组织多普勒成像在急性心肌缺血心功能异常中的实验研究

目的 运用组织多普勒成像（TDI）技术对急性心肌缺血区域和二尖瓣环侧壁处的运动速度、移动振幅进行检测,探讨TDI在急性心肌缺血、心肌梗死中的应用价值。方法 10只开胸猪结扎左冠状动脉前降支（LAD）,通过TDI技术速度模式检测缺血区域和心尖四腔观二尖瓣环侧壁处的色泽变化及收缩、舒张期运动速度（VS,VE,VA）、移动振幅（CD,MDe,MDa）、等容收缩期时间,并与基础状态对照分析。结果 LAD结扎后,缺血区域和二尖瓣环处色泽暗淡,局部心肌色彩缺失,结扎15s时收缩期、舒张早期运动速度、移动振幅显著降低,等容收缩期时间延长。结论 TDI技术能准确反映血梗死区域运动异常,精确测定局部收缩、舒张期运动速度、移动振幅,尤其二尖瓣环处的运动能反映整体心肌的运动,为临床早期评价局部心肌缺血及心功能异常提供了一种无创性的检查手段。     

Vasopressin impairs brain, heart and kidney perfusion: an experimental study in pigs after transient myocardial ischemia

Introduction

Arginine vasopressin (AVP) is increasingly used to restore mean arterial pressure (MAP) in low-pressure shock states unresponsive to conventional inotropes. This is potentially deleterious since AVP is also known to reduce cardiac output by increasing vascular resistance. The effects of AVP on blood flow to vital organs and cardiac performance in a circulation altered by cardiac ischemia are still not sufficiently clarified. We hypothesised that restoring MAP by low dose, therapeutic level AVP would reduce vital organ blood flow in a setting of experimental acute left ventricular dysfunction.

Methods

Cardiac output (CO) and arterial blood flow to the brain, heart, kidney and liver were measured in nine pigs using transit-time flow probes. Left ventricular pressure-volume catheter and central arterial and venous catheters were used for haemodynamic recordings and blood sampling. Transient left ventricular ischemia was induced by intermittent left coronary occlusions resulting in a 17% reduction in cardiac output and a drop in MAP from 87 ± 3 to 67 ± 4 mmHg (p < 0.001). A low-dose therapeutic level of AVP (0.005 U/kg/min) was used to restore MAP to pre-ischemic values (93 ± 4 mmHg).

Results

AVP further impaired systemic perfusion (CO and brain, heart and kidney blood flow reduced by 29, 18, 23 and 34%, respectively) due to a 2.0-, 2.2-, 1.9- and 2.1-fold increase in systemic, brain, heart and kidney specific vascular resistances. The hypoperfusion induced by AVP was associated with an increased systemic oxygen extraction. Oxygen saturation in blood drawn from the great cardiac vein fell from 29 ± 1 to 21 ± 3% (p = 0.01). Finally, these effects were reversed 40 min after AVP was withdrawn.

Conclusion

Low dose AVP induced a pronounced reduction in vital organ blood flow in pigs after transient cardiac ischemia. This indicates a potentially deleterious effect of AVP in patients with heart failure or cardiogenic shock due to impaired coronary perfusion.     

Protein kinase C-epsilon is a trigger of delayed cardioprotection against myocardial ischemia of kappa-opioid receptor stimulation in rat ventricular myocytes.

Kappa-opioid receptor (OR) stimulation with a selective agonist, U50,488H (U50), known to mediate the delayed cardioprotection of metabolic inhibition preconditioning (MIP) against cell injury/death in rat ventricular myocytes, has been shown to act via protein kinase C (PKC). We attempted to identify the PKC isoform(s) that is activated, thus triggering delayed cardioprotection of MIP and pretreatment with 10 microM U50 (U50 pretreatment, UP). Release of lactate dehydrogenase and exclusion of trypan blue by isolated rat ventricular myocytes were used as indices of cell injury and death, respectively. Both MIP and UP induced translocation of PKC-epsilon, but not other PKC isoforms, -alpha and -delta, from cytosolic to membrane fractions. This was accompanied by reductions in cell injury/death induced by lethal simulated ischemia. The effects of MIP and UP were attenuated and abolished by 1 microM nor-binaltorphimine, a selective kappa-OR antagonist, administered before and during preconditioning/pretreatment, respectively. The effects were mimicked by 10 nM phorbol-12-myristate-13-acetate, a PKC activator, but attenuated by 5 microM chelerythrine, a PKC inhibitor. More importantly, 0.1 microM epsilonV1-2, a selective PKC-epsilon inhibitor administered before and during MIP/UP, also attenuated the effects of both treatments on cell injury/death and translocation of PKC-epsilon. On the other hand, 5 microM rottlerin, a selective PKC-delta inhibitor, did not alter the effects of either treatment on injury/death. The results indicate that both MIP and UP activate PKC-epsilon, leading to delayed cardioprotection in rat ventricular myocytes.     

实时心肌超声造影定量评价犬急性心肌梗死缺血心肌的实验研究

目的探讨实时心肌超声造影(RT-MCE)技术定量评价静息状态下急性心肌梗死犬缺血心肌血流量(MBF)的应用价值。方法18只健康开胸犬均结扎冠状动脉前降支3h建立急性前壁心肌梗死模型。分别于结扎前和结扎3h后经股静脉匀速推注造影剂(C3F8)行RT-MCE检查,并采集动态心尖四腔、二腔和左室长轴观图像待分析。处死犬游离心脏后,行伊文思蓝(Evansblue)和三苯基氯化四氮唑(TTC)双染色。在MCE时间-强度曲线上测量A值(平台期峰值强度)和β值(曲线斜率),计算正常心肌和缺血心肌的血流量(MBF)。结果18只犬均成功建立急性前壁心肌梗死模型。冠状动脉前降支结扎前,RT-MCE显示18只犬心肌灌注良好;结扎3h后,MCE显示受累节段心肌出现灌注减少和灌注缺损。与病理染色结果对照:肉眼观察MCE定性诊断缺血心肌的敏感性为81.8%、特异性为87.4%;诊断梗死心肌的敏感性为60.0%、特异性为89.1%;静息状态下,以MBF<6.81ml.min-1.g-1诊断缺血心肌的敏感性为100%、特异性为77.1%,受试者特征工作曲线(ROC)下面积为0.977。结论RT-MCE技术定量诊断缺血心肌优于定性诊断,MBF<6.81ml.min-1.g-1可作为判断静息状态下犬急性心肌缺血的参考阈值。     

Quantification of the spectrum of changes in regional myocardial function during acute ischemia in closed chest pigs: an ultrasonic strain rate and strain study.

The objectives of this study were to define the spectrum of regional myocardial function changes during acute ischemia in closed chest animals by using newly developed ultrasonic strain rate and strain indexes derived from regional color Doppler myocardial imaging (CDMI) velocity data. Myocardial ischemia was induced in 18 pigs either with acute total 20-second occlusions (group 1, n = 12) or graded hypoperfusion (40 to 0 mL/min, group 2, n = 6) of the circumflex coronary artery. In addition, a dobutamine challenge (5 to 10 microg/kg per minute) was performed during sustained subtotal ischemia (10 mL/min) in group 2. CDMI acquisitions with parasternal views monitored the myocardial posterior wall function. Regional radial strain rate and strain (epsilon(r)) were measured for systole, isovolumic relaxation, early diastole, and atrial filling, respectively. During total and graded ischemia, epsilon(r) profiles were consistently modified, showing a delayed onset and a decrease in regional systolic thickening as well as increased postsystolic thickening. Radial strain rate and epsilon(r) indexes decreased consistently during systole and early diastole and increased during isovolumic relaxation. End-systolic epsilon(r) could differentiate total ischemia from severe hypoperfusion (10 mL/min), decreasing from 32% +/- 8% to 16% +/- 5% (versus 60% +/- 10% at baseline). During dobutamine infusion (10 microg/kg per minute), end-systolic epsilon(r) tended to decrease from 27% +/- 5% to 18% +/- 11%, whereas postsystolic thickening increased by 2-fold (P <.05). The combined analysis of regional deformation characteristics and global cardiac event timing derived from CDMI data can identify and quantify regional function changes induced by experimental acute ischemia in closed chest pigs. This would appear to be a potentially promising new noninvasive approach to the clinical evaluation of ischemia-induced changes in segmental myocardial function.     

速度向量成像技术评价犬心肌缺血与梗死状态下左心室节段性旋转特征

目的应用速度向量成像(VVI)技术评价心肌缺血及心肌梗死状态下犬心肌旋转运动特征。方法选用杂种犬12只,在超声实时引导下结扎前降支定量制备前降支轻度狭窄(狭窄率:50%～75%)与完全闭塞模型,应用VVI技术分析前降支结扎前、轻度狭窄与完全闭塞状态下左心室旋转特征的改变。结果 12只杂种犬成功制备前降支轻度狭窄与完全闭塞模型,应用VVI技术对缺血与梗死状态下心肌旋转运动分析结果显示:(1)前降支部分结扎状态下室间隔的旋转角度与圆周应变较正常显著降低(P<0.05);径向应变与应变率较正常差异有统计学意义(P<0.05);(2)前降支完全结扎状态下:前间隔、室间隔、前壁的旋转角度与旋转速度、圆周应变与圆周应变率较正常及部分结扎状态下均显著减低(P<0.05);径向应变与应变率较正常状态下显著降低(P<0.05),与部分结扎状态下比较,差异无统计学意义。结论 VVI技术可以无创、敏感地评价心脏旋转运动。前降支部分结扎状态下心脏的旋转在个别节段已经出现减低,前降支完全结扎后,旋转角度与旋转速度较结扎前、部分结扎后均显著降低,心脏旋转可以更加敏感的反映心脏收缩功能。     

应变率显像及组织多普勒成像综合评价基因治疗慢性心肌缺血的实验研究

目的探讨应变率显像及组织多普勒显像检测基因转染治疗心肌缺血的价值。方法健康家猪16头,在冠状动脉左旋支放置Ameroid环建立慢性心肌缺血模型,4周后治疗组注射携带血管内皮生长因子B基因的重组腺病毒液,对照组注射磷酸盐缓冲液,治疗后4周取心肌进行病理学检查。观察术前、置环后2周、4周及治疗后2周、4周左心室乳头肌水平短轴观后壁心肌收缩期速度(VS)、舒张早期速度(VE)、舒张晚期速度(VA)和内、外膜速度跨壁梯度的变化。结果缺血心肌较正常心肌速度梯度减小,色彩变暗。置环后2周,左室侧后壁心肌运动速度VS、VE较术前略下降但无统计学意义,局部心肌内、外膜速度跨壁梯度则明显降低(P<0.05);置环后4周,侧后壁心肌变薄,VS、VE明显减低(P<0.05),心肌内、外膜速度跨壁梯度进一步下降(P<0.05)。治疗后2周,基因转染组较对照组心肌运动速度无显著差异,而心肌内、外膜下速度跨壁梯度明显改善(P<0.05);治疗后4周,治疗组左心室侧后壁心肌运动速度较对照组增加(P<0.05),内、外膜下速度跨壁梯度持续改善(P<0.05)。结论心内、外膜速度跨壁梯度及心肌运动速度可准确评价慢性缺血心肌基因治疗前后节段性室壁厚度变化速率和室壁运动改善的情况,前者评价局部心功能的敏感性优于后者。     

心肌缺血损伤小型猪模型内关穴位埋针后血管新生及成纤维细胞生长因子mRNA和蛋白的表达

背景:血管生成及成纤维细胞生长因子与心肌缺血损伤后修复关系密切,针刺内关防治心肌缺血损伤的机制是否与此有关尚不清楚。目的:观察内关穴位埋针对心肌缺血损伤小型猪血管新生及成纤维细胞生长因子基因和蛋白表达的影响。方法:将32只小型猪随机分为4组,采用左冠状动脉前降支结扎法建立心肌缺血模型,假手术组穿线但不结扎,内关组和膈俞组分别在造模的基础上进行内关、膈俞穴埋针治疗,模型组和假手术组不进行任何干预。结果与结论:免疫组织化学染色显示小型猪经冠脉结扎后心肌毛细血管密度降低(P<0.01),内关、膈俞穴埋针治疗7d,损伤心肌组织毛细血管密度增加(P<0.05或P<0.01),内关组优于膈俞组(P<0.05);Real time PCR和Western blot检测显示小型猪经冠脉结扎后心肌组织成纤维细胞生长因子mRNA和蛋白表达量显著增高(P<0.05或P<0.01),内关和膈俞穴位埋针治疗均可上调成纤维细胞生长因子mRNA和蛋白表达量,以内关埋针效果最明显(P<0.05)。揭示内关、膈俞穴位埋针均可通过上调成纤维细胞生长因子mRNA和蛋白的表达,增加心肌毛细血管密度,改善缺血心肌的损伤,且内关优于膈俞。     

Therapeutic angiogenesis induced by human hepatocyte growth factor gene in rat and rabbit hindlimb ischemia models: preclinical study for treatment of peripheral arterial disease

Hepatocyte growth factor (HGF) exclusively stimulates the growth of endothelial cells without replication of vascular smooth muscle cells, and acts as a survival factor against endothelial cell death. Recently, a novel therapeutic strategy for ischemic diseases using angiogenic growth factors to expedite and/or augment collateral artery development has been proposed. We have previously reported that intra-arterial administration of recombinant HGF induced angiogenesis in a rabbit hindlimb ischemia model. In this study, we examined the feasibility of gene therapy using HGF to treat peripheral arterial disease rather than recombinant therapy, due to its disadvantages. Initially, we examined the transfection of 'naked' human HGF plasmid into a rat hindlimb ischemia model. Intramuscular injection of human HGF plasmid resulted in a significant increase in blood flow as assessed by laser Doppler imaging, accompanied by the detection of human HGF protein. A significant increase in capillary density was found in rats transfected with human HGF as compared with control vector, in a dose-dependent manner (P < 0.01). Importantly, at 5 weeks after transfection, the degree of angiogenesis induced by transfection of HGF plasmid was significantly greater than that caused by a single injection of recombinant HGF. As an approach to human gene therapy, we also employed a rabbit hindlimb ischemia model as a preclinical study. Naked HGF plasmid was intramuscularly injected in the ischemic hindlimb of rabbits, to evaluate its angiogenic activity. Intramuscular injection of HGF plasmid once on day 10 after surgery produced significant augmentation of collateral vessel development on day 30 in the ischemia model, as assessed by angiography (P < 0.01). Serial angiograms revealed progressive linear extension of collateral arteries from the origin stem artery to the distal point of the reconstituted parent vessel in HGF-transfected animals. In addition, a significant increase in blood flow was assessed by a Doppler flow wire and the ratio in blood pressure of the ischemic limb to the normal limb was observed in rabbits transfected with HGF plasmid as compared with rabbits transfected with control vector (P < 0.01). Overall, intramuscular injection of naked human HGF plasmid induced therapeutic angiogenesis in rat and rabbit ischemic hindlimb models, as potential therapy for peripheral arterial disease.     

心肌缺血损伤小型猪模型内关穴位埋针后血管新生及成纤维细胞生长因子mRNA和蛋白的表达

背景：血管生成及成纤维细胞生长因子与心肌缺血损伤后修复关系密切,针刺内关防治心肌缺血损伤的机制是否与此有关尚不清楚。目的：观察内关穴位埋针对心肌缺血损伤小型猪血管新生及成纤维细胞生长因子基因和蛋白表达的影响。方法：将32只小型猪随机分为4组,采用左冠状动脉前降支结扎法建立心肌缺血模型,假手术组穿线但不结扎,内关组和膈俞组分别在造模的基础上进行内关、膈俞穴埋针治疗,模型组和假手术组不进行任何干预。结果与结论：免疫组织化学染色显示小型猪经冠脉结扎后心肌毛细血管密度降低（P〈0.01）,内关、膈俞穴埋针治疗7d,损伤心肌组织毛细血管密度增加（P〈0.05或P〈0.01）,内关组优于膈俞组（P〈0.05）;Real time PCR和Western blot检测显示小型猪经冠脉结扎后心肌组织成纤维细胞生长因子mRNA和蛋白表达量显著增高（P〈0.05或P〈0.01）,内关和膈俞穴位埋针治疗均可上调成纤维细胞生长因子mRNA和蛋白表达量,以内关埋针效果最明显（P〈0.05）。揭示内关、膈俞穴位埋针均可通过上调成纤维细胞生长因子mRNA和蛋白的表达,增加心肌毛细血管密度,改善缺血心肌的损伤,且内关优于膈俞。     

首过灌注及心肌活力分析在猪心肌梗死存活心肌诊断的实验研究

目的评估心肌灌注成像、心肌活力及运动分析MRI在猪心肌梗死存活心肌诊断中的应用价值。方法猪心肌梗死3天模型14例、3周模型12例进行心脏MR检查。BFFE用于观察心肌运动,快速梯度回波序列(T1-TFE)用于观察首过心肌灌注表现;反转恢复梯度回波序列用于观察延迟时相心肌活力表现。结果猪梗死心肌内的首过灌注诊断敏感性为92%。心肌活力分析示左心室心肌内存在不同范围的强化灶或心肌变薄,诊断敏感性为75%。心肌运动减弱节段与强化节段基本一致,诊断敏感性为92%。明显纤维化或瘢痕心肌表现为心肌变薄并始终保持低信号。结论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。     

犬急性心肌缺血左心室跨壁径向位移的超声研究

目的 观察比格犬左心室急性心肌缺血前后,节段整体和节段跨壁心肌峰值径向位移(RD)变化,量化评价节段整体和节段跨壁心肌力学特征,为缺血前后不同状态心肌构造与功能的定量研究提供基础力学数据.方法 10只健康比格犬开胸模型,结扎冠状动脉左前降支,诱导产生急性心肌缺血.缺血前和结扎冠状动脉后20min分别采集三个心动周期二尖瓣水平、乳头肌水平以及心尖水平短轴观动态组织多普勒速度图像.应用量化组织多普勒工作站,分别获取各短轴观前壁、下间壁、下壁、后壁节段整体和心内膜下心肌(subend)、中层心肌(mid)、心外膜下心肌(subepi)的RD时间曲线并测量RD及其达峰值时间.评价急性心肌缺血前后节段整体和节段跨壁心肌的RD、达峰时间、达峰时间标准差等力学参数变化及其相关性.结果 ①急性心肌缺血后,二尖瓣水平前壁和乳头肌水平前壁及心尖水平各节段整体及节段跨壁心肌的RD较缺血前呈下降趋势,其余节段呈增高趋势;②急性心肌缺血后,左心室壁12节段跨壁的RD与相应节段整体的RD相关性较缺血前发生改变,乳头肌水平及心尖水平前壁节段跨壁与节段整体的RD相关性丧失.③急性心肌缺血后,左心室节段整体和节段跨壁的心率纠正后RD达峰时间较缺血前延迟.部分节段整体的RD达峰时间延迟较缺血前差异有统计学意义(P<0.05).④急性心肌缺血后,左心室节段整体和节段跨壁心肌的RD达峰时间标准差较缺血前增大,差异有统计学意义(P<0.05).结论 节段整体和跨壁心肌峰值RD降低、相关性破坏、达峰时间延迟、达峰时间标准差增大等终点力学参数变化能够反映急性心肌缺血局部的力学异常状态.     

Modulation of apoptosis by nitric oxide: implications in myocardial ischemia and heart failure

The purpose of this review is to summarize the regulation of apoptosis by nitric oxide (NO) and to discuss the potential role that NO plays in cardiomyocyte apoptosis during myocardial ischemia/reperfusion and development of heart failure. NO is an important regulator of apoptosis within the mammalian system, capable of both inducing and preventing apoptosis, depending upon the level of NO production and environmental milieu. This bifunctional capacity is well illustrated in the heart. It appears that high levels of NO produced by inducible nitric oxide synthase (iNOS) promote apoptosis while basal levels of NO production from endothelial nitric oxide synthase (eNOS) protect cardiomyocytes from apoptosis. Since permanent loss of cardiomyocytes due to apoptosis contributes to the development of heart failure, inhibition of cardiomyocyte apoptosis may have therapeutic implications. Given its pro- and anti-apoptotic capacity within the heart, NO may serve as a valuable therapeutic target in myocardial ischemia and heart failure.     

Cardioprotection of cariporide evaluated by plasma myoglobin and troponin I in myocardial infarction in pigs

The cardioprotective effects of cariporide were investigated against myoglobin and troponin I elevation in a model of myocardial infarction in pig, and the possible relationship between these markers and myocardial infarct size. The left circumflex coronary artery was ligated for 60-min and then reperfused for 48-h. Plasma levels of myoglobin and troponin I were quantified during reperfusion. Vehicle or cariporide (2.5 mg/kg) were administered i.v. before ischaemia and infused throughout ischaemia and for the beginning of reperfusion. In vehicle-treated pigs, the infarct size represented 26% +/- 3% of the area at risk. Cariporide significantly decreased the infarct size by 66% +/- 9%, and significantly reduced plasma levels of myoglobin and troponin I. A strongly correlated linear relationship between myocardial necrosis and plasma levels of myoglobin (R = 0.966, P < 0.0001) or troponin I (R = 0.855, P < 0.0001) was clearly identified. In conclusion, in our porcine model of myocardial infarction, even with small infarcts (in the presence of cariporide), plasma levels of myoglobin and troponin I are predictive of the presence of necrosis and its extent.     

犬急性缺血心肌非同步运动与左心功能的相关性研究

目的：探讨定量组织速度成像（QTVI）评价犬急性缺血心肌非同步运动与左心功能的相关性。方法：健康犬21只,暴露心脏,于左冠状动脉主干阻断前（对照组）、后（实验组）分别获取左心室12个节段的QTVI曲线,测量各点QRS波起点至心肌收缩期峰值速度和舒张早期峰值速度的时间（Ts和Te）,计算同一壁内3个节段Ts最大差值（Intra-△Ts）和Te最大差值（Intra-△Te）以及左心室12个节段Ts和Te的最大差值（Max-△Ts和Max-△Te）。心室间的不同步指标测量QRS波起点到主动脉瓣血流频谱起点时间（Q-A）,QRS波起点到肺动脉瓣血流频谱起点时间（Q-P）及其差值（Q-AP）。左室射血分数（LVEF）和Tei指数反映左心整体功能。结果：实验组缺血节段Intra-△Ts、Intra-△Te、Max-△Ts、Max-△Te、Q-A、Q-P及Q-AP较对照组明显延长（P＜0.01）,Max-△Ts与Tei指数呈正相关（P＜0.05）,与LVEF呈负相关（P＜0.05）。QRS与Max-△Te呈正相关（P＜0.05）。结论：犬急性缺血左心室内及心室间心肌存在明显非同步运动,且与心功能密切相关。     

背向散射积分、组织多普勒与核素扫描对心肌缺血和存活的相关性临床研究

目的:进一步探讨组织多普勒和组织定征技术临床应用的可行性。方法:12例超声发现节段性室壁运动失常患者分别进行多巴酚丁胺负荷超声心动图、超声组织多普勒、背向散射积分及核素扫描检查。结果:有收缩储备节段背向散射积分曲线形态评分较无收缩储备节段明显降低,背向散射积分周期变异幅度(CVIB)、T波顶点时心内膜运动速度(Vendo)、心肌中部心动周期中最大运动速度(TVC)、收缩期心肌运动速度峰值跨壁梯度(MVGm+)及放射性核素摄取率均较无收缩储备节段显著增高,有收缩储备节段背向散射积分平均值(AII)与无收缩储备节段的差别无显著性。心肌收缩期运动指标与CVIB正相关,与AII负相关。放射性核素摄取率与TVC、Vendo、MVGm+正相关,与AII负相关,与CVIB相关呈临界状态。结论:背向散射积分和组织多普勒指标在判断心肌缺血与存活的临床应用方面有很大潜力。