Predicting Rotation in Fenestrated Endovascular Aneurysm Repair Using Finite Element Analysis

Fenestrated endovascular aneurysm repair (FEVAR) is a minimally invasive method of abdominal aortic aneurysm (AAA) repair utilized in patients with complex vessel anatomies. Stent grafts (SG) used in this process contain fenestrations within the device that need to be aligned with the visceral arteries upon successful SG deployment. Proper alignment is crucial to maintain blood flow to these arteries and avoid surgical complications. During fenestrated SG deployment, rotation of the SG can occur during the unsheathing process. This leads to misalignment of the vessels, and the fenestrations and is associated with poor clinical outcomes. The aim of this study was to develop a computational model of the FEVAR process to predict SG rotation. Six patient-specific cases are presented and compared with surgical case data. Realistic material properties, frictional effects, deployment methods, and boundary conditions are included in the model. A mean simulation error of 2 deg (range 1–4 deg) was observed. This model was then used to conduct a parameter study of frictional properties to see if rotation could be minimized. This study showed that increasing or decreasing the coefficients of friction (COF) between the sheath and the vessel walls would decrease the amount of rotation observed. Our model accurately predicts the amount of SG rotation observed during FEVAR and can be used as a preoperative planning tool within the surgical workflow.

MRI for peripheral artery disease: Introductory physics for vascular physicians

Magnetic resonance imaging (MRI) has advanced significantly in the past decade and provides a safe and non-invasive method of evaluating peripheral artery disease (PAD), with and without using exogenous contrast agents. MRI offers a promising alternative for imaging patients but the complexity of MRI can make it less accessible for physicians to understand or use. This article provides a brief introduction to the technical principles of MRI for physicians who manage PAD patients. We discuss the basic principles of how MRI works and tailor the discussion to how MRI can evaluate anatomic characteristics of peripheral arterial lesions.

Analysis of Iliac Artery Geometric Properties in Fenestrated Aortic Stent Graft Rotation

Introduction:

A complication of fenestrated endovascular aneurysm repair is the potential for stent graft rotation during deployment causing fenestration misalignment and branch artery occlusion. The objective of this study is to demonstrate that this rotation is caused by a buildup of rotational energy as the device is delivered through the iliac arteries and to quantify iliac artery geometric properties associated with device rotation.

Methods:

A retrospective clinical study was undertaken in which iliac artery geometric properties were assessed from preoperative imaging for 42 cases divided into 2 groups: 27 in the nonrotation group and 15 in the rotation group. Preoperative computed tomography scans were segmented, and the iliac artery centerlines were determined. Iliac artery tortuosity, curvature, torsion, and diameter were calculated from the centerline and the segmented vessel geometry.

Results:

The total iliac artery net torsion was found to be higher in the rotation group compared to the nonrotation group (23.5 ± 14.7 vs 14.6 ± 12.8 mm−1; P = .05). No statistically significant differences were found for the mean values of tortuosity, curvature, torsion, or diameter between the 2 groups.

Conclusion:

Stent graft rotation occurred in 36% of the cases considered in this study. Cases with high iliac artery total net torsion were found to be more likely to have stent graft rotation upon deployment. This retrospective study provides a framework for prospectively studying the influence of iliac artery geometric properties on fenestrated stent graft rotation.

Prediction of advanced endovascular stent graft rotation and its associated morbidity and mortality

OBJECTIVE

Advanced endovascular aneurysm repair (EVAR) with fenestrated and branched stent grafts is increasingly being used to repair complex aortic aneurysms; however, these devices can rotate unpredictably during deployment, leading to device misalignment. The objectives of this study were to quantify the short-term clinical outcomes in patients with intraoperative stent graft rotation and to identify quantitative anatomic markers of the arterial geometry that can predict stent graft rotation preoperatively.

METHODS

A prospective study evaluating all patients undergoing advanced EVAR was conducted at two university-affiliated hospitals between November 2015 and December 2016. Stent graft rotation (defined as ≥10 degrees) was measured on intraoperative fluoroscopic video of the deployment sequence. Standard preoperative computed tomography angiography imaging was used to calculate the geometric properties of the arterial anatomy. Any in-hospital and 30-day complications were prospectively documented, and a composite outcome of any end-organ ischemia or death was used as the primary end point.

RESULTS

Thirty-nine patients undergoing advanced EVAR were enrolled in the study with a mean age of 75 years (interquartile range [IQR], 71-80 years) and a mean aneurysm diameter of 64 mm (IQR, 59-65 mm). The incidence of stent graft rotation was 37% (n = 14), with a mean rotation of 25 degrees (IQR, 21-28 degrees). A nominal logistic regression model identified iliac artery torsion, volume of iliac artery calcification, and stent graft length as the primary predictive factors. The total net torsion and the total volume of calcific plaque were higher in patients with stent graft rotation, 8.9 ± 0.8 mm^-1 vs 4.1 ± 0.5 mm^-1 (P < .0001) and 1054 ± 144 mm³ vs 525 ± 83 mm³ (P < .01), respectively. The length of the implanted stent grafts was also higher in patients with intraoperative rotation, 172 ± 9 mm vs 156 ± 8 mm (P < .01). The composite outcome of any end-organ ischemia or death was also substantially higher in patients with stent graft rotation (36% vs 0%; P = .004). In addition, patients with stent graft rotation had significantly higher combined rates of type Ib and type III endoleaks (43% vs 8%; P = .03).

CONCLUSIONS

Patients with intraoperative stent graft rotation have a significantly higher rate of severe postoperative complications, and this is strongly associated with higher levels of iliac artery torsion, calcification, and stent graft length. These findings suggest that preoperative quantitative analysis of iliac artery torsion and calcification may improve risk stratification of patients before advanced EVAR.

Rehabilitation Trends After Lower Extremity Amputations in Canada

BACKGROUND

The heterogeneity of medical complications that lead to amputation has resulted in a diverse patient population with differing rehabilitation needs; however, the rehabilitation trends for patients with lower extremity amputations across Canada have not been studied previously.

OBJECTIVE

To describe trends in rehabilitation after lower extremity amputations and the factors affecting rehabilitation length of stay in Canada.

DESIGN

Retrospective cohort analysis.

SETTING

Canadian inpatient rehabilitation facilities that received persons with lower extremity amputations discharged from academic or community hospitals.

PARTICIPANTS

Patients underwent lower extremity amputations between 2006 and 2009 for nontraumatic indications and were then discharged to a rehabilitation facility. Patients were identified from the Canadian Institute for Health Information's Discharge Abstract Database that includes hospital admissions across Canada except Quebec.

INTERVENTIONS

Inpatient rehabilitation after lower extremity amputations.

MAIN OUTCOME MEASURES

Length of stay, discharge destination, and change in total and motor function scores.

RESULTS

The analysis included 5342 persons who underwent lower extremity amputations, 1904 of whom were transferred to a rehabilitation facility (36%). Patients most commonly underwent single below-knee (74%) and above-knee (17%) amputations. The duration of rehabilitation varied by whether the amputation was performed by a vascular (median = 36 days), orthopedic (median = 38 days), or general surgeon (median = 35 days). The overall median length of stay was 36 days. Most patients (72%) subsequently were discharged home and 9% were readmitted to hospital. Predictors of longer rehabilitation included amputation by an orthopedic surgeon (beta = 5.0, P ≤ .01), older age (beta = 0.2, P ≤ .01), and a history of ischemic heart disease (beta = 3.8, P = .03) or congestive heart failure (beta = 5, P = .04). Patients who spent <7 days in hospital were significantly more likely to have a shorter rehabilitation stay (beta = -4, P = .03). Advanced patient age was the only predictor for hospital readmission (odds ratio = 1.03, P ≤ .01).

CONCLUSIONS

Rehabilitation length of stay in Canada after lower extremity amputation varies by the type of surgeon performing the amputation. Advanced age, undergoing surgery in the province of Manitoba, and having a history of ischemic heart disease or congestive heart failure predict a longer rehabilitation stay. A shorter perioperative hospitalization period (<7 days) predicts a shorter rehabilitation duration. Future studies are needed to explore these issues and to optimize the delivery of rehabilitation services to Canadians after lower extremity amputation.

LEVEL OF EVIDENCE

II.

Tuberculous Aneurysm of the Supraceliac Aorta

Significant vascular complications are rare following systemic infections with Mycobacterium tuberculosis (TB). This report describes a 33-year-old man who presented with a short history of abdominal discomfort and febrile episodes with no prior history of infection with TB. Ultrasound, CT scan, and aortography confirmed the presence of a pseudoaneurysm originating from the posterior aspect of the supraceliac aorta at the level of the diaphragm. Via a full thoracoabdominal approach, periaortic inflammatory tissue and the aortic wall itself were debrided, and repair of the pseudoaneurysm was achieved with a synthetic patch. Mycobacterium tuberculosis was isolated from the aortic wall, and anti-TB medications were instituted. Postoperatively the patient did well and was discharged after 14 days. As illustrated by this case, tuberculous mycotic aneurysms of the aorta are optimally treated with a combination of medical and surgical therapy, and early diagnosis is essential to ensure survival.

Midterm Results of Endovascular Infrarenal Abdominal Aortic Aneurysm Repair in High-Risk Patients

Short-term and midterm clinical outcomes after endovascular repair of abdominal aortic aneurysms (AAAs) have been well documented. Evaluation of longer term outcomes is now possible. Here we describe our initial 100 high-risk patients treated with endovascular aneurysm repair (EVAR), all with a minimum of 5 years of follow-up. A retrospective review of prospectively recorded data in a departmental database was undertaken for the first 100 consecutive EVAR patients with a minimum of 5 years (range, 60-105 months) of follow-up performed between December 1997 and June 2001. Information was obtained from surgical follow-up visits and family doctors' offices. Endovascular repair of AAA in high-risk patients can be achieved with acceptably low postoperative mortality and morbidity. Longer term results in this high-risk cohort suggest that EVAR is effective in preventing aneurysm-related deaths at 5 years and beyond. All late mortalities were due to patients' comorbid diseases.

Determination of Functional Outcome Following Upper Extremity Arterial Trauma

Upper extremity arterial trauma may lead to significant disability with a poor functional outcome. This study represents a retrospective review of all trauma patients presenting to a university-affiliated medical center. Patients suffering from upper extremity arterial injuries requiring treatment were identified. The injured vessels were identified along with the mechanism of injury and method of repair. The degree of functional disability was evaluated by using a previously validated questionnaire, the Disabilities of the Arm, Shoulder, and Hand (DASH) Outcome Measure. Between September 1999 and December 2004, 17 patients presented with traumatic arterial injury to the upper extremity, with 9 and 8 patients suffering from blunt and penetrating traumas, respectively. One patient required amputation representing a limb salvage rate of 94%. The mean length of hospitalization was significantly shorter for penetrating trauma (5.1 vs 12 days, P = .03), with blunt trauma victims being more prone to coexisting orthopedic injuries ( P = .009). Length of follow-up did not differ between the 2 groups and ranged from 1-60 months. Patients with blunt trauma tended, although not statistically significant, to have higher DASH scores (61.8 vs 22.8, P = .08), indicating a greater degree of disability. By utilizing a validated disability questionnaire, this study confirms that patients suffering from blunt injuries to upper extremity arteries are more likely to have greater degrees of disability affecting everyday activities.

The Association Between a Surgeon’s Learning Curve With Endovascular Aortic Aneurysm Repair and Previous Institutional Experience

The purpose of the present study was to determine whether an institution’s prior endovascular experience influenced the learning curve of subsequent surgeons. A prospective analysis of the initial 70 endovascular abdominal aortic aneurysm repair (EVAR) cases attempted by an individual surgeon was performed with the primary outcome variable being achievement and 30-day maintenance of initial clinical success. Along with standard statistical analyses, the cumulative sum failure method (CUSUM) was used to analyze the learning curve, with a predetermined acceptable failure rate of 10%. Seventy elective EVAR cases were performed by this surgeon during a 4-year period (2000-2004) (mean age, 73.7 ∓ 5.4 years; mean aneurysm diameter 63.3 ∓ 7.2 mm). Initial clinical success was achieved in 68 of 70 cases (97%), which differed significantly with that of our initial surgeon (88.5%, P = .01). Causes of failure in the present series included 1 early mortality (1.4%) and 1 case of conversion to open repair with no instances of type I endoleak or endograft limb thrombosis. Both surgeons’ cases were plotted sequentially with CUSUM curves revealing a significantly shorter learning curve for the second surgeon. Optimal results were achieved following 10 to 20 EVAR cases, as opposed to 60 cases in the initial series. Such an analysis confirms that as an institution’s experience with EVAR increases, an individual surgeon’s learning curve shortens considerably.

A Canadian population-based description of the indications for lower-extremity amputations and outcomes

BACKGROUND

To our knowledge, there have been no previously published reports characterizing lower-extremity amputations in Canada. The objective of this study was to describe the indications and outcomes of lower-extremity amputations in the Canadian population.

METHODS

We performed a retrospective cohort study of all adult patients who underwent lower-extremity amputation in Canada between 2006 and 2009. Patients were identified from the Canadian Institute for Health Information's Discharge Abstract Database, which includes all hospital admissions across Canada with the exception of the province of Quebec. Pediatric, trauma, and outpatients were excluded.

RESULTS

During the study period, 5342 patients underwent lower-extremity amputations in 207 Canadian hospitals. The mean age was 67 ± 13 years, and 68% were men. Amputations were most frequently indicated after admission for diabetic complications (81%), cardiovascular disease (6%), or cancer (3%). In total, 65% of patients were discharged to another inpatient or long-term care facility, and 26% were discharged home with or without extra support. Most patients were diabetic (96%) and most (65%) required a below-knee amputation. Predictors of prolonged (> 7 d) hospital stay included amputation performed by a general surgeon; cardiovascular risk factors, such as diabetes, hypertension, ischemic heart disease, congestive heart failure, or hyperlipidemia; and undergoing the amputation in the provinces of Newfoundland and Labrador, New Brunswick, or British Columbia.

CONCLUSION

There is variability in the delivery of lower-extremity amputations and postoperative hospital discharges among surgical specialists and regions across Canada. Future work is needed to investigate the reasons for this variability and to develop initiatives to shorten postoperative hospital stays.

Surgical treatments for chronic deep venous insufficiency

Objective: The aim of this study was to critically appraise and synthesize the published evidence regarding the short- and long-term efficacy/effectiveness of surgical techniques for patients with deep venous insufficiency (DVI) refractory to other forms of management.

Methods: All original, published studies on non-pregnant human patients undergoing treatment for deep or mixed deep/superficial/perforator chronic venous insufficiency were identified by systematically searching PubMed, EMBASE, CINAHL, The Cochrane Library, Science Citation Index and the websites of various health technology assessment agencies, research registers and guidelines sites, from January 1990 to July 2003. No language restriction was applied.

Results: A total of two randomized controlled trials and 12 non-randomized comparative studies reported on a variety of procedures ranging from superficial venous surgery (SVS) and subfascial endoscopic perforator surgery (SEPS), through to deep venous reconstruction (including valvuloplasty, transplantation and transposition) for the treatment of DVI. Limited evidence suggested that combined SVS/valvuloplasty is a relatively safe procedure that is potentially more effective than SVS alone in preventing ulcer recurrence in patients with primary DVI in both the short- and mid-term. Evidence for the efficacy of valvuloplasty, bypass, transplantation, SEPS and iliac stenting in the treatment of DVI was inconclusive. The optimal surgery for patients with deep venous obstruction or secondary valvular incompetence remains unclear.

Conclusions: It is unlikely that a large randomized, or even non-randomized, controlled trial will be conducted to ascertain the safety and efficacy of surgery for DVI. However, standardized reporting and collection of data in a registry would be a move forward. In addition, professional bodies should consider providing guidance, in the form of an evidence-based treatment algorithm, that would define when to perform SVS in patients with mixed or deep venous insufficiency and what type of deep venous surgery is considered appropriate for different indications. A prime focus of future research may be to understand why less invasive treatments have failed in patients requiring surgery for DVI and to identify those patients who would benefit most from early surgical intervention.