Endovascular stent-graft in abdominal aortic aneurysms: the relationship between patent vessels that arise from the aneurysmal sac and early endoleak

OnyxTMGel or Coil versus Hydrogel as Embolic Agents in Endovascular Applications: Review of the Literature and Case Series

This review focuses on the use of conventional gel or coil and "new" generation hydrogel used as an embolic agent in endovascular applications. In general, embolic agents have deep or multidistrict vascular penetration properties as they ensure complete occlusion of vessels by exploiting the patient's coagulation system, which recognises them as substances foreign to the body, thus triggering the coagulation cascade. This is why they are widely used in the treatment of endovascular corrections (EV repair), arteriovenous malformations (AVM), endoleaks (E), visceral aneurysms or pseudo-aneurysms, and embolisation of pre-surgical or post-surgical (iatrogenic) lesions. Conventional gels such as Onyx or coils are now commercially available, both of which are frequently used in endovascular interventional procedures, as they are minimally invasive and have numerous advantages over conventional open repair (OR) surgery. Recently, these agents have been modified and optimised to develop new embolic substances in the form of hydrogels based on alginate, chitosan, fibroin and other polymers to ensure embolisation through phase transition phenomena. The main aim of this work was to expand on the data already known in the literature concerning the application of these devices in the endovascular field, focusing on the advantages, disadvantages and safety profiles of conventional and innovative embolic agents and also through some clinical cases reported. The clinical case series concerns the correction and exclusion of endoleak type I or type II appeared after an endovascular procedure of exclusion of aneurysmal abdominal aortic (EVAR) with a coil (coil penumbra released by a LANTERN microcatheter), the exclusion of renal arterial malformation (MAV) with a coil (penumbra coil released by a LANTERN microcatheter) and the correction of endoleak through the application of Onyx 18 in the arteries where sealing by the endoprosthesis was not guaranteed.

Impact of Patent Lumbar Arteries on Aneurysm Sac Enlargement with Type II Endoleak after Endovascular Aneurysm Repair

OBJECTIVE

This study aimed to investigate the impact of the number of patent lumbar arteries (LAs) on sac enlargement after endovascular aneurysm repair (EVAR).

METHODS

This was a retrospective cohort single centre registry study. Between January 2006 and December 2019, 336 EVARs were reviewed using a commercially available device excluding type I or type III endoleaks during a follow up of ≥ 12 months. Patients were divided into four groups based on the pre-operative patency of the inferior mesenteric artery (IMA) and high (≥ 4) or low (≤ 3) number of patent LAs: Group 1, patent IMA and high number of patent LAs; Group 2, patent IMA and low number of patent LAs; Group 3, occluded IMA and a high number of patent LAs; Group 4, occluded IMA and low number of patent LAs.

RESULTS

Groups 1, 2, 3, and 4 included 124, 104, 45, and 63 patients, respectively. The median follow up duration was 65.1 months. Significant differences in the incidence of overall type II endoleak (T2EL) at discharge between Group 1 and Group 2 (59.7% vs. 36.5%, p < .001) and between Group 3 and Group 4 (33.3% vs. 4.8%, p < .001) were observed. In patients with a pre-operatively patent IMA, the rate of freedom from aneurysm sac enlargement was significantly lower in Group 1 than in Group 2 (69.0% vs. 81.7% five years after EVAR, p < .001). In patients with a pre-operatively occluded IMA, the freedom rate from aneurysm sac enlargement was not significantly different between Groups 3 and Group 4 (95.0% vs. 100% five years after EVAR, p = .075).

CONCLUSION

A high number of patent LAs seemed to have a significant role in sac enlargement with T2EL when the IMA was patent pre-operatively, whereas a high number of patent LAs seemed to have limited influence on sac enlargement when the IMA was occluded pre-operatively.

Routine Inferior Mesenteric Artery Embolisation is Unnecessary Before Endovascular Aneurysm Repair

OBJECTIVE

A type II endoleak is the most common complication during surveillance after endovascular aneurysm repair (EVAR), and a patent inferior mesenteric artery (IMA) is a known risk factor for an endoleak. The effect of routine IMA embolisation prior to EVAR on overall outcome is unknown. The aim of the study was to compare two strategies: routine attempted IMA embolisation prior to EVAR (strategy in centre A) and leaving the IMA untouched (strategy in centre B).

METHODS

Patients were treated with EVAR in two centres during the period 2005 - 2015, and the data were reviewed retrospectively. The primary endpoints were re-intervention rate due to type II endoleaks and the late IMA embolisation rate. Secondary endpoints included EVAR related re-intervention, sac enlargement, aneurysm rupture, and open conversion rates.

RESULTS

Strategy A was used to treat 395 patients. The IMA was patent in 268 (67.8%) patients, and embolisation was performed in 164 (41.5%). The corresponding figures for strategy B were 337 patients with 279 (82.8%) patent IMAs, two (0.6%) of which were embolised. The mean duration of follow up was 70 months for strategy A and 68.2 months for strategy B. The re-intervention rates due to a type II endoleak were 12.9% and 10.4%, respectively (p = .29), with no significant difference in the rate of re-interventions to occlude a patent IMA (2.0% and 4.7%, respectively; p = .039). The EVAR related re-intervention rate was similar, regardless of strategy (24.1% and 24.6%, respectively; p = .93). Significant sac enlargement was seen in 20.3% of cases treated with strategy A and in 19.6% treated with strategy B (p = .82). The rupture and conversion rates were 2.5% and 2.1% (p = .69) and 1.0% and 1.5% (p = .40), respectively.

CONCLUSION

The strategy of routinely embolising the IMA does not seem to yield any significant clinical benefit and should therefore be abandoned.

Risk Analysis of Aneurysm Sac Enlargement Caused by Type II Endoleak after Endovascular Aortic Repair

BACKGROUND

Although the preoperative risk factors associated with the occurrence of type II endoleak (ETII) after endovascular aortic repair (EVAR) have gradually become more evident, the preoperative risk factors associated with aneurysm sac enlargement caused by ETII remain unclear. This study aimed to determine the preoperative risk factors associated with aneurysm sac enlargement caused by ETII after EVAR.

METHODS

This retrospective cohort study reviewed 519 EVARs performed for true abdominal aortic aneurysm between January 2006 and December 2018 at our institution. EVARs using commercially available bifurcated devices with no type I or III endoleaks during follow-up and with ≥12 months follow-up were included. A total of 320 patients were enrolled in the study. To identify the preoperative risk factors of sac enlargement after EVAR, Cox regression analysis was used to assess preoperative data.

RESULTS

The median follow-up period was 60.8 months. Overall, 135 of 320 patients (42%) had ETII during follow-up, and 47 of 135 patients (35%) developed aneurysm sac enlargement. Multivariate analysis revealed that chronic kidney disease (CKD) stage ≥4 (hazard ratio [HR], 4.65; 95% confidence interval [CI], 2.13-10.15; P = 0.001), patent inferior mesenteric artery (IMA) (HR, 17.85; 95% CI, 2.46-129.73; P< 0.001), and number of patent lumbar arteries (LAs) (HR, 1.37; 95% CI, 1.13-1.68; P= 0.002) were risk factors of aneurysm sac enlargement caused by ETII.

CONCLUSIONS

CKD stage ≥4, patent IMA, and number of patent LAs were independent risk factors for aneurysm sac enlargement after EVAR. In particular, patent IMA had the highest HR and seemed to have the greatest impact on long-term aneurysm sac enlargement. Hence, taking preoperative measures to address a patent IMA appears to be important in reducing the incidence of sac enlargement.

Repair of abdominal aortic aneurysms: preoperative imaging and evaluation

Imaging is a critical component of the pre-procedure evaluation and planning of endovascular aneurysm repair (EVAR). Imaging is the mainstay for proper assessment of procedural candidacy, relevant vascular anatomy, device selection, and surgical approach. Computed tomography angiography (CTA) has long been considered the preferred modality for pre-operative imaging and evaluation prior to EVAR. Recently, advances in image quality and software technology have further enhanced the proceduralist's ability to plan and perform EVAR. In this review, we highlight the current state of the art to provide interventionalists a contemporary assessment of the available tools for pre-operative imaging and evaluation prior to EVAR.

Chronological Change of the Sac after Endovascular Aneurysm Repair

Purpose:

The purpose of this study was to evaluate the potential risk factors of type II endoleak and sac growth after endovascular aneurysm repair (EVAR) and the outcomes of secondary interventions.

Materials and Methods:

Ninety seven patients underwent elective EVAR for infrarenal abdominal aortic aneurysms in two tertiary centers between April 2005 and July 2013. Clinical and imaging parameters were compared among sac growth (>5 mm) and non-growth groups. Risk factors associated with sac growth and persistent type II endoleak were analyzed. The outcomes of reinterventions for persistent type II endoleak were determined.

Results:

Sac growth was observed in 20 cases (20.6%) and endoleak was found in 90% of them compared to 28.6% (22/77) in the non-growth group (P<0.001). The majority of endoleaks were type II (36/40) and 80.5% were persistent. Sac diameter, neck diameter and number of patent accessory arteries were also statistically significant for sac growth. On multivariate analysis, grade of calcification at the neck, grade of mural thrombus at the inferior mesenteric artery and number of patent accessory arteries were risk factors of persistent type II endoleak. Twenty six reinterventions were done for 16 patients with persistent type II endoleak, with a technical success rate of 88.5%, yet 55.5% showed sac growth regardless of technical success. There were no ruptures during the follow-up period.

Conclusion:

Sac growth after EVAR was mostly associated with persistent type II endoleak. Secondary interventions using transarterial embolization is partially effective in achieving clinical success.

The Influence of Preoperative Aneurysmal Thrombus Quantity and Distribution on the Development of Type II Endoleaks with Aneurysm Sac Enlargement After EVAR of AAA

PURPOSE

To determine the influence of preoperative aneurysmal thrombus quantity and distribution on the development of type II endoleak with aneurysm sac enlargement after endovascular aneurysm repair (EVAR).

MATERIALS AND METHODS

We retrospectively analyzed the pre- and postoperatively performed CT scans of 118 patients who had follow-up imaging for at least 1 year after EVAR available. We assessed preoperative thrombus perimeter (T Peri), diameter (T Dia), cross-sectional area (T CSA), and volume (T Vol). The preoperative thrombus distribution was classified into no thrombus, semilunar-shaped (anterior, right side, left side, posterior) thrombus, and circumferential type thrombus. The number of preoperative patent aortic side branches (ASB) was identified. Endpoint was type II endoleak with aneurysm volume (A Vol) increase of ≥5 % during follow-up.

RESULTS

During follow-up (2 years, range 1-9 years), 17 patients with type II endoleak had significant A Vol increase. Less preoperative T Peri, T Dia, T CSA, and T Vol were associated with A Vol increase. A circumferential thrombus distribution significantly protected against aneurysm enlargement (p = 0.028). The variables with the strongest significance for A Vol increase were preoperative T Vol/A Vol ratio (OR 0.95; p = 0.037) and number of patent ASB (OR 3.52; p < 0.001).

CONCLUSION

A low preoperative T Vol/A Vol ratio and a high number of patent ASB were associated with aneurysm sac enlargement after EVAR.

Contrast-enhanced ultrasound after endovascular aortic repair-current status and future perspectives

An increasing number of patients with abdominal aortic aneurysms (AAAs) are undergoing endovascular aortic repair (EVAR) instead of open surgery. These patients require lifelong surveillance, and the follow-up imaging modality of choice has been traditionally computed tomography angiography (CTA). Repetitive CTA imaging is associated with cumulative radiation exposure and requires the administration of multiple doses of nephrotoxic contrast agents. Contrast-enhanced ultrasound (CEUS) has emerged as an alternative strategy in the follow-up of patients with EVAR and demonstrates high sensitivity and specificity for detection of endoleaks. In fact, a series of studies have shown that CEUS is at least performing equal to computed tomography for the detection and classification of endoleaks. This article summarizes current evidence of CEUS after EVAR and demonstrates its usefulness via various patient cases.

Detecting Aortic Graft Complications: A Spectrum of Computed Tomography Findings

Endovascular aneurysm repair (EVAR) is a successful technique as well as an excellent alternative to the surgical management of abdominal aortic aneurysms. EVAR has improved the mortality and morbidity of many patients who would have otherwise suffered greatly from the consequences of abdominal aortic aneurysms. However, EVAR is not without complications. Some complications require lifelong surveillance, whereas others may necessitate immediate surgical intervention. We discuss the various modalities available for the surveillance as well as the common complications that can be seen on computed tomography.

Predictive Factors for Type II Endoleaks after Treatment of Abdominal Aortic Aneurysm by Conventional Endovascular Aneurysm Repair

BACKGROUND

The aim of this study was to identify the predictive factors for the development of type II endoleaks (EL-II) after endovascular aneurysm repair (EVAR).

METHODS

We assessed the preoperative and postoperative computed tomography data of 308 patients who underwent EVAR between 2000 and 2012 and in 84 of whom primary or secondary EL-II occurred. The data analyzed were: demographics, number and diameter of lumbar arteries (LAs), inferior mesenteric artery (IMA), median sacral artery (MSA), accessory renal arteries (ARas), maximum diameter of infrarenal abdominal aortic aneurysm, diameter and length of proximal aortic neck. Statistical analysis was performed using Stata software (version 12). Categorical parameters were compared between groups using chi-squared or Fisher's exact tests as appropriate. Continuous variables were analyzed using Student's t-test or Mann-Whitney test as appropriate (normality studied by the Shapiro-Wilk and homoscedasticity verified using the Fisher-Snedecor test).

RESULTS

Of the 308 patients included (mean age, 73.8 ± 8.74 years), 284 (92%) were men, 61 (20%) were smokers, 113 (37%) had chronic obstructive pulmonary disease, 215 (70%) were taking antiplatelet. Respectively, 13, 51, 60, 103, 28, 40, 2, and 7 patients had 1, 2, 3, 4, 5, 6, 7, and 8 patent LAs. Before surgery, 221 IMAs and 136 MSA were patent. The sources of EL-II were: LA (n = 51), IMA (n = 22), MSA (n = 1), IMA and LA (n = 8), IMA and ARa (n = 1), and unknown (n = 1). Logistic regression models adjusting for clinically relevant covariables (age, American Society of Anesthesiologists, smoking status, dyslipidemia, and diuretics) were proposed to study morphologic EL-II predictive factors, first in the entire population, and then in the more specific population for whom IMA was patent. Risk factors of occurrence EL-II were: permeability of the IMA (70 patients [83%] vs. 155 [69%], P = 0.01), IMA diameter (3.49 mm vs. 2.71 mm, P < 0.001), number of LAs patent higher than or equal to 4 (P < 0.001), the mean LA diameter greater than 2.4 mm (P < 0.001), and MSA diameter (2.28 mm vs. 1.94 mm; P < 0.01).

CONCLUSIONS

Our results show the major role of the number and diameter of the patent aortic branches in the development of EL-II. As they can result in complications increasing the morbidity and mortality after EVAR, it is relevant to identify the risk factors of their occurrence.

Interventional radiology: a half century of innovation

The evolution of modern interventional radiology began over half century ago with a simple question. Was it possible to use the same diagnostic imaging tools that had revolutionized the practice of medicine to guide the real-time treatment of disease? This disruptive concept led to rapid treatment advances in every organ system of the body. It became clear that by utilizing imaging some patients could undergo targeted procedures, eliminating the need for major surgery, while others could undergo procedures for previously unsolvable problems. The breadth of these changes now encompasses all of medicine and has forever changed the way we think about disease. In this brief review article, major advances in the field, as chronicled in the pages of Radiology, will be described.

Essentials of endovascular abdominal aortic aneurysm repair imaging: postprocedure surveillance and complications

OBJECTIVE

Lifelong postprocedural imaging surveillance is necessary after endovascular abdominal aortic aneurysm repair (EVAR) to assess for complications of endograft placement, as well as device failure and continued aneurysm growth. Refinement of the surveillance CT technique and development of ultrasound and MRI protocols are important to limit radiation exposure.

CONCLUSION

A comprehensive understanding of EVAR surveillance is necessary to identify life-threatening complications and to aid in secondary treatment planning.

Can early computed tomography angiography after endovascular aortic aneurysm repair predict the need for reintervention in patients with type II endoleak?

PURPOSE

This study was designed to identify parameters on CT angiography (CTA) of type II endoleaks following endovascular aortic aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA), which can be used to predict the subsequent need for reinterventions.

METHODS

We retrospectively identified 62 patients with type II endoleak who underwent early CTA in mean 3.7 ± 1.9 days after EVAR. On the basis of follow-up examinations (mean follow-up period 911 days; range, 373-1,987 days), patients were stratified into two groups: those who did (n = 18) and those who did not (n = 44) require reintervention. CTA characteristics, such as AAA, endoleak, as well as nidus dimensions, patency of the inferior mesenteric artery, number of aortic branch vessels, and the pattern of endoleak appearance, were recorded and correlated with the clinical outcome.

RESULTS

Univariate and receiver operating characteristic curve regression analyses revealed significant differences between the two groups for the endoleak volume (surveillance group: 1391.6 ± 1427.9 mm(3); reintervention group: 3227.7 ± 2693.8 mm(3); cutoff value of 2,386 mm(3); p = 0.002), the endoleak diameter (13.6 ± 4.3 mm compared with 25.9 ± 9.6 mm; cutoff value of 19 mm; p < 0.0001), the number of aortic branch vessels (2.9 ± 1.2 compared with 4.2 ± 1.4 vessels; p = 0.001), as well as a "complex type" endoleak pattern (13.6 %, n = 6 compared with 44.4 %, n = 8; p = 0.02).

CONCLUSIONS

Early CTA can predict the future need for reintervention in patients with type II endoleak. Therefore, treatment decision should be based not only on aneurysm enlargement alone but also on other imaging characteristics.

Preoperative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow-up

PURPOSE

To review the effect of preoperative embolization of the inferior mesenteric artery (IMA) before endovascular aneurysm repair (EVAR) on subsequent endoleaks and aneurysm growth.

MATERIALS AND METHODS

Between August 2002 and May 2010, 108 patients underwent IMA embolization before EVAR. Coil embolization was performed in all patients in whom the IMA was successfully visualized and accessed during preoperative conventional angiography. In this cohort, the incidences of type II endoleak, aneurysm sac volume enlargement at 24 months, and repeat intervention were compared with a group of 158 consecutive patients with a patent IMA on preoperative computed tomography angiography but not on conventional angiography, who therefore did not undergo preoperative embolization.

RESULTS

The incidence of type II endoleak was significantly higher in patients not treated with embolization (49.4% [78 of 158] vs 34.3% [37 of 108]; P = .015). The incidence of secondary intervention for type II endoleak embolization was also significantly higher in those who did not undergo embolization (7.6% [12 of 158] vs 0.9% [one of 108]; P = .013). At 24 months, an increase in aneurysm sac volume was observed in 47% of patients in the nonembolized cohort (21 of 45), compared with 26% of patients in the embolized cohort (13 of 51; P = .03). No aneurysm ruptures or aneurysm-related deaths were observed in either group. One patient in the embolization group developed mesenteric ischemia and ultimately died.

CONCLUSIONS

Preoperative embolization of the IMA was associated with reduced incidences of type II endoleak, aneurysm sac volume enlargement at 24 months, and secondary intervention.

Type B aortic dissection after standard endovascular repair of abdominal aortic aneurysm

Dissection of the aorta is a rare yet potentially serious complication following endovascular abdominal aortic aneurysm (EVAR). These can lead to visceral branch hypoperfusion, compromise of aneurysm exclusion, arterial dilation or rupture. Intimal injury and dissection in the context of EVAR may be associated with a number of risk factors that include adverse infrarenal neck morphology, device oversizing, barbed fixation and wire manipulation in the proximal aorta. Herein, we describe three cases of type B aortic dissection following EVAR and discuss possible causes. As the applicability of endovascular technology widens, clinicians are reminded of the importance of early recognition and detection of unusual sequelae following EVAR.

[Review of pre- and post-treatment multidetector computed tomography findings in abdominal aortic aneurysms]

The increase in the frequency of abdominal aortic aneurysms (AAA) and the widely accepted use of endovascular aneurysm repair (EVAR) as a first-line treatment or as an alternative to conventional surgery make it necessary for radiologists to have thorough knowledge of the pre- and post-treatment findings. The high image quality provided by multidetector computed tomography (MDCT) enables CT angiography to play a fundamental role in the study of AAA and in planning treatment. The objective of this article is to review the cases of AAA in which CT angiography was the main imaging technique, so that radiologists will be able to detect the signs related to this disease, to diagnose it, to plan treatment, and to detect complications in the postoperative period.

Quality improvement guidelines for imaging detection and treatment of endoleaks following endovascular aneurysm repair (EVAR)

Major concerns after aortic aneurysm repair are caused by the presence of endoleaks, which are defined as persistent perigraft flow within the aortic aneurysm sac. Diagnosis of endoleaks can be performed with various imaging modalities, and indications for treatment are based on further subclassifications. Early detection and correct classification of endoleaks are crucial for planning patient management. The vast majority of endoleaks can be treated successfully by interventional means. Guidelines for Imaging Detection and Treatment of endoleaks are described in this article.

Endovascular management of the patent inferior mesenteric artery in two cases of uncontrolled type II endoleak after endovascular aneurysm repair

Context:

Endovascular aneurysm repair (EVAR) has well documented advantages over traditional open repair and has been widely adopted as the alternative treatment modality for abdominal aortic aneurysm. However, endoleaks specifically type II can be a significant problem with this technique leading to aortic sac expansion and potential rupture. A large number of type II endoleaks are caused by persistent inferior mesenteric artery (IMA) retrograde bleeding. Various methods to try to manage this complication have been previously described. IMA embolization via the marginal artery of Drummond, however, has not been adequately popularized as an alternative less invasive approach to the treatment of type II endoleak.

Case Report:

Two men, ages 77 and 81, underwent uneventful EVAR for 5.5 and 5.0 cm infrarenal abdominal aortic aneurysms, respectively, using Zenith Cook^® bifurcated stent grafts. Computed tomography angiography at 1 and 6 months postoperatively demonstrated small type II endoleaks in both cases which were followed clinically. Subsequent follow-up tomography scan at 12 months revealed persistent type II endoleaks related to retrograde filling from the IMA with significant enlargement of the aneurysm sacs. Both patients underwent successful IMA coil embolization via the marginal artery of Drummond.

Conclusions:

Percutaneous IMA embolization using standard endovascular techniques to access the marginal artery of Drummond is an alternative, and in our opinion, preferred technique for controlling type II endoleaks caused by a persistently patent IMA.

A unique case of a type II endoleak after EVAR caused by patent inferior mesenteric and accessory renal arteries

Type II endoleaks have been viewed as the Achilles' heel of endovascular repair of abdominal aortic aneurysms. This report describes a unique etiology to this common challenge and our approach to endovascular repair.

Multimodal approach to the endovascular treatment of embolisation or exclusion of the renal arteries and their distal and/or polar branches: personal experience

PURPOSE

This study reviews our experience over the last 10 years with procedures of embolisation and/or exclusion of the renal arteries, their parenchymal branches and the polar arteries [renal artery embolisation (RAE)].

MATERIALS AND METHODS

Twenty-seven patients (19 men and eight women; age range 37-93 years; mean 74 years) underwent RAE. The indications were: symptomatic gross haematuria in nine patients (33.3%) (tumour-related in seven and iatrogenic in two), symptomatic inoperable renal tumour in five (18.5%), large subcapsular or perirenal haematoma in three (11.1%) and aneurysm of the main renal artery in two (7.4%). Eight patients (29.6%) scheduled for endovascular aneurysm repair (EVAR) of the abdominal aorta underwent prophylactic embolisation of the renal polar branch arising from the aneurysmal sac or the subrenal aortic neck to prevent the possible revascularisation of the sac. Different embolisation agents were used: coils (17 cases), embolisation particles (14 cases), glue (one case), coated stent (two cases) and mechanical occlusion devices (two cases). In 11 cases, two to three different embolisation agents were used together.

RESULTS

Technical success was achieved in 26/27 patients (96.3%); in one case, embolisation of a polar artery arising from the aneurysmal sac was not possible. One case of gross haematuria recurred 13 months after the procedure and was re-treated with success. There were no cases of major or minor complications.

CONCLUSIONS

RAE is an effective and minimally invasive procedure in the treatment of neoplastic/iatrogenic symptomatic gross haematuria and in the palliative treatment of inoperable renal tumours. One possible new indication is the prophylactic exclusion of the polar artery arising from the neck or the sac of an abdominal aortic aneurysm in patients who are candidates for EVAR. In our experience, we observed very low morbidity and a short hospital stay. This procedure requires the availability of various materials for performing embolisation and experience in their use.

Preoperative variables predict persistent type 2 endoleak after endovascular aneurysm repair

OBJECTIVE

Persistent type 2 endoleaks (PT2, present >or=6 months) after endovascular aneurysm repair (EVAR) are associated with adverse outcomes. This study evaluated the preoperative risk factors and natural history of PT2 in order to define a population at high risk.

METHODS

From January 1999 to December 2007, 595 of 832 EVAR patients had long-term computed tomography follow-up and comprised the study cohort. Preoperative anatomic and clinical variables were correlated with PT2 using Cox regression. Composite hazard ratios (HRs) were constructed with clusters of high-risk preoperative variables. Primary end points, including spontaneous resolution, sac enlargement >5 mm, and freedom from reintervention, were evaluated using Kaplan-Meier analysis.

RESULTS

There were 136 PT2 patients (23%) with a median follow-up of 34.8 months (range, 6.4-121.2 months). Positive predictive factors included patent inferior mesenteric artery (IMA; HR, 4.00; 95% confidence interval [CI], 1.62-9.90; P = .003), increasing number of patent lumbar arteries (HR, 1.24; 95% CI, 1.10-1.41; P = .0006), increasing age (HR, 1.04; 95% CI, 1.01-1.06; P = .005), and increasing luminal diameter on CT-contrast opacified lumen (HR, 1.03; 95% CI, 1.02-1.05; P = .0001). During follow-up, spontaneous PT2 resolution occurred in 34 patients (25%), sac diameter remained stable in 63 (46%), and rupture occurred in 2 (1.5%). Kaplan-Meier analysis estimated that 35.2% +/- 5.6% (95% CI, 23.8%-46.2%) of PT2 resolve spontaneously at 5 years after the index procedure. Freedom from sac enlargement >5 mm was 54.6% +/- 7.2% (95% CI, 40.6%-69.4%) at 5 years. Fifty-nine reinterventions were performed in 39 patients with PT2. Freedom from reintervention was 67.3% +/- 5.0% (95% CI, 57.0%-77.0%) at 5 years. The combination of a patent IMA and one risk factor of more than six patent lumbar arteries, maximum luminal diameter >30 mm, or age >70 years increased the odds of PT2 approximately ninefold. The combination of a patent IMA and any two risk factors increased the odds of PT2 approximately 18-fold.

CONCLUSIONS

Several readily identifiable preoperative variables are associated with PT2 whose natural history was benign in but 35% of patients. On the basis of the composite high-risk HRs, there is accordingly a cohort of patients in whom perioperative interventions to preclude PT2 should be considered.

Improving endothelial cell adhesion and proliferation on titanium by sol-gel derived oxide coating

In-stent restenosis becomes increasingly prevalent as a difficult-to-treat disease. An alternative therapeutic strategy is enhancing endothelialization on metallic stent surfaces. This study attempted to modify surface chemistry and topography of commercial pure titanium (cp-Ti) by different sol-gel derived oxide coatings (TiO(2), SiO(2), SiO(2)/TiO(2), and Nb(2)O(5)) to improve endothelialization. The physiochemical properties of the modified surfaces were characterized by ellipsometry, atomic force microscope, and sessile-drop method. The cell adhesion/proliferation quantity, cell adhesion morphology, and focal adhesion protein expression were evaluated with human pulmonary microvascular endothelial cell line. The thickness of oxide coatings approximates to 100 nm; significantly rougher nanoporous structure was found in the TiO(2) and Nb(2)O(5) coatings than that of cp-Ti. SiO(2) coating possesses the highest surface energy (75.1 mJ/m(2)) and the lowest was for cp-Ti (45.7 mJ/m(2)). TiO(2) coating showed significantly higher endothelial cell adhesion rate than others; TiO(2), Nb(2)O(5), and TiO(2)/SiO(2) coatings exhibited higher endothelial proliferation in 3-day assays than noncoated Ti. In hemocompatible test, they also showed good hemocompatibility. These results offer the insight into that certain oxide coatings on titanium could significantly improve endothelial cell adhesion and proliferation especially in early period, which will favor reaching the endothelialization rapidly and suitable as matrix for "endothelial seeding" stent.

Fluid-Structure Interaction Analyses of Stented Abdominal Aortic Aneurysms

Rupture of abdominal aortic aneurysms (AAAs) alone is the thirteenth leading cause of death in the United States. Thus, reliable AAA-rupture risk prediction is an important advancement. If repair becomes necessary, the minimally invasive technique of inserting a stent-graft (SG), commonly referred to as endovascular aneurysm repair (EVAR), is a viable option in many cases. However, postoperative complications, such as endoleaks and/or SG migration, may occur. Computational fluid-structure interaction simulations provide physical insight into the hemodynamics coupled with multi-wall mechanics' function as an assessment tool for optimal SG placement and improved device design.

Predictive Factors, Morphologic Effects, and Proposed Treatment Paradigm for Type II Endoleaks after Repair of Infrarenal Abdominal Aortic Aneurysms

PURPOSE

To evaluate the predictive factors and outcome of type II endoleaks after endovascular repair of infrarenal abdominal aortic aneurysms with use of a Zenith endograft.

MATERIALS AND METHODS

Patients classified at high risk were enrolled in a prospective study and evaluated with serial cross-sectional imaging techniques. The effect of a type II endoleak on sac behavior and associated factors were analyzed. Type II endoleaks were categorized as absent, persistent, or transient, and the morphologic effects were determined. Logistic regression and classification tree were used to predict which patients may be at risk for persistent type II endoleaks.

RESULTS

A total of 273 patients were enrolled. Patients were excluded in the absence of a minimum of 6 months digital data or the presence of endoleak not classified as type II. Two hundred four patients met inclusion criteria, with a median follow-up period of 24 months (range, 6-60 months). Early type II endoleak was detected in 35 patients (17%), which resolved spontaneously in 17 cases. There were 18 patients with persistent endoleak, 17 patients with transient type II endoleak, and 169 patients with no endoleak. Aneurysm enlargement was detected in seven patients with persistent endoleak (39%), no patients with transient type II endoleak, and one patient with no endoleak. No variables were predictive of the development of persistent endoleak. The relative risk of aneurysmal growth was 77 with persistent endoleak. Successfully treated persistent endoleaks were not associated with any growth.

CONCLUSIONS

Persistent endoleaks are associated with sac growth. Transient type II endoleaks have a benign course and do not require treatment. Successful treatment of persistent endoleak ameliorates the risk of growth.

Persistent type 2 endoleak after endovascular repair of abdominal aortic aneurysm is associated with adverse late outcomes

OBJECTIVE

Type 2 endoleak occurs in up to 20% of patients after endovascular aneurysm repair (EVAR), but its long-term significance is debated. We reviewed our experience to evaluate late outcomes associated with type 2 endoleak.

METHODS

During the interval January 1994 to December 2005, 873 patients underwent EVAR. Computed tomography (CT) scan assessment was performed < or =1 month of the operation and at least annually thereafter. Sequential 6-month CT scan follow-up was adopted for those patients with persistent type 2 endoleaks, and reintervention was limited to those with sac enlargement >5 mm. Study end points included overall survival, aneurysm sac growth, reintervention rate, conversion to open repair, and abdominal aortic aneurysm (AAA) rupture. Preoperative variables and anatomic factors potentially associated with these endpoints were assessed using multivariate analysis.

RESULTS

We identified 164 (18.9%) patients with early (at the first follow-up CT scan) type 2 endoleaks. Mean follow-up was 32.6 months. In 131 (79.9%) early type 2 endoleaks, complete and permanent leak resolution occurred < or =6 months. Endoleaks persisted in 33 patients (3.8% of total patients; 20.1% of early type 2 endoleaks) for >6 months. Transient type 2 endoleak (those that resolved < or =6 months of EVAR) was not associated with adverse late outcomes. In contrast, persistent endoleak was associated with several adverse outcomes. AAA-related death was not significantly different between patients with and without a type 2 endoleak (P = .78). When evaluating patients with no early endoleak vs persistent endoleak, freedom from sac expansion at 1, 3, and 5 years was 99.2%, 97.6%, and 94.9% (no leak) vs 88.1%, 48.0%, and 28.0% (persistent) (P < .001). Patients with persistent endoleak were at increased risk for aneurysm sac growth vs patients without endoleak (odds ratio [OR], 25.9; 95% confidence interval [CI] 11.8 to 57.4; P < .001). Patients with a persistent endoleak also had a significantly increased rate of reintervention (OR, 19.0; 95% CI, 8.0 to 44.7); P < .001). Finally, aneurysm rupture occurred in 4 patients with type 2 endoleaks. Freedom from rupture at 1, 3, and 5 years for patients with a persistent type 2 endoleak was 96.8%, 96.8%, and 91.1% vs 99.8%, 98.5%, and 97.4% for patients without a type 2 endoleak. Multivariate analysis demonstrated persistent type 2 endoleak to be a significant predictor of aneurysm rupture (P = .03).

CONCLUSIONS

Persistent type 2 endoleak is associated with an increased incidence of adverse outcomes, including aneurysm sac growth, the need for conversion to open repair, reintervention rate, and rupture. These data suggest that patients with persistent type 2 endoleak (>6 months) should be considered for more frequent follow-up or a more aggressive approach to reintervention.

Imaging Techniques for Detection and Management of Endoleaks after Endovascular Aortic Aneurysm Repair1

Endovascular aortic aneurysm repair (EVAR) is evolving into a viable alternative to open surgical repair for many patients with abdominal and thoracic aortic aneurysms. Endoleak development is a complication of EVAR and represents one of the limitations of this procedure. Endoleaks represent blood flow outside the stent-graft lumen but within the aneurysm sac. Lifelong imaging surveillance of patients after EVAR is critical to detect endoleaks for the patient's benefit and to determine the long-term performance of the stent-graft. Although computed tomographic angiography is the most commonly used examination for imaging surveillance, magnetic resonance angiography, ultrasonography, and digital subtraction angiography all have a role in endoleak detection and management. This review will focus on imaging techniques used for endoleak detection and the role imaging surveillance plays in the overall care of the post-EVAR patient.

Complications of Endovascular Repair of Abdominal Aortic Aneurysms: A Review

The endovascular procedure for repair of abdominal aortic aneurysms has had an enormous impact on the treatment of this challenging disease. Complications, however, do occur and it is important to have a thorough understanding of the array of complications and appropriate management strategies. In this review of endovascular complications, we describe early and late complications paying particular attention to preventive, treatment and surveillance strategies.

Endovascular repair of an infrarenal abdominal aortic aneurysm with a dominant middle mesenteric artery: A case report

The middle mesenteric artery is a rare anomalous mesenteric vessel that may supply variable segments of the colon. Occlusion of this artery during endovascular aortic aneurysm repair may bear a significant risk of bowel ischemia. We report the successful interventional treatment of a patient with a 5.3 cm infrarenal abdominal aortic aneurysm, sparing a dominant middle mesenteric artery.

An animal model for type II endoleaks with use of a tsuzumi drum-shaped stent-graft

PURPOSE

To create an animal model of type II endoleaks after endoluminal deployment of a specially designed stent-graft (SG).

MATERIALS AND METHODS

Five swine were used. A tsuzumi drum-shaped SG consisting of a covered Z stent with its diameter narrowed at the center was deployed in the midthoracic aorta. In this way, a residual space (RS) was created between the aortic wall and the graft to simulate an aneurysm sac. A 5-F catheter was placed into the RS, and then aortography, RS angiography, and pressure measurements were performed. Follow-up was performed at 3 and 10 days after the procedure. Mean pressure indexes (MPIs) were calculated as the ratio of the mean RS pressure to the aortic pressure. Histologic examination was also performed.

RESULTS

RSs with two or three pairs of intercostal arteries were successfully created in all cases. Aortography showed two type II endoleaks in five swine just after SG deployment and four type II endoleaks at 10 days. RS angiography showed circulation between the RS and the intercostal arteries in all cases. The mean MPI was 69.4% +/- 10.4% just after SG deployment and increased to 87.8% +/- 5.2% at 10 days. By gross examination, RS patency was retained.

CONCLUSIONS

A swine model of type II endoleaks was successfully created endoluminally. This model does not require direct surgery to the aorta and its side branches and promises to be useful to study the mechanism of and therapy for type II endoleaks.

Type 2 Endoleaks after Abdominal Aortic Aneurysm Stent Grafting with Systematic Mesenteric and Lumbar Coil Embolization

We evaluated the results of our policy of systematic coil embolization of the inferior mesenteric artery (IMA) and/or lumbar arteries (LAs) prior to endovascular abdominal aortic aneurysm (AAA) repair (EVAR). We retrospectively reviewed all patients undergoing EVAR over a 4-year period at one hospital. Results were analyzed using uni- and multivariate analyses. Fifty-five male patients with an average age of 71 years were evaluated. Follow-up averaged 15 +/- 13 months. The IMA was either coiled or occluded in 30 cases. One or more LAs were coiled in 29 patients. An average of 1.3 LAs per patients were coiled (range 0-6). There were no immediate or late complications from coiling. At last follow-up, 14 AAAs showed no change in diameter, one increased by 2 mm, and the remainder (n = 40) decreased by 7.5 +/- 6 mm in maximal diameter. Only five (9%) type 2 endoleaks were detected during follow-up. Three were associated with AAA size increase. Four of the five were treated with additional coiling, with good results. By logistic regression, neither endoleak occurrence nor AAA shrinkage correlated with LA or IMA coiling. However, by multivariate analysis, completeness of lumbar coiling correlated negatively with aneurysm shrinkage (p = 0.04) and IMA coiling correlated positively with aneurysm shrinkage (p = 0.04). Coil embolization of the IMA and/or LAs prior to EVAR can be safely accomplished in a large number of cases and is associated with a low incidence of type 2 endoleaks. We cannot at present demonstrate a benefit to LA embolization in terms of endoleak prevention or AAA shrinkage. However, IMA embolization may be of benefit in terms of AAA shrinkage.