Vascular remodeling in atherosclerotic coronary arteries is affected by plaque composition

Impact of plaque composition on long-term clinical outcomes in patients with coronary artery occlusive disease

BACKGROUND AND OBJECTIVES

It is unclear which plaque component is related with long-term clinical outcomes in patients with coronary artery occlusive disease (CAOD). We assessed the relationship between plaque compositions and long-term clinical outcomes in those patients.

SUBJECTS AND METHODS

The study subjects consisted of 339 consecutive patients (mean 61.7±12.2 years old, 239 males) who underwent coronary angiogram and a virtual histology-intravascular ultrasound examination. Major adverse cardiac and cerebrovascular events (MACCE), including all-cause death, non-fatal myocardial infarction, cerebrovascular events, and target vessel revascularization were evaluated during a mean 28-month follow-up period.

RESULTS

Patients with high fibrofatty volume (FFV, >8.90 mm(3), n=169) had a higher incidence of MACCE (25.4% vs. 14.7%, p=0.015), male sex (75.7% vs. 65.3%, p=0.043), acute coronary syndrome (53.3% vs. 35.9%, p=0.002), multivessel disease (62.7% vs. 41.8%, p<0.001) and post-stent slow flow (10.7% vs. 2.4%, p=0.002) than those with low FFV (FFV≤8.90 mm(3), n=170). Other plaque composition factors such as fibrous area/volume, dense calcified area/volume, and necrotic core area/volume did not show any impact on MACCE. Cardiogenic shock {hazard ratio (HR)=8.44; 95% confidence interval (CI)=3.00-23.79; p<0.001} and FFV (HR=1.85; 95% CI=1.12-3.07; p=0.016) were the independent predictors of MACCE by Cox regression analysis. Thin-cap fibroatheroma, necrotic core area, and necrotic core volume were not associated with MACCE.

CONCLUSION

FFV of a culprit lesion was associated with unfavorable long-term clinical outcomes in patients with CAOD.

Effect of calcification on the mechanical stability of plaque based on a three-dimensional carotid bifurcation model

Background

This study characterizes the distribution and components of plaque structure by presenting a three-dimensional blood-vessel modelling with the aim of determining mechanical properties due to the effect of lipid core and calcification within a plaque. Numerical simulation has been used to answer how cap thickness and calcium distribution in lipids influence the biomechanical stress on the plaque.

Method

Modelling atherosclerotic plaque based on structural analysis confirms the rationale for plaque mechanical examination and the feasibility of our simulation model. Meaningful validation of predictions from modelled atherosclerotic plaque model typically requires examination of bona fide atherosclerotic lesions. To analyze a more accurate plaque rupture, fluid-structure interaction is applied to three-dimensional blood-vessel carotid bifurcation modelling. A patient-specific pressure variation is applied onto the plaque to influence its vulnerability.

Results

Modelling of the human atherosclerotic artery with varying degrees of lipid core elasticity, fibrous cap thickness and calcification gap, which is defined as the distance between the fibrous cap and calcification agglomerate, form the basis of our rupture analysis. Finite element analysis shows that the calcification gap should be conservatively smaller than its threshold to maintain plaque stability. The results add new mechanistic insights and methodologically sound data to investigate plaque rupture mechanics.

Conclusion

Structural analysis using a three-dimensional calcified model represents a more realistic simulation of late-stage atherosclerotic plaque. We also demonstrate that increases of calcium content that is coupled with a decrease in lipid core volume can stabilize plaque structurally.

Left ventricular dysfunction with reduced functional cardiac reserve in diabetic and non-diabetic LDL-receptor deficient apolipoprotein B100-only mice

Background

Lack of suitable mouse models has hindered the studying of diabetic macrovascular complications. We examined the effects of type 2 diabetes on coronary artery disease and cardiac function in hypercholesterolemic low-density lipoprotein receptor-deficient apolipoprotein B100-only mice (LDLR^-/-ApoB^100/100).

Methods and results

18-month-old LDLR^-/-ApoB^100/100 (n = 12), diabetic LDLR^-/-ApoB^100/100 mice overexpressing insulin-like growth factor-II (IGF-II) in pancreatic beta cells (IGF-II/LDLR^-/-ApoB^100/100, n = 14) and age-matched C57Bl/6 mice (n = 15) were studied after three months of high-fat Western diet. Compared to LDLR^-/-ApoB^100/100 mice, diabetic IGF-II/LDLR^-/-ApoB^100/100 mice demonstrated more calcified atherosclerotic lesions in aorta. However, compensatory vascular enlargement was similar in both diabetic and non-diabetic mice with equal atherosclerosis (cross-sectional lesion area ~60%) and consequently the lumen area was preserved. In coronary arteries, both hypercholesterolemic models showed significant stenosis (~80%) despite positive remodeling. Echocardiography revealed severe left ventricular systolic dysfunction and anteroapical akinesia in both LDLR^-/-ApoB^100/100 and IGF-II/LDLR^-/-ApoB^100/100 mice. Myocardial scarring was not detected, cardiac reserve after dobutamine challenge was preserved and ultrasructural changes revealed ischemic yet viable myocardium, which together with coronary artery stenosis and slightly impaired myocardial perfusion suggest myocardial hibernation resulting from chronic hypoperfusion.

Conclusions

LDLR^-/-ApoB^100/100 mice develop significant coronary atherosclerosis, severe left ventricular dysfunction with preserved but diminished cardiac reserve and signs of chronic myocardial hibernation. However, the cardiac outcome is not worsened by type 2 diabetes, despite more advanced aortic atherosclerosis in diabetic animals.

Micro-ultrasound imaging assessment of carotid plaque characteristics in apolipoprotein-E knockout mice

This study was aimed to test the hypothesis that noninvasive assessment of carotid plaques can be achieved by high-resolution micro-ultrasound imaging in apolipoprotein-E knockout (apoE-KO) mice. Forty-two male apoE-KO mice were fed a high-fat diet and atherosclerotic lesions in the left common carotid artery were induced by perivascular placement of constrictive collars. Eight weeks after surgery, all mice were divided into interventional group (n=21) which received mental stress stimulation and intraperitoneal injection of lipopolysaccharide, and control group (n=21) which received only 0.9% sodium chloride solution for 4 weeks. Plaque morphology and flow velocities were evaluated by micro-ultrasonography. The results showed that micro-ultrasound imaging and corresponding cross-sectional histopathology data revealed positive correlations for plaque area, intima-medial thickness (IMT), eccentric index (EI) and remodeling index (RI) (all p<0.05). Ultrasound-derived IMT, EI and RI in the ruptured plaques were significantly greater than those in the nonruptured plaques (all p<0.05). Maximal flow velocity (Vmax) was higher in the ruptured plaque sites compared with nonruptured plaques sites (p<0.001). Multivariate logistic regression analysis revealed that IMT and Vmax were independent predictors of plaque rupture. In conclusion, micro-ultrasound imaging provides a reliable approach to the noninvasive and quantitative assessment of carotid plaques in apoE-KO mice.

Relationship Between Coronary Artery Remodeling and Plaque Composition in Culprit Lesions An Intravascular Ultrasound Radiofrequency Analysis

BACKGROUND

The relationship between coronary artery remodeling and culprit plaque composition in vivo has not been fully evaluated by spectral analysis of intravascular ultrasound (IVUS) radiofrequency (RF) data.

METHODS AND RESULTS

IVUS RF analyses were performed for 56 consecutive de novo culprit lesions of 52 patients undergoing percutaneous coronary intervention. Remodeling of culprit lesions was determined using the remodeling index (RI), calculated as the external elastic membrane area of the minimum lumen area (MLA) site divided by that of the proximal reference site. Positive remodeling was defined as RI >1.05, intermediate remodeling as 0.95< or = RI < or =1.05 and negative remodeling as RI <0.95. Among the 56 lesions, positive remodeling was detected in 24, intermediate remodeling in 16, and negative remodeling in 16. At MLA sites, positive remodeling lesions had a larger percentage of the fibrofatty component than negative remodeling lesions (22.5+/-10.3% vs 10.4+/-6.6%, p=0.0001), whereas the latter contained a larger percentage of the dense calcium component than the former (2.8+/-2.9% vs 8.4+/-7.0%, p=0.016).

CONCLUSIONS

Culprit plaques with positive remodeling have a large lipid burden, whereas those with negative remodeling contain a large amount of calcium.

Association of coronary plaque composition and arterial remodelling: a virtual histology analysis by intravascular ultrasound

BACKGROUND

Conflicting data have been reported about the correlation between plaque composition assessed by virtual histology (VH) and remodelling index (RI).

AIM

To evaluate, in a larger patient population, the relationship between plaque morphology obtained by VH and arterial remodelling.

METHODS AND RESULTS

VH intravascular ultrasound was performed on 95 non-bifurcation native significant lesions (>75% stenosis) in 85 patients. Positive remodelling (defined as RI > or =1.05) was present in 28 lesions, whereas intermediate/negative remodelling (RI <1.05) was present in 67 lesions. Compared with intermediate/negative remodelling, positive remodelling was associated with an increased frequency of patients with acute coronary syndrome (n = 13 (52%) vs n = 15 (25%); p = 0.017), and with a greater plaque burden (mean (SD) 78.3 (6.3)% vs 73.2 (6.8)%, p = 0.001). At the minimal lumen site, necrotic core was significantly smaller in lesions with positive remodelling (median (interquartile range) 5.0% (2.2-11.0%)) than in lesions with intermediate/negative remodelling (median (interquartile range) 9.0% (4.0-16.0%); p = 0.048). No differences were observed in the rate of thin-cap fibroatheroma or in the presence of multiple necrotic core layers, and there were no statistical differences for fibrous, fibro fatty and dense calcium percent plaque area at the minimum lumen diameter (MLD), or for the entire lesion length between both groups.

CONCLUSIONS

In vivo VH analysis shows that lesions with positive remodelling have statistically less necrotic core percent area at the MLD site compared with intermediate/negative remodelling lesions.

Negative Remodeling and Calcified Plaque in Octogenarians With Acute Myocardial Infarction

OBJECTIVES

The goal of this study was to use intravascular ultrasound (IVUS) to compare octogenarians versus patients <65 years of age with regard to culprit lesion morphology in acute myocardial infarction (MI).

BACKGROUND

Although octogenarians represent the fastest-growing segment of our population and have a higher risk profile, they are underrepresented in therapeutic trials.

METHODS

Between 2002 and 2005, 42 octogenarians and 52 patients <65 years of age underwent pre-intervention IVUS within 2 days from onset of an MI. Qualitative and quantitative measurements were performed at the lesion site and at the proximal and distal references. Positive remodeling was defined as a remodeling index (lesion/mean reference arterial area) > or =1.

RESULTS

Elderly patients mostly (71%) presented with non-ST-segment elevation myocardial infarction (NSTEMI), whereas patients <65 years of age presented almost equally with ST-segment elevation myocardial infarction (STEMI) and NSTEMI (56% vs. 44%). The frequency of rupture/dissection was greater in the <65-year-old group (32% vs. 9%, p = 0.009), and culprit lesions contained more thrombus in this group (14% vs. 2%, p = 0.04). Conversely, in octogenarians, lesions were predominantly calcified (57% vs. 10%, p < 0.001) and longer (20.9 +/- 7.8 mm vs. 16.6 +/- 6.1 mm, p = 0.004) with less positive remodeling (19% vs. 56%, p < 0.001). On multivariant logistic regression analysis, age was the only independent predictor of calcified plaque (p = 0.02) and remodeling (p = 0.005).

CONCLUSIONS

Negative remodeling and calcified plaque with rare plaque ruptured were common in elderly people with acute MI. These findings may contribute to the difference in clinical presentation and may suggest a different pathophysiologic mechanism of MI in octogenarians.

Coronary artery remodelling is related to plaque composition

OBJECTIVE

To assess the potential relation between plaque composition and vascular remodelling by using spectral analysis of intravascular ultrasound (IVUS) radiofrequency data.

METHODS AND RESULTS

41 coronary vessels with non-significant (< 50% diameter stenosis by angiography), < or = 20 mm, non-ostial lesions located in non-culprit vessels underwent IVUS interrogation. IVUS radiofrequency data obtained with a 30 MHz catheter, were analysed with IVUS virtual histology software. A remodelling index (RI) was calculated and divided into three groups. Lesions with RI > or = 1.05 were considered to have positive remodelling and lesions with RI < or = 0.95 were considered to have negative remodelling. Lesions with RI > or = 1.05 had a significantly larger lipid core than lesions with RI 0.96-1.04 and RI < or = 0.95 (22.1 (6.3) v 15.1 (7.6) v 6.6 (6.9), p < 0.0001). A positive correlation between lipid core and RI (r = 0.83, p < 0.0001) and an inverse correlation between fibrous tissue and RI (r = -0.45, p = 0.003) were also significant. All of the positively remodelled lesions were thin cap fibroatheroma or fibroatheromatous lesions, whereas negatively remodelled lesions had a more stable phenotype, with 64% having pathological intimal thickening, 29% being fibrocalcific lesions, and only 7% fibroatheromatous lesions (p < 0.0001).

CONCLUSIONS

In this study, in vivo plaque composition and morphology assessed by spectral analysis of IVUS radiofrequency data were related to coronary artery remodelling.

Calcification and cardiovascular problems in renal failure

Extraosseus calcification has plagued management of renal failure since the beginning of hemodialysis, but the issue has largely been neglected because the impact on survival was thought to be limited. The recent recognition that hyperphosphatemia is a strong predictor of all-cause mortality, and particularly of cardiac mortality, has transformed the situation. Relatively stringent, though difficult to implement, guidelines have been proposed for the management of hyperphosphatemia. Important recent insights document that, for different reasons, both high and low turnover of bone disease increase the risk of vascular calcifications. Vascular calcification impacts cardiac death not only by complicating coronary atherosclerosis, but also by increasing the stiffness of central arteries, impacting on heart function (increased impedance, reduced coronary perfusion). While in the past extraosseous calcification, including vascular calcification, was thought to be a passive process resulting from transgression of a critical Ca x P product, recent studies show that the adverse effect of hyperphosphatemia is also mediated by active processes (e.g., induction of "osteogenic" genetic programs), and is modulated by calcification inhibitors.

Remodeling of coronary arteries in diabetic patients-an intravascular ultrasound study

BACKGROUND

Coronary artery remodeling is a structural change in the vessel wall and typically in response to atherosclerotic plaque. The nature of coronary remodeling has been described in different clinical situations. However, remodeling characteristics of coronary arteries of diabetic patients have never been studied.

HYPOTHESIS

We tested the hypothesis that positive remodeling of coronary artery in response to atherosclerotic plaque in diabetic patients would be less compared to nondiabetic patients.

METHODS

Coronary intravascular ultrasound analysis of data in 26 consecutive patients (12 diabetic and 14 nondiabetic) was performed. Linear regression analyses of vessel area versus plaque area were carried out to establish a relation between the degree of plaque and the extent of remodeling in diabetic and nondiabetic groups.

RESULTS

The positive remodeling quantified as the slope of the regression line was similar in both the groups (diabetic group 1.32 and nondiabetic group 0.80) when all segments with different plaque areas were considered (P > 0.05). However, the diabetic group had greater positive remodeling in segments with plaque area less than 55%, as the slope for diabetic group was 2.01 and nondiabetic group was 1.40 (P < 0.05).

CONCLUSIONS

Both the diabetic and nondiabetic patients had positive remodeling in response to atherosclerotic plaque formation. Diabetics had greater positive remodeling in the early stages of atherosclerosis compared to nondiabetics, thus providing evidence against our hypothesis. The adverse clinical outcomes in diabetics may not be due to inadequate positive remodeling of coronary arteries as previously thought.

Spectrum of remodeling behavior observed with serial long-term (>/=12 months) follow-up intravascular ultrasound studies in left main coronary arteries

Most intravascular ultrasound (IVUS) studies of arterial remodeling in native coronary arteries reported a remodeling index obtained at a single time point. We analyzed serial IVUS examinations, including the vessel cross-sectional area changes (remodeling behavior), of 60 hemodynamically nonstenotic left main lesions (baseline vs 18.4 +/- 9.4 months follow-up). Lumen reduction resulted from vessel reduction (sometimes despite plaque + media decrease), plaque + media increase (with or without vessel increase), or both. The percent annual changes in lumen area correlated strongly with changes in vessel (r = 0.84), but not with changes in plaque + media area. Plaques were classified as group A lesions, reflecting positive remodeling behavior (vessel changes >0), or group B lesions, reflecting negative (or intermediate) remodeling behavior (vessel changes <==0). Both groups did not differ significantly in demographics, laboratory data, and medications. Group A lesions (n = 40) more often showed plaque + media increase than group B lesions (32 of 40 [80%] vs 9 of 20 [45%]; p = 0.02). Group A lesions had, on average, mild annual lumen increase despite mild plaque + media increase, i.e, overcompensation of remodeling for plaque + media increase (vessel increase greater than plaque + media area increase, 19 of 40 [47%]). Conversely, group B lesions (n = 20) showed a significant lumen area reduction (-2.8 +/- 2.6 mm(2)/year) as a result of a decrease in vessel area only. Thus, serial long-term reduction of lumen size may result from vessel shrinkage (sometimes despite plaque decrease), plaque increase (with or without vessel increase), or both; overall, only the remodeling behavior has a significant relation to lumen changes. More than 30% of lesions show a negative remodeling behavior, which shows no relation to patient characteristics or initial plaque burden.