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 the coronary arteries: an in vitro evaluation of measurement of area of the lumen and atheroma characterisation.

OBJECTIVE--To assess the accuracy of measurement of area of the lumen, and sensitivity, and specificity of detection of atheroma in coronary arteries in vitro with a commercially available 20 MHz intravascular ultrasound system. SETTING--A teaching hospital department of cardiology with the support of the department of cardiovascular pathology. PROCEDURE--10 segments of coronary artery were removed from cadaver hearts. Intravascular ultrasound imaging was performed at fixed levels and the vessels were then sectioned and photographed before histological preparation. An independent blinded observer measured luminal area and assessed the presence of atheroma on the intravascular ultrasound images of 76 vessel sections (304 quadrants). The sensitivity and specificity of detection of atheroma was assessed in comparison with the histologically prepared sections. Luminal areas from intravascular ultrasound, photographs of cross sections of the vessels and histological sections were compared with the technique of limits of agreement. RESULTS--Overall 36% of the 304 quadrants studied histologically had identifiable atheroma. Intravascular ultrasound sensitivity for atheroma was 0.593 and the specificity was 0.839. The positive predictive value was 0.674, and the relative risk 3.139. Values for area of the vessel lumen were on average 9.4 mm2 (confidence interval (CI) 8.6-10.2 mm2) larger than those measured from photographs and 10.7 (CI 9.8-11.6 mm2) larger than those measured from the histological sections. CONCLUSIONS--The intravascular ultrasound system assessed in this study significantly overestimated coronary vessel luminal area and had low sensitivity and specificity for detection of atheroma. Improvements in image resolution are required before this system can provide useful information on coronary artery size and morphology.     

血管内超声的冠状动脉腔内成形术的机制研究

目的应用血管内超声的方法研究病人经皮冠状动脉(冠脉)腔内成形术(PTCA)前后冠脉内的粥样斑块和血管壁的变化,进一步明确PTCA的机制。方法择期行PTCA的病人50例,共68支血管于球囊扩张前后行冠脉内超声(ICUS)检查。记录病变部位粥样斑块的特性,最小管腔面积,弹力内膜面积和斑块面积。结果PTCA球囊扩张前后病变部位的内弹力膜面积(IELA)分别为(6.67±1.45)mm2和(8.14±1.13)mm2,术后有明显的扩大(P＜0.05)。脂质斑块,纤维斑块,钙化斑块,混合斑块各组PTCA手术前后IELA之差(ΔIELA)分别为1.84,1.52,0.40,1.23mm2,钙化斑块球囊扩张前后内弹力膜面积无明显扩大,P＜0.05。斑块的撕裂程度及管壁变化根据Honye分类法记录A型10例,B型20例,C型16例,D型12例,E1型5例,E2型5例。68个病变中有58个（85%）病变出现不同程度的斑块撕裂。12个D型撕裂中有11个是钙化的斑块,1个是混合斑块。结论粥样斑块的撕裂和管壁的牵伸在冠脉球囊扩张术的管腔增大方面同时起关键作用,较硬的斑块如钙化的斑块球囊扩张时易出现大的夹层,而血管牵伸的程度较差,用旋磨或旋切的方法处理可能会得到更好的结果。     

Atherosclerotic saphenous vein grafts treated with different interventional procedures assessed by intravascular ultrasound.

Intravascular ultrasound imaging of saphenous vein grafts may enhance the angiographic interpretation of results following transcatheter interventions. We used intravascular ultrasound to study 18 patients with stenotic vein grafts following balloon angioplasty, atherectomy, or stent placement. In real-time imaging the three-layer appearance was rarely seen, calcification was infrequent (11% of patients), and atheroma were usually mildly echogenic ("soft"). Despite excellent angiographic results (reduction in percent diameter stenosis from 90 +/- 8% to 17 +/- 8%) and concordant improvement in lumen area by ultrasound regardless of the intervention, there was usually significant retained atheroma at the treatment site. Following balloon angioplasty, ultrasound showed multiple superficial fissures and fractures without discrete dissections. Atherectomy caused a smooth lumen surface without deep dissections or resections, but significant retained atheroma was observed with each one of the atherectomy procedures. Endovascular stents were concentric in the vein with reflective struts above compressed atheroma and an outer echogenic adventitia. Stent expansion was asymmetric axially and longitudinally and evidence of stent recoil was present. Thus intravascular ultrasound may be an important adjunct to angiography in characterizing postintervention results in saphenous vein grafts.     

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.     

Predictors of event-free survival after repeat intracoronary procedure for in-stent restenosis; study with angiographic and intravascular ultrasound imaging.

AIMS: Lumen enlargement during repeat percutaneous coronary intervention for in-stent restenosis has been shown to be the result of both stent over-expansion and decrease in neointimal tissue. How these two different mechanisms of action may influence outcome and target lesion revascularization after repeat intervention for in-stent restenosis is unclear. METHODS: Intravascular ultrasound guided repeat intervention for in-stent restenosis was carried out either with balloon angioplasty, or with a combination of rotational atherectomy plus balloon angioplasty. Clinical follow-up at 1 year, including death, myocardial infarction, or need for revascularization, was obtained. RESULTS: Seventy patients were included in this study; 40 were treated by balloon alone, and 30 by combination of rotational atherectomy plus balloon. Event-free survival probability was 76+/-5%. The mechanism of lumen enlargement, be it stent over-expansion or tissue removal, had no influence on long-term clinical evolution. The only independent predictor was the minimal lumen cross-sectional area at the end of the procedure, the larger the lumen cross-sectional area, the higher the event-free probability. The cut-off point of the lumen cross-sectional area was set at 4.7 mm(2)by discriminant analysis. Event-free survival was 69+/-15% in patients with <4.7 mm(2)lumen cross-sectional area and 91+/-8% in patients with >4.7 mm(2)lumen cross-sectional area (P=0. 008). CONCLUSIONS: This study showed that the only independent predictor of late clinical outcome after percutaneous re-intervention for in-stent restenosis was final lumen size, no matter which means were used to achieve it.     

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.     

Mechanisms of balloon angioplasty and directional coronary atherectomy as assessed by intracoronary ultrasound.

OBJECTIVE. This study was designed to use intracoronary ultrasound imaging to elucidate the physical effects of balloon angioplasty and directional coronary atherectomy in vivo in humans. BACKGROUND. The proposed mechanisms of coronary artery interventions such as balloon angioplasty and directional atherectomy are based on animal studies or pathologic findings and these data may not be applicable to living patients. Intracoronary ultrasound findings correlate highly with pathologic results and may allow in vivo assessment of the mechanisms of such interventions in humans. METHODS. Intracoronary ultrasound imaging was performed in 45 patients after a successful coronary intervention (balloon angioplasty in 30, directional coronary atherectomy in 15). Ultrasound images obtained at the treatment site and at an adjacent angiographically normal references site were analyzed quantitatively for minimal lumen diameter, cross-sectional lumen area, are enclosed by the internal elastic lamina, plaque area (internal elastic lamina area--lumen area) and percent area stenosis (plaque area/internal elastic lamina area). Qualitative analysis included assessment of presence of dissection, plaque composition and plaque topography. RESULTS. The results of the two procedures were similar with respect to minimal lumen diameter (angioplasty 2.6 +/- 0.5 vs. atherectomy 2.6 +/- 0.3 mm, p = NS), lumen area (0.07 +/- 0.03 vs. 0.07 +/- 0.02 cm2, p = NS) and percent area stenosis (59 +/- 14% vs. 51 +/- 21%, p = NS). However, after angioplasty, the internal elastic lamina area was significantly larger at the treated site than at the reference site (delta = +0.03 +/- 0.04 cm2, p = 0.01). There was no significant difference between the two sites after atherectomy (delta = -0.01 +/- 0.05 cm2, p = NS). In addition, dissection was seen significantly more often after balloon angioplasty than after atherectomy (50% vs. 7%, p less than 0.01). The results were similar when stratified for plaque composition and morphology. These data were confirmed in six additional patients who underwent ultrasound imaging before and after the intervention. CONCLUSIONS. Thus, the improvement in lumen dimensions after coronary balloon angioplasty is a result of both vessel stretch, demonstrated by a larger internal elastic lamina area at the treated site, and dissection. Both vessel stretch and dissection are uncommon after atherectomy, a finding consistent with plaque removal as the major mechanism for improved lumen area after this procedure.     

Effects of intravascular cryotherapy on vessel wall repair in a balloon-injured rabbit iliac artery model

OBJECTIVE: Although the application of cold energy, cryotherapy, has been shown to cause selective damage to cellular components with preservation of matrix structure resulting in less fibrosis in a variety of tissues, the effects of intravascular cryotherapy on vessel wall repair after balloon angioplasty are unknown. We sought to characterize the effects of cryotherapy application on vessel wall repair after balloon angioplasty and study the relationship between collagen accumulation in the vessel wall and late lumen loss as assessed by serial intravascular ultrasound. METHODS: The immediate, early (72 h) and late (10 weeks) effects of three intravascular cryotherapy application time periods (60, 120 and 240 s) after iliac artery balloon angioplasty ('cryotherapy') were compared with balloon angioplasty alone ('control') in 59 rabbits. Arterial lumen area was measured by intravascular ultrasound immediately after the procedure, at 72 h and at 10 weeks. Collagen content was calculated separately for intima and media/adventitia layers and correlated with late lumen loss. RESULTS: Cryotherapy produced average vessel wall temperature of -26 degrees C (range, -20 to -45 degrees C) and resulted in significantly larger lumen cross-sectional area (CSA) immediately after application (5.74+/-1.18 vs. 4.14+/-0.75 mm(2), P=0.008) but was not different than control arteries at 10 weeks. At 72 h, there was extensive cell loss in the medial and adventitial layers accompanied by increased macrophage infiltration in cryotherapy treated arteries compared to control. At 10 weeks, intimal hyperplasia was increased 2-fold in cryotherapy treated arteries. Collagen content was increased 2-fold in the medial/adventitial layers, and nearly 3-fold in the intima of cryotherapy treated arteries. Collagen content in arterial intima (P=0.01) as well as media/adventitia (P=0.005) positively correlated with late lumen loss. Foci of chondro- and osseous metaplasia and calcification were evident at the medial-adventitial junction in cryotherapy treated arteries at 10 weeks. CONCLUSION: Intravascular cryotherapy induced early arterial wall cell loss and late intimal hyperplasia, vascular fibrosis and chondro- and osseous metaplastic changes with no late beneficial effects on lumen area compared to balloon angioplasty alone. Collagen accumulation in all three layers of the vessel wall contributes to the development of late inward remodeling after balloon angioplasty.     

Applicability of laser to assist coronary balloon angioplasty

Severe atherosclerotic obstructed coronary artery disease (CAD) may preclude passage of a balloon catheter for transluminal coronary angioplasty (TCA). Since lasers have been shown to effectively vaporize CAD plaque, the initial application of laser to effect a lumen large enough to accommodate the angioplasty catheter for further dilatation was explored. Eleven postmortem human CAD segments which did not permit passage of a 1.33 mm shaft diameter angioplasty catheter were studied. Argon laser radiation (14 to 90 J) transmitted via 400 micron core diameter quartz fiber onto the stenotic channel of 0.58 mm created a vaporized lumen of 1.77 mm (mean increase of 1.31 +/- 0.25 mm, p less than 0.001). The laser procedure allowed the balloon angioplasty catheter to be pushed into the stenosis. TCA was then performed (7 atm, 45 seconds) and expanded the channel to 2.12 mm (additional mean increase of 0.38 +/- 0.07 mm, p less than 0.001). In terms of percent luminal narrowing, laser radiation reduced obstruction from 80% to 45% (mean difference of -38.7 +/- 4.6%, p less than 0.001), and TCA caused a further decrease to 37% (mean difference of -9.3 +/- 1.9%, p less than 0.001). Thus, in tight atherosclerotic lesions, the laser may be useful in creating an initial opening enabling the placement of the balloon angioplasty catheter which, in turn, can further dilate the lased stenotic coronary lumen.     

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.     

Diffuse intimal thickening of coronary arteries in slow coronary flow

Intravascular ultrasound imaging can detect intimal thickening and is suitable for detection of early atherosclerosis, which cannot be detected by conventional angiography. The aim of the present study was to investigate the epicardial coronary morphology and intracoronary pressure in relation to slow coronary flow (SCF). The study population consisted of 19 patients with SCF [11 (57.9%) females; 55.95 +/- 9.42 years]. Proximal, middle, distal and mean total vessel area, lumen area, intima + media area (IMA), percent IMA, and maximal intima + media (I + M) thickness were calculated and compared to healthy subjects. Proximal, middle, distal and mean I + M thickness, IMA, and % IMA of patients with SCF were found to be significantly higher than those of control subjects. Longitudinally extended massive calcification throughout the epicardial arteries was found in 13 (68.49%) patients with SCF and regional calcification was found in 6 (31.6%) patients with SCF. Proximal and distal pressure gradients of patients with SCF were determined to be 15.84 +/- 12.11 mmHg in the intracoronary pressure measurements. Fractional flow reserve values were significantly lower than the normal population (0.83 +/- 0.13, P < 0.0001). This study indicates that patients with SCF have diffuse intimal thickening, widespread calcification along the vessel wall and atheroma which does not cause luminal irregularities in coronary angiography, and a pressure gradient between proximal and distal segments of epicardial coronary arteries with SCF. Based on these results, we believe that SCF may be a form of diffuse atherosclerosis involving both the microvascular system and epicardial coronary arteries.     

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.     

Attenuation of the media of coronary arteries in advanced atherosclerosis

Human coronary artery wall architecture was analyzed in detail in 127 histologic sections with varying degrees of narrowing due to atherosclerotic plaque. A planimetry-microscope system was used to morphometrically determine percent luminal cross-sectional area narrowing due to atherosclerotic plaque, absolute area of the coronary artery media and total cross-sectional area of the coronary artery section. In 65 sections in which the native coronary artery lumen was narrowed less than 75%, the area of the coronary artery media corrected for total coronary cross-sectional area (Mc) was 0.244 +/- 0.055 mm2. In contrast, among 62 sections in which the coronary artery lumen was narrowed more than 75% in cross-sectional area, Mc measured 0.180 +/- 0.078 (p less than 0.001). Thus, in coronary artery segments with advanced atherosclerosis, there is substantial attenuation of the media, normally the principal component of the coronary artery wall.     

Percutaneous excimer laser coronary angioplasty

To determine the efficacy of percutaneous excimer laser coronary angioplasty as an adjunct or alternative to conventional balloon angioplasty, 55 patients were studied in a multicenter trial. These patients underwent the procedure using a modification of conventional balloon angioplasty technique. A first-generation, 1.6-mm diameter catheter constructed of 12 individual silica fibers concentrically arranged around a guidewire lumen was used. Catheter tip energy density varied from 35 to 50 mJ/mm2. The mean number of pulses delivered at 20 Hz was 1,272 +/- 1,345. Acute success was defined as a greater than or equal to 20% increase in stenotic diameter and a lumen of greater than or equal to 1 mm in diameter after laser treatment. Acute success was achieved in 46 of 55 (84%) patients. Adjunctive balloon angioplasty was performed on 41 patients (75%). The percent diameter stenosis as determined by quantitative angiography decreased from a baseline of 83 +/- 14 to 49 +/- 11% after laser treatment and to 38 +/- 12% in patients undergoing adjunctive balloon angioplasty. The mean minimal stenotic diameter increased from a baseline of 0.5 +/- 0.4 to 1.6 +/- 0.5 mm after laser treatment and to 2.1 +/- 0.5 mm after balloon angioplasty. There were no deaths and no vascular perforations. One patient (1.8%) required emergency coronary bypass surgery. These data suggest that excimer laser energy delivered percutaneously by specially constructed catheters can safely ablate atheroma and reduce coronary stenoses.     

The impact of high pressure vs low pressure stent implantation on intimal hyperplasia and follow-up lumen dimensions; results of a randomized trial.

AIMS: Histology and retrospective clinical studies have indicated that the amount of neointimal hyperplasia is dependent on the arterial injury induced during stent implantation. This study analysed, prospectively, the impact of high vs low pressure stent implantation techniques using a second generation stent on intimal hyperplasia and follow-up lumen dimensions. METHODS AND RESULTS: Post-intervention and follow-up (mean[+/-SD] 5.5+/-1.3 months) angiographic and intravascular ultrasound studies were performed on 120 Multi-Link HP stents randomized to implantation at either low (8-10 atm) or high (16-20 atm) pressure. Intravascular ultrasound measurements of the external elastic membrane, stent, and lumen cross-sectional area were performed at 1 mm axial increments. Peri-stent plaque+media cross-sectional area (external elastic membrane-stent cross-sectional area, intimal hyperplasia cross-sectional area (stent-lumen cross-sectional area at follow-up), intimal hyperplasia thickness and peri-stent tissue growth cross-sectional area (Deltapersistent plaque+media cross-sectional area) were calculated. Intravascular ultrasound demonstrated a larger minimal lumen cross-sectional area post-intervention in the high pressure group (7.3+/-2.0 vs 6.2+/-1.8 mm(2), P<0.001, high vs low pressure group, respectively). At follow-up, the mean intimal hyperplasia cross-sectional area (1.7+/-0.9 vs 1.5+/-0.8 mm(2), P=0.708), the mean intimal hyperplasia thickness (0.16+/-0.12 vs 0.16+/-0.12 mm, P=0.818) and peri-stent tissue proliferation cross-sectional area were not greater in the high pressure group. Thus, the minimal lumen cross-sectional area at follow-up continued to be greater (5.5+/-2.0 vs 4.7+/-1.7 mm(2), P=0.038) in the high pressure group. CONCLUSIONS: High pressure stent implantation results in greater stent expansion even with the less rigid second generation Multi-Link stent. Larger lumen dimensions persist at follow-up, while intimal hyperplasia is not significantly greater after high pressure implantation compared to the low pressure technique.     

Unrecognized stenosis by angiography documented by intravascular ultrasound imaging

This report documents how intravascular ultrasound imaging was used to diagnose a short "napkin-ring" stenosis that was missed by coronary angiography. Intravascular ultrasound revealed a lumen of 2.6 x 2.5 mm in diameter and 5.0 mm2 in cross-sectional area, with a residual atheroma that occluded 63% of available cross-sectional area at the stenosis.     

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.     

Real-time assessment of experimental arterial angioplasty with transvenous intravascular ultrasound.

Optimal evaluation of experimental angioplasty procedures would allow real-time simultaneous assessment during the procedure without direct manipulation of treated arterial segments. To assess the feasibility and utility of transvenous real-time intravascular ultrasound imaging during experimental angioplasty, 11 consecutive atherosclerotic iliac artery segments in rabbits were imaged before, during and after thermal or conventional perfusion balloon angioplasty. A 20-MHz intravascular ultrasound catheter was positioned in the adjacent vein, and images were correlated with data from quantitative angiography and histologic studies. Images suitable for analysis were obtained at all 11 sites. Arterial distension and recoil were observed during balloon inflation and deflation. Measurements of lumen diameter and cross-sectional area by intravascular ultrasound and angiography were closely correlated (r2 = 0.90, SEE = 0.2 mm, and r2 = 0.90, SEE = 0.8 mm2, respectively). Intimal dissections were identified in six segments by intravascular ultrasound and all were concordant with histologic findings. Thus, real-time transvenous ultrasound avoids manipulation of the treated artery, and is a feasible modality for dynamic quantitative and qualitative assessment of arterial interventions.     

Effects of radial stretch on target lesion revascularization after percutaneous coronary intervention: an intravascular ultrasound study

OBJECTIVE: To analyze possible associations between radial stretch during coronary angioplasty and the incidence of target lesion revascularization (TLR). PATIENTS AND METHODS: Intravascular ultrasound images were obtained before and after revascularization in 182 native coronary lesions. The quantitative intravascular ultrasound parameters (external elastic membrane cross-sectional area [EEM-A], lumen areas [LA], plaque area [PA], calculated as EEM-A-LA, and changes between pre- and postinterventional LA [DLA], EEM-A [DEEM-A] and PA [DPA]) were correlated with the incidence of TLR. RESULTS: TLR was performed in 60 (33%) patients, while 122 (67%) patients remained event free. Postinterventional PA remained significantly larger in the TLR group than in the event-free group (9.2 +/- 3.3 mm2 versus 7.9 +/- 3.3 mm2; P=0.02). The radial stretch during intervention, expressed as DEEM-A, and the balloon to artery ratio was significantly larger in the TLR group (DEEM-A: 1.9 +/- 2.1 mm2 versus 1.3 +/- 2.0 mm2; P=0.03; balloon to artery ratio: 1.3 +/- 0.2 versus 1.0 +/- 0.5; P=0.04). Multivariate analysis revealed DEEM-A (P=0.01), DPA (P=0.03), diabetes (P=0.001, odds ratio 5.2, 95% CI 4.9 to 6.5) and adaptive remodelling (P<0.001, odds ratio 4.1, 95% CI 3.5 to 6.4) as independent predictors for TLR. CONCLUSION: Whereas patients in whom lumen gain is achieved primarily by plaque reduction with less wall stretch tend to remain event free, patients with significant radial stretch (ie, less reduction of the PA, but a radial outward shift of the plaque mass) experience a higher incidence of TLR.