Calcified plaque cross-sectional area in human arteries: correlation between intravascular ultrasound and undecalcified histology

BACKGROUND: The purpose of this investigation was to quantify the amount of intralesional calcium detected by intravascular ultrasound (IVUS) compared with undecalcified histology in human arteries. This method preserves intralesional calcium and reduces sectioning artifacts, thereby providing an accurate measure of calcium plaque morphology. METHODS AND RESULTS: Ten arterial segments (5 coronary, 5 iliac) were obtained at autopsy. IVUS imaging was performed with a 4.9F catheter at an automated pullback rate of 1.0 mm/s. The undecalcified arteries were dehydrated in ascending alcohol and polymerized in glycol methylmethacrylate. The arteries were cut into 200-microm sections with an Isomet low-speed saw and stained with Goldner's trichrome. The lumen cross-sectional area, the calcium plaque cross-sectional area, the calcium plaque depth, length, and angle of arc of calcified plaque were measured from the IVUS images and histologic sections. In 24 selected cross sections, there were 38 separate calcium plaques. An independent observer correctly identified 34 of 38 calcified plaques for a sensitivity of 89% and specificity of 97%. The total mean calcified plaque cross-sectional area measured from histology was 4.6 +/- 4.1 mm2 compared with 2.8 +/- 2.3 mm2 by IVUS (P =.002). Plaque depth measured by histology was 1.2 +/- 0.4 mm versus 0.7 +/- 0.2 mm by IVUS (P =.001). The length of calcium plaques measured by histology was 3.6 +/- 1.78 mm versus 3.6 +/- 1.5 mm for IVUS (r = 0.79). CONCLUSIONS: IVUS accurately depicts circumferential calcified lesions with high sensitivity (89%) and specificity (97%). However, IVUS underestimates the total calcified plaque cross-sectional area by 39%. This is mainly because of the inability of the ultrasound to penetrate intralesional calcium, which leads to an underestimation of the depth of calcium by 45%.     

Atherosclerotic plaque characterization by 0.5-mm-slice multislice computed tomographic imaging.

BACKGROUND: It has been proposed that 0.5-mm-slice multislice computed tomography (MSCT) is a noninvasive tool for the detection of atherosclerotic plaque, but the validity of such an assessment has not been demonstrated by an invasive investigation. The present study was performed to compare the 0.5-mm-slice MSCT density of plaques with intravascular ultrasound (IVUS) findings. METHODS AND RESULTS: Atherosclerotic plaques were characterized in 37 consecutive patients undergoing percutaneous interventions. Based on the IVUS echogenecity, the plaques were classified as soft (n=18), fibrous (n=40) or calcified (n=40). In these 98 plaques, 0.5-mm-slice MSCT plaque density was calculated in 443 regions-of-interest, including 331 lesional foci and 112 luminal cross-sections, and represented as Hounsfield units (HU). MSCT density of the 3 types of plaque was 11+/-12 HU, 78+/-21 HU, and 516 +/-198 HU respectively. Computed tomography density of the (contrast-filled) lumen was 258+/-43 HU. There were statistically highly significant differences in the densitometric characteristics among the 4 groups (soft, fibrous, calcified plaque and lumen) by nonparametric Kruskal-Wallis test (p<0.0001). CONCLUSIONS: The IVUS-based coronary plaque configuration can be accurately identified by 0.5-mm slice MSCT. Noninvasive assessment of plaque characterization will ensure emphasis on the vessel wall beyond the vascular lumen.     

Coronary artery imaging with intravascular high-frequency ultrasound

Safe and effective clinical application of new interventional therapies may require more precise imaging of atherosclerotic coronary arteries. To determine the reliability of catheter-based intravascular ultrasound as an imaging modality, a miniaturized prototype ultrasound system (1-mm transducer; center frequency, 25 MHz) was used to acquire two-dimensional, cross-sectional images in 21 human coronary arteries from 13 patients studied at necropsy who had moderate-to-severe atherosclerosis. Fifty-four atherosclerotic sites imagined by ultrasound were compared with formalin-fixed and fresh histological sections of the coronary arteries with a digital video planimetry system. Ultrasound and histological measurements correlated significantly (all p less than 0.0001) for coronary artery cross-sectional area (r = 0.94), residual lumen cross-sectional area (r = 0.85), percent cross-sectional area (r = 0.84), and linear wall thickness (plaque and media) measured at 0 degrees, 90 degrees, 180 degrees, and 270 degrees (r = 0.92). Moreover, ultrasound accurately predicted histological plaque composition in 96% of cases. Anatomic features of the coronary arteries that were easily discernible were the lumen-plaque and media-adventitia interfaces, very bright echoes casting acoustic shadows in calcified plaques, bright and homogeneous echoes in fibrous plaques, and relatively echo-lucent images in lipid-filled lesions. These data indicate that intravascular ultrasound provides accurate image characterization of the artery lumen and wall geometry as well as the presence, distribution, and histological type of atherosclerotic plaque. Thus, ultrasound imaging appears to have great potential application for enhanced diagnosis of coronary atherosclerosis and may serve to guide new catheter-based techniques in the treatment of coronary artery disease.     

Validation of a three-dimensional intravascular ultrasound imaging technique to assess atherosclerotic burden: potential for improved assessment of cardiac allograft coronary artery disease

BACKGROUND: Serial analysis of intracoronary ultrasound images is limited by difficulty with spatial registration and inability to assess the full extent of vascular disease. Three-dimensional (3D) imaging of coronary arteries can potentially overcome these limitations. OBJECTIVES: To assess the feasibility of using a PC-based 3D rendering technique to assess atherosclerotic burden. METHODS: To define the accuracy of 3D intravascular ultrasound (IVUS) measurements in vitro, six porcine iliac arteries and nine human cadaveric iliac arteries were pressure fixed and imaged with a commercial IVUS system. 3D datasets of the arteries were constructed, and measurements were correlated with histomorphometry. In vivo studies of 53 arterial segments (19 right coronary, 26 anterior descending and eight circumflex) were scanned in 18 patients, one month to nine years post-transplantation and correlated to corresponding angiographic images for the presence of atherosclerosis. RESULTS: Porcine artery length and volume measurements by IVUS showed a high degree of correlation with histomorphometry measurements (r=0.99, P<0.0003 and r=0.99, P<0.0001, respectively). Human arterial length, total artery volume and lumen volume measurements were similarly correlated (r=0.99, P<0.0001, r=0.99, P<0.0001 and r=0.98, P<0.0001, respectively). For plaque volume, r=0.84, P<0.05. In vivo 3D IVUS scans demonstrated atherosclerotic lesions in nine of 18 patients, compared with five detected by angiography alone. CONCLUSIONS: 3D IVUS imaging allows rapid and accurate measurement of arterial length, volume and plaque dimensions in addition to lumenal area and can demonstrate the full extent of atherosclerotic pathology. Because of its superior reproducibility, this technique may be used to assess the progression of coronary artery disease and allow for more accurate evaluation of interventions aimed at preventing or retarding coronary artery disease.     

Intravascular ultrasound classification of atherosclerotic lesions according to American Heart Association recommendation

BACKGROUND: Intravascular ultrasound (IVUS) offers a new modality by which to image the vessel wall in high resolution. The aim of the study was to classify atherosclerotic lesions using IVUS according to American Heart Association (AHA) recommendation. METHODS: IVUS was performed using a 20 or 30 MHz mechanically rotated catheter in 190 patients (aged from 35 to 75 years, mean 59 +/- 9 years) who presented with suspicion of coronary artery disease based on clinical examination. RESULTS: Of the 190 patients, 49 (26%) (group A) were found to have normal or nearly normal coronary arteries, whereas the other 141 (74%) (group B) had significant angiographic stenosis (> 50% luminal narrowing). IVUS image interpretation was based on the recommendation of the Committee on Vascular Lesions of the Council on Atherosclerosis (AHA). In group A, a total of 822 segments were evaluated with IVUS; 444 (54%) were found to have plaque formation. Among these 444 segments, type II lesions were found in 145 (33%), type III lesions in 110 segments (25%), type IV and Va lesions in 169 segments (38%), and type Vb in 18 segments (4%). The severity of plaque area stenosis increased from type II to IV. In group B, only the most stenotic segments (n = 141) on angiography were selected for analysis. No significant differences were found among different lesion types with respect to the severity of plaque area stenosis. Type Vb and Vc lesions presented mainly, but not exclusively, as stable angina, whereas type VI lesions presented mainly as unstable angina. Some patients (12%) with stable angina had complicated lesions (type VIa-VIc). CONCLUSIONS: It is now possible to use intravascular ultrasound to classify atherosclerotic lesions according to the AHA recommendations that were based on histological examination. Standardized reports of IVUS can now be based on these recommendations. Even in angiographically normal coronary arteries, advanced atherosclerotic lesions are found, explaining the potential risk of acute coronary syndromes in this group of patients. In patients with angiographically severe coronary disease, clinical symptoms correlate mainly with plaque characteristics, rather than with the severity of stenosis.     

Intracoronary ultrasound evaluation of interventional technologies

The feasibility and applicability of intravascular ultrasound (IVUS) of the coronary arteries were evaluated in 65 patients undergoing 70 coronary interventional procedures. Morphologic and quantitative analyses were performed with a mechanically rotated IVUS catheter (4.8Fr, 20 MHz) and with orthogonal view cineangiography. A semiautomated edge-detection algorithm was used for cineangiographic quantification. Coronary interventions included 45 percutaneous transluminal coronary angioplasties, 9 excimer lasers, 11 directional coronary atherectomies, 3 rotational atherectomies and 2 stents. Most lesions consisted of a mixture of plaque composition (hard, n = 30; soft, n = 64). Other unique morphologic data by IVUS were plaque topography (eccentric, n = 34; concentric, n = 36) and vessel dissection (IVUS [n = 29] versus angiography [n = 14], p less than 0.05). Postprocedure minimal lumen diameter and cross-sectional area measured by IVUS were larger and poorly correlated with angiography (r = 0.28, standard error of the estimate = 0.52 mm; r = 0.08, standard error of the estimate = 1.0 cm2, respectively). IVUS is more sensitive than angiography when assessing postintervention lesion characteristics including vessel dissection and plaque morphology. Catheter-based ultrasound appears to be a useful adjunct to contrast angiography when evaluating and comparing the therapeutic impact of conventional percutaneous transluminal coronary angioplasty with new technologies.     

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: questions and answers.

Coronary angiography is the gold standard for the detection of coronary artery disease, but it only gives information about the lumen of the coronary arteries. Intravascular ultrasound (IVUS) has provided a new perspective for imaging the coronary arteries. It allows assessment of not only the lumen but also the vessel wall and atherosclerotic plaque. In this article, we review the technique, measurements and current applications of IVUS imaging of the coronaries in a question-answer format.     

中重度冠状动脉钙化对介入治疗即刻疗效的影响

目的观察中重度冠状动脉钙化对冠状动脉介入治疗即刻疗效的影响。方法连续收集84例冠心病患者(84处靶病变),在冠状动脉支架置入术前后,通过血管内超声分析冠状动脉斑块特征、评估支架置入情况,并收集临床资料及介入操作相关信息,根据结果分为无钙化组36例和中重度钙化组48例,所有钙化病变均给予充分预扩张,并在血管内超声指导下视情况给予后扩张处理,对比2组PCI前后临床及影像学特征。结果 PCI后中重度钙化组置入支架直径、术后最小支架直径、最小支架横截面积、即刻管腔获得及相对管腔获得均小于无钙化组(P<0.05),PCI前中重度钙化组单支病变、靶病变B1型、斑块偏心指数、远端参考外弹力膜面积及管腔面积小于无钙化组(P<0.05,P<0.01)。而2组支架对称性、膨胀指数、手术并发症、院内主要不良心血管事件发生率比较,差异无统计学意义(P>0.05);2组术前最小管腔截面积、斑块负荷、管腔面积狭窄率、重构指数、病变长度差异无统计学意义(P>0.05)。结论血管内超声指导下给予充分预扩张及非顺应性高压球囊后扩张处理后,中重度钙化仍然影响PCI术后即刻管腔获得,但最终管腔面积基本理想。     

Validation of Automated Border Detection in Intravascular Ultrasound Images

Intravascular ultrasound (IVUS) imaging provides cross-sectional views of the vessel lumen; however, lumen measurements still rely on operator-dependent border delineation and time-consuming lumen tracings. We tested a new system for automated lumen border detection in IVUS images based on acoustic quantification of blood and vessel wall. In 10 rabbits, 29 segments of the aorta were imaged in vivo using a 2.9-Fr IVUS catheter. IVUS images were obtained during motorized pullbacks of aortic segments of 18 mm length. Automated measurements of lumen dimensions were compared to automated measurements of a second pullback through the same segment, lumen measurements derived from visual border tracings in IVUS images, and to quantitative angiography. The automated system showed good reproducibility: Correlations for repeated measurements of lumen area, maximal and minimal lumen diameters were r = 0.97, r = 0.91, and r = 0.93, respectively. Automated measurements also correlated well to visual image analysis (lumen area, r = 0.97; maximal lumen diameter, r = 0.89; minimal lumen diameter, r = 0.89) and to angiographic measurements (lumen area, r = 0.93; lumen diameter, r = 0.95). In 12% of the images, the automated system overestimated lumen dimensions because of weak wall signals in the presence of echolucent structures next to the wall. Signal artifacts from the IVUS catheter itself or strong blood backscatter resulted in lumen underestimation in 6% of the images. Over-and underestimation of lumen by the border detection system were often associated with eccentric catheter position. Thus, lumen measurements in vivo IVUS images can be performed using an automated border detection system based on acoustic quantification of blood and vessel wall. The system allows reproducible and accurate measurements of lumen area and diameters.     

Intravascular ultrasound imaging of angiographically normal coronary arteries: a prospective study in vivo.

Intravascular ultrasound imaging (IVUS) was performed to elucidate the discrepancy between clinical history and angiographic findings and to measure the diameter and area of the lumen of the normal left coronary artery in 55 patients who presented with chest pain but had normal coronary angiograms. The left coronary artery (LCA) was scanned with a 4.8F, 20 MHz mechanically rotated ultrasound catheter at 413 sites. Atherosclerotic lesions were identified at 72 (17%) sites in 25 patients. The mean (SD) (range) plaque area was 5.55 (3.56) mm2 (2-26 mm2) and it occupied 28.8 (9.6)% (13-70%) of the coronary cross sectional area. Calcification was detected at 24 (33%) atherosclerotic sites in nine patients. The correlation coefficients for the lumen dimensions measured at normal sites by IVUS and by angiography were r = 0.93 (SEE = 0.43) mm for lumen diameter and r = 0.89 (SEE = 4.27) mm2 for lumen area (both p < 0.001). 16 of the 30 patients in whom no atherosclerotic plaques were detected in the LCA lumen by IVUS had no risk factors of coronary artery disease. The cross sectional area of 90 consecutive images of left main coronary artery (LMCA), proximal left anterior descending coronary artery (proximal LAD), and mid LAD was measured in these 16 subjects. The mean (SEM) areas at end diastole were LMCA 17.33 (7.98) mm2; proximal LAD 13.56 (5.85) mm2; mid LAD 9.75 (4.67) mm2. During the cardiac cycle the cross sectional area changed by 10.2 (4.0)% in the LMCA, by 8.3 (4.7)% in the proximal LAD, and by 9.8 (4.0)% in the mid LAD. In 11 patients with plagues the change in cross sectional area in plague segments (5.8(3.1)%) was significantly lower than in the segments from patients without plagues (p < 0.001). Lumen area reached a maximum in early diastole rather than in late diastole. IVUS can imagine atherosclerotic lesions that are angiographically silent; it also provides detailed information about plague characteristics. The variation in coronary cross sectional area during the cardiac cycle should not be ignored during quantitative analysis. Maximum dimensions in normal segments are reached in early diastole. Further studies are needed to clarify the clinical significance of atherosclerosis detected by IVUS in patients presenting with chest pain but normal coronary angiography.     

Accuracy of nonstenotic coronary atherosclerosis assessment by multi-detector computed tomography.

BACKGROUND: The ability to evaluate coronary stenosis using multi-detector computed tomography (MDCT) has been well discussed. In contrast, several studies demonstrated that the plaque burden measured by intravascular ultrasound (IVUS) has a relationship to the risk of cardiovascular events. the accuracy of MDCT was studied to determine plaque and vessel size compared with IVUS. METHODS AND RESULTS: Fifty-six proximal lesions (American College of Cardiology/American Heart Association classification: segment 1, 5, 6) from 33 patients were assessed using MDCT and IVUS. The plaque and vessel area were measured from the cross-sectional image using both MDCT and IVUS. Eight coronary artery lesions with motion artifacts and heavily calcified plaques were excluded from the analysis. The vessel and lumen size evaluated using MDCT were closely correlated with those evaluated by IVUS (R(2)=0.614, 0.750 respectively). Furthermore, there was a strong correlation between percentage plaque area assessed by MDCT and IVUS (R(2)=0.824). CONCLUSION: MDCT can noninvasively quantify coronary atherosclerotic plaque with good correlation compared with IVUS in patients with atherosclerosis.     

Mechanisms of acute gain and late lumen loss after atherectomy in different preintervention arterial remodeling patterns

The main mechanism of restenosis after directional coronary atherectomy (DCA) remains obscure. We investigated mechanisms of restenosis after DCA in different coronary artery remodeling patterns. DCA was performed in 51 de novo lesions. The lesions were evaluated by intravascular ultrasound (IVUS) before, immediately after, and 6 months after the procedure. According to the IVUS findings before DCA, we classified the lesions into the following 3 groups: (1) positive (n = 10), (2) intermediate (n = 25), and (3) negative (n = 16) remodeling. We measured lumen area, vessel area, and plaque area using IVUS before DCA, immediately after DCA, and at follow-up. Lumen area increase after DCA was mainly due to plaque area reduction in the positive and intermediate remodeling groups (90 plus minus 15% and 80 plus minus 25% increase in lumen area, respectively), whereas that in the negative remodeling group was due to both plaque area reduction (57 plus minus 22% increase in lumen area) and vessel area enlargement (43 plus minus 33% increase in lumen area). The plaque area increase correlated strongly with late lumen area loss in the positive and intermediate remodeling groups (r = 0.884, p <0.001; r = 0.626, p <0.001, respectively), but the decrease in vessel area was not correlated with lumen area loss. In contrast, both an increase in plaque area and a decrease in vessel area were correlated with late lumen area loss (r = 0.632, p = 0.009; r = 0.515, p = 0.041) in the negative remodeling group. Coronary artery restenosis after atherectomy was primarily due to an increase in plaque in the positive and/or intermediate remodeling groups. However, in the negative remodeling group, late lumen loss might have been caused by both an increase in plaque and vessel shrinkage.     

Successful Directional Atherectomy of De Novo Coronary Lesions Assessed With Three-Dimensional Intravascular Ultrasound and Angiographic Follow-Up

Recent histopathologic and intravascular ultrasound (IVUS) data indicate that inadequate compensatory enlargement of atherosclerotic lesions contributes to the development of significant arterial stenoses. Such lesions may contain less plaque, which may have implications for atheroablative interventions. In this study, we compared lesions with (group A, n = 16) and without inadequate compensatory enlargement (group B, n = 30) as determined by IVUS. The acute results and the follow-up lumen dimensions of angiographically successful directional coronary atherectomy procedures were compared. Inadequate compensatory enlargement was considered present when the preintervention arterial cross-sectional area at the target lesion site was smaller than that at the (distal) reference site. Three-dimensional IVUS analysis and quantitative angiography were performed in 46 patients before and after intervention. IVUS measurements included the arterial, lumen, and plaque (arterial minus lumen) cross-sectional areas at the target lesion site (i.e., smallest lumen site) and the (distal) reference site. Angiographic follow-up was performed in 42 patients. Preintervention and postintervention angiographic measurements and IVUS lumen cross-sectional area measurements were similar in both groups. However, at follow-up, the angiographic minimum lumen and reference diameters were significantly smaller in group A compared with group B (1.71 ± 0.47 mm vs 2.14 ± 0.73 mm, p <0.03, and 2.97 ± 0.29 mm vs 3.39 ± 0.76 mm, p <0.02; group A vs B). The data of this observational study suggest that lesions with inadequate compensatory enlargement, as determined by IVUS before intervention, may have less favorable long-term lumen dimensions after directional coronary atherectomy procedures.     

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

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

Intravascular ultrasound evaluation of the effect of rotational atherectomy in obstructive atherosclerotic coronary artery disease.

BACKGROUND. High-speed rotational atherectomy uses a diamond-coated, elliptical burr to abrade occlusive atherosclerosis, especially noncompliant calcified plaque. METHODS AND RESULTS. Intravascular ultrasound (IVUS) was used to analyze 28 patients after atherectomy. Arteries treated and imaged were left main (three), left anterior descending (12), left circumflex (five), right coronary (seven), and saphenous vein graft (one). Twenty patients had adjunct balloon angioplasty. Twenty-two (79%) target lesions were calcified; the intimal arc of calcium was 160 +/- 126 degrees (range, 0-360 degrees). After atherectomy, the intima-lumen interface was unusually distinct and circular. The lumen was larger than the largest burr used for both stand-alone (1.19 +/- 0.19-fold the largest burr size) and adjunct balloon procedures (1.30 +/- 0.15-fold the largest burr). Three-dimensional reconstruction of the ultrasound images showed a smooth lumen, especially in calcified plaque. Deviations from cylindrical geometry occurred only in areas of soft plaque or superficial tissue disruption of calcified plaque. Five patients were studied before and after rotational atherectomy. IVUS showed an increase in lumen size, a decrease in plaque-plus-media area and in arc of target lesion calcification, and no change in target lesion external elastic membrane cross-sectional area. CONCLUSIONS. Rotational atherectomy causes atheroablation with only moderate evidence of barotrauma in heavily calcified arteries, even after adjunct balloon angioplasty. The lumen is cylindrical, especially in areas of calcified plaque, and somewhat larger than the largest burr tip used.     

Pathologic validation of a new method to quantify coronary calcific deposits in vivo using intravascular ultrasound

Current methods of calcium quantification by intravascular ultrasound (IVUS) measure the arc of calcium using the cross-sectional image at the lesion and at the reference site while neglecting calcium elsewhere. Calcium at these sites may not adequately represent the extent of total epicardial coronary calcium. We devised a new method to quantify calcium as a percentage of the coronary luminal surface. This study examines whether this new method accurately reflects coronary calcium determined by histology. Seventeen postmortem coronary arteries were pressure-fixed and imaged by IVUS using a motorized pullback device. Total plaque-luminal circumferential length and calcified plaque-luminal circumferential length were measured from serial cross-sectional IVUS images every 1 mm. With use of Simpson's method, the total plaque and calcified plaque surface area was then calculated. Histologic sections were stained with hematoxylin-eosin and Movat pentachrome at 3-mm intervals. Calcium was independently quantified by planimetry under light microscopy. Histologic analysis (n = 253 sections) revealed a wide range of calcium (0 to 47 mm2; mean 12 +/- 16 mm3). The IVUS-derived calcified plaque surface area was 17 +/- 23 mm2), which represented 3.1 +/- 4.1% (range 0% to 13.9%) of the total plaque surface area. The histologic and IVUS quantification of calcium by this method was strongly related (r = 0.84, p <0.0001), which was an improvement over current 2-dimensional measures of calcium arc (r = 0.41, p = 0.18). Calculation of calcified plaque surface area from sequential IVUS images appears to accurately reflect the degree of total coronary calcification.     

Comparison of ruptured plaques in native coronary arteries and in saphenous vein grafts: an intravascular ultrasound study

Intravascular ultrasound (IVUS) has been used to describe ruptured plaques in saphenous vein grafts (SVGs) and native coronary arteries. We compared clinical, angiographic, and IVUS features of ruptured atherosclerotic plaques in SVGs and native coronary arteries. We identified 95 plaque ruptures in 76 SVGs in 73 patients. These lesions and patients were matched with 95 lesions and patients from a database of 468 native artery ruptures. The matching criterion was IVUS mean reference lumen area. Patients with ruptured SVG plaques were older (68.4 +/- 10.1 vs 65.0 +/- 10.6 years, p = 0.021), more often had hypercholesterolemia (92% vs 74%, p = 0.015) and hypertension (78% vs 62%, p = 0.059), and more often had a history of a remote myocardial infarction (57% vs 32%, p = 0.002). In contrast, anginal symptoms were similar in the 2 groups (70% to 75% of each group had an acute coronary syndrome). Most (90% to 95%) ruptured plaques in each group were classified as angiographically complex. However, ruptured SVG lesions more often had an angiographically visible intimal flap (71% vs 38%, p <0.001). More than 70% of lesions in the 2 groups had positive arterial remodeling by IVUS, but there was a tendency for a higher remodeling index in ruptured plaque SVG lesions (1.18 +/- 0.30 vs 1.11 +/- 0.20, p = 0.085). The site of the initial tear occurred mainly (in approximately 70%) at the plaque shoulders in the 2 groups. In conclusion, although patients with SVG plaque ruptures are older and have more co-morbidities, the clinical presentation and angiographic and IVUS features are remarkably similar to those of native artery plaque ruptures.     

Characterization of non-calcified coronary atherosclerotic plaque by multi-detector row CT: comparison to IVUS

Multi-detector row Computed Tomography (MDCT) permits non-invasive visualization of the coronary arteries. The ability to visualize and, with limitations, to characterize non-calcified coronary atherosclerotic plaque has been described. We investigated the CT attenuation of non-calcified plaques as determined by 16-slice MDCT in comparison to intravascular ultrasound (IVUS). METHODS AND RESULTS: Thirty-two patients were investigated by contrast-enhanced 16-slice CT. In addition, IVUS of one coronary artery (motorized pullback) was performed (LM+LAD: 22, LM+LCX: 4, RCA: 6). At 252 sites within the coronary system, in which non-calcified atherosclerotic plaque could be identified both in MDCT and IVUS, the CT attenuation within the plaque was measured using a centrally placed region of interest and correlated to the appearance of the plaque in IVUS at the corresponding location. The mean CT attenuation within plaque that corresponded to hyper-echogenic appearance in IVUS was 121+/-34HU (n=76). The mean CT attenuation within plaque that corresponded to hypo-echogenic appearance was 58+/-43HU (n=176, p<0.001). However, there was substantial overlap of the density values measured by MDCT in the two groups. CONCLUSIONS: A significant difference of the mean CT attenuation within atherosclerotic lesions of hypo-echogenic and hyper-echogenic appearance in IVUS could be observed. However, we observed substantial overlap of attenuation values between plaque types so that the differentiation of "vulnerable" and "stable" plaques based on their CT attenuation is doubtful.     

Low variation and high reproducibility in plaque volume with intravascular ultrasound

BACKGROUND: Intravascular ultrasound (IVUS) has several advantages compared to angiography when evaluating coronary atherosclerosis in the vessel wall. METHODS: The accuracy, reproducibility, and short-time spontaneous variation in volume of vessel, plaque and lumen were studied by electrocardiographic-gated three-dimensional (3D) IVUS in 20 male patients with ischaemic heart disease (IHD). RESULTS: The study lesions were angiographically insignificant, with a length of the analysed segment on 11.4+/-5.9 mm. At baseline the mean minimal lumen diameter was 2.41+/-0.59 mm, minimal lumen area 4.82+/-2.38 mm2, and maximal plaque burden 65.61+/-9.57%. Mean reference diameter was 3.1+/-0.6 mm. No significant changes were observed in volumes of total vessel, lumen or plaque. The coefficient of variation (CV) for two volume measurements at baseline was: vessel 0.8%, plaque 1.3%, and lumen 1.4%. For measurements recorded at baseline and after 12.6+/-1.5 weeks, CV was respectively 3.5%, 3.3% and 6.6%. Reproducibility and interobserver and intraobserver variation showed very high correlations. A linear correlation was present in percent changes over 12.6+/-1.5 weeks between vessel volume and lumen volume (r=0.804; p<0.001) and between percent changes in plaque volume and vessel volume (r=0.581; p=0.007). No correlation was found between changes in plaque volume and lumen volume (r=0.015; p=0.950). CONCLUSION: ECG-gated 3D IVUS is a highly reproducible method when applied on coronary artery atherosclerosis. CV for lumen volume over 12.6+/-1.5 weeks is twice that of plaque volume indicating the superiority of the 3D IVUS compared to coronary angiography (CAG).