犬左前降支心外膜下层心肌冠状动脉分支角度的超声初步研究

Preliminary study on left anterior descending branches angle of subepicardial coronary artery in the beagles using high-frequency transepicardial echocardiography

目的应用高频二维灰阶超声结合彩色多普勒血流成像、心肌超声造影以及组织病理技术观察健康比格犬左冠状动脉前降支心外膜下层心肌及心肌内冠状动脉分支情况,通过测量分支点角度,利用流体力学原理以及心脏舒缩运动的特点分析其分支结构特点与冠状动脉循环的关系,深入认识心肌血流灌注的特点。方法 (1)8只健康比格犬,常规动物术前准备,开胸制作心包吊篮模型;(2)应用高频超声结合彩色多普勒血流成像和心肌超声造影经心外膜观察左冠状动脉前降支(LAD)、斜角支(OB)及其心肌内分支的连接和走行方向,尤其是心外膜下层心肌内分支,采集其长轴和短轴二维超声灰阶、心肌超声造影及彩色多普勒血流实时图像,并储存;(3)图像采集后,处死比格犬,取出心脏固定后游离左心室前壁,沿LAD、OB长轴及短轴制作大体标本、组织病理切片,分别在显微镜下观察心外膜冠状动脉及心肌内冠状动脉走行、连接,并摄影存图;(4)脱机应用photoshop图像分析软件分别沿所观察血管长轴和短轴的二维超声灰阶图上于LAD、OB上段(SSOB)和下段(ISOB)走行区域选取3支心外膜下层心肌内冠状动脉血管(SIMCA),测量其收缩末和舒张末与其上级主干血管夹角角度θ(θs、θd)。同时测量大体标本或组织病理切片上感兴趣区域(ROI)冠状动脉分支角度;(5)对所有进入分析的定量资料进行正态性和方差齐性检验,近似正态分布的定量资料以x-±s表示。LAD、OB上段和下段走行区域心外膜-心外膜下层心肌内冠状动脉分支角度三者之间比较使用单因素方差分析,同一节段舒张期和收缩期分支角度两两之间比较采用配对t检验,检验水准α=0.05,P<0.05差异有统计学意义。结果 (1)二维灰阶超声、彩色多普勒血流成像及心肌超声造影观察:比格犬左冠状动脉前降支心外膜下冠状动脉分支多以锐角"旋入"心外膜下层心肌;从LAD主干近端到分支OB远端,心外膜-心外膜下层心肌冠状动脉分支夹角角度逐步减小;膈面血管绕过心尖到达左心室前壁,其分支夹角开口与左前降支在心外膜下层心肌内的分支夹角开口方向相反。(2)大体标本及组织病理切片显微镜下观察:LAD分支多以锐角进入心外膜下层心肌,并斜行于中层心肌片层间隙,在中层心肌内其反向延长线与心外膜下冠状动脉长轴略垂直;心外膜下冠状动脉分支处内弹力膜明显增厚,凸入管腔内形成内膜垫。(3)长轴切面LAD、SSOB及ISOB组间心外膜下层心肌冠状动脉分支角度两两比较,差异均有统计学意义(P<0.01),且LAD组>SSOB组>ISOB组。ISOB组内θs和θd比较,差异有统计学意义(P<0.01),LAD组和SSOB组组内θs和θd比较,差异均无统计学意义(P>0.05);短轴切面LAD组、SSOB组间心外膜下层心肌冠状动脉分支夹角角度比较,差异无统计学意义(P>0.05),LAD组、SSOB组及ISOB组内θs和θd比较,差异均无统计学意义(P>0.05)。结论 (1)心外膜冠状动脉分支成锐角进入心外膜下层心肌,角度从LAD主干至斜角支下段分支逐步减小,斜角支下段分支冠状动脉进入角度在收缩和舒张期存在明显差异。"锐角连接"更符合伯努利方程和雷诺方程原理以及心脏自身舒缩运动特点。(2)心外膜冠状动脉分支旋转进入心外膜下层心肌及随心肌旋转运动而旋转,符合心室肌壁扭转运动的生物力学特性以及冠状动脉管壁结构特点。(3)研究结果有助于进一步揭示冠状动脉循环功能的解剖学基础。(4)高频超声、彩色多普勒血流成像以及心肌超声造影技术的综合应用有助于心外膜冠状动脉进入心外膜下层心肌时角度变化和旋转运动的动态观察。

Objective To study the blood perfusion of myocardium in coronary circulation by evalu- ating the eruption angle of subepieardial coronary artery branches from beagle＇ s left anterior descending （LAD） coronary artery using transepicardial high-frequency echocardiography, Doppler flow imaging（ CD- FI）, myocardial contrast eehocardiography （MCE）, analyzing the relation between characteristic of branch and coronary circulation by principle of hydromechanics and characteristic of heart＇ special motion, and demonstrating its hemodynamics related anatomical characteristics with echocardiographic and patho-histologi- cal findings. Methods （ 1 ） Eight open-chest healthy female beagle models were used for the research. （2） Observating the connection, orientation and distribution of subepicardial coronary branches from LAD and its distal oblique branch （OB）into sub-epicardium or intra-myocardium using high-frequency transepicardial eeh- ocardiography ,2D gray scale imaging, color Doppler flow imaging （CDFI）＇ and myocardial contrast echocar- diography （MCE）. Then, the longitudinal and short-axis views of left ventricular anterior wall with epicardi- al and subepieardial coronary arteries were acquired in three successive cardiac cycles. （ 3 ） Beagles were ex- ecuted for euthanasia after eehocardiographie image collection and the heart were isolated and fixed in 6% formaldehyde solution for further patho-histological slice. （4） Observating the connection, orientation and distribution of subepicardial coronary branches from LAD and its distal oblique branch（OB） into sub-epicar- dium or intra-myocardium, and taking photos region of interesting （RO1）. （ 5 ） In 2D gray-scale, CDFI , MCE and photos of patho-histological slice , longitudinal and short axis views, the LAD, superior segments and inferior segments of oblique branch （SSOB ,ISOB） as well as three selected subepicardial intra-myocar- dium coronary artery（SIMCA） branches were displayed, and the eruption angles between branches and the main trunk of superior coronary arteries were measured using a dedicated Photoshop software at the end of systole and end of diastole （ i. e. ,0s, 0d） , respectively. （6） All statistical analyses were performed with SPSS13.0 software, all measurement data were expressed as ：~ ＋ s, when compared means among many groups we adopted One-Way ANOVA test, and paired samples t Test was used for difference identification of angles of branch point in end of systolic and end of diastolic phase. The criteria was defined as ct = 0.05, a value of P 〈 0.05 was considered significant. Results （ 1 ） Echocardiographic findings ： the branches of LAD penetrated rotationally into subepicardium from epicardial main trunk with an acute eruption angle either in longitudinal or short-axis section. The angles were reduced from the proximal trunk of LAD to distal part of its branch in the longitudinal sections except the cross sections ; The eruption angles of intramural LAD bran- ches at left ventricular apex were almost 90~ for less myocardial movement;The angles of some coronary arter- y branches from the vessels of inferior part at apex were obtuse with the reversed originated angle of these branches. （2） Patho-histological findings ： the branches of LAD penetrated vortically into subepicardium from epicardium with acute eruption angle, and the prolonged lines of extension arteries in longitudinal direction was perpendicular obliquely to the longitudinal lines of its superior vessels in the middle myocardial layer of left ventricular anterior wall. At the bifurcation point of LAD into subepicardium, a proliferated endarterium cushion was noticed and projected into the chamber of vessels. （3）Eruption angle measurement： in longitu- dinal sections： the angle differences were statistically significant between LAD, SSOB and ISOB （P 〈 0. O1 ）, and angles decreased along LAD（ i. e. , LAD 〉 SSOB 〉 ISOB）. Otherwise, there was no the significant differ- ence of 0s and 0d between LAD and SSOB except the 0s and 0d at ISOB（P 〈0.01）. In short-axis sections： There were no significant eruption angle differences at LAD, SSOB, ISOB （ P 〉 0.05 ）. There was no signifi- cant difference of angle measurements between two observers （P 〉 0.05 ）. Conclusions （ 1 ） The branches of LAD erupted into subepicardium from epicardium in an acute angle with gradual decrease from proximal trunk of LAD to the distal part, and a significant angle difference existed between the end systole and end diastole at ISOB. connecting by acute angle between trunk of superior vessel and interior branch was in line with Bernoulli equation, Reynolds＇ equation and characteristic of heart＇ specially systolic and diastolic motion. （2）The branches of LAD erupted into subepieardium from epicardium vortically and revolved with myocardium＇ rotation,which accorded with the bio-mechanic characteristic of heart＇ s rotation or twist motion and anatomical characteristics of coronary artery. （3）The morphological findings from this study will foster the better understanding of the anatomic fundament of coronary artery circulation function. （4） The eombinat- ed application of high-frequency transepieardial echocardiography, CDFI and MCE was helpful to contiguously observe the connection, orientation and distribution of subepicardial coronary branches from LAD and its distal oblique branch （OB）into sub-epicardium or intra-myocardium, and revolving with myocardium＇ rotation.