楊道玲 陳靜婉 王戲丹
[摘要] 目的 應(yīng)用超聲斑點(diǎn)追蹤成像技術(shù)(STI)測(cè)量心肌梗死兔心室短軸切面各室壁節(jié)段的應(yīng)變參數(shù),探討其臨床應(yīng)用價(jià)值。 方法 選取健康成年日本大耳白兔20只,開(kāi)胸并結(jié)扎冠狀動(dòng)脈左前降支中斷血流以構(gòu)建動(dòng)物心肌梗死模型。分別在術(shù)前和術(shù)后30 min、6 h、1周各時(shí)段行超聲心動(dòng)圖檢查,測(cè)量實(shí)驗(yàn)兔室間隔與左室后壁運(yùn)動(dòng)幅度、左室射血分?jǐn)?shù)(EF)及左室短軸縮短率(FS);應(yīng)用QLAB軟件測(cè)量實(shí)驗(yàn)兔左室圓周應(yīng)變(CS)及徑向應(yīng)變(RS),觀察超聲心動(dòng)圖診斷指標(biāo)變化,取出心臟與病理診斷結(jié)果比較。 結(jié)果 心梗兔左室短軸乳頭肌水平病理組織學(xué)檢查共發(fā)現(xiàn)梗死節(jié)段63個(gè),二維斑點(diǎn)追蹤技術(shù)共發(fā)現(xiàn)異常節(jié)段53個(gè),符合率為84.1%(53/63);建模后6 h室間隔運(yùn)動(dòng)幅度、EF、FS開(kāi)始減低,且隨時(shí)間的延長(zhǎng)測(cè)值逐漸下降;建模后30 min心梗兔左室前壁、前間隔徑向應(yīng)變值減低;建模后6 h前壁、前間隔圓周應(yīng)變值減低,與徑向應(yīng)變相比,其測(cè)值變化晚于徑向應(yīng)變,差異有統(tǒng)計(jì)學(xué)意義(P<0.05)。 結(jié)論 超聲斑點(diǎn)追蹤技術(shù)可準(zhǔn)確、定量評(píng)價(jià)心臟節(jié)段性室壁運(yùn)動(dòng)異常,消除傳統(tǒng)超聲心動(dòng)圖僅能評(píng)價(jià)心臟整體室壁運(yùn)動(dòng)及心功能變化的缺點(diǎn),二者結(jié)合可充分發(fā)揮各自優(yōu)勢(shì),提高心肌梗死診斷的準(zhǔn)確性和敏感性。
[關(guān)鍵詞] 兔;心肌梗死;斑點(diǎn)追蹤;心肌應(yīng)變
[中圖分類號(hào)] R541.4? ? ? ? ? [文獻(xiàn)標(biāo)識(shí)碼] B? ? ? ? ? [文章編號(hào)] 1673-9701(2022)14-0025-04
Application value of speckle tracking imaging in measuring strain parameters of each ventricular wall segment in short-axis views of rabbits with myocardial infarction
YANG? Daoling? ?CHEN? Jingwan? ?WANG? Xidan
Department of Ultrasound,Jinhua Hospital Affiliated to School of Medicine of Zhejiang University,Jinhua 321000,China
[Abstract] Objective To measure the strain parameters of each ventricular wall segment in the short-axis view of rabbits with myocardial infarction (MI) by using speckle tracking imaging (STI),so as to investigate its application value in clinical practice. Methods A total of 20 healthy adult Japanese large-eared white rabbits were selected,and the middle dissection of the left anterior descending branch of the coronary artery was opened and ligated to construct an animal MI model. Echocardiography examinations were performed before, at 30 min, 6 h and 1 week after surgery to measure the motion range of the ventricular septum and left ventricular posterior wall,left ventricular ejection fraction (EF) and left ventricular fractional shortening (FS) of the experimental rabbits.QLAB software was applied to measure the left ventricular circumferential strain (CS) and radial strain (RS) of the experimental rabbits.The changes in diagnostic indices of echocardiography were observed, and these diagnostic indices were compared with the pathological diagnosis results after the heart was removed. Results A total of 63 infarcted segments were found at the level of the short-axis papillary muscle in rabbits with MI, and 53 abnormal segments were found by the two-dimensional STI, with a compliance rate of 84.1%(53/63).The ventricular septum motion range, EF and FS began to decrease at 6 h after modeling, and the measured values gradually decreased with time. The RS values of the left ventricular anterior wall and anterior septum in rabbits with MI decreased at 30 min after modeling.The CS values in the left ventricular anterior wall and anterior septum decreased at 6 h after modeling,and the measured CS values changed later than the RS values,with statistically significant difference(P<0.05). Conclusion STI can accurately and quantitatively assess the abnormalities of segmental ventricular wall motion, which eliminates the shortcomings of traditional echocardiography which can only assess the overall ventricular wall motion and changes in cardiac function. Furthermore, the combination of the two can give full play to their respective advantages and improve the accuracy and sensitivity of MI diagnosis.DCDC1E84-EA32-4131-B731-86AA2FF19B8B
[Key words] Rabbits; Myocardial infarction; Speckle tracking; Myocardial strain
心肌梗死(myocardial infarction,MI)是由于冠狀動(dòng)脈急性閉塞,導(dǎo)致部分心肌缺血、缺氧引起心肌細(xì)胞發(fā)生不可逆性壞死,在臨床中屬于危急重癥,病死率較高。急性缺血發(fā)作后超聲心動(dòng)圖對(duì)心臟的評(píng)估包括整體收縮和舒張功能的評(píng)估及局部心肌收縮異常的評(píng)估。但是,臨床工作中對(duì)心肌梗死患者局部收縮功能的評(píng)估并非常規(guī)進(jìn)行。目前組織多普勒成像(tissue doppler imaging,TDI)和斑點(diǎn)追蹤成像技術(shù)(speckle tracking imaging,STI)可用于定量分析心臟局部收縮功能[1-2]。與TDI不同,STI無(wú)角度依賴性,可在多個(gè)方向測(cè)量心肌應(yīng)變和應(yīng)變率[3-4]。該技術(shù)不僅可區(qū)分心肌梗死初期心肌的正常段和缺血段,而且還可評(píng)估心肌梗死再灌注后心肌恢復(fù)情況。因此本研究主要目的是采用超聲新技術(shù)斑點(diǎn)追蹤評(píng)估兔心肌梗死模型,并與傳統(tǒng)超聲心動(dòng)圖比較,以期尋找一種更快、更準(zhǔn)確的評(píng)估心肌梗死超聲新方法,以幫助臨床醫(yī)生準(zhǔn)確判斷,快速治療,減少病死率。
1 資料與方法
1.1 實(shí)驗(yàn)動(dòng)物及心肌梗死模型建立
20 只健康成年日本大耳白兔,體重(3.0±0.5)kg,由金華市實(shí)驗(yàn)動(dòng)物中心提供,動(dòng)物生產(chǎn)許可證號(hào):SYXK(浙)2016-0008。麻醉后胸前區(qū)備皮、消毒,連接肢體導(dǎo)聯(lián)心電圖。栓線牽拉肋骨法打開(kāi)胸廓及心包,輕抬左心耳,在肺動(dòng)脈圓錐與左心耳交界處往下3~5 mm處雙線結(jié)扎冠狀動(dòng)脈左前降支。肉眼觀察結(jié)扎遠(yuǎn)端心肌變暗,室壁運(yùn)動(dòng)減弱甚至矛盾運(yùn)動(dòng)及心電圖提示ST段持續(xù)抬高為模型建立成功標(biāo)志。
1.2 傳統(tǒng)超聲心動(dòng)圖檢查
采用Philip EPIQ 7C專業(yè)心臟彩色多普勒超聲診斷儀,S8-3探頭。分別于建模前、建模后30 min、6 h、1周行超聲心動(dòng)圖檢查。得出兔標(biāo)準(zhǔn)左室長(zhǎng)軸切面,M型超聲測(cè)量左室收縮末期和舒張末期內(nèi)徑,得出兔左室射血分?jǐn)?shù)(ejection fraction,EF)及左室短軸縮短率(fractional shortening,F(xiàn)S);測(cè)量兔室間隔及左室后壁運(yùn)動(dòng)幅度。動(dòng)態(tài)記錄3個(gè)心動(dòng)周期的左室短軸乳頭肌水平切面二維動(dòng)態(tài)圖像,以備分析。
1.3 斑點(diǎn)追蹤技術(shù)
使用QLAB工作站,對(duì)左室短軸乳頭肌水平切面進(jìn)行脫機(jī)分析,選擇最清晰的一幀圖像進(jìn)行凍結(jié),于舒張末期勾畫出心內(nèi)膜,軟件自動(dòng)定義心內(nèi)膜及心外膜之間斑點(diǎn)追蹤感興趣區(qū)后,手動(dòng)調(diào)整感興趣區(qū)范圍使斑點(diǎn)落于所有追蹤范圍之內(nèi)。軟件自動(dòng)顯示6個(gè)室壁節(jié)段的二維應(yīng)變-時(shí)間曲線,并得出6個(gè)節(jié)段心肌的收縮期峰值圓周應(yīng)變(circumferential strain,CS)及徑向應(yīng)變(radial strain,RS)。整個(gè)圖像采集及分析過(guò)程均由一人完成。
1.4 病理檢查
實(shí)驗(yàn)結(jié)束后,處死實(shí)驗(yàn)兔,取出心臟,參照超聲心動(dòng)圖心肌節(jié)段劃分方法,于左室短軸二尖瓣水平、乳頭肌水平、心尖水平切片,行HE及MASSON染色,觀察心梗兔心肌損傷情況。
1.5 統(tǒng)計(jì)學(xué)方法
采用SPSS 24.0統(tǒng)計(jì)學(xué)軟件進(jìn)行分析,計(jì)量資料以(x±s)表示,該實(shí)驗(yàn)中多組樣本均數(shù)比較用單因素方差分析,P<0.05為差異有統(tǒng)計(jì)學(xué)意義。
2 結(jié)果
2.1 病理結(jié)果
正常兔心肌纖維排列整齊,胞質(zhì)染色均勻,細(xì)胞核位于中央,呈橢園形。見(jiàn)圖1。心梗兔心肌纖維腫脹、排列紊亂、可見(jiàn)空泡變,胞漿內(nèi)出現(xiàn)顆粒及不規(guī)則橫帶,部分梗死灶周邊可見(jiàn)肉芽組織增生,可見(jiàn)有長(zhǎng)條形的充血,散在的出血。見(jiàn)圖2。
20 只心梗兔,共發(fā)現(xiàn)梗死節(jié)段138個(gè),二尖瓣水平短軸切面47個(gè),乳頭肌水平短軸切面63個(gè),心尖部水平短軸切面28個(gè)。
2.2 傳統(tǒng)超聲心動(dòng)圖評(píng)價(jià)結(jié)果
對(duì)建模前和建模后30 min、6 h、1周共20只兔心臟彩超結(jié)果行單因素方差分析,室間隔運(yùn)動(dòng)幅度、EF、FS比較,差異均有統(tǒng)計(jì)學(xué)意義(均P<0.05),心梗后6 h室間隔運(yùn)動(dòng)幅度、EF、FS開(kāi)始減低,且隨著時(shí)間的延長(zhǎng)測(cè)值逐漸下降。見(jiàn)表1。
2.3 二維斑點(diǎn)追蹤技術(shù)評(píng)價(jià)實(shí)驗(yàn)兔左室心肌應(yīng)變結(jié)果
2.3.1 應(yīng)變曲線? 建模前兔心室短軸切面乳頭肌水平各節(jié)段徑向應(yīng)變曲線表現(xiàn)為排列較整齊,達(dá)峰時(shí)間基本一致的正向曲線,圓周應(yīng)變?yōu)檫_(dá)峰時(shí)間一致的負(fù)向曲線。見(jiàn)圖3。建模后30 min兔各節(jié)段室壁徑向應(yīng)變、圓周應(yīng)變曲線雜亂,達(dá)峰時(shí)間不一致。見(jiàn)圖4。
2.3.2 斑點(diǎn)追蹤技術(shù)評(píng)價(jià)實(shí)驗(yàn)兔左室短軸乳頭肌水平各節(jié)段室壁徑向應(yīng)變情況? 建模前兔心肌各室壁節(jié)段徑向應(yīng)變比較差異無(wú)統(tǒng)計(jì)學(xué)意義(P>0.05);對(duì)同一手術(shù)時(shí)間不同兔心肌節(jié)段徑向應(yīng)變值行單因素方差分析,建模后30 min兔左室前壁、前間隔徑向應(yīng)變值即減低,早于EF、FS變化,差異有統(tǒng)計(jì)學(xué)意義(P<0.05)。見(jiàn)表2。
2.3.3 斑點(diǎn)追蹤技術(shù)評(píng)價(jià)實(shí)驗(yàn)兔左室短軸乳頭肌水平各節(jié)段室壁圓周應(yīng)變情況? 建模前兔心肌各室壁節(jié)段圓周應(yīng)變比較,差異無(wú)統(tǒng)計(jì)學(xué)意義(P>0.05);對(duì)同一手術(shù)時(shí)間不同兔心肌節(jié)段圓周應(yīng)變值行單因素方差分析,建模后6 h心梗兔左室前壁、前間隔圓周應(yīng)變值減低,差異有統(tǒng)計(jì)學(xué)意義(P<0.05)。與徑向應(yīng)變相比,其測(cè)值變化晚于徑向應(yīng)變。見(jiàn)表3。
3 討論
左室局部收縮功能障礙與多種因素有關(guān),最常見(jiàn)的是冠狀動(dòng)脈狹窄閉塞[5]。當(dāng)冠狀動(dòng)脈狹窄大于75%或斑塊突發(fā)破裂急性血栓形成引起冠狀動(dòng)脈持續(xù)閉塞時(shí),均可導(dǎo)致心肌細(xì)胞缺血、缺氧引起急性心肌梗死[6-9]。梗死面積較大時(shí),大量心肌細(xì)胞喪失收縮功能,導(dǎo)致急性心功能不全發(fā)生。心肌細(xì)胞是不可再生細(xì)胞,梗死后壞死的心肌細(xì)胞被廣泛的纖維組織所取代,從而影響整個(gè)心功能和預(yù)后,其致死率、致殘率高。因此快速確定心?;颊咝募」K绤^(qū)域,精確量化心肌功能,可幫助臨床醫(yī)生選擇最佳治療方案。目前,超聲是診斷急性心肌梗死不可缺少的重要方法之一,因此如何能夠更加快速、準(zhǔn)確地利用超聲新技術(shù)分析室壁運(yùn)動(dòng)狀態(tài),確定梗死區(qū)域是研究的重點(diǎn)。DCDC1E84-EA32-4131-B731-86AA2FF19B8B
臨床工作中,常使用傳統(tǒng)超聲心動(dòng)圖評(píng)價(jià)心肌梗死患者心臟功能,其主要參數(shù)包括左室射血分?jǐn)?shù)(LVEF)、左室短軸縮短率(LVFS)、左室舒張末期容積(LVEDV)、左室收縮末期容積(LVESV)等,且已被證實(shí)具有參考價(jià)值。盡管LVEF、LVFS易于計(jì)算,方便獲得,但其在檢測(cè)心肌缺血中初期變化的靈敏度、特異性較低。作者在對(duì)慢性腎功能不全患者心功能的研究中發(fā)現(xiàn),慢性腎衰患者心臟EF、FS正常時(shí),慢性腎衰患者心肌縱向應(yīng)變、圓周應(yīng)變已開(kāi)始減低[10]。
本研究通過(guò)制備動(dòng)物心肌梗死模型,對(duì)實(shí)驗(yàn)兔心梗前后行傳統(tǒng)超聲心動(dòng)圖檢查,發(fā)現(xiàn)結(jié)扎兔冠狀動(dòng)脈左前降支后,即刻會(huì)出現(xiàn)節(jié)段性室壁運(yùn)動(dòng)異常,但改變較小,M型超聲心動(dòng)圖測(cè)量早期心功變化并不明顯,僅6 h后EF、FS輕微減低。因此,僅以傳統(tǒng)超聲心動(dòng)圖診斷兔心肌梗死,結(jié)果并不可靠。
心肌細(xì)胞實(shí)際上無(wú)氧儲(chǔ)備功能,缺血幾秒鐘,細(xì)胞內(nèi)氧張力就會(huì)顯著下降,因此冠狀動(dòng)脈閉塞時(shí),其對(duì)應(yīng)供血區(qū)心肌即喪失收縮功能,出現(xiàn)節(jié)段性室壁運(yùn)動(dòng)異常。所以說(shuō)節(jié)段性室壁運(yùn)動(dòng)異常是早期診斷心肌缺血特異性指標(biāo)[11-15]。斑點(diǎn)追蹤技術(shù)(STI)是在二維超聲圖像的基礎(chǔ)上,通過(guò)斑點(diǎn)匹配法及自相關(guān)搜索在心動(dòng)周期中逐幀掃描某個(gè)像素的位置,通過(guò)運(yùn)算重建心肌組織實(shí)時(shí)運(yùn)動(dòng)和變形。該技術(shù)可根據(jù)病變部位及檢查所需,獲取任意層心肌網(wǎng)絡(luò)狀感興趣區(qū)追蹤,可測(cè)量任何可視角度心肌的徑向、縱向或環(huán)形應(yīng)變及應(yīng)變率,準(zhǔn)確反映心肌細(xì)微功能的多種參數(shù)。它不受聲束方向與室壁運(yùn)動(dòng)方向夾角的影響,克服了組織多普勒(TDI)角度依賴的缺陷[16-17]。本研究組通過(guò)對(duì)比實(shí)驗(yàn)兔心梗前后心肌應(yīng)變指標(biāo)變化進(jìn)一步證實(shí)這一理論。實(shí)驗(yàn)中發(fā)現(xiàn)STI在分析心肌梗死兔節(jié)段性室壁運(yùn)動(dòng)狀態(tài)中,其準(zhǔn)確性,敏感性高于傳統(tǒng)超聲心動(dòng)圖,術(shù)后30 min即出現(xiàn)陽(yáng)性結(jié)果,冠狀動(dòng)脈分布對(duì)應(yīng)梗死區(qū)心肌節(jié)段與周圍正常心肌組織節(jié)段徑向應(yīng)變、圓周應(yīng)變比較,差異均有統(tǒng)計(jì)學(xué)意義(均P<0.05),梗死區(qū)域心肌圓周應(yīng)變值、徑向應(yīng)變值均低于正常心肌節(jié)段。
綜上所述,傳統(tǒng)超聲心動(dòng)圖可判斷兔心臟整體收縮功能,可測(cè)量兔心腔大小、容量等變化;斑點(diǎn)追蹤技術(shù)可準(zhǔn)確定位心肌梗死兔局部室壁運(yùn)動(dòng)異常部位,兩種技術(shù)結(jié)合能夠綜合評(píng)價(jià)冠狀動(dòng)脈閉塞后心臟整體及細(xì)微運(yùn)動(dòng)狀態(tài),為臨床醫(yī)生評(píng)估心臟功能提供一種可靠有效的方法。本研究尚有不足之處,二維斑點(diǎn)追蹤技術(shù)定量評(píng)價(jià)室壁運(yùn)動(dòng)狀態(tài)是建立在清晰的二維圖像基礎(chǔ)之上,圖像質(zhì)量嚴(yán)重影響其追蹤測(cè)量指標(biāo)[18-20]。實(shí)際操作中,由于兔心腔較小,心率偏快,心尖部聲窗顯示欠滿意,很難評(píng)價(jià)兔心肌縱向應(yīng)變。因此為達(dá)到實(shí)驗(yàn)的嚴(yán)謹(jǐn)性、科學(xué)性、準(zhǔn)確性等要求,本研究選用顯示較好的乳頭肌水平切面分析兔室壁節(jié)段的運(yùn)動(dòng)情況。對(duì)兔心肌的縱向應(yīng)變、旋轉(zhuǎn)應(yīng)變未深入研究。本課題組將在冠心病的進(jìn)一步研究中攻克難點(diǎn),努力改進(jìn),爭(zhēng)取達(dá)到實(shí)驗(yàn)的規(guī)范化、完整化。
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(收稿日期:2021-01-22)DCDC1E84-EA32-4131-B731-86AA2FF19B8B