Performance of acoustic radiation force impulse ultrasound imaging for carotid plaque characterization with histologic validation.

OBJECTIVE: Stroke is commonly caused by thromboembolic events originating from ruptured carotid plaque with vulnerable composition. This study assessed the performance of acoustic radiation force impulse (ARFI) imaging, a noninvasive ultrasound elasticity imaging method, for delineating the composition of human carotid plaque in vivo with histologic validation. METHODS: Carotid ARFI images were captured before surgery in 25 patients undergoing clinically indicated carotid endarterectomy. The surgical specimens were histologically processed with sectioning matched to the ultrasound imaging plane. Three radiologists, blinded to histology, evaluated parametric images of ARFI-induced peak displacement to identify plaque features such as necrotic core (NC), intraplaque hemorrhage (IPH), collagen (COL), calcium (CAL), and fibrous cap (FC) thickness. Reader performance was measured against the histologic standard using receiver operating characteristic curve analysis, linear regression, Spearman correlation (ρ), and Bland-Altman analysis. RESULTS: ARFI peak displacement was two-to-four-times larger in regions of NC and IPH relative to regions of COL or CAL. Readers detected soft plaque features (NC/IPH) with a median area under the curve of 0.887 (range, 0.867-0.924) and stiff plaque features (COL/CAL) with median area under the curve of 0.859 (range, 0.771-0.929). FC thickness measurements of two of the three readers correlated with histology (reader 1: R2 = 0.64, ρ = 0.81; reader 2: R2 = 0.89, ρ = 0.75). CONCLUSIONS: This study suggests that ARFI is capable of distinguishing soft from stiff atherosclerotic plaque components and delineating FC thickness.

Balancing 'fistula first' with a 'catheter last' strategy.

Endovascular treatment, in general, is a safe and effective method to assist a fistula to maturation, although this does not mean that surgical revision is not better in some patients. An experienced interventionalist should be able to discern the most appropriate treatment modality based upon physical exam, duplex ultrasound, and/ or fistulogram. The care of a hemodialysis patient is truly a team endeavor, including the primary care physician, nephrologists, dialysis nurses and coordinators, and the interventionalists. Each must be aware that options exist to assist many slowly or non-maturing fistulas in order to establish a usable, functional fistula as soon as possible to limit the frequent complications associated with tunneled catheters. Even diffusely small veins are not beyond the reach of therapy as evidenced with the BAM procedure. Early evaluation following fistula placement (three to four weeks) with quick referral to an experienced interventionalist is crucial. There is emerging data suggesting that there is no negative effect on patency with early cannulation of fistulas, even as soon as one month. Perhaps in the near future we might see an even greater impact on the prevalence of tunneled catheters with the emergence of earlier cannulation of fistulas, along with more aggressive intervention to slowly maturing fistulas, such as the BAM procedure. As experience with the BAM procedure grows, there may be a role for BAM in patients with a suboptimal vein on preoperative vein mapping (< 2.5 mm). These patients, who traditionally would have received a prosthetic graft, might be candidates for fistula placement followed by a preplanned BAM, initiated within weeks of the initial placement. The cost effectiveness and utility of such a strategy is unstudied and would be a good subject for future trials.

Non-invasive in vivo characterization of human carotid plaques with acoustic radiation force impulse ultrasound: comparison with histology after endarterectomy.

Ischemic stroke from thromboembolic sources is linked to carotid artery atherosclerotic disease with a trend toward medical management in asymptomatic patients. Extent of disease is currently diagnosed by non-invasive imaging techniques that measure luminal stenosis, but it has been suggested that a better biomarker for determining risk of future thromboembolic events is plaque morphology and composition. Specifically, plaques that are composed of mechanically soft lipid/necrotic regions covered by thin fibrous caps are the most vulnerable to rupture. An ultrasound technique that non-invasively interrogates the mechanical properties of soft tissue, called acoustic radiation force impulse (ARFI) imaging, has been developed as a new modality for atherosclerotic plaque characterization using phantoms and atherosclerotic pigs, but the technique has yet to be validated in vivo in humans. In this preliminary study, in vivo ARFI imaging is presented in a case study format for four patients undergoing clinically indicated carotid endarterectomy and compared with histology. In two type Va plaques, characterized by lipid/necrotic cores covered by fibrous caps, mean ARFI displacements in focal regions were high relative to the surrounding plaque material, suggesting soft features were covered by stiffer layers within the plaques. In two type Vb plaques, characterized by heavy calcification, mean ARFI peak displacements were low relative to the surrounding plaque and arterial wall, suggesting stiff tissue. This pilot study illustrates the feasibility and challenges of transcutaneous ARFI for characterizing the material and structural composition of carotid atherosclerotic plaques via mechanical properties, in humans, in vivo.

Coverage of the left subclavian artery during thoracic endovascular aortic repair.

BACKGROUND: Thoracic aortic stent grafts require proximal and distal landing zones of adequate length to effectively exclude thoracic aortic lesions. The origins of the left subclavian artery and other aortic arch branch vessels often impose limitations on the proximal landing zone, thereby disallowing endovascular repair of more proximal thoracic lesions. METHODS: Between October 2000 and November 2005, 112 patients received stent grafts to treat lesions involving the thoracic aorta. The proximal aspect of the stent graft partially or totally occluded the origin of at least one great vessel in 28 patients (25%). The proximal attachment site was in zone 0 in one patient (3.6%), zone 1 in three patients (10.7%), and zone 2 in 24 patients (85.7%). Patients with proximal implantation in zones 0 or 1 underwent debranching procedures of the supra-aortic vessels before stent graft repair. In one patient who underwent zone 1 deployment, the left subclavian artery was revascularized before stent graft deployment. Among patients who underwent zone 2 deployment with partial or complete occlusion of the left subclavian artery, none underwent prior revascularization. Patients were assessed postoperatively and at follow-up for development of neurologic symptoms as well as symptoms of left upper extremity claudication or ischemia. RESULTS: Mean follow-up was 7.3 months. Among the 24 patients with zone 2 implantation, 10 (42%) had partial left subclavian artery coverage at the time of their primary procedure. A total of 19 patients experienced complete cessation of antegrade flow through the origin of the left subclavian artery without revascularization at the time of the initial endograft repair as a result of a secondary procedure or as a consequence of left subclavian artery thrombosis. Left upper extremity symptoms developed in three (15.8%) patients that did not warrant intervention, and rest pain developed in one (5.3%), which was treated with the deployment of a left subclavian artery stent. Two primary (type IA and type III) endoleaks (7.1%) and one secondary endoleak (type IA) (3.6%) were observed in patients who underwent zone 2 deployment. Three cerebrovascular accidents were observed. Thoracic aortic lesions were successfully excluded in all patients who underwent supra-aortic debranching procedures. CONCLUSION: Intentional coverage of the origin of the left subclavian artery to obtain an adequate proximal landing zone during endovascular repair of thoracic aortic lesions is well tolerated and may be managed expectantly, with some exceptions.

Natural history of limbs with arterial insufficiency and chronic ulceration treated without revascularization.

OBJECTIVES: The natural history of limbs affected by ischemic ulceration is poorly understood. In this report, we describe the outcome of limbs with stable chronic leg ulcers and arterial insufficiency that were treated with wound-healing techniques in patients who were not candidates for revascularization. METHODS: A prospectively maintained database of limb ulcers treated at a comprehensive wound center was used to identify patients with arterial insufficiency, defined as an ankle-brachial index (ABI) <0.7 or a toe pressure <50 mm Hg. Patients were treated without revascularization when medical comorbidity or anatomic considerations did not allow revascularization with acceptable risk. Ulcers were treated with a protocol emphasizing pressure relief, débridement, infection control, and moist wound healing. Risk factors analyzed for their affect on healing and amputation risk included age, gender, diabetes mellitus, chronic renal insufficiency (serum creatinine > 2.5 mg/dL), severity of ischemia measured by ABI or toe pressure, wound grade, wound size, and wound location. RESULTS: Between January 1999 and March 2005, 142 patients with 169 limbs having arterial insufficiency and full-thickness ulceration were treated without revascularization. Mean patient age was 70.8 +/- 4.5. Diabetes mellitus was present in 70.4% of limbs and chronic renal insufficiency in 27.8%. Toe amputations or other foot-sparing procedures were performed in 28% of limbs. Overall, limb loss occurred in 37 patients. By life-table analysis, 19% of limbs required amputation < or =6 months of initial treatment and 23% at 12 months. Complete wound closure was achieved in 25% by 6 months and in 52% by 12 months. Statistical analysis showed a correlation between ABI and the risk of limb loss. In patients with an ABI <0.5, 28% and 34% of limbs experienced limb loss at 6 and 12 months, respectively, compared with 10% and 15% of limbs in patients with an ABI >0.5 (P = .01). The only risk factor associated with wound closure was initial wound size (P < .005). CONCLUSIONS: Limb salvage can be achieved in most patients with arterial insufficiency and uncomplicated chronic nonhealing limb ulcers using a program of wound management without revascularization. Healing proceeds slowly, however, requiring more than a year in many cases. Patients with an ABI <0.5 are more likely to require amputation. Interventions designed to improve outcomes in critical limb ischemia should stratify outcomes based on hemodynamic data and should include a comparative control group given the natural history of ischemic ulcers treated in a dedicated wound program.

Effect of challenging neck anatomy on mid-term migration rates in AneuRx endografts.

OBJECTIVE: To establish the effect of challenging neck anatomy on the mid- and long-term incidence of migration with the AneuRx bifurcated device in patients treated after Food and Drug Administration approval and to identify the predictive factors for device migration. METHODS: Prospectively maintained databases at the University of North Carolina (UNC) and Washington University (WU) were used to identify 595 patients (UNC, n = 230; WU, n = 365) who underwent endovascular repair of an infrarenal abdominal aortic aneurysm with the AneuRx bifurcated stent graft. Those patients with at least 30 months of follow-up were identified and underwent further assessment of migration (UNC, n = 25; WU, n = 59) by use of multiplanar reconstructed computed tomographic scans. RESULTS: Eighty-four patients with a mean follow-up time of 40.3 months (range, 30-55 months) were studied. Seventy percent of the patients (n = 59) met all inclusion criteria for neck anatomy (length, angle, diameter, and quality) as defined by the revised instructions for use guidelines and are referred to as those with favorable neck anatomy (FNA). The remaining 25 patients retrospectively fell outside of the revised instructions for use guidelines and are referred to as those with unfavorable neck anatomy (UFNA). Life-table analysis for FNA patients at 2 and 4 years revealed a migration rate of 0% and 6.1%, respectively. For UFNA patients, it was 24.0% and 42.1% at 2 and 4 years, respectively (P < .0001). The overall (FNA and UFNA) migration rate was 7.1% and 17.1% at 2 and 4 years, respectively. Overall, late graft-related complications occurred in 38% of patients (FNA, 27%; UFNA, 64%; P = .003; relative risk, 1.7). There was no incidence of late rupture or open conversion. The relative risk of migration for UFNA patients was 2.5 compared with FNA patients (P = .0003). A larger neck angle and a longer initial graft to renal artery distance were predictors of migration, whereas shorter neck length approached but did not reach statistical significance. CONCLUSIONS: Patients who have unfavorable aneurysm neck anatomy experience significantly higher migration, device-related complication, and secondary intervention rates. However, there was no incidence of open conversion, rupture, or abdominal aortic aneurysm-related death, thereby supporting the AneuRx device as a feasible alternative to open repair even in patients with challenging neck characteristics. Enhanced surveillance should be used in these high-risk patients.

Endovascular repair of lesions involving the descending thoracic aorta.

BACKGROUND: Vascular lesions involving the thoracic aorta are often life-threatening conditions that carry significant morbidity and mortality with traditional open surgical repair. Preliminary results suggest that endovascular therapy is an effective and possibly advantageous treatment for diseases of the descending thoracic aorta. METHODS: Between October 2000 and May 2004, 50 consecutive patients underwent endovascular stent-grafting of lesions involving the descending thoracic aorta. Attempted stent-graft deployment was performed electively in 39 patients and emergently in 11. The pathology of electively treated aortic lesions included degenerative/atherosclerotic aneurysms (n = 24), pseudoaneurysms (n = 11), aortic dissections (n = 2), and penetrating ulcers (n = 2). Emergently treated aortic lesions were for acute rupture due to infectious (mycotic) aneurysms (n = 4), atherosclerotic/degenerative aneurysms (n = 3), acute type B dissections (n = 2), and acute transections (n = 2). Devices used include Talent (n = 45), AneuRx aortic cuffs (n = 2), custom-fabricated Gianturco-Dacron grafts (n = 2), and a modified Cook-Zenith abdominal aortic graft (n = 1). Follow-up was performed at 1-month, 6-months, 1-year, and annually thereafter. RESULTS: Primary technical success, defined as successful deployment and exclusion of the lesion without evidence of type I or type III endoleak, was achieved in 48 (96%) of 50 patients. In one patient, the procedure was terminated due to inability to access the iliac vessels. In another patient, a type III endoleak was observed at the completion of the primary procedure that required deployment of an additional stent-graft component 2 months later. Of the 49 patients who received endografts, seven underwent secondary procedures to correct endoleaks, with five of these seven requiring the deployment of additional endovascular stent-graft components. Major complications included four in-hospital deaths, with three of these occurring in patients treated emergently. Additionally, respiratory failure (n = 6), multisystem organ failure (n = 2), cerebrovascular accident (n = 2), retroperitoneal hematoma (n = 2), acute renal insufficiency (n = 1), and pulmonary embolus (n = 1) were also observed. The overall endoleak rate was 20%, with five primary (< or = 30 days) and five secondary (> 30 days) endoleaks observed. Five of the endoleaks were treated with the deployment of one or more additional endovascular stent-graft components. Two of the endoleaks were treated with endovascular balloon remolding. Mean follow-up was 271 days. There were no aneurysm ruptures or aneurysm-related deaths. CONCLUSIONS: Endovascular treatment of vascular lesions involving the descending thoracic aorta can be safely performed with low morbidity in high-risk patients. Endovascular repair may become an attractive alternative for the treatment of a wide range of pathology along this vascular territory.