A canine model for studying endoleak after endovascular aneurysm repair

PURPOSE: The aim of this study was to create an animal model of endoleak after stent-graft placement for abdominal aortic aneurysm (AAA) in which a large aneurysmal sac would be preserved for the testing of techniques for its percutaneous occlusion. MATERIALS AND METHODS: Infrarenal AAAs were created in nine dogs by anastomosis of an isolated segment of the inferior vena cava to the right side of the abdominal aorta in combination with a large anterior patch from the external jugular vein. One hour later, animals underwent percutaneous implantation of polytetrafluoroethylene-covered Z stent endografts with three 3-mm-diameter holes through the fabric. Aortograms were obtained before and after surgery, after endograft placement, and at the time of animal sacrifice at 1 week or 1, 2, 3, or 6 months. Pressures within the aorta and the aneurysm sac were recorded before animal sacrifice. Gross and histologic evaluations of the specimens were then carried out. RESULTS: Immediately after endograft placement, all nine animals had artificial type III endoleaks with angiographic filling of lumbar arteries and veins. One animal died of surgical complications within 2 days of surgery and is not included in our data analysis. One aneurysm ruptured at 1 week. At completion of the study, six endografts were patent and two were occluded. The aneurysm sac had enlarged by approximately 50% in seven animals. At follow-up, type I endoleak was present in three animals, type II endoleak was present in three, and the artificial type III endoleak was present in all six animals with patent endografts. The pressure differential between aorta and aneurysm sac was 36 mm Hg, with a mean aortic pressure of 87 mm Hg +/- 13.3 and a mean aneurysmal sac pressure of 51 mm Hg +/- 28.1. The aneurysmal sac exhibited early thrombus formation at 1 week, which progressed to complete thrombosis in 1-6 months. CONCLUSIONS: The model is technically feasible but would be useful in testing occlusive techniques for residual aneurysm sacs only in the acute phase after endograft placement. It would be not reliable for chronic evaluation because of rapidly progressive thrombosis in most aneurysm sacs and occasional complete thrombosis of the AAA and endograft.     

Use of the Endurant Stent Graft System for Ruptured Infrarenal Aortic Aneurysms: Short-term Experience in Nine Patients

PurposeTo report the early results of use of the Endurant stent graft in the treatment of ruptured abdominal aortic aneurysms (AAAs).Materials and MethodsNine consecutive patients (seven men and two women; mean age, 76 y; range, 65–87 y) underwent endovascular aneurysm repair (EVAR) for a ruptured AAA with the Endurant stent graft between April and December 2012. EVAR was emergent in all cases. Early technical success, clinical success, major complication, and mortality rates were analyzed.ResultsIntraoperative immediate technical success was achieved in all nine patients. The 30-day clinical success rate was 67% (six of nine patients). The 30-day mortality rate was 33% (three of nine patients). During a mean follow-up of 6 months (range, 3–10 mo), none of the cases required reintervention; there was one late death attributed to probable endograft infection.ConclusionsThe short-term results of EVAR with the Endurant stent graft in patients with ruptured AAAs are encouraging.     

CT of abdominal aortic aneurysms--aneurysmal size and thickness of intra-aneurysmal thrombus as risk factors of rupture

In order to seek for the factors to suggest a risk of rupture of abdominal aortic aneurysms (AAA), we measured the largest diameter of AAA and the thickness of intra-luminal thrombus on CT in 72 patients. The mean aneurysmal size was 64 mm in diameter in 9 patients with ruptured aneurysm and 61 mm in diameter in 63 patients with non-ruptured aneurysm respectively (p less than 0.90). The rupture of AAA was seen in 3 of 30 patients with AAA of the small size (less than 50 mm in diameter), in 3 of 16 patients with AAA of the intermediate size (51-66 mm in diameter) and in 3 of 26 patients with AAA of the large size (more than 70 mm in diameter), respectively. The mean intra-luminal thrombus was 9 mm in 9 patients with ruptured aneurysm and 19 mm in thickness in 63 patients with non-ruptured aneurysm respectively (p = 0.05). We concluded from the above results that the aneurysmal size was not important, but the thickness of intra-luminal thrombus was useful for suggestion of a risk of rupture of AAA.     

Radiologic features and anatomic basis of atypical clinical presentations of ruptured abdominal aortic aneurysms

Ruptured abdominal aortic aneurysms (AAAs) occasionally manifest with atypical clinical presentations and can be initially misdiagnosed. Symptoms are attributable either to local mass effect from the aneurysm or a contained rupture, or to the particular cavity or anatomic space into which an aneurysm bleeds. Radiologic studies obtained in this patient population often will demonstrate signs of the ruptured AAA, and these signs should be actively searched for when a ruptured AAA can be in the differential diagnosis. Emergent computed tomographic examination is indicated to confirm any clinical or radiologic suspicion of a ruptured abdominal aortic aneurysm, provided that the patient remains hemodynamically stable. The anatomic basis for a ruptured AAA presenting clinically as renal colic is discussed and illustrated, and the spectrum of clinical presentations of ruptured AAAs is reviewed.     

Twin-tube endografts for aortic aneurysms: an experimental feasibility study.

PURPOSE: To explore feasibility of twin-tube endografts (TTEGs) for treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAAs were created in six dogs by overdilation of Palmaz stents. TTEGs made of seven 9.5-mm-diameter Gianturco R?sch Z (GRZ) stents and covered with PTFE were deployed simultaneously from both femoral arteries through 10-F sheaths to exclude the AAA. Follow-up aortography was performed immediately and at 2, 4, and 8 weeks. Two dogs were killed at 4 weeks and four were killed at 8 weeks. Gross and histologic examinations were performed. RESULTS: AAA creation and TTEG placement were successful in all six dogs. TTEGs completely excluded AAAs in five dogs. Minor temporary perigraft leak was seen in one dog immediately after stent placement. Four dogs had TTEGs patent to termination at 8 weeks. In two dogs with oversized TTEGs, one of the twin endografts occluded at 2 weeks. At autopsy, TTEGs were formed in semicircular shape and histology did not show any significant inflammatory reaction. CONCLUSION: TTEGs show promise for treatment of AAA, with the potential of reducing the introductory sheath size. Further experimental studies, particularly with TTEGs extended into iliac arteries, are warranted.     

Initial experience of branched endovascular graft for abdominal aortic aneurysm with complex anatomy of proximal neck: planning and technical considerations

The purpose of this report was to demonstrate initial Japanese cases of abdominal aortic aneurysm (AAA) with complex anatomy of proximal neck treated using a Zenith fenestrated endograft with branched endovascular technique and to describe the device’s design and technical considerations. Planning and sizing of endografts were performed using high-resolution computed tomography on a three-dimensional workstation. Branched endograft technique combined with reinforced fenestrated device and balloon-expandable stent graft was used in two patients because of challenging morphology for the fenestrated device with a bare stent. Successful exclusion of the aneurysm sac was achieved in both patients with antegrade perfusion in incorporated visceral vessels. Endovascular repair using a fenestrated device with graft material incorporating the visceral arteries is feasible. The combination of the reinforced fenestration and the balloon-expandable stent graft can provide an adequate sealing effect for the compromised anatomy. Initial and midterm results are reported with further follow-up and patient accrual.     

Three-year follow-up of fenestrated thoracoabdominal stent graft bridging an endovascular thoracic stent graft and a surgical abdominal aortic graft

This case report describes repair of a type I endoleak at the distal landing zone of a thoracic aortic stent graft by endovascular placement of a thoracoabdominal fenestrated stent graft (Cook, Brisbane, Australia). The fenestrated stent graft was interposed between a previous abdominal aortic aneurysm (AAA) Gelsoft tube graft (Sulzer Vascutek Ltd, Inchinnan, United Kingdom) and two overlapping Zenith thoracic endografts (Cook Inc, Bloomington, Indiana). Placement was made more complex because the distal thoracic endograft had rotated into a horizontal position. At 3-year clinical and computed tomography (CT) follow-up, continued clinical and radiologic success was shown with no further intervention required.     

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.     

Bifurcated drum occluder endograft for treatment of abdominal aortic aneurysm: an experimental study in dogs

PURPOSE: To evaluate a new, low profile, home-made, bifurcated drum occluder endograft (BDOEG), designed for percutaneous, transcatheter treatment of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: AAA was created in 10 dogs with over-dilated Palmaz stents. To prevent back filling, the lumbar arteries, inferior mesenteric artery, and common internal iliac arteries were embolized. The BDOEG was constructed of a drum occluder device and two PTFE endografts. The drum device consisted of a modified Z stent with Dacron stretched across and held within the ends of the stent, each with two 8 x 6-mm slits through which PTFE endografts were delivered. The PTFE endografts were 8 mm in diameter and 9.5 cm in length. Preloaded, the BDOEG was delivered through a 10-F sheath from both femoral arteries in a three-step procedure. All 10 animals were treated with BDOEG. Aortography was performed immediately, 6 weeks, and 12 weeks after stent-graft placement. Five animals were killed at 6 weeks and five were killed at 3 months. Gross and histologic evaluation was performed. RESULTS: The infrarenal aortic diameters and both external iliac arteries ranged from 8.0 mm to 10.3 mm (mean, 9.4 mm +/- 0.6) and from 5.2 mm to 6.8 mm (mean, 5.8 mm +/- 0.5), respectively. Creation of the AAA was successful in all 10 dogs. AAA diameters ranged from 13.7 mm to 15.9 mm (mean, 14.9 mm +/- 0.7). Complete exclusion of the AAA was achieved immediately after BDOEG placement and aneurysms remained excluded without perigraft leak to the time of killing in all 10 animals. There was a high incidence of aortoiliac limb occlusion. Occlusion of 12 aortoiliac limbs (60%) caused by intimal hyperplasia at the distal end of the endografts in iliac arteries developed in nine animals (90%). In six animals (60%), one limb occluded and, in three animals (30%), there was occlusion of both limbs. CONCLUSION: This study suggests a new approach for treatment of AAA. BDOEG use reduces sheath size for endograft delivery and may eliminate the need for a surgical cut down on femoral arteries. Tapering of the iliac ends of endografts to the size of the artery will be needed to prevent distal intimal hyperplasia.     

Iliac Artery Injury Following Placement of the Memotherm Arterial Stent

Iliac rupture and aneurysm formation at the site of stent placement has rarely been described in the literature. We report four cases, three of iliac rupture, including a delayed rupture, and an aneurysm, with the use of a single type of stent, the Memotherm stent. We believe the design of the stent significantly contributed to damage to the arterial wall and subsequently prevented closure of the arterial tear by balloon tamponade in the two cases where this was attempted. Two patients, one with rupture and one with an aneurysm, were successfully treated with a covered stent obviating surgery and two ruptures resulted in death. We recommend that all interventionists carrying out iliac angioplasty and/or stenting should have access to covered stents for such emergencies.     

Estimation of Abdominal Aortic Aneurysm Rupture Risk with Biomechanical Imaging Markers

PurposeTo evaluate whether the biomechanical marker known as rupture risk equivalent diameter (RRED) was superior to the actual abdominal aortic aneurysm (AAA) diameter in estimating future rupture risk in patients who had undergone pre-rupture computed tomography (CT) angiography.Materials and MethodsA retrospective study was conducted in 13 patients with ruptured AAAs who had undergone CT angiography before and after rupture between 2001 and 2015. The median time between the 2 scans was 731 days. Biomechanical and geometrical markers such as maximal AAA diameter, peak wall stress (PWS), and RRED were calculated with AAA-dedicated software. The main analyses determined whether RRED was higher than the actual diameter and the threshold diameter for elective surgery (55 mm for men, 50 mm for women) in AAAs before and after rupture. Differences between diameter and biomechanical markers before and after rupture were tested with appropriate statistical tests.ResultsRRED before and after rupture was smaller than the actual diameter in 7 of 13 cases. Post-rupture RRED was estimated to be smaller than the threshold diameter for elective repair in 4 cases, again suggesting a low rupture risk. The median PWS before and after rupture was 181.7 kPa (interquartile range [IQR], 152.1–244.2 kPa) and 274.1 kPa (IQR, 172.2–377.2 kPa), respectively.ConclusionsRRED was smaller than the actual diameter in more than half of pre-rupture AAAs, suggesting a lower rupture risk than estimated with the actual diameter. The results suggest that the currently available biomechanical imaging markers might not be ready for use in clinical practice.     

Endovascular Treatment of Ruptured Iliac Aneurysm Previously Treated by Endovascular Means

A patient with a ruptured iliac aneurysm was admitted to the Emergency Department in hypovolemic shock. He had previously undergone surgical treatment for an infrarenal abdominal aortic aneurysm, which was managed with a terminal-terminal Dacron tube graft. Subsequently, he developed two iliac aneurysms, which were treated endovascularly with two wall-grafts in the right and one wall-graft in the left iliac arteries. He suffered chronic renal failure and arterial hypertension. Contrast-enhanced computed tomography showed rupture of the right iliac aneurysm and dislocation of the two wall-grafts. He was treated in an emergency situation with the implantation of an iliac endograft that bridged the two wall-grafts, which resulted in hemostasis and stabilization of his condition. Five days later, in an elective surgical situation, he was treated with the implantation of an aorto-uni-iliac endograft combined with a femoral-femoral bypass. He was discharged 5 days later in good condition. At the 4 year follow-up visit, the endoprosthesis remained in place with no evidence of an endoleak. In conclusion, overlapping of endografts should be avoided, if possible. Strict surveillance of the endovascularly treated patient remains mandatory.     

An Experimental Study of Endovascular Stenting with Special Reference to the Effects on the Aortic Vasa Vasorum

Purpose: To evaluate the effects of bare stents and covered stents on the aortic wall, especially the vasa vasorum. Methods: Eight bare stents and nine covered stents were placed in the infrarenal aorta of nine dogs. The dogs were euthanized at 4–45 weeks after stent placement. The vasa vasorum was evaluated by microstereoscopy with vascular casting, and the histopathology of the aortic wall was examined by light microscopy. Results: In the unstented normal aorta, vasa vasorum nourished the adventitia and the outer media, and the intima and inner media were avascular. In the stented segment, vascular dilatation and proliferation of vasa vasorum, medial atrophy, and intimal hyperplasia were observed, more prominent for covered stents than for bare stents. Conclusion: Intravascular stent placement caused not only medial atrophy and intimal hyperplasia but also proliferation of the vasa vasorum, probably due to hypoxia in the aortic wall. Received: 0/00/00/Accepted: 0/00/00     

Prophylactic Residual Aneurysmal Sac Embolization with Expandable Hydrogel Embolic Devices for Endoleak Prevention: Preliminary Study in Dogs

Objective To explore the feasibility and efficacy of residual aneurysmal sac (RAS) embolization with the expandable hydrogel embolic device (EHED) in prevention of endoleaks in a surgically created and endoluminally treated abdominal aortic aneurysm (AAA).Methods In eight dogs, an AAA was created by means of side-to-side anastomosis between the infrarenal abdominal aorta and inferior vena cava (IVC) with ligation of the IVC above and below the anastomotic end, followed by deployment of an endograft with holes. The RAS was then embolized with the EHED. One animal was killed immediately after RAS embolization and one animal died 12 hr after the procedure. Follow-up aortograms were obtained in six animals after 1 day (1 animal), 2 weeks and 6 months (1 animal), and 8 weeks (4 animals).Results Four animals had no endoleaks on the follow-up aortograms. The remaining two animals with incomplete RAS embolization had moderate type III endoleaks. Type I or II endoleaks were not seen in any animals. Complications included RAS wall penetration by the devices with platinum wires in two animals (nos. 1 and 2), device migration into an aortic circulation through the endograft holes in two animals (nos. 2 and 3) or through distal interstices between the aortic wall and endograft in one animal (no. 8), aortic occlusion in three animals (nos. 3, 7, and 8), and RAS rupture in one animal (no. 7). Histologic examination showed expanded hydrogels occupying the RAS with associated mature or immature organized thrombus, fibrinous thrombus, or degenerate blood cells.Conclusion RAS embolization was feasible with the EHED, although additional modifications to the device are required to avoid complications. Angiographic and histologic results suggested that RAS embolization with the EHED may help in the prevention of endoleaks.     

Endovascular Repair of Narrow Distal Aortas Using an In Situ Fenestration Technique

PurposeTo demonstrate that in situ fenestration (ISF) of an aorto-uni-iliac endograft to treat aortoiliac disease with narrow distal aorta (NDA) vessels is effective and safe.Materials and MethodsData for all patients treated by use of ISF between August 2014 and December 2019 were retrospectively analyzed. The series included 27 patients, aged 70 years ± standard error (SE) 11. The pathologies treated included aortoiliac occlusive disease (n = 16), asymptomatic abdominal aortic aneurysm (n = 8), and a ruptured abdominal aortic aneurysm (n = 3). The technique consisted of deploying an aorto-uni-iliac graft, which was converted into a bifurcated repair through contralateral iliac ISF. The inclusion criteria encompassed the presence of an abdominal aortic aneurysm (diameter of >50 mm, rapid growth, ruptured or symptomatic) associated with NDA or the presence of severe aortoiliac occlusive disease with NDA. NDA is defined as an aortic diameter of <16 mm.ResultsThe mean aortic bifurcation diameter was 11.9 mm ± SE 1.5. In total, 55% of the fenestrated endografts were performed with a multifilament polyester endograft and 45% with expanded polytetrafluoroethylene endograft. Technical success was 100%. Fluoroscopy time was 28 minutes ± SE 12, and 94 mL ± SE 43 of iodinated contrast medium was used. In the postoperative course, a single minor retroperitoneal hematoma was identified. The mean hospital stay was 5 days ± SE 3. At the mean follow-up of 26 months ± SE 22, overall primary patency was 94% and no endoleak was observed at the ISF site.ConclusionsThe ISF technique is safe and effective in the treatment of aortoiliac disease with NDA. Comparisons with alternative techniques are needed to determine the long-term durability.     

Spared flow tract within the mural thrombus of an aortic aneurysm: its pathogenesis and clinical importance

The purpose of this case report is to determine the unique pathogenesis of a "spared flow tract" through a thick mural thrombus of an aortic aneurysm mimicking the penetrating or dissecting tract of an impending or acute rupture of an abdominal aortic aneurysm (AAA) and to discuss its clinical importance. Three blood flow tracts (i.e., spared flow tracts) penetrating to aortic major branches (inferior mesenteric arteries in two and left renal artery in one) through thick mural thrombi of three aortic aneurysms were found on thin section spiral CT scans. Histopathological examination revealed that the tracts were formed by thrombi and partially covered with endothelial cells. In conclusion, spared flow tracts may be pathways continuing to the aortic major branches through thick mural thrombi of aortic aneurysms and are spared from thrombogenesis because of relatively high blood flows. Their pathogenesis is definitely different from penetrating or dissecting tracts within mural thrombi of ruptured AAAs. Spared flow tracts should not be misinterpreted as penetrating or dissecting tracts of impending or acute rupture.     

Translumbar repair of a type II endoleak associated with an aorta-to-left renal vein fistula after aortic stent-graft placement

An abdominal aortic aneurysm (AAA) is a serious medical condition with significant associated morbidity and mortality. Endograft repair of AAAs is a therapy in evolution, but offers promise as a minimally invasive treatment option. Persistent sac pressurization via endoleaks has limited wider application of stent-grafting technology. The present report describes a case of an AAA with rupture into a retroaortic left renal vein that was treated acutely with aortic stent-graft repair. Continued aneurysm enlargement and a large type II endoleak drained by an arteriovenous fistula were subsequently treated via a translumbar approach.     

On the effect of computed tomography resolution to distinguish between abdominal aortic aneurysm wall tissue and calcification: A proof of concept

PurposeThe purpose of this study is to determine the optimal target CT spatial resolution for accurately imaging abdominal aortic aneurysm (AAA) wall characteristics, distinguishing between tissue and calcification components, for an accurate assessment of rupture risk.Materials and methodsRuptured and non-ruptured AAA-wall samples were acquired from eight patients undergoing open surgical aneurysm repair upon institutional review board approval and informed consent was obtained from all patients. Physical measurements of AAA-wall cross-section were made using scanning electron microscopy. Samples were scanned using high resolution micro-CT scanning. A resolution range of 15.5–155 μm was used to quantify the influence of decreasing resolution on wall area measurements, in terms of tissue and calcification. A statistical comparison between the reference resolution (15.5 μm) and multi-detector CT resolution (744 μm) was also made.ResultsElectron microscopy examination of ruptured AAAs revealed extremely thin outer tissue structure <200 μm in radial distribution which is supporting the aneurysm wall along with large areas of adjacent medial calcifications far greater in area than the tissue layer. The spatial resolution of 155 μm is a significant predictor of the reference AAA-wall tissue and calcification area measurements (r = 0.850; p < 0.001; r = 0.999; p < 0.001 respectively). The tissue and calcification area at 155 μm is correct within 8.8% ± 1.86 and 26.13% ± 9.40 respectively with sensitivity of 87.17% when compared to the reference.ConclusionThe inclusion of AAA-wall measurements, through the use of high resolution-CT will elucidate the variations in AAA-wall tissue and calcification distributions across the wall which may help to leverage an improved assessment of AAA rupture risk.     

Extracorporeal expulsion of a vascular endograft used to treat a mycotic aneurysm

A 65-year-old woman with a right common iliac artery mycotic aneurysm and an overlying sacral pressure ulcer was treated with placement of a vascular endograft. The mycotic aneurysm was successfully excluded, but 3 months after the procedure, the endograft was expelled through the wound. Fortunately, the patient had minimal clinical sequelae. This case emphasizes the importance of frequent noninvasive imaging of mycotic aneurysms treated with endografts. A rigorous postoperative imaging protocol is proposed based on the current regimen for abdominal aortic aneurysm surveillance after endograft implantation.     

Case report: Endovascular repair of a ruptured abdominal aortic aneurysm under local anaesthesia

Abdominal aortic aneurysm (AAA) is a common degenerative condition affecting the elderly population. Rupture carries a high overall mortality. Elective endovascular stent graft repair is well described. We describe a patient with ruptured AAA and co-morbid conditions making him unfit for surgery and general or epidural anaesthesia, who was successfully treated by endovascular stent graft under local anaesthesia.