Suprarenal endograft fixation avoids adverse outcomes associated with aortic neck angulation.

The advent of endovascular therapy has had a profound impact on repair of abdominal aortic aneurysms (AAA). Prudent patient selection, particularly in regard to unfavorable anatomy, is emerging as perhaps the most important determinant of endovascular abdominal aortic aneurysm repair (EVAR) outcome. The aim of this study was to examine the association of one such anatomic factor, proximal aortic neck angulation, with the incidence of adverse events following EVAR. Prospectively collected data on 289 EVAR repairs with the Talent endograft (Medtronic, Inc., Minneapolis, MN) from March 1998 to June 2000 were analyzed. Stent graft-specific adverse events studied were migration, endoleak, kinking, thrombosis, and AAA expansion. Computed tomography (CT) scanning with three-dimensional post-processing and/or aortography was used to measure aortic neck angle. Patients were categorized into one of four groups according to their neck angle: I (0-10 degrees); II (11-39 degrees); III (40-59 degrees); or IV (60-85 degrees). Outcomes were evaluated by chi-squared analysis and ANOVA. There was a direct correlation between AAA diameter and neck angle (p = 0.002). There was no difference in endoleak rate (p = 0.877), stent migration (p = 0.850), or AAA expansion rate (p = 0.599) between groups. Device kinking >45 degrees was associated with neck angulation > or = 60 degrees (p = 0.013), but not with other adverse outcomes. The average neck angle was 30 degrees in patients with endoleaks and 31 degrees in patients without endoleaks. Increasing aortic neck angulation was not associated with the selected adverse outcomes within 1 year following EVAR with the Talent stent graft using suprarenal fixation with the exception of graft kinking. This may be related to the graft design that permits suprarenal aortic fixatiou of the proximal stent graft, Whether severe degrees of angulation of 60 degrees or greater can be safely treated with suprarenal fixation requires further study.

Gender differences in blood velocities across carotid stenoses.

OBJECTIVES: Carotid duplex scanning is the standard test for documenting carotid disease. Carotid endarterectomy effectively reduces stroke in selected patients with carotid artery disease. Data from large national randomized trials suggest that the benefits of CEA may be gender dependent. Because many diagnoses are made and treatment is based on the results of carotid duplex ultrasound scanning alone, it is important to determine whether different diagnostic thresholds should be used in men and women. The purpose of this study was 2-fold: to examine whether there is an overall gender difference in carotid velocity at similar arteriographic stenoses, and to determine whether there are significant differences at clinically relevant thresholds of disease. METHODS: A database of 938 carotid arteriogram entries was established prospectively, with accompanying measurements of peak systolic velocity (PSV) and end-diastolic velocity (EDV). The percent of internal carotid artery stenosis seen on arteriograms was calculated according to criteria from the North American Symptomatic Carotid Endarterectomy Trial. Analyses were made in 536 carotid arteries in men and 402 carotid arteries in women. In addition, the single most diseased artery per patient was analyzed by gender. PSV and EDV were averaged for data subsets according to 10% intervals of internal carotid artery stenoses. Velocity for each interval was compared between men and women with the Student t test. Receiver operator characteristic curves were developed to define optimal duplex criteria for 60% and 70% stenosis. RESULTS: For all intervals, PSV and EDV averaged 9% and 6% higher, respectively, in women than in men. Significant gender differences existed between PSV and EDV for 60% and 70% stenosis (P = .03). When a single vessel per patient was analyzed these observations persisted, but lost significance for PSV at 60% stenosis (P = .18). Receiver operator characteristic curves at 90% sensitivity demonstrated that optimal PSV for 60% stenosis was 160 cm/s and 180 cm/s, and for 70% stenosis was 185 cm/s and 202 cm/s, in male and female patients, respectively. CONCLUSIONS: Women have higher carotid blood flow velocity than men do. Gender differences exist, and are notably different at clinically relevant thresholds for intervention. These data indicate that different criteria should be used for interpreting carotid velocity profiles in women than in men, and have potentially important implications for patient care.

Post-endograft abdominal aortic aneurysm shrinkage varies among hospitals: observations from multicenter trials.

PURPOSE: To evaluate differences in abdominal aortic aneurysm (AAA) shrinkage among hospitals following protocol-driven patient selection and using endografts from a single manufacturer. METHODS: Standardized inclusion criteria for the Talent endograft multicenter trials included AAA diameter >/=40 mm and proximal neck limits of length >/=5 mm, diameter 14 to 32 mm, and angle /=5-mm decrease in the AAA largest minor axis diameter. Trial sites with >10 complete study cases were selected for stepwise logistic regression analysis. In the 13 trial sites meeting this criterion, 323 patients (mean age 74; 93% men) were treated for aneurysms with a mean pretreatment diameter of 53 mm. RESULTS: At 12 months, significant AAA shrinkage occurred in 192 (59%) cases. The AAA shrinkage rate was 71% to 82% at 3 sites, 60% to 64% at 4 sites, 45% to 50% at 4 sites, and 35% and 27% at the 2 remaining sites. In the multivariate analysis, the hospital site showed a strong, independent association with aneurysm shrinkage (p<0.04). Neck and pretreatment AAA diameters were also found to be important factors (p<0.04). Age, gender, AAA classification, neck length, and angle were not significant correlates. Sixty-four (20%) endoleaks (29 type I, 34 type II, and 1 type III) were observed. The incidence of proximal endoleak was significantly different among sites (p<0.001) and highest in the 3 sites with the lowest AAA shrinkage rate. CONCLUSIONS: AAA shrinkage rates vary significantly among hospitals using the same endograft and protocol-defined patient selection criteria. Site-specific factors appear to be an important variable leading to successful endograft repair, as defined by post-endograft aneurysm shrinkage.

Fate of great saphenous vein after radio-frequency ablation: detailed ultrasound imaging.

Radio-frequency ablation (RFA) of the great saphenous vein (GSV) is an endovascular alternative to stripping. To determine long-term effectiveness, the fate of GSV treated for valvular insufficiency with RFA was evaluated in detail with ultrasound imaging (US). One hundred lower extremities were examined with high-resolution color flow US, an average of 8 months after RFA treatment of an incompetent GSV. For every cm of the RFA-treated segment, the US observation was classified as follows: absent, occluded, or recanalized. Lengths of vein segments in each class were added and percentages of absent, occluded, or recanalized segments were calculated. Five groups were identified. Group I (n = 15): segment of treated GSV was absent. Group II (n = 4): segment of treated GSV was visualized and occluded (these vein segments had no flow and were shrunk and "fibrotic" or thrombosed without clear evidence of significant shrinkage). Group III (n = 1): segment of treated GSV was recanalized. Group IV (n = 27): segment of treated GSV was obstructed (absent or occluded). Group V (n = 53): segment of treated GSV was partially recanalized, on average being 53% absent, 32% occluded, and 15% recanalized. Maximum recanalization was 50% of treated segment. RFA was successful in obliterating all of the GSV treated segment in 46% of veins (groups I, 15%, plus II, 4%, plus IV, 27%) and obliterated more than half of the treated vein segment in 53% of the cases (group V). A dynamic process of recanalization and thrombosis warrants further evaluation to determine if and how a collateral network may develop.

Percutaneous venous valve bioprosthesis: initial observations.

Chronic deep venous insufficiency remains a major health problem in the United States and worldwide. Selected patients benefit from direct deep vein valve repair or valve transplantation; however, most are not candidates for these procedures. Experience with the bovine monocusp venous valve surgically inserted into the common femoral vein (CFV) demonstrates potential benefit and good long-term patency. A venous valve placed distal to the CFV via percutaneous access has great appeal and potential for further improving venous hemodynamics, as well as reducing ambulatory venous hypertension and ulceration. Two patients were treated with a percutaneous venous valve bioprosthesis as part of a Phase I trial. The primary objective was to evaluate the safety, patency, and efficacy of the percutaneous venous valve bioprosthesis to restore competency to the deep venous system.

Computed tomography scanning for endograft planning: evolving toward three-dimensional, single source imaging.

One of the most fundamental differences between open surgical repair of aortic aneurysms and treatment by endograft exclusion is the dependency on imaging for all critically important aspects of the endovascular approach. Patient selection and preprocedure planning for device selection and sizing depend on imaging. Computed tomography (CT) scanning for endograft planning is capable of providing accurate and complete measurement data. There are problems with diameter, length, and angulation measurement when using conventional two-dimensional (2D) axial CT images that can be partly overcome by expert interpretation. However, when computerized 3D programs that include easy-to-use measurement tools process CT data, the problems of 2D CT scan data are relieved. In addition, virtual simulation of various endograft choices can be modeled within computerized renderings of patient-specific anatomy that allow testing of alternatives and provide an intuitive understanding during the planning phase.

Aortic diameter is an insensitive measurement of early aneurysm expansion after endografting.

PURPOSE: To determine the sensitivity of various methods of diameter measurement to detect abdominal aortic aneurysm (AAA) size change following endovascular grafting. METHODS: Sixty-eight patients (59 men; mean age 68 years, range 47-84) with 3-dimensional reconstruction of 196 computed tomography (CT) studies (68 preoperative, 128 follow-up) were studied. Implanted devices included 50 bifurcated and 18 straight stent-grafts. All diameter measurements were obtained from reformatted CT slices perpendicular to the center of blood flow. Three diameter measurements were made for each study: (1) transverse (TR), (2) anteroposterior (AP), and (3) maximum diameter in any orientation (Dmax). Volume measurements were calculated from the lowest main renal artery to the aortic bifurcation. Changes in diameter and volume were determined by subtracting follow-up measurements from preop measurements. Diameter and volume changes >5 mm and 10%, respectively, were considered significant. RESULTS: AAA volume significantly increased in 20 (15%) studies, decreased in 84 (66%), and remained unchanged in 24 (19%). Agreement between methods of diameter measurement (TR, AP, Dmax) and volume change were 35%, 15%, and 25% for volume increase >10%, respectively, and 70%, 88%, and 74%, respectively, for volume decrease >10%. The orientation of maximum diameter varied in individual serial exams in 19 (28%) patients. Three of 12 patients with a study showing volume increase failed to demonstrate endoleak. CONCLUSIONS: Diameter measurements were not sensitive in detecting enlarging AAA after endografting. Volume measurement determined by 3D reconstruction is the preferred method for early diagnosis of patients with enlarging AAA that may indicate increased risk of rupture after aortic endografting.

Multicenter pivotal trial results of the Lifepath System for endovascular aortic aneurysm repair.

PURPOSE: This study was undertaken to assess the results of endovascular aortic aneurysm repair with the Lifepath abdominal aortic aneurysm (AAA) graft system. METHOD: In a prospective clinical trial, 23 centers used the Lifepath System balloon-expandable, modular bifurcated stent graft for elective endovascular aortic aneurysm repair. Stent grafts were sized according to computed tomographic angiography-based diameter measurements. All repairs were performed in the operating room through bilateral surgically exposed femoral arteries. Results were assessed with contrast agent-enhanced computed tomography scans and plain abdominal x-ray films at 1, 6, 12, 24, 36, and 48 months postoperatively. RESULTS: Over 52 months (mean follow-up, 11 months), 227 patients (206 men, 21 women) were enrolled. Technical implant success rate was 98.7%. There were five (2.2%) conversions to open surgery: two emergently because of aortic perforation; to treat refractory endoleak, immediate in one and at 12 months in one; and to replace a device with wireform fractures that had migrated at 12 months, resulting in a proximal endoleak. The perioperative mortality rate was 1.3%. There was one operative death during a secondary procedure to repair perforation of the aorta. There were two perioperative deaths, from postoperative myocardial infarction (n = 1) and pulmonary embolus (n = 1). There were 12 late deaths, from coronary artery disease (n = 4), cancer (n = 2), respiratory failure (n = 2), sepsis (n = 1), or unknown cause (n = 3). Median length of stay was 2 days (mean, 4 days). There have been no AAA ruptures after successful implantation of the device, no graft limb thromboses, and no limb dislocations. At the time of operation endoleak was noted in 43 (19%) patients, but by 6 months this was reduced to 8 (5.9%) patients (type I, n = 1; type II, n = 7). There were no type III or type IV endoleaks. Secondary interventions to treat endoleaks included open conversion (n = 2), placement of extension cuffs (n = 4), repeated balloon dilation (n = 3), and coil embolization (n = 6). The two remaining secondary interventions were emergent treatment of postoperative bleeding from a groin incision, and a colon resection because of postoperative colonic ischemia, for a 12-month secondary intervention rate of 7.5%. Wireform fractures were noted in the first generation Lifepath device in 37 of 79 (47%) patients. Graft migration (>10 mm) was observed in five patients (2.2%), each of whom also had two or more fractures of the proximal anchoring wireforms. Migration resulted in a proximal attachment endoleak in one patient. In response to wireform fractures, the device was modified after the initial 79 patients were enrolled. Wireform fracture has been observed in six patients since this modification (4%), and in only one patient did this involve fracture of a proximal anchoring wireform; none of these patients has had endoleak or graft migration. By 12 months, mean aneurysm diameter was noted to decrease by 9 mm (P <.0001), and mean aneurysm volume by 42 mL (P <.0001) from the preoperative visit. CONCLUSION: The Lifepath System demonstrates a low endoleak and secondary intervention rate and high sac regression rate, compared with other devices. The unique balloon-expandable design offers the advantages of precise placement and high radial force. The device appears to be highly resistant to limb thrombosis and modular component separation. Patients were protected from AAA rupture after successful device implantation, and demonstrated significant reduction in AAA diameter and volume. Fractures of the wireforms of the main body of the device have been observed. Careful long-term follow-up is necessary.

Lessons learned from aortic aneurysm stent graft failure; observations from several perspectives.

Since the first US report of endovascular repair of abdominal aortic aneurysm in 1995, many lessons have been learned from the growing reports of successes and failures. This article combines experience with 6 endograft types plus examples from the literature to summarize lessons learned from a variety of stent graft failures classified according to (1) failure of patient selection, (2) procedural failure, and (3) failure of the endovascular device.

Distal internal iliac artery embolization: a procedure to avoid.

OBJECTIVES: Internal iliac artery (IIA) coil embolization as an adjunct to endovascular stent grafting (ESG) is common practice for treating abdominal aortic aneurysm (AAA) in patients with a substantially enlarged common iliac artery requiring extension of the stent-graft limb into the external iliac artery. The literature describing pelvic ischemia in association with IIA coil embolization contains conflicting reports of symptom severity. We studied IIA occlusion outcome as a function of coil placement in the IIA. METHODS: From August 1997 to March 2002, 20 patients with AAA underwent ESG with unilateral IIA coil embolization. Coils were placed proximal to the first branch of the IIA in 8 patients and distal to the first branch in 12 patients. Symptoms of pelvic ischemia and mid-term outcome were studied. RESULTS: Patients included 18 men and 2 women with mean age of 70(1/2) years (range, 53-86 years). Mean diameter of AAA was 54.4 mm (range, 38-80 mm), and of common iliac artery was 24.2 mm (range, 15-48 mm). Ten patients (50%) had new onset of symptoms of pelvic ischemia after endograft procedures: 1 of 8 patients (13%) with proximal IIA embolization had buttock claudication, and 9 of 12 patients (75%) with distal IIA embolization had pelvic ischemic symptoms, including buttock claudication in 8 and impotence in 1 (P =.02, Fisher exact test). No colonic ischemia occurred in this series. At 12-month follow-up, 4 patients with distal IIA embolization were symptom-free. At further follow-up to 24 months, 4 patients remained significantly limited with symptoms of claudication. CONCLUSIONS: A significantly higher incidence of symptoms of pelvic ischemia occurred with more distal placement of coils for IIA embolization. Failure to control for extent of coil placement may account for the apparently conflicting results in published studies. IIA coil embolization should be performed as proximal as possible to prevent interference with pelvic collateral circulation.

Planning endovascular vein valve implantation: significance of vein size variability.

OBJECTIVE: Endovascular placement of prosthetic valves is currently in clinical trials as treatment for lower extremity venous hypertension caused by valvular insufficiency. Femoropopliteal vein sizing is a critical factor in treatment planning. A wide diameter range could influence selection of an endoprosthesis. Quantitative data describing intrasubject vein diameter variation are scant. We measured vein diameters with ultrasound imaging to assess minimum-maximum diameter range under forced conditions of venoconstriction and venodilatation. METHODS: Diameter of the common femoral vein (CFV), proximal femoral vein (PFV), mid-femoral vein (MFV), and distal femoral vein (DFV) in the thigh and the popliteal vein (PV) was measured in the morning under conditions of minimal venodilation and in the afternoon under conditions of stressed venodilatation that included activities of daily living and a 5-minute treadmill walk. Measurements were obtained twice on two different days in both extremities in 20 subjects with CEAP clinical classification C(0) (n = 10), C(3) (n = 7), C(4) (n = 1), or C(5) (n = 2). RESULTS: Average vein diameter increased, from 11.2 +/- 2.5 (SD) mm to 14.5 +/- 2.3 mm at the CFV, from 6.9 +/- 1.8 mm to 9.4 +/- 1.9 mm at the PFV, from 6.9 +/- 1.6 mm to 9.0 +/- 1.8 mm at the MFV, from 7.3 +/- 1.7 mm to 9.1 +/- 1.5 mm at the DFV, and from 8.4 +/- 1.4 mm to 9.7 +/- 1.8 mm at the PV (P <.001 for all differences). Maximum diameter change was 8.2 mm at the CFV, 7.0 mm at the PFV, 6.6 mm at the MFV, 6.0 mm at the DFV, and 5.1 mm at the PV. Dilatation of 4 mm or greater occurred in 43% of CFV, 15% of PFV, 11% of MFV, 3% of DFV, and 1% of PV. Minimum vein diameter was found at PFV in 41%, MFV in 34%, and DFV in 23% of morning measurements and at PFV in 21%, MFV in 38%, DFV in 28%, and PV in 16% of afternoon measurements. CONCLUSIONS: Femoropopliteal veins demonstrated a wide range of diameters, and significant diameter changes were detected in all vein segments. Variations in vein diameter must be evaluated in candidates for endovascular venous valve prostheses. Such devices must adapt to a wide range in vein diameter.

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.

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.

Factors related to short length of stay after carotid endarterectomy.

In the past decade, expected in-hospital length of stay (LOS) after carotid endarterectomy (CEA) has decreased from 4 days to 1. Long LOS is associated with known complications and factors affecting severity of the patient's condition. Factors affecting an intermediate stay of 2 to 4 days need further clarification. The vascular registry at Jobst Vascular Center includes data on manifestation of disease; cardiovascular history; operation and discharge dates; surgeon; surgical details such as patching, shunting, and completion arteriography; and complications. Univariate chi-square and ANOVA and multivariate logistic regression were applied to analyze 635 CEAs performed in 1998, 1999, and 2000. Statistical significance was at a p value less than 0.05 (two-sided). Overall morbidity rate was 8.2% with three (0.5%) in-hospital neurologic complications and one death for a 0.16% mortality rate. Fifty-eight percent of the patients were discharged in 1 day. Patients staying 1 day were 3 years younger. Female gender and prior cerebrovascular accident were factors extending LOS to 2 and 3 days. History of angina, heart failure, valve disease, and vein patch or no patch contributed to LOS of 3 or 4 days. Completion arteriography had an association with LOS of 2 days. The relative percentage of patients with complications increased with LOS. No significant relationship was found for symptoms, smoking, myocardial infarction, atrial fibrillation, cardiac revascularization, or surgeon. Insulin-treated diabetes mellitus, cardiac risk factors, cerebrovascular accident, and vein patch or no patch correlated with prolonged hospitalization. Factors were identified that may alter a clinical pathway designed for discharge 1 day after CEA. Focused management of patients with cardiac and cerebrovascular accident history or requiring vein patch and a better understanding of CEA in women may further increase the percentage of patients discharged 1 day after CEA.

Noninvasive measurement of shear rate in autologous and prosthetic bypass grafts.

There is a major difference in thrombogenicity between lower extremity prosthetic and autologous vein bypass grafts, and arterial blood flow shear rate is known to influence thrombus formation. Despite this association, there has been little direct clinical observation of shear rates in bypass grafts. The authors developed a new noninvasive method to quantitate human arterial shear rate and used it in a pilot study to characterize differences in lower extremity bypasses. Shear rates were measured in 10 prosthetic and 14 autologous vein femoropopliteal bypass grafts. With CVI-M-mode color flow ultrasonography in resting supine patients, a velocity profile was recorded from a midgraft longitudinal section in the ultrasound beam direction. Shear rates were calculated by using a mathematical-graphic computer program at the anteromedial (near) and posterolateral (far) graft walls by averaging values immediately before and after peak systolic velocity (PSV). Comparison between prosthetic and autologous graft groups respectively revealed that differences in age (67 +/- 12 [SD] vs 71 +/- 10 yr), male gender (60% vs 43%), prevalence of hypertension (50% vs 71%), diabetes (40% vs 64%), smoking (50% vs 50%), hypercholesterolemia (30% vs 29%), coronary artery disease (60% vs 50%), and critical ischemia (60% vs 86%) did not reach statistical significance (p>0.19). Median PSVs were significantly less in prosthetic than in autologous vein bypasses (37 +/- 13 vs 57 +/- 22 cm/s, p=0.018). Prosthetic and autologous graft diameters were not statistically significantly different (6.3 +/- 1.1 vs 5.6 +/- 1.3 mm, p = 0.18). Shear rates were significantly less in prosthetic than in autologous vein bypasses both at the near wall (382 +/- 146 vs 698 +/- 271 s(-1), p=0.003) and at the far wall (551+/-235 vs 827+/-339 s(-1), p-0.037). This mathematical model can be used to calculate shear rate from observed ultrasound flow patterns. Prosthetic bypass grafts had lower shear rates than autologous vein grafts.

Bell-bottom aortoiliac endografts: an alternative that preserves pelvic blood flow.

OBJECTIVE: Dilated common iliac arteries that complicate aortic aneurysm stent grafting usually have been managed with endograft extension across the iliac artery bifurcation with internal iliac artery (IIA) occlusion. We studied 25 patients with significant common iliac artery (CIA) dilation treated with two methods: endograft extension across the iliac bifurcation or a new approach with a flared cuff within the CIA that preserves the IIA. METHODS: Of 86 patients with abdominal aortic aneurysm (AAA) who underwent bifurcated endovascular stent grafting (ESG), 25 (29.1%) had at least one dilated CIA. Two treatment groups had different methods of management of iliac artery dilation. Group 1 underwent ESG with straight extension across the iliac bifurcation and IIA coil embolization before the ESG procedure (n = 2) or simultaneously with ESG (n = 8). Group 2 underwent ESG with flared distal cuff (AneuRx, Medtronic AVE, Santa Rosa, Calif) contained within the CIA, the so-called "bell-bottom" procedure, thus preserving the IIA (n = 15). Iliac artery dimensions, operating room time, fluoroscopy time, and postoperative complications were prospectively gathered. RESULTS: Two women and 23 men had mean diameters of AAA of 56.6 mm (range, 38 to 98 mm) and of CIA of 21.4 mm (range, 15 to 48 mm). The diameters of CIA treated with device extension into external iliac artery after IIA coil embolization in group 1 and with the bell-bottom procedure in group 2 were not different (mean CIA diameter, 19.9 mm; range, 15 to 26 mm; and mean, 19.1 mm; range, 15 to 24 mm; respectively). However, significantly lower operating room and catheter procedure times were found in group 2 compared with group 1 (137 versus 192 minutes; 58 versus 106 minutes; P =.02 and.02, respectively). No periprocedural type I endoleaks were found in either group. Nine patients in group 2 also had a second contralateral CIA aneurysm, and five patients (mean CIA diameter, 33.0 mm; range, 22 to 48 mm) underwent treatment with extension across the iliac artery bifurcation and IIA occlusion. Use of the bell-bottom procedure on the other side allowed preservation of one IIA. Four cases (mean diameter, 19.3 mm) also underwent contralateral bell-bottom procedure. Two of these group 2 patients had complications, with severe buttock claudication in one and distal embolism necessitating limb salvage bypass after preoperative coil embolization of the IIA in another. CONCLUSION: Significant CIA ectasia or small aneurysm is often associated with AAA. In such cases, the bell-bottom procedure that preserves IIA circulation is a new alternative to the common practice of placement of endograft extensions across the iliac artery bifurcation in patients with at least one CIA diameter of less than 26 mm. Additional benefits include reduced total procedure time. Early technical success appears to justify continued use. However, long-term evaluation is necessary to determine durability because the risk of rupture as the result of potential expansion of the excluded iliac artery or late failure is unknown.

Preclinical testing for aortic endovascular grafts: results of a Food and Drug Administration workshop.

BACKGROUND: Since their introduction into clinical trials in the United States, endovascular aortic grafts have shown various types of problems. Although details of design and construction vary between different endovascular grafts and failure modes have had a variety of causes and clinical effects, the inability of preclinical testing to predict these failures remains common to all endovascular grafts. The need to improve preclinical testing in an attempt to reduce clinical device failures resulted in a Food and Drug Administration-sponsored workshop on endovascular graft preclinical testing held in Rockville, Md, from July 31 to August 1, 2001. FORMAT: The workshop was not designed as a consensus conference. Instead, it provided a forum for bringing stakeholders together to define problems and identify areas of agreement and disagreement. The workshop had 34 invited participants who represented device manufacturers, the medical community, the Food and Drug Administration, and testing facilities, and international attendance was more than 120 people. OUTCOME: Discussion centered on: 1, defining the physiologic, anatomic, and morphologic characteristics of abdominal aortic aneurysms before and after endovascular graft treatment; 2, identifying the types of failures that have been observed clinically; and 3, determining which characteristics should be considered during preclinical modeling to better predict clinical performance. Attendees agreed to the need to better define and address anatomic characteristics and changes in the aneurysm after endograft treatment to optimize preclinical testing. Much discussion and little agreement occurred on the importance of flow-related forces on graft performance or the need or ability to define and model physiologic compliance during durability testing. The discussion and conclusions are summarized in this paper and are provided in detail at: http://www.fda.gov/cdrh/meetings/073101workshop.html. CONCLUSION: The workshop raised awareness of significant performance issues and the challenges of modeling the extremely variable and relatively undefined environment of abdominal aortic aneurysms. Through the interactive format of the workshop, participants identified areas of preclinical testing, device design, and aspects of the simulated environment that need further consideration.

CT artifacts of the proximal aortic neck: an important problem in endograft planning.

PURPOSE: To describe the imaging error introduced by noncircular abdominal aortic aneurysm (AAA) necks in axial and reformatted computed tomographic (CT) images and discuss the potential implications for aortic endografting. METHODS: The records of 120 endograft patients with preoperative CT axial scans and subsequent 3-dimensional (3D) computerized reconstructions were reviewed. Maximum and minimum infrarenal aortic neck diameters were measured from axial CT scans and 3D reformatted slices at the same point on the vessel. Diameter measurements were made at the largest point within the 10-mm segment of vessel below the lowest renal artery. Excluded were aneurysms with proximal neck minimum diameters >30 mm, neck lengths < 15 mm, or angulation > 75 degrees measured on the axial CT slice. RESULTS: Measuring from reformatted CT slices, 86 (71.6%) cases had < or = 2-mm differences between maximal and minimal neck diameters, comprising the "round neck" group A. In 34 (28.4%) cases, the neck was not round: 26 (21.7%) had diameter differences between 2 and 4 mm (group B) and 8 (6.7%) had a > 4-mm difference (group C; range 4.1-8.1 mm). Although AAA diameter, neck length, and neck angle progressively increased as the difference between neck maximum and minimum diameters grew, i.e., greater eccentricity, these trends did not reach statistical significance. Mean infrarenal neck maximum diameter was significantly larger in group C (30.2 +/- 3.4 mm) compared to groups A (23.0 +/- 2.9 mm, p = 0.0002) and B (23.8 +/- 3.6 mm, p = 0.0003). Hence, 28.4% of AAAs had a noncircular aortic neck of varying degree, and 6.7% had an eccentricity factor that may have clinical significance. CONCLUSIONS: This study confirms the importance of selecting an endoprosthesis sized 15% to 20% larger than the infrarenal aortic neck diameter. Three-dimensional reconstruction using reformatted CT slices perpendicular to the flow lumen is an important tool that offers enhanced accuracy of infrarenal aortic neck evaluation.