OBJECTIVES: The purpose of this study was to investigate the role of shear stress(SS) in plaque regression. BACKGROUND: A condition favorable to the development of atherosclerotic lesions is low oscillating SS. In the...OBJECTIVES: The purpose of this study was to investigate the role of shear stress(SS) in plaque regression. BACKGROUND: A condition favorable to the development of atherosclerotic lesions is low oscillating SS. In the descending thoracic aorta, the relationship between plaque distribution and SS has never been characterized. The regression of plaque as the result of lipid-lowering therapy is associated with reverse atherogenic mechanisms. Therefore, we investigated the role of SS in plaque regression. Magnetic resonance imaging(MRI) provides a unique opportunity to noninvasively study morphology and hemodynamics. METHODS: Cross-sectional images of atherosclerotic plaques in the descending thoracic aorta of 10 asymptomatic, hypercholesteremic patients were acquired at baseline and 24 months after starting lipid-lowering therapy by using a black-blood sequence on a 1.5-T clinical MRI system(5 mm×780 μm×780 μm). Average wall thickness(WT) was derived per quadrant. The aorta was subdivided in segments 2 cm in length starting 1 cm from the aortic arch. RESULTS: Average WT decreased with increasing distance from the arch(3.0±0.7 mm vs. 2.5±0.3 mm; p< 0.05) and showed a helical pattern from the proximal to distal segments. Phase-contrast MRI was performed in the thoracic aorta of eight healthy volunteers to derive typical average SS distribution. Shear stress predicted the location of WT(r2=0.29, p< 0.05) but did not predict plaque regression. The best predictor of plaque regression was baseline WT. CONCLUSIONS: Our data showing an association between WT and average low SS locations support the role of local hemodynamics in the development of atherosclerotic lesions in descending thoracic aorta. Furthermore, SS does not seem to be the major predictor for plaque regression by lipid-lowering interventions. Therefore, our data suggest that other mechanisms are involved in the lipid-reversal mechanism.展开更多
OBJECTIVES: This study sought to compare the effects of aggressive and conventional lipid lowering by two different dosages of the same statin on early human atherosclerotic lesions using serial noninvasive magnetic r...OBJECTIVES: This study sought to compare the effects of aggressive and conventional lipid lowering by two different dosages of the same statin on early human atherosclerotic lesions using serial noninvasive magnetic resonance imaging(MRI). BACKGROUND: Regression of atherosclerotic lesions by lipid-lowering therapy has been reported. METHODS: Using a double-blind design, newly diagnosed hypercholesterolemic patients(n=51) with asymptomatic aortic and/or carotid atherosclerotic plaques were randomized to 20 mg/day(n=29) or 80 mg/day(n=22) simvastatin. Mean follow-up was 18.1 months. A total of 93 aortic and 57 carotid plaques were detected and sequentially followed up by MRI every six months after lipid-lowering initiation. The primary MRI end point was change in vessel wall area(VWA) as a surrogate for atherosclerotic burden. RESULTS: Both statin doses reduced significantly total cholesterol(TC) and low-density lipoprotein cholesterol(LDL-C) versus baseline(p< 0.001). Total cholesterol decreased by 26%versus 33%and LDL-C by 36%versus 46%in the conventional(20 mg) versus aggressive(80 mg) simvastatin groups, respectively. Although the simvastatin 80-mg group had significantly higher baseline TC and LDL-C levels, both groups reached similar absolute values after treatment. A significant reduction in VWA was already observed by 12 months. No difference on vascular effects was detected between the randomized doses. Post-hoc analysis showed that patients reaching mean on-treatment LDL-C ≤100 mg/dl had larger decreases in plaque size. CONCLUSIONS: Effective and protracted lipid-lowering therapy with simvastatin is associated with a significant regression of atherosclerotic lesions. No difference in vessel wall changes was seen between high and conventional doses of simvastatin. Changes in vessel wall parameters are more related to LDL-C reduction rather than to the dose of statin.展开更多
文摘OBJECTIVES: The purpose of this study was to investigate the role of shear stress(SS) in plaque regression. BACKGROUND: A condition favorable to the development of atherosclerotic lesions is low oscillating SS. In the descending thoracic aorta, the relationship between plaque distribution and SS has never been characterized. The regression of plaque as the result of lipid-lowering therapy is associated with reverse atherogenic mechanisms. Therefore, we investigated the role of SS in plaque regression. Magnetic resonance imaging(MRI) provides a unique opportunity to noninvasively study morphology and hemodynamics. METHODS: Cross-sectional images of atherosclerotic plaques in the descending thoracic aorta of 10 asymptomatic, hypercholesteremic patients were acquired at baseline and 24 months after starting lipid-lowering therapy by using a black-blood sequence on a 1.5-T clinical MRI system(5 mm×780 μm×780 μm). Average wall thickness(WT) was derived per quadrant. The aorta was subdivided in segments 2 cm in length starting 1 cm from the aortic arch. RESULTS: Average WT decreased with increasing distance from the arch(3.0±0.7 mm vs. 2.5±0.3 mm; p< 0.05) and showed a helical pattern from the proximal to distal segments. Phase-contrast MRI was performed in the thoracic aorta of eight healthy volunteers to derive typical average SS distribution. Shear stress predicted the location of WT(r2=0.29, p< 0.05) but did not predict plaque regression. The best predictor of plaque regression was baseline WT. CONCLUSIONS: Our data showing an association between WT and average low SS locations support the role of local hemodynamics in the development of atherosclerotic lesions in descending thoracic aorta. Furthermore, SS does not seem to be the major predictor for plaque regression by lipid-lowering interventions. Therefore, our data suggest that other mechanisms are involved in the lipid-reversal mechanism.
文摘OBJECTIVES: This study sought to compare the effects of aggressive and conventional lipid lowering by two different dosages of the same statin on early human atherosclerotic lesions using serial noninvasive magnetic resonance imaging(MRI). BACKGROUND: Regression of atherosclerotic lesions by lipid-lowering therapy has been reported. METHODS: Using a double-blind design, newly diagnosed hypercholesterolemic patients(n=51) with asymptomatic aortic and/or carotid atherosclerotic plaques were randomized to 20 mg/day(n=29) or 80 mg/day(n=22) simvastatin. Mean follow-up was 18.1 months. A total of 93 aortic and 57 carotid plaques were detected and sequentially followed up by MRI every six months after lipid-lowering initiation. The primary MRI end point was change in vessel wall area(VWA) as a surrogate for atherosclerotic burden. RESULTS: Both statin doses reduced significantly total cholesterol(TC) and low-density lipoprotein cholesterol(LDL-C) versus baseline(p< 0.001). Total cholesterol decreased by 26%versus 33%and LDL-C by 36%versus 46%in the conventional(20 mg) versus aggressive(80 mg) simvastatin groups, respectively. Although the simvastatin 80-mg group had significantly higher baseline TC and LDL-C levels, both groups reached similar absolute values after treatment. A significant reduction in VWA was already observed by 12 months. No difference on vascular effects was detected between the randomized doses. Post-hoc analysis showed that patients reaching mean on-treatment LDL-C ≤100 mg/dl had larger decreases in plaque size. CONCLUSIONS: Effective and protracted lipid-lowering therapy with simvastatin is associated with a significant regression of atherosclerotic lesions. No difference in vessel wall changes was seen between high and conventional doses of simvastatin. Changes in vessel wall parameters are more related to LDL-C reduction rather than to the dose of statin.
