七氟醚预处理对非糖尿病及糖尿病大鼠心肌保护效应的观察

目的观察七氟醚预处理对非糖尿病及糖尿病大鼠心肌缺血/再灌注损伤的保护效应。方法糖尿病及非糖尿病大鼠各16只,随机分为4组（n=8）：非糖尿病缺血/再灌注组（N组）,非糖尿病七氟醚预处理组（N＋S组）,糖尿病缺血/再灌注组（D组）,糖尿病七氟醚预处理组（D＋S组）。建立离体心脏缺血/再灌注损伤Langendorff灌注模型,N组及D组采用平衡灌注20 min,续灌15 min,缺血30 min,再灌注60 min,七氟醚预处理组采用平衡灌注20 min,含2.4%七氟醚的K-H液预处理10 min,洗脱5 min,缺血30 min,再灌注60 min。比较各组平衡末及再灌注15 min、30 min、60 min心率（HR）、左心室发展压（LVDP）、左心室舒张末压（LVEDP）、左心室内压最大上升和下降速率（±dp/dtmax）和再灌注末心肌梗死面积。结果平衡末N组与N＋S组间和D组与D＋S组间心功能指标（基础值）差异无统计学意义（P〉0.05）,与非糖尿病大鼠相比糖尿病大鼠心功能指标（基础值）明显下降（P〈0.05）。再灌注末N＋S组较N组心功能明显改善,心肌梗死面积减小。而D组与D＋S组以上指标差异无统计学意义。再灌注末D组较N组心功能恢复明显增强,心肌梗死面积减小。结论七氟醚预处理可以减轻非糖尿病大鼠的心肌缺血/再灌注损伤;4周病程的糖尿病大鼠基础心功能下降但对心肌缺血/再灌注损伤的耐受增强,七氟醚预处理不能进一步增强其对缺血/再灌注损伤的耐受性。     

急性缺氧对大鼠心肌组织AMPK磷酸化和糖原含量的影响

目的研究急性缺氧对大鼠心肌组织AMPK磷酸化和糖原含量的影响,探讨急性缺氧时心肌组织的能量代谢状况。方法用随机数字表将16只健康雄性SD大鼠分为平原对照组(n=8)和急性缺氧组(n=8)。急性缺氧组大鼠置于模拟海拔5 000 m高原的低压舱中。24 h后测定2组大鼠血糖、血乳酸以及心肌组织糖原含量,用心导管技术测定大鼠心脏功能,Western blot法检测心肌组织AMPK、磷酸化AMPK(pAMPK)水平以及葡萄糖转运体-4(GLUT4)的表达。结果与平原对照组相比较,急性缺氧组大鼠肺动脉压显著升高,右心室功能显著增强,左心室功能无明显变化;血糖含量显著升高[(5.6±0.6)mmol/Lvs(7.5±0.5)mmol/L,P<0.05];左、右心室心肌组织GLUT4表达显著增强,糖原含量显著增加[右心室心肌:(4.78±1.29)mg/gvs(6.55±1.20)mg/g,P<0.05;左心室心肌:(4.15±0.77)mg/gvs(5.73±1.57)mg/g,P<0.05];左、右心室心肌组织AMPK含量无明显变化,但pAMPK含量显著降低,pAMPK/AMPK比值显著降低(P<0.05)。结论模拟高原5 000 m急性缺氧静息状态下心肌组织AMPK磷酸化水平降低,说明心肌能量供求处于平衡状态,心肌糖原含量增加可能是AMPK磷酸化水平降低的机制之一。     

Heart wall myofibers are arranged in minimal surfaces to optimize organ function

Heart wall myofibers wind as helices around the ventricles, strengthening them in a manner analogous to the reinforcement of concrete cylindrical columns by spiral steel cables [Richart FE, et al. (1929) Univ of Illinois, Eng Exp Stn Bull 190]. A multitude of such fibers, arranged smoothly and regularly, contract and relax as an integrated functional unit as the heart beats. To orchestrate this motion, fiber tangling must be avoided and pumping should be efficient. Current models of myofiber orientation across the heart wall suggest groupings into sheets or bands, but the precise geometry of bundles of myofibers is unknown. Here we show that this arrangement takes the form of a special minimal surface, the generalized helicoid [Blair DE, Vanstone JR (1978) Minimal Submanifolds and Geodesics 13-16], closing the gap between individual myofibers and their collective wall structure. The model holds across species, with a smooth variation in its three curvature parameters within the myocardial wall providing tight fits to diffusion magnetic resonance images from the rat, the dog, and the human. Mathematically it explains how myofibers are bundled in the heart wall while economizing fiber length and optimizing ventricular ejection volume as they contract. The generalized helicoid provides a unique foundation for analyzing the fibrous composite of the heart wall and should therefore find applications in heart tissue engineering and in the study of heart muscle diseases.     

Early prediction of myocardial viability after acute myocardial infarction by two-dimensional speckle tracking imaging

Background Identifying the transmural extent of myocardial necrosis and the degree of myocardial viability in acute myocardial infarction (AMI) is important clinically. The aim of this study was to assess myocardial viability using two-dimensional speckle tracking imaging (2D-STI) in patients with AMI. Methods 2D-STI was performed at initial presentation, three days, and six months after primary percutaneous coronary intervention (PCI) in 30 patients with AMI, who had a left anterior descending coronary artery (LAD) culprit lesion. In addition, 20 patients who had minimal stenotic lesions (< 30% stenosis) on coronary angiography were also included in the control group. At six months dobutamine echocardiography was performed for viability assessment in seven segments of the LAD territory. According to the recovery of wall motion abnormality, segments were classified as viable or non-viable. Results A total of 131 segments were viable, and 44 were nonviable. Multivariate analysis revealed significant differences between the viable and nonviable segments in the peak systolic strain, the peak systolic strain rate at initial presentation, and peak systolic strain rate three days after primary PCI. Among these, the initial peak systolic strain rate had the highest predictive value for myocardial viability (hazard ratio: 31.22, P < 0.01). Conclusions 2D-STI is feasible for assessing myocardial viability, and the peak systolic strain rate might be the most reliable predictor of myocardial viability in patients with AMI.     

多巴胺受体2减轻离体大鼠心肌缺血/再灌注损伤

目的 观察多巴胺受体2(DR2)对离体大鼠心肌缺血/再灌注(I/R)损伤的影响及其可能机制.方法 将大鼠40只,每组n=10,随机分成对照组(control)、I/R组、10 pmol/L Bromocriptine(DR2激动剂)组(Bro),10 μmol/L Haloper-idol(DR2抑制剂)组(Hal).用Langendorff离体灌流装置,复制大鼠心肌I/R损伤模型.Powerlab生理记录仪记录心功能;比色法测定冠脉流出液LDH、CK活性和心肌组织匀浆SOD活性以及MDA含量;TUNEL染色检测心肌细胞凋亡;Western blot检测DR2、Bcl-2、caspase-3和caspase-9蛋白的表达.结果 与对照组比较,I/R组DR2、Bcl-2、caspase-3和cmpase-9蛋白表达、LDH和CK活性、MDA含量和细胞凋亡率均增加(P＜0.01),唯有SOD活性降低,心功能减弱(P＜0.01).与I/R组比较,Bro降低LDH和CK活性、MDA含量、细胞凋亡率、caspase-3和caspase-9的表达,升高SOD活性,改善心功能和进一步增加Bcl-2的表达(P ＜0.01);Hal对上述指标影响不显著.结论 DR2可减轻心肌I/R损伤,其机制与抗氧化、清除自由基、上调Bcl-2表达以及下调caspase-3和caspase-9的表达有关.     

Loss of dystrophin staining in cardiomyocytes: a novel method for detection early myocardial infarction

Myocardial infarction (MI) is the most frequent diagnosis made in majority of sudden death cases subjected to clinical and medicolegal autopsies. When sudden death occurs at a very early stage of MI, traditional macroscopic examination, or histological stains cannot easily detect the myocardial changes. For this reason we propose a new method for detecting MI at an early stage. Murine model of MI was used to induce MI through permanent ligation of left anterior descending branch of left coronary artery. Five groups of C57B6/J mice were used for inducing MI, which includes 20 minutes, 30 minutes, one hour, four hours and 24 hours post MI groups. One naïve group and sham-operated groups were used as controls. There is loss of dystrophin membranous staining in cardiac myocytes occurs as early as 20 minutes post myocardial infarction. This can be used as a novel method to diagnose early myocardial infarction in post mortem cases where diagnosis is unclear. In conclusion, evaluation of immunohistochemical expression of dystrophin represents a highly sensitive method for detecting early myocardial infarction due to the loss of staining in the infarcted areas. Dystrophin immunostaining can also be used to assess myocardial architecture.     

不同小剂量多巴酚丁胺超声心动图与18F-脱氧葡萄糖心肌代谢显像对比检测冠心病左心室收缩功能严重受损患者存活心肌

目的 :与18F 脱氧葡萄糖单光子发射计算机断层摄影术 (SPECT)心肌代谢显像对比 ,评价不同小剂量多巴酚丁胺超声心动图 ,检测冠心病左心室收缩功能严重受损患者存活心肌的准确性和安全性。方法 :冠心病心肌梗死伴左心室收缩功能严重受损 (平均左心室射血分数 0 3 8± 0 0 5 )的患者 3 3例 ,1周内分别进行不同小剂量多巴酚丁胺 [3、5、10 μg/(kg·min) ]超声心动图和99m锝 甲氧基异丁基、18F 脱氧葡萄糖SPECT心肌灌注及代谢显像。图像分析均采用 16节段半定量法。以18F 脱氧葡萄糖SPECT检测结果为标准 ,评价不同小剂量多巴酚丁胺超声心动图检测存活心肌的敏感性、特异性、准确性和安全性。结果 :3 3例患者的 3 65个运动异常节段中存活心肌检出率 :18F 脱氧葡萄糖SPECT心肌代谢显像检出的存活心肌节段为 67 4% ,多巴酚丁胺 3、5和 10 μg/(kg·min)分别为 3 8 9%、61 4%和 70 4%。多巴酚丁胺 3 μg/(kg·min)检出的存活心肌节段显著低于18F 脱氧葡萄糖SPECT心肌代谢显像检出的存活心肌节段 (P <0 0 0 1)。多巴酚丁胺 3、5、10μg/(kg·min)超声心动图检出存活心肌的敏感性分别为 5 1 6%、82 9%和 91 8% ,准确性分别为 63 6%、81 6%和87 8% ,均显著递增 (P <0 0 5～ 0 0 0 1) ;副作用发生率分别     

Effects of coronary revascularisation on myocardial blood flow and coronary vasodilator reserve in hibernating myocardium

OBJECTIVE—Previous studies have suggested that resting myocardial blood flow is within normal limits in most chronically dysfunctional left ventricular segments which improve function after coronary artery revascularisation (hibernating myocardium). The aim of this study was to assess myocardial blood flow and coronary vasodilator reserve in hibernating myocardium before and after coronary revascularisation.
PATIENTS AND METHODS— 30 patients with multivessel coronary disease undergoing coronary revascularisation (21 patients with bypass grafting and nine with coronary angioplasty), and 21 age and sex matched healthy volunteers (controls). Myocardial blood flow (MBF, ml/min/g) was measured by positron emission tomography using oxygen-15 water at rest and after dipyridamole (MBFdip, 0.56 mg/kg in four minutes). Coronary vasodilator reserve was calculated as MBFdip/MBF. Regional wall motion was assessed with echocardiography.
RESULTS—Before revascularisation there were 48 remote and 275 dysfunctional myocardial segments, of which 163 (59%) improved function after revascularisation (hibernating). In hibernating segments coronary vasodilator reserve before revascularisation was significantly lower than in remote segments (1.97 (0.7), p < 0.0001) and controls (3.2 (1.5), p < 0.0001). In hibernating segments, myocardial blood flow remained unchanged after revascularisation (0.94 (0.3) v 0.95 (0.3) ml/min/g, p = 0.3) while coronary vasodilator reserve increased (1.47 (0.7) v 1.98 (1.0), p < 0.0001). Myocardial blood flow was similar in remote, hibernating segments before and after revascularisation and in controls.
CONCLUSIONS—This study confirms that myocardial blood flow at rest in hibernating myocardium is within normal limits in most segments, and that hibernating myocardium is characterised by an impaired coronary vasodilator reserve which improves significantly after coronary revascularisation.


Keywords: hibernating myocardium; myocardial blood flow; heart failure; positron emission tomography     

Administration of the Rho-Kinase Inhibitor Fasudil Before Ischemia or just After Reperfusion,but not 30 min After Reperfusion,Protects the Stunned Myocardium in Swine

OBJECTIVES: We assessed the effect of administration time for fasudil treatment of the stunned myocardium in 40 anesthetized open chest swine. MATERIALS AND METHODS: All swine were subjected to 12 min ischemia followed by reperfusion to generate stunned myocardium. Group A (n = 11) received saline in place of fasudil both before ischemia and after reperfusion. Group B (n = 10) received 30 min intravenous fasudil at a rate of 13 mug/kg/min starting 45 min before ischemia and received saline after reperfusion. Groups C (n = 10) and D (n = 9) received saline before ischemia, and received fasudil at a rate of 13 mug kg(-1) min(-1) starting just before reperfusion in group C and 30 min after reperfusion in group D. In both groups, treatment lasted 30 min. Myocardial contractility was assessed by percent segment shortening (%SS). RESULTS AND DISCUSSION: Three swine in group A, 2 swine in each of groups B and C, and one swine in group D had ventricular fibrillation or tachycardia after reperfusion and were excluded from further analysis. The changes of %SS from baseline at 90 min after reperfusion in groups B and C were 68 +/- 8% and 75 +/- 8%, respectively, which were significantly higher than in group A or D (47 +/- 10% or 43 +/- 8%). CONCLUSION: We conclude that fasudil administered before ischemia or just after reperfusion, but not 30 min after reperfusion, protects the stunned myocardium.