Transluminal stent graft repair with Wallgraft endoprosthesis in a porcine arteriovenous graft pseudoaneurysm model

Intimal growth on the luminal surface of arteriovenous grafts in rats

BACKGROUND

Endothelial cells are known to grow on the luminal surface of arteriovenous grafts (AVGs) used in hemodialysis. Although endothelial cells are important for preventing infection, a detailed growth of endothelial cells in AVGs is unknown. This study sought to create a simpler animal model of AVGs and to investigate how endothelial cells form on the luminal surface.

METHODS

Polyethylene grafts were placed between the cervical artery and vein of Wistar rats. The grafts were removed at 6 h, 24 h, 3 days, or 7 days after placement. The luminal surface was observed under optical and polarizing microscopy and stained with endothelial cell markers (LEL, CD31), the progenitor cell marker CD34, and the macrophage marker ED-1.

RESULTS

Microscopy demonstrated many diffuse vascular endothelial cells on the luminal surface of AVGs after placement. While there was no difference in the number of LEL-positive cells between the arterial side (AS) and venous side (VS) at 6 h or 7 days, there were significantly more of these cells on the VS at both 24 h and 3 days (p < 0.05). Analysis at 24 h showed some CD31-positive cells and few CD34-positive cells.

CONCLUSIONS

This was the first study to use a simple rat model of AVG placement. Endothelial cell formation was initially more active on the VS than on the AS, but these cells subsequently increased in number across the luminal surface. Future clinical studies might contribute clinically by confirming whether AS versus VS puncture results in different infection rates.

Transforming Growth Factor-β1 Inhibits Pseudoaneurysm Formation After Aortic Patch Angioplasty

OBJECTIVE

Pseudoaneurysms remain a significant complication after vascular procedures. We hypothesized that TGF-β (transforming growth factor-β) signaling plays a mechanistic role in the development of pseudoaneurysms.

APPROACH AND RESULTS

Rat aortic pericardial patch angioplasty was associated with a high incidence (88%) of pseudoaneurysms at 30 days, with increased smad2 phosphorylation in small pseudoaneurysms but not in large pseudoaneurysms; TGF-β1 receptors were increased in small pseudoaneurysms and preserved in large pseudoaneurysms. Delivery of TGF-β1 via nanoparticles covalently bonded to the patch stimulated smad2 phosphorylation both in vitro and in vivo and significantly decreased pseudoaneurysm formation (6.7%). Inhibition of TGF-β1 signaling with SB431542 decreased smad2 phosphorylation both in vitro and in vivo and significantly induced pseudoaneurysm formation by day 7 (66.7%).

CONCLUSIONS

Normal healing after aortic patch angioplasty is associated with increased TGF-β1 signaling, and recruitment of smad2 signaling may limit pseudoaneurysm formation; loss of TGF-β1 signaling is associated with the formation of large pseudoaneurysms. Enhancement of TGF-β1 signaling may be a potential mechanism to limit pseudoaneurysm formation after vascular intervention.

Endograft salvage of hemodialysis accesses threatened by pseudoaneurysms

OBJECTIVE

Currently, no formal practice guidelines exist regarding the use of endografts to exclude hemodialysis access pseudoaneurysms and prolong access lifespan in dialysis patients. We evaluated the efficacy of percutaneous endograft placement for exclusion of hemodialysis access pseudoaneurysms.

METHODS

Between July 2005 and October 2009, 32 patients were prospectively evaluated. Twenty-four patients were actively enrolled in the study based upon clinical and ultrasonographic evaluation of their hemodialysis accesses. Self-expanding covered endografts were placed percutaneously to exclude access pseudoaneurysms. Patients were evaluated at 2 and 6 months to assess for graft patency, access or outflow stenosis, endoleak, or stent graft migration.

RESULTS

No procedural complications resulted from these interventions. An average of 1.8 endografts was placed per patient, with patients requiring between 1 and 3 endografts to exclude pseudoaneurysms. Primary-assisted patency was 83% at completed 2-month follow-up and 54% at 6-month follow-up. At 12 months, primary-assisted patency was 50%. Eleven patients left the study before 6-month follow-up: five (21%) required explantation secondary to infection between 1 and 4 months; three (13%) were lost to follow-up; two (8%) died of unrelated causes; and 1 requested explantation citing pain from the "stent poking the vein." Mean time to explantation secondary to infection was 2.4 months. Mean duration of patency was 17.6 months with a range from 0 to 76 months. Mean duration of patency for patients who completed 6-month follow-up was 28.7 months. The longest duration of patency is 6 years 4 months, after stent fracture and subsequent placement of a new stent at 6 years 2 months. One other incident of stent fracture occurred at 36 months. Dialysis patterns were not interrupted in either patient.

CONCLUSIONS

The long-term results demonstrate that endograft salvage of failing hemodialysis accesses is a viable and safe alternative to open surgical revision that excludes pseudoaneurysms while maintaining uninterrupted access patency. A larger sample size and longer follow-up are needed to support the study data.

Endovascular treatment of hemodialysis access pseudoaneurysms

OBJECTIVE

Pseudoaneurysm (PSA) formation is a complication of hemodialysis access. Open repair requires PSA resection, interposition graft placement, and insertion of a catheter as a bridge. Endovascular stent graft repair is an alternative that permits immediate use of the access site. The objective of this study was to determine the efficacy of stent grafts for repair of arteriovenous fistula and arteriovenous graft PSA.

METHODS

A retrospective review of medical records from October 2007 to March 2011 revealed 24 patients with a PSA who underwent endovascular repair using a stent graft. Indications for repair included PSA with symptoms (n = 11), PSA with skin erosion (n = 8), PSA with failed hemodialysis (n = 3), and PSA after balloon angioplasty of a stenosis (n = 2). Outcome measures were technical success, 30-day and 180-day patency, secondary interventions, and complications. All the statistical analyses were conducted by using software SAS 9.1 (SAS, SAS Institute, Gary, NC).

RESULTS

Twenty-seven self-expanding stent grafts (Viabahn, W. L. Gore, n = 25; Fluency, Bard, n = 2) were used to treat hemodialysis access (arteriovenous graft, n = 13; arteriovenous fistula, n = 11) PSA in 24 patients (16 females; mean age, 55.7 years; mean body mass index, 28.4; mean PSA diameter, 19.5 mm). Comorbidities included hypertension (n = 22; 91.7%), diabetes mellitus (n = 8; 33.3%), and coronary artery disease (n = 4; 16.67%). The median time from access creation to repair was 455 days. The technical success rate was 100%. Balloon angioplasty of an outflow stenosis was performed in 56% of stent grafts. The 30- and 180-day patency rate was 100% and 69.2%, respectively. Three secondary interventions were performed for treatment of unrelated stenosis. Treatment failure occurred in five (18.5%) stent grafts due to infection (n = 3) and thrombosis (n = 2). Treatment of PSA with skin erosion was associated with failure due to infection (odds ratio, 5.0; 95% confidence interval, .38, 66.01). The remaining 22 (81.5%) stent grafts remain patent. The mean follow-up time was 268.9 days (median, 97.5).

CONCLUSIONS

Endovascular therapy is an effective and durable treatment option for patients with dialysis access PSAs. This technique permits immediate use of the hemodialysis access site as well as identification and treatment of associated stenosis. It may be considered as an alternative to open repair in patients who are anatomically suitable candidates.

Role of stent grafts for the treatment of failing hemodialysis accesses

Covered stents or stent grafts are exciting new products with multiple applications for patients with vascular disease, including hemodialysis access-related complications. Although most of the current uses of stent grafts in these settings are "off-label" (ie, not approved by the US Food and Drug Administration) several studies are currently underway to provide the necessary data to support their application. It is clear that stent grafts provide a rapid, effective means for endovascular repair of ruptured access vessels. The commercially available devices and their current applications for treating access-related complications, including aneurysms/pseudoaneurysms, venous outflow stenoses, cephalic arch lesions, ruptures, and diffuse access stenoses, will be reviewed in this article. Available data are reported along with our current clinical practice and algorithms.

Aneurysm of the tibial-saphenous fistula in hemodialysis patient: the results of surgical treatment

Arteriovenous fistulas are widely used for hemodialysis patients with end-stage renal failure. Due to the lack of suitable veins because of the arteriovenous fistulas previously opened in the upper extremity, alternative access routes are being tested. Few complications of long-term alternative arteriovenous fistulas have been reported in the literature. We report the results of surgical repairs of aneurysms that occurred on anterior tibial-saphenous arteriovenous fistulas (along the vein) in patients with end-stage renal disease after 5 years on hemodialysis.

Treatment of hemodialysis graft pseudoaneurysms with stent grafts: institutional experience and review of the literature

Hemodialysis access grafts are an important component of the treatment of patients with renal failure. Because access sites are limited, maximizing graft lifespan is of major importance to dialysis patients. Pseudoaneurysm formation is a rare, but important complication potentially limiting the longevity of dialysis grafts. With rapidly advancing technology, placement of stent grafts in patients with end-stage renal disease is an important step in prolonging the life of the graft. We conducted a review of the literature regarding stent-graft use for hemodialysis access. In addition, we looked at our experience utilizing the Viabahn(®) (W. L. Gore & Associates, Newark, DE) stent graft in pseudoaneurysm repair. Our patients achieved primary patency of their grafts for 1, 5, and 9 months, respectively. No complications related to stent-graft implementation have been encountered in six stent-graft implants over the course of 29 months.

Stent graft treatment for hemodialysis access aneurysms

BACKGROUND

Aneurysms that develop in arteriovenous accesses as a result of repeated punctures are sometimes complicated by infection or ischemia causing sloughing of the overlying skin, which may endanger the access and risk major bleeding and other complications. Surgical revision may necessitate the temporary use of a central venous catheter until dialysis can be resumed via the access. We used stent grafts in selected patients for the exclusion of access aneurysms.

METHODS

Twenty of 63 patients requiring access revision for complication of an aneurysm from February 2005 to December 2009 underwent ambulatory endovascular stent graft deployment. Indications included signs of impending rupture, questionable viability of overlying skin, pain, infection, and limitation of cannulation sites by the size or number of the aneurysms. Endovascular treatment always included angioplasty of associated outflow or central vein stenoses at the same ambulatory session.

RESULTS

Twenty patients with complicated access aneurysms were treated by endovascular stent graft exclusion at an average of 4.8 ± 4.3 years (range, 0.2 to 16.1 years) after access construction: nine graft pseudoaneurysms, nine native vein aneurysms, and two acute iatrogenic pseudoaneurysms. Six patients had skin erosion over the aneurysm, and 12 had painful aneurysms and clinical signs of compromised blood supply to the skin. Another two patients with an acute giant false aneurysm occurring during endovascular procedures were treated in the same interventional session by the stenting technique to control bleeding. All the aneurysms underwent endovascular exclusion without complications. Only one infected puncture site failed to heal within 2 months of stenting and was closed surgically 10 months later due to persistent localized graft infection, but with no further bleeding episodes. Only one aneurysm did not reabsorb within 3 months. Patients with painful skin ischemia had immediate pain relief. All patients also had stenosis in the draining veins necessitating additional percutaneous transluminal angioplasty. Only one patient required hospitalization (for intravenous antibiotic treatment of staphylococcal sepsis). No patients required a central catheter for hemodialysis. One access occluded due to cephalic arch stenosis in a noncompliant patient. Functional patency was 87% at 12 months, with a median follow-up of 15 months (range, 6.3 to 55.5 months).

CONCLUSION

Endovascular treatment with stent grafts in complicated access aneurysms is a simple, safe and rapid ambulatory procedure that enables treatment of both the aneurysm and its accompanying draining vein stenosis. It enables continued cannulation of the existing access and avoids the use of central catheters.

Interventional radiology in the diagnosis, management, and follow-up of pseudoaneurysms

Arterial wall disruption, as a consequence of inflammation/infection, trauma (penetrating or blunt), or iatrogenic causes, may result in pseudoaneurysm formation. Currently, iatrogenic causes are increasing as a result of the growth of endovascular intervention. The frequency of other causes also seems to be increasing, but this may simply be the result of increased diagnosis by better imaging techniques, such as multidetector contrast-enhanced computed tomography. Clinically, pseudoaneurysms may be silent, may present with local or systemic signs, or can rupture with catastrophic consequences. Open surgical repair, previously the mainstay of treatment, has largely been replaced by image-guided occlusion methods. On the basis of an experience of over 100 pseudoaneurysms, treatments at various anatomical sites, imaging modalities used for accurate diagnosis, current changing therapeutic options for pseudoaneurysm management, approved embolization agents, and clinical follow-up requirements to ensure adequate treatment will be discussed. Image-guided direct percutaneous and endovascular embolization of pseudoaneurysms are established treatment options with favorable success rates and minimal morbidity. The pendulum has now swung from invasive surgical repair of pseudoaneurysms to that of image-guided interventional radiology.

Effect of catheter-directed arterial embolization and laparoscopic endovascular stapling on stapled vessel integrity in a porcine model

Arterial embolization is a frequently performed adjunctive maneuver prior to laparoscopic splenectomy or nephrectomy to facilitate laparoscopic dissection and reduce intraoperative bleeding. However, little is known regarding the effect of laparoscopic stapling across thrombosed vessels with imbedded embolic materials. This study analyzed the stapled line integrity by comparing visceral arteries treated with either platinum coils or polyvinyl alcohol (PVA) particles. Using a porcine model, 30 visceral vessels including splenic and renal arteries were treated with either coil or PVA embolization, which was followed by laparoscopic stapling. Vessel integrity and bursting pressure analysis was performed using an in vitro flow circuitry. The mean bursting pressure of the coil and the PVA group was 158 +/- 56 and 350 +/- 34 mm Hg, respectively (p < .001). The lowest bursting pressure in the coil and the PVA group was 70 and 280 mm Hg, respectively. The highest bursting pressure in the coil and the PVA group was 225 and 420 mm Hg, respectively. The bursting pressure in the splenic artery between the PVA and the coil group was 345 +/- 29 and 150 +/- 54 mm Hg, respectively (p < .001). Significant difference in the bursting pressure in the renal artery was noted in the PVA and the coil group, which was 350 +/- 40 and 160 +/- 40 mm Hg, respectively (p < .001). Our findings showed that preoperative coil embolization followed by laparoscopic vessel stapling sustained a poor busting pressure. Such a practice appears to be unsafe based on our findings and should be performed with caution in a clinical setting.

Endovascular Repair of Hemodialysis Graft-Related Pseudoaneurysm: An Alternative Treatment Strategy in Salvaging Failing Dialysis Access

Introduction Hemodialysis access—related pseudoaneurysm is a known complication in patients requiring hemodialysis via prosthetic arteriovenous grafts (AVGs). The traditional treatment strategy of AVG-related pseudoaneurysms is either AVG ligation or interposition replacement with another prosthetic graft segment or autogenous veins.

Patients and methods From June 2002 to August 2007, 32 self-expanding stent grafts were implanted in 26 patients with AVG pseudoaneurysms. Indications for treatment consisted of large AVG pseudoaneurysm size, localized pain at pseudoaneurysm site, enlarging pseudoaneurysm, and skin site breakdown. AVG pseudoaneurysm exclusion was accomplished with Wallgrafts, Viabahn endoprosthesis, and Fluency endograft. Technical success was achieved in all patients. Nineteen patients experienced a marked decrease in the size of their pseudoaneurysm following endograft exclusion. Successful hemodialysis was resumed through endograft-excluded AVG in all patients within 48 hours.

Conclusions Endoluminal exclusion of AVG pseudoaneurysms using endografts is a safe and effective treatment strategy in patients with hemodialysis-related pseudoaneurysm.

Role of Stents and Stent Grafts in Management of Hemodialysis Access Complications

Different types of complications may occur during a percutaneous vascular access procedure and the majority of these complications are caused by balloon angioplasty. These balloon angioplasty-induced complications include venous rupture, venous dissection, and the development of an acute pseudoaneurysm. Balloon tamponade is the traditional percutaneous technique for management of these complications. However, insertion of a stent or stent graft has become an increasingly popular method to quickly and effectively repair a venous injury. A stent or stent graft may provide a more effective and durable method to treat balloon angioplasty-induced complications. Unfortunately, there are few, if any, clinical studies to substantiate the advantages and cost-effectiveness of these devices and so their use remains controversial.

Use of Stent Grafts to Repair Hemodialysis Graft–related Pseudoaneurysms

PURPOSE

To review the author's early experience with stent grafts to repair hemodialysis graft-related pseudoaneurysms.

MATERIALS AND METHODS

Eleven patients had undergone insertion of a stent graft to repair a pseudoaneurysm arising from a PTFE hemodialysis graft. The study group consists of seven women and four men with a mean age of 50.7 years. The primary indications for stent graft placement were: rapid enlargement of a pseudoaneurysm in four patients, difficulty with cannulating the graft in two patients, high risk of acute rupture in three patients, persistent bleeding from the pseudoaneurysm in one patient, and one was incidentally discovered during diagnostic fistulography. In 10 of the 11 patients, the pseudoaneurysm arose from the arterial limb of a loop-configuration graft. A stent graft was successfully deployed in all patients. The radiological and surgical records were reviewed.

RESULTS

The Viabahn endoprosthesis was successfully inserted and deployed in all 11 patients. Six patients underwent subsequent interventions, which ended primary patency at 39 days, 40 days, 63 days, 104 days, 120 days, and 327 days after insertion of the stent graft. However, no additional interventions have been performed in five patients and primary patency continues. In these five patients the interval of continuing primary patency is 55 days, 92 days, 103 days, 139 days, and 196 days. In this small group of patients the primary patency rate is 71% at 3 months and 20% at 6 months.

DISCUSSION

Early experience has demonstrated that a stent graft can successfully exclude a pseudoaneurysm from a hemodialysis graft and may prevent further enlargement and decrease the likelihood of rupture. However, in two of these 11 patients, the large pseudoaneurysm remained problematic and required subsequent surgical repair.

Surgical Management of Giant Aneurysms Complicating Arteriovenous Fistulae

The creation of an arteriovenous fistula (AVF) is frequently used to achieve easier access for haemodialysis in patients with chronic renal insufficiency. The most frequent late complication of AVFs is aneurysm formation, which carries the risk of spontaneous rupture. This study reports on 18 patients with giant aneurysms that developed on antebrachial AVFs who were operated on over a period of 6 years. Colour duplex ultrasonographic examination of the upper extremity was performed in all but one patient in the preoperative period.

Surgical management included resection of the aneurysm and re-establishment of arterial continuity. There were no complications such as infection, ischaemic extremity loss, neurological sequelae or mortality. Colour duplex ultrasonographic examinations after 6 months were all normal. The mean follow-up period was 29.1 months (range 7 − 50 months). There were no additional vascular complications observed during follow-up. Early surgical intervention is the recommended treatment of choice for giant aneurysm complicating antebrachial AVF.