急性心肌梗死MR心肌灌注成像实验及临床应用研究

目的采用MR首过灌注成像评价急性心肌梗死心肌组织血流灌注特点及治疗效果。方法急性心肌梗死模型犬9条,对照组犬4条;心肌梗死患者16例,正常对照组8例。采用磁化准备梯度回波（turboFLASH）序列行MR首过灌注及延迟成像扫描,绘制左心室各壁心肌信号强度-时间曲线,分析病变心肌信号强度-时间曲线特点。结果心肌梗死模型犬及未溶栓治疗组心肌首过呈低强化,延迟扫描信号强度高于正常心肌,曲线上升时间、上升斜率、峰值时间和对比增强率明显低于正常心肌。心肌梗死溶栓再灌注组首过及延迟均强化,延迟扫描时病变心肌信号强度高于正常心肌,信号强度-时间曲线仅曲线上升时间延长。心肌梗死模型犬和未溶栓治疗组病变心肌峰值信号强度较正常心肌明显降低,分别为正常心肌的(44.8±13.0)%和(54.5±12.0)%,溶栓再灌注组病变心肌峰值信号强度可达正常心肌的(90.8±13.0)%。结论turboFLASHMR心肌首过灌注成像有助于评价心肌血流灌注及溶栓疗效。     

梗死心肌的MRI评价及病理对照实验研究

目的　通过MR影像与病理对照的方法明确心肌梗死后 7～ 10dMRI延迟强化区与梗死心肌的关系 ,以期为MRI评价心肌活性提供病理依据。方法　利用 6只猪无再灌注和再灌注的心肌梗死模型 ,行短轴面MR心肌延迟强化扫描。扫描结束后将心脏离体 ,沿短轴面将心脏切成断面行氯化三苯基四氮唑 (TTC)染色。比较心肌梗死区和正常对照区的延迟强化信号强度的差异 ;比较相应层面的MRI延迟强化区和TTC染色所示梗死区的关系。结果　在心肌梗死的 7～ 10d ,无论有无再灌注 ,MR延迟强化扫描均可见心肌梗死区信号较正常对照区明显升高 ,无再灌注组梗死区信号( 2 0 81± 6 49)是正常对照区 ( 2 68± 1 10 )的 7 76倍 (t =11 68,P <0 0 1) ,再灌注组梗死区信号( 14 2 8± 1 64)是正常对照区 ( 1 44± 0 52 )的 9 92倍 (t =3 1 69,P <0 0 1) ;无再灌注组的延迟强化区[占同层面左室面积的百分率为 ( 15 49± 6 0 7) % ]与梗死心肌 [( 14 95± 7 3 6) % ]一致 (t =-0 78,P>0 0 5) ,再灌注组的延迟强化区 [( 12 52± 5 93 ) % ]包括梗死区 [( 11 13± 5 81) % ]和梗死周围区 ,过度估计梗死心肌范围约 12 47% (t =-14 48,P <0 0 1)。结论　在心肌梗死的 7～ 10d ,MR延迟强化扫描可较准确地反映梗死心肌的范围     

磁共振心肌灌注成像急性心肌梗死的实验研究

目的 研究猪急性心肌梗死的首过灌注和延迟时相MRI特点.方法 猪心肌梗死模型12只,均进行快速梯度回波序列(FGREET)首过灌注扫描及反转恢复梯度回波序列(MDE)延迟时相扫描.扫描后处死,分析心肌首过灌注和延迟时相特点,并与病理检查对照.结果 9例(75%)首过灌注时梗死心肌表现为灌注减低,其信号强度显著低于周围心肌,10例(83.33%)延迟期梗死心肌表现为延迟强化,而正常心肌信号强度下降,低于梗死心肌.结论 MR心肌灌注成像可有效检测急性心肌梗死的梗死心肌以及其程度和范围.     

正常成人心肌MR灌注成像的初步研究

目的: 探讨利用MR心肌首过灌注及延迟增强方法评价正常成人心肌灌注特点的价值.材料和方法: 对15例正常志愿者进行MR首过灌注、延迟增强成像及cine-MR成像检查,绘制时间-信号强度曲线.结果: 正常左室前、侧、后壁心肌和室间隔时间-信号强度曲线上升时间,曲线上升斜率,对比增强率及延迟信号强度无统计学差异.结论: 正常成人心肌MR灌注成像的特点对利用MR心肌灌注成像诊断心肌病变具有重要的价值.     

猪心梗模型MRI心肌首过灌注实验研究

目的 探讨缺血心肌灌注以及局部心肌的存活情况. 方法 制备成功的10只猪心梗模型分别于术前及术后24 h、72 h及1周行MRI心肌首过灌注检查,MRI检查完后处死实验猪,行TTC染色及病理检查.结果 符合实验研究10只猪术前MRI心肌首过期灌注未见灌注减低或缺损,术后8只见心肌灌注缺损和减低,灌注缺损区其灌注曲线未见明显的灌注峰,在正常心肌灌注峰值时间为低灌注表现,后期曲线呈逐渐上升表现;灌注缺损周围心肌其灌注曲线峰值信号强度低于正常侧壁和下壁心肌(P<0.05);灌注曲线峰值时间较正常侧壁和下壁心肌延迟(P<0.05).灌注缺损区TTC染色及病理均可见心肌坏死,灌注减低区见间质局灶水肿、心肌纤维水肿变性. 结论 MRI心肌首过灌注成像结合灌注曲线分析可以评价心肌活性和缺血情况.     

磁共振心肌灌注成像及心肌活力分析诊断急性心肌梗死的价值

目的:研究磁共振心肌灌注成像及心肌活力分析在诊断急性心肌梗死中的价值。方法:选择37例急性心肌梗死患者作为观察组,同时选出37例无心血管疾病的正常志愿者作为对照组,均行灌注成像和心肌活力分析,观察2组相应心肌信号强度平均值、首过最大上升斜率及首过时间。结果:磁共振心肌灌注成像延迟期观察组梗死心肌的信号强度平均值为73.23±35.24,对照组正常心肌(对应观察组梗死区)为17.99±8.15,2组对比差异具有统计学意义(P<0.01);观察组梗死心肌的首过最大上升斜率平均值为32.85±20.69,对照组正常心肌(对应观察组梗死区)为44.68±23.60,2组对比差异具有统计学意义(P<0.01)。观察组患者心肌梗死区首过时间平均为(5.04±1.74)s,对照组正常心肌(对应观察组梗死区)为(2.82±1.82)s,2组对比差异具有统计学意义(P<0.01)。结论:磁共振心肌灌注成像及心肌活力分析可用于诊断急性心肌梗死。     

磁共振心肌灌注成像及延迟成像检测冠心病心肌缺血的临床研究

目的 探讨MR心肌灌注成像(PI)联合延迟扫描成像检测梗死心肌的价值.资料与方法 对18例经冠状动脉造影证实有冠状动脉狭窄的患者行MR首过心肌灌注及延迟扫描成像检查.分别计算低灌注节段组和正常灌注节段组灌注信号强度参数前后信号增强最大强度(SIp)、相对峰值强化率(SI%)、累积信号强度(ASI)、对比剂到达时间(t0)、强化峰值时间(t1),对比剂流入到强化峰值50%s时间(t1/2)、对比剂流入到强化峰值时间(Tp)、最大曲线上升斜率Slope(α).观察心肌低灌注节段,并与DSA结果比较.测定延迟扫描强化区与无强化区的信号强度值,计算强化区体积占心肌总体积的比值,分析强化区体积所占心肌总体积的比值与每搏输出量之间的相关性.结果 (1)心肌首过灌注成像与冠状动脉造影两种方法存在较好的相关性(X2=21.0,P＜0.05,r=0.53).(2)正常灌注节段组各参数分别为:SIp(162.8±30.2),SI%(136.2±6.6),ASI(931.4±98.1),t0(16.2±1.1),t1/2(18.5±1.4),t1(22.4±1.4),Tp(9.7±1.7),Slope(α)(16.1±1.7).低灌注节段与正常灌注节段参数SIp、SI%、ASI、t1、Tp、Slope(α)差异有统计学意义(P＜0.05),t0、t1/2差异无统计学意义(P＞0.05).SIp、SI%、Tp、Slope(α)为反映心肌首过灌注TIC的特异性参数,能敏感地反映缺血的程度.(3)延迟强化后,异常延迟强化区信号值(616.6±38.4)与正常延迟强化区信号值(304.0±69.0)差异有统计学意义(P＜0.05).异常延迟强化区体积比与患者每搏输出量呈负相关(r=-0.977,P＜0.05).结论 MR心肌PI通过灌注参数的分析可以评估梗死心肌的程度,参照延迟增强的结果,可确定梗死心肌,并计算梗死面积,是对心肌血供情况的最直接反映.     

心肌灌注MRI和MR电影在急性冠状动脉综合征中的应用

目的　评估心肌灌注MRI和MR电影在急性冠状动脉 (简称冠脉 )综合征中的应用价值。方法　急性冠状动脉综合征患者 5 5例 ,再灌注治疗 3～ 6个月后 ,进行心脏MR影像检查。真正快速稳态梯度序列 (FIESTA)用于观察心肌运动 ;快速梯度回波序列 (FGREET)用于观察首过时相心肌灌注的MRI特征 ;反转恢复梯度回波序列 (MDE)用于观察延迟时相心肌灌注MRI特征。结果5 5例中 38例患者可见位于心内膜下心肌的首过灌注缺损 ,其信号强度相对值显著低于周围心肌。心肌灌注延迟时相MRI示 5 1例患者心室壁内存在不同范围的强化灶 ,其信号强度值是周围心肌的4 36倍 (t=1.6 9,P <0 .0 5 )。心室壁内所存在的延迟强化灶范围和信号均匀程度与心室壁运动能力显著相关 (非标准相关系数分别为 - 4 2 195、- 10 1 75 0 ,标准相关系数分别为 - 0 377、0 4 2 5 ;t分别为- 5 735、- 5 4 4 5 ,P值均 <0 .0 0 1)。结论　梗死心肌于MR心肌灌注延迟时相呈现显著强化。通过综合分析延迟强化 ,运动能力显著降低和可能存在的首过灌注缺损 ,可以更有效地识别梗死 (或瘢痕 )心肌     

急性心肌梗死的CT灌注实验研究

目的　探讨CT灌注扫描检测急性心肌梗死病灶的可靠性 ;定量研究急性梗死灶伽玛(γ)曲线的参数特征 ,以期指导临床对于冠心病及心肌梗死的分析、诊断。方法　使用ImatronC 15 0型电子束CT(EBCT) ,灌注扫描程序 ,扫描对比剂流动模型 ,观察拟合的曲线以及在不同灌注量中的变化 ;选取 6只健康家犬 ,麻醉后经开胸手术 ,结扎左冠状动脉前降支和旋支分支 ,使左心侧壁部分梗死。通过EBCT灌注扫描 ,观察正常和梗死区的形态及其灌注曲线变化 ,分析正常和梗死区的曲线特征和各参数 ,经统计学处理 ,提出其差异和鉴别点。有 2只同时经单光子发射体层计算机(SPECT)扫描 ,所有标本经氯化三苯基四氮唑 (TTC)染色处理 ,与扫描图像比较 ,并通过光学显微镜和电子显微镜检查证实。结果　不同灌注量的模型扫描曲线上升斜率不同 ;犬心肌的正常灌注曲线为一上升稍快 ,继之平缓下降的γ 曲线 :其上升时间约 10～ 13s,上升CT值约 34～ 37HU ,峰值CT值约 70～ 81HU。而梗死心肌的上升时间延长 ,平均 19 9s左右 ,上升CT值和峰值CT值降低 ,平均分别为 2 0 0和 5 3 8HU ,与正常心肌比较差异有显著性意义 (P <0 0 5 )。结论　正常与梗死心肌的灌注曲线有显著性差异 ,CT灌注扫描能够检测、发现心肌梗死病灶     

Gd-DTPA动态增强MRI评价心肌微血管损伤

目的：探讨Gd-DTPA动态增强MRI评价心肌微血管损伤的可行性。方法：制作急性犬心肌梗死动物模型，在活体上用放射微球^99Tc—MAA测量心肌血流量，0．5％伊文蓝染色区分缺血心肌；心脏离体后用3％TTC染色区分梗死心肌，SP免疫组化染色观察心肌微血管并计算微血管体积分数。犬离体心脏左冠状动脉插管后作MRI平扫及Gd—DTPA动态增强扫描，测量正常、缺血和梗死心肌的信号强度，绘制时间-信号强度曲线。结果：在T1WI上，心肌信号强度无明显差异；在T2WI上，病变心肌信号强度较正常增高；Gd-DTPA灌注动态增强扫描，正常心肌时间-信号强度曲线呈下降形，危险心肌呈上升形，梗死心肌呈平直形，灌注晚期病变区呈明显环状强化。正常、危险和梗死心肌血流量、微血管体密度差异显著。结论：急性心肌梗死后心肌间质水肿、心肌含水量增加致T2WI信号增高。Gd-DTPA动态增强时间-信号强度曲线上升的斜率及峰值可以反映心肌微血管损伤及组织水肿的程度。     

Myocardial perfusion

Noninvasive cardiac magnetic resonance (CMR) imaging has progressed rapidly over the past few years and will most likely become an integral part of the diagnostic workup of patients with known or suspected coronary artery disease (CAD). In this article the rationale for using perfusion-CMR is discussed, followed by a summary of current state-of-the-art perfusion-CMR techniques that addresses pharmacological stress, monitoring, pulse sequences, and doses of contrast media (CM) for first-pass studies. In the second part, unresolved aspects of perfusion-CMR, such as the lack of fully established and validated imaging protocols, are discussed. The optimum pulse sequence parameters, required cardiac coverage, analysis algorithms, criteria for data quality, and other aspects remain to be defined. Furthermore, since expertise in perfusion-CMR is not yet widely available, training of physicians and technicians to perform perfusion-CMR according to recognized standards is an important future requirement. In the last part of the review, some ideas are proposed to improve the management of patients with known or suspected CAD. This involves making a shift from a "reactive" strategy, in which patients are typically approached when they are symptomatic, to an "active" strategy, in which perfusion-CMR is performed for early detection of high-risk patients so that revascularizations can be performed before potentially deadly infarcts occur. An ideal test for such an active strategy would be highly accurate, reliable, safe (and thus repeatable), and affordable. Large multicenter trials have shown that in experienced centers perfusion-CMR is reliable and repeatable, and it is hoped that future studies will demonstrate its cost-effectiveness as well.     

Myocardial viability

This article reviews various means to assess myocardial viability by imaging, and provides recommendations for current clinical practice. This article also discusses future directions in assessing myocardial viability.     

Myocardial scintigraphy

Results of myocardial scintigraphy in 103 individuals are reported. This test method was introduced by the authors in 1973; ¹³¹Cs chloride served the purpose of tracer. Beside a group of 17 control individuals, 63 patients with myocardial infarction, 9 with myocardiosclerosis, and 14 with other affections were tested. The normal scintigram in fullface, profile, and left half-profile positions of the patient is first described, then the typical picture of these same positions in infarctions with anterior and posterior localizations, and also in myocardiosclerosis of various origin.The valuableness of the new radioisotope test method has been duly stressed. It affords direct and precise information about the localization and the extensiveness of the morbid process which has led to cicatricial alteration in the heart muscle.     

Myocardial reinfarction]

A total number of 1924 patients were treated for acute myocardial infarction (AMI) at the Clinic for Urgent Medicine at the Military Medical Academy during the period of seven years (1991-1997). These myocardial infarctions were at different locations, the mean age of patients was 63.7 +/- 6.2, in male patients 1192 (61.9%) and 732 (38.1%) in female ones. Out of that number of patients, 406 (21.1%) had recurrent myocard infarction (RMI), 254 (62.6%) males and 152 (37.4%) females, of average age 64.8 +/- 8.3 years. Statistically, no significant differences were observed in those two groups of patients, concerning their age, location of myocardial infarction and administration of fibrinolytic therapy. There were, however, significant differences concerning the complications, primarily cardiac insufficiency, malignant arrhythmias, AV block II0 and III0, applications of temporary or permanent pacemaker and finally mortality. During intrahospital phase of treatment, in the first few months, obtained results revealed that the patients suffering from RMI had multiple and serious complications and that cardiac insufficiency was the main cause of high mortality rate in those patients.     

Myocardial scintigraphy.

Results of myocardial scintigraphy in 103 individuals are reported. This test method was introduced by the authors in 1973; 131Cs chloride served the purpose of tracer. Beside a group of 17 control individuals, 63 patients with myocardial infarction, 9 with myocardiosclerosis, and 14 with other affections were tested. The normal scintigram in full-face, profile, and left half-profile positions of the patient is first described, then the typical picture of these same positions in infarctions with anterior and posterior localizations, and also in myocardiosclerosis of various origin. The valuableness of the new radioisotope test method has been duly stressed. It affords direct and precise information about the localization and the extensiveness of the morbid process which has led to cicatricial alterations in the heart muscle.     

Myocardial contraction bands

Pathological contraction bands affecting myocardial cells are observed in many different human conditions and in different experimental models. Their morphology was defined long ago but we need to understand the pathogenesis and functional meaning. A distinction between different histological forms of contraction bands and their quantification in a large spectrum of human diseases (262 cases) and a normal population sample where death was due to various types of accidental death (170 cases) produced the following conclusions: 1) The term “contraction band necrosis”, as used presently, is ambiguous and should be reserved for a specific morpho-functional entity induced experimentally by intravenous catecholamine infusion and seen in equivalent human cases with pheochromocytoma. 2) In human pathology it may represent a sign of adrenergic stress linked with malignant arrhythmia/ventricular fibrillation. 3) Beyond a histological threshold of 37 ± 7 foci and 322 ± 99 myocells/100 mm², the lesion may indicate sympathetic overdrive in the natural history of a disease and associated arrhythmogenic supersensitivity. 4) The detection of few pathological contraction bands in normal subjects in some types of accidental death correlates with the survival time, suggesting an agonal adrenergic stimulation to promote the cardiac pump. Received: 27 November 2000 / Accepted: 27 March 2001