Effects of lipid-lowering therapy on coronary artery remodeling

Arterial remodeling of basilar atherosclerosis in isolated pontine infarction

Isolated pontine infarctions are usually classified as paramedian pontine infarction (PPI) and lacunar pontine infarction (LPI). Although they have different shapes and locations, some recent studies proved that they might both be associated with basilar artery atherosclerosis in pathogenesis. This study aimed to explore the difference of basilar artery remodeling between two subtypes of pontine infarctions. Patients with PPI or LPI were scanned by High-resolution MRI (HR-MRI). The MR images of patients with basilar artery atherosclerosis were further analyzed to measure the vessel, lumen and wall areas at different segments of basilar arteries. Stenosis rate and remodeling index were calculated according to which arterial remodeling was divided into positive, intermediate and negative remodeling. Vascular risk factors and remodeling-related features were compared between PPI and LPI, and also between patients with and without positive remodeling. 34 patients with PPI and 21 patients with LPI had basilar artery atherosclerosis identified by HR-MRI. Positive remodeling was dominant in LPI group while in PPI group, three subtypes of remodeling were equal. Patients with positive remodeling had higher levels of low-density lipoprotein and homocysteine. Positive remodeling of basilar artery might reflect the low stability of basilar atherosclerotic plaques, which was more closely associated with LPI than PPI.

Positive remodeling at 3 year follow up is associated with plaque-free coronary wall segment at baseline: a serial IVUS study

AIMS

At present it is unknown what limits the arterial remodeling process during atherosclerotic plaque formation. In healthy arteries remodeling is regulated by the shear stress induced response by the endothelium. As endothelium at the plaque site is assumed to be dysfunctional, we tested the hypothesis that plaque free wall (PFW) determines vascular remodeling during atherosclerotic plaque build-up.

METHODS & RESULTS

66 human coronary ROIs (38 patients) were studied at baseline and at 3 years follow up applying intravascular ultrasound (IVUS). From the IVUS images the lumen and external elastic membrane contours were delineated to assess wall thickness (WT), vessel area (VA), Plaque Area (PA) and plaque burden (PA/VA*100%). WT < 0.5 mm was defined as normal and determined the arc of the PFW (0-360°). Positive remodeling was defined as relative difference of VA over time >5%. At baseline, IVUS-PFW was inversely related to plaque burden (p < 0.05). Positive remodeling was most frequently observed in ROIs with IVUS-PFW > 180° (i.e. larger than half of the circumference) compared to PFW < 180° (55% vs. 12%, p < 0.05). Accordingly, plaques with IVUS-PFW > 180° at baseline had the largest change in VA (1.1 ± 2.1 vs. -0.4 ± 0.6 mm(2), p < 0.05) with an odds ratio of 9.2 to develop positive remodeling.

CONCLUSIONS

Our serial IVUS data show that IVUS-PFW is a determinant of vascular remodeling. ROIs with PFW > 180 at baseline had the highest probability to undergo positive remodeling.

Vascular remodeling in ApoE-deficient mice: diet dependent modulation after carotid ligation

Vascular remodeling is influenced by trauma and proatherogenic factors such as cholesterol. It has been shown that cholesterol exerts a direct effect on vessel wall structure. In this study we evaluated the effects of vascular trauma and cholesterol treatment on vascular remodeling and plaque integrity in carotid ligated ApoE-deficient mice. The right carotid artery was ligated in mice fed regular chow or cholesterol and fat containing diet. After 4 weeks left (non-ligated) and right (ligated) carotids were prepared. For studying vascular remodeling the vascular areas were evaluated morphometrically by calculating the areas from circumference measurements on Verhoff-van Gieson stains. The cellular and structural features of the plaque were analyzed by histological staining and immunohistochemistry. Under regular chow total vessel area decreased by 35% (p<0.001); cholesterol-rich diet led to an increase by 20% (p<0.05). In both feeding groups ligated carotids presented neointima development. The medial area increased only in mice fed regular chow. The luminal area was reduced by 80% (regular chow: p<0.001) and by 90% (cholesterol-rich diet: p<0.01). Regular chow led to structured plaques showing the typical features of stable plaques. Under cholesterol diet well defined plaque structures were missing. These lesions were characterized by numerous macrophages, few mostly PCNA positive smooth muscle cell (SMC) and less collagen particularly in the shoulder region. Our data indicate that in ApoE-deficient mice both direction of the remodeling response and lesion integrity are due to the diet applied: regular chow led to constrictive remodeling, whereas cholesterol and fat containing diet was associated with an adaptive response. Our data further indicate that the direction of response is not only related to the macrophage content but also to a proliferative intimal SMC-phenotype. Our data implicate that high serum cholesterol levels are not only inducers of plaque instability but also of the so far "positively recorded" compensatory remodeling.

Mapping spatial and temporal changes in carotid atherosclerosis from three-dimensional ultrasound images

This study was designed to evaluate changes in carotid atherosclerosis using plaque and wall thickness maps derived from three-dimensional ultrasound (3DUS) images. Five subjects with carotid stenosis were scanned at baseline and 3 mo as part of a placebo-controlled intensive statin treatment study and three subjects with moderate atherosclerosis were scanned at baseline and again within 14 +/- 2 d. 3DUS-derived vessel wall volume (VWV) was measured using manual segmentation to provide segmentation contours that were used to generate scan and rescan carotid atherosclerosis thickness maps and thickness difference maps. There was no significant difference in VWV between scan and rescan for the three subjects scanned twice in 2 wk or the single subject treated with placebo. There was a significant difference between scan and rescan VWV for carotid stenosis subjects treated with atorvastatin (p < 0.001). Carotid atherosclerosis thickness difference maps showed visual qualitative evidence of thickness changes in vessel wall and plaque thickness in the common carotid artery for all statin-treated subjects and no change in a placebo-treated subject and subjects scanned twice in 2 wk. Carotid atherosclerosis thickness difference maps generated from 3DUS images provide evidence of vessel wall and plaque thickness changes for all subjects assessed.

Effect of Simvastatin on Coronary Lesion Site Remodeling: A Serial Intravascular Ultrasound Study

BACKGROUND

Direct evidence of coronary artery remodeling can be derived only from serial changes in the external elastic membrane (EEM) and plaque area. The aim of the study was to assess the effect of simvastatin on coronary remodeling in serial intravascular ultrasound (IVUS) studies.

METHODS

In 39 male patients ECG-triggered transducer pullback IVUS was performed at baseline, after 3 months on a lipid-lowering diet (control period), and after another 12 months of simvastatin 40 mg/day. The lesion site was the image slice with maximum plaque burden at 3 months.

RESULTS

Absolute changes in the EEM area correlated significantly with changes in plaque area during the control period [B = 0.966, r = 0.792 (95% CI 0.71-1.22); p < 0.001] and during simvastatin treatment [B = 0.945, r = 0.822 (95% CI 0.73-1.16); p < 0.001], but there was no significant difference in the slope (delta EEM/delta plaque) between the two time intervals. After 12 months of simvastatin, there was a significant reduction in the lesion EEM area of 4.6% (p = 0.006) and in the lesion plaque area of 5.9% (p < 0.001), but there was no change in reference measurements. As a result, the remodeling index was reduced by simvastatin from 1.01 +/- 0.12 to 0.95 +/- 0.09 (p < 0.001).

CONCLUSION

Simvastatin decreases the remodeling index by reducing lesion, but not reference plaque and EEM area. However, simvastatin does not affect direct evidence of remodeling (delta EEM/delta plaque) obtained using serial IVUS studies.

Paradoxical increase in lumen size during progression of coronary atherosclerosis: Observations from the REVERSAL trial

Relative changes in lumen size during progression and regression of coronary atherosclerosis remain largely unknown. We assessed these changes using serial intravascular ultrasound (IVUS). From the baseline IVUS interrogations of the Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) trial, 210 focal coronary lesions with <50% angiographic stenosis were identified. Lesions were matched to the follow-up IVUS, performed after 18 months of treatment with atorvastatin 80 mg/day or pravastatin 40 mg/day. Changes in external elastic membrane (EEM) and lumen areas of lesions demonstrating progression and regression (i.e. increased and decreased atheroma area) were examined. In progressors (n=128), there was 1.34 mm(2) increase in EEM area for every 1mm(2) increase in atheroma area (r=0.72, p<0.0001). This resulted in 0.34 mm(2) increase in lumen area for every 1mm(2) increase in atheroma area (r=0.25, p=0.004). In contrast, there was no significant change in lumen area with regression of disease (n=82, r=-0.06, p=0.59). Progression of coronary atherosclerosis can be associated with a paradoxical increase in lumen cross-sectional area, whereas regression is not associated with any change in lumen area. Measurement of changes in lumen size may not be an accurate method to study progression and regression of atherosclerotic lesions with <50% stenosis.

Static and serial assessments of coronary arterial remodeling are discordant: an intravascular ultrasound analysis from the Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) trial

BACKGROUND

Arterial remodeling is a major determinant of the clinical manifestations of coronary artery disease. Assessment of arterial remodeling with intravascular ultrasound (IVUS) used to rely on comparing the external elastic membrane (EEM) areas of lesion and reference sites at a single time point (static assessment). Recently, performance of serial IVUS provided the opportunity for direct assessment of remodeling. Our aim was to study the concordance of the static and serial methods.

METHODS

We identified 210 focal coronary lesions on the baseline IVUS interrogations of the REVERSAL trial. A follow-up IVUS was performed at 18 months. Static assessment was performed by calculating the remodeling index (RI) (lesion EEM area / reference EEM area) and serial assessment by comparing the changes in atheroma and EEM areas at follow-up.

RESULTS

Using the serial method, there was a 1.24 mm2 increase in EEM area for every 1 mm2 increase in atheroma area at the lesion site, which was indicative of expansive (overcompensatory) remodeling. By using the static method, the RI was paradoxically lower at follow-up (1.062 +/- 0.15 at baseline vs 1.027 +/- 0.14 at follow-up, P < .001), indicating a trend toward constrictive remodeling. The reason for decreased RI at follow-up was the relatively larger expansion of the EEM areas at the reference sites.

CONCLUSIONS

Static and serial assessments of arterial remodeling are discordant. This is due to concomitant remodeling of the reference sites used in the static assessment. Intravascular ultrasound performed at a single point in time does not reflect the dynamic remodeling response.

Effect of atherosclerotic regression on total luminal size of coronary arteries as determined by intravascular ultrasound

We assessed vascular changes during atherosclerosis regression. Compensatory enlargement of coronary arteries accommodates plaque burden during atherosclerosis development. Lipid-lowering therapy has altered the natural history of coronary atherosclerosis, but the arterial changes that occur during disease regression need to be clarified. Intravascular ultrasound was performed at baseline and after approximately 18 months in 432 patients with coronary disease. Mean plaque, lumen, and total vessel area were computed in a 30-mm coronary segment of interest. Mean low-density lipoprotein cholesterol level was 2.4 mmol/L, and 88% of patients received statins. Overall, changes in plaque and total vessel areas were highly correlated (r = 0.82, p <0.0001). Among the 227 patients with plaque regression, the plaque area decrease was -0.58 +/- 0.54 mm(2), and changes in total vessel and lumen areas were -1.02 +/- 1.10 and -0.44 +/- 0.86 mm(2), respectively. The decrease in plaque area correlated better with the change in total vessel area (r = 0.64, p <0.0001) than with the change in lumen area (r = 0.20, p = 0.003). The relation between plaque regression and decrease in total vessel area was significantly better (p = 0.019) for patients with a >40% atheroma area (r = 0.72; p <0.0001) than for those with <or=40% (r = 0.48; p = 0.0004). In conclusion, regression of atherosclerotic plaque is generally accompanied by a decrease in total vessel size, without an increase in luminal dimensions. This reverse vascular remodeling may be responsible for the "regression paradox," whereby secondary prevention is associated with clinical benefits despite minimal improvement in coronary lumen dimensions.

Determinants of Arterial Wall Remodeling During Lipid-Lowering Therapy

Background— Coronary plaque progression and instability are associated with expansive remodeling of the arterial wall. However, the remodeling response during plaque-stabilizing therapy and its relationship to markers of lipid metabolism and inflammation are incompletely understood.

Methods and Results— Serial intravascular ultrasound (IVUS) data from the Reversal of Atherosclerosis with Aggressive Lipid Lowering Therapy (REVERSAL) trial were obtained during 18 months of intensive versus moderate lipid-lowering therapy. In a subgroup of 210 patients, focal coronary lesions with mild luminal narrowing were identified. Lumen area, external elastic membrane (EEM) area, and plaque area were determined at the lesion and proximal reference sites at baseline and during follow-up. The remodeling ratio (RR) was calculated by dividing the lesion EEM area by the reference EEM area. The relationship between the change in remodeling, change in plaque area, lipid profile, and inflammatory markers was examined. At the lesion site, a progression in plaque area (8.9±25.7%) and a decrease in the RR (−3.0±11.2%) occurred during follow-up. In multivariable analyses, the percentage change in plaque area ( P <0.0001), baseline RR ( P <0.0001), baseline lesion lumen area (0.019), logarithmic value of the change in high-sensitivity C-reactive protein ( P =0.027), and hypertension at baseline ( P =0.014) showed a significant, direct relation with the RR at follow-up. Lesion location in the right coronary artery ( P =0.006), percentage change in triglyceride levels ( P =0.049), and age ( P =0.037) demonstrated a significant, inverse relation with the RR at follow-up. Changes in LDL cholesterol, HDL cholesterol, and treatment group demonstrated no significant associations.

Conclusions— Constrictive remodeling of the arterial wall was observed during plaque-stabilizing therapy with statin medications and appears related to their antiinflammatory effects.