Quantification of carotid plaque lipid content with magnetic resonance T2 mapping in patients undergoing carotid endarterectomy.

BACKGROUND AND PURPOSE: Techniques to stratify subgroups of patients with asymptomatic carotid artery disease are urgently needed to guide decisions on optimal treatment. Reliance on estimates of % luminal stenosis has not been effective, perhaps because that approach entirely disregards potentially important information on the pathological process in the wall of the artery. METHODS: Since plaque lipid is a key determinant of plaque behaviour we used a newly validated, high-sensitivity T2-mapping MR technique for a systematic survey of the quantity and distribution of plaque lipid in patients undergoing endarterectomy. Lipid percentage was quantified in 50 carotid endarterectomy patients. Lipid distribution was tested, using two imaging indices (contribution of the largest lipid deposit towards total lipid (LLD %) and a newly-developed LAI 'lipid aggregation index'). RESULTS: The bifurcation contained maximal lipid volume. Lipid percentage was higher in symptomatic vs. asymptomatic patients with degree of stenosis (DS ≥ 50%) and in the total cohort (P = 0.013 and P = 0.005, respectively). Both LLD % and LAI was higher in symptomatic patients (P = 0.028 and P = 0.018, respectively), suggesting that for a given plaque lipid volume, coalesced deposits were more likely to be associated with symptomatic events. There was no correlation between plaque volume or lipid content and degree of luminal stenosis measured on ultrasound duplex (r = -0.09, P = 0.53 and r = -0.05, P = 0.75), respectively. However, there was a strong correlation in lipid between left and right carotid arteries (r = 0.5, P <0.0001, respectively). CONCLUSIONS: Plaque lipid content and distribution is associated with symptomatic status of the carotid plaque. Importantly, plaque lipid content was not related to the degree of luminal stenosis assessed by ultrasound. Determination of plaque lipid content may prove useful for stratification of asymptomatic patients, including selection of optimal invasive treatments.

Quantification of Lipid-Rich Core in Carotid Atherosclerosis Using Magnetic Resonance T2 Mapping: Relation to Clinical Presentation.

OBJECTIVES: The aim of this study was to: 1) provide tissue validation of quantitative T2 mapping to measure plaque lipid content; and 2) investigate whether this technique could discern differences in plaque characteristics between symptom-related and non-symptom-related carotid plaques. BACKGROUND: Noninvasive plaque lipid quantification is appealing both for stratification in treatment selection and as a possible predictor of future plaque rupture. However, current cardiovascular magnetic resonance (CMR) methods are insensitive, require a coalesced mass of lipid core, and rely on multicontrast acquisition with contrast media and extensive post-processing. METHODS: Patients scheduled for carotid endarterectomy were recruited for 3-T carotid CMR before surgery. Lipid area was derived from segmented T2 maps and compared directly to plaque lipid defined by histology. RESULTS: Lipid area (%) on T2 mapping and histology showed excellent correlation, both by individual slices (R = 0.85, p < 0.001) and plaque average (R = 0.83, p < 0.001). Lipid area (%) on T2 maps was significantly higher in symptomatic compared with asymptomatic plaques (31.5 ± 3.7% vs. 15.8 ± 3.1%; p = 0.005) despite similar degrees of carotid stenosis and only modest difference in plaque volume (128.0 ± 6.0 mm3 symptomatic vs. 105.6 ± 9.4 mm3 asymptomatic; p = 0.04). Receiver-operating characteristic analysis showed that T2 mapping has a good ability to discriminate between symptomatic and asymptomatic plaques with 67% sensitivity and 91% specificity (area under the curve: 0.79; p = 0.012). CONCLUSIONS: CMR T2 mapping distinguishes different plaque components and accurately quantifies plaque lipid content noninvasively. Compared with asymptomatic plaques, greater lipid content was found in symptomatic plaques despite similar degree of luminal stenosis and only modest difference in plaque volumes. This new technique may find a role in determining optimum treatment (e.g., providing an indication for intensive lipid lowering or by informing decisions of stents vs. surgery).

Cell-wall properties contributing to improved deconstruction by alkaline pre-treatment and enzymatic hydrolysis in diverse maize (Zea mays L.) lines.

A maize (Zea mays L. subsp. mays) diversity panel consisting of 26 maize lines exhibiting a wide range of cell-wall properties and responses to hydrolysis by cellulolytic enzymes was employed to investigate the relationship between cell-wall properties, cell-wall responses to mild NaOH pre-treatment, and enzymatic hydrolysis yields. Enzymatic hydrolysis of the cellulose in the untreated maize was found to be positively correlated with the water retention value, which is a measure of cell-wall susceptibility to swelling. It was also positively correlated with the lignin syringyl/guaiacyl ratio and negatively correlated with the initial cell-wall lignin, xylan, acetate, and p-coumaric acid (pCA) content, as well as pCA released from the cell wall by pre-treatment. The hydrolysis yield following pre-treatment exhibited statistically significant negative correlations to the lignin content after pre-treatment and positive correlations to the solubilized ferulic acid and pCA. Several unanticipated results were observed, including a positive correlation between initial lignin and acetate content, lack of correlation between acetate content and initial xylan content, and negative correlation between each of these three variables to the hydrolysis yields for untreated maize. Another surprising result was that pCA release was negatively correlated with hydrolysis yields for untreated maize and, along with ferulic acid release, was positively correlated with the pre-treated maize hydrolysis yields. This indicates that these properties that may negatively contribute to the recalcitrance in untreated cell walls may positively contribute to their deconstruction by alkaline pre-treatment.

An assessment of between-recti distance and divarication in patients with and without abdominal aortic aneurysm.

INTRODUCTION: The study assessed whether there is a greater incidence of divarication of the recti and whether between-recti distance is greater in patients with abdominal aortic aneurysm (AAA). PATIENTS AND METHODS: The study consisted of two parts: a radiological and a clinical assessment. All patients with a confirmed AAA on computerised tomography were included and compared with patients in whom AAA was excluded with imaging. Between-recti distance was measured using a computerised image viewer and clinical divarication was assessed by a surgical registrar or consultant. RESULTS: In the radiological part of the study, 108 patients with AAA were compared with 84 with colorectal cancer. Median between-recti distance was 38 mm (range, 25-59 mm) in the AAA group and 27 mm (range, 20-44.5 mm) in the non-AAA group (P=0.006). AAA diameter did not correlate with between-recti distance. The clinical study included 50 patients (25 AAA). The groups were well matched, with only a greater incidence of diabetes in the AAA group (20% vs 0%; P=0.018). AAA patients were more likely to have clinically detected divarication of the recti (76% vs 36%; P=0.004). CONCLUSIONS: Patients with AAA have greater radiological and clinical evidence of divarication. It is suggested that patients with divarication be screened for AAA.

Spontaneous rupture of the superficial femoral artery treated with endovascular stent-grafting.

Spontaneous rupture of the superficial femoral artery (SFA) is rare. It may occur in the presence of an SFA aneurysm or in a nonaneurysmal, but usually atherosclerotic, artery. Previously these ruptures have been treated by surgical exclusion, often with bypass grafting. We report a case of spontaneous rupture of a nonaneurysmal SFA treated successfully with endovascular stent-grafting.