Noninvasive ultrasound measurement of shear rate in leg bypass grafts.

Shear has been implicated in the etiology of atherosclerosis, thrombosis and graft stenosis. We measured shear rate noninvasively in infrainguinal bypasses. Velocity profiles were recorded from 35 femoropopliteal and 40 tibial grafts. Flow rate (Q), systolic shear rate (SSR), diameter, and bluntness factor (BF) were measured at midgraft using ultrasound (US). Mean shear rate (MSR) was calculated from flow and diameter. SSR, 671 +/- 260 (SD) vs. 659 +/- 304 s(-1) (p = 0.85), and MSR, 168 +/- 84 vs. 193 +/- 110 s(-1) (p = 0.26), were similar for popliteal and tibial bypasses, but differences in Q, 126 +/- 57 vs. 104 +/- 38 mL/min, were borderline significant (p = 0.058). Popliteal grafts had larger diameters, 5.2 +/- 1.1 mm vs. 4.7 +/- 0.8 mm (p = 0.048), and BF, 3.4 +/- 0.9 vs. 2.8 +/- 0.7 (p = 0.0014). Shear rates were obtained noninvasively in humans. Larger diameters in popliteal vs. tibial bypasses did not result in lower shear rates and were compensated for by larger bluntness factors. Velocity profile bluntness cannot be ignored in shear rate analysis.

Intermittent claudication: effective medical management of a common circulatory problem.

Intermittent claudication (IC), most often characterized by a reproducible, painful aching or cramping in muscle groups of the leg caused by walking and relieved by rest, is a common, lifestyle-limiting symptom of lower-extremity peripheral arterial occlusive disease. Because IC is usually indicative of systemic atherosclerosis, active investigation and treatment are recommended. Positive outcomes have been shown with a treatment regimen including risk-factor modification, particularly smoking cessation and control of diabetes, exercise, and pharmacotherapy. Pentoxifylline has been used since 1984 for the treatment of IC with indifferent results. Recently, clinical trials with cilostazol, a drug approved for use in the United States, have shown significant effectiveness in IC patients, generally doubling their maximal walking distance at 24 weeks of treatment. Cilostazol has also been shown to be significantly more effective than pentoxifylline in improving pain-free and maximal walking distance. Other classes of drugs, such as platelet antiaggregants, are being studied for the treatment of IC, but little efficacy has been shown. Arterial revascularization by endovascular or surgical methods is an additional option but must be considered on an individual basis depending on severity of symptoms and disability in each patient.

Results of an aortic endograft trial: impact of device failure beyond 12 months.

PURPOSE: Analysis endpoints of patient survival and aortic rupture at a reporting interval of 12 months are regularly used to compare endograft aortic aneurysm (EAG) repair to conventional open surgical (COS) repair. This study reports a multicenter EAG repair versus COS repair parallel cohort trial at 12 months and additional observations of specific device failure types and their impact on an aortic endograft design beyond that follow-up period. METHODS: From August 1997 to September 1998, 240 patients who were treated with bifurcation EAG repairs and 28 patients who were treated with straight EAG repairs were compared with 98 patients who were treated with COS repair for elective infrarenal aortic aneurysm repair. Allocation to treatment was based on aneurysm anatomy. All cohorts underwent infrarenal procedures. Data from concurrent, nonrandomized patient accrual from 17 United States institutions were prospectively gathered and independently adjudicated for safety and efficacy. An independent core laboratory evaluated all imaging data. RESULTS: There were 308 men and 58 women (mean age, 72 years; range, 42-94 years) treated for infrarenal aortic aneurysm (mean diameter, 55 mm; range, 40-115 mm). Mean preoperative aneurysm diameters were clinically similar (EAG repair, 54 mm vs COS repair, 57 mm). The two cohorts were not significantly different in terms of gender (P = .30) or age (P = .32). EAG repair technical success (aneurysm exclusion, graft patency, patient survival) at 30 days was 89.2%. Five patients required immediate conversion to COS repair, four caused by access complications and one caused by operator-induced EAG repair malposition. The 30-day mortality rate was 1.5% for EAG repair and 3.1% for COS repair (P = .59). The 12-month survival rate was 94.3% for EAG repair and 95.9% for COS repair. The intermediate-term cumulative survival rate at 24 months was 84.9% for EAG repair and 80.3% for COS repair (P = .48). EAG repair device failure occurred from fabric erosion in six patients, with two deaths from ruptured aneurysm at 18 and 28 months after endografting and four device failures resolved by secondary procedures. Five endograft limb dislocations were all resolved by secondary endovascular procedures. Major or minor endograft migration required secondary procedures in five patients, including conversion in two patients. CONCLUSION: The clinical outcome at 12 months demonstrated effective aneurysm treatment and comparable safety between EAG repair and COS repair by conventional endpoints. Ongoing follow-up beyond 12 months revealed device-related adverse events that required endograft design changes. Diligent surveillance of outcomes beyond 12 months is necessary to adequately evaluate EAG repair devices.

Current status of carotid bifurcation angioplasty and stenting based on a consensus of opinion leaders.

OBJECTIVE: Carotid bifurcation angioplasty and stenting (CBAS) has generated controversy and widely divergent opinions about its current therapeutic role. To resolve differences and establish a unified view of CBAS' present role, a consensus conference of 17 experts, world opinion leaders from five countries, was held on November 21, 1999. METHODS: These 17 participants had previously answered 18 key questions on current CBAS issues. At the conference these 18 questions and participants' answers were discussed and in some cases modified to determine points of agreement (consensus), near consensus, (prevailing opinion), or divided opinion (disagreement). RESULTS: Conference discussion added two modified questions, placing a total of 20 key questions before the participants, representing four specialties (interventional radiology, seven; vascular surgery, six; interventional cardiology, three; neurosurgery, one). It is interesting that consensus was reached on the answers to 11 (55%) of 20 of the questions, and near consensus was reached on answers to 6 (30%) of 20 of the questions. Only with the answers to three (15%) of the questions was there persisting controversy. Moreover, both these differences and areas of agreement crossed specialty lines. Consensus Conclusions: CBAS should not currently undergo widespread practice, which should await results of randomized trials. CBAS is currently appropriate treatment for patients at high risk in experienced centers. CBAS is not generally appropriate for patients at low risk. Neurorescue skills should be available if CBAS is performed. When cerebral protection devices are available, they should be used for CBAS. Adequate stents and technology for performing CBAS currently exist. There were divergent opinions regarding the proportions of patients presently acceptable for CBAS treatment (<5% to 100%, mean 44%) and best treated by CBAS (<3% to 100%, mean 34%). These and other consensus conclusions will help physicians in all specialties deal with CBAS in a rational way rather than by being guided by unsubstantiated claims.

Diameter comparison of saphenous vein bypasses for popliteal aneurysm versus peripheral arterial occlusive disease in matched subjects.

Previous research has suggested that arterial aneurysm might result from a systemic tendency to dilatation. This systemic effect would involve both arterial and venous dilatation. The authors investigated whether venous grafts implanted to bypass popliteal artery aneurysms (PAA) had larger diameters than those implanted to treat peripheral arterial occlusive disease (PAOD). They compared representative diameters of 20 vein grafts implanted for PAA with matched bypass grafts implanted for PAOD. Graft diameters were obtained by means of CVI-Q M-mode ultrasound imaging. Each PAA patient/graft was matched to an equivalent PAOD patient/graft based on the patient's gender and age and the vein graft type and distal anastomosis. Secondarily, graft proximal anastomosis was matched in 60% (12/20) of the cases. Age was matched if the difference was < or = 4 years. Average age at the time of surgery was 68 +/-12 years for PAA and 68 +/-13 for PAOD groups. There were 11 reversed greater saphenous vein (GSV), 2 nonreversed GSV, and 7 in situ GSV in each group. Distal anastomoses were at the popliteal (15), peroneal (3), posterior (1), and anterior tibial (1) arteries in each group. Matching was not possible for lesser saphenous and cephalic vein grafts or bypasses to the tibial-peroneal trunk. Graft diameters were significantly larger for the PAA group, 6.24 +/-0.66 mm (standard deviation), than for the PAOD group, 5.73 +/-0.69 mm (p < 0.02, Mann-Whitney U test). Of 10 bypasses with diameter >6.5 mm, 8 were implanted for PAA. If these 10 largest bypasses were eliminated from the calculations, the mean graft diameters were 5.82 +/-0.51 mm and 5.57 +/-0.52 mm for the PAA and PAOD groups, respectively (p = 0.28). Bypass grafts implanted in PAA patients had significantly greater diameters than grafts implanted in PAOD patients. This finding, however, was due to a subgroup of grafts with diameters >6.5 mm. Perhaps systemic abnormalities associated with PAA should be first studied in patients with large vein grafts or large original veins.

Effects of cilostazol on resting ankle pressures and exercise-induced ischemia in patients with intermittent claudication.

During exercise, patients with intermittent claudication (IC) have decreased limb arterial blood pressure that recovers during rest. A novel method for assessing dynamic recovery of function is measurement of the hemodynamic response after exercise. Cilostazol (Pletal), a new agent for the treatment of IC, increases walking distance and may decrease ischemic burden. The objective of this study was to assess the effect of cilostazol versus placebo on hemodynamic measurements after exercise-induced ischemia in patients with IC. Two double-blind, placebo-controlled studies with similar inclusion/exclusion criteria and duration (24 weeks) were pooled. Patients walked on a treadmill at 2.0 miles/h (3.2 km/h) on a 12.5% grade until the claudication-limited maximal walking distance (MWD) was reached. Anterior and posterior tibial pressures were measured with Doppler ultrasound at baseline and at 1, 5, and 9 min during recovery. Area under the curve (AUC), a measure of the time course of recovery of systolic pressure after exercise-induced ischemia, and ankle-brachial index (ABI) were calculated and compared using analysis of variance (ANOVA). All three treatment groups (308 patients randomized to cilostazol 100 mg bid, 303 to cilostazol 50 mg bid, and 299 to placebo) had similar baseline characteristics. Mean post-exercise AUC for cilostazol 100 mg and 50 mg bid versus placebo increased by 0.31 (p = 0.001) and 0.26 (p = 0.004), respectively. Mean resting ABI increased by 0.03 (p = 0.0039) and 0.04 (p = 0.0001) in the cilostazol 100 mg and 50 mg bid groups, respectively. In conclusion, following 24 weeks of treatment, cilostazol increased the ABI at rest and improved the recovery time of ankle pressures post-exercise.

Carotid endarterectomy versus carotid angioplasty: comparison of current results.

Carotid endarterectomy is the standard treatment for carotid artery occlusive disease, with proven low morbidity and mortality and acceptable long-term durability. Recently, enthusiasm for carotid angioplasty and stenting has led to increasingly widespread clinical application of this endovascular technique. Because no prospective randomized trial has yet been published comparing carotid endarterectomy with carotid angioplasty and stenting, we must use data from statewide, population-based, and single-center reports to compare the procedures. Although carotid stenting has already earned a significant role in treating selected patients with carotid disease, current evidence does not indicate the use of carotid stenting as a routine alternative to carotid endarterectomy.

Endograft planning without preoperative arteriography: a clinical feasibility study.

PURPOSE: To investigate an alternative method of preprocedural planning for aortic endografting based solely on spiral computed tomography (CT) with 3-dimensional (3D) reconstruction without preoperative arteriography. METHODS: From August 1997 to April 1998, 25 consecutive patients with abdominal aortic aneurysms (AAA) were evaluated for endovascular repair by spiral CT scans (2-mm slice thickness) and computerized 3D model construction. No additional imaging for planning was performed. The aortoiliac dimensions, thrombus load, calcification, and vessel tortuosity were measured and evaluated from the 3D model of the aortoiliac segment. These data were used for selecting the patients; the configuration, diameter, and length of the endograft; and the attachment sites for deployment. RESULTS: Primary procedural success was 92% (23/25). All endografts were deployed as planned, and there were no conversions to open repair. Six patients required adjunctive procedures for delivery system access or for iliac aneurysm exclusion, as predicted by the 3D model. Mean procedural time was 91 minutes (range 24 to 273). Two (8%) type II (side branch) endoleaks both sealed spontaneously within 1 month. No graft-related complications or death occurred, for a 30-day technical success rate of 100%. CONCLUSIONS: This computerized 3D model provided accurate data for preoperative evaluation of the aortoiliac segment for endovascular AAA repair. Satisfactory technical outcomes for aortic endografts can be achieved without the use of preprocedural invasive imaging.

A new pharmacological treatment for intermittent claudication: results of a randomized, multicenter trial.

BACKGROUND: Effective medication is limited for the relief of intermittent claudication, a common manifestation of arterial occlusive disease. Cilostazol is a potent inhibitor of platelet aggregation with vasodilation effects. OBJECTIVE: To evaluate the safety and efficacy of cilostazol for the treatment of intermittent claudication. METHODS: Thirty-seven outpatient vascular medicine clinics at regional tertiary and university hospitals in the United States participated in this multicenter, randomized, double-blind, placebo-controlled, parallel trial. Of the 663 screened volunteer patients with leg discomfort, a total of 516 men and women 40 years or older with a diagnosis of moderately severe chronic, stable, symptomatic intermittent claudication were randomized to receive cilostazol, 100 mg, cilostazol, 50 mg, or placebo twice a day orally for 24 weeks. Outcome measures included pain-free and maximal walking distances via treadmill testing, patient-based quality-of-life measures, global assessments by patient and physician, and cardiovascular morbidity and all-cause mortality survival analysis. RESULTS: The clinical and statistical superiority of active treatment over placebo was evident as early as week 4, with continued improvement at all subsequent time points. After 24 weeks, patients who received cilostazol, 100 mg, twice a day had a 51% geometric mean improvement in maximal walking distance (P<.001 vs placebo); those who received cilostazol, 50 mg, twice a day had a 38% geometric mean improvement in maximal walking distance (P<.001 vs placebo). These percentages translate into an arithmetic mean increase in distance walked, from 129.7 m at baseline to 258.8 m at week 24 for the cilostazol, 100 mg, group, and from 131.5 to 198.8 m for the cilostazol, 50 mg, group. Geometric mean change for pain-free walking distance increased by 59% (P<.001) and 48% (P<.001), respectively, in the cilostazol, 100 mg, and cilostazol, 50 mg, groups. These results were corroborated by the results of subjective quality-of-life assessments, functional status, and global evaluations. Headache, abnormal stool samples or diarrhea, dizziness, and palpitations were the most commonly reported potentially drug-related adverse events and were self-limited. A total of 75 patients (14.5%) withdrew because of any adverse event, which was equally distributed between all 3 treatment groups. Similarly, there were no differences between groups in the incidence of combined cardiovascular morbidity or all-cause mortality. CONCLUSION: Compared with placebo, long-term use of cilostazol, 100 mg or 50 mg, twice a day significantly improves walking distances in patients with intermittent claudication.

Cost comparison of aortic aneurysm endograft exclusion versus open surgical repair.

BACKGROUND: Shrinking health care resources impose a requirement to evaluate new technology for cost as well as clinical effectiveness. We studied an initial clinical experience with endograft treatment (EAG) of abdominal aortic aneurysm (AAA) at the beginning of an endovascular program in comparison with open surgical repair (OSR), which had been in use for decades. METHODS: From March 1997 to April 1998, the utilization of hospital resources, actual cost, clinical descriptors, and treatment outcomes were recorded for two contemporaneous groups, each having 16 consecutive patients with AAA, treated with either EAG or OSR. Subjects were not randomized; EAG treatment was based on predetermined exclusion/inclusion criteria. Statistical comparison was by either Fisher's exact test or the Wilcoxon rank sum test. RESULTS: There were no differences between OSR and EAG in age, gender, AAA size, smoking status, diabetes, ischemic heart disease, history of coronary artery bypass grafts, previous vascular surgery, or other comorbidity. There were no deaths in either group. Patients treated by EAG procedure had significantly lower length of hospital stay, length of stay in intensive care unit, time in operating room, and cost of operating room without graft (P <0.05). Cost of operating room with graft was less in OSR group (P <0.001). In-hospital imaging costs specific to the EAG procedure were $1,370.45 +/- $66.92 (range $911.58 to $1,826.76). Total costs were not significantly different between the OSR and EAG, $12,714.19 +/- $1,115.52 and $12,904.99 +/- $494.69, respectively (P = 0.26). CONCLUSIONS: Total hospital cost is not different for the two treatments studied despite differences in experience with their use. Endograft treatment utilizes significantly less hospital resources than open surgical repair. The endograft prosthesis contributes a significant cost increment that may decline with expanded use.

Carotid arterial ultrasound scan imaging: A direct approach to stenosis measurement.

PURPOSE: Management decisions regarding carotid artery disease are critically dependent on stenosis but have been made difficult because of conflicting methods used to determine such stenosis. The increasing use of duplex ultrasound scanning has conventionally depended on Doppler velocity measurement, an indirect method for calculating carotid stenosis. Recent technical advances have improved the quality of B-mode/color-flow ultrasound scan imaging (USI). We tested prospectively whether USI was clinically effective as the primary criterion for estimating carotid stenosis. METHODS: Transverse and longitudinal USI, Doppler velocity, and arteriography data were obtained sequentially and independently for 713 carotid bifurcations. The internal carotid artery (ICA) residual lumen, the local outer diameter at the stenotic site, and the diameter distal to the bulb were measured in a representative USI longitudinal section. The peak systolic velocity and the end diastolic velocity (EDV) were measured at the stenosis. Local stenosis as determined with USI was compared with the x-ray arteriographic clinical radiology interpretation (XRI). As the primary method, radiologists compared the residual lumen with the distal ICA diameter, as recommended by the North American Symptomatic Carotid Endarterectomy Trial and the Asymptomatic Carotid Atherosclerosis Study. Analysis was by means of the USI positive predictive value (PPV) and negative predictive value (NPV) of the XRI findings, with the assumption that 80%, 70%, and 60% local stenosis with USI related to 70%, 60%, and 50% stenosis with XRI, respectively. RESULTS: All 56 ICA occlusions as determined with USI were confirmed with XRI. When the USI showed 80% to 99% stenosis, the PPV of the XRI showing 70% to 99% stenosis was 94% (116/123). Two ICAs that were shown to be severely diseased with USI appeared to be occluded with XRI. For <50% stenosis shown with USI, the prediction of <50% stenosis shown with XRI was 94% (253/269). For borderline stenosis in the 50% to 79% range with USI, the addition of velocity criteria to USI data improved both the PPV and the NPV. In the range of 70% to 79% stenosis with USI, the PPV improved from 82% (76/93) to 91% (53/58) for the subgroup with an EDV of more than 80 cm/s. For the range of 60% to 69% stenosis with USI, the PPV improved from 75% (71/95) to 95% (21/22) for the subgroup with an EDV of more than 80 cm/s. In the range of 50% to 59% stenosis with USI, the NPV improved from 69% (53/77) to 93% (14/15) for the subset with a peak systolic velocity of less than 100 cm/s. CONCLUSION: On the basis of the USI data alone, a prediction of arteriographic findings was possible at the 95% level for occlusion and severe stenosis and for ruling out hemodynamically significant stenosis. The addition of velocity data improved prediction in borderline degrees of stenosis. USI was effective for quantifying clinically significant degrees of stenosis.

Screening and preoperative imaging of candidates for conventional repair of abdominal aortic aneurysm.

This article summarizes considerations in screening for abdominal aortic aneurysm (AAA) and preoperative imaging before conventional surgical repair. Because death of this relatively common disease can be prevented by an effective treatment, there is great interest in early detection and elective repair. The prevalence of AAA in older adults (65 to 80 years of age) varies from 4% to 7%. Factors associated with AAA include smoking, age, coronary artery disease, high serum cholesterol level, family history, and hypertension. A higher prevalence of AAA has been found among first-degree relatives of AAA patients, particularly in men, and smoking is an important factor in the development and progression of AAA. Screening for AAA may be appropriate in male patients older than 65 years with a smoking history, particularly current smokers, who have carotid occlusive disease, coronary artery disease, or lower extremity occlusive disease. Ultrasound is the screening method of choice and has the benefit of being inexpensive and noninvasive. Preoperative imaging serves mainly to establish the indication for operation. The vascular surgeon comfortable with discovering potentially confusing anatomic configurations or adverse extensions of pathology at the time of operation may not require any imaging beyond ultrasound. Specific indications for arteriography include suggestion of juxtarenal aneurysm by ultrasound or physical examination, clinical evidence of lower extremity arterial occlusive disease, uncontrolled hypertension or unexplained creatinine elevation, or prior arterial reconstruction. Spiral computed tomography (CT) scan with 3-dimensional reconstruction and gadolinium magnetic resonance (MR) angiography are increasingly useful alternatives to contrast arteriography.

Lower extremity arterial evaluation: are segmental arterial blood pressures worthwhile?

PURPOSE: Physiologic observations with blood flow waveform analysis and pressure measurements can document the severity of lower extremity arterial disease. Segmental blood pressures (SEGPs) taken at the thigh, calf, and ankle are commonly used, but their utility has seldom been studied. We quantified improvements in accuracy compared with arteriography when ankle pressures alone (ABI) or SEGP data were added to velocity waveforms obtained by Doppler ultrasound. METHODS: Continuous-wave Doppler velocity waveforms were recorded at common femoral (CFA), popliteal (POP), and dorsal pedal and posterior tibial (TIB) arterial levels. Systolic SEGP data were obtained with appropriately sized upper thigh, upper calf, and ankle cuffs. Waveforms, waveforms plus ABI, and waveforms plus SEGP data from 81 patients were randomly interpreted by 14 technologists or physicians from four institutions blinded to clinical and arteriographic data. Arteriograms were assigned negative or significant, severe (>75% diameter stenosis) values for four segments: iliofemoral (CFA), superficial femoral (SFA), popliteal (POP), and infrapopliteal (TIB) arteries. A total of 9072 segmental interpretations were analyzed. RESULTS: Compared with arteriography, the accuracy of waveform analysis was 83% for severe disease at and proximal to the CFA, 79% for SFA disease, 64% for POP disease, and 73% for TIB disease. Adding ABI improved the accuracy significantly (p < 0.01) to 88% (CFA), 86% (SFA), 70% (POP), and 85% (TIB). Accuracy was inferior when SEGP data replaced ABI: 86% (CFA), 85% (SFA), 70% (POP), and 80% (TIB). CONCLUSIONS: ABIs significantly improved Doppler waveform accuracy at all levels. Compared with ABI, the addition of segmental pressure to waveform data failed to improve accuracy. Pressure measurements above the ankle may lack cost effectiveness and clinical utility.

Biplane color flow duplex intravenous intravascular ultrasound for arterial visualization.

PURPOSE: To describe a feasibility study in a sheep model using an intravascular ultrasound (IVUS) instrument in an intravenous position to produce color flow, B-mode images of arterial segments along with Doppler blood flow velocities. METHODS: Four healthy adult male sheep were anesthetized for surgical exposure of the right external jugular vein. A 9.0F sheath was also introduced in the common femoral artery for arteriography and device insertion. A 7.5-MHz ultrasound probe with 1-cm graduation markers was passed into the jugular vein. B-mode and color flow pictures were captured at aortic branches in cross and longitudinal sections. Length measurements between aortic branches and Doppler spectral velocities were obtained. Guidewire, balloon, and stent maneuvers were monitored by the stationary intravenous IVUS probe. RESULTS: High-quality visualization of the entire abdominal aorta and its branches was achieved in all animals. With the probe stationary in the vena cava, a 1.5-cm linear segment of the aorta could be continuously observed in both B-mode and color flow ultrasound scans. Insertion and implantation of a Palmaz balloon-expandable stent was guided by intravenous IVUS alone. Selective catheterization of the right renal artery was followed visually by moving the intravenous IVUS probe sequentially. CONCLUSIONS: Intravenous IVUS appears feasible as a guidance and monitoring tool for endovascular interventions. While conventional IVUS provides only cross-sectional images in B-mode, intravenous IVUS captures color flow and Doppler velocity data as well. These added ultrasound modalities may offer potential advantages for guidance of endovascular procedures and endoleak detection.

Carotid stenting versus carotid endarterectomy: update on the controversy.

Carotid stenting has been a controversial subject from the outset. This discussion examines three areas: What is the basis for clinical investigation of carotid stenting? How do the results seem to compare with current surgical practice? Are there important things we do not know about carotid stenting? Does carotid stenting produce equal or better stroke prevention over a significant period than conventional therapy? Is the short-term morbidity, both neurological and general, better than with carotid endarterectomy? Does carotid stenting reduce cost? The results of recent series of carotid endarterectomy, some from National Institutes of Health (NIH)-funded randomized studies with peer-reviewed data, others from large referral centers or large regional experiences, and the results of several single-institution case series of carotid stenting that are reported in complete manuscript form are summarized. At least four industry-sponsored trials of carotid stent technology use are being undertaken in the United States as of the fall of 1997. Considering that angioplasty and stenting in other vessels has been used in many thousands of patients for over a decade, it is surprising that some basic issues are not resolved more clearly than they seem to be. Specifically in relation to the carotid lesion, seven questions are posed that frame some controversial aspects of the role of carotid stenting in stroke prevention.

Imaging modalities for aortic endografting.

One of the most fundamental and influential differences between conventional surgery and endovascular grafting for aortic aneurysm is the central role of imaging in every aspect of management. This review summarizes five imaging techniques for aortic endografting: intravascular ultrasound, contrast angiography, conventional computed tomography (CT), spiral CT with image processing, and magnetic resonance angiography (MRA). External ultrasound and intravascular ultrasound have important relevance to endovascular aortic surgery. Artifacts of arteriography include magnification, thrombus effect, fore-shortening of tortuosity, loss of luminal detail, parallax error, and projection errors. Conventional CT scans have artifacts and difficulties also. Diameter measurement by CT suffers from methodology errors and observer variability. If conventional CT and angiography are used for endovascular aortic graft planning, both should be obtained since neither alone provides sufficient data. The use of spiral CT scanning and computerized image processing has clearly aided the preoperative definition of aneurysm morphology both in terms of dimensional accuracy and by adding diagnostic information. MRA is capable of producing three-dimensional images, axial sections, and longitudinal projections in any plane. It can detect blood flow without contrast medium, but gadolinium enhances MRA by avoiding the "signal dropout" artifact. Technology exists to provide new forms of imaging for endovascular surgery that combines three-dimensional models with on-line image data in a process called "data fusion." This may offer improved ease and accuracy for conducting endovascular procedures in the future.