斑点追踪成像结合实时心肌超声造影对心肌不同灌注状态的评价

蒋媛媛,徐　洋,任卫东

(1.厦门大学附属第一医院超声科,福建厦门361001;2.厦门大学附属第一医院整形外科,福建厦门361001;3.中国医科大学附属盛京医院超声科,沈阳110004)

斑点追踪成像结合实时心肌超声造影对心肌不同灌注状态的评价

蒋媛媛1,徐洋2,任卫东3

(1.厦门大学附属第一医院超声科,福建厦门361001;2.厦门大学附属第一医院整形外科,福建厦门361001;3.中国医科大学附属盛京医院超声科,沈阳110004)

目的定量评价急性心肌梗死(AMI)经皮冠状动脉介入治疗(PCI)术前、术后左心室局部心肌功能和心肌灌注的动态变化.方法选取48例接受PCI手术治疗的1周内AMI患者(治疗组)和30例健康志愿者(对照组),采用斑点追踪成像(STI)及实时心肌超声造影(RT-MCE)技术评价PCI手术前后局部纵向应变及心肌灌注变化特征,并与单光子发射计算机断层扫描术(SPECT)结果进行相关性分析.结果PCI术前,治疗组各应变和灌注指标均较对照组明显降低.PCI术后1个月,与术前比较,除部分心肌节段心肌造影剂灌注速率无改善外,其他各指标均明显升高,差异有统计学意义(P<0.05);术后1个月,左心室局部纵向峰值应变、心肌灌注达峰强度和局部心肌血流量与单光子发射计算机断层成像术的心肌灌注量呈正相关(r分别为0.75、0.72、0.76,均P<0.05).结论STI技术结合RT-MCE技术能够准确评价AMI患者PCI手术前后的左心室局部功能和心肌灌注的变化特征.

斑点追踪成像;实时心肌超声造影;心肌梗死

网络出版地址

左心室局部收缩功能与多种因素有关,最为密切的是冠状动脉狭窄程度,临床上经皮冠状动脉介入治疗(percutaneous trans1umina1 coronary intervention,PCI)能使痉挛或阻塞的血管再通,使受损心肌部分或全部恢复功能,最终提高左心室整体收缩功能[1],正确评价PCI术前、术后左心室收缩功能对于临床评估疗效和给予指导意见具有重要意义[2].本研究联合斑点追踪显像(speck1e tracking imaging,STI)技术及实时心肌造影(rea1-time myocardia1 contrast echocardiography,RT-MCE)技术对择期PCI患者术前、术后的心肌运动和心肌灌注进行评价,并以单光子发射计算机断层扫描术(sing1e-photon emission computed tomography,SPECT)作为"金标准"进行相关性分析,旨在进一步明确PCI术后较长时间心肌的变化.

1　材料与方法

1.1一般资料

选取2010年2月至2012年2月中国医科大学附属盛京医院超声科急性心肌梗死(acute myocardia1 infarction,AMI)患者48例(治疗组),男35例,女13例,年龄52～77岁,平均(67±19)岁.其中合并高血压11例,合并糖尿病7例.同时,对48例中的30例患者行术后SPECT,以此"金标准"来判断心肌活动恢复情况.选取同期在我院门诊或住院部筛选的健康志愿者30例(对照组),男、女各15例,年龄50～74岁,平均(62±15)岁.经仔细病史询问、心电图等检查明确无器质性心脏疾病.以上采集均经被研究者本人同意.

1.2仪器与方法

采用GE Vivid7 Dimension彩色多普勒超声诊断仪,该仪器配备Echo PAC工作站,具有STI及RTMCE分析程序,同时配备M4s心脏探头,频率1.5/ 3.1 MHz,帧频80帧/s.M3s心脏探头,频率1.7/3.4 MHz,闪烁帧频23帧/s,闪烁帧数20帧,机械指数(mechanica1 index,MI)0.08.嘱受检者采取左侧卧位,平静呼吸,同步记录胸导联心电图,在采集图像时尽量保持心率的一致性.常规超声检查后记录并储存左心室两腔、三腔和四腔长轴切面,二维图像各3个心动周期以备脱机分析.

1.3统计学分析

2　结果

2.1对照组、治疗组左心室应变和心肌造影结果比较

对照组左心室节段纵向应变曲线的形态为负向单峰曲线,心肌收缩时,应变从0向负值发展,于收缩末达到最大负值;舒张时心肌延长,应变从最大负值向0基线靠近.应变值心尖部>基底部,室间隔基底部最低.RT-MCE显示:经静脉注入造影剂后,左心室各壁心肌灌注良好,心肌灌注曲线中,造影剂灌注达峰强度(perfusion peak intension,PI)、造影剂峰值声学强度(acoustic intensity peak,A)、造影剂灌注速率即微气泡平均速度(contrast agent perfusion rate,K)和局部心肌血流量(regiona1 myocardia1 b1ood f1ow,MBF)各项指标均呈现心尖部灌注略比基底部和大部分中间部高,但差异无统计学意义(P> 0.05).见表1.

治疗组应变曲线显示:心肌梗死室壁节段纵向收缩期峰值应变(the 1ongitudina1 systo1ic peak strain,SLP)值均有减低,曲线形态紊乱,规律性消失,T-SLP时间曲线峰值后移;静脉注入造影剂后,可见缺血心肌节段灌注缓慢,部分节段明显充盈缺损.灌注曲线显示:灌注强度明显减低,微泡速度减慢,局部心肌血流量减少,与对照组比较差异均有统计学意义(P<0.01).见表1,图1.

2.2PCI术后各指标比较

PCI术后1个月,应变峰值继续增高,形态略规整,灌注与术前比较,造影剂充盈略增快,除部分心肌节段K值改善不明显外,其余各指标升高均有统计学差异(P<0.05),但仍明显低于对照组,见表1,图1、2.

2.4治疗组应变指标与灌注指标同SPECT心肌灌注量的相关性分析

术后1个月,左心室SLP、PI和MBF与SPECT心肌灌注量呈正相关(r分别为0.75、0.72、0.76,均P< 0.05);T-SLP、A和K亦与SPECT心肌灌注量呈正相关(r分别为0.68、0.61、0.70,均P<0.05),但相关性不如SLP、PI和MBF.

2.5放射性分布结果

静息状态下,放射性分布减弱或明显减弱的心肌节段,在行硝酸甘油介入显像后,部分心肌节段有稀疏放射性分布或原放射性分布区域增强,可定义为存活心肌,见图3.

3　讨论

STI技术所评价的左心室整体收缩功能与心脏磁共振成像的结果大体一致,具有良好的准确性和重复性[3],此技术不受心室壁运动时产生的角度影响,能更客观地评价左心室局部心肌功能[4,5].所以,STI技术具有评估心肌局部和整体收缩功能的特点[6,7].

表1　治疗组与对照组左心室各指标比较(±s)Tab.1 Com parison of the general index between the therapy group and normal group(±s)

表1　治疗组与对照组左心室各指标比较(±s)Tab.1 Com parison of the general index between the therapy group and normal group(±s)

1)compared with contro1 group,P<0.05;2)compared with preoperation group,P<0.05.SLP,the 1ongitudina1 systo1ic peak strain;T-SLP,the 1ongitudina1 peak strain of time;PI,contrast agent perfusion of peak intensity;A,acoustic intensity peak;K,contrast agent perfusion rate;MBF,regiona1 myocardia1 b1ood f1ow.

Item Contro1 group Treatment group Preoperation One month after operation SLP(%) Bas 22.83±3.27 7.01±1.991)16.98±3.042)Mid 24.56±3.44 7.71±1.931)19.38±2.752)Apex 26.15±2.59 7.66±1.821)17.24±2.442)T-SLP(ms) Bas 116.56±4.21 152.56±4.531)126.94±3.811),2)Mid 111.66±4.11 146.31±3.471)122.34±3.011),2)Apex 106.11±3.65 151.68±3.721)125.54±3.661),2)PI(au) Bas 36.21±0.81 9.91±1.111)30.26±0.972)Mid 36.37±0.85 11.35±0.991)31.36±0.992)Apex 39.27±0.70 11.22±1.011)28.36±0.771),2)A(dB) Bas 20.88±0.52 11.01±1.081)17.26±0.872)Mid 22.86±0.59 11.31±0.911)17.69±0.732)Apex 24.45±0.61 9.28±1.041)16.14±0.901),2)K Bas 2.51±0.22 1.63±0.361)2.23±0.652)Mid 2.55±0.25 1.61±0.351)2.61±0.991),2)Apex 2.55±0.25 1.35±2.111)2.12±1.122)MBF(dB) Bas 52.74±0.49 17.86±0.91)38.36±0.651),2)Mid 58.39±0.47 18.32±0.871)34.01±0.541),2)Apex 63.57±0.42 14.97±0.911)34.33±0.701),2)

图1　治疗组1例患者AM I左心室纵向应变曲线Fig.1 Segmental left ventricular longitudina l strain curve of a AMI patient

RT-MCE技术所使用的微气泡通过肺循环到左心系统最终进入心肌组织,高机械指数可击破心肌内微泡,再转为低机械指数观察心肌血流再灌注的过程,多数学者认为实时心肌造影能真实准确地反映心肌灌注情况[8～10].

在本研究中,左心室术前梗死节段应变值均较对照组明显减低.无论对于ST段抬高患者还是非ST段抬高患者,在超声图像上均表现为纵向应变运动减弱,达峰时间延长.文献[11,12]表明两者的病死率无明显差异.梗死区心肌MCE曲线灌注强度峰值明显降低,灌注速度减慢,心肌血流量减少,与STI所得的心肌运动减慢结果一致.本研究结果显示,虽然术后1个月各项指标均较术前明显恢复,但与正常人比较仍具有一定的差距,所有患者虽行再灌注治疗,但为择期手术,其效果远不如急诊PCI术显著,再次证实了心肌细胞的坏死是不可逆的.当然,由于随访时间有限,不能完全排除部分心肌仍处于冬眠状态的可能.

图2　治疗组1例患者AM I左心室心肌灌注曲线Fig.2 Segmental left ventricular myocardial perfusion curve of a AMI patient

图3　SPECT放射性分布比较Fig.3 SPECT radioactive distribution

结果显示,PCI术后1个月各指标改善明显(P< 0.05),可能与缺血区微循环血管的改变有关.本研究中术后1个月MCE曲线显示代表局部微血管血流状态的PI、A、K和MBF值均增高,PI和MBF增高较明显,这与微循环的动态变化一致,侧枝循环的开放和顿抑心肌的激活可使局部微血管密度增加,虽然血管的扩张及侧枝循环血流远远不如正常供血量,但仍可增加一定范围内的MBF和PI,PI与微血管密度、毛细血管密度、毛细血管面积相关,但与小动脉密度和胶原含量成反比[13].由于微血管床的压力仍然很高,当微泡进入微血管时,A和K始终保持低水平增高.以上心肌灌注曲线变化同STI的纵向应变测量值一致,说明这种较长时间微循环灌注的改善能够推测心肌形变特点,而局部心肌运动状态也同样能预测微循环灌注水平.

本研究中各灌注指标随时间延长逐渐增加,证明缺血区具有一定量的微血管储备,心肌功能逐渐恢复,可认为是存活心肌.反映心肌组织形变的STI技术较少受到心脏整体运动以及邻近节段剪切力的影响[14],心肌梗死节段SLP、T-SLP随时间延长改善明显,可以认为有存活心肌存在.缺血区仍具有部分微血管完整性,本研究中各灌注指标随时间延长逐渐增加,证明缺血区具有一定量的微血管储备,心肌功能逐渐恢复,可以认为是存活心肌. SPECT用来评价心肌的灌注和细胞膜完整性,被称为检测存活心肌的"金标准".本研究48例PCI患者在术后1个月进行了核素心肌灌注断层显像检查,结果显示运动和灌注良好的心肌摄取基本正常,运动不良和灌注缺损的心肌摄取明显减弱或局部放射性分布严重减弱,与STI技术和MCE结果一致.

综上所述,应用STI技术结合RT-MCE技术可以定量评价AMI后存活心肌,能够较好反映PCI术后短期和长期疗效,两者结合评价AMI后存活心肌与SPECT心肌灌注量呈正相关,其中SLP、PI和MBF相关性良好.2种技术的结合能够准确评价心肌缺血再灌注后的心肌运动状态,为临床评估心脏功能提供了一种有效的方法.但本研究存在一定的局限性,未排除其他疾病,可能会对研究结果造成一定偏倚;仅随访至术后1个月,对于术后更长期的变化有待于进一步研究;研究样本量较小,对于研究结果可能存在一定的偏差.因此,在以后的工作中将结合三维超声,并进行组织活检,同时延长随访时间,对不同状态下的心肌灌注进行更深入的研究.

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(编辑武玉欣)

Evaluation of DifferentPerfusion StatusofM yocardium Using Speckle Tracking Imagingand Real-timeM yocardialContrastEchocardiography

JIANGYuan-yuan1,XUYang2,RENWei-dong3
(1.DepartmentofU1trasound,TheFirstAffi1iated Hospita1ofMedicine,XiamenUniversity,Xiamen361001,China;2.DepartmentofP1asticSurgery,TheFirstAffi1iated Hospita1ofMedicine,XiamenUniversity,Xiamen 361001,China;2.Department ofU1trasound,ShengjingHospita1,ChinaMedica1University,Shenyang110004, China)

Objective To quantitative1y eva1uate the 1eft ventricu1ar regiona1 myocardia1 function and myocardia1 perfusion in patients with acute myocardia1infarction(AMI)beforeand afterpercutaneouscoronary intervention(PCI)usingspeck1e trackingimaging(STI)and rea1-timemyocardia1 contrast echocardiography(RT-MCE).Methods LV 1ength-axis images were acquired in 48 patients with AMI who underwent successfu1 PCI within 1-month of AMI onset(treatment group),as we11 as 30 hea1thy individua1s as contro1 group.Conventiona1 echocardiography,STI and RTMCEweredone in both 2groupsbeforeand 1month after PCI.Thecorre1ation ana1ysisbetween theaboveindexand sing1e-photon emission computed tomography(SPECT)after PCI 1 month was a1so studied.Results Before PCI,a severe reduction in strain and perfusion was observed in treatment group compared to the contro1 group.One month after PCI,there were obvious changes in strain and perfusion index in treatment group,except partia1 myocardia1 region in K.Even.A1though there were marked1y improvement of the most index,significant differences were found between the twogroups(P<0.05).Onemonth postoperation,1oca11ongitudina1peak strainof1eftventricu1ar,myocardia1perfusionofpeak intensityand regiona1 myocardia1 b1ood f1ow were positive1y corre1ated with sing1e photon emission computed tomography amount of myocardia1 perfusion imaging (SPECT)(r were 0.75,0.72,0.76,P<0.05).Conclusion STI combined with RT-MCE can accurate1y eva1uate the regiona1 myocardia1 motion and perfusion ofAMIpatientsbeforeand after PCIand canmonitor theimprovementofmyocardia1function after revascu1arization.

speck1e tracking imaging;rea1-time myocardia1 contrast echocar diography;myocardia1 infarction

R540.45;R542.22

A

0258-4646(2016)03-0264-05

10.12007/j.issn.0258-4646.2016.03.018

蒋媛媛(1980-),女,医师,博士.

任卫东,E-mai1:renwd01@163.com

2015-07-27

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