Nonoperative approach to endotension

Applications of Artificial Intelligence in Acute Abdominal Imaging

Artificial intelligence (AI) is a rapidly growing field with significant implications for radiology. Acute abdominal pain is a common clinical presentation that can range from benign conditions to life-threatening emergencies. The critical nature of these situations renders emergent abdominal imaging an ideal candidate for AI applications. CT, radiographs, and ultrasound are the most common modalities for imaging evaluation of these patients. For each modality, numerous studies have assessed the performance of AI models for detecting common pathologies, such as appendicitis, bowel obstruction, and cholecystitis. The capabilities of these models range from simple classification to detailed severity assessment. This narrative review explores the evolution, trends, and challenges in AI applications for evaluating acute abdominal pathologies. We review implementations of AI for non-traumatic and traumatic abdominal pathologies, with discussion of potential clinical impact, challenges, and future directions for the technology.

Management of Endoleaks After Elective Infrarenal Aortic Endovascular Aneurysm Repair: A Review

Importance

Endovascular aneurysm repair (EVAR) is the dominant treatment strategy for abdominal aortic aneurysms, encompassing 80% of all repairs in the United States. Endoleaks are ubiquitous and affect 30% of patients treated by EVAR, potentially leading to sac enlargement and increased risk of rupture. The care of EVAR patients requires long-term surveillance by a multidisciplinary team. Accordingly, physicians should be familiar with the fundamentals of endoleak management to achieve optimal outcomes, including timely referral for remediation or providing counseling and reassurance when needed.

Observations

PubMed and the Cochrane database were searched for articles published between January 2002 and December 2022 in English, addressing epidemiology, diagnosis, and management of endoleaks after EVAR. Endoleaks can be detected intraoperatively or years later, making lifelong surveillance mandatory. Type I and III have the highest risk of rupture (7.5% at 2 years and 8.9% at 1 year, respectively) and should be treated when identified. Intervention should be considered for other types of endoleak when associated with aneurysm sac growth larger than 5 mm based on current guidelines. Type II endoleaks are the most common, accounting for 50% of all endoleaks. Up to 90% of type II endoleaks resolve spontaneously or are not associated with sac enlargement, requiring only observation. Although the risk of rupture is less than 1%, cases that require reintervention are challenging. Recurrence is common despite endovascular treatment, and rupture can occur without evidence of sac growth. Type IV endoleaks and endotension are uncommon, are typically benign, and primarily should be observed.

Conclusions and Relevance

Endoleak management depends on the type and presence of sac expansion. Type I and III endoleaks require intervention. Type II endoleaks should be observed and treated selectively in patients with significant sac expansion. Since endoleaks can appear any time after EVAR, at least 1 contrast-enhanced computed tomographic angiogram or duplex ultrasound by an experienced laboratory is recommended every 5 years.

Late Type III Endoleak after Loss of Component Overlap after EVAR with AFX2 Device: A Case Report

Addressing the high incidence of late type III endoleaks in previous AFX models, Endologix upgraded the device material and updated its recommendation regarding component overlap. However, whether upgraded AFX2 models are safe for endoleaks remains controversial. Here we report a case of a 67-year-old male with an AFX2-implanted abdominal aortic aneurysm experiencing a delayed type IIIa endoleak. Aneurysmal sac enlargement occurred 36 months post-endovascular aneurysm repair (EVAR), with a computed tomography scan at 52 months revealing component overlap loss and a significant type IIIa endoleak. We performed endograft explantation and endoaneurysmal aorto-bi-iliac interposition grafting. Our findings suggest that sufficient component overlap is necessary when using an AFX2 endograft outside the manufacturer's instructions for use to prevent late type IIIa endoleaks. Moreover, patients who undergo EVAR with AFX2 for tortuous large aortic aneurysms should be carefully monitored for conformational changes.

Occult endoleaks revealed during open conversions after endovascular aortic aneurysm repair in a multicenter experience

BACKGROUND

An occult endoleak (OE) may be the underlying cause of aneurysm sac expansion after endovascular aneurysm repair (EVAR). The aim of this study is to describe intraoperative findings of OE during surgical endograft explantations.

METHODS

This is a retrospective, multicenter analysis of all open conversions (OC) after EVAR from 1997 to 2020 in 12 vascular centers. We excluded patients with a preoperative diagnosis of endograft infection, endograft thrombosis, and thoracic-EVAR. An OE was defined as an endoleak revealed during OC not shown on preoperative imaging, which was likely the real cause for sac enlargement. We reported the number of OE, and we described the type of OE in relation to the initial alleged or associated endoleak. A separate analysis of patients with an initial diagnosis of endotension was also performed.

RESULTS

An OE was found in 32/255 patients (12.5%). In the 78.1% of the cases (25/32) a type II endoleak hid a type I or III endoleak. Endotension was the initial diagnosis of 26/255 patients (10.2%). In 4/26 cases (15.4%), a type I or II OE was revealed. In 5/26 cases (19.2%) an endograft infection was found intraoperatively. In 2/26 cases we found an angiosarcoma. Fifteen cases of endotension (57.7%) remained unexplained.

CONCLUSIONS

OE represent a not negligible cause of EVAR failure. A type II endoleak associated with sac enlargement may actually conceal a higher-flow endoleak. In most of the cases, the initial diagnosis of endotension remains unexplained. However, endotension sometimes conceals severe underlying pathologies such as infections.

Open Abdominal Aortic Repair to Treat Perigraft Seroma after Endovascular Aortic Repair with Endologix AFX2 Endograft

A 75-year-old man with an abdominal aortic aneurysm underwent endovascular aortic repair (EVAR) using an AFX2 endograft with no endoleaks. Nevertheless, the aneurysmal sac increased by 8 mm at 24 months after EVAR despite no detectable endoleaks. Open surgical treatment was performed because of the risk of rupture. Intraoperative findings of much viscous cloudy fluid with no blood flow in the sac suggested that perigraft seroma resulted in sac enlargement. The endografts were replaced by a Dacron graft. Perigraft seroma should be considered as a cause of sac growth after EVAR with AFX2 when there are no detectable endoleaks.

Surgical Findings and Outcomes of Endotension following Endovascular Aneurysm Repair

BACKGROUND

Endotension is one of the detrimental complications after endovascular aneurysm repair (EVAR) and surgical management has been considered as standard of care. However, there is a paucity of data regarding the findings and outcomes of such surgical intervention. The aim of this study was to investigate intraoperative findings and outcomes of surgical treatment for endotension after EVAR.

METHODS

Between January 2005 and October 2018, of the 708 patients who underwent EVAR for aneurysm aortic aneurysm; 12 patients (mean age of 76.1; range 66-88) who underwent open repair for endotension were retrospectively analyzed. The anatomical characteristics of the aorta and surgical findings were reviewed. The rates of early and late procedural complications, and overall mortality were evaluated.

RESULTS

The median interval between the EVAR and surgical conversion was 45.9 months (range 17.1-46.9). Three of the twelve patients underwent emergency surgery due to aneurysm rupture. The median aneurysm sac size, the proximal neck diameter, and the proximal neck length before EVAR were 64 mm, 23.5 mm, and 30.5 mm, respectively, that changed before open repair to 93.5 mm (p = .02), 25 mm (p = .011), and 23 mm (p = .003), respectively. In four of the twelve patients, radiographically undetected endoleak was identified during surgery to be Type Ia, Ib, II, and III, respectively. The rates of early and late procedural complications, and overall mortality were 8.3%, 8.3% and 8.3%, respectively.

CONCLUSIONS

Patients with endotension have a risk of delayed endoleak and aneurysm rupture; secondary intervention should be performed in such cases to prevent fatal complications. Surgical treatment appears to be a curative treatment for endotension with favorable outcomes. In addition, the possibility of an undetected endoleak should be considered as a potential cause of endotension.

Endotension: What do we know and not know about this enigmatic complication of endovascular aneurysm repair

As the use of endovascular approaches to treat aneurysm repair continues to increase, more and more patients have been identified with endoleaks. Five types of endoleaks have been defined. Endotension, or type V endoleak, remains controversial owing to its variable definition across studies and the range of proposed treatments. Thus, we performed a review of the reported studies to summarize the diagnosis and treatment of this rare complication after endovascular aneurysm repair to determine what we do and do not know about this rare form of endoleak. The presence of an endoleak places patients at an increased risk of aneurysm sac enlargement and potential rupture. Although additional research is essential and yet difficult to perform, we sought to provide a guide for the management of this perplexing endoleak known as endotension.

Management of Concealed Type IV Endoleak and Aortic Sac Hygroma by Prone ContrASt EnHancement Computed Tomography Angiography

BACKGROUND

Aortic sac hygroma and concealed endoleaks (EL) after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm needs particular attention with aggressive management as they are associated with rapid sac expansion and rupture risk. However, they can be erroneously reported as type IV or V EL with supine computed tomography (CT) scans, leading to delay in management. Therefore, we describe a novel diagnostic technique, 'Prone contrASt enHanced computed tomography Angiography' (PASHA), to document concealed EL METHODS: We present eight case descriptions with continuous sac expansion after primary EVAR. Management began with diagnosis using the PASHA imaging technique. PASHA is a multiphase CTA positional technique for increasing the accuracy of detecting EL after EVAR. Furthermore, the PASHA imaging technique also guides whether the open or endovascular intervention could be used effectively to manage the sac expansion. In synchrony with the PASHA technique, "EVAR GORE SalvAge FAbric Technique" (ARAFAT) was to salvage previous EVAR.

RESULTS

The PASHA technique diagnosed all cases of type IIIb EL, as it enhanced the degree of contrast infiltration into the aortic sac when microleaks were present. ARAFAT was effectively used in five elderly patients. Another three had an open conversion; two with double breasting of the aortic sac and one EVAR explantation.

CONCLUSIONS

The PASHA protocol helped classify and localize the concealed EL (type IV, V), which were not appropriately diagnosed by supine CT protocols. PASHA and ARAFAT were used as a fully functioning protocol to overcome apparent challenges in accurate diagnosis and subsequent concealed EL management in high-risk patients.

Delayed migration of a thrombosed aortic endograft within a thrombosed aneurysm sac resulting in continued sac expansion and rupture

We present the case of delayed migration of a thrombosed aortic endograft within a thrombosed aneurysm sac that expanded and ruptured. Dilation of the aortic neck likely led to endograft migration and exposure of the occluded endograft and aneurysm sac to systemic pressure. Although no endoleak was identified, a key finding on ultrasound showed mobility of the sac thrombus. This may be an indicator of flow within the sac that may predict potential for rupture. Despite thrombosis of the aortic sac and endograft, the risk of rupture still lingers, and thus continued surveillance of occluded endografts may be prudent.

Comparison of Endovascular Stent Grafts for Abdominal Aortic Aneurysm Repair in Medicare Beneficiaries

BACKGROUND

Increased renal complications have been suggested with suprarenal stent grafts, but long-term analyses have been limited. Therefore, the purpose of this study was to evaluate the effect of endograft choice on perioperative and long-term outcomes.

METHODS

We compared Medicare beneficiaries undergoing endovascular abdominal aortic aneurysms repair from 2005 to 2008 with endografts with infrarenal fixation and a single docking limb (AneuRx, Excluder) to those with suprarenal fixation and 2 docking limbs (Zenith), or a unibody configuration (Powerlink). Propensity score weighting accounted for differences in patient characteristics among the different graft formations, and perioperative mortality, complications, and length of stay and 4-year rates of survival, rupture, and reintervention were compared.

RESULTS

Forty-six thousand one hundred seventy-one Medicare beneficiaries were identified including 11,002 (24%) with suprarenal fixation, 32,909 (71%) with infrarenal fixation, and 2,260 (5%) with a unibody graft. After propensity score weighting, there were no significant differences in patients' baseline clinical and demographic characteristics. The suprarenal fixation patients had higher rates of perioperative mortality (1.7% vs. 1.3%, P < 0.01), renal failure (6.0% vs. 4.7%, P < 0.001), and mesenteric ischemia (0.7% vs. 0.4%, P < 0.01) and longer length of stay (3.4 days vs. 3.0 days, P < 0.001) compared with patients with infrarenal fixation. Unibody grafts had higher rates of renal failure (5.9% vs. 4.7%, P < 0.001), mesenteric ischemia (1.0% vs. 0.4%, P < 0.001), and conversion to open repair (0.7% vs. 0.1%, P < 0.001) compared to those with infrarenal fixation and single docking limbs. At 4 years, mortality remained slightly higher with suprarenal compared to infrarenal fixation (30% vs. 29%, P = 0.047), although these patients had fewer conversions to open repair (0.6% vs. 0.9%, P = 0.03) and aneurysm-related reinterventions (10% vs. 12%, P < 0.01). At 4 years, unibody grafts had more aneurysm-related interventions compared to infrarenal fixation grafts (15% vs. 12%, P < 0.01) but fewer conversions to open repair (0.4% vs. 0.9%, P = 0.02). Late rupture did not differ among the groups.

CONCLUSIONS

Compared to infrarenal fixation devices, patients who underwent EVAR with suprarenal fixation had higher perioperative mortality and renal complications but fewer reinterventions including conversion, while the unibody graft had more perioperative complications and aneurysm-related reinterventions, but fewer conversions to open repair. Although these differences could be explained by selection bias, these data suggest that further comparative effectiveness analyses should be performed to understand the outcomes following EVAR with suprarenal fixation and unibody grafts.

Perigraft fluid collection mimicking graft infection in patients with a para-anastomotic aneurysm

We herein report two cases of perigraft effusion mimicking graft infection after debranching thoracic endovascular repair for an anastomotic pseudoaneurysm of the distal ascending aorta. Both patients presented with a bulging tumor on the sternum. Enhanced computed tomography showed no endoleak, but extension of periprosthetic graft fluid to a subcutaneous sternal wound was present. We suspected a deep sternal wound infection; however, cultures of débrided tissues were negative. After drainage of the subcutaneous fluid or negative pressure wound therapy, both patients were doing well without recurrence of effusion. Endotension was considered to have been associated with enlargement of the perigraft effusion.

Ten-Year Outcomes after Endovascular Aneurysm Repair (Evar) and Magnitude of Additional Procedures

Background and Aims:

With any new technology complications are possible, and problems with first-generation aortic stentgrafts have been extensively reported. The long-term outcome of this patient population and the magnitude of additional secondary procedures are, however, less well covered.

Materials and Methods:

Between February 1997 and November 1999, 48 patients (44 men and 4 women; mean age 70 years; range 54–85) with AAA (average 57mm, range 40–90mm) were treated with a Vanguard® endoprosthesis. Stentgrafts were sized by CT and angiography-based measurements. Results were continuously assessed using contrast-enhanced CT before discharge, 1, 3, 6 and 12 months after the procedure and thereafter annually. Since 2001 plain abdominal X-rays have been performed annually.

Results:

The technical implant success rate was 100%. Median follow-up was 91 months (range 7.6–120 months). None of the patients was lost during this period. Hospital mortality was 0%. There were 25 subsequent deaths (52%), the most common cause being coronary artery disease. There were ten late conversions to open surgical repair, including three emergency operations: two due to rupture and one to thrombosis. EVAR-related complications were encountered in 43 patients (90%): 12 primary endoleaks (all type II), 36 late endoleaks (16 type I, 2 type II and 18 type III), 22 migrations, 25 row separations, 20 thromboses, one endotension and 3 ruptures of the AAA. Secondary procedures were required in 39 patients (81%): 1 re-endografting by aortoiliac bifurcated graft and 3 with a uni-iliac graft; 33 limb graft repairs were performed and 19 infrarenal cuffs were placed. There were 4 late embolizations and 4 attempts, and 6 thrombolyses, four of which were successful. Further, 9 femoro-femoral crossover by-pass and 2 axillo-femoral by-pass operations and 2 amputations were carried out during the follow-up. Only one patient was alive without complications.

Conclusions:

The impact of long-term follow-up of patients treated with the new technology was emphasized in this patient population. A careful surveillance protocol and active endovascular treatment of complications can yield acceptable results and low AAA rupture and aneurysm mortality rates, also with the first-generation endovascular graft. A new technology, however, may involve unpredictable problems which can magnify the workload and incur high costs over several years after the initial procedure.

MDCT of endoleaks following endovascular repair of abdominal aortic aneurysms

Endovascular aneurysm repair has been used to repair abdominal aortic aneurysms but necessitates surveillance to diagnose the delayed possibility of endoleak formation. Multi-detector computer tomography (MDCT) of the abdomen is one imaging technique used to diagnose enlargement of the aneurysm sac that may be indicative of endoleaks. MDCT has a role in identifying the initial endoleak formation and providing signs suggestive of the specific endoleak subtype; thus it is necessary for radiologists to be familiar with the findings of endoleak seen on MDCT. In this pictorial review, we explore the various types of endoleaks and their appearance on MDCT.

Endotension-related aortic sac rupture treated by endograft relining

Endovascular aortic aneurysm repair is an effective alternative to open surgical repair in high risk patient. Endotension is an unpredictable late and rare complication of EVAR. Clinical significance and choice of technique for treatment are controversial. At present, there are no cases of endotension-related aneurysmal sac rupture reported in literature, altough it is frequently associated with late surgical conversion. In this case report is described a case of a patient treated with a first generation Gore Excluder(TM) endograft for abdominal aortic aneurysm, with late aneurysmal sac enlargement without evidence of endoleak and subsequent contained rupture without anemia and shock. We have successfully treated the patient by endovascular procedure, through bilateral percutaneous femoral approach, with relining technique. Three years CT scan follow-up showed the endograft patency and size sac reduction.

Endotension: rupture of abdominal aortic aneurysm

Aortic endovascular exclusion technique called 'chimney' consists of placing stents through abdominal aortic visceral branches and a prosthesis that excludes the thoraco-abdominal aneurysm. Stents and an aortic endoprosthesis are placed in the renal arteries. This method is primarily used when open surgery is too risky. The mechanism that provides aneurysm sac increase without the visible presence of endoleaks has not been fully elucidated. The expansion of the aneurysm sac, due to endotension, is difficult to diagnose, even with the use of advanced imaging tests. Its diagnosis is made by exclusion. We present a case of a late complication in a high-risk patient after a 'chimney' endovascular procedure. Following the surgery, the patient presented a ruptured aneurysm sac without a visible endoleak. A second intervention was not feasible due to the high risk of occluding all of the branches, and complicated by previous 'chimney'. Endotension is a possible cause of aneurysm rupture and death.

Challenging treatment of multiple late complications after endovascular aneurysm repair

BACKGROUND

To report a case of multiple additional procedures after successful endovascular treatment of abdominal aortic aneurysm.

METHODS

An endovascular abdominal aortic aneurysm repair with a bifurcated aortic Vanguard endograft successfully performed in 1999 resulted in multiple complications, including endoleaks and a row separation, treated endovascularly. Subsequently, tuberculosis sepsis and prosthesis infection resulted in long-term antibiotic treatment. Additional graft leaks, aneurysm sack growth, and sack ruptures were also treated endovascularly because the patient consistently denied open repair. Endovascular procedures, however, did not solve the problem, turning to be increasingly challenging. The patient finally approved open graft removal and aortobifemoral reconstruction that were successfully performed 11 years after the initial endograft implantation.

RESULTS

The patient has recovered from surgery well and is asymptomatic. No evidence of bacterial colonization was found according to the specimen taken during the laparotomy.

CONCLUSION

Vanguard and other first-generation aortic endografts are associated with high incidence of complications and reinterventions. Open surgery is a method of choice in similar cases.

Management of Endoleaks following Endovascular Aneurysm Repair

Endovascular aneurysm repair (EVAR) has emerged as a viable alternative to open repair for abdominal aortic aneurysms. Endoleaks are a complication unique to EVAR and can occur in up to 25% of patients. In this article, the management of endoleaks following EVAR will be discussed.

A multidetector tomography protocol for follow-up of endovascular aortic aneurysm repair

OBJECTIVE

The purpose of this study was to improve the use of 64-channel multidetector computed tomography using lower doses of ionizing radiation during follow-up procedures in a series of patients with endovascular aortic aneurysm repair.

METHODS

Thirty patients receiving 5 to 29 months of follow-up after endovascular aortic aneurysm repair were analyzed using a 64-channel multidetector computed tomography device by an exam that included pre-and postcontrast with both arterial and venous phases. Leak presence and type were classified based on the exam phase.

RESULTS

Endoleaks were identified in 8/30 of cases; the endoleaks in 3/8 of these cases were not visible in the arterial phases of the exams.

CONCLUSION

The authors conclude that multidetector computed tomography with pre-contrast and venous phases should be a part of the ongoing follow-up of patients undergoing endovascular aortic aneurysm repair. The arterial phase can be excluded when the aneurism is stable or regresses. These findings permit a lower radiation dose without jeopardizing the correct diagnosis of an endoleak.

AAA stent-grafts: past problems and future prospects

Endovascular aneurysm repair (EVAR) has quickly gained popularity for infrarenal abdominal aortic aneurysm repair during the last two decades. The improvement of available EVAR devices is critical for the advancement of patient care in vascular surgery. Problems are still associated with the grafts, many of which can necessitate the conversion of the patient to open repair, or even result in rupture of the aneurysm. This review attempts to address these problems, by highlighting why they occur and what the failings of the currently available stent grafts are, respectively. In addition, the review gives critical appraisal as to the novel methods required for dealing with these problems and identifies the new generation of stent grafts that are being or need to be designed and constructed in order to overcome the issues that are associated with the existing first- and second-generation devices.

Fluid-structure interaction of a patient-specific abdominal aortic aneurysm treated with an endovascular stent-graft

Background

Abdominal aortic aneurysms (AAA) are local dilatations of the infrarenal aorta. If left untreated they may rupture and lead to death. One form of treatment is the minimally invasive insertion of a stent-graft into the aneurysm. Despite this effective treatment aneurysms may occasionally continue to expand and this may eventually result in post-operative rupture of the aneurysm. Fluid-structure interaction (FSI) is a particularly useful tool for investigating aneurysm biomechanics as both the wall stresses and fluid forces can be examined.

Methods

Pre-op, Post-op and Follow-up models were reconstructed from CT scans of a single patient and FSI simulations were performed on each model. The FSI approach involved coupling Abaqus and Fluent via a third-party software - MpCCI. Aneurysm wall stress and compliance were investigated as well as the drag force acting on the stent-graft.

Results

Aneurysm wall stress was reduced from 0.38 MPa before surgery to a value of 0.03 MPa after insertion of the stent-graft. Higher stresses were seen in the aneurysm neck and iliac legs post-operatively. The compliance of the aneurysm was also reduced post-operatively. The peak Post-op axial drag force was found to be 4.85 N. This increased to 6.37 N in the Follow-up model.

Conclusion

In a patient-specific case peak aneurysm wall stress was reduced by 92%. Such a reduction in aneurysm wall stress may lead to shrinkage of the aneurysm over time. Hence, post-operative stress patterns may help in determining the likelihood of aneurysm shrinkage post EVAR. Post-operative remodelling of the aneurysm may lead to increased drag forces.

Original Excluder component overlap from proximal or distal extension during initial repair not correlated with aneurysm sac shrinkage

OBJECTIVES

The original abdominal Excluder (W.L. Gore & Associates, Flagstaff, Ariz) endoprosthesis has been associated with late aneurysm sac expansion over time from transgraft ultrafiltration of serous fluid. This has been treated by relining the graft with original or low-permeability components. We asked whether additional component overlap of the original graft material resulting from proximal or distal extensions placed at the time of initial repair would influence the rate of late aneurysm sac expansion in the absence of endoleak.

METHODS

Computed tomography (CT) scans from subjects (n = 120) receiving the original endoprosthesis from the Excluder pivotal trial were measured for total distance of original graft overlap (including contralateral gate, proximal extension, or distal extension overlap) based on reformatted CT scans. This was compared to change in aneurysm sac diameter and volume (as measured in independent laboratories) at the latest time point available. Patients were omitted if they were missing CT scan data (n = 10), their graft was explanted for endoleak (n = 2), they underwent an intervention for endoleak and did not have diameters available after their intervention (n = 3), or if they had a continued endoleak that could account for an increase in aneurysm sac diameter (n = 11). This left 27 patients with more overlapping components than the required contralateral limb/gate overlap (mean follow-up time 40.6 +/- 17.0 months) and 67 patients with required gate overlap (mean follow-up time 46.2 +/- 15.9 months).

RESULTS

Subjects with increased component overlap (mean overlap 87.1 mm +/- 57.4 mm) were not protected from aneurysm sac expansion when compared to those with the minimum required gate overlap (mean overlap 31.2 mm +/- 3.4 mm). There was no association of total distance of overlap with aneurysm sac size change by diameter or volume (r(2) = 0.00034, P = .86 for diameter and r(2) = 0.0019, P = .68 for volume). Increasing percentage of overlap within the aneurysm sac was likewise not associated with aneurysm sac decrease in diameter (r(2) = 0.0028, P = .61). Few patients had large percentages of original graft overlap (mean 26.2% +/- 14.1% for the increased overlap group and 18.6% +/- 5.5% for the required overlap group, P = .0097).

CONCLUSION

Partial graft overlap involving multiple original components from proximal and distal extensions is not protective against aneurysm sac expansion due to transgraft ultrafiltration. This suggests that transgraft ultrafiltration is not impeded by having partial double layers of original material. All patients who received the original Excluder and have late aneurysm sac expansion in the absence of endoleak should have as complete relining as feasible with low permeability components if sac shrinkage is the surrogate goal.

Symptomatic aneurysm rupture without bleeding secondary to endotension 4 years after endovascular repair of an abdominal aortic aneurysm

PURPOSE

To demonstrate the absence of bleeding from a ruptured abdominal aortic aneurysm (AAA) without evidence of endoleak following endovascular aneurysm repair (EVAR).

CASE REPORT

A 72-year-old woman developed aneurysm enlargement 4 years after EVAR of an infrarenal AAA. During surgical exploration for abdominal pain and presumed aneurysm rupture, the ruptured aneurysm sac was found to be filled with gelatinous material without evidence of thrombus or active bleeding.

CONCLUSION

This case provides insight into the natural history of endotension and indicates that conservative management even in the face of an expanding aneurysm is a valid management option for selected patients.

Secondary Endovascular and Conversion Procedures for Failed Endovascular Abdominal Aortic Aneurysm Repair: Can We Still Be Optimistic?

The purpose of this study was to evaluate the incidence, etiology, and outcome of secondary endovascular and “open” conversion procedures after failed endovascular abdominal aortic aneurysm repair (EVAR). From January 1997 until December 2005, 625 patients with an infrarenal abdominal aortic aneurysm were treated by elective EVAR, with 98.7% ( n = 617) primary EVAR success. The mean follow-up of the 617 patients was 46.7 ± 11.2 months. One hundred of these patients (16.2%) required secondary endovascular or peripheral procedures, and 39 (6.3%) patients underwent a secondary abdominal conversion. There were 5 acute conversions (0.8%) and 34 elective conversions (5.5%). The pre-EVAR anatomic suitability data, the main cause of the secondary procedure, and stent graft type were compared between patients with primary EVAR success, patients in need of a secondary endovascular or peripheral procedure, and patients with abdominal conversion. The overall main causes for reinterventions were proximal migration ( n = 60; 9.7%), progressive kinking of the stent graft ( n = 59; 9.6%), and late type III endoleak ( n = 12; 1.9%). Multivariate logistic regression analysis showed that factors significantly correlated with secondary procedures were the abdominal aortic aneurysm's maximum diameter, the proximal neck's width and length, and particularly the commercial withdrawal of the stent graft ( p < .001). The morbidity and mortality rates of secondary endovascular or peripheral interventions were 0%. The mortality rate of acute secondary conversions was 20% ( n = 1) and of elective secondary conversions was 8.8% ( n = 3). The morbidity rates for acute and elective conversions were 0% and 65%, respectively. The aneurysm-related mortality rate in our series was below 1%. Abdominal conversion surgery still carries a high mortality rate, but the overall EVAR-related mortality rate remains low. Early pitfall detection and proper reintervention are crucial to long-term EVAR success.

Endotension following endovascular aneurysm repair

Abstract

Endovascular aneurysm repair (EVAR) is a new and minimally invasive alternative to open repair for patients with abdominal aortic aneurysm (AAA). Soon after its introduction in 1990, it was recognized that EVAR had potential and distinct advantages in the elective and emergency settings. However, long-term follow-up has shown enlargement of the AAA in a substantial percentage of patients who underwent EVAR with the original-permeability Excluder. Of interest is that sac expansion frequently occurs in the absence of endoleak, often referred to as endotension. The pathophysiology of endoleak is beginning to be elucidated and its management is ready to be established, while controversy still exists about the etiology and clinical consequences of endotension. Fortunately, the incidence of endotension is decreasing and it appears that AAA expansion after EVAR with the original Excluder can be arrested by endovascular relining with a low-permeability Excluder endoprosthesis. The aim of this brief review is to provide historical perspective and a good understanding of the etiology, diagnosis, and management of endotension.

Successful treatment of endotension and aneurysm sac enlargement with endovascular stent graft reinforcement

Abdominal aortic aneurysm (AAA) enlarges after successful endovascular repair because of endoleak, which is persistent blood flow within the aneurysm sac. In the absence of detectable endoleak, AAA may still expand, in part because of endotension, which is persistent pressurization within the excluded aneurysm. We report three patients who underwent successful endovascular AAA repair using the Excluder device (W. L. Gore & Associates, Flagstaff, Ariz). Although their postoperative surveillance showed an initial aneurysm regression, delayed aneurysm enlargement developed in all three, apparently due to endotension. Endovascular treatment was performed in which endograft reinforcement with a combination of aortic cuff and iliac endograft extenders were inserted in the previously implanted stent grafts. The endograft reinforcement procedure successfully resulted in aneurysm sac regression in all three patients. Our study underscores the significance of increased graft permeability as a mechanism of endotension and delayed aneurysm enlargement after successful endovascular AAA repair. In addition, our cases illustrate the feasibility and efficacy of an endovascular treatment strategy when endotension and aneurysm sac enlargement develops after endovascular AAA repair.

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.

Five-year report of a multicenter controlled clinical trial of open versus endovascular treatment of abdominal aortic aneurysms

OBJECTIVE

Compare long-term results of endovascular treatment and standard open repair of abdominal aortic aneurysms in a multicenter, concurrent-controlled trial.

METHODS

334 subjects were treated with standard open repair (control, n = 99) or the original EXCLUDER Bifurcated Endoprosthesis (test, n = 235). Five-year clinical evaluations and corelab radiographic results are analyzed.

RESULTS

Overall and aneurysm-related survival are similar. There have been ten open conversions, most frequently for enlarging sacs without endoleak. Two patients died after conversion. Including reinterventions and complications of reinterventions as adverse events, there is significant, persistent long-term reduction in major adverse events. At 5 years, corelab reported 0% limb narrowing, 0% trunk migration, 0% component (contralateral leg, aortic extender, and iliac extender) migration, 0% fracture, endoleak in 3% (2 type II/68), and aneurysm growth (>5 mm compared to baseline) in 38% (30/78) of the test group. There are no aneurysm ruptures in either test or control group.

CONCLUSIONS

After 5 years follow-up, endovascular repair is a safer and effective treatment compared with open surgical repair for abdominal aortic aneurysms. Major adverse events are less frequent with the endograft despite the need for late reinterventions. Aneurysm expansion is observed in nearly two-fifths of patients but is not associated with endoleak or aneurysm rupture. Multicenter clinical trials are evaluating a newer version of this device designed to avoid this high rate of sac expansion.

The effect of endograft relining on sac expansion after endovascular aneurysm repair with the original-permeability Gore Excluder abdominal aortic aneurysm endoprosthesis

OBJECTIVE

Endovascular abdominal aortic aneurysm repair (EVAR) with the original-permeability Excluder (W.L. Gore & Associates, Flagstaff, Ariz) has been associated with postoperative sac expansion in the absence of endoleak. In these cases, we have performed an endovascular revision, relining the original endograft with another Excluder, in an effort to arrest sac expansion by reducing permeability. We have studied these cases to determine the effect of relining on aneurysm expansion.

METHODS

Patients who demonstrated sac expansion (>or=5 mm diameter, >or=5% three-dimensional volume) after EVAR with the original Excluder were evaluated. Between 1999 and 2004, the original-permeability endoprosthesis was used in 97 patients who underwent EVAR for asymptomatic abdominal aortic aneurysm (AAA). Sac expansion occurred in 24 patients, of which multiple imaging modalities showed 12 had expansion without demonstrable endoleak. Nine of the 12 have had endovascular relining, and five of these nine have >6 months follow-up to form the primary basis for this report.

RESULTS

AAA size was stable or smaller in the first 6 months after the original EVAR for all patients. Once expansion began (typically in the time frame of 6 to 12 months), multimodality imaging showed no aneurysm spontaneously decreased in size without intervention, despite the absence of endoleak (n = 12). Expansion exceeded clinically significant thresholds at 30 months (mean) by diameter criteria and 22 months (mean) by three-dimensional volume criteria for the five patients with >6 months follow-up after relining. Endovascular relining was performed at a mean of 36 months, with a mean hospital stay of 1 day, and no morbidity or mortality. Over the entire duration of expansion (mean, 26 months), aneurysms expanded by 6.0 +/- 1 mm/year diameter and by 12% +/- 2%/year by three-dimensional volume. At a mean of 16 months follow-up after relining with another Excluder, the mean diameter decrease was 2.0 mm/year (P < .03) and the mean volume decrease was 2.6%/year (P < .01). After relining, all AAAs were smaller by diameter or volume, or both, exceeding thresholds defining shrinkage in two of the five with >6 months follow-up after relining. There was no rupture, migration, endoleak, conversion to open repair, or aneurysm-related death in any patient.

CONCLUSIONS

It appears from the initial follow-up that AAA expansion owing to permeability issues after EVAR with the original Excluder can be arrested by endovascular relining with a low-permeability Excluder endoprosthesis.

Endovascular conversion with femorofemoral bypass as a treatment of endotension and aneurysm sac enlargement

We report a case of a patient treated with a Gore Excluder endograft for AAA in November 2003 with subsequent aneurysm sac enlargement in the absence of an identified endoleak. The patient had a Type I endoleak treated with a Palmaz stent at the neck and later developed a Type II endoleak treated with translumbar coil embolization. This was successful with absence of pressure in the sac after the procedure and stable aneurysm size over the next nine months. Surveillance of the patient with both CT and ultrasound then revealed an increase in the aortic sac diameter in the absence of endoleak. A Cook Zenith converter was used to reline this PTFE endograft. Subsequently, imaging showed aneurysm sac shrinkage. This is a report of endotension with aneurysm expansion following Gore Excluder placement which was treated successfully with a dacron endograft.

Outcomes of original and low-permeability Gore Excluder endoprosthesis for endovascular abdominal aortic aneurysm repair

OBJECTIVE

Because of concern about the percentage of enlarging abdominal aortic aneurysms (AAAs) after endovascular repair with the Excluder device (W.L. Gore & Assoc, Inc, Sunnyvale, Calif), the graft material was modified to reduce its permeability and released for commercial use in mid-2004. We studied all AAA repairs with Excluder endografts performed at our institution, including the original-permeability (OP) version (n = 99) and the low-permeability (LP) version (n = 48).

METHODS

All patients were followed up with serial computed tomography (CT) angiography and three-dimensional (3D) reconstruction. Morphologic measurements, including AAA diameter and 3D volume, were prospectively entered into a database to evaluate changes in AAA size over time. Owing to the length of available follow-up for the LP version, the primary end point was AAA size change at 6 and 12 months, evaluated by Mann-Whitney U test for unpaired samples.

RESULTS

Preoperative and postoperative anatomy was similar in the two groups, including AAA diameter (OP, 5.6 +/- 1 cm; LP, 5.8 +/- 2 cm; P = .3), aortic neck length (OP, 21 +/- 1 mm; LP, 22 +/- 2 mm; P = .9), postoperative aortic seal zone (OP, 18 +/- 1 mm; LP, 16 +/- 1 mm, P > .1) and iliac seal zone (OP, 33 +/- 1 mm, LP 31 +/- 1 mm, P = .2). The rate of sac shrinkage differed significantly. Orthogonal diameter measurements showed a significant difference in the rate of shrinkage by 12 months postoperatively (OP, -2.1 +/- 1 mm; LP, -5.1 +/- 1 mm; P = .01). By 3D volume, the rate of shrinkage was considerably different between the two groups at both 6 and 12 months (12 months: OP, -6% +/- 1%; LP, -20 +/- 4%; P = .0006). There was no enlargement by diameter in either group at 6 or 12 months postoperative. By standard volume criteria, however, 12 of 99 patients in the OP group and one of 48 patients in the LP group had significant AAA enlargement < or =12 months (P = .04). Of these, four of 12 patients in the OP group had enlargement without apparent endoleak, even on delayed-contrast CT. The remainder had persistent type II endoleaks (8/12 in the OP group and 1/1 in the LP group). Multivariate analysis revealed graft permeability (P < .0001) and endoleak (P < .0001) as independent factors in aneurysm size change. In the OP group long-term, the average AAA enlarged at later time points compared with the prior scan: 24 months, -0.2%; 36 months, +0.2%; 48 months, +2%; and 60 months, +2% (P < .0002).

CONCLUSIONS

In early follow-up, the low-permeability Excluder device is associated with a significantly greater aneurysm shrinkage rate than the original version. Clinically important enlargement also appears significantly different within 1 year of implantation. Despite these promising results, longer follow-up is needed to determine whether these differences will persist.

Sac Hygroma After Endovascular Abdominal Aortic Aneurysm Repair: Successful Treatment with Endograft Relining

Aneurysm sac expansion following endovascular abdominal aortic aneurysm repair (EVAR) is typically associated with endoleaks that can be readily diagnosed on computed tomographic angiography (CTA), ultrasound, or catheter-directed arteriography. Sac hygromas are a cause of sac expansion without apparent endoleak and are presumed to be a result of ultrafiltration of serum manifested by accumulation of fibrinous, gelatinous material within the aneurysm sac following EVAR. Although there are no reported associated ruptures, sac expansion is nevertheless disconcerting and intervention is presumably indicated. We report a case of an expanding aneurysm after EVAR secondary to sac hygroma that was successfully treated with relining of the existing, original endograft.

Detection of Endoleaks after Endovascular Aneurysm Repair with Use of Technetium-99m Sulfur Colloid and 99m Tc-labeled Red Blood Cell Scans

PURPOSE

This study was performed to determine whether endoleaks could be detected after endovascular aneurysm repair (EVAR) with use of technetium-99m sulfur colloid and (99m)Tc-labeled red blood cell (RBC) nuclear medicine scans.

MATERIALS AND METHODS

There were 13 patients enrolled in this study: nine with endoleaks seen on computed tomographic (CT) angiography and four with no endoleak on CT angiography. All patients underwent regularly scheduled surveillance CT angiography examination after EVAR to evaluate for endoleak. Endoleak detection was then attempted in each patient with two nuclear medicine scans: a (99m)Tc sulfur colloid scan and a (99m)Tc-labeled RBC scan. Flow images (5 seconds per frame) were obtained for 1 minute after intravenous administration of 555 MBq (15 mCi) (99m)Tc sulfur colloid. Sequential dynamic images were then obtained every minute for 30 minutes. Next, a (99m)Tc-labeled RBC study was performed after the intravenous administration of 370-1,073 MBq (10-29 mCi) in vitro labeled (99m)Tc RBCs. Flow images were obtained, followed by sequential dynamic images obtained every minute for 30 minutes. Single photon emission CT images of the abdomen were then acquired. The nuclear medicine scans were evaluated for the presence or absence of endoleak independent of the CT angiography findings.

RESULTS

Of the nine patients with endoleaks on CT angiography, seven (78%) had them detected by nuclear medicine examinations. Two of the nine endoleaks seen on CT angiography (22%) were not seen on either scintigraphic examination. All patients with no endoleak on CT angiography had their nuclear medicine scans correctly interpreted as showing no endoleak present (n = 4; 100%). No complications occurred as a result of the nuclear medicine scans.

CONCLUSIONS

Endoleaks can be detected with (99m)Tc sulfur colloid and (99m)Tc-labeled RBC nuclear medicine scans. This initial work suggests that the sensitivities of these scintigraphic scanning methods for endoleak detection are lower than that of CT angiography.

Three-dimensional analysis of enlarging aneurysms after endovascular abdominal aortic aneurysm repair in the Gore Excluder Pivotal clinical trial

OBJECTIVE

Recent reports have raised concern about the percentage of enlarging abdominal aortic aneurysms (AAAs) after endovascular repair with the Gore Excluder device. As part of the investigation into this issue, a morphologic analysis was performed on enlarging aneurysms in the Excluder Pivotal clinical trial.

METHODS

Computed tomographic scans were evaluated on all patients identified with enlarging aneurysms (5-mm increase by Core laboratory or site) and at least 4 years of follow-up in the Excluder Pivotal clinical trial. Three-dimensional reconstruction, a set of 24 standard morphologic measurements, and analysis of potential enlargement mechanisms were performed.

RESULTS

Of 112 trial patients with 4 years of follow-up, 38 AAAs (34%) were identified as enlarging. Data were obtained from 196 computed tomographic scans (the mean interval was 47 months from first to last scan). Of the 158 scans with a prior scan for comparison, 41% demonstrated growth relative to the initial scan by diameter criteria, but 79% demonstrated growth relative to the initial scan by 3-dimensional volume criteria (P < .0001 vs diameter; chi2 analysis). This difference was most evident at early time points: at 1 year, diameter criteria indicated that 8% of these AAAs were enlarging, but 56% were already enlarging by volume criteria. On average, enlargement was detected by volume 18 months before it was detected by diameter (P < .0001), and at a smaller diameter (55 +/- 1 mm vs 60 +/- 1 mm; P < .0001). Only 19% of scans (39% of patients) had apparent endoleaks. Scans with apparent endoleaks demonstrated a greater interval rate of growth as compared with those without apparent endoleak (3.6 +/- 0.8 mm vs 1.9 +/- 0.3 mm [P < .02] by diameter; 23 +/- 4 cm3 vs 11 +/- 1 cm3 [P < .001] by volume). Although the etiology of enlargement may be endotension or device permeability in up to 74% of patients, other potential causes of aneurysm enlargement included neck apposition length less than 15 mm (15 patients; 39%), large aortic diameter relative to device (18%), large iliac diameter (5%), and iliac apposition length less than 15 mm (20%). Multiple potential etiologies of enlargement were present in 53% of AAAs.

CONCLUSIONS

The etiology of aneurysm enlargement in the Excluder Pivotal trial is likely multifactorial, including endoleak, inadequate attachment site length, and endotension or device permeability. Even by conservative criteria, a substantial percentage of aneurysm growth with the original device is likely due to material permeability. Three-dimensional volume criteria detected aneurysm enlargement more frequently, at a smaller diameter, and on average 18 months sooner than standard diameter criteria, thus suggesting a role in further investigation of this issue.