Impact of transrenal aortic endograft placement on endovascular graft repair of abdominal aortic aneurysms

Transrenal fixation of aortic endografts: intermediate follow-up of a single-center experience

PURPOSE

To examine the fate of the renal ostia following transrenal fixation of endovascular aortic stent-grafts.

METHODS

Thirty-five patients (29 men; mean age 75 years) undergoing endovascular repair for abdominal aortic aneurysms (AAAs) had transrenal fixation of the uncovered proximal stent due to a short (< 1.5 cm long) or conical neck or a periprocedural endoleak. Eighteen (51%) patients were hypertensive; 7 (20%) had renal artery stenoses (RAS). Outcome measures included blood pressure, serum creatinine, computed tomography, and renal artery duplex scans.

RESULTS

Two patients with > or = 60% RAS had renal stents placed during the endograft procedure; the other 5 RAS patients were normotensive and their renal lesions were not treated. Overall technical success was 82.9% (29/35). One (2.9%) case was converted due to graft twisting. There were 5 (14.2%) early endoleaks. Transient postoperative creatinine elevations were observed in 5 (14.2%) cases. Over a median 11-month period (range 2-24), no secondary endoleaks or silent renal artery occlusions were seen. One normotensive patient with an untreated > or = 60% renal lesion developed hypertension and severe stenosis (99%) at 4 months; stenting through the interstices of the transrenal stent was performed. No disease progression was seen in the other 6 RAS patients.

CONCLUSIONS

In the intermediate period, transrenal fixation appears to have no adverse effects on renal blood flow. Moreover, in patients with no evidence of renal disease or preoperative RAS < 60%, it does not precipitate or cause progression of renal stenosis. However, patients with preoperatively documented RAS > or = 60% are a concern and mandate further study.

Patient selection for endovascular repair of aortoiliac aneurysms

PURPOSE

This study was conducted to establish criteria to aid in the selection of patients for endovascular repair of aorto-iliac aneurysms.

METHODS

Characterization of pertinent factors used to determine whether a patient is eligible to undergo stent-graft repair of an aorto-iliac aneurysm.

PRINCIPAL FINDINGS AND CONCLUSIONS

The determinant factor that dictates whether or not one is eligible to undergo endovascular repair of aorto-iliac aneurysm is the arterial anatomy of the affected area and its surrounding vessels. Some of the initial limitations imposed in this technology have changed such as an acceptance of much shorter neck than initially conceptualized, by the use of supra-renal stent deployment. However, unsolved issues remain regarding the differentiation of thrombus and atherosclerotic plaque in the infra-renal aortic region, iliac artery disease, and the need to have an enhanced flexibility of the delivery system for proper deployment in tortuous aortic necks. The question of long-term device durability remains the most important issue that has to be taken into consideration before one chooses minimally invasive endovascular approaches.

Safety and efficacy of high-dose adenosine-induced asystole during endovascular AAA repair

PURPOSE

To assess the safety and efficacy of high-dose adenosine administration to increase the precision of endovascular abdominal aortic aneurysm (AAA) repair using a balloon deployed stent-graft.

METHODS

From January 1997 to March 1999, 98 AAA patients (79 men; mean age 71 years, range 62-91) were treated with balloon-expandable stent-grafts under an approved protocol. After placing a temporary transvenous ventricular lead or an external transthoracic pacing electrode, adenosine (24 mg initially) was administered in an escalating dose fashion to induce at least 10 seconds of asystole, during which the proximal stent was expanded.

RESULTS

Adenosine dosages ranged from 24 to 90 mg (median 24 mg). Nine (9.2%) self-limiting cardiac events were observed: 2 (2.0%) episodes of transient myocardial ischemia, 2 (2.0%) cases of atrial fibrillation requiring cardioversion, 1 (1.0%) transient left bundle branch block lasting <10 seconds, and 4 (4.1%) prolonged periods of asystole requiring temporary pacemaker activation. There were no cases of bronchospasm or worsening obstructive pulmonary disease, and no patients required inotropic support after adenosine-induced asystole.

CONCLUSIONS

Cardiac events following adenosine-induced asystole are infrequent, mild, and easily treated. The perioperative use of high-dose adenosine to ensure precise stent-graft placement appears to be a safe method of inducing temporary asystole during endovascular aortic repair.

Aortic stent-grafting with transrenal fixation: use of newly designed spiral Z-stent endograft

PURPOSE

To evaluate the feasibility and efficacy of a newly designed stent-graft placed across the renal arteries for exclusion of abdominal aortic aneurysms (AAAs) with short or tortuous proximal necks.

METHODS

Among a group of AAA patients treated with endovascular grafting, 5 had tortuous proximal necks and 13 had necks <20 mm (mean 13 mm). In these 18 cases, a 2- to 3-cm uncovered segment of the stent-graft was placed transrenally using a catheter inserted into the renal artery as a guide for graft margin positioning. A newly designed stent-graft was constructed from a custom-made spiral Z-stent covered with a thin-walled Dacron material; the endografts were deployed through 16-F (aortoaortic model) or 18-F sheaths (bifurcated devices). Renal function was assessed by preoperative and postoperative measurement of urea nitrogen and creatinine. Aneurysm exclusion and renal artery patency were evaluated during follow-up using spiral computed tomography and angiography.

RESULTS

The stent-grafts were correctly placed at the intended site in all 18 patients. Renal function was not affected except transiently in 1 patient who developed bilateral renal artery stenoses 24 hours after the procedure; Palmaz stents were deployed in each renal artery to reestablish satisfactory blood flow. Of the 33 renal arteries crossed by the bare stent-graft segment, all were patent over a mean 14-month follow-up (range 7-24), including the patient with Palmaz stents implanted for postprocedural renal stenosis. Complete aneurysm exclusion was maintained in 15 (83%) of 18 patients; proximal leaks persisted in 3 patients, including 2 with severely angled proximal necks.

CONCLUSIONS

Transrenal placement of the uncovered leading edge of custom-made spiral Z-stent-based endografts appears feasible and clinically effective in the treatment of AAAs with short or tortuous proximal necks.

Placement of a fenestrated Palmaz stent across the renal arteries. Feasibility and outcome in an animal study

OBJECTIVES

To investigate the feasibility of placing stents across renal arteries. Design we have studied in pigs: (i) the feasibility of accurately placing a fenestrated stent in front of one renal ostium; (ii) the short-term effects on renal arteries and function after the placement of such a fenestrated stent.

MATERIALS AND METHODS

Eight fenestrated Palmaz stents were placed over pigs' renal ostia under fluoroscopy. Five weeks later, angiograms were performed and the animals were sacrificed. Proliferation of the healing tissues over the ostia was measured and analysed by microscopy. Serum creatinine was measured prior to all angiograms and at 5 weeks.

RESULTS

All eight stents were correctly placed. One stent later migrated and was excluded from the study. One pig died at day 1. Gross examination confirmed the correct placement of the fenestrations in four pigs out of seven (57%). In the six remaining pigs, at 5 weeks, there was no angiographic evidence of stent misplacement and all the kidneys were fully perfused. Nine renal ostia were covered by struts and neointima with a mean area of coverage of 38+/-5% altogether. No tissue proliferation was observed over the three renal ostia located in front of the fenestration. Serum creatinine did not significantly increase at 5 weeks.

CONCLUSION

Creating a fenestration in a stent for renal arteries may be worth while in order to avoid neointimal covering of the renal ostia. However, accurate placement of such a fenestrated stent remains a difficult task.

Malpositioned or dislocated aortic endoprostheses: repositioning using percutaneous pull-down maneuvers

PURPOSE

To present the capabilities and potential complications of 2 percutaneous techniques for repositioning malpositioned or dislodged aortic endografts.

METHODS

Seven male patients (median age 67.9 years, range 59 to 78) required correction of misplaced or dislocated endografts in the thoracic (n = 1) or infrarenal abdominal aorta (n = 6). In 1 patient, an infrarenal bifurcated stent-graft was mistakenly deployed across a renal artery; repositioning was accomplished by tugging caudally on a guidewire placed across the endograft bifurcation and exteriorized from both femoral arteries. An inflated balloon catheter was used to reposition 3 dislocated aortic devices (1 thoracic, 2 infrarenal) and 3 iliac graft limbs that had disconnected from the main graft body 6 to 12 months after implantation.

RESULTS

Repositioning maneuvers were successful in all cases, with the devices being moved from 5 to 27 mm (median 7.8 mm). There were no procedure-related complications.

CONCLUSIONS

Nonsurgical repositioning of misplaced aortic prostheses is technically feasible in individual cases. The risk associated with the procedure, however, cannot yet be evaluated.

Anatomical importance of infrarenal aortic branches in conventional and endovascular surgery: a review

Minimally invasive or catheter-directed, endoluminal stent-graft treatment of abdominal aortic aneurysms (AAA) is a novel and important advance in the armamentarium of the vascular surgeon and interventional therapist. Provided adequate training is available, infrastructure is optimal, and patient selection correct, successful exclusion of AAA can safely and effectively be achieved with low morbidity and mortality by this lesser invasive technique. An important Achilles heel of endovascular repair (EVR) of AAA is back bleeding or endoleak formation due to incomplete sealing or bridging of aortic branches ostia by endoluminal stents. Significant, recurrent, and persistent retroleaks, a topic of clinical interest, are related to either incompletely sealed-off inferior mesenteric and/or lumbar arteries. The optimal method to diagnose and manage these endoleaks is currently in a state of evolution. In the process of stent-graft treatment of AAA, other important aortic branches are also bridged that may potentially present with the sequelae of peripheral ischemia. This review re-emphasizes the anatomical and clinical importance of abdominal aortic branches relevant to conventional aortic surgery and EVR of AAA.

Endovascular repair of abdominal aortic aneurysm using a pararenal fenestrated stent-graft

PURPOSE

To report an unusual case of endovascular abdominal aortic aneurysm (AAA) exclusion in which a fenestrated stent-graft was used to seal a proximal Type I endoleak.

METHODS AND RESULTS

An 84-year-old man with a 6.0-cm AAA underwent an aortomonoiliac aneurysm exclusion procedure that was complicated by a proximal endoleak. Because the patient had no right kidney, an additional stent-graft was designed to cover the right renal artery stump while preserving left renal perfusion through a fenestration in the graft material. This approach was successful in obliterating the endoleak around the proximal attachment site, but flow through the lumbar arteries remained.

CONCLUSIONS

The use of a fenestrated stent-graft is feasible, but the type of fenestration in this case has limited applicability owing to the rarity of patients with suitable anatomy.

Custom bifurcated stent-graft for abdominal aortic aneurysms: initial experience

PURPOSE

To describe a custom bifurcated stent-graft for possible treatment of abdominal aortic aneurysm (AAA).

MATERIALS AND METHODS

Five male patients (mean age, 76 +/- 6 years), who had AAA (mean diameter, 4.7 +/- 0.4 cm) and who were considered to be at high risk for conventional surgery, were treated with a custom modular bifurcated stent-graft constructed with bifurcated 24-mm x 12-mm (upper body diameter x iliac limb diameter) Cooley Veri-Soft Woven polyester grafts and Gianturco-Rösch Z stents. The stent-graft body was delivered through 20-22-F sheaths, and the contralateral iliac limb was delivered through a 16-F sheath by means of surgical exposure of the common femoral arteries. A flared distal limb extender (12 mm to 14 mm) was created for one patient to accommodate a large common iliac artery.

RESULTS

Stent-grafts were successfully deployed without complications in all five patients. There were no proximal or distal leaks. A lumbar-to-inferior mesenteric artery leak was seen in one patient at 24 hours. At 6-month follow-up, all devices were intact, with complete exclusion and shrinkage of the aneurysm in four of five patients. Aneurysm size remained stable in the one patient with a lumbar-to-inferior mesenteric artery leak.

CONCLUSION

A custom, bifurcated stent-graft was utilized for endovascular treatment of AAA. Long-term follow-up is necessary for the device.

Endovascular repair of abdominal aortic aneurysms in patients with congenital renal vascular anomalies

PURPOSE

The endovascular repair of abdominal aortic aneurysms (AAAs) has been suggested as an alternative to conventional aortic reconstruction. The presence of anomalous renal vascular anatomy frequently necessitates special planning during conventional aortic replacement and may also create unique challenges for endovascular repair. We analyzed our experience with 24 patients with variant renal vascular anatomies who underwent treatment with aortic endografts to determine the safety and efficacy of this technique in this population.

METHODS

During a 6-year period, 204 patients underwent aortic endograft procedures, 24 (11.8%) of whom had variations in renal vascular anatomy. There were 19 men and five women. Each of the 24 patients had variant renal vascular anatomy, which was defined by the presence of multiple renal arteries (n = 32), with or without a renal parenchymal anomaly (horseshoe or solitary pelvic kidney). Twenty patients underwent aneurysm repair with balloon expandable polytetrafluoroethylene grafts, and the remaining patients underwent endograft placement with self-expanding attachment systems. Eighteen patients underwent exclusion and presumed thrombosis of anomalous renal branches to effectively attach the aortic endograft. The decision to sacrifice a supernumerary artery was made on the basis of the vessel size (<3 mm), the absence of coexisting renal insufficiency, and the expectation for successful aneurysm exclusion.

RESULTS

The successful exclusion of the AAAs was achieved in all the patients, with the loss of a total of 17 renal artery branches in 12 patients. Small segmental renal infarcts (<20%) were detected in only six of the 12 patients with follow-up computed tomographic scan results, despite angiographic evidence of vessel occlusion at the time of endografting. No evidence of new onset hypertension or changes in antihypertensive medication was seen in this group. No retrograde endoleaks were detected through the excluded renal branches on late follow-up computed tomographic scans. Serum creatinine levels before and after endografting were unchanged after the exclusion of the AAA in all but one patient with multiple renal branches. One patient had a transient rise in serum creatinine level presumed to be caused by contrast nephropathy.

CONCLUSION

On the basis of this experience, we recommend the consideration of endovascular grafting for patients with AAAs and anomalous renal vessels when the main renal vascular anatomy can be preserved and when the loss of only small branches (<3 mm) is necessitated in patients with otherwise normal renal functions.

Early clinical results and studies of aortic aneurysm morphology after endovascular repair

Endovascular repair is a feasible treatment alternative with favorable short-term results compared with standard operations. Nonrandomized, multicenter trials already in progress should help to define the role of endovascular grafting in the treatment of patients who are otherwise candidates for conventional repair. Long-term follow-up studies will test the durability of the procedure, including clinical repercussions of late endoleaks and migration related to slow alterations in aortic morphology, such as neck dilation and aortic shortening. More research is needed into long-term aortic morphologic changes; further insights into these changes may allow subclinical prediction of clinical events and permit intervention before a catastrophic failure. How great an advantage this procedure has over observation in high-risk patients for whom no open surgical alternative is available is also unknown because the overall mortality of this patient cohort may mitigate any treatment benefits. In today's cost-conscious world, the viability of this new technology may be dependent on balancing the short-term benefits of this procedure against its associated requirements for monitoring and subsequent reinterventions.

Endovascular repair of abdominal aortic aneurysm using the EVT device: limited increased utilization with availability of a bifurcated graft

PURPOSE

To determine if the availability of a bifurcated graft would increase the percentage of patients eligible for endovascular repair of abdominal aortic aneurysms (AAAs).

METHODS

One hundred eighty-five consecutive patients were evaluated prospectively for endovascular AAA repair at a university referral center. Data were collected on eligibility for tube or bifurcated endovascular grafts, reasons for exclusion, aneurysm morphology, and the interventions performed.

RESULTS

Forty-six (25%) patients were eligible for endovascular treatment using the first-generation Endovascular Technologies (EVT) system: 19 (10%) for a tube graft and 27 (15%) for a bifurcated device. An unsuitable proximal neck was the reason for exclusion in 48% of patients (excess diameter in 27%, inadequate length in 21%). Unsuitable iliac configuration was present in 41% of those excluded; 29% of the common iliac arteries were enlarged or aneurysmal, while 12% were small or tortuous.

CONCLUSIONS

Although a bifurcated graft more than doubles the eligibility of AAA patients for endovascular repair, the configuration of the proximal neck and iliac disease excluded the majority of AAA patients from endovascular therapy using the first generation EVT device.