【作者】 石键；

【导师】 杨光；

【作者基本信息】 大连医科大学 ， 影像医学与核医学， 2003， 硕士

【摘要】 研究背景：超声背向散射积分(IBS)技术通过定量测定组织的声学密度可以评价组织结构和成分的特性及其变化。心肌IBS的心动周期依赖性变化(CVIB)，可以反映心肌的内在收缩功能。由于心肌内部组织成分的不一致性，在微循环、代谢消耗、收缩功能等具有跨壁的异质性。心内膜下和心外膜下心肌CIVB的差值即跨壁梯度(TGCV)和跨壁梯度指数(TGI)可以反映心肌收缩功能的跨壁异质性。以往研究这种异质性大多局限于动物实验，而对人体心肌异质性的了解甚少，现有的研究方法(如核磁共振)大多使用较复杂，不适于临床推广。本研究的目的是利用IBS的技术特点，通过连续观测梗塞心肌在PTCA术前和术后不同时间的各项IBS指标，以及室壁增厚率(WT)的变化，研究人体梗塞心肌在成功再灌注后的跨壁异质性的情形，探讨IBS技术在心肌异质性方面的研究对心肌梗塞的临床应用价值。 资料与方法：使用带有AD-IBS联机分析软件的HP SONOS 5500型彩超仪，连接S3探头，以及光盘存储系统；同时连接心电图。对一组(n=34)急性心肌梗塞患者，在行PTCA术前、术后3天、21天、3个月分别用IBS技术检测受累心肌全层、心内膜下层、心外膜下层的IBS周期变化幅度(CVIB)，以及跨壁梯度(TGCV)、跨壁梯度指数(TGI)，并在常规超声下，测量相应节段心肌的室壁增厚率(WT)；并与另一组(n=35)正常对照者相比较。 结果：正常对照组的心肌内层CVIB比外层CVIB高，差异有显著性；TGCV=1.23±0.53(dB)，TGI=0.22±0.08(P＜0.01)。术前梗塞心肌的全层、心内膜下层、心外膜下层CVIB及TGCV、TGI、WT均较正常组明显减小，心内膜下和心外膜下心肌的CVIB值之间差异没有显著性。术后以心外膜下层CVIB恢复最快，第三天即可观察到明显的提高；心内膜下层心肌CVIB的早期恢复出现顿抑，在第21天恢复才有显著性。WT的恢复晚于全层CVIB的恢复。WT的恢复与心内膜下层心肌CVIB的恢复具有相关性(P＜0.01)。 结论: 1.人体正常心肌的CVIB具有跨壁梯度，以心内膜下心肌的CVIB比心外膜下的高，证明了正常心肌的收缩性具有跨壁异质性; 2.梗塞心肌的跨壁异质性减低，心内膜下心肌和心外膜下心肌的CVIB均下降，二者之间没有显著性差异;TGCV和TGI明显降低: 3.梗塞心肌在成功再灌注后，心肌的恢复呈现异质性，心内膜下心肌的恢复较心外膜下的慢，出现“心内膜下顿抑”。同时，全层心肌的室壁增厚率和CVIB的恢复有分离现象，WT的恢复与心内膜下心肌(而不是心外膜下心肌)的恢复呈显著的相关性。 4.IBS技术可以定量性检测人体心肌的跨壁异质性，对急性心梗患者可以提供梗塞的状况，早期评价再灌注术后的心肌的存活性及其分布，对预后的评估和确定进一步的治疗方案有重要的临床价值。作为一项方便、安全的新兴技术，IBS具有广阔的应用前景。更多还原

【Abstract】 Objective: Ultrasonic backscatter of the heart is a new application of echocardiography to evaluate the structural and functional state of myocardium. This method provides quantitative indexes of the heart’s physical properties and variations due to pathophysiological changes. The cyclic variation of integrated backscatter (CVTB) is an expression of regional intramural myocardial contractile performance and is related to contractility, but is not directly dependent on inotropic state changes. In normal conditions, myocardium has a transmural heterogeneity of contraction: contractility decreases from subendocardium to subepicardium. Available data on myocardial contractility heterogeneity during ischemia have been exclusively obtained in animal studies, because techeniques of evaluating the transmurality of ischemia are quite complicated and are often invasive. To investigate the clinical application of myocardial backscatter in studying the transmural heterogeneity of recovery in infarcted myocardium after reperfusion therapy, we evaluated the behavior of CVIB in patients with acute myocardial infarction in the different transmural layers, before and after reperfusion therapy.Methods: ’Commercially available echocardiographic equipment (HP Sonos 5500) with a S3 transducer was used in this study. IBS data were acquired and analyzed using an Acoustic-Densitornetry system. The infarcted myocardium of a group of patients with acute myocardial infarction were measured on the day before PTCA, and the third day, the 21st day, the third month after PTCA. And the CVIB in total layers, the layers of subendocardium and subepicardium and TGCV, TGI as well as the wall thickening (WT) were calculated. Another group of healthy volunteers were enrolled in this study as contrasts.Results: The normal myocardium has a trarismural heterogeneity, and the value of CVIB was greater in the subendocardium than in the subepicardium. TGCV=1.23± 0.53(dB), TGI=0.22±0.08 (P<0.01). In patients with AMI, the IBS parameters and WT were decreased before PICA, and CVIB in the subendocardium was similar to that in the subepicardium. After PICA, the recovery of CVIB in the subepicardium was quicker than in the subendocardium. The recovery of CVIB in the subendocardium behaves blunt in the early of reperfusion. WT increased more slowly than overall myocardial CVIB. TGCV and TGI decreased on the third day after PTCA, and recovered significantly since the 21st day. WT correlated closely with CVIB in the subepicardium, but not with that in the subepicardium (p<0.01).Conclusions:1. There is a transmural gradient in CVIB of normal myocardium. The value of CVIB is greater in the subendocardium than in the subepicardium. This proves that the transmural heterogeneity of myocardial contraction exists in the human heart.2. The transmural heterogeneity of infarcted myocardium decreases, and CVIB in the subendocardium is similar to,that in the subepicardium. The values of TGVC and TGI are descented.3. The transmural heterogeneity occurs during recovery of post-infarcted myocardium. The magnitude of CVIB rise more quickly in the subepicardium than in the subendocardium, with a ’subendocardial stunning’ phenomenon. In addition there is a post-infarcted dissociation between CVIB and WT recovery time. This may be explained by the transmural heterogeneity.4. Integrated backscatter can detect the transmural heterogeneity of myocardium quantitatively, and could provide the information of the recovery in infarcted myocardium after reperfusion convenientely in time. This method has a widely prospect in studying the transmural heterogeneity.更多还原