Importance of Aortic Morphology in Planning Aortic Interventions

Influence of Anesthetic Techniques on Perioperative Outcomes after Endovascular Aneurysm Repair

BACKGROUND

The purpose of the study was to explore the influence of anesthetic techniques on perioperative outcomes after endovascular aneurysm repair (EVAR) for infrarenal abdominal aortic aneurysm (AAA) in a Chinese population.

METHODS

A retrospective review was performed in patients after elective EVAR for infrarenal AAA at our single center. Patients were classified into general anesthesia (GA), regional anesthesia (RA), and local anesthesia (LA) groups. The primary outcomes (30-day mortality and morbidity) and secondary outcomes [procedure time, mean arterial pressure (MAP), and length of hospital stay (LOS)] were collected and analyzed.

RESULTS

From January 2006 to December 2015, 486 consecutive patients underwent elective EVAR at our center. GA was used in 155 patients (31.9%), RA in 56 (11.5%), and LA in 275 (56.6%). The GA patients had fewer respiratory comorbidities, shorter and more angulated proximal necks, and more concomitant iliac aneurysms. LA during EVAR was significantly associated with a shorter procedure time (GA, P < 0.001; RA, P < 0.001) and shorter LOS (GA, P = 0.002; RA, P = 0.001), but a higher MAP (GA, P < 0.001; RA, P < 0.001) compared with GA and RA. LA was associated with a significantly lower risk of cardiac (odds ratio (OR) 4.27, 95% confidence interval (CI) 1.21-15.04), pulmonary (OR 5.37, 95% CI 1.58-18.23), and systemic complications (OR 4.15, 95% CI 1.85-9.33) compared with GA. RA was also associated with a decreased risk of systemic complications (OR 4.74, 95% CI 1.19-18.92) compared with GA. There was no difference in the 30-day mortality, neurologic complications, renal complications, and intraoperative extra procedures among the 3 groups.

CONCLUSIONS

Anesthetic techniques for EVAR have no influence on the 30-day mortality. LA for EVAR appears to be beneficial concerning the procedure time, LOS, and 30-day systemic complications for patients after elective EVAR for infrarenal AAA in the Chinese population.

Long-term failure after endovascular aneurysm sealing in a real-life, single-center experience with the Nellix endograft

BACKGROUND

Endovascular aneurysm sealing (EVAS) is an innovative alternative to conventional endovascular aneurysm repair (EVAR). EVAS relies on sac anchoring without proximal fixation to achieve sealing and should have allowed for the treatment of a broader range of anatomic features compared with standard EVAR. Despite the encouraging early reports, the mid- and long-term follow-up data have shown increased rates of failure. To address the issue, the manufacturer introduced revised instructions for use (IFU) in 2016. The present study reports the outcomes of this system after a median follow-up of 45 months.

METHODS

Data for all patients electively treated with EVAS at our institution were retrospectively collected. The patients were retrospectively reclassified according to the 2016 revised IFU of the device. All patients in the present series had undergone EVAS for the treatment of infrarenal abdominal aortic aneurysms (AAAs). The primary end point was therapeutic failure: graft migration >5 mm, sac expansion >5 mm, type IA endoleak (Is2 and Is3 using the Van den Ham classification), type Ib endoleak, and secondary rupture. The overall mortality, aortic-related mortality, and reintervention rates were also analyzed.

RESULTS

A total of 101 patients had undergone elective treatment by EVAS from 2013 to 2018 for infrarenal AAAs. The median follow-up was 3.75 years. Therapeutic failure was observed in 31 of the 101 patients (30.7%), with no significant difference between the in-IFU and off-IFU 2016 subgroups. Failure occurred at a median interval of 34 months from the index procedure. Of the 101 patients, 6.9% had presented with secondary rupture. Freedom from aneurysm-related mortality was 96.9% at 1 and 2 years and 89.9% at 5 years. Freedom from reintervention decreased over time: 94.7% at 1 year, 77% at 4 years, and 52.1% at 6 years. Of the 101 patients, 14 (13.9%) had undergone emergent or elective graft explantation.

CONCLUSIONS

EVAS performed worse than conventional endografts for several critical end points, regardless of any preoperative anatomic parameters. The incidence of therapeutic failures tended to increase over time, especially 4 years after the index procedure.

Midterm results of endovascular aneurysm sealing to treat abdominal aortic aneurysm

BACKGROUND

Endovascular aneurysm sealing (EVAS) represents a novel approach to the treatment of abdominal aortic aneurysms. It uses polymer technology to achieve an anatomic seal within the sac of the aneurysm. This cohort study reports the early clinical outcomes, technical refinements, and learning curve during the initial EVAS experience at a single institution.

METHODS

Results from 150 consecutive EVAS cases for intact, infrarenal abdominal aortic aneurysms are reported here. These cases were undertaken between March 2013 and July 2015. Preoperative, perioperative, and postoperative data were collected for each patient prospectively.

RESULTS

The median age of the cohort was 76.6 years (interquartile range, 70.2-80.9 years), and 87.3% were male. Median aneurysm diameter was 62.0 mm (IQR, 58.0-69.0 mm). Adverse neck morphology was seen in 69 (46.0%) patients, including aneurysm neck length <10 mm (17.3%), neck diameter >32 mm or <18 mm (8.7%), and neck angulation >60 degrees (15.3%). Median follow-up was 687 days (IQR, 463-897 days); 37 patients (24.7%) underwent reintervention. The rates of unresolved endoleak are 1.3% type IA, 0.7% type IB, and 2.7% type I. There were no type III endoleaks. There have been seven secondary ruptures in this cohort; all but one of these patients survived after reintervention. Only one rupture occurred in an aneurysm that had been treated within the manufacturer's instructions for use (IFU).

CONCLUSIONS

The rate of unresolved endoleaks is satisfactorily low. The incidence of secondary rupture is of concern; however, when the IFU are adhered to, the rate is very low. The results of this study suggest that working within the IFU yields better clinical results.

Using multiple classifiers for predicting the risk of endovascular aortic aneurysm repair re-intervention through hybrid feature selection

Feature selection is essential in medical area; however, its process becomes complicated with the presence of censoring which is the unique character of survival analysis. Most survival feature selection methods are based on Cox's proportional hazard model, though machine learning classifiers are preferred. They are less employed in survival analysis due to censoring which prevents them from directly being used to survival data. Among the few work that employed machine learning classifiers, partial logistic artificial neural network with auto-relevance determination is a well-known method that deals with censoring and perform feature selection for survival data. However, it depends on data replication to handle censoring which leads to unbalanced and biased prediction results especially in highly censored data. Other methods cannot deal with high censoring. Therefore, in this article, a new hybrid feature selection method is proposed which presents a solution to high level censoring. It combines support vector machine, neural network, and K-nearest neighbor classifiers using simple majority voting and a new weighted majority voting method based on survival metric to construct a multiple classifier system. The new hybrid feature selection process uses multiple classifier system as a wrapper method and merges it with iterated feature ranking filter method to further reduce features. Two endovascular aortic repair datasets containing 91% censored patients collected from two centers were used to construct a multicenter study to evaluate the performance of the proposed approach. The results showed the proposed technique outperformed individual classifiers and variable selection methods based on Cox's model such as Akaike and Bayesian information criterions and least absolute shrinkage and selector operator in p values of the log-rank test, sensitivity, and concordance index. This indicates that the proposed classifier is more powerful in correctly predicting the risk of re-intervention enabling doctor in selecting patients' future follow-up plan.

Feature selection through validation and un-censoring of endovascular repair survival data for predicting the risk of re-intervention

Background

Feature selection (FS) process is essential in the medical area as it reduces the effort and time needed for physicians to measure unnecessary features. Choosing useful variables is a difficult task with the presence of censoring which is the unique characteristic in survival analysis. Most survival FS methods depend on Cox’s proportional hazard model; however, machine learning techniques (MLT) are preferred but not commonly used due to censoring. Techniques that have been proposed to adopt MLT to perform FS with survival data cannot be used with the high level of censoring. The researcher’s previous publications proposed a technique to deal with the high level of censoring. It also used existing FS techniques to reduce dataset dimension. However, in this paper a new FS technique was proposed and combined with feature transformation and the proposed uncensoring approaches to select a reduced set of features and produce a stable predictive model.

Methods

In this paper, a FS technique based on artificial neural network (ANN) MLT is proposed to deal with highly censored Endovascular Aortic Repair (EVAR). Survival data EVAR datasets were collected during 2004 to 2010 from two vascular centers in order to produce a final stable model. They contain almost 91% of censored patients. The proposed approach used a wrapper FS method with ANN to select a reduced subset of features that predict the risk of EVAR re-intervention after 5 years to patients from two different centers located in the United Kingdom, to allow it to be potentially applied to cross-centers predictions. The proposed model is compared with the two popular FS techniques; Akaike and Bayesian information criteria (AIC, BIC) that are used with Cox’s model.

Results

The final model outperforms other methods in distinguishing the high and low risk groups; as they both have concordance index and estimated AUC better than the Cox’s model based on AIC, BIC, Lasso, and SCAD approaches. These models have p-values lower than 0.05, meaning that patients with different risk groups can be separated significantly and those who would need re-intervention can be correctly predicted.

Conclusion

The proposed approach will save time and effort made by physicians to collect unnecessary variables. The final reduced model was able to predict the long-term risk of aortic complications after EVAR. This predictive model can help clinicians decide patients’ future observation plan.

Electronic supplementary material

The online version of this article (doi:10.1186/s12911-017-0508-3) contains supplementary material, which is available to authorized users.

Extended use of endovascular aneurysm sealing: Chimneys for juxtarenal aneurysms

Hostile infrarenal aortic neck anatomy presents a challenge for the endovascular treatment of abdominal aortic aneurysm. Open surgical repair has been seen as the gold standard treatment for juxtarenal abdominal aortic aneurysm; however, endovascular techniques are now becoming more prevalent, particularly in patients deemed high risk for morbidity and mortality with open repair. The morphology of an aneurysm is a determinant of long-term outcomes, and short aneurysm necks are associated with poorer outcomes and a higher rate of secondary reinterventions. Parallel grafts have been used in combination with endovascular aneurysm repair to elongate the sealing zone into the paravisceral segment of the aorta. This technique is associated with a risk of proximal Type I endoleak due to "guttering." This risk may be decreased when parallel grafts are used in combination with endovascular aneurysm sealing and, as such, this technique may represent an alternative to current techniques for the treatment of juxtarenal abdominal aortic aneurysm, such as the use of conventional bifurcated grafts (with or without parallel grafts) and fenestrated endovascular stent grafts.

Endovascular aneurysm sealing for infrarenal abdominal aortic aneurysms: 30-day outcomes of 105 patients in a single centre

OBJECTIVE

Endovascular aneurysm sealing (EVAS) has been proposed as a novel alternative to endovascular aneurysm repair (EVAR) in patients with infrarenal abdominal aortic aneurysms (AAA). The early clinical experience, technical refinements, and learning curve of EVAS in the treatment of AAA at a single institution are presented.

METHODS

One-hundred and five patients were treated with EVAS between March 2013 and November 2014. Prospective data were recorded on consecutive patients receiving EVAS. Data included demographics, preoperative aneurysm morphology, and 30-day outcomes, including rates of endoleak, limb occlusion, reintervention, and death. Postoperative imaging consisted of duplex ultrasound and computed tomographic angiography.

RESULTS

The mean age of the cohort was 76 ± 8 years and 12% were female. Adverse neck morphology was present in 72 (69%) patients, including aneurysm neck length <10 mm (20%), neck diameter >32 mm (18%), β-angulation >60° (21%), and conical aneurysm neck (51%). There was one death within 30 days. The incidence of Type 1 endoleak within 30 days was 4% (n = 4); all were treated successfully with transcatheter embolisation. All four proximal endoleaks were associated with technical issues that resulted in procedure refinement, and all were in patients with adverse proximal aortic necks. The persistent Type 1 endoleak rate at 30 days was 0% and there were no Type 2 or Type 3 endoleaks. Angioplasty and adjunctive stenting were performed for postoperative limb stenosis in three patients (3%).

CONCLUSIONS

EVAS appears to be associated with reasonable 30-day outcomes despite the necessity of procedural evolution in the early adoption of this technique. EVAS appears to be applicable to patients with challenging aortic morphology and endoleak rates should reduce with procedural experience. The utility of EVAS will be defined by the durability of the device in long-term follow-up, although the absence of Type 2 endoleaks is encouraging.

Bayesian neural network approach for determining the risk of re-intervention after endovascular aortic aneurysm repair

This article proposes a Bayesian neural network approach to determine the risk of re-intervention after endovascular aortic aneurysm repair surgery. The target of proposed technique is to determine which patients have high chance to re-intervention (high-risk patients) and which are not (low-risk patients) after 5 years of the surgery. Two censored datasets relating to the clinical conditions of aortic aneurysms have been collected from two different vascular centers in the United Kingdom. A Bayesian network was first employed to solve the censoring issue in the datasets. Then, a back propagation neural network model was built using the uncensored data of the first center to predict re-intervention on the second center and classify the patients into high-risk and low-risk groups. Kaplan-Meier curves were plotted for each group of patients separately to show whether there is a significant difference between the two risk groups. Finally, the logrank test was applied to determine whether the neural network model was capable of predicting and distinguishing between the two risk groups. The results show that the Bayesian network used for uncensoring the data has improved the performance of the neural networks that were built for the two centers separately. More importantly, the neural network that was trained with uncensored data of the first center was able to predict and discriminate between groups of low risk and high risk of re-intervention after 5 years of endovascular aortic aneurysm surgery at center 2 (p = 0.0037 in the logrank test).

The morphological applicability of a novel endovascular aneurysm sealing (EVAS) system (Nellix) in patients with abdominal aortic aneurysms

OBJECTIVE

Endovascular aneurysm sealing (EVAS) using the Nellix system is a promising alternative to endovascular repair (EVR) and open surgery for abdominal aortic aneurysms (AAA). The aim of this study was to investigate the proportion of patients with AAA who are morphologically suitable for treatment with Nellix.

METHODS

Patients presenting with AAA were investigated at two regionalised vascular units. Separate cohorts were identified, who had undergone infrarenal EVR, open aneurysm repair, fenestrated endovascular repair (FEVR) or non-operative management. Pre-operative morphology was quantified using three-dimensional computed tomography according to a validated protocol. Each aneurysm was assessed for compliance with the instructions for use (IFU) of Nellix

RESULTS

776 patients were identified with mean age 75 ± 9 years. 730/776 (94.1%) had undergone infrarenal EVR, 6/776 (0.8%) open repair, 27/776 (3.5%) FEVR and 13/776 (1.7%) had been managed non-operatively. 544/776 (70.1%) of all AAA were morphologically suitable for Nellix. 533/730 (73.0%) of patients who had undergone infrarenal EVR were compliant with Nellix IFU, compared with 497/730 (68.1%), 379/730 (51.9%) and 214/730 (29.3%) with the IFU for Medtronic Endurant (p = .04) or Cook Zenith (p < .01) and Gore C3 Excluder (p < .01) endografts respectively.

CONCLUSIONS

Nellix technology appears widely applicable to contemporary infrarenal AAA practice, and may provide an option for patients that are outside current EVR device instructions for use. However, formal outcomes study is still required, and will ultimately dictate the clinical relevance of this feasibility study. The major limitation to anatomic suitability for Nellix is currently the maximum patent lumen diameter of large AAA.

Predicting aortic complications after endovascular aneurysm repair

Background

Lifelong surveillance is standard after endovascular repair of abdominal aortic aneurysm (EVAR), but remains costly, heterogeneous and poorly calibrated. This study aimed to develop and validate a scoring system for aortic complications after EVAR, informing rationalized surveillance.

Methods

Patients undergoing EVAR at two centres were studied from 2004 to 2010. Preoperative morphology was quantified using three-dimensional computed tomography according to a validated protocol, by investigators blinded to outcomes. Proportional hazards modelling was used to identify factors predicting aortic complications at the first centre, and thereby derive a risk score. Sidak tests between risk quartiles dichotomized patients to low- or high-risk groups. Aortic complications were reported by Kaplan–Meier analysis and risk groups were compared by log rank test. External validation was by comparison of aortic complications between risk groups at the second centre.

Results

Some 761 patients, with a median age of 75 (interquartile range 70–80) years, underwent EVAR. Median follow-up was 36 (range 11–94) months. Physiological variables were not associated with aortic complications. A morphological risk score incorporating maximum aneurysm diameter (P &lt; 0·001) and largest common iliac diameter (measured 10 mm from the internal iliac origin; P = 0·004) allocated 75 per cent of patients to a low-risk group, with excellent discrimination between 5-year rates of aortic complication in low- and high-risk groups at both centres (centre 1: 12 versus 31 per cent, P &lt; 0·001; centre 2: 12 versus 45 per cent, P = 0·002).

Conclusion

The risk score uses commonly available morphological data to stratify the rate of complications after EVAR. The proposals for rationalized surveillance could provide clinical and economic benefits.

Aortic rupture and sac expansion after endovascular repair of abdominal aortic aneurysm

Background

Long-term concerns about the durability of endovascular aortic aneurysm repair (EVAR) remain after the publication of controlled trials. Increased expertise in endograft technology, case selection and postoperative reintervention has created a need for reappraisal of the longer-term efficacy of EVAR using contemporary data.

Methods

Patients undergoing infrarenal EVAR between 2004 and 2010 were studied prospectively. Morphological compliance with manufacturers' instructions for use (IFU) was established using three-dimensional computed tomography. The primary outcome measures were all-cause and aneurysm-related mortality, postoperative rupture, reintervention and sac expansion. These adverse events were reported using Kaplan–Meier survival analysis, with comparison within, or outside IFU by the log rank test.

Results

Some 478 patients of median age 76 years had a median aneurysm diameter of 62·9 mm. Median follow-up was 44 (range 11–94) months; 198 (41·4 per cent) were compliant with IFU. The 30-day mortality rate was 2·1 per cent (10 of 478 patients): nine (2·0 per cent) of 455 patients who had elective and one (4 per cent) of 23 patients who had non-elective surgery. Aneurysm-related mortality was 0·897 deaths per 100 person-years, and all-cause mortality was 8·558 deaths per 100 person-years, with significantly lower survival outside IFU (P = 0·012). Two patients had a late rupture (0·138 per 100 person-years), of whom one died. There were 6·120 reinterventions per 100 person-years, with no difference for aneurysms treated outside IFU (P = 0·136). Primary sac expansion occurred in 6·721 per 100 person-years and secondary sac expansion in 4·142 per 100 person-years.

Conclusion

In this series EVAR had a lower aneurysm-related mortality rate than demonstrated in early controlled trials, and with lower sac expansion rates than reported from image repositories. Data from earlier studies should be applied to current practice with caution.

AAA with a challenging neck: early outcomes using the Endurant stent-graft system

OBJECTIVES

The efficacy and safety of endovascular aneurysm repair is disputable in aneurysms with a short, angulated, wide, conical, or thrombus-lined neck making a reliable seal difficult to achieve. The influence of a challenging neck on early results using the Endurant stent-graft system in high risk patients was investigated.

MATERIALS AND METHODS

A retrospective study conducted on a prospectively compiled database of 72 elective patients with challenging neck treated with the Endurant system (Endurant Stent Graft, Medtronic AVE, Santa Rosa, CA, USA). These patients were compared to a control group (n = 65) without significant neck problems. Endpoints were early technical and clinical success, deployment accuracy and differences in operative details at one month follow-up. Data are reported as mean and standard deviation or as absolute frequency and percentage (%). Normality distribution and homogeneity of variances were tested by Shapiro-Wilks and Levene tests, respectively. Inter-group comparisons for each variable were made by t-test or χ2-test or Fisher exact test. A p < 0.05 was considered statistically significant.

RESULTS

Mean age was 76.12 years; 76.6% were males. Risk factors and pre-operative variables did not differ significantly between the two groups. Mean neck length was 10.56 mm in patients with challenging anatomies and 22.85 mm in controls. Patients with a challenging neck differed significantly (p < 0.001) from controls in terms of mean infrarenal (37.67° vs. 20.12°) and suprarenal angle (19.63° vs. 15.57°); 82% of patients with a challenging neck were ASA III/IV (vs. 86%). Technical success was 100%, with four unplanned proximal extension in challenging group. No type I endoleaks or aneurysm-related deaths occurred in either group; major complications were 1.54% vs. 1.39% (p = 0.942). Operative details were similar in both groups.

CONCLUSION

Treatment with the Endurant stent-graft is technically feasible and safe, yielding satisfactory results even in challenging anatomies. Medium- and long-term data are needed to verify durability, but early results are promising.

Ethylene vinyl alcohol copolymer (Onyx) to seal type 1 endoleak. A new technique

The aim of this study was to investigate whether the liquid embolic agent Onyx, an ethylene vinyl alcohol copolymer, can be used to seal type 1 endoleaks during endovascular aortic repair (EVAR). Six patients with large aortic aneurysms and remaining type 1 endoleaks during or after EVAR were treated with Onyx embolization through a microcatheter placed in the proximal neck in five cases and in the distal neck in one case. Four of the patients were treated using the chimney technique. The type 1 endoleak was primarily sealed by Onyx in all six patients. There was no distal embolization. Two patients had complications during follow-up. One patient had occlusions of chimney grafts to the renal arteries and to one leg extension. These occlusions were not anatomically related to Onyx embolization. One patient had late stentgraft migration of the Onyx-treated distal neck with aneurysm rupture 18 months after treatment. Early experience of Onyx embolization as a bailout solution of type 1 endoleaks after complicated EVAR is promising. However, effective seal with Onyx does not prevent late stentgraft migration. More reported patients and longer follow-up are necessary to evaluate this new technique.