Fractured Sealing Rings in a Fenestrated Anaconda Stent-Graft.

An 81 year-old man presented with an asymptomatic juxtrarenal abdominal aortic aneurysm and was subsequently treated with a fenestrated endovascular Anaconda stent-graft. Surveillance imaging within the first postoperative year demonstrated a lower proximal sealing ring fracture. In the second postoperative surveillance year, the upper proximal sealing ring was also fractured with extension of the wire into the right paravertebral space. Despite these sealing ring fractures, there were no endoleak nor visceral stent complications and the patient continued on standard surveillance protocols. There are an increasing number of reports of fractured proximal sealing rings with the fenestrated Anaconda platform. Those analysing the surveillance scans of patients treated with this device should stay vigilant for the development of this complication.

Endovascular Preservation of Segmental Arteries during Treatment of Thoracoabdominal Aortic Aneurysms with Fenestrated/Branched Stent Grafts: Feasibility and Outcomes.

PURPOSE: To evaluate the technical success, feasibility, and outcomes of endovascular preservation of segmental arteries (SAs) during fenestrated/branched endovascular aortic repair (F/B-EVAR). MATERIALS AND METHODS: A multicenter, retrospective study was conducted in consecutive patients treated with F/B-EVAR and a branch or fenestration for SA preservation. Eleven patients (median age, 57 years; range, 45-73 years; 7 men) were included. RESULTS: Twelve SAs were preserved. Stent grafts were custom made with fenestrations, branches, or a combination of both in 1, 2, and 5 patients, respectively. A t-Branch stent graft was used in 2 patients, and a physician-modified thoracic stent graft with a branch was used in 1 patient. Eight branches and 4 fenestrations were used for the preservation of 12 SAs. Four fenestrations and 1 branch for the SAs were not bridged and were left for perfusion of the corresponding SAs. Technical success was achieved in 10 of 11 (91%) patients. No early mortality occurred. Early morbidities included renal insufficiency without dialysis in 1 patient and partially delayed paraplegia in 1 patient. Before discharge, computed tomography angiography (CTA) showed patency of all the SAs. The median follow-up duration was 30 months (range, 10-88 months). Late death occurred in 1 patient. Two SAs were occluded in 1 patient with 2 unstented fenestrations, as determined using 1-year follow-up CTA. This patient did not develop spinal cord ischemia (SCI). Other SAs remained patent during follow-up. One patient with a type IIIc endoleak was treated by relining of bridging stents. CONCLUSIONS: Endovascular preservation of SAs with F/B-EVAR for thoracoabdominal aortic aneurysm is feasible and safe in select patients and may add to preventive measures for SCI.

Costs and Budget Impact of Collagen-Based Vascular Closure Device Versus Manual Compression Following Peripheral Endovascular Procedures.

BACKGROUND: The objective of this study was to evaluate the annual costs and budget impact of using a vascular closure device to achieve hemostasis following femoral access endovascular procedures in England, compared with manual compression. METHODS: A budget impact model was developed in Microsoft® Excel, based on the estimated number of peripheral endovascular procedures eligible for day-case management performed annually by the National Health Service in England. The clinical effectiveness of vascular closure devices was captured based on the requirement for inpatient stays and the incidence of complications. Data for endovascular procedures, time to hemostasis, length of hospital stay, and complications were collected from public sources and the published literature. There were no patients involved in this study. Model outcomes are reported as estimated number of bed days and annual costs to the National Health Service for all peripheral endovascular procedures in England, and the average cost per procedure. The robustness of the model was tested in a sensitivity analysis. RESULTS: The model estimated savings for the National Health Service of up to £4.5 million annually if vascular closure devices were used in every procedure instead of manual compression. The model estimated an average cost saving of £176 per procedure for vascular closure devices over manual compression, primarily due to fewer inpatient stays. The sensitivity analysis demonstrated that the proportion of day-case procedures for vascular closure devices and manual compression was a key driver of costs and savings. CONCLUSIONS: The use of vascular closure devices for achieving hemostasis after peripheral endovascular procedures may be associated with lower resource use and cost burden, compared with manual compression, based on shorter time to hemostasis and ambulation and an increased likelihood of a day-case procedure.

Onyx™ Cast Fragmentation After Embolization of Endoleaks.

PURPOSE: Endoleaks are common following endovascular aneurysm repair (EVAR), and the liquid embolic material Onyx has been widely used in their treatment. We report our experience of long-term morphological changes of Onyx casts on surveillance imaging. MATERIALS AND METHODS: We identified 10 patients over 10 years who underwent Onyx embolization in our institution. Morphological changes of Onyx casts were assessed on surveillance radiographs and computed tomography (CT) scans. Relevant outcome data and sequelae were obtained via electronic patient records. RESULTS: Twelve procedures were performed on 10 cases, 9 for type 2, and 1 for a type 1a endoleak. Five cases showed evidence of Onyx fragmentation on follow-up imaging ranging from a single fracture to gross fragmentation with migration of fragments. Of these 5, 3 had achieved primary success but 2 went on to develop recurrence of endoleak. Onyx volume ranged from 4 to 46.5 ml (median 10.5 ml) per patient with larger volumes demonstrating the most marked fragmentation on follow-up. Follow-up ranged from 9 months to 8 years (median 2.25 years). CONCLUSION: To our knowledge, this is the first report of Onyx fragmentation after endoleak embolization. If long-term morphological stability of the Onyx cast is necessary to maintain aneurysm seal, then Onyx may not offer a permanent solution to some patients with post-EVAR endoleaks. Our study cannot ascertain whether the observed changes were the cause or the effect of ongoing aneurysm growth, persistent endoleak, and/or other forces acting on the solidified polymer, but it raises important questions on the use of Onyx in this setting.

Observational study on the incidence of nephrogenic systemic fibrosis in patients with renal impairment following gadoterate meglumine administration: the NSsaFe study.

BACKGROUND: Nephrogenic systemic fibrosis (NSF) is a rare life-threatening condition strongly associated with the administration of gadolinium-based contrast agents in patients with severe or endstage renal impairment. PURPOSE: To prospectively determine the incidence of NSF in patients with renal impairment after administration of gadoterate meglumine. STUDY TYPE: Prospective. POPULATION: In all, 540 patients with moderate, severe, or endstage renal impairment, scheduled to undergo a routine contrast-enhanced MRI with gadoterate meglumine. Mean age was 69.7 ± 12.7 years (range: 21-95) with 58.4% of males. FIELD STRENGTH/SEQUENCE: 1.5T or 3.0T, sequence according to each site practice. ASSESSMENT: Medical history, indication(s) for current MRI and adverse events were recorded for each patient. Patients were followed up over 2 years after administration with three visits separated by at least 3 months to detect any signs/symptoms suggestive of NSF. STATISTICAL TESTS: Descriptive. RESULTS: Renal impairment was graded as moderate for 69.4% of patients, severe for 16.0% and endstage for 12.1%; 2.6% had undergone a kidney transplant. Estimated glomerular filtration rate ranged from 4 to 59 mL/min/1.73 m2 except one value of 74 mL/min/1.73 m2 in a patient with kidney transplant. Central nervous system exploration was the main MRI indication (34.7%) and mean dose injected was 0.22 ± 0.09 mL/kg. Overall, 446 patients (82.6%) attended at least one follow-up visit and completed the NSF questionnaire and 329 (60.9%) attended the 2-year visit. No suspicion of NSF was reported in all 446 patients, including 119 patients with severe or endstage renal impairment. No deaths and no adverse events were reported during the MRI examination and the usual period of follow-up after gadoterate meglumine administration. DATA CONCLUSION: No cases of NSF were observed in the 446 patients with moderate to endstage renal impairment followed up over a maximum of 2 years after injection of gadoterate meglumine. LEVEL OF EVIDENCE: 2 Technical Efficacy Stage: 4 J. Magn. Reson. Imaging 2020;51:607-614.

Aneurysm Growth After Endovascular Sealing of Abdominal Aortic Aneurysms (EVAS) with the Nellix Endoprosthesis.

OBJECTIVE: The aim of this study was to measure the incidence of post endovascular aneurysm sealing (EVAS) abdominal aortic aneurysm (AAA) growth, and its association with stent migration, in a cohort of patients with differing compliance to old and new Instructions For Use (IFU). METHODS: A retrospective single centre study was conducted to review the computed tomography (CT) and clinical data of elective, infrarenal EVAS cases, performed as a primary intervention, between December 2013 and March 2018. All included patients had a baseline post-operative CT scan at one month and at least one year follow up. The primary outcome measure was the incidence of AAA growth and its association with stent migration. AAA growth was defined as a ≥5% increase in aortic volume between the lowermost renal artery and the aortic bifurcation post EVAS at any time during follow up, in comparison to the baseline CT scan. Migration was defined according to the ESVS guidelines, as > 10 mm downward movement of either Nellix stent frame in the proximal zone. RESULTS: Seventy-six patients were eligible for inclusion in the study (mean age 76 ± 7.4 years; 58 men). AAA growth was identified in 50 of 76 patients (66%); adherence to IFU did not affect its incidence (mean growth within IFU-2016 compliant cohort vs. non-compliant: 16% vs. 13%, p = .33). Over time, the incidence of AAA growth increased, from 32% at one year to 100% at four years. AAA growth by volume was progressive (p < .001), as its extent increased over time. Migration was detected in 16 patients and there was a statistically significant association with AAA growth (13 patients displayed migration and AAA growth, p = .036). CONCLUSION: Patients treated with EVAS are prone to AAA growth, irrespective of whether their aortic anatomy is IFU compliant. AAA growth by volume is associated with stent migration. Clinicians should continue close surveillance post EVAS, regardless of whether patients are treated within IFU.

Meta-analysis of the accuracy of contrast-enhanced ultrasound for the detection of endoleak after endovascular aneurysm repair.

OBJECTIVE: The purpose of this systematic review and meta-analysis was to investigate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) for detection of endoleak after endovascular aneurysm repair (EVAR). METHODS: We searched electronic bibliographic databases for original articles comparing concurrent CEUS and computed tomography angiography for detection of endoleak after EVAR. We assessed the methodologic quality of the studies with the Quality Assessment of Diagnostic Accuracy Studies-2 tool. We constructed 2 × 2 contingency tables for all selected studies including true-positive, false-positive, false-negative, and true-negative results for all endoleaks and for type I and type III endoleaks. We used a mixed-effects logistic regression model to estimate summary sensitivity and specificity. We developed hierarchical summary receiver operating characteristic curves and calculated the area under the curve (AUC). RESULTS: We identified 26 studies reporting a total of 2638 paired scans in 2217 patients. The major risk of bias of the selected studies pertained to blinding for the index test and the reference standard. The pooled sensitivity and specificity of CEUS for all endoleaks were 0.94 (95% confidence interval [CI], 0.89-0.97) and 0.93 (95% CI, 0.89-0.96), respectively. The AUC was 0.98 (95% CI, 0.93-0.99). The summary estimate of sensitivity and specificity for type I and type III endoleaks was 0.97 (95% CI, 0.8-1.00) and 1.00 (95% CI, 0.99-1.00), respectively. The AUC was 1.00 (95% CI, 0.99-1.00). CONCLUSIONS: CEUS has a high sensitivity and specificity in the detection of endoleaks after EVAR. CEUS is a useful tool in EVAR surveillance.

Stent Frame Movement Following Endovascular Aneurysm Sealing in the Abdominal Aorta.

PURPOSE: To investigate the incidence and extent of stent frame movement after endovascular aneurysm sealing (EVAS) in the abdominal aorta and its relationships to aneurysm growth and the instructions for use (IFU) of the Nellix endograft. METHODS: A retrospective single-center study was conducted to review the clinical data and computed tomography (CT) images of 75 patients (mean age 76±7.6 years; 57 men) who underwent infrarenal EVAS and had a minimum 1-year follow-up. The first postoperative CT scan at 1 month and the subsequent scans were used to measure the distances between the proximal end of the stent frames and a reference visceral vessel using a previously validated technique. Device migration was based on the Society of Vascular Surgery definition of >10-mm downward movement of either Nellix stent frame in the proximal landing zone; a more conservative proximal displacement measure (downward movement ⩾4 mm) was also recorded. Patients were categorized according to adherence to the old (2013) or new (2016) Nellix IFU. Aneurysm diameter was measured for each scan; a change ⩾5 mm was deemed indicative of aneurysm growth. RESULTS: Over a median follow-up of 24 months (range 12-48), proximal displacement ⩾4 mm occurred in 42 (56%) patients and migration >10 mm in 16 (21%), with similar incidences in the right and left stent frames. Proximal displacement was significantly more frequent among patients whose anatomy did not conform to any IFU (p=0.025). Presence of aneurysm growth ⩾5 mm was observed in 14 (19%) patients and was significantly associated with proximal displacement ⩾4 mm (p=0.03). CONCLUSION: Infrarenal EVAS may be complicated by proximal displacement and migration, particularly when performed outside the IFU. The definition of migration used for endovascular aneurysm repair may be inappropriate for EVAS; a new consensus on definition and measurement technique is necessary.

Temporal Changes in Intraluminal Thrombus Volume Within Abdominal Aortic Aneurysms: Implications for Planning Endovascular Aneurysm Sealing.

PURPOSE: To explore whether or not there are temporal changes in the abdominal aortic aneurysm (AAA) and intraluminal thrombus (ILT) volumes between planning and implantation of the endovascular aneurysm sealing (EVAS) device and how these changes influence lumen volume. METHODS: A retrospective review was conducted of 51 AAA patients (mean age 76±7.1 years; 36 men) in whom 2 serial preoperative computed tomography angiograms (CTAs) had been performed within 1 to 18 months before fenestrated endovascular repair. The 2 preoperative CTAs were analyzed to identify changes in total sac, ILT, and lumen volumes. RESULTS: Over a median 7.0 months (interquartile range 4, 10), 46 (90%) of 51 AAAs increased in volume between the 2 CTAs. ILT volume increased in 44 aneurysms. In contrast, lumen volume increased in 31 and decreased in 20 AAAs. There was a strong correlation between changes in AAA volume and ILT volume (rs=0.859, p<0.001), which remained significant after adjustment for initial volumes (rs=0.815; p<0.001). There was no correlation between the time interval separating the 2 CTAs and changes in AAA volume (rs=0.115; p=0.421), changes in ILT volume (rs=0.084; p=0.599), or changes in lumen volume (rs=0.060; p=0.676). The AAA growth rate (defined as the change in AAA size/days between CTAs) showed a weak correlation with ILT volume (rs=0.272, p=0.054), which disappeared after adjustment for initial AAA size (rs=-0.002, p=0.991). Between the 2 CTAs, 12 aneurysms crossed the new <1.4 Nellix maximum aorta/lumen diameter ratio. CONCLUSION: As AAAs grow, the increase in aortic volume is largely occupied by additional ILT formation, with minimal change in lumen volume. These changes may alter the suitability of the aneurysm for the Nellix device and could have implications for EVAS planning and device deployment.

Endovascular Repair of Type IIIb Endoleak With the Amplatzer Septal Occluder.

PURPOSE: To report the successful treatment of a type IIIb endoleak with an Amplatzer Septal Occluder. CASE REPORT: A 76-year-old man was found to have a type IIIb endoleak in the proximal body component of a fenestrated graft at 4-year surveillance imaging; the leak was associated with rapid aneurysm growth. The anatomy of the graft and position of the fabric defect precluded treatment by relining with a secondary endograft. The defect was demonstrated with catheter angiography, sized with an angioplasty balloon, and repaired using an Amplatzer Septal Occluder. Follow-up imaging at 6 months showed no endoleak and marked reduction in the aneurysm size. CONCLUSION: The Amplatzer Septal Occluder may be considered as an option for managing type IIIb endoleaks.

Anatomical Applicability of Endovascular Aneurysm Sealing Techniques in a Consecutive Cohort of Fenestrated Endovascular Aneurysm Repairs.

PURPOSE: To determine how many endovascular aneurysm sealing (EVAS) procedures with/without off-label use of chimneys (ChEVAS) could have been performed in a cohort of patients who had undergone fenestrated endovascular aneurysm repair (FEVAR). METHODS: Sixty patients (median age 76.3 years; 54 men) who underwent FEVAR in our institution between 2013 and 2015 were selected for the study. The median aneurysm diameter was 62.0 mm (interquartile range 59.3, 69.0). Preoperative computed tomography angiograms (CTA) were anonymized and sent to 2 physicians with experience of more than 40 ChEVAS interventions. These ChEVAS planners were blinded to the study purpose and asked to agree upon an EVAS/ChEVAS plan. The primary outcome was the percentage of the FEVAR patients in whom an EVAS/ChEVAS was technically possible. The secondary outcomes were a comparison of seal zones, number of target vessels, and device cost. RESULTS: An EVAS-based intervention would have been technically possible in 56 (93.3%) of the FEVAR patients. The median proximal aortic seal zone was significantly more distal in the EVAS/ChEVAS procedures vs the FEVAR cases (zone 8 vs zone 7, p<0.001) and fewer target vessels were involved (median 2 vs 3, p<0.001). The cost of the EVAS/ChEVAS device was 66% of the FEVAR device. Planners would not currently advocate an EVAS-based intervention in 43 (76.8%) of these 56 patients due to concerns regarding the risk of migration associated with the lumen thrombus ratios observed. CONCLUSION: EVAS is technically feasible in the majority of patients undergoing FEVAR in our institution but currently advocated in only 23.2%. The seal zone was more distal, fewer target vessels were involved, and the device cost was lower in the planned EVAS/ChEVAS interventions.

Clinical Outcome after Endovascular Sealing of Abdominal Aortic Aneurysms: A Retrospective Cohort Study.

BACKGROUND: The aim of this study is to present the clinical outcome of endovascular aneurysm sealing (EVAS) with the Nellix endoprosthesis in patients with abdominal aortic aneurysms treated in our institution. METHODS: This is a retrospective, single center, observational cohort study. A departmental database was interrogated to extract demographics, clinical information, and outcome of all patients treated with EVAS between December 2013 and December 2015. Outcome measures included technical success (successful device deployment and absence of any endoleak at completion angiography), mortality, major complications, incidence of endoleaks, aneurysm rupture, and reintervention. RESULTS: Sixty-five patients (49 men) with a mean (standard deviation) age of 78 (6.9) years were successfully treated with EVAS, with no 30-day mortality. The cohort included 1 patient with ruptured aneurysm, 9 patients with late complications of previous aortoiliac repairs (2 open, 7 endovascular), and 4 patients who required a total of 9 visceral chimneys for juxtarenal aneurysms. Six patients (9%) suffered major postoperative complications and 4 (6%) required intervention. There were no early or late endoleaks or aneurysm ruptures. After a median (range) follow-up of 12 (0-24) months, there was no aneurysm-related mortality; 2 patients (3%) required late aneurysm-related interventions. CONCLUSIONS: EVAS can be performed with good outcomes up to 2 years postoperatively. Longer follow-up on larger cohorts is needed to prove the efficacy of this technique.

Perigraft hygroma - a rare cause of post-EVAR aneurysm growth.

Development of perigraft hygromas following repair of abdominal aortic aneurysms is extremely rare. A case is presented of a patient who was found to have a large hygroma despite two re-interventions on a previous EVAR.

Migration of the Nellix endoprosthesis.

BACKGROUND: This study reports the incidence and sequelae of migration of the Nellix (Endologix Inc, Irvine, Calif) endoprosthesis after endovascular aneurysm sealing. METHODS: A review was performed of the follow-up imaging of all endovascular aneurysm sealing patients in a university hospital endovascular program who had a minimum follow-up of 1 year. The first postoperative and latest follow-up computed tomography scans were used to measure the distances between the proximal and distal borders of the stent grafts relative to reference vessels using a previously validated technique. Device migration was based on previously established criteria and defined as any stent graft movement of ≥4 mm related to a predefined reference vessel. Device movement in a caudal direction was given a positive value, and movement in a cranial direction was denoted by a negative value. RESULTS: Eighteen patients (35 stent grafts) were eligible for inclusion in this retrospective review. The mean preoperative abdominal aortic aneurysm diameter was 57 mm (standard deviation [SD], 5; range, 50-67 mm) and aortic neck length was 30 mm (SD, 16; range, 6-62 mm). Proximal migration, according to study definitions, was identified in six stent grafts (17%), all in a caudal direction. At 1 year the mean proximal migration distance was +6.6 mm (SD, 1.6; range, +4.7-+9.2 mm). Migration occurred in a single stent graft in four patients and bilaterally in one. No distal migration occurred. CONCLUSIONS: Proximal migration of the Nellix endoprosthesis does occur and was without any sequelae in our series. Further investigations into the long-term positional stability of the Nellix device, together with a more thorough understanding of the etiology and consequences of migration, are required.

Renal Stent Crushed During Open Aneurysmorrhaphy for Endoleak After Fenestrated EVAR.

PURPOSE: To report a complication of renal stent crushing during open aneurysmorrhaphy performed 10 years after fenestrated endovascular aneurysm repair (FEVAR). CASE REPORT: A 67-year-old male patient underwent elective FEVAR of a juxtarenal aortic aneurysm. Uncovered balloon-expandable stents were placed through the fenestrations for the superior mesenteric and right renal arteries; the left renal artery received a Jostent covered balloon-expandable stent. The uncovered right renal stent was noted to be crushed on the first imaging after FEVAR, but was left untreated; the right kidney was thereafter significantly smaller than the left. Over several years, the aneurysm expanded, and type II endoleak involving the lumbar arteries was embolized with coils 7 years after FEVAR. Despite this, the aneurysm continued to enlarge and reached a diameter of 12.8 cm. Open aneurysmorrhaphy and selective ligation of lumbar arteries was performed 10 years after FEVAR. The first surveillance imaging after aneurysmorrhaphy demonstrated a new finding of a crushed left renal stent, which was presumed to be related to surgical instrumentation. The stent was successfully redilated percutaneously, and renal function remained stable. Computed tomography demonstrated a normal appearance of the left renal covered stent after re-expansion. Doppler ultrasound after 7.5 months showed normal renal perfusion. CONCLUSION: Balloon-expandable visceral artery stents are susceptible to crush injury during aortic surgery. Consideration should be given to early imaging after such surgery in FEVAR patients.

Type IIIb Endoleak With the Endurant Stent-Graft.

PURPOSE: To report 2 cases of type IIIb endoleak with the Endurant stent-graft and postulate the cause for the events. CASE REPORT: A type IIIb endoleak was diagnosed at open conversion for a ruptured aneurysm 4 years after implantation of an Endurant stent-graft. In the other case, the endoleak was diagnosed at angiography 4 years after the Endurant stent-graft was implanted; the stent-graft was relined. In both cases the fabric hole was in the body of the stent-graft at the level of the top of the contralateral limb. CONCLUSION: The cause of the type IIIb endoleaks in these cases was fabric erosion likely due to interaction between the bare metal at the top of the contralateral limb and the fabric of the stent-graft body.

A Rescue Technique for Intraoperative Proximal Migration of a Nellix Stent During Endovascular Aneurysm Sealing.

PURPOSE: To describe a technique to rescue intraoperative migration of 1 of the 2 Nellix stents during endovascular sealing of abdominal aortic aneurysms (EVAS). TECHNIQUE: The technique requires advancement and inflation of a 10-mm angioplasty balloon into the inlet of the migrated stent via an upper limb approach. Inflation of the balloon allows completion of EVAS without risking the contralateral endobag occluding the inlet of the migrated stent. CONCLUSION: This technique allows safe completion of EVAS without compromising stent patency or aneurysm seal and should be considered when intraoperative migration of a Nellix stent occurs despite appropriate precautions.

Endovascular Aneurysm Sealing Is Associated With Reduced Radiation Exposure and Procedure Time Compared With Standard Endovascular Aneurysm Repair.

PURPOSE: To compare indirect measures of radiation exposure and operating time between endovascular aneurysm sealing (EVAS) and endovascular aneurysm repair (EVAR) for the treatment of abdominal aortic aneurysm (AAA). METHODS: The study compared 32 consecutive patients (mean age 78 years; 21 men) with AAA who underwent standard EVAS with 32 consecutive patients (mean age 78 years; 25 men) treated with EVAR between November 2013 and May 2015. Electronic medical records and image archiving databases were interrogated to retrieve relevant information and scans. Screening time and dose area product (DAP) were the primary outcome measures. Data are presented as median and interquartile range (IQR). Correlations were tested with the Spearman rank coefficient (ρ). RESULTS: The screening time was shorter in EVAS than in EVAR [16 (IQR 14, 20) vs 32 (IQR 26, 38) minutes; p<0.001]. DAP was lower in EVAS than in EVAR [54 (IQR 42, 77) vs 111 (IQR 75, 157) Gy∙cm(2); p<0.001]. Digital subtraction angiography delivered 20% (IQR 15%, 28%) of the DAP in EVAS compared with 14% (IQR 11%, 19%) in EVAR (p<0.001), but the absolute time used on digital subtraction was marginally lower in EVAS than in EVAR [1.07 (IQR 0.52, 1.23) vs 1.19 (IQR 0.70, 1.39) minutes; p=0.037]. The operating time was shorter for EVAS [121 (IQR 105, 146) vs 162 (IQR 145,186) minutes; p<0.001]. There was a moderate correlation between DAP and screening time (ρ=0.597, p<0.001), fluoroscopy time (ρ=0.595, p<0.001), digital subtraction time (ρ=0.301, p=0.015), and operating time (ρ=0.512, p<0.001). CONCLUSION: EVAS is associated with reduced radiation exposure and operating room usage compared with EVAR, which may have safety and financial implications.

Type IIIb Endoleak and Relining: A Mathematical Model of Distraction Forces.

PURPOSE: To examine the changes in distraction force following relining of a conventional abdominal aortic stent-graft with a type IIIb endoleak using the Nellix endovascular sealing device compared to a unilateral stent-graft. METHODS: Relining is often used to repair type IIIb endoleaks, but the consequences to graft stability are unknown. A mathematical model was constructed based on pressure and volume flow through the stent-grafts, incorporating recognized distraction force equations. Steady flow was presumed at peak systolic pressures to calculate the maximum distraction force, with gravity ignored. Distraction forces for 28- to 36-mm-diameter stent-graft bodies with 16-mm limbs were calculated and compared to forces following relining with single and double Nellix devices or the Renu unilateral device. RESULTS: Distraction forces for the 28-, 32-, and 36-mm stent-grafts prior to relining were 5.99, 10.21, and 14.99 N, respectively. Similar forces were reported after relining with bilateral Nellix devices (5.86, 10.08, and 14.86 N, respectively). However, use of a unilateral Nellix increased the distraction forces to 9.92, 14.14, and 18.92 N, respectively. These were comparable to the increase observed after relining with a Renu unilateral stent-graft (9.87, 14.09, and 18.86 N, respectively). The proportional increase in distraction force for a unilateral relining ranged from 26% to 66%, with the greatest increase noted in the smaller diameter main bodies. CONCLUSION: Relining a stent-graft with a type IIIb endoleak using bilateral Nellix devices does not increase the distraction force. However, a unilateral Nellix device or the Renu system could theoretically increase the distraction force by up to 66%, potentially risking migration and type Ia endoleak. In clinical practice, these results suggest that a relining with bilateral Nellix may have benefits over the Renu unilateral stent-graft.