A combined "in vivo" noninvasive evaluation of carotid plaques using ultrasonography and high-resolution magnetic resonance - new insight into plaque burden and vulnerability.

BACKGROUND: Qualitative change in carotid plaques was prospectively evaluated by Gray Scale Median (GSM) analysis at repeated examinations "in vivo", in relation to quantitative change in carotid arterial geometry, as assessed by high-resolution magnetic resonance imaging (HR-MRI). PATIENTS AND METHODS: Duplex ultrasound with GSM analysis and HR-MRI at the carotid level were performed at baseline and 1- and 2-year follow up in 30 patients with < 70% carotid stenosis. Changes in GSM values (ΔGSM) were evaluated as the intra-individual difference between 2-year and baseline values. HR-MRI studies were evaluated for lumen area (LA), total vessel area (TVA), vessel wall area (VWA = TVA-LA) and normalized wall index (NWI = VWA/TVA). RESULTS: ΔGSM value distribution was divided into quartiles. Predominantly echolucent plaques with ΔGSM value in the lowest quartile (ΔGSM ≤- 8) showed a significantly greater mean 2-year LA (28.62 ± 10.9 mm2 vs. 17.88 ± 4.8 mm2, p = 0.04) and a greater mean 2-year TVA (83.64 ± 19.4 mm2 vs. 63.26 ± 9.2 mm2, p = 0.02) than predominantly echogenic plaques with ΔGSM value in the highest quartile (ΔGSM ≥8). CONCLUSIONS: Increasing echolucency during the 2-year follow up was associated with a 2-year lower degree of stenosis and higher tendency toward lumen preservation. By corroborating that plaque vulnerability is highly independent of stenosis severity, our study provided a possible new combined "in vivo" noninvasive approach for the assessment of carotid plaque vulnerability.

Intra-individual comparison of carotid and femoral atherosclerotic plaque features with in vivo MR plaque imaging.

The purpose of this study was to evaluate differences of plaque composition and morphology within the same patient in different vascular beds using non-invasive MR-plaque imaging. 28 patients (67.8 ± 7.4 years, 8 females) with high Framingham general cardiovascular disease 10-year risk score and mild-to-moderate atherosclerosis were consecutively included in the study. All subjects underwent a dedicated MRI-plaque imaging protocol using TOF and T1w and T2w black-blood-sequences with fat suppression at 1.5 T. The scan was centered on the carotid bulb of the carotid arteries and on the most stenotic lesion of the ipsilateral femoral artery, respectively. Plaques were classified according to the American Heart Association (AHA) lesion type classification and area measurements of lumen, wall and the major plaque components, such as calcification, necrotic core and hemorrhage were determined in consensus by two blinded reviewers using dedicated software (Cascade, Seattle, USA). Plaque components were recorded as maximum percentages of the wall area. Carotid arteries had larger maximum wall and smaller minimum lumen areas (p < 0.001) than femoral arteries, whereas no significant difference was find with respect to the max. NWI (p = 0.87). Prevalence of lipid-rich AHA lesion type IV/V and complicated AHA lesion type VI with hemorrhage/thrombus/fibrous cap rupture was significantly higher in the carotid arteries compared to the femoral arteries. Plaque composition as percentage of the vessel wall differed significantly between carotid and femoral arteries: Max. %necrotic core and max. %hemorrhage were significantly higher in the carotid arteries compared to the femoral arteries (p = 0.001 and p = 0.02, respectively). Max. %calcification did not differ significantly. Average stenotic degree of carotid arteries at duplex was 49.7 ± 12.5 (%). Non-invasive MR plaque-imaging is able to visualize differences in plaque composition across the vascular tree. We observed significant differences in quantitative and qualitative plaque features between carotid and femoral arteries within the same patient, which in the future could help to improve risk stratification in patients with atherosclerosis.

Progression of human carotid and femoral atherosclerosis: a prospective follow-up study by magnetic resonance vessel wall imaging.

AIMS: The time course of atherosclerosis burden in distinct vascular territories remains poorly understood. We longitudinally evaluated the natural history of atherosclerotic progression in two different arterial territories using high spatial resolution magnetic resonance imaging (HR-MRI), a powerful, safe, and non-invasive tool. METHODS AND RESULTS: We prospectively studied a cohort of 30 patients (mean age 68.3, n = 9 females) with high Framingham general cardiovascular disease 10-year risk score (29.5%) and standard medical therapy with mild-to-moderate atherosclerosis intra-individually at the level of both carotid and femoral arteries. A total of 178 HR-MRI studies of carotid and femoral arteries performed at baseline and at 1- and 2-year follow-up were evaluated in consensus reading by two experienced readers for lumen area (LA), total vessel area (TVA), vessel wall area (VWA = TVA - LA), and normalized wall area index (NWI = VWA/TVA). At the carotid level, LA decreased (-3.19%/year, P = 0.018), VWA increased (+3.83%/year, P = 0.019), and TVA remained unchanged. At the femoral level, LA remained unchanged, VWA and TVA increased (+5.23%/year and +3.11%/year, both P < 0.01), and NWI increased for both carotid and femoral arteries (+2.28%/year, P = 0.01, and +1.8%/year, P = 0.033). CONCLUSION: The atherosclerotic burden increased significantly in both carotid and femoral arteries. However, carotid plaque progression was associated with negative remodelling, whereas the increase in femoral plaque burden was compensated by positive remodelling. This finding could be related to anatomic and flow differences and/or to the distinct degree of obstruction in the two arterial territories.