In vitro and in vivo intravascular ultrasound imaging.

This paper presents our experience with intravascular ultrasound imaging of animal and human arteries in vitro and in vivo using a high-frequency (20 M Hz) ultrasound transducer. In vitro, 32 human coronary artery segments were imaged with intravascular ultrasound and compared with corresponding histological sections. Ultrasound and histology measurements correlated significantly (P less than 0.0001) for coronary artery cross-sectional area (r = 0.94), lumen cross-sectional area (r = 0.85) and wall thickness (r = 0.92). In vivo, 19 sheep and eight human common femoral arteries were imaged and the angiographic lumen diameter of 14 animal and six human arteries was compared to the diameter of the corresponding ultrasound images. Significant correlations were found for lumen diameter in animals and humans (P less than 0.001, r = 0.91 and P less than 0.0001, r = 0.96, respectively). These studies demonstrate that this technique can provide high resolution images of arterial vessels and may have unique advantages in diagnosing atherosclerotic vascular disease and in catheter based therapies.     

Plaque characterization of atherosclerotic coronary arteries by intravascular ultrasound

Intravascular ultrasound provides cross-sectional images of arteries and enables accurate delineation of lumen dimensions and wall structure. Moreover, ultrasound characterization of atherosclerotic plaque subtypes may have important implications in determining the natural history and the clinical outcome of patients with coronary artery disease. The reliability of intravascular ultrasound to differentiate plaque morphology subtypes was studied in 60 coronary segments excised from 33 coronary arteries obtained from 17 patients at necropsy. Ultrasound was performed with a 25-MHz transducer mounted on the distal end of a rigid probe that was rotated manually inside the lumen artery. Plane film radiography was also performed to establish the presence of calcific deposits. A total of 82 histologic transverse sections corresponding to 82 ultrasound imaging sites were studied from the 60 coronary segments. Of the first 54 images, 36 were fibrous plaques and yielded dense homogenous echo reflections, 6 had discrete areas of lipid that were less echogenic and 12 had calcific deposits that cast echo-free shadows beyond areas of intense echo reflections. The predictive accuracy of evaluating plaque composition in the remaining 28 ultrasound imaging sites was 96%. Thus, anatomical structure of coronary arteries and composition of atherosclerotic lesions can be assessed accurately with intravascular ultrasound and may have potential for better understanding of the atherosclerotic process and provide guidance to interventional procedures.     

Intravascular ultrasound imaging of human coronary arteries in vivo. Analysis of tissue characterizations with comparison to in vitro histological specimens

BACKGROUND. Intravascular ultrasound imaging was performed in 27 patients after coronary balloon angioplasty to quantify the lumen and atheroma cross-sectional areas. METHODS AND RESULTS. A 20-MHz ultrasound catheter was inserted through a 1.6-mm plastic introducer sheath across the dilated area to obtain real-time images at 30 times/sec. The ultrasound images distinguished the lumen from atheroma, calcification, and the muscular media. The presence of dissection between the media and the atheroma was well visualized. These observations of tissue characterization were compared with an in vitro study of 20 human atherosclerotic artery segments that correlated the ultrasound images to histological preparations. The results indicate that high-quality intravascular ultrasound images under controlled in vitro conditions can provide accurate microanatomic information about the histological characteristics of atherosclerotic plaques. Similar quality cross-sectional ultrasound images were also obtained in human coronary arteries in vivo. Quantitative analysis of the ultrasound images from the clinical studies revealed that the mean cross-sectional lumen area after balloon angioplasty was 5.0 +/- 2.0 mm2. The mean residual atheroma area at the level of the prior dilatation was 8.7 +/- 3.4 mm2, which corresponded to 63% of the available arterial cross-sectional area. At the segments of the coronary artery that appeared angiographically normal, the ultrasound images demonstrated the presence of atheroma involving 4.7 +/- 3.2 mm2, which was a mean of 35 +/- 23% of the available area bounded by the media. CONCLUSIONS. Intravascular ultrasound appears to be more sensitive than angiography for demonstrating the presence and extent of atherosclerosis and arterial calcification. Intracoronary imaging after balloon angioplasty reveals that a significant amount of atheroma is still present, which may partly explain why the incidence of restenosis is high after percutaneous transluminal coronary angioplasty.     

Intravascular ultrasonic evidence by constant cross-sectional area of atherosclerotic plaques during coronary vasomotion in humans

AIMS: This study aims to visualize ultrasonically deformation of atheroscleroticplaques in human coronary arteries during vasoconstriction andvasodilatation. METHODS AND RESULTS: Intravascular ultrasound detected occult atherosclerosis inangiographically normal coronary arteries of eight patientswith chest pain at rest. During the acetylcholine provocativetest, intravascular ultrasound monitored deformation of theatherosclerotic plaques. At the last step of the test, intracoronaryinjection of isosorbide dinitrate caused vasodilation. Undercontrol, acetylcholine-treated, and isosorbide dinitrate-treatedconditions, cross-sectional areas of sonolucent circle and vessellumen were measured. Subtraction of the latter from the formergave the area of atherosclerotic plaque. In the process of vasoconstrictionand vasodilation, the plaque area did not change significantly. CONCLUSION: The cross-sectional area of the atherosclerotic plaque appearedto be constant during vasomotion of human coronary arteries.     

Validation of a novel wire-type intravascular ultrasound imaging catheter.

Intravascular ultrasound can be used to characterize atherosclerotic plaques in arteries. This report describes the results of in vitro experiments with a novel wire-type intravascular ultrasound-imaging catheter developed in our laboratory. The ultrasound catheter comprises a 30-MHz transducer mounted on the tip of a wire-type catheter. The outer diameter of the catheter at the distal acoustic site was 0.025". Dimensional measurements of arteries obtained at the time of autopsy were acquired by intravascular ultrasound and direct planimetry. The luminal CSA (cross-sectional area), vessel CSA, and intima-media thickness for arterial samples (n = 22) acquired by ultrasound images and histopathologic microsections correlated closely (r = 0.99, 0.97, and 0.99, respectively). The histopathologic lumen CSA, vessel CSA, and intima-media thickness were less than those of corresponding ultrasound images in 43 of 54 samples (80%), 43 of 54 samples (80%), and 62 of 62 samples (80%), respectively. Intraobserver and interobserver variances of the luminal CSA vessel CSA and intima-media thickness by ultrasound images were excellence. This novel wire-type intravascular imaging catheter provides accurate vessel measurements and plaque thickness. Furthermore, this intravascular imaging catheter can be used in coronary arteries to assess the morphology of small distal coronary arteries.     

Angiographically silent atherosclerosis detected by intravascular ultrasound in patients with familial hypercholesterolemia and familial combined hyperlipidemia: Correlation with high density lipoproteins

Objectives. This study sought to evaluate the extent of atherosclerosis in coronary and iliac arteries in patients with heterozygous familial hypercholesterolemia or familial combined hyperlipidemia, using intravascular ultraound imaging.

Background. Intravascular ultrasound imaging provides cross-sectional tomographic views of the vessel wall and allows quantitative assessment of atherosclerosis.

Methods. Forty-eight nonsmoking, asymptomatic patients with heterozygous familial hypercholesterolemia or familial combined hyperlipidemia underwent intravascular ultrasound imaging of the left anterior descending coronary, left main coronary and common iliac arteries. Angiography showed only minimal or no narrowing in these vessels. Intravascular ultrasound images obtained during catheter pullback underwent morphometric analysis. Plaque burden was expressed as the mean and maximal intimal index (ratio of plaque area and area within the internal elastic lamina) and as the percent of vessel surface covered by plaque.

Results. Intravascular ultrasound detected plaque more frequently than angiography in the left anterior descending (80% vs. 29%, respectively), left main (44% vs. 16%) and iliac arteries (33% vs. 27%). Plaque burden was higher in the left anterior descending (mean intimal index [±SD] 0.25 ± 0.16) than in the left main (0.11 ± 0.16, p < 0.001) and iliac arteries (0.02 ± 0.04, p < 0.001). Angiography detected lumen narrowing only in coronary arteries with a maximal intimal index 0.42 (left anterior descending artery) and 0.43 (left main artery). The area within the internal elastic lamina increased with plaque area in the left anterior descending (r = 0.82, p < 0.001) and left main arteries (r = 0.53, p < 0.001). By stepwise multiple regression analysis, the strongest predictor for plaque burden in the left anterior descending artery was the level of high density lipoprotein (HDL) cholesterol and total/HDL cholesterol ratio for the left main artery.

Conclusions. In patients with heterozygous familial hypercholesterolemia and familial combined hyperlipidemia, extensive coronary plaque is present despite minimal or no angiographic changes. Compensatory vessel enlargement and diffuse involvement with eccentric plaque may account for the lack of angiographic changes. Levels of HDL cholesterol and total/HDL cholesterol ratio are far more powerful predictors of coronary plaque burden than are low density lipoprotein cholesterol levels in these patients with early, asymptomatic disease.     

Comparison of measurement of cross-sectional coronary atherosclerotic plaque and vessel areas by 16-slice multidetector computed tomography versus intravascular ultrasound

In 26 patients, 16-slice multidetector computed tomography (MDCT) with 0.75-mm collimation and intravascular ultrasound (IVUS) of 1 coronary artery were performed. At 100 sites within the coronary arteries, the measurement of cross-sectional luminal area and, if detectable, the cross-sectional area of atherosclerotic plaque was performed independently with IVUS and MDCT. The mean luminal area (r = 0.92), measured at 100 sites, and plaque area (r = 0.55), measured at 65 sites, were significantly correlated (p <0.001) between MDCT and IVUS. The mean luminal area and mean plaque area were slightly but significantly overestimated with MDCT. MDCT permits the noninvasive measurement of coronary cross-sectional luminal and plaque areas with moderate accuracy.     

Intravascular ultrasound cross-sectional arterial imaging before and after balloon angioplasty in vitro

A prototype ultrasound imaging catheter was evaluated in vitro using 17 human atherosclerotic artery segments before and after balloon dilatation angioplasty. The catheter was 1.2 mm in diameter and incorporated a single 20-MHz ultrasound transducer to obtain cross-sectional images of the arterial lumen. In 15 of the 17 (88%) arteries, high quality images were obtained, which demonstrated clear demarcation between the lumen and the endothelium, the atheroma plaque, the muscular media, and the adventitia. Qualitative characteristics of plaque disruption, dissection, and residual flaps were readily visible. In addition, quantitative information about cross-sectional lumen area was obtained before and after balloon dilatation. The mean cross-sectional lumen area increased from 8.7 to 15.1 mm2 (p less than 0.01) following balloon dilatation. The lumen area measured from the ultrasound images following dilatation correlated closely with the area measured from histologic sections (r = 0.88). The results from this study indicate that a small-diameter ultrasound imaging catheter can be developed that will provide high-resolution qualitative and quantitative information during peripheral and coronary angioplasty.     

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.     

Comparison of intravascular ultrasound, external ultrasound and digital angiography for evaluation of peripheral artery dimensions and morphology

Validation of catheter-based intravascular ultrasound imaging has been based on comparisons with histology and digital angiography, each of which may have limitations in the assessment of arterial size and morphology. External, high-frequency ultrasound can accurately determine vessel dimensions and morphology and because, like ultravascular ultrasound, it also provides cross-sectional arterial ultrasound images, it may be a more appropriate technique for the in vivo comparison of arterial dimensions and morphology determined by intravascular ultrasound. Thus, intravascular ultrasound, external 2-dimensional ultrasound, Doppler color-flow imaging and digital angiography were compared for assessment of arterial dimensions and wall morphology at 29 femoral artery sites in 15 patients. Intravascular ultrasound and the other 3 imaging modalities correlated well in determination of lumen diameter (2-dimensional, r = 0.98, standard error of the estimate [SEE] = 0.14; Doppler color flow, r = 0.91, SEE = 1.11; angiography, r = 0.95, SEE = 0.91) and cross-sectional area (2-dimensional, r = 0.97, SEE = 0.04; Doppler color flow, r = 0.92, SEE = 0.14; angiography, r = 0.96, SEE = 0.08). However, lumen size measured by Doppler color flow was consistently smaller than that measured by the other 3 imaging modalities. Intravascular ultrasound detected arterial plaque at 15 sites, 5 of which were hypoechoic (soft) and 10 hyperechoic with distal shadowing (hard). Plaque was identified at 12 of 15 sites by Z-dimensional imaging (p = 0.30 vs intravascular ultrasound), but at only 6 of 15 sites by angiography (p = 0.003 vs intravascular ultrasound), only 1 of which was thought to be calcified plaque.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intravascular ultrasound imaging: in vivo peripheral and coronary artery studies

Recent in vitro studies have demonstrated that intravascular ultrasound can obtain high-resolution cross-sectional images of arterial vessels. To further expand the use of this technique for in vivo visualization of peripheral and coronary vessels, we imaged 24 femoral and 13 carotid arteries from 19 sheep. Using a manual rotation technique, high-resolution images were obtained in 95% of the vessel sites with a rigid probe and in 82% of the vessel sites with a flexible catheter. In 14 of these arteries, good correlation was found between the lumen diameter measured by ultrasound and by angiography (P less than .001, r = .91). In addition, 6 left circumflex coronary arteries were imaged from 6 additional sheep by motor-driven rotation of the ultrasound probe at 1,800 rotations per minute, obtaining clear delineation of coronary lumen morphology and lumen-intima interface. Strong correlation was found also between intravascular ultrasound and cineangiography for coronary artery diameter measurement (P less than .001, r = .96). These studies demonstrate that this technique can provide high-resolution images of arterial vessels in vivo and may have unique advantages in diagnosis of atherosclerotic vascular disease and in the guidance of new catheter-based therapeutic modalities.     

Intravascular ultrasound assessment of the renal artery

OBJECTIVE: To determine the feasibility and diagnostic value of catheter-based intravascular ultrasound imaging compared with angiography for visualizing renal artery structure. DESIGN: Renal artery images were obtained in patients with renal artery stenosis having percutaneous balloon angioplasty and in normal subjects by digital angiography and by a 20-MHz, mechanically driven, catheter-based, intravascular ultrasound imaging system. SETTING: A referral-based university hospital. PATIENTS: Four randomly selected normal subjects without known renal disease and four consecutive patients with known renal artery stenosis referred for percutaneous balloon angioplasty. INTERVENTIONS: Digital angiograms and intravascular ultrasound images of nine renal artery segments were obtained. In patients with renal artery stenosis, imaging was done before and after balloon angioplasty. MAIN RESULTS: Digital angiography and ultrasonography correlated closely in the determination of arterial lumen diameter (r = 0.81) and cross-sectional area (r = 0.83). However, ultrasonography provided structural information not shown by angiography. All normal arteries showed discrete intimal, medial, and adventitial wall layers by ultrasonography. In the five stenotic segments, angiography identified the cause of stenosis to be atherosclerosis in four patients and fibromuscular dysplasia in one patient. Ultrasound imaging, however, identified the disease process as atherosclerosis in three patients and as fibromuscular dysplasia in two patients. After renal angioplasty, ultrasonography identified three arterial dissections, only one of which was shown by angiography. CONCLUSIONS: These preliminary data indicate that catheter-based intravascular ultrasound imaging of the renal artery is feasible and correlates well with angiography in assessing renal artery size and also provides potentially important additional structural information that permits a better characterization of arterial pathology.     

Application of intravascular ultrasound for detection and quantitation of coronary atherosclerosis

Although angiography is widely utilized to assess the extent and severity of coronary artery disease (CAD), arteriography yields only a silhouette of the vessel lumen. Coronary intravascular ultrasound supplements angiography by providing a tomographic perspective of lumen geometry and vessel wall structure. Intracoronary ultrasound can now be performedin vivo utilizing small, flexible probes capable of negotiating tortuous vessles. We have performed coronary ultrasound in more than 100 patients, including a group of normal subjects, with no serious complications. Measurements of coronary lumen dimensions by angiography and ultrasound correlated closely for normal vessels (r=0.92) and for concentrically narrowed atherosclerotic vessels (r=0.90). However, the correlation between angiography and ultrasound was only fair for eccentrically narrowed arteries (r=0.79) and was poor following angioplasty (r=0.30). Coronary artery wall motion was measured by intravascular ultrasound and demonstrated significant differences between normal arteries (18% lumen area change) and atherosclerotic vessels (11% change). Coronary ultrasound demonstrated important differences in the structure of normal and altherosclerotic vessel walls. Arteries in normal subjects exhibited a thin intimal leading-edge echo (mean 0.20 mm) and subadjacent sonolucent zone (mean 0.12 mm). Atherosclerotic vessels typically demonstrated increased thickness of both structures and often exhibited dense fibrocalcific plaques that shadowed underlying anatomy. These ultrasound abnormalities were often present at angiographically normal sites. Several limitations of coronary intravascular ultrasound were apparent, including echo dropout, distortions produced by non-coaxial imaging, and inability to image small or severely narrowed vessels. Coronary intravascular ultrasound holds great promise for the detection and quantification of CAD in the clinical setting.     

Real-time intravascular ultrasound imaging in humans

The capability of obtaining cross-sectional, high resolution images of arteries with the use of ultrasound catheters has recently been demonstrated in animal studies. In this study the in vivo feasibility of intravascular ultrasound imaging in humans was evaluated. In 26 patients who had undergone diagnostic cardiac catheterization or iliofemoral arteriography, 1 of 3 different models of 20-MHz ultrasound catheters was advanced retrograde, into the iliac arteries and aorta or anterograde into the femoral arteries and real-time cross-sectional images of the arteries were obtained in all. In 10, the iliac arteries were normal and appeared circular and pulsatile with a 3-layered wall and crisply defined lumens. In 7 patients with nonobstructive plaques, the plaque was easily identified in the ultrasound image as a linear, bright, adynamic echo-dense structure. In 4 with obstructive disease in the iliac artery, the arterial lumen appeared irregular, bordered by a thickened, nonpulsatile wall. Variable grades of atheromatous abnormalities in the wall could be visualized. In all 5 patients with arteriographic evidence of obstructive disease of the femoral artery, intravascular ultrasound displayed reduced lumens and irregular borders with protruding high-intensity echoes in the wall. In all patients, the arterial lumen and the normal or abnormal wall were well visualized in the ultrasound images. There were no complications. This study thus demonstrates the feasibility of intravascular ultrasound imaging of arterial circulation in humans. With further improvements in catheter design and image quality, this imaging approach is likely to have a number of potential applications in the assessment of peripheral and coronary arterial diseases and in guiding interventional therapeutic procedures.     

Advancing age is associated with diminished vascular remodeling and impaired vasodilation in resistance coronary arteries

BACKGROUND: Compensatory enlargement of the coronary arterial wall has been described in the early stages of native atherosclerosis. However, little is known about the specific effect of aging on this adaptive process in atherosclerosis. The purpose of the current study was to characterize the effects of advancing age on vascular remodeling and endothelium-dependent and -independent coronary vasodilation in patients without coronary artery disease risk factors. METHODS: Twenty-six patients without coronary risk factors and with normal and mildly diseased coronary arteries were studied. Vessel, lumen and atherosclerotic plaque areas were evaluated by intravascular ultrasound and coronary flow response was assessed using papaverine and acetylcholine in the left anterior descending coronary artery. RESULTS: There was a weak but significant correlation between plaque area and age (r = 0.29, P<0.01). Vessel area was also weakly but significantly correlated with age (r = 0.22, P<0.05). However, lumen area had no correlation with age. Vessel area in the younger group (<50 years) and the older group (> or =50 years) increased 1.64 and 0.55 mm2 for every 1 mm2 increase in plaque area (r = 0.62, P<0.0001 and r = 0.39, P<0.05, respectively). With regard to vascular reactivity, there was an inverse correlation between the percentage increases in coronary blood flow (CBF) evoked by acetylcholine and aging (r = -0.49, P<0.05). The percentage increases in CBF evoked by papaverine also inversely correlated with aging (r=-0.53, P<0.01). However, the percentage changes in coronary artery diameter evoked with acetylcholine did not correlate with aging. CONCLUSION: This study suggests that endothelium-dependent and -independent vasodilation of the resistance coronary artery are impaired with advancing age, which may be in association with attenuated coronary vascular remodeling with aging.     

稳定型心绞痛患者与不稳定心绞痛患者冠状动脉血管内超声特点的比较

目的:通过对稳定型心绞痛（SAP）与不稳定心绞痛（UAP）患者冠状动脉血管内超声（IVUS）测定,进行斑块定性及定量分析,比较不同心绞痛患者冠状动脉斑块影像学特征性改变。方法:分别对37例SAP患者与34例UAP患者行冠状动脉造影及IVUS影像学检查;分析冠状动脉斑块性质,测定最小面积处外弹力膜面积（EEMA）、管腔横截面积、斑块面积（PA）、斑块负荷、重构指数等指标,并对各指标进行统计学分析。结果:UAP患者冠状动脉病变脂质斑块数明显多于SAP患者（P＜0.05）,而钙化斑块例数在两组间未见显著性差异;定量分析显示两组患者EEMA未见显著差异,而斑块负荷（PA/EEMA）的比较中两组间有显著性差异（P＜0.01）。UAP患者病变处倾向于表现为正性重构,而SAP患者多为负性重构。结论:SAP与UAP冠状动脉病变斑块性质及血管重构存在差异,IVUS能有效反映冠状动脉病变斑块特点。     

Invasive imaging of the coronary atherosclerotic plaque

Coronary atherosclerosis has a high prevalence and is known as the leading cause of death worldwide. Clinically, coronary atherosclerosis is routinely evaluated by coronary angiography, which provides a luminogram of the coronary artery and allows for recognizing lumen narrowing. However, angiography does not allow for the direct assessment of the disease process within the coronary vessel wall. Today, a number of catheter-based imaging methods can overcome this shortcoming and provide physicians with additional information on specific morphological components of atherosclerotic lesions. This article discusses the abilities of intravascular imaging techniques such as intravascular ultrasound (IVUS), IVUS-VH, iMAP, integrated backscatter-IVUS, intravascular optical coherence tomography, near-infrared spectroscopy and angioscopy, to diagnose coronary atherosclerosis and their potential to guide clinical decision making.     

Intravascular ultrasound assessment of arterial dissection, intimal flaps, and intraarterial thrombi

Arterial dissection, intimal tears, and intraluminal thrombosis are common sequelae of catheter-based interventional procedures for coronary artery disease. These may not be recognized reliably by contrast angiography. Intravascular ultrasound imaging is an innovative method that allows visualization of the cross-sectional anatomy with high-resolution real-time images. This article presents the recent experience in arterial imaging with this method. Studies documenting the ability of intravascular ultrasound to demonstrate arterial atherosclerosis and to unmask some problems related to atherosclerotic disease and its treatment by catheter-based maneuvers are presented. Problems of arterial dissection, intimal flaps, and intravascular thrombosis are described with in vitro and in vivo documentation of the capability of intravascular ultrasound to visualize these abnormalities. The clinical implications of real-time imaging of intimal flaps and intraluminal clots, and the possible value of this imaging modality in the performance of catheter-based therapeutic procedures for coronary and peripheral arterial disorders are discussed.