In vivo validation of compensatory enlargement of atherosclerotic coronary arteries

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.

Impact of diabetes mellitus on angiographically silent coronary atherosclerosis

Constrictive remodeling occurs in significant atherosclerotic lesions of the diabetic patient, but the impact of diabetes mellitus (DM) on the angiographically normal coronary artery is still unclear. Morphometric analysis using intravascular ultrasound (IVUS) prior to intervention evaluated 54 sites in 33 DM patients and 106 in 62 non-diabetic patients. Vessel area (VA) and lumen area (LA) were measured at angiographically normal sites in the vessel. Plaque area (PA) was calculated as VA - LA. Percentage plaque area (%PA) was calculated as PA VA. Even in the angiographically normal site, mild coronary atherosclerosis was detected by IVUS in both groups. In the patients with DM, VA and LA were significantly smaller than in the non-diabetic patient (15.5 vs 17.8 mm(2), p<0.01; and 10.1 vs 12.2 mm(2), p<0.01 respectively), whereas % PA was similar (34.5 vs 31.6%). At angiographically normal sites where mild coronary atherosclerosis is detected by IVUS, the coronary artery of diabetic patients is smaller than that of the non-diabetic. These results suggest impaired compensatory enlargement or some other constrictive mechanism has already occurred in the early stages of coronary atherosclerosis in patients with DM.

Intravascular ultrasound observations of atherosclerotic lesion formation and restenosis in patients with diabetes mellitus

Coronary artery disease is more aggressive in diabetic patients than in nondiabetics; they have more diffuse disease, higher mortality rates and worse clinical outcomes after coronary interventions. Intravascular ultrasound (IVUS) produces transmural tomographic images of the coronary arteries in vivo. Recent IVUS studies have provided new insights into the mechanisms of stenosis formation and restenosis in both nondiabetic and diabetic patients. Arterial remodeling is defined as a change in arterial area. During atherogenesis, an increase in arterial area usually accompanies plaque accumulation to delay lumen compromise. Stenosis formation is related to: (a) the rate of plaque accumulation versus the rate of positive remodeling; and (b) the limits and ultimate failure of positive remodeling. However, there is a marked variability in remodeling. IVUS studies have suggested that remodeling may be impaired in some diabetic patients during atherogenesis. Following non-stent catheter-based interventions, serial (post-intervention and follow-up) IVUS studies have shown that the change in lumen area correlates better with the change in arterial area (remodeling) than with the change in plaque area (neointimal hyperplasia). In some patients, a positive remodeling response mitigates against the increase in plaque area to limit late lumen loss and restenosis. Neointimal hyperplasia is exaggerated in diabetic patients. Despite this, there is a reduced frequency of positive remodeling, potentially similar to the impaired positive remodeling in some diabetic patients during atherogenesis. Failed or inadequate arterial remodeling may contribute to the pathogenesis and natural history of atherosclerotic coronary artery disease in diabetic patients.

Radical-trapping activity, blood pressure, and carotid enlargement in women

The aim of this study was to evaluate the influence of traditional and nontraditional (oxidation markers) cardiovascular risk factors on the degree of adaptive response of the carotid wall to atherosclerotic disease, a process known as arterial enlargement. Five thousand sixty-two clinically healthy, middle-aged women living in the area of Naples participated in the "Progetto Atena" study; 310 of these women (potentially at higher atherosclerotic risk) underwent a high-resolution ultrasound scan of the carotid arteries. In addition to routine biochemical tests, these women had the determination of serum IgG antibody titer against oxidized LDL and measurement of thiobarbituric acid reactive substances and total radical-trapping activity potential of plasma. Age, systolic blood pressure, body mass index, and radical-trapping activity were all positively correlated with external and internal common carotid diameters, whereas triglycerides (positively) and HDL cholesterol (inversely) were related only to external diameter. After controlling for traditional cardiovascular risk factors, associations still persisted for age, systolic blood pressure, and plasma radical-trapping activity with external carotid diameters. However, in the quartile of women with highest total cholesterol (>7.38 mmol/L), the slope of the regression line between systolic blood pressure and external diameter was significantly flatter than in the three other quartiles (test for difference, P=0.014). Outward carotid enlargement is related to traditional and nontraditional risk factors and comes even before plaque development. Women with poor resistance to oxidative stress potentially have a difficulty to remodel their arteries in response to atherosclerotic stimuli.

Intracoronary ultrasound in acute coronary syndromes: from characterization of vulnerable plaques to guidance of percutaneous treatment of complex stenoses

Our current knowledge on the substrate and genesis of acute coronary syndromes (ACS) results from the integration of pathological, angiographic, and intracoronary imaging techniques. To summarize briefly the current paradigm, eight differentiated stages of development of atherosclerotic lesions are currently accepted, defined not only by the cellular elements involved, but also by the appearance of sudden alterations of plaque structure and coronary thrombosis. The latter constitutes not only the dominant substrate for the most devastating manifestations of coronary artery disease, but also accelerates plaque size at a faster pace than in earlier stages. The composition of atherosclerotic plaque varies significantly along the different evolutive stages, and thus includes cellular (macrophage, smooth muscle cells) and noncellular elements (glicosaminglycan or collagen-rich cellular matrix, extracellular lipid deposits, calcification, fresh, or organized thrombus) in a varying proportion. Furthermore, a dynamic process of vessel remodeling occurs along the atherosclerotic process, resulting, in most cases, in a protective mechanism against myocardial ischemia by preserving luminal dimensions during plaque enlargement. Intravascular ultrasound (IVUS) is one of the intracoronary imaging techniques that has contributed to the understanding of these changes in man. In addition, IVUS has the potential of being a useful clinical tool for predicting the chances of future acute coronary events by identifying vulnerable plaques, of characterizing which is the culprit lesion in ACS, and in guiding revascularization procedures in the treacherous field of thrombotic coronary syndromes. In this article, we review the current evidence on the potential of IVUS imaging for fulfilling these purposes.

Mechanism of lumen gain during coronary stent deployment in diabetic patients compared with non-diabetic patients

BACKGROUND

Diabetic patients show an increased incidence of restenosis after coronary angioplasty than non-diabetic patients. This may be because of differences in the mechanism of lumen gain during coronary revascularization in this population cohort.

DESIGN

This study analyses the mechanism of lumen gain during coronary stent deployment in diabetic patients compared with non-diabetic patients with intravascular ultrasound (IVUS).

METHODS

IVUS images were obtained prior to and after revascularization in 26 diabetic and 97 non-diabetic patients. The external elastic membrane cross-sectional area (EEM) and lumen cross-sectional area (LA) were measured. Plaque area (PA) was calculated as EEM minus LA. Differences between pre- and post-LA (deltaLA), EEM (deltaEEM) and PA (deltaPA) were calculated.

RESULTS

Pre-interventional PA (diabetic patients: 12.4 +/- 4.4 mm2 compared with non-diabetic patients: 10.7 +/- 3.6 mm2, = 0.04) and pre-interventional EEM (15.5 +/- 4.4 mm2 compared with 13.6 +/- 3.7 mm2 respectively, P = 0.02) were larger in the diabetic group. Postinterventional PA (10.2 +/- 3.2 mm2 compared with 8.0 +/- 3.4 mm2, P = 0.004) was also larger and postinterventional LA (6.3 +/- 2.2 mm2 compared with 7.4 +/- 2.4 mm2 = 0.04), deltaEEM (0.9 +/- 1.8 mm2 compared with 1.8 +/- 1.8 mm2 P = 0.04) and deltaLA (3.1 +/- 1.6 mm2 compared with 4.2 +/- 2.2 mm2, P = 0.03) were smaller in the diabetic group. The diabetic group exhibited longer lesion lengths (P = 0.04) and a higher inflation pressure was used during revascularization in this patient cohort (P = 0.02).

CONCLUSION

Diabetic patients have less reduction of PA during revascularization and because the vessel wall cannot be stretched outwards despite higher inflation pressure, postinterventional LA remains smaller than in the non-diabetic population cohort. This might be a rudiment for consideration of different treatment strategies such as cutting balloon or atherectomy prior to stenting in this population group in order to achieve better procedural outcome.

Three-dimensional black-blood cardiac magnetic resonance coronary vessel wall imaging detects positive arterial remodeling in patients with nonsignificant coronary artery disease

BACKGROUND

Direct noninvasive visualization of the coronary vessel wall may enhance risk stratification by quantifying subclinical coronary atherosclerotic plaque burden. We sought to evaluate high-resolution black-blood 3D cardiovascular magnetic resonance (CMR) imaging for in vivo visualization of the proximal coronary artery vessel wall.

METHODS AND RESULTS

Twelve adult subjects, including 6 clinically healthy subjects and 6 patients with nonsignificant coronary artery disease (10% to 50% x-ray angiographic diameter reduction) were studied with the use of a commercial 1.5 Tesla CMR scanner. Free-breathing 3D coronary vessel wall imaging was performed along the major axis of the right coronary artery with isotropic spatial resolution (1.0x1.0x1.0 mm(3)) with the use of a black-blood spiral image acquisition. The proximal vessel wall thickness and luminal diameter were objectively determined with an automated edge detection tool. The 3D CMR vessel wall scans allowed for visualization of the contiguous proximal right coronary artery in all subjects. Both mean vessel wall thickness (1.7+/-0.3 versus 1.0+/-0.2 mm) and wall area (25.4+/-6.9 versus 11.5+/-5.2 mm(2)) were significantly increased in the patients compared with the healthy subjects (both P<0.01). The lumen diameter (3.6+/-0.7 versus 3.4+/-0.5 mm, P=0.47) and lumen area (8.9+/-3.4 versus 7.9+/-3.5 mm(2), P=0.47) were similar in both groups.

CONCLUSIONS

Free-breathing 3D black-blood coronary CMR with isotropic resolution identified an increased coronary vessel wall thickness with preservation of lumen size in patients with nonsignificant coronary artery disease, consistent with a "Glagov-type" outward arterial remodeling. This novel approach has the potential to quantify subclinical disease.

Vascular remodeling of the carotid artery in patients with untreated essential hypertension increases with age

We examined whether hypertrophy of the carotid artery in patients with untreated essential hypertension is associated with compensatory carotid artery enlargement as these patients age. Carotid ultrasonography was evaluated in 163 patients with untreated essential hypertension (74 males and 89 females) and in 76 normotensive subjects. Intima-media end-diastolic thickness (IMT) and outer vessel diameter (VD) were measured, and relative wall thickness (IMT/R, R=VD/2) and vascular mass (VM) were calculated. Determinants of vascular hypertrophy in patients with untreated essential hypertension were also investigated. VD, VM, and IMT were significantly correlated with age in both the normotensive and hypertensive groups. Additionally, IMT was significantly correlated with VD in both groups. There was no correlation between increasing age and IMT/R in either group. IMT, VD and VM were significantly higher in the hypertensive group >50 years than in age-matched normotensive controls. However, IMT/R was significantly higher in the 50-59 years hypertensive group than in normotensive controls of the same age group. In addition to age, VM was related to systolic blood pressure, pulse pressure, fasting blood sugar, IMT, VD, and IMT/R in the hypertensive group. Multivariate regression analysis in the hypertensive group indicated that IMT/R was the strongest predictor of carotid vascular mass. Age and pulse pressure were also independently related to vascular mass. These results indicate that, as patients with untreated hypertension age, carotid arteries undergo remodeling. This should add further impetus to the implementation of appropriate hypertension treatment for such patients.

Application of intravascular ultrasound to characterize coronary artery disease and assess the progression or regression of atherosclerosis

Angiography has major limitations in its ability to assess coronary disease. Intravascular ultrasound (IVUS) offers unique capabilities to assess coronary atherosclerotic burden. The tomographic orientation of ultrasound enables visualization of the full vessel wall, as opposed to the 2-dimensional projection of the lumen provided by angiography. The equipment required to perform coronary IVUS consists of a catheter with a miniaturized transducer and a console to reconstruct the image. High ultrasound frequencies are used, typically, 30 to 40 MHz, which provides excellent theoretical resolution. IVUS has been performed safely in a wide variety of clinical situations. Vessels with classic atherosclerosis exhibit a diversity of abnormal features that reflect the severity, composition, and distribution of the atheromata. Plaque rupture is sometimes evident in ultrasound examination of the culprit lesions after an acute coronary syndrome. Most laboratories routinely perform cross-sectional area measurements of the lumen and external elastic membrane boundaries and calculate atheroma area. IVUS commonly detects atherosclerosis at angiographically normal sites. It has contributed substantially to our understanding of remodeling and has shown that positive remodeling is more prevalent in unstable lesions. Studies in patients early after transplantation have shown the presence of advanced atherosclerosis in their apparently normal donors. In addition, the application of IVUS in detecting the rate of progression or regression of existing atherosclerosis is among the most dynamic areas of development. IVUS is likely to emerge as the "gold standard" in the study of atherosclerosis progression-regression over the next few years.

Coronary intravascular ultrasound: implications for understanding the development and potential regression of atherosclerosis

The incremental value of intravascular ultrasound (IVUS), compared with angiographic analysis of coronary atherosclerosis, originates principally from 2 key features-its tomographic perspective and the ability to image coronary atheroma directly. Whereas angiography depicts the cross-sectional coronary anatomy as a planar silhouette of the lumen, ultrasound directly images the atheroma within the vessel wall, allowing measurement of atheroma size, distribution, and to some extent, composition. Although angiography remains the principal method to assess the extent of coronary atherosclerosis and to guide percutaneous coronary interventions, IVUS is rapidly altering conventional paradigms in the diagnosis and therapy of coronary artery disease. Thus, IVUS has become a vital adjunctive imaging modality for the aggressive coronary interventional cardiologist. As such, ultrasound has earned a role as a viable complementary technique relative to angiography, rather than an alternative to conventional angiographic methods. This article reviews the rationale, technical advantages and limitations, and interpretation of intravascular ultrasonography from the perspective of the general and invasive cardiologist. We emphasize the impact that IVUS studies have had on our understanding of the atherosclerotic coronary artery disease process, because these findings have important implications for all cardiologists. We then review several trials that are currently using intravascular ultrasonography for the study of coronary artery disease regression.

Increased intimal apoptosis in coronary atherosclerotic vessel segments lacking compensatory enlargement

OBJECTIVES

In a histopathologic study, we assessed the balance of cell proliferation and apoptosis by counting the number of apoptotic and proliferating cell nuclear antigen-positive cells in freshly harvested atherectomy specimens from 34 patients.

BACKGROUND

Remodeling of human coronary arteries is an adaptive process that alters vascular lumen size.

METHODS

Intravascular ultrasound was performed prior to atherectomy. Total vessel area (area within the external elastic lamina [EEL]), lumen area and plaque area were measured at the region of interest (ROI), and at a proximal and distal reference segment, utilizing the formula Delta(%)=100x(ROI-reference segment)/reference segment. Positive arterial remodeling (R+) resulting in luminal expansion was defined as DeltaEEL >10%. Absence of remodeling (0 < DeltaEEL <10%) and constrictive arterial remodeling (DeltaEEL <0) were considered as neutral remodeling (R0) and negative remodeling (R-), respectively.

RESULTS

In R- lesions, apoptotic indices (APO) were significantly elevated (17.17 +/- 2.19%) compared with R+ lesions (4.89 +/- 1.7%; p = 0.0007). In a rabbit iliac percutaneous transluminal coronary angioplasty model intimal apoptosis was increased four weeks after balloon angioplasty injury (APO 8.8 +/- 0.03%) compared with contralateral untreated segments (APO 3.0 +/- 0.04%, n = 6). Lesions with an EEL/intimal area <3.0 showed significantly more intimal apoptosis than untreated lesions (p = 0.02).

CONCLUSIONS

The data indicate that constrictive remodeling of atherosclerotic coronary lesions is associated with increased apoptosis of intimal cells. We speculate that increased apoptosis is due to extensive plaque healing after episodes of symptomatic or asymptomatic plaque rupture.

Misperception of adaptation and remodeling in vascular pathology

A prerequisite of scientific communications is that words should not be misrepresented. Currently, the frequent misuse of adaptation and remodeling derives from faulty analysis and misrepresentation of the pathology of coronary atherosclerotic lesions. This misperception of vascular pathology has misled the uncritical and unwary, and propagates fallacious data and concepts. Unless the misusage ceases, the terms will continue to be meaningless merely furthering promulgation of unscientific data and concepts that effectively obstructs scientific progress.

An intravascular ultrasound classification of angiographic coronary artery aneurysms

The purpose of this study was to use intravascular ultrasound (IVUS) to clarify the morphology of coronary aneurysms diagnosed by angiography. Seventy-seven consecutive patients with an aneurysmal dilatation in a native coronary artery diagnosed by angiography (defined as a lesion lumen diameter 25% larger than reference) were evaluated by IVUS. IVUS true aneurysms were defined as having an intact vessel wall and a maximum lumen area 50% larger than proximal reference. IVUS pseudoaneurysms had a loss of vessel wall integrity and damage to adventitia or perivascular tissue. Complex plaques were lesions with ruptured plaque or spontaneous or unhealed dissection. Aneurysmal dilatation and reference segments were assessed using standard IVUS quantitative techniques. Twenty-one lesions (27%) were classified as true aneurysms, 3 (4%) were classified as pseudoaneurysms, 12 (16%) were complex plaques, and the other 41 (53%) were normal arterial segments adjacent to > or =1 stenosis. The maximum lumen area within the aneurysmal segment was largest for pseudoaneurysm (35.1 +/- 10.4 mm(2)), 22.1 +/- 9.9 mm(2) for true aneurysm, and similar for complex plaques (11.2 +/- 3.5 mm(2)) and normal segments with adjacent stenoses (13.8 +/- 6.4 mm(2)): analysis of variance, p <0.0001. Only one third of angiographically diagnosed aneurysms had the IVUS appearance of a true or pseudoaneurysm. Instead, most angiographically diagnosed aneurysms had the morphology of complex plaques or normal segments with adjacent stenoses.

Lumen loss in transplant coronary artery disease is a biphasic process involving early intimal thickening and late constrictive remodeling: results from a 5-year serial intravascular ultrasound study

BACKGROUND

Coronary artery disease is the major cause of late cardiac allograft failure. However, few data exist regarding the natural history of changes in intimal and external elastic membrane (EEM) areas after heart transplantation.

METHODS AND RESULTS

In 38 transplant recipients, serial intravascular ultrasound examinations were performed 3.7+/-2.2 weeks after transplantation and annually thereafter for 5 years. In 59 coronary arteries, we compared 135 matched segments among serial studies. In each segment, intravascular ultrasound images were digitized at 1-mm intervals, and mean values of EEM and lumen and intimal areas were analyzed. In the first year after transplantation, the intimal area increased significantly from 1.8+/-1.6 to 3.0+/-2.1 mm(2) (P<0.001). Subsequently, the annual increase in intimal area decreased. EEM area did not change during the first year; however, between years 1 and 3, significant expansion of EEM area occurred (15.4+/-4.6 to 17.2+/-5.4 mm(2), P<0.001). Thereafter, EEM area decreased significantly from 17.2+/-5.4 mm(2) (year 3) to 15.1+/-4.9 mm(2) (year 5, P=0.01). Different mechanisms of lumen loss were observed during 2 phases after transplantation: early lumen loss primarily caused by intimal thickening and late lumen loss caused by EEM area constriction.

CONCLUSIONS

This serial ultrasound study revealed that most of the intimal thickening occurred during the first year after heart transplantation. Changes in the EEM area showed a biphasic response, consisting of early expansion and late constriction. Thus, different mechanisms of lumen loss were observed during the early and late phases after transplantation.

Relation between coronary artery remodelling (compensatory dilatation) and stenosis in human native coronary arteries

OBJECTIVES

To investigate the contribution of plaque size and vessel remodelling to coronary artery stenosis and to assess the role of vessel shrinkage (negative remodelling) across a wide range of lesions.

DESIGN

Postmortem study of coronary remodelling in perfusion fixed hearts.

SUBJECTS

24 men and 24 women who died suddenly with coronary artery disease.

MAIN OUTCOME MEASURES

Percentage stenosis, percentage plaque burden, percentage remodelling, and arc of normal vessel were measured and related to age, sex, smoking status, and history of hypertension.

RESULTS

There was a positive relation between percentage stenosis and percentage plaque burden (r = 0.6, p < 0.0001) and an inverse relation between percentage stenosis and percentage remodelling (r = -0.4, p < 0.0001). Multilinear regression modelling showed that luminal stenosis = 1.0 (plaque burden) - 0.4 (vessel remodelling). Remodelling was greater in lesions that would not have been significant at angiography (</= 25% stenosis) than in the remaining lesions (25.9 (26)% v 10.0 (21.1)%, p < 0.0001, respectively) and was reduced in segments with circumferential plaques (12.7 (24.5)% v 20.7 (24.3)% in eccentric plaques, p = 0.001). Remodelling did not correlate with age, sex, or smoking. Negative remodelling was present in 62 lesions with a stenosis > 25% versus 10 lesions with </= 25% stenosis (p < 0.0001). Lesions with negative remodelling had greater plaque burden and luminal stenosis and a reduced arc of normal segment.

CONCLUSION

Outward arterial remodelling negates the stenosing effect of increasing plaque size. Significant coronary stenoses arise from a failure of this outward remodelling in the face of a large plaque burden. Coronary arterial remodelling is unrelated to sex or smoking and is plaque specific.

Relation between coronary artery remodelling (compensatory dilatation) and stenosis in human native coronary arteries

OBJECTIVES

To investigate the contribution of plaque size and vessel remodelling to coronary artery stenosis and to assess the role of vessel shrinkage (negative remodelling) across a wide range of lesions.

DESIGN

Postmortem study of coronary remodelling in perfusion fixed hearts.

SUBJECTS

24 men and 24 women who died suddenly with coronary artery disease.

MAIN OUTCOME MEASURES

Percentage stenosis, percentage plaque burden, percentage remodelling, and arc of normal vessel were measured and related to age, sex, smoking status, and history of hypertension.

RESULTS

There was a positive relation between percentage stenosis and percentage plaque burden (r = 0.6, p < 0.0001) and an inverse relation between percentage stenosis and percentage remodelling (r = –0.4, p < 0.0001). Multilinear regression modelling showed that luminal stenosis = 1.0 (plaque burden) − 0.4 (vessel remodelling). Remodelling was greater in lesions that would not have been significant at angiography (⩽ 25% stenosis) than in the remaining lesions (25.9 (26)% v10.0 (21.1)%, p < 0.0001, respectively) and was reduced in segments with circumferential plaques (12.7 (24.5)% v20.7 (24.3)% in eccentric plaques, p = 0.001). Remodelling did not correlate with age, sex, or smoking. Negative remodelling was present in 62 lesions with a stenosis > 25% versus 10 lesions with ⩽ 25% stenosis (p < 0.0001). Lesions with negative remodelling had greater plaque burden and luminal stenosis and a reduced arc of normal segment.

CONCLUSION

Outward arterial remodelling negates the stenosing effect of increasing plaque size. Significant coronary stenoses arise from a failure of this outward remodelling in the face of a large plaque burden. Coronary arterial remodelling is unrelated to sex or smoking and is plaque specific.

Arterial remodeling and coronary artery disease: the concept of "dilated" versus "obstructive" coronary atherosclerosis

Traditionally, the development of coronary artery disease (CAD) was described as a gradual growth of plaques within the intima of the vessel. The outer boundaries of the intima, the media and the external elastic membrane (EEM), were thought to be fixed in size. In this model plaque growth would always lead to luminal narrowing and the number and severity of angiographic stenoses would reflect the extent of coronary disease. However, histologic studies demonstrated that certain plaques do not reduce luminal size, presumably because of expansion of the media and EEM during atheroma development. This phenomenon of "arterial remodeling" was confirmed in necropsy specimens of human coronary arteries. More recently, the development of contemporary imaging technology, particularly intravascular ultrasound, has allowed the study of arterial remodeling in vivo. These new imaging modalities have confirmed that plaque progression and regression are not closely related to luminal size. In this review, we will analyze the role of remodeling in the progression and regression of native CAD, as well as its impact on restenosis after coronary intervention.

Compensatory enlargement and stenosis develop in apoE(-/-) and apoE*3-Leiden transgenic mice

Atherosclerotic mouse models develop little ischemic organ damage and no infarctions, despite the presence of large atherosclerotic lesions. Therefore, we hypothesize that luminal changes do not follow atherosclerotic lesion development. Because a phenomenon that may explain the discrepancy between luminal changes and lesion size is vascular remodeling, we measured parameters of vascular remodeling in the carotid arteries (CAs), thoracic aorta (TA), and abdominal aorta (AA) of apolipoprotein E (apoE)-deficient (apoE(-/-)) and apoE*3-Leiden mice, 2 well-known mouse models of atherosclerosis. Atherosclerotic lesions were classified (American Heart Association [AHA] types II through V), and plaque thickness, compensatory enlargement versus constrictive remodeling, lumen diameter, stenosis, and media thickness were measured relative to the nondiseased arterial wall. In CAs, plaque thickness increased during atherogenesis. CAs showed compensatory enlargement (apoE(-/-) 55%, apoE*3-Leiden 38%). Regression analysis revealed a positive correlation between plaque and lumen area (for apoE(-/-), R=0.95; for apoE*3-Leiden, R=0.90). Medial thinning and elastolysis were also observed. During atherogenesis, lumen diameter decreased (apoE(-/-) -69%, apoE*3-Leiden -40%), and stenosis >70% developed. TA and AA showed similar features, but neither developed a progressive decrease in lumen diameter or stenosis >70%. In CAs, TA, and AA of apoE(-/-) and apoE*3-Leiden mice, atherogenesis is associated with compensatory enlargement, medial thinning, and elastolysis. A progressive decrease in lumen diameter and stenoses >70% occur only in CAs. Vascular remodeling is more prominent in apoE(-/-) mice.

Mechanical and structural characteristics of vulnerable plaques: analysis by coronary angioscopy and intravascular ultrasound

OBJECTIVES

Mechanical and structural characteristics of vulnerable plaques were evaluated using coronary angioscopy and intravascular ultrasound.

BACKGROUND

Mechanical stress and composition of plaques play an important role in plaque disruption.

METHODS

Thirty-eight lesions in 38 patients were examined pre-interventionally. The plaques were classified as either yellow or white using coronary angioscopy. Intravascular ultrasound imaging was performed simultaneously with electrocardiographic and intracoronary pressure recordings to calculate distensibility index and stiffness beta. Moreover, the type of remodeling was classified.

RESULTS

We identified 27 patients with yellow plaques and 11 patients with white plaques. Patients with yellow plaques presented acute coronary syndromes more frequently than stable angina (85% vs. 36%, p < 0.01). The distensibility index in yellow plaques was significantly greater than it was in white plaques (2.7 +/- 0.8 mm Hg(-1) vs. 0.7 +/- 0.8 mm Hg(-1), p < 0.0001), while stiffness beta for white plaques was significantly greater than it was for yellow plaques (34.9 +/- 16.3 vs. 8.7 +/- 2.7, p < 0.0001). Compensatory enlargement occurred more frequently with yellow plaques than with white plaques (56% vs. 9%, p < 0.01), while paradoxical shrinkage occurred more frequently with white plaques than it did with yellow plaques (64% vs. 4%, p < 0.001).

CONCLUSIONS

Yellow plaques with an increased distensibility and a compensatory enlargement may be mechanically and structurally weak. As a result, mechanical "fatigue," caused by repetitive stretching, may lead to plaque disruption. Plaques with a high distensibility and a compensatory enlargement may be vulnerable.

Effect of coronary risk factors on arterial compensatory enlargement in japanese middle-aged patients with de novo single-vessel disease--an intravascular ultrasound study

BACKGROUND

Compensatory enlargement (CE) of atherosclerotic human arteries has been reported; however, the pattern of arterial remodeling in response to plaque formation is not unique.

HYPOTHESIS

The study was undertaken to determine the extent of coronary artery compensatory enlargement at stenotic lesions and to correlate the arterial compensatory enlargement with risk factors.

METHODS

We studied 62 patients with stable angina and de novo single-vessel disease using intravascular ultrasound and obtained good images in 42 patients (68%). The vessel cross-sectional area (VA), lumen cross-sectional area (LA), and plaque cross-sectional area (PA) were measured at the lesion site and at proximal and distal reference sites. Positive CE was defined as increase in VA of lesion site > 10% compared with that of proximal reference site (CE group, n = 15); shrinkage was defined as reduction in VA of lesion site > 10% compared with that of proximal reference site (S group, n = 14); inadequate CE was defined as intermediate between CE and S (IE group, n = 13). All subjects had coronary risk factors measured before this study.

RESULTS

There was no difference in VA, LA, or PA among the three groups at the proximal and distal reference sites, nor in LA at the lesion site; however, VA and PA were significantly smaller in the S group than in the other groups (p < 0.01). Of coronary risk factors, increased systolic blood pressure (SBP), increased diastolic blood pressure (DBP), and decreased high-density lipoprotein cholesterol (HDL-c) levels had the strongest association with shrinkage (p < 0.05).

CONCLUSION

Hypertension and decreased HDL level may contribute to the shrinkage response in middle-aged patients with stable angina.

Aggressive versus moderate lipid-lowering therapy in postmenopausal women with hypercholesterolemia: Rationale and design of the Beyond Endorsed Lipid Lowering with EBT Scanning (BELLES) trial

BACKGROUND

Electron beam tomography (EBT) is a noninvasive technique that allows the study of the entire coronary artery tree during a brief imaging session without the injection of any contrast media. Atherosclerosis is identified vicariously through the visualization of coronary calcific deposits. Quantitative assessments of calcium burden, such as calcium volume scores, have been shown to be a useful means to assess treatment-related changes in the extent of atherosclerotic plaques. Historically, the elderly female population has received less medical recognition regarding the risk and severity of coronary heart disease (CHD).

METHODS

In the BELLES (Beyond Endorsed Lipid Lowering with EBT Scanning) trial, the presence of asymptomatic CHD in 600 postmenopausal women will be assessed by EBT. In this 1-year, multicenter, randomized, double-blind, parallel-group study, aggressive lipid-lowering treatment will be compared with moderate lipid-lowering treatment in postmenopausal women with hypercholesterolemia. The hypothesis we will test is that aggressive lipid-lowering therapy with 80 mg/d atorvastatin can produce greater reductions in atherosclerotic plaque burden as assessed by volumetric calcium scores than a moderate treatment with 40 mg/d pravastatin. The primary outcome measure will be the percent change from baseline in total CVS determined by EBT at 12 months.

CONCLUSIONS

The results of the BELLES trial will help assess the actual incidence of CHD in postmenopausal women and the relative ability of two different lipid-lowering therapies to halt its progression.

Role of vascular remodeling in the pathogenesis of early transplant coronary artery disease: a multicenter prospective intravascular ultrasound study

BACKGROUND

Luminal narrowing in transplant coronary artery disease is thought to be primarily caused by intimal proliferation, and the role of vascular remodeling is less certain.

METHODS AND RESULTS

We studied cardiac allografts from 83 prospectively recruited patients immediately and 1 year after transplant using intravascular ultrasound in a multicenter study. We measured coronary artery dimensions in 310 angiographically matched segments (175 were also fully matched by ultrasound criteria). At 1 year, lumen area changed by -1.8 +/- 3.7 mm(2) (p < 0.0001, 14% of baseline lumen area). Thirty-three percent of this luminal loss was due to intimal thickening and 67% to vessel shrinkage. Shrinkage also occurred (-0.9 +/- 3.2 mm(2), 7% of baseline total area) in segments free of detectable intimal disease at baseline and at 1 year. Using the mean baseline total vessel area (13.9 mm(2)) as the cutoff, we divided the cohort into the large and the small coronary-segment groups. The large-segment group (n = 176) shrank more (-2.6 +/- 4.4 vs. -0.03 +/- 2.8 mm(2), p < 0.0001), but intimal growth was similar in both groups (0.8 +/- 2.2 vs. 0.4 +/- 1.3 mm(2), p = not significant). Analysis of the 175 fully ultrasound matched sub-cohort showed similar results. Changes in intimal area, total vessel area, and lumen area were similar in segments with (n = 132) and segments without (n = 178) pre-existing donor disease. Despite overall shrinkage, change in total vessel area positively correlated with change in intimal area (r = 0.29, p < 0.0001).

CONCLUSION

In large coronary segments, coronary artery shrinkage plays an important role in the loss of luminal diameter early after cardiac transplantation, whereas new intimal growth occurs in both large and small segments. Pre-existent donor disease does not aggravate these processes. Compensatory remodeling with increasing intimal growth retards the rate of lumen loss. As is intimal thickening, shrinkage and compensatory remodeling are important pathogenic mechanisms in transplant coronary artery disease.

Relation between preintervention remodeling and late arterial responses to coronary angioplasty or atherectomy

We used the serial intravascular ultrasound (IVUS) data from the Serial Ultrasound REstenosis trial to explain why positive remodeling lesions have a higher rate of clinical restenosis after non-stent interventions. Serial IVUS was performed before intervention and immediately and 1 and 6 months after percutaneous transluminal coronary angioplasty (n = 35) or directional coronary atherectomy (n = 26). External elastic membrane, lumen, and plaque + media (external elastic membrane minus lumen) areas were measured at the reference and stenosis. Stenoses were divided into 3 groups: positive remodeling (lesion greater than proximal reference external elastic membrane), intermediate remodeling (lesion external elastic membrane smaller than proximal reference but larger than distal reference), and negative remodeling (lesion equal to or less than distal reference external elastic membrane). The early (postintervention to 1 month) and late (1- to 6-month) changes in lesion external elastic membrane and plaque + media areas were compared. An early increase in plaque + media area was associated with an equal or greater increase in external elastic membrane area in positive (r = 0.78, p < 0.0001), intermediate (r = 0.69, p < 0.0001), and negative (r = 0.59, p = 0.0003) remodeling lesions. A late (1- to 6-month) decrease in external elastic membrane area correlated inversely with the early increase in plaque + media area in positive (r = 0.77, p = 0.0002) and intermediate (r = 0.45, p = 0.0003), but not in negative (r = 0.02, p = 0.9) remodeling lesions. In positive remodeling lesions, the early increase in plaque + media area was associated with both an exaggerated early increase and late decrease in external elastic membrane area. Positive remodeling lesions have an exaggerated early increase in external elastic membrane area and, especially, an exaggerated late decrease in external elastic membrane area after percutaneous transluminal coronary angioplasty and directional coronary atherectomy. This may explain that the increased clinical restenosis after positive remodeling lesions is treated with non-stent interventions.

Coronary remodeling of proximal and distal stenotic atherosclerotic plaques within the same artery by intravascular ultrasound study

The aim of this intravascular ultrasound study was to compare the type and the degree of vessel remodeling in proximal and distal de novo lesions within the same coronary artery in patients with stable angina pectoris. Seventy-six de novo coronary artery lesions in 38 coronary arteries of 38 patients were imaged by intravascular ultrasound. The vessel area (VA) within the external elastic lamina and the lumen area (LA) were measured, and the wall area (VA-LA) was calculated at the lesion site, and the proximal and distal reference sites. The VA ratio was defined as (lesion VA/average of the proximal and distal reference VAs) to represent the degree of vessel remodeling. The proximal coronary segments showed compensatory enlargement more often (68% vs 29%, p < 0.01) than the distal segments, and the VA ratio at the lesion site was significantly larger (1.1 +/- 0.3 vs 1.0 +/- 0.2, p <0 .01) in proximal segments than in distal segments. The type of coronary remodeling was discordant in 61% and concordant in only 39% of coronary arteries between the proximal and distal segments. The type of coronary remodeling of proximal and distal coronary lesions was inhomogeneous, even within the same vessel. Proximal coronary segments showed more prominent compensatory enlargement than distal segments, which have a similar degree of luminal narrowings.

Intravascular ultrasound: novel pathophysiological insights and current clinical applications

Intravascular ultrasound (IVUS) is a valuable adjunct to angiography, providing new insights in the diagnosis of and therapy for coronary disease. Angiography depicts only a 2D silhouette of the lumen, whereas IVUS allows tomographic assessment of lumen area, plaque size, distribution, and composition. The safety of IVUS is well documented, and the assessment of luminal dimensions represents an important application of this modality. Comparative studies show the greatest disparities between angiography and ultrasound after mechanical interventions. In young subjects, normal intimal thickness is typically approximately 0.15 mm. With IVUS, lipid-laden lesions appear hypoechoic, fibromuscular lesions generate low-intensity echoes, and fibrous or calcified tissues are echogenic. Calcium obscures the underlying wall (acoustic shadowing). The extent and severity of disease by angiography and ultrasound are frequently discrepant. Arterial remodeling refers to changes in vascular dimensions during the development of atherosclerosis. At diseased sites, the external elastic membrane may actually shrink in size, contributing to luminal stenosis. The interpretation of IVUS relies on simple visual inspection of acoustic reflections to determine plaque composition. However, different tissue components may look quite similar, and artifacts may adversely affect ultrasound images. IVUS commonly detects occult disease in angiographically "normal" sites. In ambiguous lesions, ultrasound permits lesion quantification, particularly for left main coronary disease. IVUS has emerged as the optimal method for the detection of transplant vasculopathy. An important potential application of ultrasound is the identification of atheromas at risk of rupture. The mechanisms of action of interventional devices have been elucidated using IVUS, and ultrasound is used by some operators to select the most suitable interventional device. IVUS-derived residual plaque burden is the most useful predictor of clinical outcome. In restenosis after balloon angioplasty, negative remodeling is a major mechanism of late lumen loss. IVUS is not routinely used for stent optimization, and there is no consensus regarding optimal procedural end points. Ultrasound has proven useful in evaluating brachytherapy. New and emerging applications for IVUS are continuing to evolve, particularly in atherosclerosis regression-progression trials.

Intravascular ultrasound assessment of ambiguous coronary lesions

Accurate assessment of coronary lesions is essential for clinical decision-making. While angiography has long been accepted as the gold standard investigation, this technique provides only a planar 2-D silhouette of the arterial lumen and therefore has limited accuracy in the setting of vessel tortuosity or overlap, bifurcational and eccentric lesions, and diffusely diseased arteries. By providing high-resolution cross-sectional imaging through the arterial wall, intravascular ultrasound (IVUS) can overcome many of these limitations and accurately quantify angiographically indeterminate lesions. Angiographic evaluation of the left main coronary artery presents particular challenges that are ideally resolved with IVUS examination. The role of IVUS in the assessment of coronary stenoses of angiographically intermediate severity (50-70%) continues to evolve. Recent data correlating IVUS with intracoronary flow and pressure measurements suggest that epicardial coronary artery lesions with minimum lumen area of less than 3-4 mm2 may be haemodynamically significant. In addition to accurately quantifying minimum lumen diameter and area at the lesion site, IVUS can characterise coronary artery plaque morphology, and it may have the potential to predict plaque complications.

Impact of coronary artery remodeling on clinical presentation of coronary artery disease: an intravascular ultrasound study

OBJECTIVES

We examined the association between the features of the culprit lesion in coronary artery disease (CAD) and clinical presentation as shown by intravascular ultrasound (IVUS).

BACKGROUND

The association between coronary remodeling pattern and clinical presentation of CAD is unclear.

METHODS

We analyzed 125 selected patients who underwent preintervention IVUS. Acute myocardial infarction (AMI) and unstable angina pectoris (UAP) were categorized as an acute coronary syndrome (ACS), and stable angina pectoris (SAP) and old myocardial infarction (OMI) as stable CAD. Coronary remodeling patterns and plaque morphology of the culprit lesion obtained by IVUS were analyzed in terms of their association with clinical presentation or angiographic morphology.

RESULTS

Angiographically complex lesions were associated with ACS and OMI. In patients with a complex lesion, positive remodeling was observed more frequently than in those with a simple lesion. In AMI and UAP, positive remodeling was observed more frequently than in SAP and OMI (82% vs. 78% vs. 33% vs. 40%, respectively, p < 0.0001). The remodeling ratio was greater in AMI and UAP than in SAP and OMI (1.26 +/- 0.15 vs. 1.11 +/- 0.10 vs. 0.94 +/- 0.11 vs. 0.96 +/- 0.13, respectively, p < 0.0001). Furthermore, within ACS, the remodeling ratio was greater in AMI than in UAP (1.26 +/- 0.15 vs. 1.11 +/- 0.10, respectively, p < 0.05), whereas the frequency of positive remodeling was not different.

CONCLUSIONS

Positive remodeling was more frequently observed in ACS than in stable CAD. Moreover, the degree of positive remodeling was greater in AMI than in UAP. These results may reflect the impact of remodeling types and its degree in the culprit lesion of CAD on clinical presentation.

Hyperplasia of coronary intima in young males in relation to development of coronary heart disease in adults

The aim of the investigation was to study structural features of coronary arteries in young males which may influence the development of stenosing coronary atherosclerosis in older age. We studied the coronary arteries from 84 males, 10-39 years old, who died from accidents in Moscow, Malmo and Riga, and 98 males aged 40 and above from Moscow who died from coronary heart disease (71 cases) or other diseases (27 cases). In children and young males from all three cities, musculo-elastic hyperplasia of the coronary intima took place constantly but with different degrees of expression; a strict relationship of the intimal thickness and age was observed. Histometric investigations of the right coronary artery showed that in young males of Riga, in comparison with those of Malmo, the intima was significantly thicker both outside (69.6+/-2.8 and 58. 2+/-2.5 microm) and within the area of cushion like thickening (118. 8+/-4.0 and 101.9+/-3.8 microm), they had more extended cushion-like thickening of intima (42.6+/-3.0 and 30.8+/-3.3% to the length of the artery circumference) and destroyed parts of the internal elastic lamina (28.3+/-1.9 and 19.1+/-1.7% of its length). In males older than 40 years, severe coronary atherosclerosis and stenosis was also significantly more common in Riga than in Malmo. Our data indicate that with age the intimal musculo-elastic hyperplasia in the coronary arteries is transformed to a fibro-elastic layer. The thickness of this layer in the presence of stenosing plaques (>75% of arterial lumen) was much greater than in the presence of plaques with stenoses less than 50% (188.1+/- 7.3 and 69.8+/-4.5 microm, respectively).

CONCLUSION

The development of stenosing coronary atherosclerosis is closely related to the degree of musculo-elastic intimal hyperplasia in childhood and young age. The formation of a fibro-elastic layer in the coronary intima decreases the ability of the artery to dilate during the development of atherosclerosis.

Coronary artery compliance and adaptive vessel remodelling in patients with stable and unstable coronary artery disease

OBJECTIVE

To test the hypothesis that patients with unstable coronary syndromes show accentuated compensatory vessel enlargement compared with patients with stable angina, and that this may in part be related to increased coronary artery distensibility.

DESIGN AND PATIENTS

In 23 patients with unstable coronary syndromes (10 with non-Q wave myocardial infarction and 13 with unstable angina), the culprit lesion was investigated by intravascular ultrasound before intervention. The vessel cross sectional area (VA), lumen area (LA), and plaque area (VA minus LA) were measured at end diastole and end systole at the lesion site and at the proximal and distal reference segments. Similar measurements were made in 23 patients with stable angina admitted during the same period and matched for age, sex, and target vessel. Calculations were made of remodelling index (VA at lesion site / VA at reference site), distensibility index ([(delta A/A)/delta P] x 10(3), where delta A is the luminal area change in systole and diastole and delta P the difference in systolic and diastolic blood pressure measured at the tip of the guiding catheter during a cardiac cycle), and stiffness index beta ([ln(P(sys)/P(dias))]/(delta D/D), where P(sys) is systolic pressure, P(dias) is diastolic pressure, and delta D is the difference between systolic and diastolic lumen diameters). Positive remodelling was defined as when the VA at the lesion was > 1.05 times larger than at the proximal reference site, and negative remodelling when the VA at the lesion was < 0.95 of the reference site.

RESULTS

Mean (SD) LA at the lesion site was similar in both groups (4.03 (1.8) v 4.01 (1. 93) mm(2)), while plaque area was larger in the unstable group (13. 29 (4.04) v 8.34 (3.6) mm(2), p < 0.001). Remodelling index was greater in the unstable group (1.14 (0.18) v 0.83 (0.15), p < 0.001). Positive remodelling was observed in 15 patients in the unstable group (65%) but in only two (9%) in the stable group (p < 0.001). Negative remodelling occurred only in two patients with unstable symptoms (9%) but in 17 (74%) with stable symptoms. At the proximal reference segment, the difference in LA between systole and diastole was 0.99 (0.66) mm(2) in the unstable group and 0.39 (0.3) mm(2) in the stable group (p < 0.001), and the calculated coronary artery distensibility was 3.09 (2.69) and 0.94 (0.83) per mm Hg in unstable and stable patients, respectively (p < 0.001). The stiffness index beta was lower in patients with unstable angina (1.95 (0.94) v 3.1 (0.96), p < 0.001).

CONCLUSIONS

Compensatory vessel enlargement occurs to a greater degree in patients with unstable than with stable coronary syndromes, and is associated with increased coronary artery distensibility.

Intravascular ultrasound findings of negative arterial remodeling at sites of focal coronary spasm in patients with vasospastic angina

BACKGROUND

There are few data about the intravascular ultrasound (IVUS) findings in patients with vasospastic angina, especially regarding patterns of vascular remodeling.

METHODS AND RESULTS

Coronary spasm was documented by angiography and electrocardiographic evidence of ischemia in 36 patients after administration of ergonovine (cumulative doses up to 350 microg). After relief of spasm with 1000 microg of intracoronary nitroglycerin, quantitative angiography and IVUS imaging were performed and analyzed by standard methods. The 36 focal spasm sites were compared with the proximal and distal reference segments. The angiographic baseline minimum lumen diameter measured 1.78 +/- 0.66 mm, which decreased to 0.66 +/- 0.38 mm with ergonovine provocation (P <.0001), increased to 2.66 +/- 0.64 mm after intracoronary nitroglycerin (P <.0001 compared with baseline and after ergonovine), and did not change after IVUS imaging (2.66 +/- 0.63, P =.9). By IVUS, atherosclerotic lesions were observed at all coronary spasm sites; the mean plaque burden measured 56% at the spasm site and 35% at the reference. Spasm site plaque composition was hypoechoic in 31 and hyperechoic, noncalcific in 5; there was no calcium. The mean eccentricity index (maximum divided by minimum plaque thickness) was 6.7. Positive remodeling (spasm site arterial area greater than proximal reference) was present in 5; intermediate remodeling (proximal reference greater than spasm site greater than distal reference arterial area) was present in 7; and negative remodeling (spasm site arterial area less than distal reference) was present in 24.

CONCLUSIONS

Sites of vasospasm in patients with variant angina showed characteristics of early atherosclerosis, except for an unusually high incidence of negative arterial remodeling.

Techniques characterizing the coronary atherosclerotic plaque: influence on clinical decision making?

The composition of the atherosclerotic lesion rather than the degree of stenosis is currently considered to be the most important determinant for acute clinical events. Modalities capable of characterizing the atherosclerotic lesion may be helpful in understanding its natural history and detecting lesions with high risk for acute events. Speaking grossly, three histologic features of the vulnerable plaque have been reported: size of the atheroma, thickness of the fibrous cap, and inflammation. Imaging techniques are currently being deployed and are under development to aid visualization of the vulnerable coronary plaque. Most of these diagnostic modalities have the potential to detect locally one or more of the three histologically defined features of vulnerable plaque. This review will focus on imaging techniques that have been developed to characterize the atherosclerotic lesion. Most catheter-based visualization techniques will provide insight into components of the local atherosclerotic plaque which may limit their predictive value for the occurrence of a clinical event. Therefore, the clinical relevance of these imaging tools will be discussed.

Longitudinal study of vascular remodeling in coronary arteries after heart transplantation

Cross-sectional studies by intravascular ultrasound (IVUS) in heart transplant recipients have suggested that vascular remodeling occurs in coronary arteries years after transplant. However, no reports describe vascular remodeling in the same cohort of patients studied prospectively using morphometric analysis (10 evenly spaced images obtained from a slow pullback from the left anterior descending coronary artery). Morphometric analysis better reflects total vessel anatomy compared with previously reported site (2 to 3 images) analysis. We reviewed 20 patients studied by IVUS at 2 months, 1 year, 2 years, and 3 years after heart transplant.Over time, the coronary artery luminal area decreased from baseline level of 12.0 mm(2) to a 3-year mark of 9.7 mm(2) (p = 0.02). Vessel shrinkage was seen in 16/20 patients. After an initial rise in intimal parameters (maximal intimal thickness, intimal index, and plaque area) from baseline to 1 year, we found a significant decrease in intimal parameters between Year 1 and Year 3 after transplant. For example, plaque area decreased from 2.05 mm(2) at 1 year post-transplant to 1.48 mm(2) by 3 years post-transplant (p = 0.05). In a majority of heart transplant patients, early intimal thickening in the first year post-transplant is accompanied by constrictive remodeling. Over the subsequent 2 years, further constrictive remodeling is seen despite a decrease in intimal area.

Assessment of coronary compensatory enlargement by three-dimensional intravascular ultrasound

Several techniques have been used to demonstrate that human arteries respond to atherosclerosis by increasing their total arterial area to prevent a decrease in blood flow. Three-dimensional reconstructions of coronary arteries can document this compensatory response accurately and specifically. Seven human coronary arteries were reconstructed using intravascular ultrasound and biplane angiography, and vessel geometries were quantified. In all seven vessels, as plaque area increased, overall vessel area increased (R = 0.986, 0.933, 0.984, 0.678, 0.763, 0.963, and 0.830), but luminal cross-sectional area did not significantly decrease. Focal compensatory enlargement was identified in each vessel, and in some cases this response appeared to occur until the vessel was 65% occluded. Luminal enlargement near the proximal ends was attributed to the natural taper of the vessel. The semi-automated, three-dimensional segmentation technique used in this study allows reproducible quantification, as there is no subjective manual tracing involved. Following the intravascular ultrasound transducer in time and space with biplane angiography allows for accurate reconstruction with or without automated pullback devices. Information on the rate of change of vessel measurements is also presented, which, when combined with visualization of accurate 3D geometry, provides a unique assessment of coronary compensatory enlargement. This reconstruction technique can be applied in a clinical environment with no major modification.

Cholesterol-lowering treatment is associated with improvement in coronary vascular remodeling and endothelial function in patients with normal or mildly diseased coronary arteries

Coronary vascular remodeling and altered endothelial function have been described in the early stages of native atherosclerosis. The purpose of this study was to evaluate the association between cholesterol-lowering therapy and coronary vascular remodeling and endothelial function in patients with normal or mildly diseases coronary arteries. Patients (N=101) with normal or mildly diseased coronary arteries by coronary angiography underwent intravascular ultrasound examination of the left anterior descending coronary artery. Vessel and lumen area, atherosclerotic plaque area, and plaque morphology were evaluated. Vascular reactivity was examined with the use of intracoronary adenosine, acetylcholine, and nitroglycerin. Patients were divided into 3 groups based on the total cholesterol levels: group 1 (n=25), patients with a history of hypercholesterolemia adequately treated (total cholesterol <240 mg/dL); group 2 (n=26), patients with hypercholesterolemia not adequately controlled (total cholesterol >/=240 mg/dL); and group 3 (n=50), patients without hypercholesterolemia. Vessel area and lumen area were significantly greater in groups 1 and 3 than in group 2 (for respective values in groups 1, 2, and 3: vessel area 11.9+/-0.5, 10.6+/-0.4, and 11.8+/-0.4 mm(2), both P<0.05; lumen area 8.3+/-0.4, 6.9+/-0.3, and 8.9+/-0.3 mm(2), both P<0.01). However, plaque areas in groups 1 and 2 were similar. Furthermore, acetylcholine-induced percent increases in coronary blood flow were significantly greater in groups 1 and 3 than in group 2 (for respective values in groups 1, 2, and 3: 70.5+/-20.1%, 22.8+/-13.7%, and 68.6+/-14.8%, both P<0. 05). Cholesterol-lowering treatment is associated with an improvement in coronary lumen area that results not from a decrease in plaque area but from an increase in vessel area, reflecting vascular remodeling. Additionally, this adaptive process may occur in association with an improvement of endothelium-dependent vasodilation of the resistance coronary artery.

Extent and direction of arterial remodeling in stable versus unstable coronary syndromes : an intravascular ultrasound study

BACKGROUND

The morphological characteristics of coronary plaques in patients with stable versus unstable coronary syndromes have been described in vivo with intravascular ultrasound, but the relationship between arterial remodeling and clinical presentation is not well known.

METHODS AND RESULTS

We studied 85 patients with unstable and 46 patients with stable coronary syndromes using intravascular ultrasound before coronary intervention. The lesion site and a proximal reference site were analyzed. The remodeling ratio (RR) was defined as the ratio of the external elastic membrane (EEM) area at the lesion to that at the proximal reference site. Positive remodeling was defined as an RR >1.05 and negative remodeling as an RR <0.95. Plaque area (13.9+/-5.5 versus 11.1+/-4.8 mm(2); P=0.005), EEM area (16.1+/-6.2 versus 13.0+/-4.8 mm(2); P=0. 004), and the RR (1.06+/-0.2 versus 0.94+/-0.2; P=0.008) were significantly greater at target lesions in patients with unstable syndromes than in patients with stable syndromes. Positive remodeling was more frequent in unstable than in stable lesions (51. 8% versus 19.6%), whereas negative remodeling was more frequent in stable lesions (56.5% versus 31.8%) (P=0.001).

CONCLUSIONS

Positive remodeling and larger plaque areas were associated with unstable clinical presentation, whereas negative remodeling was more common in patients with stable clinical presentation. This association between the extent of remodeling and clinical presentation may reflect a greater tendency of plaques with positive remodeling to cause unstable coronary syndromes.

Hyperemic coronary flow after optimized intravascular ultrasound-guided balloon angioplasty and stent implantation

OBJECTIVES

This study evaluated the acute physiological gain of adjunctive intravascular ultrasound (IVUS) guided balloon angioplasty and stent implantation.

BACKGROUND

Recent studies indicate safe coronary luminal enlargement and "stent-like" long-term outcomes using upsized balloons guided by IVUS.

METHODS

After angiographically guided balloon angioplasty in 20 patients with 1-vessel disease and normal left ventricular function, IVUS was performed to determine the size of the adjunctive balloon using the mean of the maximal luminal diameter and the maximal diameter of the external elastic membrane measured in the adjacent proximal and distal reference segments. Serial adenosine-induced hyperemic blood flow velocity measurements were performed using a 0.014" Doppler guide wire to determine the physiological lumen obstruction after standard balloon angioplasty, followed by IVUS-guided balloon angioplasty and stent implantation.

RESULTS

Upsized balloon angioplasty (increase balloon size: 0.98 +/- 0.26 mm; balloon:artery ratio 1.35 +/- 0.21) resulted in an additional increase of arterial dimensions: minimal lumen diameter (MLD) 2.18 +/- 0.38 mm to 2.73 +/- 0.51 mm; percent diameter stenosis (%DS) 34 +/- 13% to 19 +/- 22%; IVUS assessed minimal lumen area (MLA) 7.53 +/- 1.55 mm2 to 10.24 +/- 2.22 mm2 (all p < 0.0001). Major dissections (> or = type C) did not occur. Hyperemic blood flow velocity increased from 49.8 +/- 20.1 cm/s to 59.1 +/- 22.9 cm/s (p < 0.05) after IVUS-guided balloon angioplasty. Adjunctive stent implantation resulted in a further increase of MLD to 3.84 +/- 0.51 mm, %DS to -9 +/- 21% and MLA to 13.39 +/- 1.80 mm2 (all p < 0.0001), while hyperemic blood flow velocity remained unchanged (61.2 +/- 24.7 cm/s, p = 0.7).

CONCLUSIONS

Upsized IVUS-guided balloon angioplasty increases arterial coronary dimensions and the distal hyperemic blood flow velocity. Adjunctive stent implantation does not yield a further gain in the hyperemic blood flow velocity, indicating the absence of a functional residual lumen obstruction after IVUS-guided balloon angioplasty. This may explain a similar clinical outcome reported after those coronary interventions.

Intravascular ultrasound assessment of the presence of vascular remodeling in diseased human saphenous vein bypass grafts

Remodeling occurs in diseased human coronary arteries; however, reports of remodeling in diseased autologous saphenous vein bypass graft (SVG) stenoses are inconsistent. Preintervention intravascular ultrasound and quantitative coronary angiography were used to study 104 SVG stenoses in 93 consecutive patients. Lesion site and proximal and distal reference segment measurements included vein graft, external elastic membrane, lumen, wall (vein graft minus lumen), and plaque (external elastic membrane minus lumen) areas. Three indexes of remodeling were assessed: (1) lesion site SVG (or external elastic membrane) area was compared with the average reference segment, (2) SVG area was correlated with the wall area and external elastic membrane area was correlated with the plaque area, and (3) the impact of excess plaque accumulation (at the stenosis compared with the reference segment) on lumen compromise was calculated. Overall, the ratio of lesion/reference vein graft area was 1.07 +/- 0.25; however, 23 lesions were classified as negative remodeling (ratio <0.9), 37 as intermediate remodeling (ratio between 0.9 and 1.1), and 44 as positive remodeling (ratio >1.1). Reference segment vein graft area correlated with wall area (r = 0.906, p <0.0001), and external elastic membrane area correlated with plaque area (r = 0.703, p <0.0001). Similarly, lesion site vein graft area correlated with wall area (r = 0.978, p <0.0001), and external elastic membrane area correlated with plaque area (r = 0.961, p <0.0001). The regression line relating delta lumen area to delta wall area was y = -0.22 x - 6.2 (r = 0.451, p <0.0001) and the regression line relating delta lumen to delta plaque area was y = -0.47 x - 4.5 (r = 0.572, p <0.0001). (A slope of 0 would indicate perfect positive remodeling and a slope of 1.0 no positive remodeling.) Diseased SVGs undergo positive and negative remodeling similar to native coronary arteries.

Arterial remodeling in the left coronary system: the role of high-density lipoprotein cholesterol

OBJECTIVES

We sought to evaluate the plaque and patient variables related to arterial remodeling responses of early, de novo atherosclerotic lesions involving the left coronary artery.

BACKGROUND

Coronary artery remodeling is a lesion-specific process involving either enlargement or shrinkage of atherosclerotic coronary arteries. There are little histologic data available correlating plaque morphologic and patient clinical characteristics with the degree and type of arterial remodeling in early atherosclerosis.

METHODS

We studied 736 serial arterial sections from the left coronary system of 97 autopsy cases (mean age 33 +/- 11 years) by correlating the arterial remodeling response to plaque with demographic, serologic and histologic variables. Using the most proximal section as a reference, and considering the expected degree of internal elastic lamina tapering, remodeling was classified as positive (including neutral remodeling or compensatory enlargement) or negative.

RESULTS

Remodeling was classified as positive in 84.3% (compensatory in 30.6%) and negative in 15.7% of sections with an overall mean luminal stenosis of 10.4 +/- 9.9%. In the lesions with the greatest arterial cross-sectional narrowing from each case, compensatory enlargement was associated with higher high-density lipoprotein (HDL) cholesterol (59.4 +/- 27.2 mg/dl) compared with either neutral (49.3 +/- 15.5 mg/dl) or negative remodeling (30.4 +/- 5.2 mg/dl; p = 0.019). In subjects with advanced atherosclerosis (maximum American Heart Association histologic grade 5 atherosclerosis), there was a modest linear relationship between higher HDL cholesterol and the propensity for positive remodeling (r2 = 0.37; p = 0.025). On multivariate analysis, only HDL cholesterol was related to the arterial remodeling response.

CONCLUSIONS

Negative arterial remodeling occurs in early atherosclerosis. Higher HDL cholesterol may favor positive remodeling.

Impact of coronary artery remodeling on misinterpretation of angiographic disease eccentricity: evidence from intravascular ultrasound

This study was designed to examine the impact of coronary artery remodeling, enlargement or shrinkage, on the angiographic disease eccentricity. A total of 82 coronary sites from 73 patients with significant stenosis (>50%) were prospectively analyzed by both quantitative coronary angiography and intravascular ultrasound. By quantitative coronary angiography, the maximal and minimal distances from the center of the stenosis to the outline of the vessel wall were measured, and the eccentricity index was calculated by the formula [(maximal-minimal)/maximal]. By intravascular ultrasound, the maximal and minimal distances from the center of the lumen to the leading edge of the second echogenic zone were measured, and the eccentricity index was calculated by the same formula. For identifying the vessel remodeling, the total vessel area that was determined by tracing the leading edge of the second echogenic zone was measured at the stenotic sites and the adjacent proximal and distal segments. By quantitative coronary angiography, the maximal and minimal distances were 1.76+/-0.6 and 0.97+/-0.3 mm, respectively, yielding an eccentricity index of 0.42+/-0.2. The maximal and minimal distances by intravascular ultrasound were 2.77+/-0.6 mm and 1.46+/-0.4 mm, respectively, yielding an eccentricity index of 0.45+/-0.2 (NS). Although the average eccentricity index was not different between the two methods, there was substantially no correlation between the eccentricity index determined by the two methods (r = 0.38, y = 0.43x+0.22). However, this correlation was significantly improved (r = 0.55, y = 0.73x+0.12, P<0.001) when 44 stenotic segments with remodeling were excluded for comparison. These results indicate that coronary artery remodeling could be a major contributing factor to angiographic misinterpretation of disease eccentricity. We suggest that intravascular ultrasound is a powerful method that can accurately determine diseases eccentricity as well as disease severity.

Remodeling of atherosclerotic coronary arteries varies in relation to location and composition of plaque

The aim of this study was to determine the contribution of morphologic characteristics and location of plaque in remodeling of atherosclerotic coronary arteries. Consecutive intravascular ultrasound studies performed in native coronary arteries before an intervention were included in the study. Total vessel, lumen and plaque + media areas were measured at target lesion, and distal and proximal references. Remodeling index was calculated as target total vessel area/proximal reference total vessel area, and categorized into 3 groups based on relative total vessel-area ratio: (1) > 1.1 (group A, adequate remodeling); (2) 0.9 to 1.1 (group B, failure of compensatory enlargement); and (3) <0.9 (group C, coronary shrinkage). Eighty-nine narrowings were assessed in 80 intravascular ultrasound studies. Thirty-eight lesions (43%) were defined as soft and 51 (57%) as hard. Soft plaques were more prevalent in group A than in groups B and C (p = 0.001). Conversely, the arc of calcium was larger in group C lesions (p = 0.005). At distal segments, group A lesions were more prevalent than those in groups B and C, whereas at proximal segments group C lesions were more prevalent (p = 0.007). Multivariate analysis identified the arc of calcium and the location of plaque at distal segments as independent predictors of compensatory enlargement (odds ratio 0.94, 95% confidence interval 0.90 to 0.99; odds ratio 4.6; 95% confidence interval 1.4 to 15.7, respectively), whereas hard plaques were an independent predictor of coronary shrinkage (odds ratio 4.6; 95% confidence interval 1.7 to 12.5). In conclusion, composition and location of plaque appeared to be major determinants of vessel remodeling during the process of atherosclerosis.