Metabolic action and cellular structure of the myocardium during coronary angiography

Experimental perfusion of coronary arteries of guinea pig heart with contrast media causes various changes in electrolyte metabolism, depending on the chemical structures of the administered contrast media. These electrolyte changes are related to the tolerance of the myocardium to the contrast agents. Electron microscopic sections of human myocardium after coronary perfusion with Urografin-76 reveal that no alterations of subcellular structure occur.     

Hypervolaemia improves global and local function and efficiency in postischaemic myocardium

1. In the present study, we investigated the effects of blood volume on postischaemic function and efficiency. In 14 anaesthetized dogs, following recovery from a period of 15 min occlusion of the left anterior descending coronary artery, the effects of hypervolaemia (HYPER; 15% increased volume produced by fast infusion of Hespan; B Braun Medical, Irvine, CA, USA), normovolaemia (NORMO) and hypovolaemia (HYPO) were studied. 2. Although myocardial O2 consumption was not significantly increased by volume (6.37+/-0.94 vs 6.89+/-1.1 mL/min per 100 g for HYPO and HYPER, respectively), local work of the stunned myocardium was markedly elevated (8.8+/-1.7 vs 22.5+/-3.5 g.mm/ beat, for HYPO and HYPER, respectively; P < 0.05). External work of the heart was also significantly improved (71.8+/-12.7 vs 139.5+/-16.2 mmHg.L/min for HYPO and HYPER, respectively). These data indicate markedly improved efficiency produced by volume, because work was increased with no change in myocardial O2 consumption. 3. Local dysfunction was characterized by several parameters, including systolic bulge, end-diastolic length, delay to onset of shortening, end shortening time delay (EST) and tail work ratio. Hypervolaemia reduced EST compared with hypovolaemia (98.6+/-18.3 vs 110.7+/-14.9 msec, respectively; P < 0.05) and improved tail work ratio (28.0+/-7.0 vs 36.0+/-7.0%, respectively; P < 0.05), with no effects on systolic bulge, end-diastolic length and delay to onset of shortening. 4. Thus, even in the postischaemic myocardium, increasing work by volume is energetically efficient and is accompanied by partial improvement of local dysfunction.     

Determination of transmural, endocardial, and epicardial radial strain and strain rate from phase contrast MR velocity data

PURPOSE: To develop a method for computing radial strain (epsilon) and strain rate (SR) from phase contrast magnetic resonance (PCMR) myocardial tissue velocity data. MATERIALS AND METHODS: PCMR tissue velocity maps were acquired at basal and mid-short-axis slices in the myocardium in 10 healthy volunteers. An algorithm for computing radial strain and SR from PCMR tissue velocity data was developed. PCMR strain values were compared to values computed independently from contours drawn on cine steady-state free procession (SSFP) images. Peak endocardial and epicardial strain and SR values from PCMR data were compared. RESULTS: Excellent agreement was observed between peak strain values computed by PCMR and cine SSFP contours (38.1 +/- 5.4% vs. 38.1 +/- 6.2%; P = not significant [NS]). The presence of an endocardial-epicardial gradient was demonstrated in both strain and SR: peak endocardial values were larger than peak epicardial values in the basal and mid-short-axis slices (P < 0.05). CONCLUSION: This study presents a method for determining radial strain and SR values from PCMR velocity data. This technique illustrates a difference in strain and SR across the myocardium with peak endocardial values being greater than peak epicardial values.     

Improved estimation and visualization of two-dimensional myocardial strain rate using MR velocity mapping

PURPOSE: To estimate regional myocardial strain rate, with reduced sensitivity to noise and velocities outside the region of interest, and provide a visualization of the spatial variation of the obtained tensor field within the myocardium. MATERIALS AND METHODS: Myocardial velocities were measured using two-dimensional phase contrast velocity mapping. Velocity gradients were estimated using normalized convolution and the calculated 2D strain rate tensor field was visualized using a glyph representation. Validation utilized a numerical phantom with known strain rate distribution. Strain rate glyph visualizations were created for normal myocardium in both systole and diastole and compared to a patient with an anteroseptal infarction. RESULTS: In the phantom study the strain rate calculated with normalized convolution showed a very good agreement with the analytic solution, while traditional methods for gradient estimation were shown to be sensitive to both noise and surrounding velocity data. Normal myocardium showed a homogenous strain rate distribution, while a heterogeneous strain rate can be clearly seen in the patient data. CONCLUSION: The proposed approach for quantification and visualization of the regional myocardial strain rate can provide an objective measure of regional myocardial contraction and relaxation that may be valuable for the assessment of myocardial heart disease.     

Peculiarities of Myocardial Structure in Rats with Hereditary Hypertension Reared by Normotensive Females

Morphometric analysis revealed no signs of myocardial hypertrophy at the tissue and ultrastructural levels in 3-week-old NISAG rat pups reared by normotensive Wistar females. The severity of myocardial hypertrophy in these animals aging 6 months was similar to that in NISAG rats reared by natural mothers. However, raising conditions during the early ontogeny form compensatory structural changes in the myocardium of rats with genetically determined hypertension.     

SIRS大鼠心肌葡萄糖6磷酸酶活性的测定和线粒体形态变化

目的：对大鼠全身炎症反应综合征（SIRS）阶段心肌细胞浆内参与葡萄代谢的酶活性进行研究,并观察心肌细胞线粒体形态结构,从酶学及亚细胞结构的角度深入了解SIRS时心肌能量代谢的改变。方法：（1）腹注射内毒素（LPS）20mg/kg,以直肠温度、心率、呼吸、血白细胞（WBC）、中性粒细胞数量及血肿瘤坏死因子－α（TNF－α,免疫组化法）含量变化作为SIRS的指标,制造大鼠SIRS的动物模型。（2）酶组织化学方法检测SIRS大鼠心肌细胞葡萄糖6－磷酸酶,图像分析进行半定时测定其活性的变化。（3）SIRS大鼠球后静脉丛取血测血糖。（4）SIRS大鼠心肌细胞的透射电镜观察。结果：（1）注射LPS后1小时大鼠心肌细胞葡萄糖6－磷酸酶活性较对照组明显增强,3小时后则明显减弱,差异性均显著（P均＜0．05）。（2）注射LPS1小时后血糖明显升高,3小时后降低。（3）透射电镜观察可见SIRS大鼠心肌细胞线粒增多,排列紊乱,出现空泡变性,肌纤维水肿。结论：SIRS时存在葡萄糖代谢紊乱及能量代谢障碍,可能为SIRS时MODS的发生的重要原因。     

胎心不同部位心肌酶的分布

目的：探讨人胎心各腔壁的某些酶的含量及其在胚胎发育过程中的变化规律。方法：用组织化学方法和组织扫描光度测定法,观察了胎儿和成人心脏的5种酶。结果：乳酸脱氧酶（LDH）、琥珀酸脱氢酶（SDH）、6-磷酸葡萄糖脱氢酶（G-6-PDH）、细胞色素氧化酶（CCO）在心室壁的含量均明显大于心房壁,且右心大于左心;三磷酸腺苷酸酶（ATPase）在心房的含量略大于右心室,心房和右心室明显大于左心事。结论：人体胎心各腔壁内某些酶的含量存在差别,这种差别可能与相应的结构和功能相关。     

微低温超极化停跳对犬心肌细胞线粒体的保护作用

[目的]从心肌细胞线粒体改变的角度,比较超极化停跳和去极化停跳(钾停跳)的心肌保护效果.[方法]18只纯种比格犬,体质量8.5～15 kg,随机分为实验组和对照组,实验组10例,对照组8例.全麻后建立体外循环模型.阻断主动脉后从主动脉根部灌注停跳液20 mL/kg,全心缺血45 min后,恢复灌注60 min.实验组的停跳液为温血(34℃)尼可地尔(含尼可地尔400 μmol/L),对照组的停跳液为传统的4℃高钾停跳液(含钾22 mmol/L),停跳后两组心脏均局部冰敷以保持低温.心脏停跳期间若出现心电活动,则追加停跳液首量的三分之一.在主动脉阻断前、主动脉阻断40 min、主动脉开放30 min,用活检针穿刺取右室全层心肌行电子显微镜检查,每个标本随机选取6个视野照片,用图象分析系统分析计算线粒体的面积和周长,并计算得出线粒体体积密度、比表面和单位面积线粒体计数.检验水准α=0.05.[结果]两组中各有1例因主动脉阻断不全而被剔除,其它各例在实验中均无须追加停跳液.每组3个时间点之间、两组间线粒体的体积密度(volumedensity,V/V)、比表面(R8v)和单位面积线粒体计数的变化均无统计学意义(P＞0.05).[结论]在我们的实验方案下,超极化停跳和高钾停跳都能有效地保护心肌细胞线粒体,且两种方法具有相似的保护效果.     

线粒体与心肌缺血-再灌注损伤

目的　探讨线粒体的改变与心肌缺血-再灌注损伤(IR)的关系。方法　查阅近年来国内外资料并进行分析、整理、总结。结果　心肌缺血-再灌注时能量耗竭、自由基形成、钙超载、细胞凋亡等过程中线粒体发挥重要的作用。结论　改善线粒体功能在防治心肌缺血-再灌注损伤中具有重要的意义。     

成人心室肌致密化不全的临床特征

目的探讨成人心室肌致密化不全的临床特征。方法7例心室肌致密化不全患者,均采用东芝彩色多普勒超声心动图仪进行检查,探头频率2~4MHz。结果7例出现不同程度心功能不全和心律失常,未见栓塞。超声心动图均可见多发突入心室腔内的肌小梁和与心室腔交通深陷的小梁间隙。结论心室肌致密化不全是一种少见的先天性心肌病,临床可表现为心功能不全、心律失常,超声心动图是可靠的诊断方法。