武丹妮 栗平 田海燕
[摘要] 二維彩色多普勒心臟超聲因其操作的快速、便攜、經(jīng)濟(jì)等優(yōu)勢應(yīng)用于心臟功能和結(jié)構(gòu)的評價,并通過M型超聲心動圖、二維Simpson雙平面法完成心室收縮和舒張功能及心室容積的測定。但對于左心室收縮功能存在細(xì)微變化者則二維彩色多普勒心臟超聲各項參數(shù)則不能真實反映其變化。隨著現(xiàn)代超聲醫(yī)學(xué)影像的逐步發(fā)展,二維斑點追蹤成像技術(shù)(2D-STI)通過動態(tài)追蹤心肌組織實時回聲斑點運動評價左心室收縮,彌補(bǔ)了二維彩色多普勒心臟超聲的諸多不足。本文現(xiàn)就2D-STI對左心室收縮功能的研究進(jìn)展予以綜述。
[關(guān)鍵詞] 二維斑點追蹤成像技術(shù);左心室收縮功能;應(yīng)變
[中圖分類號] R541.1? ? ? ? ? [文獻(xiàn)標(biāo)識碼] A? ? ? ? ? [文章編號] 1673-7210(2019)08(b)-0045-04
[Abstract] Two-dimensional color Doppler echocardiography has been applied to evaluate cardiac function and structure for its advantages of fast, portable and economical operation. The measurement of ventricular systolic and diastolic function and ventricular volume has been completed by M-mode echocardiography and two-dimensional Simpson biplane method. However, for some special diseases or slight changes in left ventricular systolic function, the parameters of two-dimensional color Doppler echocardiography can not truly reflect the changes. With the gradual development of modern ultrasound medical imaging, two-dimensional speckle tracking imaging (2D-STI) makes up for many shortcomings of conventional two-dimensional color Doppler echocardiography. It can dynamically track the real-time echo speckle movement of myocardial tissue, and then evaluate left ventricular systolic function. This article reviews the research progress of 2D-STI on left ventricular systolic function.
[Key words] Two-dimensional speckle tracking imaging; Left ventricular systolic function; Strain
超聲心動圖因其操作方便、快速、有效、經(jīng)濟(jì)等優(yōu)勢,已成為臨床評價左心室收縮功能的首選方法[1]。但有些特殊疾病或左心室收縮功能存在細(xì)微變化時,左室射血分?jǐn)?shù)則無法真實反映左心室收縮功能變化[2]。2D-STI通過實時逐幀追蹤高幀頻二維圖像的斑點回聲定量分析,全面觀察心肌運動及機(jī)械變形能力,追蹤和測量左心室應(yīng)變及應(yīng)變率,由此可準(zhǔn)確評價左心室收縮功能變化。本文現(xiàn)將2D-STI技術(shù)在左心室收縮功能評價的應(yīng)用研究進(jìn)展進(jìn)行綜述。
1 概述
左心室收縮功能的準(zhǔn)確評估是臨床診斷和治療心臟疾病的關(guān)鍵[3],其主要評價指標(biāo)包括左心室容積參數(shù)、扭轉(zhuǎn)參數(shù)、心肌應(yīng)變參數(shù)等。應(yīng)變是指物體的變形能力,心肌應(yīng)變即心肌在心臟收縮與舒張運動時發(fā)生相對于原來形狀的變形。根據(jù)心肌運動模式,心臟的應(yīng)變包括4個部分[4],分別是縱向應(yīng)變(LS)、徑向應(yīng)變(RS)、周向應(yīng)變(CS)、旋轉(zhuǎn)角度(RA)。左心室應(yīng)變的常規(guī)指標(biāo)主要包括左心室長軸整體收縮期最大峰值應(yīng)變(GLS)、左心室軸向整體收縮期最大峰值應(yīng)變(GCS)、左心室整體扭轉(zhuǎn)度(ROT)、心臟整體收縮期應(yīng)變率(GSRs)、舒張早期應(yīng)變率(GSRe)、舒張晚期應(yīng)變率(GSRa)[5]。
常規(guī)超聲心動圖評價左室收縮功能是通過間接途徑測量心腔內(nèi)徑的縮短來反映心臟長軸方向縱向心肌和短軸方向環(huán)形心肌的收縮能力,2D-STI是基于二維灰階圖像實時追蹤不同像素心肌組織在高幀頻二維圖像中的位置,對斑點回聲定量分析,計算并描繪心肌運動速度和變化,可真實反映心室整體扭轉(zhuǎn)的程度、心肌收縮性能及心臟輸出能力[6-7]。并通過量化后的應(yīng)變參數(shù)真實反映心肌局部和整體運動功能[8],進(jìn)而無創(chuàng)性定量評價和測量左心室局部及整體收縮功能。
2 2D-STI在左心室收縮功能中的臨床應(yīng)用
2.1 對正常人左心室收縮功能的評價
構(gòu)成心臟的心肌纖維呈螺旋狀排列,內(nèi)層肌纖維呈縱向排列,中層心肌呈環(huán)形走行,而外層心肌纖維由基底向心尖部呈逆時針方向斜行。因此心臟的收縮和舒張包括縱向、徑向、周向三個空間方向的復(fù)雜機(jī)械運動[9]。Matre等[10]應(yīng)用2D-STI技術(shù)對比正常人群心臟的局部心肌應(yīng)變值,結(jié)果顯示,室間隔心肌應(yīng)變值較左室側(cè)壁、后壁相應(yīng)節(jié)段心肌應(yīng)變值高,同時對比左心室內(nèi)、外層心肌GCS,內(nèi)層心肌整體及局部不同室壁節(jié)段GCS值更高。Amundsen等[11]應(yīng)用聲納微測量法及加標(biāo)記的心臟磁共振成像技術(shù)對斑點追蹤超聲心動圖(speckle tracking echocardiography,STE)的準(zhǔn)確性進(jìn)行驗證,結(jié)果顯示2D-STI的測量數(shù)據(jù)與聲納微測量法及加標(biāo)記的心臟磁共振成像技術(shù)測量結(jié)果基本一致,證實2D-STI能夠準(zhǔn)確反映心肌運動及收縮功能狀態(tài)。李倩等[12]采用2D-STI技術(shù)測量生理狀態(tài)下實驗豬左心室內(nèi)、外層心肌的GCS,結(jié)果顯示心臟各個節(jié)段內(nèi)層心肌的GCS均高于外層心肌,以室間隔、左室側(cè)壁、左室下壁及前間隔差異最為顯著。
2.2 對冠心病患者左心室收縮功能的評價
超聲心動圖因其能夠反映心肌缺血或梗死導(dǎo)致的節(jié)段性室壁運動異常,在冠心病的診斷、預(yù)后及療效觀察等方面均有重要意義[13]。組織多普勒(TDI)極大地提高了超聲心動圖檢測節(jié)段性室壁運動及左心室收縮功能的敏感性和準(zhǔn)確性[14]。但許多學(xué)者在對心肌運動速度測量研究中發(fā)現(xiàn)TDI存在較大的角度依賴性,影響其準(zhǔn)確性[15]。2D-STI技術(shù)克服了TDI技術(shù)的缺點[16],其時間和空間分辨率均較高,通過連續(xù)觀察左室所有節(jié)段同步運動情況及心肌各個節(jié)段應(yīng)變性,獲取左心室實時全容積數(shù)據(jù),從而整體評價冠心病患者心肌收縮功能。Hua等[17]應(yīng)用2D-STI技術(shù)評估40只急性心梗建模成功的成年大鼠的左心室收縮功能,結(jié)果顯示2D-STI技術(shù)在有效反映心臟縱向變形運動的同時,還能反映徑向及周向的變形運動。Helle-Valle等[18]應(yīng)用2D-STI技術(shù)對8只急性心肌梗死實驗豬模型進(jìn)行應(yīng)變分析,結(jié)果示收縮期應(yīng)變隨LS的變化較大,隨著LS的增加,應(yīng)變沒有顯著降低。Ng等[19]對122名健康受試者及40例非ST段抬高型心肌梗死患者通過TDI技術(shù)及2D-STI技術(shù)對比分析其左心室收縮及舒張同步指數(shù),認(rèn)為2D-STI技術(shù)可能比TDI技術(shù)能夠更敏感地鑒別左室收縮不同步。Tatsumi等[20]同時應(yīng)用介入機(jī)械延遲技術(shù)、Yu指數(shù)和2D-STI技術(shù)評估心臟再同步化治療,發(fā)現(xiàn)2D-STI技術(shù)可以同時測量縱向、周向、徑向三個方向的應(yīng)變不同步指數(shù),能夠更加準(zhǔn)確地預(yù)測心臟再同步化治療術(shù)后效果。
2.3 對肥厚型心肌病左心室收縮功能的評價
肥厚型心肌?。╤ypertrophic cardiomyopathy,HCM)是一種具有遺傳異質(zhì)性的常染色體顯性遺傳心肌病,解剖特點為心室非對稱性肥厚[21]。大量文獻(xiàn)證實,HCM患者左室收縮功能減低與預(yù)后情況差、死亡率增加呈正相關(guān)[22]。Serri等[23]應(yīng)用2D-STI技術(shù)對26例非梗阻型肥厚型心肌?。∟HCM)患者及45名健康受試者進(jìn)行檢查,發(fā)現(xiàn)盡管部分患者的左心室整體收縮功能正常,但應(yīng)變的所有成分均顯著降低,縱向、徑向、周向應(yīng)變平均值較對照組明顯降低。Huang等[24]應(yīng)用實時三維超聲心動圖和2D-STI技術(shù)評價HCM患者的左室收縮和舒張功能,發(fā)現(xiàn)在HCM患者中,心肌功能障礙在非肥厚的部分也有分布,即使左室射血分?jǐn)?shù)正常,左室收縮和舒張功能也會受損。
2.4 對心力衰竭患者左心室收縮功能的評價
心力衰竭(heart failure,HF)患者有左心室運動功能不良伴LVEF的降低,李慎義等[25]研究應(yīng)用2D-STI評價急性HF患者左心室收縮功能時發(fā)現(xiàn),隨著患者LVEF降低,其左心室整體周向、縱向、徑向應(yīng)變值隨之降低,且心肌的應(yīng)變亦減低。左心室扭轉(zhuǎn)指心尖部相對于基底部的旋轉(zhuǎn),其取決于心肌收縮力,因此左心室ROT可用來評價其收縮功能。Song等[26]對HF患者心肌縱向、徑向、周向及心肌扭轉(zhuǎn)進(jìn)行定量檢測,研究表明射血分?jǐn)?shù)正常的心力衰竭(HFNEF)患者左心室收縮功能局部存在受損情況,而Toufan等[27]利用2D-STI評估HFNEF患者左心室的縱向收縮功能,發(fā)現(xiàn)HFNEF患者左心室各個節(jié)段的縱向收縮功能均減低。王銀榮等[28]研究結(jié)果與Toufan等[27]一致,且徑向及周向收縮功能均有減低。
2.5 對妊娠期高血壓患者左心室收縮功能的評價
早期識別并控制妊娠期高血壓(hypertensive disorder complicating pregnancy,HDCP)可改善母嬰預(yù)后,降低圍生期母胎死亡率[29]。2D-STI能夠發(fā)現(xiàn)HDCP孕婦早期左心室心肌結(jié)構(gòu)的細(xì)微變化。張蕾等[30]研究應(yīng)用2D-STI評價HDCP患者左心室心肌應(yīng)變,發(fā)現(xiàn)當(dāng)實驗組與對照組研究對象LVEF值均>50%時,HDCP 患者左心室長軸心肌縱向收縮期應(yīng)變較正常妊娠婦女顯著降低,舒張晚期應(yīng)變與舒張功能障礙呈正相關(guān),收縮力代償性增強(qiáng),提示在心臟整體收縮功能無明顯變化時局部心肌收縮力已出現(xiàn)減低的趨勢。Ajmi等[31]應(yīng)用2D-STI技術(shù)對比研究30例HDCP患者和30名健康孕婦的左心室的充盈壓力和應(yīng)變峰值,結(jié)果表明GLS對HDCP患者亞臨床心功能不全的檢測比其他超聲心動圖參數(shù)更敏感。
2.6 對2型糖尿病患者左心室收縮功能的評價
2型糖尿?。═2DM)控制不滿意時引起心臟微血管病變和心肌代謝紊亂,早期識別其功能變化并及時干預(yù)可顯著改善預(yù)后。楊勇等[32]研究應(yīng)用2D-STI在T2DM患者早期左心室整體與不同節(jié)段長軸收縮功能改變時發(fā)現(xiàn),T2DM患者左心室容積及LVEF在疾病早期無明顯變化,左心室整體與節(jié)段長軸收縮功能應(yīng)變值減低,提示T2DM患者左心室收縮功能的異常在疾病早期已經(jīng)出現(xiàn)。韓紅生等[33]研究應(yīng)用2D-STI評估T2DM患者出現(xiàn)心肌損害時左心室整體平均縱向應(yīng)變值從健康對照組、單純糖尿病組、糖尿病合并微血管病變組逐次減低,糖尿病合并微血管病組相較其他組別變化更明顯。
3 小結(jié)
綜上所述,2D-STI通過對心肌組織斑點回聲的追蹤,能夠早期、敏感地評價左心室整體和局部的收縮功能,為臨床各類心臟疾病的診療及預(yù)后評估提供重要參考依據(jù),然而由于二維斑點追蹤技術(shù)在測量過程中對時間和空間分辨率要求均較高,部分患者可能會在同一個心動周期內(nèi)不能有效顯示所有心肌節(jié)段同步運動狀況,可能導(dǎo)致追蹤的失敗。隨著超聲影像技術(shù)的逐步發(fā)展,2D-STI技術(shù)會逐漸完善,并且會更廣泛地應(yīng)用于心臟疾病的臨床診斷和治療效果評價。
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(收稿日期:2018-04-16? 本文編輯:任? ?念)