Imaging of post-mortem coronary arteries by 30 MHz intravascular ultrasound

Intravascular ultrasound cross-sectional imaging of the atherosclerotic artery may be employed to guide plaque ablation by spark erosion, atherectomy, laser irradiation or other means. To assess whether in the coronary artery the echolucent zone of the three-layered ultrasound appearance of muscular arteries might be a reliable boundary to halt transluminal ablative angioplasty, epicardial coronary arteries were scanned under pressure over a distance of 4–8 cm at 1 mm intervals. A 5.2F catheter with a 30 MHz transducer rotating at 600 RPM was used. In 419 images from four post-mortem hearts, aged at death 22, 31, 56 and 82 years, the presence of a distinct echolucent zone was scored as percentage of the wall circumference. The median scores were 0%, 0%, 10% and 75%, respectively. In the three youngest hearts, the three-layered appearance was largely absent. In the 82 year old heart, in contrast, the three-layered appearance could generally be identified. Within subjects, the presence of an echolucent zone was variable in location. Qualitatively, neither abundant medial elastin tissue nor a reduced medial thickness could explain the absence of an echolucent zone when the ultrasound image was compared to the corresponding microscopic section. The results show that in the 82 year old heart, 30 MHz intravascular ultrasound discrimination of coronary wall layers would be adequate to guide transluminal plaque ablation. In the younger hearts, guided ablation would fail due to the limited presence of a distinct echolucent zone as an ultrasound landmark of the media. Whether the presence or absence of an echolucent zone is related to age remains to be determined.     

Assessment of arterial disease and arterial reconstructions by intravascular ultrasound

Clinical application of intravascular ultrasound to assess arterial atherosclerotic disease was introduced in humans after extensivein vitro andin vivo animal studies. Real-time images, obtained with a 30 MHz element mounted on a 5 F catheter, consistently confirmed angiographic images, up till now considered to be the gold standard. In addition to these data, ultrasonic cross-sectional imaging provided information on the composition of atheroselectic lesions and the size and shape of the lumen. Based on the experimentally derived criteria for tissue characterization, a better insight into arterial morphology could be obtained, allowing improved planning of interventional or reconstructional procedures. Moreover intravascular ultrasound has proved valuable as a post-interventional procedure to monitor and assess the quality of interventional results. The ultrasound images are clearly superior to angiographic studies, albeit the ultrasonic information is an adjunct to angiography and, as yet, not a substitute. We present our initial experience with intravascular ultrasound obtained in patients with substantial peripheral arterial disease.     

Comparison of normal and diseased pulmonary artery morphology by intravascular ultrasound and histological examination

The study was performed to determine the morphological characteristics of normal and diseased pulmonary arteries by ultrasound (intravascular ultrasound, IVUS) and histology. Forty-nine cadaver segments of pulmonary arteries from 16 postmortem patients were imaged in vitro by IVUS and compared to matched histological sections. The pulmonary vasculature of 11 patients with pulmonary hypertension was investigated in vivo by IVUS. In the in vitro study, 34 of a total of 143 histological sections of the segmental pulmonary arteries showed fibrotic wall components; the remaining 109 sections had regular components. Imaged by IVUS, the wall of the regular and fibrotic arteries revealed a single layer histologically, representing the intima, media, adventitia and connective tissue. Adjacent lung tissue could be detected by IVUS and was confirmed by the histological section. In three patients with a history of chronic embolic pulmonary hypertension, IVUS revealed thrombi or a double vessel wall layer. Histologically, the material extracted after pulmonary thromboendarterectomy in two patients showed wall-adherent thrombus features of early organization. In all other patients only a single wall layer was seen. The vessel walls (intima, media, adventitia and connective tissue) of regular and slightly fibrosed pulmonary arteries show only a single layer. Wall-adherent organized thrombi in chronic embolic pulmonary hypertension can be detected by IVUS as a second inner vessel layer. Thus IVUS may represent an additional tool for detecting chronic embolic pulmonary hypertension when the results of pulmonary angiography or computed tomography are not definite.     

Identification of atrial tissue in pulmonary veins using intravascular ultrasound.

BACKGROUND: Atrial fibrillation (AF) is initiated by ectopic beats originating in the sleeve of atrial tissue in pulmonary veins (PVs). Circumferential ablation of PVs can, thus, result in a cure of AF. Identification of this PV arrhythmogenic tissue has been exclusively on the basis of electrophysiologic recordings. The purpose of this study was to visualize this tissue using intravascular ultrasound (IVUS).Methods and results In all, 15 patients undergoing AF ablation had IVUS studies of their PVs. A total of 21 veins had a wall thickness less than 0.1 mm, whereas 31 veins had well-demarcated areas of thickening measuring 0.81 +/- 0.32 mm. Electrophysiologic recordings from these thickened areas showed typical high-frequency potentials associated with arrhythmogenic atrial tissue in the PVs. Ectopic beats initiating AF always originated from these areas. PVs without thickening on IVUS did not have these potentials. CONCLUSIONS: IVUS permits visualization of atrial tissue in the PVs, and arrhythmogenic PVs are qualitatively and quantitatively different from nonarrhythmogenic PVs.     

Imaging ultrasound in the intraoperative diagnosis of vascular defects

High-resolution real-time ultrasonography was employed during 267 vascular operations in order to diagnose vascular defects such as intimal flaps, strictures, and thrombi. These defects occur at operative areas (e.g., anastomoses, endarterectomized segments, and sites of placement of occlusive clamps) and can lead to serious thrombotic complications in the early post-operative period. Ultrasound detected vascular defects in 83 patients (31.1 per cent). The defects in 59 patients were considered clinically insignificant because of their sizes and locations, and were not re-explored. Early post-operative results of these patients were comparable to those of the patients without demonstrated defects. In 24 patients (9.0 per cent of all patients examined), ultrasonography revealed clinically significant defects which prompted re-exploration. In 20 of these 24 patients, these vascular defects were confirmed and corrected. No defect was found at re-exploration in four patients, but two of them developed early postoperative thrombosis. Ultrasonography and arteriography were compared at 100 operative sites. The two imaging methods were equal in terms of sensitivity, specificity, efficiency, and predictability of a negative test. Predictability of a positive test was 77.8 per cent for ultrasonography and 59.1 per cent for arteriography. This indicates that fewer needless re-explorations would occur following a decision based on ultrasonography. Operative ultrasonography is a simple, safe and accurate technique that should be applied to reconstructive vascular surgery for diagnosis of vascular defects.     

血管内超声评估老年不稳定型心绞痛患者冠脉病变

目的 使用血管内超声探讨老年冠心病患者冠脉病变特点.方法 选择39例老年不稳定型心绞痛患者（UA）为研究对象, 28例稳定型心绞痛患者（SA）为对照组,使用血管内超声分别测定两组患者＂罪犯＂病变血管的外弹力膜面积（EEM）、管腔横截面积（LA）、斑块面积（PA）、斑块负荷（PB）、重构指数（RI）及偏心指数（EI）等指标,并利用虚拟组织学技术对斑块成分进行比较分析.结果 UA组和SA组患者的＂罪犯＂病变血管的LA、PA、PB比较差异均无统计学意义（P＞0.05）;两组EEM、RI、EI比较差异有统计学意义（P＜0.05）;UA组斑块中脂质、坏死组织所占比例较SA组显著增高,而SA组斑块以纤维组织多见（P＜0.01）.结论 老年冠心病患者临床表现与冠脉病变斑块结构、成分关系密切.     

Eprosartan in the primary prevention of cardiac allograft vascular disease: a double-blind prospectively randomized study using intravascular ultrasound

The angiotensin blocker (ARB) eprosartan (600 mg once daily) and the calcium antagonist diltiazem (90 mg twice daily) were studied in a 24-month prospective, randomized, double-blind trial involving 53 heart transplant patients. The study compared their effects on the development of post-transplant cardiac allograft vasculopathy, a condition that frequently impairs long-term post-transplantation survival and where angiotensin blockers might be expected to play a preventive role. From baseline to month 12, the mean plaque volume increased by 7.7 mm(3) for eprosartan-treated patients and by 34.4 mm(3) for diltiazem-treated patients, but the eprosartan-related trend for reduced myointimal hyperplasia was not statistically significant. The trend in favour of eprosartan for secondary parameters (mean intimal index, vessel volume, lumen volume and coronary flow reserve) also failed to reach significance. The lack of effect might be due to a lower than planned sample size and observation periods due to recruitment difficulties. A larger study is required to confirm these preliminary findings.     

Carotid artery ultrasound and intravascular ultrasound

Lipid lowering therapy is associated with a significant reduction in cardiocerebral events. But, additional studies are necessary to identify patients in whom atheroma may results in developing coronary events. Intravascular ultrasound(IVUS) and carotid artery echocardiography have significantly contributed to the understanding of nature of atherosclerosis and have validated the concepts of vascular remodeling and vulnerable plaque. Actually, intimal-medial thickness(IMT) in carotid echo is good predictors of cardiovascular events. Positive remodeled plaque with soft characteristics is more likely to rupture and cause acute coronary syndrome. Thus, studies using IVUS and carotid echo may lead to important insights into how risk factor reduction stabilizes plaque and reduces the risk of acute coronary events.     

超声在肺部疾病中的临床应用

肺部床旁超声是急诊科及重症监护室用于快速诊断和监测治疗的工具。经胸壁肺部超声（简称肺部超声）在诊断肺炎、气胸、肺栓塞、胸腔积液、肺间质综合征等疾病中有很高的敏感度、特异度和诊断准确率,此外,还可评估从肺间质综合征到肺实变的演变过程,并可对治疗效果提供实时反馈。本文对肺部超声的临床应用进行综述。     

新生儿肺部疾病的超声应用

目前临床诊断新生儿肺部疾病主要依赖放射学检查,然而放射性辐射对新生儿有较大损伤。随着超声影像诊断技术的发展,超声已成功用于新生儿肺部疾病的辅助诊断及治疗中的实时监测。本文就超声在新生儿肺部疾病诊断及治疗中的应用进展进行综述。     

术中超声在脑血管疾病的应用

目的 采用术中超声观察不同颅内血管性病变的显示情况,探讨术中超声实时定位病灶、指导手术切除的价值.方法 对204例颅内血管性疾病患者行术中超声检查,对动静脉畸形患者寻找供血动脉和引流静脉.对海绵状血管瘤患者剪开硬脑膜切除病变前(术前)、经大脑皮层造瘘到达病灶时(术中)以及病灶切除术后(术后)均行术中导航及术中超声检查,并比较二者定位的准确性.结果 ①术中超声对颅内血管性疾病的显示率为98%,其中对颅内动静脉畸形和海绵状血管瘤的显示率均为100%,动脉瘤的显示率为81%,血管母细胞瘤的显示率为91%.②术中超声对颅内动静脉畸形患者供血动脉及引流静脉的显示率为71%.③术中超声与术中导航在海绵状血管瘤切除术前定位的准确率差异无统计学意义(100%对95%,P=0.244).术中超声在海绵状血管瘤切除术中、术后定位的准确率明显高于术中导航,差异有统计学意义(100%对74%,x2=19.513,P＜0.0001,100%对68%,x2=24.973,P＜0.0001).结论 术中超声对颅内血管性疾病具有较高的显示率,并可准确定位病变,指导手术,缩短手术时间,减少损伤,提高手术的精确性.     

Assessment of coronary compensatory enlargement by three-dimensional intravascular ultrasound

Several techniques have been used to demonstrate that human arteries respond to atherosclerosis by increasing their total arterial area to prevent a decrease in blood flow. Three-dimensional reconstructions of coronary arteries can document this compensatory response accurately and specifically. Seven human coronary arteries were reconstructed using intravascular ultrasound and biplane angiography, and vessel geometries were quantified. In all seven vessels, as plaque area increased, overall vessel area increased (R = 0.986, 0.933, 0.984, 0.678, 0.763, 0.963, and 0.830), but luminal cross-sectional area did not significantly decrease. Focal compensatory enlargement was identified in each vessel, and in some cases this response appeared to occur until the vessel was 65% occluded. Luminal enlargement near the proximal ends was attributed to the natural taper of the vessel. The semi-automated, three-dimensional segmentation technique used in this study allows reproducible quantification, as there is no subjective manual tracing involved. Following the intravascular ultrasound transducer in time and space with biplane angiography allows for accurate reconstruction with or without automated pullback devices. Information on the rate of change of vessel measurements is also presented, which, when combined with visualization of accurate 3D geometry, provides a unique assessment of coronary compensatory enlargement. This reconstruction technique can be applied in a clinical environment with no major modification.     

血管内超声检测易损斑块的研究进展

早期检测易损斑块对于急性冠脉综合征的防治有重要意义。血管内超声是检测易损斑块的重要方法,有着独特优势。本文就血管内超声及其衍生技术检测易损斑块的基本原理和研究进展作一综述。     

Detection and characterization of vascular lesions by intravascular ultrasound: an in vitro study correlated with histology.

High-frequency intravascular ultrasound (30 and 40 MHz) was applied to study 112 human vascular specimens. The ultrasound images were compared with histologic cross-sections. In 44 out of 58 of the histologically classified muscular arteries, a hypoechoic middle layer was seen in the vessel wall, giving it a three-layered appearance. In 10 arteries, fibrous degeneration of the muscular media resulted in a homogeneous appearance of the vessel walls, whereas atherosclerotic plaque precluded the visualization of the arterial media in four of the arteries. A three-layered appearance was seen in seven of nine histologically classified transitional arteries, and a homogeneous arterial wall was seen in two of the nine. None of the 33 elastic arteries, veins, venous bypass, and Goretex conduits showed a hypoechoic medial layer. Histologically proved fibrous intimal thickening was echographically detected in 32 of 48 specimens (67%). It was noted that these intimal lesions were easier to detect with 40 MHz than with 30 MHz transducers. Hypoechoic areas of lipid deposition were detected in 32 of 36 specimens (89%) and could be distinguished from fibrous plaques. Histologically evident calcium deposits were detected with intravascular ultrasound in 35 of 36 specimens (97%). Measurement of plaque area was only possible in cross sections with a three-layered appearance. Quantitative analysis showed a significantly larger lumen area measured from ultrasonic images (26.3 +/- 21.3 mm2) than from histologic cross-sections (21.8 +/- 16.6 mm2, p less than 0.001), probably because of tissue shrinkage during processing for histology. A significant correlation (r = 0.96, p less than 0.001) between ultrasonic and histologic measurements of lumen areas was observed, with and a negligible interobserver and intraobserver variability. Plaque area and medial thickness correlated well with histology (r = 0.87, p less than 0.001 and r = 0.93, p less than 0.001, respectively). It appears from this in vitro study that intravascular ultrasound is an accurate technique for detection and characterization of atherosclerotic lesions. Vessel lumen area can be measured in most instances, whereas plaque area and medial thickness can only be reliably assessed in muscular arteries in which the hypoechoic media serves as a reference, and shadowing by calcium or attenuation by fibrous plaque components is absent.     

血管内支架置入治疗周围血管疾病的应用研究

目的：探讨血管内支架置入治疗周围血管疾病的应用价值。材料与方法：16例周围血管狭窄或闭塞的患者及2例外伤性周围血管损伤的患者。15例为髂动脉或股动脉动脉硬化所致的血管狭窄或闭塞，1例为左锁骨下动脉开口处动脉硬化所致的血管狭窄，1例为右肱动脉上段外伤性动脉瘤，1例为外伤性右锁骨下动－静脉瘘。16例周围血管狭窄或闭塞的患者，采用经皮穿刺溶栓治疗，球囊导管血管内成形（PTA）及血管内支架置入进行治疗，2例外伤性血管损伤的患者，采用经皮穿刺带膜血管内支架置入进行治疗。结果：18例患者经溶栓治疗，血管内成形（PTA）及血管内支架置入术治疗后，闭塞血管重新开通，损伤血管修复，血液动力学恢复正常。未发生并发症。结论：血管内支架置入治疗周围血管疾病具有较高的临床应用价值。     

血管内超声检测对冠状动脉粥样硬化斑块病变性质的应用价值——附100例报告

目的：探讨血管内超声显像（IVUS）检测对冠誊 样硬化斑块病变性质的诊断价值及其在指导介入性治疗中的作用。方法：采用IVUS检测100例冠誊 样硬化性心脏病（冠心病）患者124处冠状动脉血管段总截面积及其平均径、血管腔面积及其平均径，计算直径狭窄率及面积狭窄率，了解粥样硬化斑块的组成、分布及特性，并与同时进行的太动脉造影结果相比较。结果：IVUS检测发现偏心性斑块92处，向心性斑块32处，其中96处为严重冠状动脉病变节段，需要进行冠状动脉的介入性治疗或冠状动脉旁路移植术，冠状动脉造影（CAG）对于狭窄血管的直径及直径狭窄率的测值较低，IVUS测值与其比较有显著的统计学意义。结论：IVUS对于冠誊 样硬化斑块病变性质的检测明显优于冠状动脉造影，对冠状动脉介入手术的选择方案有着指导意义。     

Nonlinear intravascular ultrasound contrast imaging

Nonlinear contrast agent imaging with intravascular ultrasound (IVUS) is investigated using a prototype IVUS system and an experimental small bubble contrast agent. The IVUS system employed a mechanically scanned single element transducer and was operated at a 20 MHz transmit frequency (F20) for second harmonic imaging (H40), and at a 40 MHz transmit frequency (F40) for subharmonic imaging (SH20). Characterization experiments were performed with agent and tissue phantom signals acquired during transducer rotation. The suppression of transmit frequency tissue signals was achieved using a combination of pulse-inversion and bandpass filtering. H40 was found to improve the contrast-to-tissue signal ratio (CTR) by up to 22 dB relative to F20, but suffered from tissue propagation harmonics at higher pressures (>0.3 MPa). SH20 was also shown to be possible at a range of pressures (approximately 0.25 to 1.8 MPa), with tissue signals suppressed to near the noise floor. Coronary phantom experiments demonstrated the detection of agent in 1 mm diameter vessels outside a larger 4 mm diameter vessel in which the IVUS catheter was situated. These results suggest the feasibility of harmonic IVUS contrast imaging, which may have applications in coronary lumen boundary detection and vasa vasorum imaging.