Endoleak after endovascular graft repair of experimental aortic aneurysms: does coil embolization with angiographic "seal" lower intraaneurysmal pressure?

3D finite-element modeling of vascular adaptation after endovascular aneurysm repair

Aneurysm shrinkage is clinically observed after successful endovascular aortic aneurysm repair (EVAR). However, global understanding of post-operative aneurysm evolutions remains weak. In this work, we propose to study these effects using numerical simulation. We set up a 3D finite-element model of post-EVAR vascular adaptation within an open-source finite-element code, which was initially developed for growth and remodeling (G&R). We modeled the endograft with a set of uniaxial prestrained springs that apply radial forces on the inner surface of the artery. Constitutive equations, momentum balance equations, and equations related to the mechanobiology of the artery were formulated based on the homogenized constrained mixture theory. We performed a sensitivity analysis by varying different selected parameters, namely oversizing and compliance of the stent-graft, gain parameters related to collagen G&R, and the residual pressure in the aneurysm sac. This permitted us to evaluate how each factor influences post-EVAR vascular adaptation. It was found that oversizing, compliance or gain parameters have a limited influence compared to that of the residual pressure in the aneurysm sac, which was found to play a critical role in the stability of aneurysm after stent-graft implantation. An excessive residual pressure larger than 50 mmHg can induce a continuous expansion of the aneurysm while a moderate residual pressure below this critical threshold yields continuous shrinkage of the aneurysm. Moreover, it was found that elderly patients, with relatively lower amounts of remnant elastin in the arterial wall, are more sensitive to the effect of residual pressure. Therefore, these results show that elderly patients may present a higher potential risk of aortic sac expansion due to intra-aneurysm sac pressure after EVAR than younger patients.

Endotension: twenty years of a controversial term

Use of the term endotension in the treatment of aortic aneurysm is currently controversial. Initially it was proposed to define the circumstance in which there is an enlargement of the aneurysm sac after endovascular repair without a demonstrable endoleak. The term was established with the aim of transmitting the possibility of causes other than pressure applying stress to the aneurysm wall. Twenty years have passed since the proposal of this terminology was published. The literature is reviewed with the purpose of providing an update on advances in the knowledge of the possible etiological mechanisms. The experimental studies call into question that causes other than pressure determine the increase of the aneurysm. On the basis of this review, the term `Sac Expansion Without Evident Leak´ (SEWEL) is proposed as a more accurate and precise denomination for what is aimed to be defined. Evidence suggests that the more likely mechanisms of persistent pressurization of the aneurysm sac are an unidentified endoleak (likely type I or low-flow Type II) or thrombus occluding wide and short channels that connects with the excluded aneurysm sac (at the attachment sites of the stent-graft or at the branch vessels orifices).

Basic Science Review: Characterization of Endoleak Following Endovascular Repair of Abdominal Aortic Aneurysms

Aneurysm models have been developed to study the pathobiology of abdominal aortic aneurysm and to evaluate the efficacy of endovascular therapy. The purpose of this review is to describe the use and limitations of current animal and experimental models for the characterization of endoleak following endovascular repair of abdominal aortic aneurysms.

Endotension in the Closed Aneurysm Sac during Aortic and Iliac Cross Clamping: Implications of Pressure and Flow Measurements

Purpose:

To relate the mean and pulse pressures in the cross-clamped aortic aneurysm sac to the systemic pressures during open repair (OR) of abdominal aortic aneurysm (AAA). To correlate the intrasac pressures to the number of bleeding lumbar arteries (LA) and the flow pattern of the inferior mesenteric artery (IMA).

Methods:

In a prospective study of 55 patients (45 men; median age 69 years, range 47–84) undergoing open repair, the IMA flow and the mean pressure in the aneurysm sac (ASPmean) were measured before and after aortic and iliac artery cross clamping. The systemic mean pressure (SPmean) was recorded simultaneously. The aneurysm sac (ASPpulse) and systemic pulse pressures (SPpulse) were calculated, as were the mean pressure ratio (ASPmean/SPmean) and the pulse pressure ratio (ASPpulse/SPpulse). Values are given as the median (range).

Results:

Cross clamping of the proximal aortic neck significantly reduced the mean pressure to 31 mmHg (14–64), with a pressure ratio of 0.39±0.14; the pulse pressure decreased to 0 mmHg (0–13) (p<0.001). Additional cross clamping of the iliac arteries did not alter the pressure levels any further. In the patent IMA (n = 23), an orthograde median flow of 43 mL/min (2–135) was measured; sequential cross clamping of the aorta and iliac arteries reduced the flow to −6 mL/min (–130 to +21) and −3 mL/min (–120 to +22), respectively. There was no correlation between the pressure ratio and IMA patency, its volume flow, or the number of backbleeding lumbar arteries.

Conclusions:

The aneurysm sac is still pressurized with no pulsatility after cross clamping during open AAA repair. The aneurysm mean and pulse pressures did not correlate to the number of backbleeding lumbar arteries. Finally, the pressure ratios did not correlate to the highly variable IMA flow pattern during aortic cross clamping.

Type III and Type IV Endoleak: Toward a Complete Definition of Blood Flow in the Sac after Endoluminal AAA Repair

In this document the authors continue to refine their seminal categorization of endoleak, a major complication of endovascular aneurysm repair. In addition to type I (related to the graft device itself) and type II (retrograde flow from collateral branches) endoleak, they propose two new categories: endoleak due to fabric tears, graft disconnection, or disintegration would be classified type III, and flow through the graft presumed to be associated with graft wall “porosity” would be categorized as type IV endoleak.

Internal Iliac Artery Occlusion Using a Stent-Graft Tunnel during Endovascular Aneurysm Repair: A New Alternative to Coil Embolization

Purpose:

To report a new endovascular technique for internal iliac artery (IIA) occlusion during stent-graft treatment in patients with aortoiliac aneurysm.

Technique:

Stent-grafts measuring 20 to 28 mm in diameter and 37.5 mm long were deployed at the iliac bifurcation to occlude the IIA at its origin. Subsequent deployment of an aortic bifurcation endograft with ipsilateral extension into the external iliac artery was through this iliac stent-graft tunnel. This approach has been used in 5 patients with abdominal aortic aneurysm and common iliac artery aneurysm (n = 4) or isolated iliac artery aneurysm. Proximal IIA occlusion was achieved in all cases with no distal type I endoleak. IIA patency on the side opposite to the tunnel procedure was preserved in each case. No patient described new onset of pelvic ischemic symptoms. Over a mean 10-month follow-up (range 1–12), there was no secondary procedure required for type I endoleak. Three patients had a CIA aneurysm diameter change of −1, −4, and 0 mm at 1 year.

Conclusions:

This new method for IIA occlusion at its origin without coil embolization may prove to be a useful adjunct to endovascular aortoiliac aneurysm repair. The technique is simple, rapid, and may minimize the risk of pelvic ischemia.

Endotension is Influenced by Aneurysm Volume: Experimental Findings

Purpose:

To investigate in an in vitro model whether and to what extent pressure is influenced by aneurysm size.

Methods:

Latex aneurysms of 3 different volumes (24, 30, and 81 mL) were inserted into an in vitro circulation model. The systemic mean pressure (SPmean) was varied from 50 to 120 mmHg. The aneurysms were excluded using a woven polyethylene graft. Aneurysm sac mean pressure (ASPmean) was measured.

Results:

In the in vitro model, endovascular aneurysm repair created a closed chamber without endoleak but showed a relevant aneurysm sac pressure. At an SPmean of 80 mmHg, the ASPmean was 42.0 ± 0.6 mmHg in the 24-mL aneurysm, 40.5 ± 0.5 mmHg in the 30-mL model, and 19.3 ± 0.5 mmHg in the 81-mL aneurysm (p < 0.05). The ASPmean rose with increasing SPmean and was inversely dependent on the aneurysm volume.

Conclusions:

This in vitro model demonstrated that the sac mean pressure correlated to the systemic pressure and that a greater aneurysm volume reduced aneurysm sac pressure. These data highlight the need for further studies regarding endotension.

Endovascular AAA Repair: Prevention of Side Branch Endoleaks with Thrombogenic Sponge

Purpose:

To report a technique that might decrease the incidence of lumbar artery endoleaks following endovascular repair (EVR) of abdominal aortic aneurysms (AAAs).

Methods:

Ninety-three patients (86 males, median age 72 years, range 56 to 88) undergoing EVR with the aortomonoiliac technique were entered into a study to detect and then occlude patent side branches before completion of the endografting procedure. Prior to deploying the iliac occluder, an aneurysmogram was performed to detect patent aortic side branches. If these side branches were found, an absorbable gelatin sponge was inserted into the aneurysm sac via the occluder introducer sheath. The patients were followed with contrast-enhanced spiral computed tomography (CT) at 1 week and 3, 6, and 12 months to detect the presence of endoleaks.

Results:

Forty-eight (52%) patients demonstrated patent side branches that were occluded by the insertion of gelatin sponges into the aneurysm sac. The remaining 45 patients without evidence of side branch flow were untreated. Ten (10.7%) patients died in the perioperative period, and 15 (16.1%) primary endoleaks (13 proximal, 2 distal) were detected. This left 68 (73.1%) patients for follow-up, 33 (48.5%) of whom had patent branch vessels treated with the thrombogenic sponge. The median follow-up was 4 months (range 1 to 17), during which time no side branch endoleak was detected on surveillance CT scans in any of the 68 patients, which included all patients treated with the thrombogenic sponge technique and those in whom no patent side branches had been identified.

Conclusions:

We have demonstrated a safe and reliable method of preventing lumbar artery endoleaks following endovascular AAA repair.

Endovascular Repair of Aortic Aneurysms: Treatment of Complications

Purpose:

To evaluate the use of interventional procedures for treating complications following endovascular repair of aortic aneurysms.

Methods:

Fifty-five patients (49 men; mean age 67.5 years) underwent endoluminal stent-graft repair of traumatic (n = 4) or arteriosclerotic (n = 51) aortic aneurysms in the thoracic (n = 3) or infrarenal (n = 52) aorta. Follow-up of therapeutic success included periodic clinical examination, angiography, and spiral computed tomography.

Results:

Discounting the 25 (45%) cases of postimplantation syndrome that did not require treatment, there were 22 complications observed in 20 (36%) patients over a mean 10-month follow-up (range 1 to 27). There were 2 transrenal endograft maldeployments, 1 case of twisted graft limbs, 2 access site problems (1 patient), 12 endoleaks (11 patients), 1 late graft limb thrombosis, 1 symptomatic internal iliac artery occlusion, 2 myocardial infarctions, and 1 transient psychosis. Seven (13%) patients did not undergo specific therapy, while 4 (7%) required operation (2 crossover bypass grafts, 1 suture revision, and 1 graft replacement). Among 9 (16%) patients treated with interventional techniques, 7 underwent percutaneous coil embolization for 8 endoleaks (7 successfully resolved). One late stent-graft disconnection required an additional stent-graft, and 1 of the 2 malpositioned endografts was repositioned. All patients remain alive with no increase in the diameter of the aneurysm in any patient.

Conclusions:

Technical problems resulting from the endovascular repair of aortic aneurysms often respond to interventional treatment.

Endotension: An Explanation for Continued AAA Growth after Successful Endoluminal Repair

Purpose:

To present and analyze several cases that illustrate persistent sac pressurization following endovascular abdominal aortic aneurysm (AAA) repair.

Methods and Results:

Four patients with successful endovascular AAA exclusion presented in follow-up with an expanding aneurysm. Two had initial sac diameter decrease, but by 18 and 24 months, respectively, the AAA had enlarged and become pulsatile. There was no endoleak evident, but the proximal attachment stents had migrated distally in both cases. One patient developed endoleak with aneurysm expansion at 6 months; contained rupture occurred at 12 months. The last case had slowly evolving aneurysm expansion over 36 months but no endoleak. All endografts were removed and successfully replaced with conventional grafts. Intrasac thrombus was implicated as the means of pressure transmission that precipitated AAA expansion in these cases.

Conclusions:

Excluded AAAs can increase in size owing to persistent or recurrent pressurization (endotension) of the sac even when there is no evidence of endoleak. One proposed mechanism is pressure transmission via thrombus that lines the attachment site. Endotension may also represent an indiscernible, very low flow endoleak that allows blood to clot at the source of leakage.

Modelos animais de aneurisma de aorta

Os modelos experimentais em animais vêm sendo utilizados em cirurgia vascular há décadas. O desenvolvimento de novas técnicas para tratamento endovascular dos aneurismas requer a criação de bons modelos experimentais para testar esses dispositivos e estudar seu impacto sobre a progressão da doença. Este artigo tem por objetivo revisar os modelos de aneurisma arterial descritos atualmente. Entre os diversos modelos descritos, nenhum reúne todas as características de um modelo ideal de aneurisma. Os modelos em animais de grande porte são adequados para treino, estudo de alterações em parâmetros fisiológicos durante e após a liberação dos dispositivos e integração do mesmo à parede do vaso. Algumas desvantagens significantes incluem dificuldade do manejo, alto custo, difícil manutenção e regulamentações legais, dificultando a disponibilidade de diversas espécies animais. Modelos em animais menores, como os coelhos e camundongos, embora sejam menos caros e de fácil obtenção, não são adequados para estudos de técnicas endovasculares pelas pequenas dimensões de seus vasos. Nenhum modelo descrito até o momento consegue reproduzir todas as características dos aneurismas observados em humanos. Modelos disponíveis são descritos nesta revisão, e suas vantagens e desvantagens são discutidas.

Endovascular aneurysm repair: current and future status

Endovascular aneurysm repair has rapidly expanded since its introduction in the early 1990s. Early experiences were associated with high rates of complications including conversion to open repair. Perioperative morbidity and mortality results have improved but these concerns have been replaced by questions about long-term durability. Gradually, too, these problems have been addressed. Challenges of today include the ability to roll out the endovascular technique to patients with adverse aneurysm morphology. Fenestrated and branch stent-graft technology is in its infancy. Only now are we beginning to fully understand the advantages, limitations, and complications of such technology. This paper outlines some of the concepts and discusses the controversies and challenges facing clinicians involved in endovascular aneurysm surgery today and in the future.

Models of abdominal aortic aneurysm: characterization and clinical applications

Abdominal aortic aneurysms (AAAs) are responsible for considerable morbidity, mortality, and cost to society. The pathogenesis of AAA formation, however, remains poorly understood. Animal models have been used in a range of experiments designed to provide further objective scientific assessment of the pathogenesis as well as the treatment of AAA. The purpose of this manuscript is to review the current models of AAA and their potential clinical implications.

Aneurysm Sac Pressure after EVAR: The Role of Endoleak

OBJECTIVE

The relation between endoleak and aneurysm sac pressure is not completely clear. This review evaluates the effect of endoleaks on aneurysm sac pressure and summarizes the present knowledge regarding aneurysm sac pressure after EVAR.

METHODS

A systematic search of literature was carried out using MEDLINE, EMBASE and Web of Science. Studies were included if aneurysm sac pressure measurements as well as systemic pressure measurements were performed during or after EVAR. Mean pressure indices (MPI), ratio mean aneurysm sac pressure to mean systemic pressure), in the absence of endoleaks and in the presence of different type of endoleaks were compared.

RESULTS

Stent-graft deployment does not seem to result in immediate reduction of aneurysm sac in the absence of an endoleak. Aneurysm sac pressure is elevated in the presence of an endoleak. However, the MPIs differ widely between studies both in the absence and presence of an endoleak.

CONCLUSION

MPI is not specific to the type of endoleak. This implies that the same type of endoleak does not necessarily pose the same MPI and by this the same hazard of aneurysm rupture, because the aneurysm sac pressure is directly related to the aneurysm wall stress.

Sealing of type III endoleaks with ethylene vinyl alcohol copolymer in a canine model

PURPOSE

To test ethylene vinyl alcohol copolymer (EVOH) as a sealing agent for persistent abdominal aortic aneurysm (AAA) endograft leaks.

MATERIALS AND METHODS

Twelve dogs underwent creation of AAAs with a Palmaz P4014 stent. A 10-mm x 5-cm Wallgraft endoprosthesis with a 4-mm-diameter hole cut into its side was deployed within the AAA. One week later, computed tomography (CT) and angiography were performed and the aneurysm sac was catheterized through the 4-mm hole. Then, EVOH was injected into the sac and lumbar arteries. Four weeks thereafter, all surviving animals underwent repeat CT scanning and angiography and were then euthanized. The AAA underwent gross and microscopic study.

RESULTS

Three dogs died from aortic rupture within 24 hours of AAA creation and the remaining nine dogs survived to receive EVOH. All nine dogs had persistent flow into the sac and lumbar arteries at the time of EVOH delivery. Seven dogs survived to the end of the experiment, and all aneurysm sacs and lumbar arteries remained occluded on angiography and CT. Histologic examination revealed EVOH and thrombus admixed, with thrombus in varying stages of organization filling the aneurysm sac and lumbar arteries.

CONCLUSIONS

Embolization of type III endoleaks with EVOH proved to be feasible in a canine model. Further work is warranted to determine its therapeutic utility.

Surgical access of the gluteal artery to embolize a previously excluded, expanding internal iliac artery aneurysm

We describe open exposure of the inferior gluteal artery to allow coil embolization on an enlarging internal iliac artery aneurysm after previous abdominal aortic aneurysm (AAA) repair. An 84-year-old man with a stoma had undergone open AAA repair surgery 8 years previously, during which the proximal aortic neck and both proximal external iliac arteries were ligated, followed by an aorta to right external iliac and left common femoral bypass. Eight years later, he complained of abdominal pain, and a computed tomographic (CT) scan revealed persistent flow in the right internal iliac artery with enlargement to 8 cm in diameter. Because prograde access to the internal iliac artery was not possible as a result of the previous exclusion, the inferior gluteal artery was exposed surgically. Coil embolization of the arteries supplying the internal iliac artery aneurysm was successfully performed. The AAA and internal iliac artery aneurysm were treated by the exclusion technique. Eight years after the operation, CT revealed that the iliac artery had expanded to approximately 8 cm in diameter. The patient was placed face down, and a catheter was directly inserted into the internal iliac artery from the inferior gluteal artery. Four embolization coils were placed in the internal iliac artery and its branches. Absence of blood flow and shrinkage of the aneurysm were subsequently confirmed in the aneurysm, as shown by echogram color duplex scanning and CT scanning at 1 year. This technique could also be applicable for persistent blood flow in an internal iliac aneurysm after endovascular AAA repair, and the size of the aneurysm was reduced to approximately 1 cm 1 year after the operation.

Aortic compliance following EVAR and the influence of different endografts: determination using dynamic MRA

PURPOSE

To utilize dynamic magnetic resonance angiography (MRA) to characterize aortic stiffness (beta) and elastic modulus (Ep) as indexes of wall compliance during the cardiac cycle and determine any influence of different endograft designs or the presence of endoleaks on these indexes.

METHODS

Eleven consecutive patients (11 men; median age 74 years, range 63-78) with abdominal aortic aneurysm (AAA) selected for endovascular repair were scanned pre- and postoperatively. Aortic area and diameter changes during the cardiac cycle were determined using dynamic MRA at 4 levels: 3 cm above the renal arteries, between the renal arteries, 1 cm below the renal arteries, and at the level of maximum aneurysm sac diameter. Ep and beta were calculated. Data are presented as median (range); p<0.05 was considered significant.

RESULTS

Preoperatively, Ep and beta were significantly higher at the level of the aneurysm sac compared to all other levels (p<0.05). Following EVAR, stiffness increased at this level (p<0.05). After implantation, patients with an Excluder endograft demonstrated Ep and beta measurements at the aneurysm neck that were 94% and 60% higher, respectively, compared to those with a Talent (p<0.05) endograft. The presence of an endoleak had no effect on Ep or beta.

CONCLUSION

This study introduces the feasibility of dynamic MRA imaging-based calculations of aortic elastic modulus and stiffness. AAA patients demonstrate increased Ep and beta at the level of the aneurysm sac. EVAR results in increased aneurysm sac Ep and beta. Stent-graft design seems to alter Ep and beta within the aneurysm neck, which may have consequences for endograft durability. The presence of an endoleak does not seem to have an effect on Ep or beta.

Evaluation of the accuracy of a wireless pressure sensor in a canine model of retrograde-collateral (type II) endoleak and correlation with histologic analysis

BACKGROUND

The utility of intra-aneurysmal pressure determination is dependent on the ability to measure pressure in the presence of endoleak and thrombosis. In this study, the accuracy of a CardioMEMS wireless pressure sensor (CardioMEMS, Atlanta, Ga) transducer in the presence of thrombus associated with type II endoleak was measured.

METHODS

Type II endoleaks were created in four mongrel dogs by implanting four collateral arterial side branches (lumbar and caudal mesenteric arteries) as a Carrel patch onto a 3-cm prosthetic polytetrafluoroethylene abdominal aortic aneurysm (AAA). The aneurysm was excluded 2 weeks later from antegrade perfusion by a stent graft. The wireless pressure sensor was positioned in the AAA external to the stent graft. A Konigsberg intraluminal solid-state strain-gauge pressure transducer (Konigsberg Instruments, Pasadena, Calif) that is accurate in the presence of thrombus served as the control to determine AAA pressure. Both of the transducers were implanted on the luminal surface of the aneurysm, 180 degrees opposite from the Carrel patch and endoleak channel. Intra-aneurysmal pressure resulting from the type II endoleak was measured twice daily for 4 weeks using both transducers. A total of 56 pre-exclusion and 224 post-exclusion distinct pressure determinations were made. Intra-aneurysmal pressure was indexed to the systemic pressure that was simultaneously measured by a strain-gauge pressure transducer implanted in the native aorta. Histologic analysis of the aneurysm contents was performed with hematoxylin and eosin.

RESULTS

The intra-aneurysmal systolic, mean, and pulse pressures produced by the type II endoleak were significantly lower than systemic pressure in all animals and were < 60% of systemic pressure (P < .001). Close correlation between the wireless transducer and the control strain-gauge transducer was observed (R = 0.83, P < .001). Arteriography and Doppler ultrasound documented retrograde flow through the aneurysm side branches and persistent endoleak patency up to the time of euthanasia. Pathologic analysis demonstrated the endoleak channel to be patent and separated from the transducers by thrombus, which surrounded both transducers.

CONCLUSIONS

Intra-aneurysmal pressure generated by type II endoleaks may be accurately measured through thrombus using a wireless pressure sensor in the canine model. The wireless sensor has the potential for clinical applicability in diagnosing and characterizing type II endoleaks.

Endovascular Treatment of an Internal Iliac Artery Aneurysm Using a Nitinol Vascular Occlusion Plug

PURPOSE

To report endovascular occlusion of an internal iliac artery (IIA) aneurysm with an Amplatz nitinol vascular occlusion plug.

CASE REPORT

A 71-year-old asymptomatic man who had previously undergone open aortic aneurysm repair presented for annual follow-up. A bifurcated Dacron graft had been inserted 12 years ago from the infrarenal aorta to the left common femoral artery and the right common iliac artery. The left common iliac artery was ligated proximally, and the left external iliac artery (EIA) provided retrograde flow into the IIA. Magnetic resonance imaging (MRI) revealed a 7.4-cm aneurysm of the left IIA. After transfemoral calibrated catheter angiography was performed, the proximal EIA was occluded with an Amplatz nitinol vascular occlusion plug. In addition, microcoils were placed distal to the vascular plug to achieve complete thrombosis of the vessel. One day after treatment, the patient was discharged free of symptoms after MRI had shown complete obliteration of the IIA aneurysm. At 6 months, the patient was free from symptoms, and angiography confirmed exclusion of the IIA aneurysm.

CONCLUSIONS

This case illustrates the technical feasibility and successful short-term follow-up of a novel embolization approach to IIA aneurysms in patients with an aortofemoral graft.

Treatment of type II endoleaks with a novel polyurethane thrombogenic foam: Induction of endoleak thrombosis and elimination of intra-aneurysmal pressure in the canine model

OBJECTIVE

The clinical significance and treatment of retrograde collateral arterial perfusion of abdominal aortic aneurysms after endovascular repair (type II endoleak) have not been completely characterized. A canine abdominal aortic aneurysm model of type II endoleak with an implanted pressure transducer was used to evaluate the use of polyurethane foam to induce thrombosis of type II endoleaks. The effect on endoleak patency, intra-aneurysmal pressure, and thrombus histology was studied.

METHODS

Prosthetic aneurysms with an intraluminal, solid-state, strain-gauge pressure transducer were created in the infrarenal aorta of 14 mongrel dogs. Aneurysm side-branch vessels were reimplanted into the prosthetic aneurysm of 10 animals by using a Carrel patch. Type II (retrograde) endoleaks were created by excluding the aneurysm from antegrade perfusion with an impermeable stent graft. Thrombosis of the type II endoleak was induced by implantation of polyurethane foam into the prosthetic aneurysm sac of four animals. Six animals with type II endoleaks were not treated. In four control animals, no collateral side branches were reimplanted, and therefore no endoleak was created. Intra-aneurysmal and systemic pressures were measured daily for 60 to 90 days after the implantation of the stent graft. Endoleak patency and flow were assessed during surgery and at the time of death by using angiographic imaging and duplex ultrasonography. Histologic analysis of the intra-aneurysmal thrombus was also performed.

RESULTS

Intra-aneurysmal pressure values are indexed to systemic pressure and are represented as a percentage of the simultaneously obtained systemic pressure, which has a value of 1.0. All six animals with untreated type II endoleaks maintained patency of the endoleak and side-branch arteries throughout the study period. Compared with control aneurysms that had no endoleak, animals with patent type II endoleaks exhibited significantly higher intra-aneurysmal pressurization (systolic pressure: patent type II endoleak, 0.702 +/- 0.283; control, 0.172 +/- 0.091; P < .001; mean pressure: endoleak, 0.784 +/- 0.229; control, 0.137 +/- 0.102; P < .001; pulse pressure: endoleak, 0.406 +/- 0.248; control, 0.098 +/- 0.077; P < .001; P < .001 for comparison for all groups by analysis of variance). Treatment of the type II endoleak with polyurethane foam induced thrombosis of the endoleak and feeding side-branch arteries in all four animals with type II endoleaks. This resulted in intra-aneurysmal pressures statistically indistinguishable from the controls (systolic pressure, 0.183 +/- 0.08; mean pressure, 0.142 +/- 0.09; pulse pressure, 0.054 +/- 0.04; not significant). Angiography and histology documented persistent patency up to the time of death (mean, 64 days) for untreated type II endoleaks and confirmed thrombosis of polyurethane foam-treated endoleaks in all cases.

CONCLUSIONS

Untreated type II endoleaks were associated with intra-aneurysmal pressures that were 70% to 80% of systemic pressure. Treatment with polyurethane foam resulted in a reduction of intra-aneurysmal pressure to a level that was indistinguishable from control aneurysms that had no endoleak.

CLINICAL RELEVANCE

Endovascular repair of abdominal aortic aneurysms is dependent on the successful exclusion of the aneurysm from arterial circulation. Type II endoleaks originate from retrograde flow into the aneurysm sac. This study demonstrates the use of polyurethane foam to induce thrombosis in a canine model of a type II endoleak, thereby reducing intra-aneurysmal pressure to levels similar to levels in animals without endoleaks. This approach may be a strategy for future treatment of type II endoleaks.

Intrathrombotic pressure of a thrombosed abdominal aortic aneurysm

In a case of thrombosed abdominal aortic aneurysm, intraluminal and intrathrombotic pressures were simultaneously measured 3 cm distal to the left renal vein level (#1), at the inferior mesenteric artery level (#2) (3 cm distal to #1), 3 cm distal to #2 (#3), and at the aortic bifurcation level (#4) (3 cm distal to #3). The intraluminal pressure (at #1) was 154/72 (101) mmHg, and the intrathrombotic pressures at #2, #3, and #4 were 138/77 (100), 137/74 (97), and 135/68 (96) mmHg, respectively. The percentages of the systolic and mean intrathrombotic pressures to the intraluminal pressure were 90% and 99% at #2, 89% and 96% at #3, and 88% and 95% at #4, respectively. The mural thrombus of an aneurysm does not significantly decrease the pressure on the aneurysmal wall, even in a thrombosed aneurysm.

Telementoring During Endovascular Treatment of Abdominal Aortic Aneurysms:A Prospective Study

PURPOSE

To explore the use of telementoring for distant teaching and training in endovascular aortic aneurysm repair (EVAR).

METHODS

According to a prospectively designed study protocol, 48 patients underwent EVAR: the first 12 patients (group A) were treated at a secondary care center by an experienced interventionist, who was training the local team; a further 12 patients (group B) were operated by the local team at their secondary center with telementoring by the experienced operator from an adjacent suite; and the last 24 patients (group C) were operated by the local team with remote telementoring support from the experienced interventionist at a tertiary care center. Telementoring was performed using 3 video sources; images were transmitted using 4 ISDN lines. EVAR was performed using intravascular ultrasound and simultaneous fluoroscopy to obtain road mapping of the abdominal aorta and its branches, as well as for identifying the origins of the renal arteries, assessing the aortic neck, and monitoring the attachment of the stent-graft proximally and distally.

RESULTS

Average duration of telementoring was 2.1 hours during the first 12 patients (group B) and 1.2 hours for the remaining 24 patients (group C). There was no difference in procedural duration (127+/-59 minutes in group A, 120+/-4 minutes in group B, and 119+/-39 minutes in group C; p=0.94) or the mean time spent in the ICU (26+/-15 hours in group A, 22+/-2 hours in group B, and 22+/-11 hours for group C; p=0.95). The length of hospital stay (11+/-4 days in group A, 9+/-4 days in group B, and 7+/-1 days in group C; p=0.002) was significantly different only for group C versus A (p=0.002). Only 1 (8.3%) patient (in group A: EVAR performed by the experienced operator) required conversion to open surgery because of iliac artery rupture. This was the only conversion (and the only death) in the entire study group (1/12 in group A versus 0/36 in groups B + C, p=0.31).

CONCLUSIONS

Telementoring for EVAR is feasible and shows promising results. It may serve as a model for development of similar projects for teaching other invasive procedures in cardiovascular medicine.

Characterization of retrograde collateral (type II) endoleak using a new canine model

OBJECTIVE

The clinical significance of retrograde collateral arterial perfusion of abdominal aortic aneurysms after endovascular repair (type II endoleak) has not been completely characterized. In this study a canine model was used to analyze intra-aneurysmal pressure, thrombus histologic characteristics, endoleak patency, and radiographic appearance of type II endoleaks originating from single and multiple aneurysm side branches.

METHODS

Prosthetic aneurysms with an intraluminal solid-state strain-gauge pressure transducer were created in the infrarenal aorta of 14 mongrel dogs. A single collateral side branch was reimplanted in 4 animals, multiple side branches were reimplanted in 6 animals, and no side branches were reimplanted in 4 control animals. Intra-aneurysmal and systemic pressure was measured for 60 to 90 days after creation of the type II endoleak. Endoleak patency and flow were assessed with duplex ultrasound scanning and cine-magnetic resonance angiography. Histologic analysis of the intra-aneurysmal thrombus was also performed.

RESULTS

Stent-graft exclusion reduced intra-aneurysmal pressure significantly in all animals, as compared with systemic pressure (P < .001). All intra-aneurysmal pressure values are indexed to the systemic pressure, and are represented as a percentage of the simultaneously obtained systemic pressure, which has a value of 1.0. Type II endoleaks originating from multiple side branches exhibited significantly increased intra-aneurysmal systolic pressure, mean pressure, and pulse pressure, as compared with endoleaks derived from either a single side branch (systolic pressure: multiple, 0.70 +/- 0.28 vs single, 0.50 +/- 0.19; P < .001; mean pressure: multiple, 0.78 +/- 0.23 vs single, 0.59 +/- 0.22, P < .001; pulse pressure: multiple, 0.41 +/- 0.25 vs single, 0.17 +/- 0.15, P < .001) or excluded control aneurysms that had no side branches and no endoleak (systolic pressure, 0.17 +/- 0.09; mean pressure, 0.14 +/- 0.10; pulse pressure, 0.098 +/- 0.08; P < .001). Cine-magnetic resonance angiograms and duplex ultrasound scans documented persistent patency of multiple branch endoleaks up to the time of euthanasia. In contrast, single side branch endoleaks thrombosed within 3 days (P < .001). Thrombus in the aneurysm sac in close proximity to the endoleak contained intact red blood cells and limited fibrin. Thrombus distant from the endoleak demonstrated extensive fibrin deposition and degraded red blood cells.

CONCLUSION

The canine model may be used to reliably measure intra-aneurysmal pressure in the presence of patent and thrombosed type II endoleaks. In this model 2 or more side branches are necessary to maintain persistent patency of type II endoleaks. These endoleaks are associated with significantly elevated intra-aneurysmal pressure, that is, 70% to 80% of systemic pressure. These results suggest that persistent type II endoleaks have clinical significance.

CLINICAL RELEVANCE

Endoleaks originating from retrograde flow in the side branch vessels of the aneurysm generate significant levels of intra-aneurysmal pressure, that is, 70% to 80% of systemic pressure. At least 2 patent side branch vessels appear to be necessary to cause persistent patency of type II endoleak in the canine model. Further studies will be necessary to enable more complete characterization of retrograde endoleaks and to extend these findings to allow clinical application. However, these results suggest that persistently patent type II endoleaks are clinical significance and may require more intensive follow-up intervention.

Effectiveness of coiling in the treatment of endoleaks after endovascular repair

BACKGROUND

Persistent endoleaks are a common problem following endovascular repair of abdominal aortic aneurysms, and the best method of treatment has been an issue of debate. Some experimental evidence has suggested that coiling may not be an effective method because it allows transmission of pressure across the coils with continued expansion of the sac. We reviewed our experience with endoleak coiling to assess the degree of clinical success of this treatment.

METHODS

A retrospective review of patients with type I or type II endoleaks treated solely by coiling over a 7-year period (1997-2003) was performed. All endoleaks had been observed for at least 6 months prior to intervention to detect spontaneous resolution. All coils were delivered by selective catheterization of the endoleaks. For Type II endoleaks, the branches were all coiled at their junction with the sac when feasible and the endoleak cavity was packed. Clinical success was defined as cessation of endoleak on follow-up computed tomography as well as no further aneurysmal growth (> or =5mm minor axis).

RESULTS

Twenty-eight patients had their endoleaks treated only with coils. There were 22 Ancure, 2 Excluder, 2 AneuRx, and 2 Lifepath endografts in this patient cohort. Procedural morbidity was 0%. Mean follow-up after coiling for all patients was 18 months (range, 1-60 months) while mean follow-up for patients with a type I endoleak was 24 months. Clinical success was achieved in 15 of 19 (79%) patients with type II endoleaks and 8 of 9 (89%) patients with type I. Three patients, all with type I endoleak, required more than 1 episode of coiling, while 2 others, both with type II lumbar endoleaks, required repeat angiography due to inability to access the leak during the first attempt. There were 2 proximal and 6 distal type I endoleaks (2 aortic, 6 iliac) successfully treated while the type II successes included 8 inferior mesenteric artery and 7 sole lumbar endoleaks. Five patients continued to show evidence of endoleak over time: 2 endoleaks were associated with aneurysm growth leading to conversion in 1 patient, 2 patients with type II endoleaks are stable, and the sole type I endoleak with continued perigraft flow has shown significant shrinkage of the sac and continues to be observed 18 months later. No ruptures were noted during follow-up.

CONCLUSION

Coiling as the sole method of endoleak management may be a suitable treatment option in selected patients. Clinical success can be expected in over 80% of patients with type II and select type I endoleaks, with minimal morbidity.

Type II endoleak in porcine model of abdominal aortic aneurysm

PURPOSE

The purpose of this study was to develop a reliable in vivo porcine model of type II endoleak resulting from endovascular aortic aneurysm repair (EVAR), for the study and treatment of type II endoleak.

METHODS

Eight pigs underwent creation of an infrarenal aortic aneurysm, with a Dacron patch with preservation of lumbar branches. An indwelling pressure transducer was placed in the aneurysm sac. After 1 week the animals underwent EVAR with a custom-made Talent endograft. After another week the animals underwent laparoscopic lumbar artery ligation. Abdominal and pelvic computed tomography was performed after each procedure. Aneurysm sac pressure was measured in sedated and awake animals.

RESULTS

All eight animals underwent successful creation of an aortic aneurysm and EVAR resulting in exclusion of the aneurysm sac. After creation of the aneurysm the sac mean arterial pressure (MAP) was 72.5 +/- 6.1 mm Hg and the sac pulse pressure was 44.8 +/- 8.7 mm Hg. Postoperative computed tomography scans demonstrated a type II endoleak from the lumbar branches in all animals. While aneurysm sac MAP (56.5 +/- 7.9 mm Hg; P <.01) and pulse pressure (13.6 +/- 4.1 mm Hg; P <.01) decreased after EVAR, sac pulse pressure remained, with type II endoleak. All animals underwent laparoscopic lumbar artery ligation, which resulted in further reduction in the sac MAP (38.3 +/- 4.6 mm Hg; P <.02) and immediate absence of sac pulse pressure (0 mm Hg; P <.01). Necropsy confirmed the absence of collateral flow in the aneurysm sac, with fresh thrombus formation in all animals.

CONCLUSION

We present a reliable and clinically relevant in vivo large animal model of type II endoleak.

CLINICAL RELEVANCE

We set out to show that aortic aneurysm sac pressurization caused by lumbar arterial flow in the setting of type II endoleak can be reproduced in an in vivo porcine model of endovascular aortic aneurysm repair. Indeed, in this model the aneurysm sac pulse pressure was a sensitive indicator of type II endoleak, correlating well with findings at computed tomography, and lumbar artery ligation eliminated the endoleak, as demonstrated on computed tomography scans and sac pressure measurement. Therefore we believe this in vivo large animal model can be instrumental in the study of many aspects of the physiologic features of type II endoleak.

Endovascular treatment of abdominal aortic aneurysm

BACKGROUND

Endovascular repair of abdominal aortic aneurysm has become widely used. Supporters claim high success rates, few complications and a dramatically reduced hospital stay. However, endoleak, endotension and reports of endoprosthesis rupture are causes of concern.

METHODS

A Medline search was undertaken to identify articles on endovascular repair of abdominal aortic aneurysm. Additional papers were identified by manual scanning of the references from key articles.

RESULTS AND CONCLUSION

Endoleak is a potentially serious complication of the endovascular technique and occurs in a significant proportion of patients. It is still not possible to judge whether the presence of an endoleak alone signifies failure of treatment, and the long-term durability of prosthetic covered stents is unknown. However, endovascular repair does appear to confer a degree of protection from rupture although patients must be advised of the need for life-long imaging surveillance and, perhaps, further intervention.

Is a Type II Endoleak after EVAR a Harbinger of Risk? Causes and Outcome of Open Conversion and Aneurysm Rupture during Follow-up

OBJECTIVE

There is still debate whether type II endoleaks represent a risk for the patient after EVAR. Treatment policies vary from fairly conservative to active intervention. In this analysis risk factors for type II endoleak and adverse events during follow-up were assessed. In addition, risk factors and causes for conversion to open repair and for rupture post-EVAR were studied.

METHODS

The data of 3595 patients, who underwent operation between 1996 and 2002 in 114 European institutions that collaborated in the EUROSTAR Registry, were assessed. To accurately assess the influence of type II endoleaks patients with type I, III and combined endoleaks were excluded from the present study cohort.

RESULTS

A combined adverse outcome event consisting of aneurysmal growth, transfemoral reintervention, and transabdominal secondary procedures (including laparoscopic branch vessel clipping) occurred in 55% in patients with type II endoleak at 3 years, compared to 15% in patients without any endoleak (p<0.0001). Conversion to open repair or post-EVAR rupture was not significantly associated with type II endoleaks. An independent association of device migration and expansion of the aneurysm with late conversion was observed. The cumulative incidence of aneurysm rupture at 3 years of follow-up was 1.2% for an annual rate of 0.4%. Variables that significantly and independently correlated with rupture were size of the aneurysm at preoperative measurement and device migration during follow-up.

CONCLUSION

Endoleak type II may not be harmless as it was more frequently associated with enlargement of the aneurysm and reinterventions. Large aneurysms and migration of the device were the main risk factors for rupture. The clinical implications of these findings may involve more frequent surveillance visits for patients with type II endoleak. Aneurysm expansion is a clear indication for reintervention. Patients with large aneurysms, 65 mm or larger, may also benefit from a more comprehensive surveillance schedule.

Variable sac behavior after endovascular repair of abdominal aortic aneurysm: analysis of core laboratory data

OBJECTIVES

The behavior of the aneurysm sac after endovascular grafting has been the subject of significant speculation. The importance of sac behavior is manifested by the correlation between aneurysm size or size change and risk for rupture, and potentially further extrapolated to define the need for secondary intervention. This study was undertaken to define graft-specific differences and the effect of endoleak on sac remodeling.

METHODS

Core laboratory data were obtained for three US Phase II clinical trials. Patients were included if they met anatomic inclusion criteria and underwent placement of the latest version of a bifurcated endovascular prosthesis. Unsupported Dacron (Ancure), supported Dacron (Zenith), and expanded polytetrafluoroethylene (Excluder) grafts were evaluated. Digitized images were electronically assessed for aneurysm size (area, maximum, minimum diameter) with National Institutes of Health Image software. Two blinded reviewers analyzed each radiographic study to ensure accurate image selection and establish the presence or absence of endoleak. A third reviewer adjudicated discrepancies. chi(2) analysis and mixed nonlinear modeling were used to analyze the results.

RESULTS

Of 1506 patients evaluated, 723 (227 Ancure, 343 Excluder, 153 Zenith) met inclusion criteria for the study. Mean follow-up was 23.2 months (Ancure, 31.3 months; Excluder, 19.6 months; Zenith, 19.3 months). The incidence of any endoleak was 39.1% (Ancure, 58.1%; Excluder, 34.7%; Zenith, 20.9%; P <.001). Type of prosthesis, presence or absence of endoleak, and baseline size were determinants of rate of aneurysm shrinkage. Reduction in sac size was greatest with the Zenith graft, followed by the Ancure and Excluder grafts. Presence of endoleak had a moderating effect on rate of sac shrinkage with the Zenith and Ancure grafts; however, sac size increased in the presence of endoleak with the Excluder graft. Finally, baseline size was positively correlated with rate of aneurysm shrinkage.

CONCLUSIONS

The behavior of the aneurysm sac depends on the type of prosthesis, presence or absence of endoleak, and baseline size of the sac. Differential sac behavior must be considered when determining the need for secondary interventions, timing follow-up studies, and assessing success or failure of endovascular repair.

Endotension is Influenced by Wall Compliance in a Latex Aneurysm Model

OBJECTIVES

Even though endovascular aneurysm repair (EVAR) creates a closed chamber except for patent branches, the intra-sac pressure is never zero. This study was designed to investigate whether, and to what extent, aneurysm wall compliance influences intra-sac pressure.

DESIGN

In vitro experimental study.

METHODS

Aneurysm models with six and 12 latex layers were produced, resulting in elastic and stiff circumferential compliance (3.5 +/- 0.5 and 0.9 +/- 0.3%/100 mmHg, respectively). The models with an 18 mm internal neck and maximum aneurysm diameter of 60 mm were inserted into an in vitro circulation system. The systemic mean pressure (SPmean) was varied from 50 to 120 mmHg. After the aneurysm was excluded with a knitted polyethylene graft, aneurysm sac mean pressure (ASPmean) and aneurysm sac pulse pressure (ASPpulse) were measured. Data are presented as mean +/- SD. Statistics were performed using repeated measurements of variance; p<0.05 was considered significant.

RESULTS

In the model EVAR created a closed chamber without endoleak, but with an aneurysm sac pressure related to wall compliance. In the elastic aneurysm model with six latex coats the aneurysm sac mean pressure (ASPmean) and the aneurysm sac pulse pressure (ASPpulse) at all systemic pressures were significantly lower than they were in the stiffer model with 12 latex coats (p<0.05). At a SPmean of 90 mmHg, the ASPmean was 21.0 +/- 0.9 mmHg (six latex coats) and 26.0 +/- 0.2 mmHg (12 latex coats) (p<0.05), the ASPpulse was 5.7 +/- 0.2 mmHg (six latex coats) and 8.8 +/- 0.3 mmHg (12 latex coats) (p<0.05).

CONCLUSIONS

This in vitro model demonstrated that the aneurysm sac mean pressure (ASPmean) and the aneurysm sac pulse pressure (ASPpulse) were significantly influenced by the compliance of the aneurysm wall. These data highlight the need for further studies regarding endotension.

Small Intestinal Submucosa Aneurysm Sac Embolization for Endoleak Prevention after Abdominal Aortic Aneurysm Endografting: A Pilot Study in Sheep

PURPOSE

To percutaneously create an improved abdominal aortic aneurysm model of endoleak after endograft placement and to explore efficacy of small intestinal submucosal embolization of the residual aneurysmal sac for prevention of endoleaks.

MATERIALS AND METHODS

Abdominal aortic aneurysm was created transluminally by over-dilation of a Palmaz stent in 12 sheep. Approximately 20% undersized endografts suspended between two stent-graft adapters were used to bridge the aneurysm in a manner that two lumbar pairs remained patent within the residual aneurysm sac. Size of the residual aneurysm sac was increased by placement of an undersized stent-graft consisting of damaged lyophilized small intestinal submucosal sheets sandwiched between two Zilver stents. In six sheep, residual aneurysm sacs were embolized by combining small intestinal submucosal sponge and small intestinal submucosal sheet pieces. The other six sheep served as the control group. Angiography performed immediately after the procedure was compared with follow-up angiography before the animals were killed at 1, 3, and 7 months. Gross and histologic examinations were also obtained.

RESULTS

Aortic ruptures (n = 3) and dissections (n = 2) during aneurysm creation responded well to endograft placement. Eleven endografts were placed successfully, one was misplaced. The mean diameter of aneurysmal sac was 16 mm in the study and 15.2 mm in the control group. In the study group, in four sheep, the sac and seven pairs of lumbar arteries were occluded by embolization and remained obstructed by organized thrombus during the entire study. There were no type II endoleaks. Four type III new endoleaks developed without antegrade filling of lumbar arteries. In the control group, five animals had type I and II endoleaks at the initial studies. Only one sheep exhibited completely organized thrombosis of the aneurysmal sac and without endoleaks. In the other four sheep with partially organized sac thrombosis, endoleaks were unchanged. One type III endoleak occurred in this group.

CONCLUSION

The combination of small intestinal submucosal sponge and small intestinal submucosal sheet pieces is a promising embolic material for occlusion of the residual sac after endovascular abdominal aortic aneurysm repair and for prevention of type II endoleaks.

Surgical repair of a distal arch aneurysm with a stent-graft

This study evaluates the effectiveness and potential complications of stent-grafting for the treatment of distal arch aneurysms using profound hypothermia and circulatory arrest with retrograde cerebral perfusion. Between December 1998 and December 2001, 9 consecutive patients with a distal arch aneurysm (6 men and 3 women, mean age 71 years) underwent surgical repair using a stent-graft. Profound hypothermic circulatory arrest and retrograde cerebral perfusion were performed in all patients. Endovascular leakage was screened postoperatively using three-dimensional computerized tomography. The mean follow-up period was 27.4 months. Thirty day mortality was 0%. One patient died 3 months after stent-grafting due to proximal leakage into her aneurysm. The mean postoperative extubation period was 2.1 days. No patients suffered cerebral infarction or paraplegia. Although preliminary outcomes using this technique were good, endovascular leakage is a concern. We suggest that, if major proximal leakage is recognized postoperatively, re-intervention should be performed as soon as possible. Endovascular stent-grafting appears to be a good alternative treatment for distal arch aneurysms, although longer follow-up is necessary to more comprehensively evaluate this procedure.

Endotension as a Result of Pressure Transmission through the Graft following Endovascular Aneurysm Repair—An In vitro Study

BACKGROUND

endovascular aneurysm repair (EVAR) significantly reduces, but does not abolish aneurysm sac pressure, possibly because of trans-fabric transmission.

OBJECTIVE

to investigate how blood pressure is transmitted through different types of grafts into the aneurysm sac.

DESIGN

experimental study, in vitro.

METHODS

a latex aneurysm was inserted into an in vitro circulation model. The systemic mean pressure (SPmean) was varied from 50 to 120 mmHg. The grafts used for aneurysm exclusion were: thin wall polyethylene (PE), thick wall polyethylene (PE) and thin wall ePTFE. Mean aneurysm sac pressure (ASPmean) was measured, as was pulse pressure (ASPpulse).

RESULTS

at an SPmean of 70 mmHg, the ASPmean was 34 +/- 0.8 mmHg (polyethylene knitted, thick wall), 30 +/- 1.0 mmHg (polyethylene woven, thin wall), and 17 +/- 0.6 mmHg (thin wall ePTFE). The ASPmean increased with SPmean, the relationship depending on the graft material. Stiffer grafts were associated with lower ASPmean and ASPpulse (p<0.001).

CONCLUSIONS

the relationship between aneurysm sac mean pressure and systemic pressure (SP) depends on the graft material. These data highlights the need for further studies regarding endotension.

Technique and results of transfemoral superselective coil embolization of type II lumbar endoleak

OBJECTIVE

This study was undertaken to describe the technique of transfemoral superselective coil embolization of type II endoleak and its influence on abdominal aortic aneurysm diameter.

METHODS

Over 23 months, 104 aortic stent grafts were deployed to exclude abdominal aortic aneurysms, at an academic medical center. Increase in aneurysm diameter and perigraft findings on contrast material-enhanced computed tomography scans prompted arteriography. Procedures were performed solely by vascular surgeons in a surgical angiography suite. In 7 patients aneurysm access was via the iliolumbar branches of the internal iliac artery, and in 1 patient aneurysm access was via the inferior mesenteric artery through the arc of Riolan from the superior mesenteric artery. Coaxial catheters were placed to gain access to the aneurysm (8F to 5F to 3F, or 5F to 3F). A 3F Tracker18 was the most distal catheter through which an assortment of 0.018 microcoils were deployed within the aneurysm, and the origin of the feeding vessels when possible.

RESULTS

Aneurysm diameter increased 0.48 +/- 0.2 cm over 10.8 +/- 5 months before superselective coil embolization. In 6 of 8 patients superselective coil embolization embolization resulted in a mean decrease in aneurysm diameter of 1.3 +/- 1.2 cm over 9 +/- 3.2 months. Failure was presumed due to inability to reach the aneurysm sac in 1 patient and was associated with oral anticoagulation in 1 other patient.

CONCLUSION

Proper identification of the source of type II endoleak and its complete occlusion, combined with aneurysm sac coiling, may result in prompt decrease in aneurysm size.

The significance and management of different types of endoleaks

Development of endovascular abdominal aortic aneurysm repair (EVAR) has been accompanied by previously unencountered complications. The most challenging but least understood of these complications is the incomplete seal of the endovascular graft (endoleak), a phenomenon that has a variety of causes. An important consequence of endoleakage may be persistent pressurization of the aneurysm sac, which may ultimately lead to post-EVAR rupture. Data of 110 European centers were recorded in a central database (EUROSTAR). Patient, anatomic characteristics, and operative and device details were correlated with the occurrence of different types of endoleaks. Outcome events during follow-up, particularly expansion of the aneurysm, incidence of conversion to open repair, and post-EVAR rupture were assessed in the different categories of endoleaks and in a group of patients without any endoleak. Type I and III endoleak were associated with an increased frequency of open conversions or risk of rupture of the aneurysm. Device-related endoleaks also correlated with an increased need for secondary interventions. These types of endoleaks need to be treated without delay, and when no other possibilities are present, an open conversion to avert the risk of rupture should be considered. Type II endoleaks do not pose an indication for urgent treatment. However, they may not be harmless, because there was a frequent association with enlargement of aneurysm and reinterventions. Our findings suggest that more frequent surveillance examinations are indicated than in patients without collateral endoleak. The indication for intervention is primarily dictated by documented expansion of the aneurysm.

Management of endoleak after endovascular aneurysm repair: cuffs, coils, and conversion

OBJECTIVE

The effectiveness of endovascular treatment of abdominal aortic aneurysm (AAA) may be limited by persistent perfusion of the aneurysm sac (endoleak). Endoleak that results in persistent systemic pressurization of the aneurysm or in continued AAA expansion is believed to require treatment to prevent rupture. This report describes the results of three techniques used to treat endoleak.

METHODS

Endovascular repair of AAA was performed in 597 patients between January 1996 and September 2002. Seventy-three endoleaks that required treatment developed in 70 patients (11.7%). These involved the graft attachment site (type I) or the graft junction site (type III) or originated from collateral side-branch vessels (type II) and were associated with an increase in aneurysm size. Endoleak type was confirmed at angiography in all cases. Average time between the initial endovascular procedure and endoleak treatment was 14.5 +/- 5.7 months. The techniques used for endoleak treatment were deployment of an endovascular extension graft or cuff (n = 44), coil embolization (n = 24,) and conversion to conventional open repair (n = 5). Configurations of endovascular grafts in which endoleak developed were bifurcated (n = 44), aortouniiliac (n = 15), and aortoaortic-tube (n = 11). Mean follow-up after endoleak treatment was 24.5 +/- 12.2 months (range, 1-60 months).

RESULTS

Endovascular extension grafts or cuffs were used to treat 41 attachment site endoleaks and 3 graft junction endoleaks, with overall technical success rate of 97%. Embolic coils were used to treat 16 retrograde side-branch endoleaks and 8 attachment site endoleaks, with overall technical success rate of 87%. Conversion to open surgery was performed in 4 patients with attachment site endoleaks and 1 patient with a graft junction site endoleak, and was successful in all cases. After endoleak treatment, aneurysm size decreased (>5 mm) in 38% of patients, stabilized in 58% of patients, and increased (>5 mm) in 4% of patients. Major morbidity occurred in 7.0%, with no perioperative deaths.

CONCLUSIONS

Endovascular extension grafts, coil embolization, and conversion to open surgery each may be used to effectively repair endoleak. Selection of the treatment method used is determined by the anatomic characteristics of the endoleak and the patient's ability to tolerate conventional repair. Conversion to open repair was uniformly successful. Deployment of an extension cuff was successful when complete closure of the endoleak was achieved. Embolic coils were effective for retrograde endoleaks and provided stabilization of AAA size in selected patients with attachment site endoleaks in limited follow-up.

Internal iliac aneurysm rupture into the rectum following endovascular exclusion: an unusual cause of massive lower gastrointestinal bleeding

PURPOSE

To report a rare iliorectal fistula following endovascular treatment of an internal iliac aneurysm.

CASE REPORT

A 76-year-old man developed lower gastrointestinal bleeding 3 months after successful endovascular exclusion of a left internal iliac aneurysm with coil embolization, attempted stent-grafting, ligation of the distal external iliac artery, and a femorofemoral crossover bypass. Aortography showed no clear intestinal bleeding point, but demonstrated recanalization and continued perfusion of the aneurysm. At laparotomy, an iliorectal fistula was detected. The common iliac artery was ligated proximally, the aneurysm sac was opened, and the back-bleeding internal iliac artery branches were oversewn. The rectum was closed primarily. He made an uneventful recovery.

CONCLUSIONS

An iliorectal fistula is an extremely rare and unlikely complication of coil occlusion of an iliac aneurysm. A high index of suspicion for the diagnosis is of paramount importance. Periodic imaging in these patients is required to detect recanalization and continuing aneurysm expansion.

Endovascular treatment of aneurysmal disease

Endovascular repair of abdominal aortic aneurysm using stent grafts that are delivered intraluminally by catheters is a less invasive alternative to open surgical repair. Endovascular surgery has been studied for over a decade, and early results are comparable to open repair. With extended follow-up care, however, postoperative complications and graft failures have been reported in some patients, resulting in reintervention, conversion to open repair, and death. The high incidence of secondary interventions causes some researchers to question the durability of endograft repair and emphasizes the need for detailed long-term follow-up care. This article describes the evolution of endovascular treatment of abdominal aortic aneurysm from its origin to its current state and discusses the future direction of endovascular therapy.

Intra-aneurysm sac pressure--the holy grail of endoluminal grafting of AAA

OBJECTIVES

To relate intra-aneurysm sac pressure during endoluminal AAA repair to early and late endoleak, as well as to the aneurysm size upon follow-up.

DESIGN

Prospective clinical investigation.

METHODS AND PATIENTS

In 46 patients who had their AAAs treated by a stent graft (group I), intra-operative pressure measurement was performed (aorta uni-iliac stent grafts: 25 cases, bifurcated stent grafts: 21 cases). In 18 patients with open repair (group II) flow in the inferior mesenteric artery, and the pressure in the aneurysm sac was measured, before and after aortic and iliac cross clamping. Values are given in median with range.

RESULTS

In group I, complete exclusion of AAA (no endoleak on intra-operative control angiogram) resulted in a statistically significant decrease in mean sac pressure from 74 (55-101) to 47 (4-104) mmHg. Pulse pressure reduced from 67 (34-103) to 8 (0-74) mmHg. In 11 patients a proximal type I endoleak was sealed by balloon modeling, after which the mean sac pressure reduced from 63 (14-91) to 52 (4-74) mmHg (n.s. versus patients with primary seal). Intra-operative pressure did not correlate with change in AAA diameter during twelve months follow-up. In group II, cross clamping of the proximal aorta significantly reduced mean sac pressure to 32 (21-55) mmHg, and the pulse pressure to 0 (0-13) mmHg (p < 0.05). Subsequent cross clamping of the iliac arteries did not significantly change the pressures.

CONCLUSIONS

Measurement of intra-aneurysm sac pressure can help to detect and treat endoleaks during endoluminal grafting. However, the intra-operative sac pressure did not predict the fate of aneurysm during follow up. Compared to open repair of AAA, the sac pressure after endoluminal grafting remains significantly higher, in relation to pulse pressure.

Type II endoleak: transperitoneal sacotomy and ligation of side branch endoleaks responsible for aneurysm sac expansion

PURPOSE

To demonstrate aneurysm sac expansion in the face of a type II endoleak and its treatment with open ligation of multiple side branch endoleaks.

CASE REPORT

An 81-year-old patient had undergone elective endovascular repair of a 6.3-cm infrarenal abdominal aortic aneurysm in September 1999. Routine spiral computed tomographic angiography at 10 months disclosed a type II endoleak; the aneurysm sac diameter had grown to 7.4 cm. Selective angiography revealed multiple lumbar endoleaks and a patent inferior mesenteric artery. Laparotomy and sacotomy was performed, confirming the presence of pulsatile type II endoleaks, which were ligated successfully. The patient made a full postoperative recovery.

CONCLUSIONS

Type II endoleaks may cause aneurysm expansion. Open repair of multiple type II endoleaks is feasible and may be useful where endovascular or laparoscopic techniques are at high risk of procedural failure, such as multiple endoleak channels.