Variations of remodeling in response to left main atherosclerosis assessed with intravascular ultrasound in vivo

Relationship between left main coronary artery plaque burden and nonleft main coronary atherosclerosis: results from the PROSPECT study

OBJECTIVES

Whether the severity of left main coronary artery (LMCA) disease reflects LMCA and overall coronary atherosclerotic burden is not known. We aimed to assess nonculprit LMCA disease characteristics and the relationship with atherosclerosis in the rest of the coronary arteries as well as patient outcomes.

PATIENTS AND METHODS

In the PROSPECT study, 697 patients with acute coronary syndromes underwent three-vessel gray-scale and radiofrequency intravascular ultrasound after percutaneous coronary intervention.

RESULTS

Overall, 552 patients with adequate LMCA imaging were compared according to LMCA plaque burden. The tertile with the highest plaque burden in the LMCA had the smallest LMCA minimum lumen area (17.4, 14.2, 10.5, lowest through highest tertiles, respectively, P<0.0001) and the greatest percent necrotic core volume (2.8, 5.6, 9.5%, lowest through highest tertiles, respectively, P<0.0001). Furthermore, the tertile with the highest plaque burden was also significantly associated with the highest overall non-LMCA percent atheroma volume within the major epicardial arteries (48.3, 49.2, 50.8%, lowest through highest tertiles, respectively, P<0.0001). After adjusting for patient background, the LMCA plaque burden was independently associated with non-LMCA percent atheroma volume (P=0.003). Of the three PROSPECT predictors of future nonculprit major adverse cardiac events (MACE) (minimum lumen area≤4 mm, plaque burden≥70%, and virtual histology thin-cap fibroatheroma), the tertile with the highest LMCA plaque burden had the highest number of patients with at least one of three PROSPECT predictors (P=0.03). In multivariable model, though total atheroma volume (per 1%) was an independent predictor of all MACE [hazard ratio (95% confidence interval)=1.06 (1.01-1.11), P=0.02] and strong trend for non-culprit-related MACE [hazard ratio (95% confidence interval)=1.06 (1.00-1.13), P=0.06], plaque burden at LMCA was not (all MACE, P=0.90, non-culprit-related MACE, P=0.85).

CONCLUSION

The severity of atherosclerosis in LMCA predicted the overall atherosclerotic plaque burden as well as the presence of high-risk plaques in the three major epicardial coronary arteries.

Assessment of superficial coronary vessel wall deformation and stress: validation of in silico models and human coronary arteries in vivo

Cyclic biomechanical stress at the lumen-intima interface plays a crucial role in the rupture of coronary plaque. We performed a comprehensive assessment of a novel angiography-based method for four-dimensional (4D) dynamic assessment of superficial wall stress (SWS) and deformation with a total of 32 analyses in virtual stenosis models with equal lumen dimensions and 16 analyses in human coronary arteries in vivo. The in silico model analyses demonstrated that the SWS, derived by the proposed global displacement method without knowledge of plaque components or blood pressure, was comparable with the result calculated by traditional finite element method. Cardiac contraction-induced vessel deformation increased SWS. Softer plaque and positive arterial remodeling, associated with a greater plaque burden, showed more variation in mean lumen diameter within the cardiac cycle and resulted in higher SWS. In vivo patient analyses confirmed the accuracy of computed superficial wall deformation. The centerlines predicted by our method at random selected time instant matched well with the actual one in angiograms by Procrustes analysis (scaling: 0.995 ± 0.018; dissimilarity: 0.007 ± 0.014). Over 50% of the maximum SWS occurred at proximal plaque shoulders. This novel 4D approach could be successfully to predict superficial wall deformation of coronary artery in vivo. The dynamic SWS might be more realistic to evaluate the risk of plaque rupture.

A Novel Algorithm to Quantify Coronary Remodeling Using Inferred Normal Dimensions

Background

Vascular remodeling, the dynamic dimensional change in face of stress, can assume different directions as well as magnitudes in atherosclerotic disease. Classical measurements rely on reference to segments at a distance, risking inappropriate comparison between dislike vessel portions.

Objective

to explore a new method for quantifying vessel remodeling, based on the comparison between a given target segment and its inferred normal dimensions.

Methods

Geometric parameters and plaque composition were determined in 67 patients using three-vessel intravascular ultrasound with virtual histology (IVUS-VH). Coronary vessel remodeling at cross-section (n = 27.639) and lesion (n = 618) levels was assessed using classical metrics and a novel analytic algorithm based on the fractional vessel remodeling index (FVRI), which quantifies the total change in arterial wall dimensions related to the estimated normal dimension of the vessel. A prediction model was built to estimate the normal dimension of the vessel for calculation of FVRI.

Results

According to the new algorithm, “Ectatic” remodeling pattern was least common, “Complete compensatory” remodeling was present in approximately half of the instances, and “Negative” and “Incomplete compensatory” remodeling types were detected in the remaining. Compared to a traditional diagnostic scheme, FVRI-based classification seemed to better discriminate plaque composition by IVUS-VH.

Conclusion

Quantitative assessment of coronary remodeling using target segment dimensions offers a promising approach to evaluate the vessel response to plaque growth/regression.

Coexistence of left main and right coronary artery ostial stenosis: demographic and angiographic features

This study was designed to evaluate ostial left main coronary artery (LMCA) stenosis and investigate concomitant stenotic lesions of LMCA and right coronary arteries (RCA) and their demographic and angiographic features. We evaluated 11,283 patients who underwent coronary angiography. Patients were placed into four groups according to having ostial or nonostial LMCA or RCA stenosis. Significant LMCA stenosis was observed in 242 (8.3%) of the patients, and only 68 (28.1%) of them had significant ostial LMCA stenosis. There was a significant correlation between ostial stenosis of LMCA and RCA (p = 0.03). The frequency of female gender was greater in ostial LMCA and ostial RCA stenosis groups compared with the other groups (p = 0.01). Ostial LMCA and RCA stenosis were related significantly. Both female predominance and coexistence of ostial LMCA and RCA stenosis might have suggest a different pathological ground for this disease.

Impact of plaque burden in the left main coronary artery determined by intravascular ultrasound on cardiovascular events in a Japanese population undergoing percutaneous coronary intervention

The left main coronary artery (LMCA) is a particularly important target of atherosclerotic plaque accumulation. The aim of this study was to investigate the connection between subclinical plaque burden in the LMCA measured by intravascular ultrasound and future cardiovascular events. Two hundred eighteen consecutive patients underwent percutaneous coronary intervention for the left anterior descending coronary artery or the left circumflex coronary artery under intravascular ultrasound guidance. Plaque burden in the LMCA was analyzed for these patients, and major adverse cardiac events were also evaluated. Data were analyzed by grouping the patients into tertiles according to plaque burden values; tertile 1, <32% area stenosis; tertile 2, 32% to 45% area stenosis; and tertile 3, >45% area stenosis. During a 3-year follow-up period (average 16.1 months), 12% of tertile 1, 18% of tertile 2, and 40% of tertile 3 experienced major adverse cardiac events, mostly due to repeat revascularization (p <0.001). On Cox multivariate analysis, plaque burden in the LMCA (per percentage) detected by intravascular ultrasound remained an independent significant predictor of major adverse cardiac events (hazard ratio 1.04, 95% confidence interval 1.02 to 1.07) and future revascularization (hazard ratio 1.05, 95% confidence interval 1.02 to 1.07) (p <0.001). In conclusion, plaque burden in the LMCA is useful as an indicator of coronary atherosclerosis and may be a significant predictor of cardiovascular events, especially revascularization.

Cardio-ankle vascular index could reflect plaque burden in the coronary artery

Cardio-ankle vascular index (CAVI) using the volume plethysmographic method is a noninvasive atherosclerotic indicator which is not influenced by blood pressure. Coronary intravascular ultrasound (IVUS) is a reliable technique to measure progression of atherosclerosis. The association between CAVI and IVUS has not been reported. The aim of this study was to evaluate the association between CAVI and the plaque burden measured by IVUS in the left main coronary artery (LMCA) in patients with coronary heart disease and normal LMCA. Cardio-ankle vascular index was significantly correlated with percentage plaque area (r = .649, P < .0001) measured by IVUS in the most diseased segment of LMCA. Cardio-ankle vascular index remained significant among cardiovascular disease risk factors included in the multiple regression analysis predicting percentage plaque area. Cardio-ankle vascular index was a good atherosclerotic indicator and associated with the plaque burden in nonculprit and angiographically normal LMCA.

Remodeling is a more important determinant of lumen size than atheroma burden in left main coronary artery disease

BACKGROUND

Left main coronary artery (LMCA) disease influences survival; however, the predictors of LMCA changes over time are incompletely understood.

METHODS

Paired intravascular ultrasound (IVUS) and core laboratory analyses were performed in a standardized fashion in 207 subjects (mean +/- SD age 58 +/- 10 years, 80% men). The average follow-up duration was 18 months (range 12-24 months). The IVUS measurements were first obtained at the smallest lumen area and the largest plaque area at follow-up and the corresponding positions in the LMCA were then measured at baseline.

RESULTS

The LMCA percentage of atheroma area at baseline was 38.2% +/- 11.8%, and 133 patients (64%) experienced an increase in percentage of atheroma area. Change in lumen area correlated positively with change in total vessel area (R = 0.85, P < .0001) and negatively with change in percentage of atheroma area (R = -0.58, P < .0001). Change in plaque area correlated well with change in total vessel area (R = 0.64, P < .0001) but only weakly with change in lumen area (r = 0.14, P = .039). Although LMCA length correlated negatively with baseline lumen area and total vessel area, it did not correlate with their changes over time. On multivariable analyses, current smoking predicted an increase in percentage of atheroma area (P = .0013) and plaque area (P = .0041). Height negatively predicted change in percentage of atheroma area (P = .001).

CONCLUSIONS

The LMCA lumen dimensions are more tightly linked with remodeling than with atheroma progression/regression.

Intravascular Ultrasound Classification of Plaque Distribution in Left Main Coronary Artery Bifurcations

Background— Angiographic classifications of the location and severity of disease in the main vessel and side branch of coronary artery bifurcations have been proposed and applied to distal left main coronary artery (LMCA) bifurcation.

Methods and Results— We reviewed 140 angiograms of distal LMCA and ostial left anterior descending (LAD) and left circumflex (LCX) artery lesions with preintervention intravascular ultrasound (IVUS) of both the LAD and LCX arteries as well as the LMCA. Of 140 patients, 92.9% had at least 1 cross section with ≥40% IVUS plaque burden versus 57.2% of patients with an angiographic diameter stenosis ≥50%. Contrary to angiographic classifications, IVUS showed that bifurcation disease was rarely focal and that both sides of the flow divider were always disease-free. Continuous plaque from the LMCA into the proximal LAD artery was seen in 90%, from the LMCA into the LCX artery in 66.4%, and from the LMCA into both the LAD and LCX arteries in 62%. Plaque localized to either the LAD or LCX ostium and not involving the distal LMCA was seen in only 9.3% of LAD arteries and 17.1% of LCX arteries. Plaque distribution was not influenced by the LAD/LCX angiographic angle, lesion severity, LMCA length, or remodeling. We proposed an IVUS classification for bifurcation lesions illustrating longitudinal and circumferential spatial plaque distribution.

Conclusions— Angiographic classification of LMCA bifurcation lesions is rarely accurate. IVUS shows that the carina is always spared and that the disease is diffuse rather than focal.

Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180466.

Thematic review series: Patient-Oriented Research. Imaging atherosclerosis: state of the art

The ability to image obstructive arterial disease brought about a revolution in clinical cardiovascular care; the development of newer technologies that image arterial wall thicknesses, areas, volumes, and composition allows valid imaging of atherosclerosis for the first time. Development of noninvasive imaging of atherosclerosis has further led to a quantum shift in research in the field by enabling the study of asymptomatic populations and thus allowing investigators to focus on preclinical disease without the many biases associated with the study of symptomatic patients. These noninvasive investigations have broad implications for clinical care as well. Coronary angiography, computed tomographic (CT) imaging of coronary calcium, intravascular ultrasound, multidetector CT angiography, B mode ultrasound of the carotid arteries, and MRI of the carotid arteries all have unique strengths and weaknesses for imaging atherosclerosis. Certain of these techniques are extremely useful as outcome variables for clinical trials, and others are uniquely useful as predictors of the risk of cardiovascular disease. All are informative in one way or another with regard to the role of plaque remodeling and composition in disease causation. CT and MRI technology are advancing very rapidly, and research and clinical uses of these imaging modalities promise to further advance our understanding of atherosclerosis and its prevention.

Remodeling Index Compared to Actual Vascular Remodeling in Atherosclerotic Left Main Coronary Arteries as Assessed With Long-Term (≥12 Months) Serial Intravascular Ultrasound

OBJECTIVES

We present the remodeling index (RI) versus serial intravascular ultrasound (IVUS) data.

BACKGROUND

The RI, derived by comparing lesion external elastic membrane (EEM) cross-sectional area versus the reference at one time point, is used in various IVUS studies as a substitute of true remodeling (change in EEM over time), assuming that it represents true remodeling.

METHODS

We studied 46 non-stenotic left main arteries using serial IVUS (follow-up 18 +/- 8 months). Plaques were divided into subgroups according to the follow-up RI: follow-up RI >1 (n = 27) versus follow-up RI < or =1 (n = 19).

RESULTS

Lesions with a follow-up RI >1 had an increase in lumen despite an increase in plaque because of an increase in EEM. Conversely, lesions with a follow-up RI < or =1 had a reduction in lumen as a result of both a plaque increase and EEM decrease. Overall, the follow-up RI correlated directly with changes in lesion site EEM (baseline-to-follow-up). Although there was no correlation between the follow-up RI and changes in reference EEM area, changes in reference EEM area did correlate directly with changes in lesion EEM area. In nearly 90% of lesions with a follow-up RI >1, there was a previously documented increase in EEM area. Using multivariate linear regression analysis, the follow-up RI was dependent on the baseline RI, the increase in lesion EEM area, and the decrease in reference EEM area. The follow-up RI was not dependent on changes in lesion plaque area.

CONCLUSIONS

The vast majority of left main lesions with a remodeling index >1 had evidence of a previous increase in lesion-site EEM area.

In vivovalidation of a novel semi-automated method for border detection in intravascular ultrasound images

The aim of this work was to evaluate a new semi-automated intravascular ultrasound (IVUS) border detection method. The method was used to identify the lumen and the external elastic membrane or the borders of stents in 80 IVUS images, randomly selected from 10 consecutive human coronary arteries. These semi-automated results were compared with observations of two experts. Several indices in each case were obtained in order fully to evaluate the method. The time required for identification of the borders was also recorded. The interobserver variability of the method ranged from 1.21% to 5.61%, the correlation coefficient from 0.98 to 0.99, the slope was close to unity (0.94-1.03), the y intercept close to zero and the Williams index value was close to unity (range 0.67-0.91). The time (mean+/-SD) required for the method to identify the borders of the different vessel layers for the whole IVUS sequence was 5.2+/-0.2 min. The results demonstrate that the method is reliable and capable of identifying rapidly and accurately the different vessel layers depicted in IVUS images.

Insulin sensitivity and coronary vasoreactivity: insulin sensitivity relates to adenosine-stimulated coronary flow response in human subjects

OBJECTIVE

Diabetes is associated with coronary microvasculature abnormalities and impaired coronary flow reserve (CFR). CFR is the ratio of coronary flow under maximal vasodilation to basal flow and is a measure for coronary vasoreactivity. Insulin resistance is the central defect in the development of type 2 diabetes, preceding its onset by 10-20 years. Thus, the relationship between insulin sensitivity and CFR in nondiabetic subjects is particularly interesting. The aim of the study was to investigate this relationship.

DESIGN

Cross-sectional study.

PATIENTS

The study population consisted of 18 nondiabetic subjects without coronary artery stenosis on coronary angiography. We excluded patients with structural heart disease or with conditions affecting CFR or insulin sensitivity such as low density lipoprotein (LDL)-cholesterol > or = 4.14 mmol/l, smoking, hypertension or obesity with a body mass index (BMI) > 28 kg/m(2).

MEASUREMENTS AND RESULTS

CFR was 3.1 +/- 0.8 (range 1.7-4.8), as assessed by intracoronary Doppler measurements in the left anterior descending coronary arteries after adenosine stimulation. Intravascular ultrasound revealed zero to moderate coronary atherosclerotic changes. Whole-body insulin sensitivity (M-value) was 7.5 +/- 2.9 mg/kg/min (range 2.2-12.6), as assessed by the hyperinsulinaemic-euglycaemic clamp test. Subjects with low CFR (< 3.0) had a significantly lower M-value than subjects with normal CFR (> 3.0) (6.0 +/- 2.5 vs. 9.0 +/- 2.5 mg/kg/min, P = 0.021). Univariate linear regression demonstrated a strong correlation between CFR and M-value (r = 0.76, P < 0.001). In multiple regression analysis, the significant association of CFR with M-value was independent of potential confounders (sex, age, BMI, LDL-cholesterol and plaque burden on intravascular ultrasound). Bootstrap analysis corroborated this finding.

CONCLUSIONS

Whole-body insulin sensitivity relates to coronary vasoreactivity. Across a wide range of both insulin sensitivity and coronary flow reserve from markedly abnormal to normal values, an increase in insulin sensitivity appears to be associated with an increase in coronary flow reserve. Insulin resistance is therefore associated with coronary microvasculature abnormalities in nondiabetics.

Low variation and high reproducibility in plaque volume with intravascular ultrasound

BACKGROUND

Intravascular ultrasound (IVUS) has several advantages compared to angiography when evaluating coronary atherosclerosis in the vessel wall.

METHODS

The accuracy, reproducibility, and short-time spontaneous variation in volume of vessel, plaque and lumen were studied by electrocardiographic-gated three-dimensional (3D) IVUS in 20 male patients with ischaemic heart disease (IHD).

RESULTS

The study lesions were angiographically insignificant, with a length of the analysed segment on 11.4+/-5.9 mm. At baseline the mean minimal lumen diameter was 2.41+/-0.59 mm, minimal lumen area 4.82+/-2.38 mm2, and maximal plaque burden 65.61+/-9.57%. Mean reference diameter was 3.1+/-0.6 mm. No significant changes were observed in volumes of total vessel, lumen or plaque. The coefficient of variation (CV) for two volume measurements at baseline was: vessel 0.8%, plaque 1.3%, and lumen 1.4%. For measurements recorded at baseline and after 12.6+/-1.5 weeks, CV was respectively 3.5%, 3.3% and 6.6%. Reproducibility and interobserver and intraobserver variation showed very high correlations. A linear correlation was present in percent changes over 12.6+/-1.5 weeks between vessel volume and lumen volume (r=0.804; p<0.001) and between percent changes in plaque volume and vessel volume (r=0.581; p=0.007). No correlation was found between changes in plaque volume and lumen volume (r=0.015; p=0.950).

CONCLUSION

ECG-gated 3D IVUS is a highly reproducible method when applied on coronary artery atherosclerosis. CV for lumen volume over 12.6+/-1.5 weeks is twice that of plaque volume indicating the superiority of the 3D IVUS compared to coronary angiography (CAG).

Relationship between cardiovascular risk as predicted by established risk scores versus plaque progression as measured by serial intravascular ultrasound in left main coronary arteries

BACKGROUND

Intravascular ultrasound (IVUS) is increasingly used as an end point in studies aimed at reducing progression or inducing regression of coronary artery disease. However, data linking serial changes by IVUS with clinical outcomes are scarce.

METHODS AND RESULTS

In the absence of a validated risk score for secondary prevention, we compared 3 established risk scores for primary prevention--PROCAM, SCORE, and Framingham--with plaque progression and lumen reduction as assessed with serial IVUS (follow-up, 18+/-9 months) in atherosclerotic left main coronary arteries of 56 patients with established atherosclerosis. For all 3 algorithms, patients at highest estimated risk of events showed greater plaque progression than patients at lowest risk (P<0.05 to <0.01). There were positive linear relationships between the risk of clinical events and plaque progression (r=0.41 to 0.60; P<0.002 to <0.0001). This translated into a greater decrease in lumen dimensions with increasing risk (P<0.05, PROCAM and SCORE). Risk prediction using the PROCAM algorithm showed the strongest relation with serial IVUS. During follow-up, 18 patients suffered from adverse cardiovascular events; these patients had an annual plaque progression that was significantly greater than other patients (25.2+/-19.4% versus 5.9+/-15.6%, P<0.001).

CONCLUSIONS

There was a positive linear relationship between the estimated risk of clinical events derived from all 3 established risk-score algorithms and the extent of plaque progression measured by serial IVUS. This translated into stenosis progression (reduction in lumen dimensions) with increasing clinical risk.

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.

Relation Between Progression and Regression of Atherosclerotic Left Main Coronary Artery Disease and Serum Cholesterol Levels as Assessed With Serial Long-Term (≥12 Months) Follow-Up Intravascular Ultrasound

Background— The relation between serum lipids and risk of coronary events has been established, but there are no data demonstrating directly the relation between serum low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol versus serial changes in coronary plaque dimensions.

Methods and Results— We performed standard analyses of serial intravascular ultrasound (IVUS) studies of 60 left main coronary arteries obtained 18.3±9.4 months apart to evaluate progression and regression of mild atherosclerotic plaques in relation to serum cholesterol levels. Overall, there was (1) a positive linear relation between LDL cholesterol and the annual changes in plaque plus media (P&M) cross-sectional area (CSA) ( r =0.41, P <0.0001) with (2) an LDL value of 75 mg/dL as the cutoff when regression analysis predicted on average no annual P&M CSA increase; (3) an inverse relation between HDL cholesterol and annual changes in P&M CSA ( r =−0.30, P <0.02); (4) an inverse relation between LDL cholesterol and annual changes in lumen CSA ( r =−0.32, P <0.01); and (5) no relation between LDL and HDL cholesterol and the annual changes in total arterial CSA (remodeling). Despite similar baseline IVUS characteristics, patients with an LDL cholesterol level ≥120 mg/dL showed more annual P&M CSA progression and lumen reduction than patients with lower LDL cholesterol.

Conclusions— There is a positive linear relation between LDL cholesterol and annual changes in plaque size, with an LDL value of 75 mg/dL predicting, on average, no plaque progression. HDL cholesterol shows an inverse relation with annual changes in plaque size.

Coronary arterial remodeling in differing clinical presentations of unstable angina pectoris--an intravascular ultrasound study

BACKGROUND

Coronary arterial remodeling influences the clinical presentation of ischemic heart disease; however, there is little information on the relationship between coronary arterial remodeling and the type of angina pectoris that patients manifest.

HYPOTHESIS

The study was undertaken to determine the difference of coronary arterial remodeling in patients with different types of angina pectoris.

METHODS

We analyzed 100 patients with ischemic heart disease using intravascular ultrasound (IVUS). Intracoronary IVUS images of proximal reference (PR), distal reference (DR), and target lesion were recorded, and intraluminal area (LA) and external elastic membrane (EEM) were measured. We defined a remodeling index as 100 x (lesion EEM - [PR-EEM + DR-EEM]/2) / ([PR-EEM + DR-EEM]/2). Cases were classified into three groups according to the clinical history (Group 1a: de novo unstable angina pectoris, Group 1b: accelerating unstable angina pectoris, and Group 2; stable angina pectoris).

RESULTS

The remodeling index in Group 1a was significantly larger than that in Groups 1b and 2 (18.6 +/- 28.5 vs. 5.3 +/- 27.1 and 18.6 +/- 28.5 vs. -2.7 +/- 17.6, p = 0.0347 and p = 0.0005, respectively), but there was no statistical difference in remodeling index between Groups 1b and 2.

CONCLUSIONS

Our results indicate that positive coronary arterial remodeling is more prevalent in patients with new onset of angina pectoris. The specific type of coronary arterial remodeling may affect the clinical presentation of patients with coronary artery disease.

Atheromas that cause fatal thrombosis are usually large and frequently accompanied by vessel enlargement

Several lines of clinical evidence show that AMI frequently occurs at sites with mild to moderate degree of coronary stenosis. The degree of luminal stenosis depends on plaque deposition and degree of vessel remodeling, features poorly assessed by coronary angiography. This postmortem study tested the hypothesis that the size of coronary atheroma and the type of remodeling distinguish culprit lesion responsible for fatal AMI from equi-stenotic nonculprit lesion in the same coronary tree. The main coronary branches from 36 consecutive patients with fatal AMI were studied. The culprit lesion (Group 1) and an equi-stenotic nonculprit segment (Group 2) obtained in measurements of another coronary branch from the same patient were compared. Morphometry and plaque composition was assessed in both groups. Compared to Group 2, Group 1 had larger areas of: plaque 9.6 vs. 4.7 mm(2), vessel 12.7 vs. 7.4 mm(2) and lumen 1.7 vs. 1.2 mm(2); (P< .01). Positive remodeling was more frequent in Group 1 than Group 2: 21/30 (70%) vs. 8/26 (31%). Plaque area correlated positively with lipid core and macrophages and negatively with fibrosis and smooth muscle cells. Atherosclerotic plaques that cause fatal thrombosis are more frequently positively remodeled and tend to be larger than nonculprit plaques with the same degree of cross-sectional stenosis. We tested whether arterial remodeling and plaque size vary between segments containing a fatal thrombosed plaque versus an equi-stenotic nonculprit plaque. Culprit vessel segments had higher cross-sectional areas of intimal plaque and of vessel wall than equi-stenotic nonculprit plaques. The cross-sectional area of the vessel correlated positively with both the lipid core area and CD68(+) macrophage content, and negatively with fibrosis area and smooth muscle cell content. These results add elements explaining limitations of angiography in identifying plaques and provide new insights into the role of remodeling in plaque instability.

Plaque distribution and vascular remodeling of ruptured and nonruptured coronary plaques in the same vessel: an intravascular ultrasound study in vivo

OBJECTIVES

This study was designed to identify potential differences between the intravascular ultrasound (IVUS) characteristics of spontaneously ruptured and nonruptured coronary plaques.

BACKGROUND

The identification of vulnerable plaques in vivo may allow targeted prevention of acute coronary events and more effective evaluation of novel therapeutic approaches.

METHODS

Intravascular ultrasound was used to identify 29 ruptured plaques in arteries containing another nonruptured plaque in an adjacent segment. Intravascular ultrasound characteristics of these plaques were compared with plaques of computer-matched controls without evidence of plaque rupture. Plaque distribution was assessed by measuring the eccentricity of lumen location (inside the total vessel). Lumen cross-sectional area narrowing was calculated as [1 - (target/reference lumen area)] x 100%. A remodeling index was calculated as lesion/reference arterial area (>1.05 = compensatory enlargement, <0.95 = shrinkage).

RESULTS

Among the three groups of plaques, there was no significant difference in quantitative angiographic parameters, IVUS reference dimensions and IVUS lumen cross-sectional area narrowing. There was a difference in plaque distribution; lumen location by IVUS was significantly more eccentric in ruptured than in nonruptured (p = 0.002) and control plaques (p < 0.0001). The arc of disease-free vessel wall was larger in ruptured than in control plaques (p < 0.0001). The remodeling pattern of ruptured and nonruptured plaques differed significantly from that of the control plaques (p = 0.0001 and 0.003); compensatory enlargement was found in 66%, 48%, and 17%, whereas shrinkage was found in 7%, 10% and 48%, respectively.

CONCLUSIONS

Intravascular ultrasound assessment of plaque distribution and vascular remodeling may help to classify plaques with the highest probability of spontaneous rupture.

What has intravascular ultrasound taught us about plaque biology?

Intravascular ultrasound (IVUS) has a defined role in the cardiac catheterization laboratory to assess lesion severity and the procedural success of vascular interventions. However, IVUS has also contributed to our understanding of the biology of atherosclerosis and restenosis. In acute coronary syndromes, IVUS has revealed varying degrees of stenosis, thrombosis, and plaque derangement typical of the plaque disruption seen in many pathologic studies of patients who have died of this condition. IVUS has demonstrated that the culprit lesions of patients surviving acute coronary syndromes also tend to be softer, with less calcium, and tend to have more plaque with positive arterial remodeling (compensatory enlargement) than lesions causing stable coronary syndromes. Arterial remodeling is also an important component of restenosis after coronary interventions. IVUS has suggested that interventions that reduce restenosis tend to have a greater impact on preventing negative remodeling (constriction) rather than reducing neointimal proliferation. Oxidant stress may be an important contributor to negative remodeling, as IVUS has demonstrated this anatomy at sites of coronary artery spasm. Positive remodeling seen by IVUS is also associated with impaired endothelial vasomotor dysfunction, and IVUS studies have demonstrated the contribution of vasomotor tone to arterial elasticity. Future directions include integrating IVUS with other imaging modalities, such as angiography, to study the interaction of anatomic and physiologic factors in atherosclerosis progression, and using the raw ultrasound signal to distinguish plaque components and differences in wall strain that may identify vulnerable plaques.

Vascular remodeling in atherosclerotic coronary arteries is affected by plaque composition

BACKGROUND

Narrowing of lumen in atherosclerotic lesions is determined not solely by accumulation of plaque but also by constrictive or expansive vascular remodeling. Underlying mechanisms and determinants of these bidirectional processes are not known.

OBJECTIVES

To elucidate the response of vascular remodeling to progressive atherosclerosis by analyzing its potential association with composition of plaque.

METHODS

Seventy patients with 77 de-novo coronary artery lesions underwent intravascular ultrasound imaging before coronary intervention. Target lesions were defined as soft, fibrous/mixed, and calcified plaques. Quantitative measurements of area of lumen (A(L)), total area of vessel (A(TV)) and area of plaque (A(P) = A(TV)-A(L)) were performed at the lesion site and at the proximal and distal reference sites. Remodeling was determined by using a remodeling index [I(R) = (stenosis of A(TV)/mean reference A(TV)) x 100].

RESULTS

Overall vascular remodeling was balanced with a mean remodeling index of 100.2+/-19.3% and a high interlesion range (60.2-152.4%). The remodeling index for soft lesions was significantly higher than those for fibrous/mixed and calcified lesions (110+/-18.8 versus 96.2+/-14.4 and 85.9+/-15.1%, P < 0.01). Calcified lesions exhibited lower remodeling indexes than did uncalcified lesions (85.9+/-15.1 versus 104.6+/-18.4%, P < 0.01).

CONCLUSIONS

Processes involved in vascular remodeling are affected by composition of plaque insofar as there is a higher prevalence of constrictive remodeling among calcified plaques and a higher prevalence of expansive remodeling among soft lesions. These findings indicate that constrictive remodeling is a late manifestation in atherogenesis. Future studies are warranted in order to enhance the understanding of progression of atherosclerosis, and of mechanisms of vascular remodeling and their impacts on interventional therapy.

Size of emptied plaque cavity following spontaneous rupture is related to coronary dimensions, not to the degree of lumen narrowing. A study with intravascular ultrasound in vivo

OBJECTIVE

To identify any potential relations between the size of an emptied plaque cavity and the remodelling pattern, plaque or vessel dimensions, lumen narrowing, and other ultrasonic lesion characteristics.

DESIGN

Intravascular ultrasound was used to examine prospectively 51 ruptured ulcerated coronary plaques. Cross sectional area measurements comprised lumen, vessel, plaque, and emptied plaque cavity. Lumen narrowing was calculated as 1 - (lesion lumen area/reference lumen area) x 100%. A remodelling index was calculated as lesion vessel area/reference vessel area, and plaques were divided into those with values > 1.05 (group A) and </= 1.05 (group B).

RESULTS

Of the total of 51 plaques, 36 (71%) were assigned to group A and 15 (29%) to group B. In neither group was there a significant difference in reference dimensions and lumen narrowing. However, lesion vessel (mean (SD): 22.6 (8.1) mm(2) v 17. 5 (4.3) mm(2); p = 0.006) and plaque areas (15.8 (6.2) mm(2) v 12.8 (3.2) mm(2); p = 0.03) were greater in group A than in group B. The cavity inside the plaque was larger in group A than in group B (2.8 (1.6) mm(2) v 1.8 (0.9) mm(2); p = 0.007) and showed a positive linear relation with lesion and reference vessel size (r = 0.58 and 0.56, respectively; p < 0.001), but not with lumen narrowing.

CONCLUSIONS

The size of the emptied cavity inside ruptured plaques is on average larger in lesions with adaptive vascular remodelling, and shows a linear relation with lesion plaque and vessel size and with the reference dimensions, but not with the degree of lumen narrowing.

Plasminogen is a critical determinant of vascular remodeling in mice

Extracellular proteolysis is likely to be a feature of vascular remodeling associated with atherosclerotic and restenotic arteries. To investigate the role of plasminogen-mediated proteolysis in remodeling, polyethylene cuffs were placed around the femoral arteries of mice with single and combined deficiencies in plasminogen and fibrinogen. Neointimal development occurred in all mice and was unaffected by genotype. Significant compensatory medial remodeling occurred in the cuffed arteries of control mice but not in plasminogen-deficient mice. Furthermore, focal areas of medial atrophy were frequently observed in plasminogen-deficient mice but not in control animals. A simultaneous deficit of fibrinogen restored the potential of the arteries of plasminogen-deficient mice to enlarge in association with neointimal development but did not eliminate the focal medial atrophy. An intense inflammatory infiltrate occurred in the adventitia of cuffed arteries, which was associated with enhanced matrix deposition. Adventitial collagen deposition was apparent after 28 days in control and fibrinogen-deficient arteries but not in plasminogen-deficient arteries, which contained persistent fibrin. These studies demonstrate that plasmin(ogen) contributes to favorable arterial remodeling and adventitial collagen deposition via a mechanism that is related to fibrinogen, presumably fibrinolysis. In addition, these studies reveal a fibrin-independent role of plasminogen in preventing medial atrophy in challenged vessels.

Preintervention lesion remodelling affects operative mechanisms of balloon optimised directional coronary atherectomy procedures: a volumetric study with three dimensional intravascular ultrasound

AIMS

To classify atherosclerotic coronary lesions on the basis of adequate or inadequate compensatory vascular enlargement, and to examine changes in lumen, plaque, and vessel volumes during balloon optimised directional coronary atherectomy procedures in relation to the state of adaptive remodelling before the intervention.

DESIGN

29 lesion segments in 29 patients were examined with intravascular ultrasound before and after successful balloon optimised directional coronary atherectomy procedures, and a validated volumetric intravascular ultrasound analysis was performed off-line to assess the atherosclerotic lesion remodelling and changes in plaque and vessel volumes that occurred during the intervention. Based on the intravascular ultrasound data, lesions were classified according to whether there was inadequate (group I) or adequate (group II) compensatory enlargement.

RESULTS

There was no significant difference in patient and lesion characteristics between groups I and II (n = 10 and 19), including lesion length and details of the intervention. Quantitative coronary angiographic data were similar for both groups. However, plaque and vessel volumes were significantly smaller in group I than in II. In group I, 9 (4)% (mean (SD)) of the plaque volume was ablated, while in group II 16 (11)% was ablated (p = 0.01). This difference was reflected in a lower lumen volume gain in group I than in group II (46 (18) mm(3) v 80 (49) mm(3) (p < 0.02)).

CONCLUSIONS

Preintervention lesion remodelling has an impact on the operative mechanisms of balloon optimised directional coronary atherectomy procedures. Plaque ablation was found to be particularly low in lesions with inadequate compensatory vascular enlargement.

Arterial remodelling of native human coronary arteries in patients with unstable angina pectoris: a prospective intravascular ultrasound study

OBJECTIVE

To investigate the use of intravascular ultrasound (IVUS) in detecting the presence of arterial remodelling in patients with unstable angina.

DESIGN

Prospective case study.

PATIENTS

60 of 95 consecutively admitted patients with unstable angina (41 male, 19 female), mean (SD) age 61.2 (8.1) years.

INTERVENTIONS

Qualitative and quantitative coronary angiography and IVUS.

MAIN OUTCOME MEASURES

Adaptive or constrictive remodelling (AR, CR) was considered present when the cross sectional area of the external elastic membrane at the lesion site was larger than the proximal cross sectional area or smaller than the distal cross sectional area, respectively.

RESULTS

22 of the 60 patients (37%) showed AR and 14 (23%) showed CR. No remodelling was seen in 24 patients (group NR). The plaque contained more thrombus and plaque rupture in group AR than in groups CR and NR (thrombus: 91% v 50% and 67%, respectively, p = 0.023; rupture: 73% v 29% and 42%, p = 0.020). AR was associated with a larger plaque cross sectional area (12.6 (SD 4.6) mm2 v 10.8 (6.3) and 9.2 (3.7) mm2, p = 0.001) and larger external elastic membrane cross sectional area (16.5 (5.8) mm2 v 13.2 (5.2) and 14.4 (3.6) mm2, p = 0.01 in group AR v groups CR and NR, respectively), while the plaque burden was larger in groups AR (74.9 (9.1)%) and CR (72.4 (16.6)%) than in group NR (66.2 (18.1)%, p = 0.005).

CONCLUSIONS

IVUS is capable of detecting adaptive and constrictive remodelling of target lesions and its relation to plaque morphology in unstable angina.

Preintervention arterial remodeling as an independent predictor of target-lesion revascularization after nonstent coronary intervention: an analysis of 777 lesions with intravascular ultrasound imaging

BACKGROUND

Pathological and intravascular ultrasound (IVUS) studies have documented arterial remodeling during atherogenesis. However, the impact of this remodeling process on the long-term outcome after percutaneous intervention is unknown.

METHODS AND RESULTS

We used preintervention IVUS to define positive and negative/intermediate remodeling in a total of 777 lesions in 715 patients treated with nonstent techniques. Positive remodeling (lesion external elastic membrane area greater than average reference) was present in 313 lesions; intermediate/negative remodeling (lesion external elastic membrane area less than or equal to reference) was present in the other 464. Baseline clinical and angiographic characteristics were similar, except for a slightly higher percentage of insulin-dependent diabetic patients (10.2% versus 6.1%; P=0.054) in the negative/intermediate-remodeling group. Angiographic success and in-hospital and short-term complications were comparable in the 2 groups. There was no significant correlation between remodeling (as a continuous variable) and final lumen area (r=0.06) or final lesion plaque burden (r=0.17). At 18+/-13 months of clinical follow-up, both groups had similar rates of death and Q-wave myocardial infarction: 3.4% and 2.5% for the negative/intermediate-remodeling group versus 2.7% and 2.7% for the positive-remodeling group. However, the target-lesion revascularization (TLR) rate was 20.2% for the negative/intermediate-remodeling group versus 31.2% for the positive-remodeling group (P=0.007), and remodeling, as a continuous variable, was strongly correlated with probability of TLR (P=0.0001). By multivariable logistic regression analysis, diabetes (OR=2.3), left anterior descending artery location (OR=1.8), and remodeling (OR=5.9) were independent predictors of TLR.

CONCLUSIONS

Positive lesion-site remodeling is associated with a higher long-term TLR after a nonstent interventional procedure. Thus, long-term clinical outcome appears to be determined in part by preintervention lesion characteristics.