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.     

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)     

Greater late lumen loss after successful coronary balloon angioplasty in the proximal left anterior descending coronary artery is not explained by extent of vessel wall damage or plaque burden

OBJECTIVES: We investigated whether the greater late lumen loss after coronary balloon angioplasty in the proximal left anterior descending artery (P-LAD) compared with that in other segments might be related to differences in vascular dimensions or morphology as determined by angiography and intravascular ultrasound imaging. BACKGROUND: The greater late lumen loss after angioplasty in the P-LAD that has been observed in several studies has not been explained. METHODS: We studied 178 patients and 194 coronary artery lesions by quantitative angiography and 30 MHz intravascular ultrasound imaging after successful balloon angioplasty. Vessel wall morphology was compared among three proximal and three nonproximal segments. Follow-up quantitative angiography for late lumen loss calculation was performed in 168 lesions. Multivariate analysis was used to determine predictors of late lumen loss. RESULTS: Absolute and relative late loss were significantly greater at the P-LAD compared with the pooled group of other segments (0.42 +/- 0.60 mm vs. 0.10 +/- 0.48 mm, p = 0.0008 and 0.14 +/- 0.24 vs. 0.03 +/- 0.17, p < 0.001). Also, a greater percentage of calcific lesions (65% vs. 44%, p = 0.034), a lower incidence of rupture (51% vs. 74%, p = 0.009) and a larger reference segment plaque area (5.4 +/- 2.2 mm2 vs. 4.7 +/- 1.9 mm2, p = 0.05) were found in the P-LAD. In multivariate analysis however, these variables were not predictive of late loss. CONCLUSIONS: Greater late lumen loss after coronary balloon angioplasty of the P-LAD is not explained by differences in atherosclerotic plaque burden or in vessel wall damage.     

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.     

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 ultrasound imaging of saphenous vein grafts in vitro: comparison with histologic and quantitative angiographic findings.

The ubiquity of coronary artery disease and the resultant widespread use of saphenous veins for coronary artery bypass surgery has stimulated considerable interest in the morphologic and pathophysiologic alterations these vessels undergo after implantation. This study was undertaken to determine the ability of intravascular ultrasound to identify and characterize abnormalities in saphenous vein grafts. Ten saphenous vein grafts excised at autopsy and nine saphenous vein segments harvested during coronary artery bypass surgery were examined with intravascular ultrasound imaging, quantitative coronary angiographic techniques and histologic analysis. Intravascular ultrasound lumen measurements were strongly correlated with quantitative coronary arteriographic measurements (r 0.91, SEE 0.5 mm). Wall thickness was significantly greater in the vein grafts after long-term implantation than in the freshly harvested veins (average thickness 1.4 +/- 0.5 vs. 0.7 +/- 0.2 mm, p less than 0.007); this finding correlated histologically with vein wall fibrosis. There was good correlation between ultrasound imaging and histologic analysis, with the ability to distinguish among normal intima, intimal hyperplasia, vein wall fibrosis and atheromatous plaque. Thus, this preliminary study demonstrates the ability of intravascular ultrasound to provide real-time cross-sectional images of saphenous veins and morphologic characterization of their walls. This modality may have important clinical applications, including the ability to detect serial changes in vein graft intimal hyperplasia and atherosclerosis.     

Quantitative assessment of peripheral and coronary artery lesions before and after balloon angioplasty: A comparison of intravascular ultrasound and angiography

Summary Intravascular ultrasound and conventional angiography were used to determine the degree of stenosis before and after angioplasty in 25 consecutive patients with peripheral arterial occlusive disease and 15 selected patients with coronary artery disease. Angiographic determinations of the luminal area and percent stenosis were made with the help of an automatic detection system, and the same parameters were evaluated planimetrically in the ultrasound studies. Following angioplasty of peripheral lesions, angiography demonstrated a significantly greater increase in mean luminal area (10.8 ± 7.8mm² vs 5.8 ± 4.0 mm²;P < 0.05) and a greater reduction in degree of stenosis (26% ± 16%vs 14% ± 11%;P < 0.05) than did the ultrasonic investigation. There was a significant but moderate correlation between values for the luminal area determined by angiography and ultrasound before angioplasty (r = 0.75; SEE = 4.8mm²) and in normal proximal segments of coronary arteries (r = 0.79; SEE 4.1 mm²). Following angioplasty there was no significant correlation between angiographic findings and those determined by intravascular ultrasound in peripheral or coronary lesions. These results suggest that angiography and intravascular ultrasound are fundamentally different imaging and analysis techniques. Following angioplasty, conventional angiography rarely demonstrated dissection or intraluminal filling defects, while intravascular ultrasound detected plaque rupture and the presence of intraluminal atheroma in almost all cases. Quantitative determinations of luminal area and degree of stenosis rely on indirect measures with conventional angiography, while these parameters are determined directly by intravascular ultrasound. Additional studies and clinical experience should demonstrate whether intravascular ultrasound will play a significant role in the planning and management of vascular interventions.Presented in part at the 1993 European Congress of Cardiology in Nice, France.     

In vitro validation of three-dimensional intravascular ultrasound for the evaluation of arterial injury after balloon angioplasty.

OBJECTIVES. The hypothesis of this study was that three-dimensional ultrasound imaging would facilitate the evaluation of arterial dissection after balloon angioplasty. BACKGROUND. The presence and extent of arterial dissection occurring at the time of balloon angioplasty may be important predictors of abrupt vessel closure or late restenosis. METHODS. Forty-one human arterial segments obtained after death were imaged in an in vitro system at physiologic pressure (80 to 100 mm Hg) before and after balloon angioplasty. Images were acquired with a 20- to 30-MHz mechanical intravascular ultrasound imaging system (Cardiovascular Imaging Systems) with a constant pullback technique (1 mm/s). Standard 0.5-in. (1.27-cm) video tapes were used for data storage and later playback for analog to digital conversion. Digitized data were reconstructed to three-dimensional images with use of voxel space modeling. The vessels were opened longitudinally and subjected to pathologic examination, photographed and classified histologically as normal, fibrous or calcified. Dissection was defined as a disruption and separation of components of the arterial wall. The length and depth of arterial dissection were evaluated grossly and microscopically. RESULTS. Of the 41 arteries studied, 36 (88%) exhibited dissection on pathologic examination after balloon angioplasty. Three-dimensional reconstruction of intravascular ultrasound images identified dissection in 11 (92%) of 12 normal, 8 (100%) of 8 fibrous and 11 (69%) of 16 calcified arteries. Excellent agreement between ultrasound and pathologic findings was achieved in the evaluation of length and depth of dissection for histologically normal and fibrous arteries (kappa = 0.72 to 1.0). When the vessels were severely calcified, the agreement was not as good (kappa = 0.27 to 0.56), particularly in detection of small, non-raised intimal flaps. CONCLUSIONS. This histopathologic validation study suggests that three-dimensional intravascular ultrasound imaging facilitates the evaluation of both quantitative and morphologic features of arterial dissection induced by balloon angioplasty. The advantage of three-dimensional intravascular ultrasound is its ability to assess the length and morphology of arterial injury over an entire vessel segment.     

Intravascular ultrasonography versus digital subtraction angiography: a human in vivo comparison of vessel size and morphology

The accuracy of catheter-based intravascular ultrasonography to define luminal size in humans in vivo and its sensitivity to describe lesion morphology have not been previously reported. Vessel diameter, cross-sectional area and lesion characteristics assessed by digital subtraction angiography and intravascular ultrasonography (20 MHz) were compared in 86 human arterial segments. The same arterial segments were imaged and analyzed by digital subtraction angiography and intravascular ultrasonography at 49 femoral, 3 renal, 5 iliac, 7 pulmonary and 22 aortic sites. Digital subtraction angiographic diameter and area were determined geometrically by an automated algorithm. Intravascular ultrasonographic diameter and area were determined by planimetry. Linear correlation for diameter by the two techniques was 0.97, standard error of the estimate (SEE) = 1.83 mm, and for cross-sectional area it was 0.95, SEE = 0.65 cm2. Intravascular ultrasonography identified 24 sites in which plaque was present; 11 (46%) of these segments appeared normal by digital subtraction angiography. Conversely, digital subtraction angiography demonstrated irregularities in 18 segments of which 5 (28%) appeared normal by intravascular ultrasonography. These data indicate an excellent correlation between intravascular ultrasonography and digital subtraction angiography for in vivo assessment of human arterial dimensions in normal and minimally diseased segments. However, intravascular ultrasonography is more likely to identify atherosclerotic plaque that may be angiographically "silent."     

Intravascular ultrasound of the coronary arteries: Current applications and future directions

Although angiography is widely applied in the diagnosis of the coronary artery disease (CAD), studies have questioned the accuracy of radiographic methods. Miniaturized intravascular ultrasound devices offer several potential advantages, including a tomographic orientation and the ability to characterize atherosclerotic plaques. Two dissimilar technical approaches to transducer design have emerged: mechanically rotated devices and multi-element arrays, each yielding small coronary catheters (1.1–1.8 mm in diameter). Initial studies of coronary ultrasound have demonstrated few serious untoward effects. In most normal subjects, the vessel wall is laminar in appearance with an intimal leading edge and subintimal sonolucent layer averaging ≤0.20 mm in thickness. In most CAD patients, the thickness of the leading-edge or sonolucent zone is abnormally increased. Atherosclerotic abnormalities are frequently evident in segments with no angiographic lesion. At sites with a circular lumen shape, minimum diameter by ultrasound and angiography correlate closely, R = 0.93. At sites with an eccentric lumen, significant disagreement between angiography and ultrasound diameter is evident, R = 0.78. Correlation between angiography and ultrasound from percent stenosis is moderate, R = 0.63. Following balloon angioplasty percutaneous transluminal coronary angioplasty (PICA), morphologic findings include complex cracks, splits, and dissections, and minimum lumen diameter by angiography and intravascular ultrasound correlate poorly. Recent advances have improved the utility of coronary ultrasound, including smaller catheters and a device combining a miniature imaging transducer (1.16 mm) with a low profile balloon (0.028–0.033 inch). Important current limitations include inability to visualize the smallest coronaries and tight stensoses. The future of coronary ultrasound is promising, propelled by the unique capability of this modality to image atherosclerotic plaques directly.     

Visualisation of arterial structure in vivo with intravascular ultrasound

Abstract Background: Contrast angiography provides a silhouette of the arterial lumen, but does not give information about arterial wall structure. Catheter-tip ultrasound transducers can now provide a cross-sectional image of the arterial wall. This study examined the pathological correlation of intravascular ultrasound images and the accuracy of ultrasound measurements of vascular geometry. Methods: Intravascular ultrasound images were obtained with a mechanically rotated catheter-tip transducer and recorded on videotape. Initial validation studies were performed in fresh, postmortem arterial specimens, which were filled with saline at physiological pressures. Ultrasound images at specific sites were compared with the pathological findings at that site and measurements of luminal diameter were compared with corresponding angiographic measurements. Subsequently, intravascular ultrasound was employed to examine the aorta, ilio-femoral and coronary arteries in patients undergoing balloon angioplasty. Results: The pathological correlations showed that intravascular ultrasound can detect early initial thickening and mild atherosclerotic lesions that do not result in luminal deformation. Ultrasound images provided definition of calcified, fibrotic and lipid-filled lesions. Ultrasound measurements of luminal diameter correlated well with pathology measurements (r = 0.93), as did ultrasound measurements of plaque area (r = 0.89). The in vivo studies demonstrated that intravascular ultrasound can define atheroma lesions not evident on contrast angiography and permits detailed evaluation of the results of interventions such as balloon angioplasty. Conclusions: Intravascular ultrasound provides a unique window upon arterial structure and pathology in humans. Ultrasound images allow accurate measurements of vascular geometry and define early atheromatous lesions that are not evident with angiography.     

Videodensitometric quantitative angiography after coronary balloon angioplasty, compared to edge-detection quantitative angiography and intracoronary ultrasound imaging.

AIMS: To assess the value of videodensitometric quantification of the coronary lumen after angioplasty by comparison to two other techniques of coronary artery lumen quantification. METHODS AND RESULTS: Videodensitometric quantitative angiography, edge detection quantitative angiography and 30 MHz intracoronary ultrasound imaging were performed after successful balloon angioplasty in 161 patients. Lumen cross-sectional areas were mean (SD) 2.82 (1.15) mm(2)for edge detection quantitative angiography, 3.67 (1.5) mm(2)for videodensitometric quantitative angiography and 5.32 (1.75) mm(2)for intracoronary ultrasound imaging (P<0.001). The correlation between intracoronary ultrasound imaging and videodensitometric quantitative angiography (r=0.44) was almost similar to that of intracoronary ultrasound imaging and edge detection quantitative angiography (r=0. 47). The correlation between the three techniques was not significantly influenced by the presence of ruptures and dissections on intracoronary ultrasound imaging. The absence of calcifications improved the correlation between videodensitometry and intracoronary ultrasound imaging. CONCLUSIONS: The luminal dimensions as measured by videodensitometric quantitative angiography matched intracoronary ultrasound imaging derived dimensions more closely than edge detection quantitative angiography. Videodensitometric quantitative angiography represents an on-line alternative to intracoronary ultrasound imaging for quantitative analysis regardless of the degree of vessel damage.     

Assessment of the results of percutaneous transluminal coronary angioplasty using an integrated ultrasound imaging-angioplasty Catheter

To evaluate the results percutaneous transluminal coronary angioplasty (PTCA), intra-vascular ultrasound imaging was performed in 32 proximal coronary arterial segments and in 16 atherosclerotic lesions after PTCA in 13 patients using a 5 Fr balloon catheter with an ultrasound transducer mounted just proximal to the balloon. Simultaneous angiographic measurements of vessel diameter were also performed using electronic calipers from contrast cine angiograms. There was good correlation between ultrasound and angiographic minimum luminal diameters of the normal proximal vessel (y = 0.59x + 1.49, r = 0.70, P<0.01, n = 32). However, the luminal diameter measured by intravascular ultrasound was significantly greater than when measured by contrast angiography (2.81±0.10 vs. 2.34±0.12mm, n = 16, P<0.001, mean ±SEM). Post-PTCA, there was good correlation between ultrasound and angiographic minimum luminal diameters of the lesion (y = 0.62x + 1.42, r=0.76, P<0.001, n = 16), but again luminal diameters were significantly greater when measured by intravascular ultrasound compared to contrast angiography (2.61±0.08 vs. 1.89 ± 0.10mm, n = 16, P<0.001). Furthermore, residual stenosis was significantly less when determined by intravascular ultrasound than by contrast angiography (7.3±2.0 vs. 18.1 ± 2.1%, n = 16, P<0.001). Intravascular ultrasound was able to detect coronary calcification that was not evident by contrast coronary angiography in 8 of 16 lesions. Post-PTCA, dissection was evident in four lesions by ultrasound, whereas dissection was appreciated in only three lesions by contrast angiography. We conclude that intravascular ultrasound can accurately measure the luminal diameter of coronary arteries both before and after PTCA and reveals more information about the lesion characteristics than does conventional contrast angiography.     

Intravascular ultrasound imaging

Intravascular ultrasound imaging is a useful and promising modality that is capable of demonstrating the structure of blood vessel walls. It also provides a quantitative assessment of the amount of atheroma present that cannot be visualized by angiography. This article reviews the basic principles of intravascular ultrasound imaging and describes the clinical studies after balloon angioplasty evaluated by intravascular ultrasound imaging.     

How does angioplasty work? Serial analysis of human iliac arteries using intravascular ultrasound.

BACKGROUND. Previous studies regarding the mechanism by which balloon angioplasty increases luminal patency have generally used animal models or postmortem specimens from occasional fatal cases of angioplasty performed in human patients. In either case, conclusions regarding participatory mechanisms have relied exclusively on nonserial, postangioplasty histopathological examination. METHODS AND RESULTS. In the present study, intravascular ultrasound examination was performed before and after balloon angioplasty in 40 consecutive patients with iliac artery stenoses. The areas of the arterial wall, plaque, lumen, and areas resulting from angioplasty-induced plaque fractures were measured immediately after angioplasty in vivo and compared with findings recorded immediately before angioplasty. Angioplasty increased luminal cross-sectional area (CSA) from 11.5 +/- 0.6 mm2 before angioplasty to 25.4 +/- 1.2 mm2 after angioplasty (p = 0.0001). CSA of the portion of the postangioplasty neolumen contained within angioplasty-induced plaque fractures measured 10.0 +/- 0.8 mm2; the neolumen excluding the area contributed by these plaque fractures measured 15.4 +/- 0.8 mm2. Thus, the area contained within plaque fractures accounted for 10.0 mm2 (71.9%) of the 13.9-mm2 increase in luminal CSA after angioplasty. Analysis of CSA occupied by atherosclerotic plaque disclosed that plaque CSA decreased from 33.8 +/- 1.8 mm2 before angioplasty to 22.5 +/- 1.5 mm2 after angioplasty (p = 0.0001). Plaque CSA was thus reduced ("compressed") by 11.3 +/- 1.1 mm2. Total artery CSA increased ("stretched") slightly from 45.3 +/- 2.6 mm2 before angioplasty to 47.8 +/- 2.0 mm2 after angioplasty (p = 0.0025). CONCLUSIONS. In vivo analysis of iliac stenoses by intravascular ultrasound immediately before and after angioplasty demonstrates that plaque fractures and "compression" of atherosclerotic plaque are the principal factors responsible for increased luminal patency resulting from balloon angioplasty. "Stretching" of the arterial wall provides an additional, but minor, contribution.     

Intravascular ultrasound imaging following balloon angioplasty

Despite its long history and reliability, contrast angiography has several inherent limitations. Because it is a two-dimensional projection image of the lumen contour, the wall thickness cannot be measured and the plaque itself is not visualized. This results in an underestimation of the amount of atherosclerotic disease by angiography. An assessment of atherosclerosis could be improved by an imaging modality: (1) that has an inherent larger magnification than angiography and (2) that directly visualizes the plaque. Intravascular ultrasound fulfils these criteria. This presentation will provide evidence that intravascular ultrasound may prove complimentary or even superior to angiography as an imaging modality.Intravascular ultrasound demonstrates excellent representations of lumen and plaque morphology ofin vitro specimens compared with histology. There is very close intraobserver and interobserver variability of measurements made from intravascular ultrasound images. Phantom studies of stenoses in a tube model demonstrate that angiography can misrepresent the severity of stenosis when the lumen contour is irregular and not a typical ellipse, whereas intravascular ultrasound reproduces the cross-sectional morphology more accurately since it images the artery from within.In vitro studies of the atherosclerotic plaque tissue characteristics compare closely with the echo representation of fibrosis, calcification, and lipid material. In addition,in vitro studies of balloon angioplasty demonstrate that intravascular ultrasound accurately represents the changes in the structure of artery segments following balloon dilatation.     

Tissue proliferation within and surrounding Palmaz-Schatz stents is dependent on the aggressiveness of stent implantation technique

In-stent restenosis is entirely due to intimal hyperplasia. Histologic studies have indicated that intimal hyperplasia is related to the arterial injury induced during stent implantation. We used intravascular ultrasound (IVUS) imaging to study whether tissue proliferation inside and surrounding stents is related to the aggressiveness of the implantation technique. After intervention and follow-up (mean 5.6 +/- 3.7 months), serial IVUS imaging was performed in 102 native artery stented stenoses in 91 patients. Measurements at 5 predetermined segments within each stented lesion included external elastic membrane, stent, and lumen cross-sectional areas (CSAs). Calculations included mean plaque CSA growth outside of the stent (external elastic membrane-stent) and mean neointimal hyperplasia CSA and thickness within the stent (stent-lumen). Stenoses were categorized depending on the aggressiveness of stent placement (group 1, adjunct percutaneous transluminal coronary angioplasty pressure < 16 atm and/or balloon/artery ratio < 1.1; group 2, adjunct percutaneous transluminal coronary angioplasty pressure > or = 16 atm and balloon/artery ratio > or = 1.1). An aggressiveness score was calculated as balloon/artery ratio x inflation pressure. Mean intimal hyperplasia CSA (2.9 +/- 1.5 vs 2.2 +/- 1.6 mm2, p = 0.028), mean intimal hyperplasia thickness (0.34 +/- 0.19 vs 0.25 +/- 0.19 mm, p = 0.012), and mean peristent tissue growth CSA (2.5 +/- 1.0 vs 1.1 +/- 1.4 mm2, p = 0.003) were significantly greater in group 2 stenoses. In addition, intimal hyperplasia CSA and thickness correlated significantly with balloon/artery ratio x inflation pressures: r = 0.305, p = 0.002 and r = 0.329, p = 0.0007, respectively, as did peristent tissue proliferation CSA (r = 0.466, p = 0.001). Tissue proliferation inside and surrounding stents may be related to aggressiveness of the stent implantation technique.     

Comparison of angioscopy,intravascular ultrasound imaging and quantitative coronary angiography in predicting clinical outcome after coronary intervention in high risk patients

Objectives. The purpose of this study was to identify qualitative or quantitative variables present on angioscopy, intravascular ultrasound imaging or quantitative coronary arteriography that were associated with adverse clinical outcome after coronary intervention in high risk patients.Background. Patients with acute coronary syndromes and complex lesion morphology on angiography are at increased risk for acute complications after coronary angioplasty. Newer devices that primarily remove atheroma have not improved outcome over that of balloon angioplasty. Intravascular imaging can accurately identify intraluminal and intramural histopathologic features not adequately visualized during coronary arteriography and may provide mechanistic insight into the pathogenesis of abrupt closure and restenosis.Methods. Sixty high risk patients with unstable coronary syndromes and complex lesions on angiography underwent angioscopy (n = 40) and intravascular ultrasound imaging (n = 46) during interventional procedures. In 26 patients, both angioscopy and intravascular ultrasound were performed in the same lesion. All patients underwent off-line quantitative coronary arteriography. Coronary interventions included balloon (n = 21) and excimer laser (n = 4) angioplasty, directional (n = 19) and rotational (n = 6) atherectomy and stent implantation (n = 11). Patients were followed up for 1 year for objective evidence of recurrent ischemia.Results. Patients whose clinical presentation included rest angina or acute myocardial infarction or who received thrombolytic therapy within 24 h of procedure were significantly more likely to experience recurrent ischemia after intervention. Plaque rupture or thrombus on preprocedure angioscopy or angioscopic thrombus after intervention were also significantly associated with adverse outcome. Qualitative or quantitative variables on angiography, intravascular ultrasound of off-line quantitative arteriography were not associated with recurrent ischemia on univariate analysis. Multivariate predictors of recurrent ischemia were plaque rupture on preprocedure angioscopy (p < 0.05, odds ratio [OR] 10.15) and angioscopic thrombus after intervention (p < 0.05, OR 7.26).Conclusions. Angioscopic plaque rupture and thrombus were independently associated with adverse outcome in patients with complex lesions after interventional procedures. These features were not identified by either angiography or intravascular ultrasound.     

Balloon angioplasty results in increased segmental coronary distensibiliy: A likely mechanism of percutaneous transluminal coronary angioplasty

Objectives. The purpose of this study was to evaluate the hypothesis that the increase in lumen area induced by percutaneous transluminal coronary angioplasty is secondary to a change in lesion (segmental) distensibility.Background. Despite the widespread use of coronary angioplasty, the precise mechanism (or mechanisms) of lumen area improvement remains poorly understood.Methods. Quantitative coronary angiography was used to measure the minimal (contrast agent filled) balloon diameters at 1 to 5 atm, inclusive, during the first and final balloon inflations in 24 lesions successfully treated with coronary angioplasty. To rule out possible confounding effects due to changes in balloon material distensibility during repeated inflations, five control balloons were studied ex vivo. In parallel, intravascular ultrasound imaging was utilized to compare the segmental distensibility (change in lumen area during the cardiac cycle) of eight disease-free and seven mildly diseased coronary segments and seven segments after successful balloon angioplasty.Results. Minimal balloon diameters increased significantly between the first and final inflations (46%, 33%, 26%, 14% and 10% at 1, 2, 3, 4 and 5 atm, respectively, all p < 0.0001), demonstrating an increase in arterial distensibility after successful coronary angioplasty. No significant changes in balloon diameters were observed during sequential initial inflations at 1 and 2 atm (n = 5). Minimal increases in Balloon diameters were observed during repeated balloon inflations in the ex vivo studies (4.9 ± 1% [mean ± SEM]). A distensibility index, derived from the intravascular ultrasound data, was not different between the balloon-dilated and the normal segments but was significantly lower in mildly diseased sites (14.7 ± 2.2 vs. 12.9 ± 1.2 vs. 6.9 ± 1.9, respectively, p < 0.05) despite a smaller plaque area (7.3 ± 1 vs. 11.3 ± 1 mm², proximal/nondilated vs. dilated segments, respectively, p < 0.05).Conclusions. Coronary distensibility is significantly impaired in atherosclerotically diseased coronary segments and increases significantly after balloon angioplasty. This increase in segmental coronary compliance after coronary angioplasty may create a larger lumen area by allowing the vessel to distend in response to normal intraarterial pressure.