morphology at the time of acute dissection, predissection lengths and diameters were estimated based on models from published literature. Ascending aortic length was longer in patients immediately following acute dissection (median, 109.7 mm; interquartile range [IQR], 101.0–115.1 mm), patients in the estimated predissection group (median, 104.2 mm; IQR, 96.0–109.3 mm), and patients in the aneurysm group (median, 107.0 mm; IQR, 99.6–118.7 mm) in comparison to controls (median, 83.2 mm; IQR, 74.5–90.7 mm) (P<0.001 all comparisons). The diameter of the ascending aorta was largest in the aneurysm group (median, 52.0 mm; IQR, 45.9–58.0 mm), followed by the dissection group (median, 50.3 mm; IQR, 46.6–57.5 mm), and not significantly different between controls and the estimated predissection group (median, 33.4 mm [IQR, 30.7–36.7 mm] versus 35.2 mm [IQR, 32.6–40.3 mm], P=0.09). After adjustment for diameter, age, and sex, the estimated predissection aortic lengths were 16 mm longer than those in the controls and 12 mm longer than in patients with nondissected thoracic aneurysms.

Conclusions

The length of the ascending aorta, after adjustment for age, sex, and aortic diameter, may be useful in discriminating patients with type A dissection from normal controls and patients with nondissected thoracic aneurysms.

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.

The Many Care Models to Treat Thoracic Aortic Disease in Canada: A Nationwide Survey of Cardiac Surgeons, Cardiologists, Interventional Radiologists, and Vascular Surgeons

Background

Several specialties treat thoracic aortic disease, resulting in multiple patient care pathways. This study aimed to characterize these varied care models to guide health policy.

Methods

A 57-question e-survey was sent to staff cardiac surgeons, cardiologists, interventional radiologists, and vascular surgeons at 7 Canadian medical societies.

Results

For 914 physicians, the response rate was 76% (86 of 113) for cardiac surgeons, 40% (58 of 146) for vascular surgeons, 24% (34 of 140) for radiologists, and 14% (70 of 515) for cardiologists. Several services admitted type B dissections (vascular 37%, cardiology 31%, cardiac 18%, other 7%), and care was heterogeneous. Ownership of disease management was overestimated relative to the perspective of the other specialties. Type A dissection admissions and treatment were more uniform, but emergent call coverage varied. A 24/7 aortic specialist on-call schedule was present only 4% of the time. “Aortic” case rounds promoted attendance by a broader aortic specialty contingency relative to rounds that were specialty specific. Although 89% of respondents felt an aortic team was best for patient care, only 54% worked at an institution with an aortic team present, and only 28% utilized an aortic clinic. Questions designed to define an aortic team derived 63 different combinations.

Conclusions

Thoracic aortic disease follows a network of undefined and variable care pathways, despite its high-risk population in need of complex treatment considerations. Multidisciplinary aortic teams and clinics exist in low volume, and the “aortic team” remains an obscure construct. A multispecialty initiative to define the aortic team and outline standardized navigation pathways within the health systems hospitals is advocated.

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.

Regional health care services and rates of lower extremity amputation related to diabetes and peripheral artery disease: an ecological study

BACKGROUND

The care necessary to prevent amputation from diabetes and peripheral artery disease (PAD) remains disjointed in many jurisdictions. To help inform integrated regional care, this study explores the correlation between regional health care services and rates of lower extremity amputation.

METHODS

This ecological study included 14 administrative health regions in Ontario, Canada. All diabetes- or PAD-related major (above ankle) amputations (Apr. 1, 2007, to Mar. 31, 2017) were identified among residents 40 years of age and older. For each region, age-and sex-adjusted amputation rates were calculated as well as per capita counts of key health providers (podiatrists and chiropodists, as well as surgeons) and health care utilization among study patients in the year before the first major amputation (physician visits, publicly funded podiatry visits, emergency department visits, hospital admissions, home care nursing, minor amputation, limb revascularization).

RESULTS

A total of 11 658 patients with major amputation were identified (of whom 79.2% had diabetes and 96.5% had PAD). There was wide regional variation in amputation rates: 2.53 to 11.77 per 100 000 person-quarters. At a regional level, the proportion of study patients who received revascularization showed the strongest negative correlation with amputation rates. The regional proportion of study patients who saw a vascular surgeon showed the strongest negative correlation with amputation rates, relative to other health provider visits. Other measures of health care utilization among patients correlated poorly with regional amputation rates, as did the regional provider counts. The results were similar when we restricted the analysis to diabetes-related amputations.

INTERPRETATION

Amputation rates related to diabetes and PAD vary widely across Ontario. Access to vascular assessment and revascularization must be integrated into regional amputation prevention efforts.

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.

Fatty Acid Binding Protein 4-A Circulating Protein Associated with Peripheral Arterial Disease in Diabetic Patients

Diabetic patients with peripheral arterial disease (PAD) often suffer from poor clinical outcomes such as limb-loss. Fatty acid binding protein 4 (FABP4) is mainly expressed by adipocytes and is known to play a significant role in the development of atherosclerosis. In this study, we sought to investigate whether FABP4 is associated with PAD in patients with type 2 diabetes mellitus (DM). FABP4 plasma levels were studied in 119 diabetic patients with PAD (DM-PAD) and 49 diabetic patients without PAD (DM-noPAD) presenting to St. Michael’s Hospital between October 2017 and September 2018. Levels of FABP4 in DM-PAD patients (23.34 ± 15.27 ng/mL) were found to be over two-fold higher than the levels in DM-noPAD patients (10.3 ± 7.59 ng/mL). Regression analysis demonstrated a significant association between FABP4 levels and DM-PAD after adjusting for age, sex, prior history of coronary arterial disease and white blood cells count (OR, 2.77; 95% CI, 1.81–4.31; p-value = 0.001). Relative to DM-noPAD controls, plasma FABP4 levels in DM-PAD patients were noted to be inversely correlated with the ankle brachial index (ABI; r= −0.374, p-value < 0.001). The diagnostic ability of FABP4 was investigated using receiver operator curves (ROC) and area under the curve (AUC) analysis. FABP4 had an AUC of 0.79, which improved to 0.86 after adjusting for age, sex and prior history of coronary arterial disease. This raises a possibility of utilizing FABP4 as a biomarker for diagnosing PAD in diabetic patients.

Biomechanics of Aortic Dissection: A Comparison of Aortas Associated With Bicuspid and Tricuspid Aortic Valves

Background

Current methods for aortic dissection risk assessment are inadequate for patients with ascending aortic aneurysms associated with either bicuspid aortic valves (BAVs) or tricuspid aortic valves (TAVs). Biomechanical testing of aortic tissue may provide novel insights and biomarkers.

Methods and Results

From March 2017 to August 2019, aneurysmal ascending aortas (BAV=23, TAV=23) were collected from elective aortic surgery, normal aortas from transplant donors (n=9), and dissected aortas from surgery for aortic dissection (n=7). These aortas underwent delamination testing in simulation of aortic dissection. Biaxial tensile testing was performed to determine modulus of elasticity (aortic stiffness), and energy loss (a measure of efficiency in performing the Windkessel function). Delamination strength (S_d) was lowest in dissected aortas (18±6 mN/mm) and highest in normal aortas (58±16 mN/mm), and aneurysms fell in between, with greater S_d in the BAV group (37±10 mN/mm) than the TAV group (27±10 mN/mm) (P<0.001). Bicuspid aortopathy was associated with greater stiffness (P<0.001), while aneurysms with TAV demonstrated greater energy loss (P<0.001). S_d decreased by 7.8±1.2 mmol/L per mm per decade of life (r²=0.45, P<0.001), and it was significantly lower for patients with hypertension (P=0.001). S_d decreased by 6.1±2.1 mmol/L per mm with each centimeter increase in aortic diameter (r²=0.15, P=0.007). Increased energy loss was associated with decreased S_d (r²=0.41), whereas there was no relationship between S_d and aortic stiffness.

Conclusions

Aneurysms with BAV had higher S_d than those with TAV, suggesting that BAV was protective. Energy loss was lower in aneurysms with BAV, and inversely associated with S_d, representing a potential novel biomarker.

Population-based secular trends in lower-extremity amputation for diabetes and peripheral artery disease

BACKGROUND

The evolving clinical burden of limb loss secondary to diabetes and peripheral artery disease remains poorly characterized. We sought to examine secular trends in the rate of lower-extremity amputations related to diabetes, peripheral artery disease or both.

METHODS

We included all individuals aged 40 years and older who underwent lower-extremity amputations related to diabetes or peripheral artery disease in Ontario, Canada (2005-2016). We identified patients and amputations through deterministic linkage of administrative health databases. Quarterly rates (per 100 000 individuals aged ≥ 40 yr) of any (major or minor) amputation and of major amputations alone were calculated. We used time-series analyses with exponential smoothing models to characterize secular trends and forecast 2 years forward in time.

RESULTS

A total of 20 062 patients underwent any lower-extremity amputation, of which 12 786 (63.7%) underwent a major (above ankle) amputation. Diabetes was present in 81.8%, peripheral artery disease in 93.8%, and both diabetes and peripheral artery disease in 75.6%. The rate of any amputation initially declined from 9.88 to 8.62 per 100 000 between Q2 of 2005 and Q4 of 2010, but increased again by Q1 of 2016 to 10.0 per 100 000 (p = 0.003). We observed a significant increase in the rate of any amputation among patients with diabetes, peripheral artery disease, and both diabetes and peripheral artery disease. Major amputations did not significantly change among patients with diabetes, peripheral artery disease or both.

INTERPRETATION

Lower-extremity amputations related to diabetes, peripheral artery disease or both have increased over the last decade. These data support renewed efforts to prevent and decrease the burden of limb loss.

Female sex is associated with comparable 5-year outcomes after contemporary endovascular aneurysm repair despite more challenging anatomy

BACKGROUND

Women with abdominal aortic aneurysms less often meet anatomic criteria for endovascular repair and experience worse perioperative and long-term survival.

METHODS

We compared long-term survival, aneurysm-related mortality, and rates of endoleaks and reinterventions between male and female patients in the Endurant Stent Graft Natural Selection Global Postmarket Registry (ENGAGE) using 2:1 propensity score matching.

RESULTS

There were 1130 male patients and 133 female patients, yielding 399 patients after matching (266 male patients, 133 female patients). Female patients were older, with smaller aneurysms, smaller iliac arteries, and shorter, more angulated necks, and they were more often treated outside the device instructions for use (all P < .001). Through 5 years, female patients experienced overall mortality comparable to that of well-matched male patients (34% vs 38%, respectively; hazard ratio, 0.89 [0.61-1.29]; P = .54) and lower aneurysm-related mortality (0% vs 3%; P = .047). Female patients experienced higher rates of any postoperative type IA endoleak through 5 years (10% vs 1%; P < .001) but comparable rates of secondary endovascular procedures (14% vs 16%; P = .40). Female sex was independently associated with significantly higher risk of long-term type IA endoleaks (hazard ratio, 4.8 [1.2-20.8]; P = .04), even after accounting for anatomic factors. No female patient experienced aneurysm rupture during follow-up, and only one female patient underwent conversion to open repair.

CONCLUSIONS

Despite more challenging anatomy, female patients in the ENGAGE registry had long-term outcomes comparable to those of male patients. However, female patients experienced higher rates of type IA endoleaks. Although standard endovascular aneurysm repair remains a viable solution for most women, whether high-risk patients may be better served with open surgery, custom-made devices, EndoAnchors (Aptus Endosystems, Sunnyvale, Calif), or chimneys is worthy of further study.

Short-term outcomes of combined neuraxial and general anaesthesia versus general anaesthesia alone for elective open abdominal aortic aneurysm repair: retrospective population-based cohort study†

BACKGROUND

Use of neuraxial anaesthesia for open abdominal aortic aneurysm repair is postulated to reduce mortality and morbidity. This study aimed to determine the 90-day outcomes after elective open abdominal aortic aneurysm repair in patients receiving combined general and neuraxial anaesthesia vs general anaesthesia alone.

METHODS

A retrospective population-based cohort study was conducted from 2003 to 2016. All patients ≥40 yr old undergoing open abdominal aortic aneurysm repair were included. The propensity score was used to construct inverse probability of treatment weighted regression models to assess differences in 90-day outcomes.

RESULTS

A total of 10 447 elective open abdominal aortic aneurysm repairs were identified; 9003 (86%) patients received combined general and neuraxial anaesthesia and 1444 (14%) received general anaesthesia alone. Combined anaesthesia was associated with significantly lower hazards for all-cause mortality (hazard ratio [HR]=0.47; 95% confidence interval [CI], 0.37-0.61) and major adverse cardiovascular events (HR=0.72; 95% CI, 0.60-0.86). Combined patients were at lower odds for acute kidney injury (odds ratio [OR]=0.66; 95% CI, 0.49-0.89), respiratory failure (OR=0.41; 95% CI, 0.36-0.47), and limb complications (OR=0.30; 95% CI, 0.25-0.37), with higher odds of being discharged home (OR=1.32; 95% CI, 1.15-1.51). Combined anaesthesia was also associated with significant mechanical ventilation and ICU and hospital length of stay benefits.

CONCLUSIONS

Combined general and neuraxial anaesthesia in elective open abdominal aortic aneurysm repair is associated with reduced 90-day mortality and morbidity. Neuraxial anaesthesia should be considered as a routine adjunct to general anaesthesia for elective open abdominal aortic aneurysm repair.

Prevention and management of spinal cord ischemia following aortic surgery: A survey of contemporary practice

OBJECTIVE

Spinal cord ischemia (SCI) is a devastating complication of thoracoabdominal aortic aneurysm repair. We aim to characterize current practices pertaining to SCI prevention and treatment across Canada.

METHODS

Two questionnaires were developed by the Canadian Thoracic Aortic Collaborative and the Canadian Cardiovascular Critical Care Society targeting aortic surgeons and intensivists. A list of experts in the management of patients at risk of SCI was developed, with representation from each of the Canadian centers that perform complex aortic surgery.

RESULTS

The response rate was 91% for both intensivists (21/23), and from cardiac and vascular surgeons (39/43). Most surgeons agreed that staging is important during endovascular repair of extent II thoracoabdominal aortic aneurysm (60%) but not for open repair (34%). All of the surgeons felt prophylactic lumbar drains were effective in reducing SCI, whereas only 66.7% of intensivists felt that lumbar drains were effective (P < .001). There was consensus among surgeons over when to employ lumbar drains. A majority of surgeons preferred to keep the hemoglobin over 100 g/L if the patient demonstrated loss of lower-extremity function, whereas most intensivists felt a target of 80 g/L was adequate (P < .001). Management of perioperative antihypertensives, use of intraoperative adjuncts, and management of venous thromboembolism prophylaxis in the presence of a lumbar drain, were highly variable.

CONCLUSIONS

We observed some consensus but considerable variability in the approach to SCI prevention and management across Canada. Future studies focused on the areas of variability may lead to more consistent and improved care for this high-risk population.

Mediastinal bronchial artery aneurysm with short inflow segment successfully treated with a patent ductus arteriosus occluder device

Bronchial artery aneurysm (BAA) is a rare vascular abnormality that may result in life-threatening bleeding if it is left untreated. We present the case of a 35-year-old man with a mediastinal BAA characterized by a short inflow artery segment and tortuous single outflow vessel. The patient's BAA was treated with a novel approach involving placement of a patent ductus arteriosus closure device in the short inflow segment as well as coil embolization of the outflow vessel, successfully excluding the BAA. Two-week follow-up revealed no flow in the embolized artery on computed tomography angiography. This case demonstrates the first successful use of a patent ductus arteriosus occluder device in the treatment of a mediastinal BAA with short inflow segment.

Endovascular Repair of Thoracic Aortic Disease: Early and Midterm Experience

Thoracic aorta disease remains a challenging problem, and despite improvements, open repair techniques are still associated with significant morbidity and mortality. This is a retrospective review of 53 consecutive patients with thoracic aortic pathology who were treated with endovascular repair between September 1998 and December 2004 at a tertiary-care hospital. Endovascular stent graft placement was performed on 23 elective and 30 emergent patients (34 male patients, mean age 66 years, 21 to 85 years). Completion angiography revealed no endoleak in 47 (89%) patients, a type I endoleak in 4 patients, and a type II endoleak in 2 patients. Operative 30-day mortality for elective aneurysms (n = 22), emergent aneurysms (n = 10), dissection (n = 3), penetrating aortic ulcers (n = 7), and trauma (n = 11) was 0%, 40%, 0%, 29%, and 9%, respectively. In total, 46 (87%) patients survived 30 days, and 36 (78.3%) of the survivors were discharged home free of complications. Two patients (4%) experienced paraplegia. Median follow-up was 22 months (1 to 72 months). Intermediate-term results revealed 41 (89%) patients free of endoleak, stent migration, or aneurysmal expansion. Two (4%) patients required reintervention with an additional stent graft. There were 2 (4%) patients with late aortic-related deaths and four (9%) patients with non—aorticrelated late deaths. Endovascular stent graft placement for thoracic aorta disease can be performed successfully and safely with good perioperative and intermediate-term outcomes. Stent graft complication and reintervention rates are low, whereas intermediate survival rates are good. Long-term efficacy still needs to be evaluated.