血管内超声诊断冠状动脉临界病变的临床研究

Coronary heart disease （CHD） is primary cause for death of adult patients with heart disease in China， and its incidence rate and mortality rate are increasing year by year. Thus， correct diagnosis of CHD is very important for active treatment and improvement of prognosis[1]. Though coronary angiography （CAG） is regard as "gold standard"， but it belongs to two-dimensional plane measurement and can only observe inner appearance of lumens， not inner appearance of vascular walls. Intravascular ultrasound imaging （IVUS） can observe both appearances mentioned above and assess dimension of vessels through observing tunica media and tunica externa， and calculate the practical stenosis rate， it plays a role that cannot be substituted by CAG.1　Subjects and Methods1.1　SubjectsA total of 60 cases [36 men and 24 women， 40～77， （54.1±6.24） years old] with coronary borderline lesions （stenosis rate 50%～70% of CAG by eye measure ）underwent measurements of CAG and IVUS. All subjects were consistent with standards of naming and diagnosis of International Society of Cardiology and World Health Organization. Patients with following diseases were excluded： severe liver or renal diseases， malignant tumor， big trauma in near period， autoimmune diseases， cerebrovascular diseases etc.1.2　Methods1.2.1　The 5F multi-functional visualization catheter and 6F JR4.0， JL3.5 catheter were applied in CAG. Left and right coronary arteries were visualized in every position： left coronary artery was visualized in left-anterior oblique view 50°， head 30° position， left-anterior oblique view 50°， foot 30° position， right-anterior oblique view 30°， head 30° position， right-anterior oblique view 30° and foot 30° position in turn; right coronary artery was visualized in left-anterior oblique view 50° and right-anterior oblique view 30°。 Length of vascular with lesion， vascular dimension at the most narrow place of lesion， dimensions of proximal and distal segments of lesion were measured by workstation of QCA （quantifying stages of CAG） in later period. Mean value of multiple-angle imaging of a vessel was regard as result of stenosis degree of the vessel. Meaningful lesion was defined as stenosis >50% in left main coronary artery （LM） and left anterior descending artery （LAD）。 Mean dimension of consulted vessel= （proximal dimension of vessel with lesion+distal dimension of vessel with lesion）/2， diameter stenosis rate= [（mean dimension of consulted vessel-vascular dimension at most narrow place of vessel with lesion）/mean dimension of consulted vessel]×100%.1.2.2　Ultrasound Imaging System （Boston Scientific Company） was used for IVUS， and imaging guidewire was Atlantis SR Pro， catheter was 40 MHz phase array type. Outer dimension of probe was 3.6F， and frequency of probe was 40 MHz. Area of cross section measured by IVUS was presented as mm2. Indexes for measurement were maximal and minimal dimensions of total section area of vessels， maximal and minimal dimensions of lumens， total section area， lumens area. The instrument automatically calculated percentage of plaque area. According to characteristics of echo in IVUS， plaques were divided into soft plaque， fibrous plaque， calcified plaque and mix plaque.Characteristics of echo in IVUS， plaques were divided into soft plaque， fibrous plaque， calcified plaque and mix plaque.Plaque area= lumens area of reference vessel- lumens area of vessel with lesion.Percentage of plaque area= plaque area/ lumens area of reference vessel×100%.Mean dimension of vessel= （maximal + minimal total section area or lumens area of vessel）/2. Diameter stenosis rate of vessel=[（mean diameter of reference vessel - mean diameter of lumens in vessel with lesion）/mean diameter of reference vessel] ×100%.1.3　Statistical analysisThe SPSS 13.0 software was used to perform statistical analysis. Measurement data were presented as mean value±standard deviation （x-±s）， and paired t test was performed in measurement data. Chi-square test or exact propability was performed in enumeration data. P<0.05 was regard as possessing significant difference.2　ResultsThe differences of detection rate of plaque calcification and plaque rupture were no significant between CAG and IVUS（P>0.05）。Compared with CAG， mean diameter stenosis rate of each coronary artery [LM： （65.3l±7.81） % vs. （75.28±8.89） %，proximal segment of LAD： （66.67±8.79） % vs. （78.89±7.88） %，middle-distal segment of LAD： （71.55±6.83） % vs. （75.3l±7.81） %， P<0.01 all] significantly increased in IVUS. Underestimation of different degrees of coronary artery stenosis existed in CAG， especially in proximal segment of LAD， was shown in Table 1.Table 1　Comparisons of different characteristics between CAG and IVUS3　DiscussionThere are two analytic methods for coronary artery stenosis. One is method of routine CAG， QCA determined stenotic degree of vessel and length of vessel with lesion through calculating vessel diameter and percentage of stenotic area. The other method is application of IVUS[2,3]. It can take cross sectional image of coronary artery， observe structure of vessel wall and appearance of vessel lumens， accurately measure vessel diameter and analyzed quality of plaque in vessel and stenosis degree. IVUS is a new diagnostic method combining noninvasive ultrasound techniques and invasive cardiac catheter technique. It can scan and take cross sectional image of vessel wall in 360°view， display tiny anatomic structure of vessel. It can analyze plaque quality and stenosis degree of vessel， and appearance of vessel walls. Eccentric plaque was defined as plaque occupied a part of vessel circumference or dimension of thickest site of plaque was two or more times than that of thinnest site; concentric plaque was defined as plaque occupied whole circumference of vessel and dimension of thickest site was less two times than that of thinnest site. Soft plaque possessed lower echo than those of tunica externa and surrounding tissues; fibrous plaque possessed similar echo with tunica externa and surrounding tissues， and there's no echo shadow behind it; calcified plaque possessed higher echo than those of tunica externa and surrounding tissues， and there's echo shadow behind it. IVUS can more directly determine injury of mucous membrane in vessel[4].The result of our study indicated that coronary artery stenosis rate diagnosed by IVUS were significantly higher than that of CAG， especially in proximal segment of LAD. Its possible causes were ① In CAG， nearby normal vessel with plaque and relative stenosis was taken as consulted; ② CAG showed two-dimensional structure of lumens while IVUS scanned and took cross sectional image of vessel wall in 360° view， especially there is compensatory dilation in atherosclerotic vessel; ③ for some vessels that CAG cannot detect， whereas IVUS can make up.Although CAG still regarded as gold standard nowadays， but this study indicates that IVUS possesses its advantage， can make up for shortage of CAG， so must be spread in clinic.【参考文献】[1]郭继鸿，王立群。 冠状动脉内超声显像与造影对冠脉病变检出的意义[J]. 中国实用内科杂志，2001， 21（8）：464-467.[2] 王连生，杨志健，马根山，等。 血管内超声对冠状动脉中度狭窄处理的指导作用及安全性评价[J]. 中国超声医学杂志，2002， 18（3）： 199-202.[3] 翁建新，刘　强， 左辉华，等。 急性冠脉综合征血管内超声斑块显像与血清淀粉样蛋白A妊娠相关血浆蛋白A表达的相关研究[J].心血管康复医学杂志，2011,20（2）：117-120.[4] De Scheerder I， De Man F， Herregods MC， et al. Intravascular ultrasound versus angiography for measurement of luminal diameters in normal and diseased coronary arteries[J]. 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