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.

Role of endovascular therapies in the management of diverse thoracic aortic pathology.

Stent grafts are currently indicated for treatment of chronic aneurysmal disease of the descending thoracic aorta. At most centers of excellence, this technique has become the preferred treatment modality for this pathologic process. Many centers are also reporting excellent outcomes using a variety of debranching procedures to expand the anatomic limits of therapeutic intervention. These debranching procedures enable proximal extension of stent grafts into the transverse aortic arch and similarly enable distal extension into the visceral portion of the abdominal aorta. Thoracic aortic disease, however, is not limited to aneurysmal pathology. In our experience, at least half of all patients with major thoracic aortic pathology will have nonaneurysmal disease processes. Frequently, these patients are high-risk candidates for the performance of open surgical intervention. The reduced procedural morbidity and mortality observed with thoracic endovascular aortic repair when compared with open surgical intervention have catalyzed the investigation of stent grafts in the management of nonaneurysmal pathologic processes. This therapy has been successfully applied to a variety of diverse thoracic aortic pathologies, including aortic dissection, aortic transection, penetrating atherosclerotic ulcers, embolic lesions, and aortic coarctation. The focus of this article is on the latter 3 of these pathologies.

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.

Hybrid procedures for thoracoabdominal aortic aneurysms.

Treatment of thoracic aortic pathology has been rapidly changing in the 5 years since US Food and Drug Administration approval of thoracic stent grafts. Although not specifically evaluated in any of the major clinical trials to date, adjunctive techniques are being increasingly used to expand the applicability of stent-graft technology to patients with more extensive thoracoabdominal aortic aneurysms and dissections. Details of procedural techniques have been delineated by several aortic specialists, resulting in a trend toward standardization of effective strategies. Despite this trend, significant variability is evident in the outcomes of reported series. The objective of this article is to analyze published reports of hybrid procedures involving complete visceral debranching of the aorta and endovascular exclusion of the thoracoabdominal aortic aneurysms.

Successful management of concomitant aortoesophageal and aortotracheal fistulae secondary to a thoracic aortic aneurysm: case report and review of literature.

Thoracic aortic aneurysm with fistulization into the trachea or the esophagus is usually a lethal complication. An unusual case of combined aortotracheal and aortoesophageal fistulae is presented here. The patient had a successful outcome after resection of the aneurysm with tracheal repair and esophageal resection. A review of literature on this subject is also included in this manuscript.