Observer variability of iliac artery measurements in endovascular repair of abdominal aortic aneurysms.

Accurate measurement of iliac arteries is essential for successful delivery of aortic endografts without iliac limb endoleak. Although intravascular ultrasound measurements may be reliable, they require an invasive procedure. Therefore, helical computed tomography (hCT) has become the most commonly used modality for obtaining preprocedure arterial diameter measurements. The accuracy of hCT remains ill-defined, however, because an anatomic gold standard with which to compare the measurements is not available. We therefore assessed inter- and intraobserver variability of hCT measurements. We also applied accepted cutoff measurements to determine the clinical impact of observer variability in predicting the need for adjunctive iliac access and iliac limb seal procedures. hCT scans were analyzed in 30 patients who had undergone successful placement of a bifurcated endograft (26 Ancure, 4 Aneurex). Mean age of patients was 75 years, the male/female ratio was 27:3. Three blinded observers measured transverse diameters (maximal aortic aneurysm [Amax], narrowest infrarenal aortic neck [Amin], maximal common iliac [Imax], and narrowest iliac artery [Imin]). Inter- and intraobserver variability was calculated as standard deviation of mean pair differences according to the method of Bland and Altman. The true incidence of adjunctive procedures to facilitate delivery of the device into the aorta and ensure iliac limb seal was compared with that predicted by the observers to obtain sensitivity, specificity, and positive (PPV) and negative predictive value (NPV) for the measurements. Interobserver variability of iliac measurements was higher than intraobserver variability (p < 0.05). Interobserver variability of Amax ranged from 4.37 to 10.73% of the mean Amax. Conversely, variability of Amin was 8.91-18.89%, that of Imax was 12.11-22.23%, and that of Imin was 10.51-18.73% (p < 0.05 vs. Amax). Therefore, interobserver variability influenced aortic neck and iliac diameter twice as much as it did aneurysm measurements. To successfully place 30 endografts we performed 8 adjunctive access procedures (4 angioplasties, 4 common iliac artery conduits) and 17 adjunctive procedures in 60 limbs to ensure limb seal (9 unilateral IIA coil embolizations, 8 stents). We used 8.5 (Ancure) and 8.0 (Aneurex) mm as lower limits of acceptability for uncomplicated access, and 13.4 (Ancure) and 16 (Aneurex) mm as the upper limits of acceptability for uncomplicated iliac limb seal. These limits were applied to measurements from the three observers to predict need for adjunctive access or iliac seal procedures in this cohort. Sensitivity, specificity, PPV, and NPV of these observer measurements for a need to perform additional access procedures were 0.67, 0.80, 0.55, and 0.87; the same values for a need to perform additional seal procedures were 0.71, 0.74, 0.52, and 0.86, respectively. Interobserver variability was approximately 20% of measured iliac diameter. This explains why helical CT measurements were noted to have low PPV in predicting the need for an adjunctive access or limb seal procedure. These data establish PPV and NPV for hCT and provide objective evidence for the need to improve iliac artery imaging. Until more accurate imaging becomes available, we recommend oversizing of iliac limbs by 10-20% in patients with wide landing zones and that surgeons be prepared to resolve unexpected iliac artery access or seal problems intraoperatively.

Carotid artery stenting: analysis of data for 105 patients at high risk.

OBJECTIVES: Carotid artery stenting (CAS) has been recommended as an alternative to carotid endarterectomy (CEA) by some clinicians. However, recently published clinical trials have reported 30-day stroke and death rates of 10% to 12%. This prompted review of our experience with CAS in patients at high risk, to document our results and guide further use of CAS. METHODS: From September 1996 to the present, we performed 114 consecutive CAS procedures in 105 patients. Sixty-three patients were men (60%) and 42 patients were women (40%), with mean age of 70 years (range, 45-93 years). Indications for CAS included recurrent stenosis after previous CEA in 74 patients (65%), primary lesions in 32 patients at high risk (28%), and carotid stenosis with previous ipsilateral radiation therapy in 8 patients (7%). Asymptomatic stenosis (>80%) was managed in 70 patients (61%), and symptomatic lesions (>50%) were treated in 44 patients (39%). RESULTS: CAS was technically successful in all patients. Mean severity of stenosis before CAS was 87% +/- 6%, compared with 9% +/- 4% after CAS. Two patients (1.9%) died, 1 of reperfusion-intracerebral hemorrhage and 1 of myocardial infarction 10 days after discharge; and 1 patient (0.95%) had a stroke (retinal infarction), for a 30-day stroke and death rate of 2.85%. Two patients (1.9%) had transient neurologic events. No cranial nerve deficits were noted. No neurologic complications have been noted in the last 27 patients (26%). CONCLUSIONS: A 30-day stroke and death rate of 2.85% in our experience demonstrates acceptability of CAS as an alternative to repeat operation or primary CEA in patients at high risk or in patients with radiation-induced stenosis. We recommend further clinical investigation of CAS and participation in clinical trials by vascular surgeons.

Pixel distribution analysis of B-mode ultrasound scan images predicts histologic features of atherosclerotic carotid plaques.

BACKGROUND: The correlation of B-mode ultrasonographic morphology with histologic characteristics of atherosclerotic carotid plaques remains ill-defined. The classification of plaques with recently reported measures of plaque echogenicity and heterogeneity has been unsatisfactory. We used computer-assisted duplex ultrasound (DU) scan image analysis to determine echogenicity of specific tissues in control subjects. This information was used to quantify each tissue in imaged carotid plaques with pixel distribution analysis (PDA). These objective observations then were quantitatively compared with plaque histology in symptomatic and asymptomatic patients. METHODS: We performed standardized DU scanning of healthy tissues in 10 volunteer subjects and of 20 carotid artery plaques (7 symptomatic and 13 asymptomatic) in 19 patients with carotid stenosis. The plaques underwent histologic analysis after carotid endarterectomy. The grayscale intensity ranges of blood, lipid, fibromuscular tissue, and calcium were calculated in the control subjects. With computer-assisted image analysis, B-mode images of plaques were linearly scaled to normalize data. Pixel distribution within the images then was analyzed. The grayscale ranges of known tissues obtained from control subjects helped define the amount of intraplaque hemorrhage, lipid, fibromuscular tissue, and calcium within carotid plaque images. This analysis was correlated with tissue composition measurements on histologic sections of excised plaques. RESULTS: The median grayscale intensity (range) in control subjects was 2 (0 to 4) for blood, 12 (8 to 26) for lipid, 53 (41 to 76) for muscle, 172 (112 to 196) for fibrous tissue, and 221 (211 to 255) for calcium. PDA-derived predictions for blood, lipid, fibromuscular tissue, and calcium within carotid plaques correlated significantly with the histologic estimates of each tissue respectively (blood: P =.012; lipid: P =.0006; fibromuscular: P =.035; and calcium: P =.0001). A significantly higher amount of blood and lipid was seen within symptomatic plaques compared with asymptomatic ones (P =.0048 and P =.026, respectively). Conversely, a larger amount of calcification was noted within asymptomatic plaques (P =.0002). CONCLUSION: Computer-assisted PDA of DU scan images accurately quantified intraplaque hemorrhage, fibromuscular tissue, calcium, and lipid. Symptomatic plaques had lower calcium content but larger amounts of intraplaque hemorrhage and lipid. Quantitative PDA may be used to determine carotid plaque tissue composition to assist in the identification of symptomatic and potentially unstable asymptomatic plaques.

Carotid artery closure for endarterectomy does not influence results of angioplasty-stenting for restenosis.

OBJECTIVE: Carotid angioplasty and stenting (CAS) has been recommended by some authors for the management of postendarterectomy restenosis. However, some authors have expressed concern about the influence of primary closure and patch angioplasty performed during carotid endarterectomy (CEA) on the incidence rate of complications after CAS. METHODS: We analyzed our consecutive series of 54 CAS procedures performed for restenosis after prior CEA. These procedures accounted for 75% of the 72 CAS procedures performed at our institution for all indications during the last 4 years. Of these 54 patients, 28 (52%) were men and 26 (48%) were women, with a mean age of 69 years. The mean clinical follow-up period was 18 months (range, 1 to 48 months). The mean interval between prior CEA and CAS was 16 months (range, 6 to 62 months). Nineteen patients were symptomatic (35%), and 35 were asymptomatic (65%). The mean severity of restenosis was 84% +/- 7% (standard deviation). The mean residual stenosis after CAS was 8% +/- 3% (standard deviation). RESULTS: Among the 54 prior CEAs, eight cases were performed with primary closure (15%), five procedures used patch closure with autologous vein (9%), and 41 operations used Dacron patch closures (76%). All patients were managed successfully with CAS with predeployment angioplasty with low profile balloons, self-expanding stents, and poststent angioplasty to approximate the transverse diameter of the carotid artery. No instances of contrast extravasation, arterial disruption, or subintimal dissection were observed. One stroke (1.8%), a retinal infarction with partial field of vision loss, occurred in a patient with prior CEA and Dacron patch closure, and no deaths were observed in the series. CONCLUSION: Performance of CAS for restenosis after CEA with autologous or synthetic patch angioplasty was technically successful in all 54 procedures. The method of closure of the arteriotomy during CEA, primary closure or patch angioplasty, did not influence the incidence of complications.