Infarct involution and improved function during healing of acute myocardial infarction: the role of microvascular obstruction.

Delayed contrast-enhanced cardiac magnetic resonance imaging (ceCMR) delineates infarct size. The presence of hypoenhancement consistent with microvascular obstruction (MO) signifies larger infarcts with a worse prognosis. We hypothesized that the size of the contrast defect (CD) on ceCMR in acutely infarcted myocardium may change during infarct healing and depend upon the presence of MO. Twenty-five patients underwent CMR on weeks 1 and 8 after reperfused myocardial infarction. After short-axis cine CMR was performed, gadolinium was infused and ceCMR images and matched tagged cine MR images were obtained in the three most dysfunctional short-axis slices on cine CMR. The area and transmural extent of hyperenhancement (HE) with or without MO representing total CD size were planimetered. Between week 1 and week 8, the CD area fell from 1729+/-970 mm2 at week 1 to 1270+/-706 mm2 (p<0.001), as did the transmural extent of infarction (71+/-22% to 63+/-24%, p<0.001). The decline in CD trended to be higher in patients with MO (840+/-807 mm2) than in HE (312+/-485 mm2, p<0.07). In the patient group as a whole, ejection fraction (EF) improved (56+/-9% to 60+/-10%, p=0.002) between weeks 1 and 8, but patients with MO showed no increase in EF. Segments with some HE demonstrated partial functional improvement whereas no improvement was seen in HE+MO segments. In patients 8 weeks after reperfused myocardial infarction (MI), the size of infarction by ceCMR decreases compared to week 1 post-MI, especially in those with microvascular obstruction in whom there is little improvement in regional or global function.     

Favorable left ventricular remodeling following large myocardial infarction by exercise training. Effect on ventricular morphology and gene expression.

Continued adverse remodeling of myocardium after infarction may lead to progressive ventricular dilation and heart failure. We tested the hypothesis that exercise training in a healed myocardial infarction-dysfunction rat model can favorably modify the adverse effects of ventricular remodeling including attenuation of abnormal myosin gene expression. Sprague-Dawley rats were subjected to either proximal LAD ligation or sham operation. At 5 wk after the operation, animals were randomly assigned to sedentary conditions or 6 wk of graduated swim training, creating four experimental groups: infarct sedentary (IS), infarct exercise (IE), sham sedentary (SS), and sham exercise (SE). At 11 wk all rats were sacrificed and analyzed. Compared to sedentary infarct controls, exercise training attenuated left ventricular (LV) dilation and allowed more hypertrophy of the non infarct wall. The exercise-trained hearts also showed a reduction in the estimated peak wall tension. Northern blot analysis showed an increase in beta-myosin heavy chain expression in the hearts of the sedentary infarction group soon after infarction when compared to sham controls. However, with exercise training, there was a significant attenuation of the beta-myosin heavy chain expression in the myocardium. Exercise training in a model of left ventricular dysfunction after healed myocardial infarction can improve the adverse remodeling process by attenuating ventricular dilation and reducing wall tension. The abnormal beta-myosin expression was also attenuated in the exercise trained group. This is evidence that abnormal gene expression following severe myocardial infarction dysfunction can be favorably modified by an intervention.     

钙离子拮抗剂对大鼠心肌梗死后心肌细胞凋亡的影响

目的探索钙离子拮抗剂对缺血后心肌细胞凋亡的影响.方法结扎大鼠冠状动脉(冠脉)造成心肌梗死;实验组动物冠脉结扎前和术后3 h分别经口腔内滴注和腹腔注射钙离子拮抗剂Adalat 1 mg/kg和0.4 mg/kg,缺血对照组给安慰剂;正常对照组行假手术不结扎冠脉,给安慰剂.术后6 h测定左室功能,并取心脏标本作原位缺口末端标记法(TUNEL)原位细胞凋亡和Fas、Bcl-2蛋白免疫组织化学(组化)染色,高倍镜下计算细胞凋亡指数.结果实验组和缺血对照组的左室收缩压、左室舒张末压和压力改变速度(dp/dt)无显著差异,3个指标分别为76.7±7.5/8.0±6.1 mm Hg比74.9±11.1/11.6±8.3 mm Hg,P>0.05;(777.3±128.6)mm Hg/s比(761.8±136.4)mm Hg/s,P>0.05;但均低于正常对照组[94.9±7.5/2.8±3.2 mm Hg,P<0.001;(1 131.5±112.8)mm Hg/s,P<0.001];实验组和缺血对照组心肌缺血区TUNEL染色阳性,实验组心肌细胞凋亡指数显著低于缺血对照组(0.201±0.053比0.261±0.045,P<0.05),在缺血周边的心肌区Fas和Bcl-2蛋白免疫组化染色阳性,而正常对照组3种染色均阴性.结论缺血可诱导心肌细胞凋亡及Fas和Bcl-2基因的表达;钙离子拮抗剂具有抑制心肌细胞凋亡的作用.     

Overexpression of insulin-like growth factor-1 in mice protects from myocyte death after infarction, attenuating ventricular dilation, wall stress, and cardiac hypertrophy.

To determine whether IGF-1 opposes the stimulation of myocyte death in the surviving myocardium after infarction, transgenic mice overexpressing human IGF-1B in myocytes (FVB.Igf+/-) and wild-type littermates at 1.5 and 2.5 mo of age were subjected to coronary ligation and killed 7 d later. Myocardial infarction involved an average 50% of the left ventricle, and produced cardiac failure. In the region proximate to infarction, myocyte apoptosis increased 4. 2-fold and 2.1-fold in nontransgenics at 1.5 and 2.5 mo, respectively. Corresponding increases in myocyte necrosis were 1. 8-fold and 1.6-fold. In contrast, apoptotic and necrotic myocyte death did not increase in FVB.Igf+/- mice at either age after infarction. In 2.5-mo-old infarcted nontransgenics, functional impairment was associated with a 29% decrease in wall thickness, 43% increase in chamber diameter, and a 131% expansion in chamber volume. Conversely, the changes in wall thickness, chamber diameter, and cavitary volume were 41, 58, and 48% smaller in infarcted FVB.Igf+/- than in nontransgenics. The differential response to infarction of FVB.Igf+/- mice resulted in an attenuated increase in diastolic wall stress, cardiac weight, and left and right ventricular weight-to-body wt ratios. In conclusion, constitutive overexpression of IGF-1 prevented activation of cell death in the viable myocardium after infarction, limiting ventricular dilation, myocardial loading, and cardiac hypertrophy.     

Distinctive changes in end-diastolic wall thickness and postsystolic thickening in viable and infarcted myocardium.

OBJECTIVES: In this study, we sought to compare the magnitude of changes in end-diastolic wall thickness (WT(ed)) and postsystolic thickening (PST) in a swine model of stunning and reperfused acute myocardial infarction, and to explore the relationship between WT(ed) and PST. METHODS: Twenty-six pigs were subjected to left anterior descending coronary artery occlusion followed by reperfusion to induce stunning (n = 6), nontransmural (n = 8), or transmural (n = 12) myocardial infarction. Myocardial wall thickness was measured using intracardiac echocardiography. Transmural extent of necrosis (TEN) was quantified by triphenyltetrazolium chloride technique. RESULTS: During the first minutes of reperfusion, a marked increase in WT(ed) occurred in the myocardial walls with nontransmural and transmural infarct (42% and 102%, respectively) but less in those with stunning (19%). PST persisted at reperfusion in walls with stunning and nontransmural infarct (23% and 26%, respectively). In transmurally infarcted walls, PST progressively decreased either during occlusion (5/12 pigs) or shortly after reperfusion (7/12 pigs). PST at reperfusion was virtually absent when TEN was >70%. Both PST and the increase in WT(ed) at reperfusion correlated well with TEN (P <.0001 for both). Changes in PST at reperfusion were weakly correlated with changes in WT(ed). CONCLUSIONS: A marked increase in WT(ed) after reperfusion and absence of PST indicate transmural myocardial infarction. Presence of PST at reperfusion indicates viable tissue in more than 30% of wall thickness. The results suggest that amplitude of PST is modulated predominantely by factors related to the severity of ischemia and, to a smaller extent, by changes in wall thickness.     

Global longitudinal strain measured by two-dimensional speckle tracking echocardiography is closely related to myocardial infarct size in chronic ischaemic heart disease

2D-STE (two-dimensional speckle tracking echocardiography) is a novel echocardiographic modality that enables angle-independent assessment of myocardial deformation indices. In the present study, we tested whether peak systolic epsilon(parallel) (longitudinal strain) values measured by 2D-STE could identify areas of MI (myocardial infarction) as determined by CE MRI (contrast-enhanced magnetic resonance imaging). Conventional echocardiographic apical long-axis recordings were performed in 38 patients, 9 months after a first MI. Peak systolic epsilon(parallel) measured by 2D-STE in 16 left ventricle segments was compared with segmental infarct mass and transmurality assessed by CE MRI. Segmental values were averaged to global and territorial values for assessment of global function and myocardial function in the coronary distribution areas. CE MRI identified transmural infarction in 27 patients, and a mean infarct size of 36+/-25 g. Peak systolic epsilon( parallel) correlated with the infarct mass at the global level (r=0.84, P<0.001). A strain value of -15% identified infarction with 83% sensitivity and 93% specificity at the global level and 76% and 95% at the territorial level, and a strain value of -13% identified transmural infarction with 80% sensitivity and 83% specificity at the segmental level. Global infarct mass correlates with the wall motion score index (r=0.70, P<0.001), and left ventricular ejection fraction measured by MRI or echocardiography (r=-0.71 and -0.58, both P<0.001). In chronic infarction, peak systolic epsilon(parallel) measured by 2D-STE correlates with the infarct mass assessed by CE MRI at a global level, and separates infarcted from non-infarcted tissue. Global strain is an excellent predictor of myocardial infarct size in chronic ischaemic heart disease.     

hVEGF165腺相关病毒对心肌梗死大鼠心功能的影响

目的探讨直接心肌注射基因重组hVEGF165腺相关病毒（rAAV—hVEGF165）对急性心肌梗死大鼠心功能的影响。方法取81只雄性Sprague—Dawley大鼠,制备急性,0．／肌梗死大鼠模型。将心肌梗死大鼠模型随机分成4组：假手术组15只;心肌梗死组25只;生理盐水纽25只;VEGF组16只。生理盐水组和VEGF组分别接受生理盐水或rAAV—hVEGF165100μ1分3点注射于梗死交界处心肌内。于注射4周后测定心肌组织VEGF含量、超声心动图参数、梗死范围、微血管数量、心钠素（atrial natriuretic peptide,ANP）水平。结果假手术组中3只大鼠、心肌梗死组中13只大鼠、生理盐水组中15只大鼠、VEGF组中7只大鼠死亡,43只大鼠进入研究。VEGF组心肌梗死范围较心肌梗死组和生理盐水组明显减小（38．6±3．0）％VS（42．5±3．8）％、（42．5±2．6）％（P〈0．05）。VEGF组的左心室射血分数显著高于心肌梗死组和生理盐水组（61．11±8．37）％VS（44．17±5．31）％、（39．40±5．48）（P〈0．01）。VEGF纽心肌组织中VEGF含量较心肌梗死组和生理盐水组有所增加。血管计数显示,VEGF组有更多的新生血管形成（522．38±82．14）mm2vs（419．99±32．17）mm2、（420．86±16．50）mm2（P〈0．01）。结论梗死区交界处心肌内直接注射rAAV-hVEGF165能够显著改善急性心肌梗死大鼠的心功能,缩小梗死范围,促进心肌内新生血管的形成。     

急性心肌梗死早期患者血清中可溶型ST2水平及其与心肌活性的关系

目的探讨急性心肌梗死患者早期血清可溶性ST2(sST2)水平及其与心肌活性的关系。方法采用ELISA法检测30例发病12 h以内的非ST段抬高型心肌梗死(NSTEMI)患者血清sST2水平,于发病后第7天行心脏磁共振检查并根据磁共振结果将患者分为透壁增强组、非透壁增强组和混合组。于7¹4 d行PCI术,并于术后6个月再次行心脏磁共振检查评估心肌活性,观察指标包括梗死心肌质量、左心室射血分数及室壁运动异常评分在术前及术后的变化及其与心肌梗死早期血清sST2水平的关系。结果透壁增强组血清sST2的水平较之非透壁增强组及混合组明显升高(P<0.05),混合组较非透壁增强组高(P<0.05);梗死心肌质量及室壁运动异常评分在3组患者PCI术后均减少,梗死心肌质量在非透壁增强组及混合组中减少有统计学差异(P<0.05),室壁运动异常评分在非透壁增强组降低显著(P<0.05);左心室射血分数在3组患者PCI术后均增加,在非透壁增强组及混合组中增加有统计学差异(P<0.05)。心肌梗死早期血清sST2水平与PCI术前及PCI术后6个月的心肌活性相关。结论急性心肌梗死早期血清中sST2的水平可反映心肌受损情况并可预测心肌梗死7 d PCI术前及PCI术后6个月的心肌活性。     

Higher levels of collagen and facilitated healing protect against ventricular rupture following myocardial infarction

The mechanism of cardiac rupture after MI (myocardial infarction) is not fully understood. Rupture has not been reported in most laboratory species, including the rat, but does occur in mice. We have reported previously that beta2-TG mice (transgenic mice with cardiac-restricted overexpression of beta2-adrenergic receptors) had a lower incidence of rupture compared with NTG (non-transgenic) littermates. We hypothesized that the difference in the incidence of rupture between rodents and specific mouse strains is due to the difference in collagen content following MI. In the present study, we compared the difference in matrix remodelling post-MI between beta2-TG and NTG mice and between mice and rats. MI was induced by ligation of the left main coronary artery. Following MI, tensile strength, insoluble and soluble collagen content and gelatinase expression were determined in the infarcted and non-infarcted myocardium. Better preserved tensile strength measured as TTR [tension-to-rupture; 88+/-14 and 58+/-3% of the respective sham group values for beta2-TG compared with NTG mice (P<0.05); 108+/-7 and 32+/-4% of the respective sham group values for rats compared with 129sv mice (P<0.01)] and less severe acute infarct expansion after MI were found in rats compared with mice or in beta2-TG compared with NTG mice. These differences were associated with a higher content of pre-existing fibril collagen in the normal myocardium of beta2-TG compared with NTG mice (1.6-fold) or rats compared with 129sv mice (2-fold) and an accelerated fibrotic healing in the infarcted myocardium. Additionally, a less pronounced increase in MMP-9 (matrix metalloproteinase-9) activity was observed in the infarcted myocardium of rats compared with 129sv mice. We conclude that a higher collagen level is associated with facilitated fibrotic healing of an infarct and preserves the tensile strength of infarcted myocardium, thereby preventing cardiac rupture and acute ventricular remodelling.     

骨骼肌卫星细胞移植对心肌梗死大鼠心肌纤维化的影响

背景:现已发现心肌梗死后心肌纤维化是心室重构的重要机制,而相关干细胞心肌移植对这一过程的影响报道不多.目的:观察自体骨骼肌卫星细胞移植对心肌梗死大鼠心肌纤维化的影响,并探讨其可能机制.设计、时间及地点:随机对照动物实验,于2007-07/09在解放军第三军医大学大坪医院野战外科研究所第三研究室完成.材料:Wistar 大鼠45只,雌雄各半,体质量150～200 g,其中30只用于制备心肌梗死模型.方法:45只大鼠按随机抽签法分为3组,每组15只.心肌梗死组:结扎冠状动脉左前降支造成心肌梗死,2周后沿梗死区与正常心肌交界处多点注射0.2 mL无血清M199培养液;移植组:造模后将体外培养2周的大鼠自体卫星细胞0.2 mL以注射的方式移植到大鼠梗死区周围.假手术组:不造模,仅在左前降支周围心前壁多点注射0.2 mL生理盐水.主要观察指标:4周后测定各组大鼠缺血心肌血管内皮生长因子mRNA、血管内皮生长因子蛋白质的表达,缺血心肌毛细血管密度变化,苏木精伊红染色观察各组心肌细胞在梗死区的生长、增殖情况.结果:①卫星细胞移植4周后,假手术组和心肌梗死组血管内皮生长因子mRNA和血管内皮生长因子蛋白表达较移植组明显降低(P<0.01);心肌梗死组大鼠毛细血管密度较假手术组升高(P<0.05);移植组大鼠缺血心肌中毛细血管密度较假手术组、心肌梗死组亦明显升高(P<0.01).②苏木精-伊红染色显示假手术组大鼠心肌形态正常,结构清晰,心肌纤维排列整齐有序,肌纤维间无成纤维细胞聚集、增生现象.心肌梗死组大鼠心肌内可见成纤维细胞增生及胶原形成,心肌有序的基本结构发生紊乱.移植组大鼠其梗死区可见较多带有横纹且具有多核的肌细胞存在,组织排列较有序,纤维组织明显少于心肌梗死组.结论:卫星细胞在心肌梗死区中可增殖分化为具有弹性和收缩功能的横纹肌样细胞,并通过自分泌和旁分泌的形式分泌血管内皮生长因子促使缺血心肌毛细血管增生,从而有效地抑制了缺血心肌的纤维化进程.     

人脐血单个核细胞多次静脉移植家兔急性心肌梗死后的胶原重构

背景：以往干细胞移植治疗心肌梗死的研究,均为单次经静脉或冠脉注射移植。目的：进一步验证人脐血单个核细胞多次静脉移植对家兔急性心肌梗死胶原重构及心功能影响。方法：取家兔45只结扎冠脉左前降支制备急性心肌梗死模型,随机分为3组,①多次移植组：造模后7,9,11,13d经耳缘静脉注入BrdU标记人脐血单个核细胞生理盐水。②单次移植组：造模后7d注入BrdU标记人脐血单个核细胞生理盐水,9,11,13d注入生理盐水。③心梗对照组：仅注入生理盐水。另取家兔5只为假手术组。结果与结论：与对照组相比,两移植组心功能左室短轴缩短率、左室射血分数明显升高（P〈0.05）;且多次移植组改善效果优于单次移植组（P〈0.05）;免疫组织化学显示两移植组造模后2,4周心梗周边区均存在BrdU阳性细胞,但多次移植组BrdU阳性细胞计数多于单次移植组;改良Masson’s染色显示与假手术组比较,对照组梗死区及非梗死区胶原密度显著增加,梗死区域胶原纤维部分融合,排列较紊乱,心肌基本组织结构破坏;与对照组比较,两移植组造模后2,4周梗死周边区域心肌细胞间胶原含量、胶原纤维明显减少,胶原纤维排列较为有序;与单次细胞移植组比较,多次细胞移植组进一步改善。提示多次静脉移植脐血单个核细胞改善急性心肌梗死心功能、阻抑心肌胶原纤维重构疗效优于单次静脉移植。     

骨髓间充质干细胞移植对兔急性心肌梗死后胶原重构的影响

背景:研究发现干细胞移植可明显改善心肌梗死后心功能,以往认为主要与干细胞分化为心肌细胞和促血管新生作用有关,近来研究显示旁分泌、抑制心室重构尤其是细胞外胶原重构对心功能的改善起重要作用.目的:探讨骨髓间充质干细胞移植对兔急性心肌梗死后胶原重构的影响.设计、时间及地点:随机对照动物实验,于2007-06/08在辽宁中医药大学针灸电生理实验室完成.材料:健康日本大耳白兔57只,购自辽宁中医药大学实验动物中心.方法:取2只兔用于制备骨髓间充质干细胞,移植前行BrdU标记.余55只兔取10只作为正常组,45只结扎冠状动脉左室支建立心肌梗死模型,共30只成功造模,随机分为模型组、盐水组、细胞移植组,10只,组.兔心肌梗死后7 d,细胞移植组经耳缘静脉注射骨髓间充质干细胞悬液1 mL(2×10<'6>个细胞),盐水组注射1 mL生理盐水,造模后饲养5周.主要观察指标:采用Masson三色染色法观察心肌间质纤维结构及测量胶原容积分数,免疫组化法测量Ⅰ/Ⅲ型胶原比值.结果:细胞移植组心肌梗死区可见Brdu染色阳性细胞.细胞移植组梗死中心区和交界区内胶原纤维融合较少,排列有序;模型组和盐水组梗死中心区和交界区内胶原纤维斑块状融合明显,排列紊乱.心肌梗死5周后与正常组比较,模型组梗死区及梗死周围区胶原容积分数显著增加(P<0.05),Ⅰ/Ⅲ型胶原比值显著下降(P<0.05);与模型组比较,细胞移植组胶原容积分数、Ⅰ/Ⅲ型胶原比值均显著下降(P<0.05).结论:静脉移植骨髓间充质干细胞可以在心肌梗死区定植,通过减少胶原形成、改善胶原结构来抑制心肌梗死后胶原重构.     

胆囊壁厚度在胆囊炎性疾病诊断中的价值

我们对１２６例因急性或亚急性胆囊病发作而行胆囊切除术的胆囊标本与术前胆囊的超声表现进行了对照研究。我们把厚度＞３ｍｍ作为胆囊壁增厚的标准，将胆囊壁缺血坏死和粘膜出血作为病情严重的指征。结果显示：１．胆囊壁的薄厚在急性及慢性胆囊炎的分布上都无显著性差异；２．胆囊壁局灶性缺血出血和坏死中薄壁和厚壁所占比例无显著性差异；３．胆囊薄壁厚壁中局灶性缺血出血和坏死的发生率未显示出差异。因此不能仅凭胆囊壁增厚就作出胆囊炎的诊断，也不能得出胆囊壁＜３ｍｍ就不是胆囊炎的结论，同时也不能单纯依据超声测量胆囊壁的厚度来估计病情严重程度，不能因为胆囊壁薄就认为病情不重而作为推迟手术的唯一标准。     

Effect of AR-R 17477, a potent neuronal nitric oxide synthase inhibitor, on infarction volume resulting from permanent focal ischemia in rats

OBJECTIVE: We tested whether AR-R 17477, a selective inhibitor of neuronal nitric oxide synthase, reduces brain injury in rats subjected to permanent focal ischemia. DESIGN: Randomized within cohort; nonblinded study. SETTING: University basic science laboratory. SUBJECTS: Halothane-anesthetized male Wistar rats (n = 53). INTERVENTIONS: Rats were treated with either intravenous saline (diluent) or AR-R 17477 (1 or 3 mg/kg) 30 mins before or 60 mins after the onset of permanent focal cerebral ischemia. Infarction volume was determined at 18 or 48 hrs of ischemia. MEASUREMENTS AND MAIN RESULTS: Pretreatment with 1 mg/kg AR-R 17477 was associated with a decreased infarct volume (2,3,5-triphenyltetrazolium chloride staining) in the striatum (saline, 81+/-7 mm3; AR-R 17477, 55+/-3 mm3) but not in the cortex at 18 hrs of occlusion (saline, 302+/-29 mm3; AR-R 17477, 237+/-36 mm3). However, this therapeutic effect of AR-R 17477 was no longer evident if the rats were allowed to survive for 48 hrs before analysis of infarction volume. In fact, in this separate cohort of animals, three of eight AR-R 17477-treated and five of eight saline-treated rats died before completing 48 hrs of ischemia. Efficacy of AR-R 17477 was completely absent (even at 18 hrs of ischemia) when drug treatment was delayed until 1 hr after the onset of ischemia. Infarction volume at 18 hrs of ischemia was similar between rats treated with saline, 1 mg/kg (cortex, 229+/-43 mm3; striatum, 67+/-8 mm3) or 3 mg/kg AR-R 17477 (cortex, 284+/-34 mm3; striatum, 75+/-5 mm3). In addition, only one of eight rats treated with 3 mg/kg AR-R 17477 at 1 hr of ischemia survived 48 hrs of occlusion, compared with three of eight rats treated with saline. CONCLUSIONS: Neuronally generated nitric oxide is a mediator of brain injury during permanent focal ischemia in rats. However, severity of the ischemic insult appears to limit the therapeutic efficacy of the specific neuronal nitric oxide synthase inhibitor, AR-R 17477.     

Clinical benefit of prostaglandin E1-treatment of patients with ischemic heart disease: stimulation of therapeutic angiogenesis in vital and infarcted myocardium.

New evidence suggests that Prostaglandin E1 (PGE-1) stimulates myocardial angiogenesis in human chronic ischemic myocardium. We sought to investigate whether PGE-1 may participate in the process of neoangiogenesis within the myocardial infarct scar. Neovascularization was investigated in 14 explanted hearts from patients with ischemic cardiomyopathy, who had been bridged to heart transplantation (HTX) with PGE-1 and compared with 14 hearts from patients who did not receive PGE-1 prior to HTX. In transmural sections obtained from the left ventricular wall and containing myocardial scar tissue, CD34 and vascular endothelial growth factor (VEGF) were quantified immunohistochemically to estimate capillary density and amount of angiogenesis. Additionally, to assess the hypoxic state of myocardium of the infarct border zone, hypoxia inducible factor 1-alpha (HIF-1alpha) was determined by immunohistochemistry and quantified by means of planimetric analysis. PGE-1-treated patients had significantly more CD34-and VEGF-positive cells in infarct areas as compared to nonPGE-1 group, respectively (CD34: 116.7 +/- 5.9 vs. 45.1 +/- 5.2 capillary profiles/mm(2), P < 0.001, and VEGF: 48.3 +/- 4.9 vs. 22.9 +/- 4.7 capillary profiles/mm(2)). HIF-1alpha enrichment (in %) as well as staining intensity (in estimated units (eU)) was significantly decreased in PGE-1-treated as compared to non-treated controls (enrichment: 11.3 +/- 2.5% vs. 19.4 +/- 4.36%; staining intensity: 0.95 +/- 0.3 vs. 1.97 +/- 0.44 eU). Our data demonstrate that PGE-1 stimulates neoangiogenesis in infarct areas adjacent to viable myocardium, via upregulation of VEGF expression. The induction of therapeutic angiogenesis along with the improved hypoxic state of chronic ischemic myocardial tissue might explain the favorable clinical outcome in PGE-1 treated patients.     

Propranolol decreases sympathetic nervous activity reflected by plasma catecholamines during evolution of myocardial infarction in man.

Plasma 1-norepinephrine and epinephrine contents were strikingly elevated in 70 patients during evolution of myocardial infarction. Propranolol or placebo, 0.1 mg/kg i.v., was administered randomly an average of 10 h after infarction and continued orally for 3 d. Propranolol, but not placebo, acutely decreased 1-norepinephrine contents from 2.24 +/- 1.33 (mean +/- SD) to 1.31 +/- 0.74 microgram/liter, P less than 0.001, and epinephrine contents from 0.97 +/- 0.42 to 0.74 +/- 0.42 microgram/liter, P less than 0.02. Decreases in 1-norepinephrine contents were related to the initial plasma concentrations, r = 0.85, P less than 0.001. A similar, but less strong relationship was observed between the initial epinephrine contents and propranolol-induced changes, r = -0.51, P less than 0.01. Propranolol reduced plasma-free fatty acid contents from 1,121 +/- 315 to 943 +/- 274 mumol/liter, P less than 0.001. Decreases in plasma contents of free fatty acids were related to decreases in epinephrine, r = 0.66, P less than 0.001. Propranolol did not cause significant additional changes in plasma catecholamine contents during the subsequent 3 d. In the placebo group 1-norepinephrine contents had decreased 24 h after infarction from 1.92 +/- 0.99 to 1.37 +/- 0.93 microgram/liter, P less than 0.02. Plasma epinephrine contents did not change. Heart rate remained below the control values during the entire study period in the propranolol, but increased in the placebo group. The data indicate that sympathetic hyperactivity, indirectly reflected by plasma catecholamine contents, is acutely reduced by propranolol during evolution of myocardial infarction.     

Ultrasonic myocardial integrated backscatter and myocardial wall thickness in animal experiments

The purpose of this study was to distinguish between normal and ischemic myocardium using ultrasonic integrated backscatter (IB) measurements and to relate IB with myocardial wall thickness. IB was measured in 9 open-chested Yorkshire pigs (24-30 kg) before, after 30 minutes of partial occlusion of the proximal left anterior descending coronary artery (LADCA), and after 60 minutes of subsequent reperfusion. The ultrasound transducer (4 MHz) was sutured onto the epicardial surface perfused by the LADCA. IB measurements were made with a repetition rate of 50 times per heart rate simultaneously with a left ventricular pressure signal. Myocardial wall thickness was measured off-line. The measurements of integrated backscatter, left ventricular pressure and wall thickness were based on mean values of ten subsequent cardiac cycles. End-systolic IB measurements were 5.3 dB higher during occlusion as compared to the reference measurements (7.1 +/- 3.2 dB versus 1.8 +/- 2.6 dB; p = 0.002). No statistically significant differences were found in end-systolic IB measurements. End-systolic wall thickness was 5 mm smaller during occlusion as compared to the reference measurements (7.2 +/- 1.4 mm versus 12.2 +/- 1.2 mm; p less than 0.001). Simple linear regression analysis showed a statistically significant inverse relationship between IB measurements and wall thickness in 21 out of the 23 sequences in which wall thickness could be measured. End-systolic IB measurements are favourable to distinguish acute ischemic myocardium from normal myocardium. There is a distinct inverse relationship between IB and myocardial wall thickness.     

Improved cardiac tagging resolution at ultra-high magnetic field elucidates transmural differences in principal strain in the mouse heart and reduced stretch in dilated cardiomyopathy.

Cardiac tagging resolution for regional principal strains E1 and E2 has been a limiting factor for the study of dilated mouse hearts, in which the left ventricle (LV) wall thickness can drop to below 1 mm. Therefore, high resolution tagging was performed at 14.1 T to enable transmural principal strain measurements across the LV wall of normal mouse hearts and average principal strains in thinned LV walls of a transgenic mouse (PKCepsilon TG) that develops dilated LV. A modified DANTE tagging and fast gradient imaging method produced a tagging grid dimension of 0.33 x 0.33 mm and line thickness under 0.1 mm. In normal mice, average E1 strain in the epicardium was significantly higher than the endocardial E1 (epi = 0.22 +/- 0.10; endo = 0.13 +/- 0.07, p < 0.05), while magnitude of average endocardial E2 was greater than in the epicardium (endo = -0.12 +/- 0.03, epi = -0.08 +/- 0.03; p < 0.001). E1 strain averaged over four segments was reduced in dilated hearts compared to controls (PKCepsilon TG = 0.14 +/- 0.02; control = 0.18 +/- 0.02, p < 0.01), with specific reductions in septal (33%) and lateral (31%, p < 0.01) segments. E2 strain was similar between dilated and control hearts at -0.11 +/- 0.01. Thus, improved tagging resolution demonstrates that stretch (E1), but not compression strains (E2), are reduced as a result of significant LV wall thinning in a mouse model of dilated cardiomyopathy.     

Reduction of infarct size in the rat heart by LPS preconditioning is associated with expression of angiogenic growth factors and increased capillary density.

Inflammation induces the expression of angiogenic growth factors in tissues, which leads to microvascular growth. Bacterial lipopolysaccharide (LPS) provokes a transient inflammatory response in the heart and induces delayed cardiac resistance to post-ischemic contractile dysfunction. In this study, we examined: 1) the effects of LPS on myocardial expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), 2) whether an increase in the density of myocardial microvessels follows the expression of angiogenic growth factors, and 3) the effect of LPS on myocardial resistance to infarction and its relationship with microvascular growth. Rats were treated with LPS (from Salmonella typhimurium, 0.5 mg/kg i.p.). The expression of bFGF and VEGF in the myocardium was examined at 6 and 12 h after LPS treatment by immunofluorescent staining. Myocardial capillary and arteriole densities were determined 3 days after LPS treatment by morphometry, using immunofluorescent staining of von Willebrand factor (a marker protein of endothelial cells) and alpha-smooth muscle actin (a marker protein of smooth muscle cells). To examine cardiac resistance to infarction, hearts were subjected to 40 min of regional ischemia and 2 h of reperfusion by reversible occlusion of left coronary artery at 3 days after LPS treatment. LPS induced cardiac bFGF and VEGF at 6 and 12 h after treatment. The expression of these growth factors was followed by an increase in myocardial capillary density (2032 +/- 78/mm2 vs. 1617 +/- 47/mm2 in saline control, P < 0.05), but not arteriole density, at 3 days. Meanwhile, infarct size was significantly reduced by LPS preconditioning (infarct/left ventricle 12.3 +/- 1.04% vs. 21.7 +/- 1.65% in saline control, 43% reduction, P < 0.05). These results suggest that LPS preconditioning induces cardiac bFGF and VEGF, and an increase in myocardial capillary density. This increased myocardial capillary density is associated with a reduced infarct size after in vivo regional ischemia-reperfusion.     

Topographic correspondence of contrast echocardiographic perfusion mapping and myocardial infarct extent after varying durations of coronary occlusion

After acute coronary occlusion, the extent of dysfunction exceeds the extent of infarction by a variable amount. Contrast echocardiography has been shown to be a good predictor of the extent of acute infarction after permanent occlusion. We used hydrogen peroxide contrast echocardiography to study the temporal and topographic relationship between contrast enhancement and tissue viability during acute myocardial infarction in 32 dogs undergoing 1, 2, 3, or 4 hours of circumflex occlusion before reperfusion. To account for changes in collateral blood flow, contrast studies were performed by aortic root injection immediately before reperfusion. The area, circumference, and transmural extent of the region at risk in vivo by contrast echocardiography were statistically unchanged regardless of the duration of occlusion before reperfusion. Echo contrast defect analysis of the risk region predicted the area, circumference, and transmural extent of infarcts reperfused at 2 or more hours (r = 0.81, 0.84, 0.71, respectively). For the 1-hour occlusion group, contrast defect analysis predicted the circumference at risk but markedly overestimated the area and transmural extent of infarction. These data indicate that the circumferential extent of infarction can be identified by contrast echo and is fixed by 1 hour of occlusion. Infarction progression transmurally within the circumferential boundaries had nearly reached the transmural contrast extent by 2 hours of occlusion in this model. Assuming the development of a similar high contrast agent safe for human injection, aortic root contrast echocardiography could be useful to predict myocardium at risk of infarction early after occlusion. Late after occlusion it could be of value to predict the presence of still viable myocardial layers within the dysfunctional infarct region.