Application of finite-element analysis with optimisation to assess thein vivo non-linear myocardial material properties using echocardiographic imaging

An application of finite-element analysis with an optimisation technique to assess the myocardial material properties in diastasisin vivo is described. Using the data collected from an animal model, the three-dimensional geometry of the left ventricular chamber, at several times in diastole, was reconstructed. From the measurement of the ventricular chamber pressure during image acquisition, finite-element analysis was performed to predict the expansion during diastasis. Initially, by restricting the motion of the epicardial nodes and computing the reaction forces, an ‘equivalent pericardial pressure’ was determined and applied in subsequent analysis. The duration of diastasis was divided into three or four intervals and the analysis was performed at each interval to assess the material properties of the myocardium. Using such a step-wise linear approach, the non-linear material properties of the myocardium during passive expansion was determined. Our results demonstrated that the computed ‘equivalent pericardial pressure’ increased with and was smaller than the corresponding left ventricularchamber pressure. The passive myocardium exhibited a linear tangent modulus against chamber pressure relationship which is equivalent to an exponential stress/strain relationship, similar to those suggested byin vitro studies.     

缺血后处理与心肌保护

随着心脏外科手术和介入治疗的增加，人们越来越重视其中的主要病理生理过程——心肌缺血再灌注损伤（myocardium ischemic-reperfusion injury，MIRI）。MIRI是指心肌缺血一定时间后即使恢复血液灌注，仍将引起心肌功能障碍和结构损害，表现为致死性再灌注损伤、心肌顿抑、心律失常和能量代谢改变。其发病机制仍未完全阐明，通常认为与氧自由基、钙超载、中性粒细胞、微血管损伤和能量代谢障碍等有关。近年来对其发生机制和防治方法的研究越来越深入，发现缺血后处理（ischemic postconditioning，IPO）。有很好的心肌保护作用。现就IPO对心肌缺血和再灌注损伤的保护作用、可能机制及其意义作一综述。     

腺苷预处理对人未成熟心肌缺血再灌注损伤的保护作用

目的探讨腺苷预处理对人未成熟心肌缺血再灌注损伤的保护作用及其可能机制。方法将42例5岁以下行室间隔缺损修补术的患儿随机分成腺苷组和对照组,每组21例。腺苷组在术前用腺苷预处理,对照组经相同路径滴入相同体积的生理盐水后开始转流。观察心肌肌钙蛋白-I(cTnI)、肌酸激酶同工酶(CK-MB)、心肌超微结构改变,记录和计算两组自动复跳率、T波倒置发生率、室性心律失常发生率、术后平均住院日(d)。结果腺苷预处理明显减少了cTnI、CK-MB的漏出,在心肌超微结构和心电活动方面具有良好的保护作用。结论腺苷预处理对人未成熟心肌缺血再灌注损伤具有保护作用。     

茶多酚对5500m低压条件下吸纯氧引起的小鼠心肌自由基代谢异常的保护作用

目的 观察天然抗氧化剂茶多酚（Tea Polyphenols,TP)对模拟飞行低压吸纯氧引起的小鼠心肌自由基代谢异常的保护作用。方法 42只雄性昆明种小鼠随机分为3组（n=14):对照组（A）、5500m低压吸氧组（B）和TP保护组（C）。B、C两组置于动物低压舱在5500m低压下吸氧（＞96％）,2h/d,3d/wk,共8wk。上舱暴露前,C组灌胃给予TP100mg/kg,另2组给予蒸馏水。末次实验后次日将小鼠断头处死,迅速取出心肌组织。测定心肌超氧化物歧化酶（SOD）活性和丙二醛（MDA）、一氧化氮（NO）含量。另外,用免疫组化法对心肌组织Cu,Zn-SOD和诱生型NO合酶（iNOS)的含量进行定性观察。结果 与对照比较,B组MDA水平、SOD添性和Cu,Zn-SOD酶含量明显升高（P＜0．05）;TP有明显保护作用：降低MDA生成（P＜0．01）,SOD活性和含量恢复正常。与之相反,重复5500m低压吸氧暴露后,心肌NO含量和iNOS表达明显降低。重复给予TP使NO代谢恢复正常。结论 天然抗氧化剂茶多酚对模拟飞行低压吸纯氧引起的心肌自由基代谢异常具有保护作用。     

有氧运动训练后大鼠横纹肌线粒体DNA含量观察

有氧运动训练能使肌肉组织产生适应性变化.从而提高运动耐力.本研究通过不同运动训练方案(无负重游泳3天.60分/天;7天,60分/天;12天,60分/天)、训练及注射钙鳌合剂(EGTA)、氧化剂(GSSG),观察大鼠骨骼肌、心肌线粒体DNA含量的变化规律.结果发现,运动训练3天后,骨骼肌线粒体DNA即表现为增加(57%),7天后降为42%.12天后即不再增加,而此时注射GSSG的训练大鼠线粒体DNA仍增加了26%;心肌线粒体DNA只有在训练12天并注射了GSSG才表现为增加(30%),说明改变细胞内的氧化应激的平衡(有氧运动训练及注射GSSC)可以影响线粒体DNA的生物合成.注射EGTA并训练的大鼠,骨骼肌线粒体则表现为没有显著变化,而在心肌线粒体7天和12天后出现了DNA合成的抑制(-30%,-32%),说明细胞内外的钙平衡也会影响线粒体DNA的生物合成.     

异丙酚或咪达唑仑复合麻醉下心脏手术患者心肌细胞凋亡及术后早期恢复的比较

Objective To compare the cardiomyocyte apoptosis and early postoperative recovery in patients undergoing cardiac valve replacement under propofol-or midazolam-combined anesthesia.Methods Forty NYHA class Ⅱ or Ⅲ patients (aged 48-64 yr and weighing 45-78 kg) undergoing cardiac valve replacement with cardiopulmonary bypass (CPB) were randomly divided into midazolam group (Group M) and propofol group (Group P) (n=20each). The patients were premedicated with morphine 0.1 mg/kg i.v. and scopolamine 0.3 mg i.v. Anesthesia was induced with midazolam 0.2 mg/kg (in Group M) or propofol 2 mg/kg (in Group P) combined with fentanyl 10 μg/kg and vecuronium 0.1 mg/kg, and maintained with propofol 5 mg. kg-1·h-1 (in Group P) or midazolam 0.1 mg·kg-1·h-1(in Group M) and intermittent i.v. boluses of fentanyl and vecuronium after tracheal intubation. The patients were mechanically ventilated with PETCO2 maintained at 35-45 mm Hg. Myocardial tissues were obtained from the right atrium before and after CPB for determination of apoptosis in cardiomyocytes (by TUNEL). The apoptotic index was calculated. The expression of caspase-3 and caspase-9 was determined by immunohistochemical avidin-biotin-peroxidase complex (ABC) technique staining. The mean airway pressure (MAP) and heart rate (HR) were monitored. Aortic cross-clamping time, surgical and CPB times, spontaneous recovery of normal heart beat, emergence from anesthesia, extubation time and duration of ICU stay were recorded and compared between the two groups.Results The percentage of spontaneous recovery of normal heart beat after release of aortic cross clamp was significantly higher and the need for dobutamine support was significantly less in Group P than in Group M ( P ＜ 0.05). The emergence from anesthesia was significantly more rapid, the extubation time and the ICU stay were significantly shorter in Group P than in Group M (P＜0.05). There were no significant differences in apoptosis index and expression of caspase-3 and caspase-9 before CPB between the two groups. The apoptosis index and expression of caspase-3 and caspase-9 were significantly increased after CPB in Group M and significantly higher than those after CPB in Group P (P＜0.05).Conclusion Cardiomyocyte apoptosis in patients undergoing CPB can be inhibited and the postoperative recovery is more rapid under propofol-combined anesthesia.     

Isolated Noncompaction of Ventricular Myocardium: a Magnetic Resonance Imaging Study of 11 Patients

Objective

To retrospectively summarize the cardiac magnetic resonance imaging (CMRI) findings of isolated noncompaction of ventricular myocardium (INVM).

Materials and Methods

Eleven patients (M:F = 9:2; mean age, 35 years) were evaluated. Steady-state free precession (SSFP), fast spin echo (SE) sequence, SSFP cine imaging, and delayed enhanced inversion recovery spoiled gradient echo (IR-SPGR) sequence were used for showing abnormal myocardium, measuring ratio of noncompacted/compacted myocardium layers (NC/C ratio), and detecting myocardial viability. The left ventricle was divided into nine segments and a NC/C ratio > 2.3 in diastole was used as cutoff value in diagnosing left INVM. The right ventricle was assessed qualitatively.

Results

Cardiac MRI indicated left INVM in seven patients, right INVM in one patient and biventricle INVM in three patients. Characteristic CMRI changes included prominent trabeculations, deep intertrabecular recesses and an increase in the NC/C ratio. The most frequently involved segments was left ventricular apex. Three patients had abnormal high signals within the trabecular structures on SE T2 weighted image. One ventricular aneurysm and one apical thrombus were also observed. Delayed enhancement was seen in six of nine patients with subendocardial and transmural patterns.

Conclusion

There are CMRI features that might be characteristic for INVM.     

家兔挤压伤后心肌组织与心功能变化的对比研究

目的通过对家兔挤压伤后心肌病理组织学改变的观察,对比心脏超声技术评价其心脏整体功能的变化情况,讨论挤压伤后对心肌组织继发损伤及心脏整体功能变化的机制。方法采用42只家兔制作挤压伤家兔动物模型,将其随机分为对照组、解压即刻组、解压后6、12、24、48、72 h共7组,每组6只;光镜观察心肌细胞结构。全自动生化分析仪检测血清尿素氮、肌酐、钾离子、钙离子、肌酸激酶、肌红蛋白浓度变化,多功能复合心脏超声测量心脏整体功能。结果挤压伤后12～24 h血清肌酸激酶、肌酸激酶同工酶、肌钙蛋白I显著升高,光镜下可见心肌细胞肿胀、间质水肿等改变。超声检测心脏整体收缩及舒张功能指标均显著下降。结论严重挤压伤后可致心肌组织继发损伤及心功能障碍,在解压后逐渐加重,至解压后12～24 h达到峰值,持续至伤后72 h后逐渐缓解;多功能复合心脏超声技术能够较精准、客观、快捷评估挤压伤后心脏继发受损的情况。     

Cardiac resynchronization therapy evaluated by myocardial scintigraphy with <Superscript>99m</Superscript>Tc-MIBI: changes in left ventricular uptake,dyssynchrony, and function

Purpose   ^99mTc-MIBI gated myocardial scintigraphy (GMS) evaluates myocyte integrity and perfusion, left ventricular (LV) dyssynchrony and function. Cardiac resynchronization therapy (CRT) may improve the clinical symptoms of heart failure (HF), but its benefits for LV function are less pronounced. We assessed whether changes in myocardial ^99mTc-MIBI uptake after CRT are related to improvement in clinical symptoms, LV synchrony and performance, and whether GMS adds information for patient selection for CRT. Methods  A group of 30 patients with severe HF were prospectively studied before and 3 months after CRT. Variables analysed were HF functional class, QRS duration, LV ejection fraction (LVEF) by echocardiography, myocardial ^99mTc-MIBI uptake, LV end-diastolic volume (EDV) and end-systolic volume (ESV), phase analysis LV dyssynchrony indices, and regional motion by GMS. After CRT, patients were divided into two groups according to improvement in LVEF: group 1 (12 patients) with increase in LVEF of 5 or more points, and group 2 (18 patients) without a significant increase. Results  After CRT, both groups showed a significant improvement in HF functional class, reduced QRS width and increased septal wall ^99mTc-MIBI uptake. Only group 1 showed favourable changes in EDV, ESV, LV dyssynchrony indices, and regional motion. Before CRT, EDV, and ESV were lower in group 1 than in group 2. Anterior and inferior wall ^99mTc-MIBI uptakes were higher in group 1 than in group 2 (p<0.05). EDV was the only independent predictor of an increase in LVEF (p=0.01). The optimal EDV cut-off point was 315 ml (sensitivity 89%, specificity 94%). Conclusion  The evaluation of EDV by GMS added information on patient selection for CRT. After CRT, LVEF increase occurred in hearts less dilated and with more normal ^99mTc-MIBI uptake.     

磷酸肌酸对室间隔缺损合并肺动脉高压手术的心肌保护作用

目的观察含血STH2液加入外源性磷酸肌酸(CP)后对室间隔缺损合并肺动脉高压进行室间隔缺损修补术的心肌保护作用。方法20例室间隔缺损合并肺动脉高压患儿随机分为两组,CP治疗组在含血STH2心灌注液中加入CP,对照组用等量含血STH2液,分别在术后16h、第6天,采集患儿静脉血,测磷酸肌酸激酶同工酶(CK-MB)、心肌钙蛋白(cTnT),同时在术后观察呼吸机辅助呼吸时间、第6天检查患儿左室射血分数,肺动脉压力。结果CP治疗组术后CK-MB、cTnT、呼吸机辅助呼吸时间、左室射血分数、肺动脉压力较对照组相比均有明显改善。结论CP加入心停搏液中能显著提高心肌保护作用,同时可间接降低肺动脉压力。