Coronary Plaque Morphology Research Articles

Intravascular Ultrasound in Cardiovascular Medicine

Case presentation: A 38-year-old man underwent angiography 2 weeks after a non–ST-segment myocardial infarction. He was overweight and prehypertensive, with a blood pressure of 134/86 mm Hg. His biochemical parameters included low-density lipoprotein cholesterol (LDL-C) 127 mg/dL, high-density lipoprotein cholesterol (HDL-C) 38 mg/dL, and C-reactive protein (CRP) 3.2 mg/L. Angiography revealed mild disease throughout the coronary arteries and a hazy appearance that involved the proximal left anterior descending coronary artery. Intravascular ultrasound (IVUS) imaging revealed diffuse and extensive atherosclerosis with evidence of plaque rupture at multiple sites (Figure 1). In the presence of no significant luminal stenoses, the patient was treated medically with aspirin and low-dose statin therapy. Figure 1. Illustrative example of coronary angiography of the left anterior descending artery that appears to be free of irregularities, apart from a hazy appearance in the proximal segment. A representative cross-sectional tomographic image obtained by IVUS examination (top right) within the proximal segment (white arrow on angiogram) revealed substantial atheroma within the arterial wall. The bottom right segment illustrates a tomographic image of atheroma containing significant ulceration (5 o’clock) at the site of the gold arrow on the angiogram. The application of IVUS in this case highlights a number of important points with regard to the natural history of atherosclerosis and its modification by use of established medical therapies. The ability to image the entire arterial wall represents a significant advantage over coronary angiography. In the presence of minimal luminal stenoses, IVUS imaging in patients with coronary symptoms typically reveals extensive and diffuse atherosclerosis.1 Application of serial IVUS imaging in prospective clinical trials has enabled a greater understanding of the impact of antiatherosclerotic interventions on patients with established coronary artery disease (CAD). Ultrasonic coronary imaging has revealed essential details about the natural history of atherosclerosis. Atheroma formation begins at a …

C-reactive protein in vulnerable coronary plaques

Background: An increased level of serum C-reactive protein (CRP) is a known prognostic factor for acute coronary events and sudden cardiac death, and it is associated with coronary calcification. CRP...

Assessment of coronary plaque morphology by contrast-enhanced computed tomographic angiography: comparison with intravascular ultrasound

Computed tomographic (CT) angiography provides accurate noninvasive assessment for coronary artery stenosis. The ability of CT angiography to determine plaque morphology remains unclear. Twelve patients undergoing intravascular ultrasound for clinical indications underwent CT angiography for the evaluation of plaque morphology. Plaque morphology was classified as (1) soft, (2) fibrous, (3) fibrocalcific or (4) calcific. CT angiography data sets were evaluated for the presence and morphology of plaque in the coronary artery segments. The results were blindly compared with intravascular ultrasound results on a segment by segment basis using angiographic landmarks. Fifty-nine coronary segments were analyzed; 10 segments were normal and 49 contained plaque. Plaque morphology by intravascular ultrasound was soft in 12 segments, fibrous in four, fibrocalcific in 29 and calcific in four. To determine coronary segments with any plaque, CT angiography had a sensitivity of 100% (49 of 49) and specificity of 90% (9 of 10). To determine plaque morphology as calcified (fibrocalcific and calcific) versus noncalcified (soft and fibrous), CT angiography had a sensitivity of 100% (33 of 33) and a specificity of 94% (15 of 16). Overall accuracy for CT angiography to determine plaque morphology was 92% (54 of 59). CT angiography density values (Hounsfield units, mean+/-standard deviation) were significantly different for each plaque morphology: soft 23+/-71, fibrous 108+/-79, fibrocalcific 299+/-112 and calcific 404+/-264 (P<0.0001). CT angiography accurately characterized plaque morphology and may be a useful tool in noninvasive evaluation of plaque morphology during drug therapy trials.

Accuracy of In Vivo Coronary Plaque Morphology Assessment: A Validation Study of In Vivo Virtual Histology Compared With In Vitro Histopathology

The goal of the present study was to compare the accuracy of in vivo tissue characterization obtained by intravascular ultrasound (IVUS) radiofrequency (RF) data analysis, known as Virtual Histology (VH), to the in vitro histopathology of coronary atherosclerotic plaques obtained by directional coronary atherectomy. Vulnerable plaque leading to acute coronary syndrome (ACS) has been associated with specific plaque composition, and its characterization is an important clinical focus. Virtual histology IVUS images were performed before and after a single debulking cut using directional coronary atherectomy. Debulking region of in vivo histology image was predicted by comparing pre- and post-debulking VH images. Analysis of VH images with the corresponding tissue cross section was performed. Fifteen stable angina pectoris (AP) and 15 ACS patients were enrolled. The results of IVUS RF data analysis correlated well with histopathologic examination (predictive accuracy from all patients data: 87.1% for fibrous, 87.1% for fibro-fatty, 88.3% for necrotic core, and 96.5% for dense calcium regions, respectively). In addition, the frequency of necrotic core was significantly higher in the ACS group than in the stable AP group (in vitro histopathology: 22.6% vs. 12.6%, p = 0.02; in vivo virtual histology: 24.5% vs. 10.4%, p = 0.002). Correlation of in vivo IVUS RF data analysis with histopathology shows a high accuracy. In vivo IVUS RF data analysis is a useful modality for the classification of different types of coronary components, and may play an important role in the detection of vulnerable plaque.

Is Magnetic Resonance Image Guidance the Key to Opening Chronic Total Occlusions?

Through progressive plaque growth or fibrotic organization of occlusive thrombus, atherosclerosis may result in chronic total occlusion (CTO) of a major arterial conduit. If CTO develops slowly, collateral pathways may supply sufficient perfusion to retain tissue viability despite occlusion of the major inflow conduit. However, such collateral-mediated perfusion rarely matches that provided by an open main conduit, particularly during the peak demand of regional muscular activity. Although strategies to limit regional oxygen demand (eg, β-blockers for the treatment of angina pectoris) or to enhance collateral function (eg, a walking program for superficial femoral occlusion, experimental angiogenesis) may be of some benefit, these approaches generally offer less complete return of normal physiology and relief of ischemic symptoms than does direct revascularization of the occluded vessel. With surgical bypass, the nature of the occlusion (its length, duration, tortuosity, calcification) is less important than the presence of a suitable distal anastomotic target. On the other hand, with catheter-based techniques, success depends heavily on these lesion characteristics. In fact, crossing such occluded segments with a guidewire remains the dominant barrier to catheter-based treatments of occluded arterial segments. Once the guidewire has been passed successfully into the distal true lumen, the process of dilating and stenting the segment is usually straightforward and durable, at least with the use of drug-eluting stents in coronary CTOs.1,2 Article p 1101 Devices designed to cross CTOs should have 3 key features: an ability to distinguish a true luminal path from one created within (dissection) or through (perforation) the vessel wall of the occluded segment, an ability to change direction (steer) to correct deviations from the desired path through the occlusion, and an ability to penetrate the frequently fibrotic and focally calcific substance of the occlusion through the use of either mechanical stiffness or an alternative energy modality (laser, …

Assessing the prevalence, quantification and morphological composition of coronary atherosclerosis in patients with type 2 diabetes and the metabolic syndrome via 64-Slice CT angiography

Background: We determined the prevalence, morphology, and severity of coronary artery plaque in high-risk patients via 64-slice cardiovascular computed tomography (CVCT). Methods: Based on chart review, 101 subjects having a 64-slice CVCTwere assigned to one of three groups: type 2 diabetes, metabolic syndrome, or comparison. Disease severity was classified as:no disease, subclinical disease (lesions <70%), or clinically significant disease (lesions >70%). Plaque morphology wasstratified as either vulnerable or stable plaque by Houndsfield units and established American Heart Association criteria.Results: Diabetic subjects had the highest prevalence of CAD (78%), compared to 65% in the metabolic syndrome subjectsand 55% in the comparison group (p<.05). Diabetic subjects were also most likely to have both significant CAD (41%), andstable plaque (52%) followed by metabolic syndrome subjects (33% and 25%) and the comparison group (15% and 20%) (p< 0.05). The metabolic syndrome group was most likely to have vulnerable lesions (36%) potentially placing them atincreased risk of acute events. 22% of subjects in the diabetes group, 35% in the metabolic syndrome group, and 45% in thecomparison cohort were disease-free. Conclusions: 64-slice CVCT allows non-invasive diagnosis and stratification ofsubjects with diabetes and the metabolic syndrome, providing relevant information regarding coronary disease prevalence,severity, and plaque composition, that are statistically different among these high risk patient cohorts. (Int J Diabetes Metab14: 120-125, 2006)

Possible assessment of coronary plaque morphology before and after treatment with statin by multislice spiral computed tomographic coronary angiography—A case report

The case of a 58-year-old man with a previous anterior wall myocardial infarction and direct stenting who underwent multislice spiral computed tomographic (MSCT) coronary angiography with a row of 16 detectors before and after nine months of treatment with a statin is presented. MSCT coronary angiogram showed no significant stenosis in the left anterior descending (LAD) coronary artery, including the stented portion, and stress myocardial perfusion imaging showed that there was no ischemia. However, MSCT coronary images showed a lipid-rich plaque in the proximal portion of the stent implantation site in the LAD with a density of 17 Hounsfield units (HU) and with a size of 1.5 × 1.5 × 2.0 mm. MSCT coronary images obtained after nine months of treatment with pitavastatin showed that the plaque was smaller and had a density of 114 HU. MSCT coronary angiography allowed us to evaluate coronary artery plaque morphology before and after treatment with pitavastatin.

Impact of Renal Function on Coronary Plaque Morphology and Morphometry in Patients With Chronic Renal Insufficiency as Determined by Intravascular Ultrasound Volumetric Analysis

The aim of the present study was to use intravascular ultrasonography (IVUS) to assess plaque morphology and morphometry in patients with varying degrees of chronic renal insufficiency, including end-stage renal disease (ESRD) on dialysis replacement. Cardiovascular disease is the main cause of death for patients with chronic renal insufficiency, particularly in patients with ESRD. The impact of several degrees of renal insufficiency (including ESRD) on coronary plaque characteristics has not been determined. A total of 142 patients who underwent IVUS imaging of a de novo native coronary artery stenosis before percutaneous intervention were matched for age, gender, and diabetes and were grouped according to calculated creatinine clearance (CrCl): CrCl >70 ml/min (n = 39); CrCl 50 to 69 ml/min (n = 41); CrCl <50 ml/min, (n = 37), and ESRD (n = 25). Standard clinical, angiographic, and IVUS parameters were measured. The ESRD group had more African-American (p = 0.002) and hypertensive (p = 0.002) patients. No significant difference was found in any of the IVUS measurements among patients with CrCl >70, 50 to 69, and <50 ml/min: reference and lesion site arterial, lumen, and plaque areas and volumes, and arterial calcium (p = NS for all comparisons). Conversely, patients with ESRD had larger reference segment arterial and lumen areas and volumes; larger lesion site arterial, lumen, and plaque areas; and larger arcs of calcium (p <0.05 for all post hoc comparisons between patients with ESRD and patients with CrCl >70, 50 to 69, and <50 ml/min). Thus, chronic renal insufficiency in the absence of dialysis is not associated with increased reference segment or lesion site plaque burden and calcium. However, the transition to the need for dialysis is associated with progressive calcific atherosclerosis (larger lesion plaque area and calcium).

In vivo characterization of coronary atherosclerotic plaque by use of optical coherence tomography.

The current understanding of the pathophysiology of coronary artery disease is based largely on postmortem studies. Optical coherence tomography (OCT) is a high-resolution ( approximately 10 microm), catheter-based imaging modality capable of investigating detailed coronary plaque morphology in vivo. Patients undergoing cardiac catheterization were enrolled and categorized according to their clinical presentation: recent acute myocardial infarction (AMI), acute coronary syndromes (ACS) constituting non-ST-segment elevation AMI and unstable angina, or stable angina pectoris (SAP). OCT imaging was performed with a 3.2F catheter. Two observers independently analyzed the images using the previously validated criteria for plaque characterization. Of 69 patients enrolled, 57 patients (20 with AMI, 20 with ACS, and 17 with SAP) had analyzable images. In the AMI, ACS, and SAP groups, lipid-rich plaque (defined by lipid occupying > or =2 quadrants of the cross-sectional area) was observed in 90%, 75%, and 59%, respectively (P=0.09). The median value of the minimum thickness of the fibrous cap was 47.0, 53.8, and 102.6 microm, respectively (P=0.034). The frequency of thin-cap fibroatheroma (defined by lipid-rich plaque with cap thickness < or =65 microm) was 72% in the AMI group, 50% in the ACS group, and 20% in the SAP group (P=0.012). No procedure-related complications occurred. OCT is a safe and effective modality for characterizing coronary atherosclerotic plaques in vivo. Thin-cap fibroatheroma was more frequently observed in patients with AMI or ACS than SAP. This is the first study to compare detailed in vivo plaque morphology in patients with different clinical presentations.

Quantification of coronary hemodynamics and plaque morphology using X-ray angiography and intravascular ultrasound

While the mechanisms of plaque development in coronary arteries are not yet completely understood, vessel geometry and its influence on hemodynamics are of major importance. This manuscript presents an overview on our method for spatio-temporal modeling of the coronary arteries by fusion of data from X-ray angiography and intravascular ultrasound (IVUS) and elaborates on the aspects of 4-D computational hemodynamics as well as an approach to directly correlate vessel geometry with plaque morphology.

1084-175 Changes in coronary plaque color and morphology by lipid-lowering therapy with atorvastatin: Serial evaluation by coronary angioscopy

1084-175 Changes in coronary plaque color and morphology by lipid-lowering therapy with atorvastatin: Serial evaluation by coronary angioscopy

Coronary atherosclerotic disease burden: an emerging endpoint in progression/regression studies using intravascular ultrasound.

Coronary artery disease (CAD) represents the major cause of mortality in North America and Western Europe. Most acute coronary events, including myocardial infarction (MI) and sudden cardiac death, are initiated by the sudden rupture of mildly stenotic but vulnerable lesions and subsequent thrombosis. Recent results demonstrate a high prevalence of such plaques many years before clinical events occur. Because the event rate in asymptomatic patients, which would be candidate for primary prevention, is relatively low, pharmacological studies with the endpoint of MI and death require large study populations and long follow-up. Alternatively, the direct observation of coronary plaque burden and morphology with in vivo imaging modalities has been proposed as an endpoint in serial studies. This review will summarize the rational of this approach and describe the use of intravascular ultrasound (IVUS) for such studies.

Changes in coronary plaque color and morphology by lipid-lowering therapy with atorvastatin: serial evaluation by coronary angioscopy

ObjectivesChanges in coronary plaque color and morphology by statin therapy were evaluated using coronary angioscopy. BackgroundCoronary plaque stabilization by statin therapy has not been clarified in humans. MethodsThirty-one patients with coronary artery disease were divided into either the comparison group (n = 16) or the atorvastatin group (n = 15). Before treatment and 12 months after, the color and complexity of 145 coronary plaques were determined according to angioscopic findings. The yellow score of the plaque was defined as 0 (white), 1 (light yellow), 2 (yellow), or 3 (dark yellow), and its disrupted score was defined as 0 (smooth surface) or 1 (irregular surface) and as 0 (without thrombus) or 1 (with thrombus). In each patient, the mean yellow score and mean disrupted score were calculated. ResultsMean low-density lipoprotein cholesterol (LDL-C) decreased by 45% in the atorvastatin group, whereas an increase of 9% was seen in the comparison group. The mean yellow score decreased from 2.03 to 1.13 in the atorvastatin group, whereas it increased from 1.67 to 1.99 in the comparison group. There was a good correlation between the change in the mean yellow score and the change in LDL-C levels (r = 0.81, p < 0.0001). The change in the mean yellow score and mean disrupted score differed significantly between the two groups (p = 0.002 and p = 0.03, respectively). ConclusionsThis is the first report clarifying detailed changes in coronary plaque by statin in humans. This study indicated that lipid-lowering therapy changes plaque color and morphology and should then lead to coronary plaque stabilization.

Three methods for accurate quantification of plaque volume in coronary arteries.

The coronary atherosclerotic process evolves to an occlusive disease that causes chronic angina and acute coronary syndromes, such as myocardial infarction and sudden death. An important milestone in the understanding of the atherosclerotic process is the development of tools for quantitative assessment of disease progression or regression. A new methodology to analyze the coronary vessel lumen and plaque morphology in 3-D is based on the fusion of intravascular ultrasound (IVUS) and biplane X-ray angiography, which results in a geometrically correct representation of coronary vessels. A comparison of three volume quantification methods: polytope, Watanabe, and Simpson's rule is reported for quantifying the amount of plaque accumulation. The three methods allow local estimation of plaque volume. To determine volumetric indices, the space between the luminal and adventitial surfaces is first subdivided and then each of the volume elements is considered individually to achieve volume quantification. Polyhedral volume elements are employed and the volume of every element is estimated by each of the three approaches. The volume quantification methods were validated in 314 computer-generated shapes. All three methods are highly accurate, providing a mean error of 0.138 +/- 0.049%, 0.139 +/- 0.049%, and 0.832 +/- 0.203% for the polytope, Watanabe, and Simpson-rule methods, respectively. Nevertheless, the polytope and Watanabe methods are statistically significantly more accurate than the Simpson-rule approach (p < 0.001). The volumetric quantification methods were also tested using seven in vivo coronary arterial datasets from seven patients undergoing coronary angioplasty. While the polytope and Watanabe approaches are statistically significantly more accurate compared to the Simpson's rule method, accuracy of either of the tested method is sufficient for all practical purposes. Yet, the methods are not interchangeable and a single technique should be used in comparative volumetric studies.

Strain imaging with intravascular ultrasound array scanners: validation with phantom experiments.

Intravascular Ultrasound (IVUS) is routinely used in interventional cardiology for imaging coronary plaque morphology. However, the use of B-mode images for tissue characterization and detection of vulnerable coronary plaques is limited. Strain imaging with ultrasound is a new modality that provides additional information for tissue characterization by imaging differences in tissue stiffness. The aim is to differentiate between vulnerable (soft) plaques and less dangerous calcified (hard) plaques. In this work, the applicability of a time efficient strain imaging algorithm in conjunction with data from IVUS array transducers is evaluated. Unfocused radiofrequency (rf) data from the transducer array is acquired using custom made hardware. Rf line reconstruction is performed offline by synthetic aperture focusing techniques. Vessel mimicking phantoms of different geometries and material stiffness are made from agar and Polyvinyl Alcohol Cryogel (PVA). Experiments are conducted in a water tank and a water column is used for applying intraluminal pressure differences required for strain imaging. The results show that strain images can be calculated with A-lines reconstructed from unfocused rf raw data. Regions of different stiffness can be identified qualitatively by local strain variations. With the used algorithm strains of up to 2% can be imaged without significant decor-relation.

Accuracy of density measurements within plaques located in artificial coronary arteries by X-ray multislice CT: results of a phantom study.

Clinical studies indicate that coronary plaque morphology might be differentiated noninvasively using multislice CT by determining tissue density within the lesions. The aim of the present experimental study was to evaluate factors that influence density measurements within small vessels. A coronary phantom model was developed, consisting of silicon tubes (lumen diameter 4 mm) with two plaques of known density inside, simulating soft and intermediate lesions (Plaque 1: -39 HU; Plaque 2: 72 HU). Density measurement were conducted in three different contrast medium concentrations (1:30, 1:40, 1:50) and two different slice widths (4 x 2.5 mm, 4 x 1 mm). All scans were performed on a Somatom Volume Zoom (Siemens, Forchheim, Germany). Experimental results were compared with calculated data based on computer simulation. The two plaques could be clearly differentiated from each other on both collimations (4 x 2.5 mm: Plaque 1, 85 +/- 61 HU vs. Plaque 2, 119 +/- 26 HU, p < 0.0001; 4 x 1 mm: Plaque 1, 50 +/- 54 HU vs. Plaque 2, 91 +/- 17 HU, p < 0.0001). Significantly lower and more accurate results were achieved with 1.0 mm collimation (p < 0.0001). Contrast medium concentration contributed significantly to the measurements (p < 0.001). The experimental findings were confirmed by computer simulation, which revealed even more accurate results when using a 0.5 mm collimation (Plaque 1, 0.5 mm: -9 HU vs. 4 x 1 mm: 14 HU, Plaque 2, 4 x 0.5 mm: 83 HU vs. 4 x 1 mm: 93 HU). Density measurements were found to be highly dependent on slice width and surrounding contrast enhancement. Our results indicate that standardization of methodology is required before the noninvasive differentiation of human plaque morphology by multislice CT can be applied in the clinical setting as a screening test for coronary soft plaques.

Relation between plasma fibrinogen level and coronary plaque morphology in patients with stable angina pectoris

I vivo studies have demonstrated yellow plaque, as seen on angioscopy, to be common in the culprit lesions of acute coronary syndromes,1 and this plaque also has a predictive value for cardiac events in patients with stable angina pectoris.2 This suggests that yellow plaque is vulnerable and prone to rupture. Plaque rupture may be enhanced by the inflammatory process,3 which is considered to be involved in atherosclerotic vascular disease.4 The extent of coronary atherosclerosis proved by coronary angiography has been reported to be associated with plasma fibrinogen,5 which is an acute-phase protein, and its level changes during the inflammatory process. However, the relation between the intracoronary plaque morphology and plasma fibrinogen is less clear. We therefore examined this relation in patients with stable angina pectoris using percutaneous transluminal coronary angioscopy. • • • Eighty-three patients (71 men and 12 women; average age 57 6 7 years) with stable angina pectoris who had 1-vessel disease served as subjects in this study. They were selected from a pool of 186 consecutive patients with stable angina pectoris who underwent coronary angioscopy between May 1990 and October 1997 at our hospital. Of the 103 patients not included, 38 patients with prior myocardial infarction (onset of myocardial infarction ,3 months) were excluded because the inflammatory process of infarcted myocardium might have influenced the plasma fibrinogen level a few months after myocardial infarction. Twenty-five patients who underwent coronary angioplasty within 6 months were also excluded because recent angioplasty procedures could have influenced the color of the plaque. Twenty-one patients with multivessel disease were excluded because the intracoronary plaque characteristics of the other lesions, which were not observed by angioscopy, might have influenced the plasma fibrinogen. Thirteen patients were excluded because of an incomplete coaxial angioscopic view for color assessment, and 6 patients were excluded owing to disagreements regarding the classification of the lesion among at least 2 observers.

Impact of coronary plaque morphology as assessed by IVUS computer‐aided analysis on mechanisms of balloon angioplasty and stenting

This study was performed in order to quantitate structural coronary plaque modifications after balloon angioplasty and stenting and to evaluate the impact of plaque morphology on the mechanisms of lumen enlargement during angioplasty. Plaque morphology was studied by computer-aided analysis of 60 cross-sectional intravascular ultrasound (IVUS) images of the target lesion in 20 patients undergoing percutaneous coronary angioplasty. Based on a computer-aided video densitometry classification of plaque morphology, three groups of plaques were defined based on the slope value of a fifth polynomial regression of the plaque gray-level distribution. In groups A and B, balloon angioplasty provided significant increases in lumen area (P < 0.0001) and vessel area (P < 0.05) without a reduction in plaque area; neither parameter increased in group C. In group A, stenting was associated with an additional lumen enlargement (P < 0.0001) due to plaque reduction (P < 0.05). In groups B and C, stenting further increased lumen area (P < 0.0001) by improving vessel area (P < 0.001) but without plaque reduction. Balloon angioplasty and stenting provided a significant decrease in plaque area in group A as compared to groups B (P < 0.05) and C (P < 0.01). Finally, vessel area improvement was greater in group B than in groups A (P < 0.01) and C (P < 0.05). The mechanisms underlying lumen enlargement after coronary angioplasty are highly dependent on plaque morphology as defined by an IVUS computer-aided analysis and may differ between balloon angioplasty and stenting.

Sex differences in morphology of coronary artery plaque assessed by intravascular ultrasound

Results of autopsy studies have suggested that there are sex differences in morphology of coronary-artery plaques, but these differences have yet to be adequately evaluated in vivo. We performed preintervention intravascular ultrasound (IVUS) measurements on coronary plaques in a consecutive series of 76 men and 30 women with unstable angina pectoris. Both the target lesion and an adjacent reference site were evaluated. Arterial, plaque, and luminal areas were measured by planimetry. Plaques were classified as either calcified or uncalcified, and relative density of plaque was quantitatively assessed by videodensitometry, using a linear gray scale normalized with respect to density of adventitia. Although women were older than men (mean age 55.0 +/- 10.9 versus 60.4 +/- 12.2 years, P = 0.02), their target lesions were less dense (74.6 +/- 23.4 versus 86.2 +/- 22.2% of adventitial density, P = 0.02) and less often found to be calcified (20.0 versus 38.2%, P = 0.05). Similarly, reference sites in female subjects were less dense (77.6 +/- 15.3 versus 97.1 +/- 19.4% of adventitial density, P = 0.01). There was no sex difference in the severity of coronary stenosis. Both qualitative and quantitative sex differences in in-vivo morphology of coronary plaques morphology were detected by IVUS measurement. Plaques in women appear less videodense and are less often calcified than are those in men. Future studies employing sequential IVUS examinations are needed in order to determine whether these morphologic differences relate to a delay in initiation of plaques, slower progression of plaques, or other sex-specific modulators of plaque composition.

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 mm 2 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.