Pré-condicionamento isquémico remoto do miocárdio: dos mecanismos fisiopatológicos à aplicação na prática clínica

Short periods of myocardial ischemia followed by reperfusion induce a cardioprotective mechanism when the myocardium is subsequently subjected to a prolonged period of ischemia, a phenomenon known as ischemic preconditioning.As well as its application in the myocardium, ischemic preconditioning can also be induced by brief interruptions of blood flow to other organs, particularly skeletal muscle. Transient ischemia induced noninvasively by inflating a cuff on a limb, followed by reperfusion, helps reduce the damage caused to the myocardium by interruption of the coronary circulation.Remote ischemic preconditioning involves activation of humoral and/or neural pathways that open mitochondrial ATP-sensitive potassium channels in the myocardium and close mitochondrial permeability transition pores, making cardiomyocytes less vulnerable to ischemia-induced cell death.This cardioprotective mechanism is now being translated into clinical practice, with positive results in several clinical trials in coronary artery bypass surgery, surgical repair of abdominal aortic aneurysms, valve replacement surgery and percutaneous coronary intervention. However, certain factors weaken the subcellular mechanisms of preconditioning - age, comorbidities, medication, anesthetic protocol - and appear to explain the heterogeneity of results in some studies.Detailed understanding of the pathways involved in cardioprotection induced by ischemic preconditioning is expected to lead to the development of new drugs to reduce the consequences of prolonged ischemia.     

小剂量多巴酚丁胺超声心动图联合心肌声学造影对心肌梗死后存活心肌的诊断价值

目的前瞻性评价小剂量多巴酚丁胺超声心动图(LDDE)联合心肌声学造影(MCE)对心肌梗死后存活心肌的诊断价值。方法对24例心肌梗死者进行静态MCE、LDDE及3个月后静态超声心动图随访分析。MCE和室壁运动均用16段划分法进行目测半定量计分。心肌造影计分(MCS)回声均匀性增强为1分,回声低淡不均匀为0.5分,缺损为0分。室壁运动计分(WMS)用常规计分法。结果随访时,运动改善的心肌节段中MCS1分占49.4%、0.5分占50.6%,对LDDE均有反应;运动无改善的节段MCS0.5分占9.5%,0分占90.5%,对LDDE有反应者占13.3%,无反应占86.7%。预测存活心肌的敏感性、特异性及准确率分别为LDDE86%、86.7%、86.4%;MCE100%、89.7%、94.6%;LDDE联合MCE86.1%、100%、94.0%。结论心肌微血管结构与功能的完善是心肌存活的基本条件。MCE灌注正常和低灌注,且对多巴酚丁胺有反应的心肌有收缩力储备;而对多巴酚丁胺无反应的低灌注或无灌注心肌则多不能恢复收缩功能。LDDE联合MCE能提高检测存活心肌的特异性及准确率。     

经皮穿刺激光心肌血运重建术抗心肌缺血疗效的评价

探讨经皮穿刺激光心肌血运重建术 (PTMR)治疗严重冠心病患者心肌缺血的疗效。选择 2 1例不适应作冠状动脉成形术和旁路移植术的冠心病患者作PTMR ,观察PTMR手术前、后心肌缺血总负荷 (TIB)和缺血性ST段事件(STI) ,缺血阈值 (MIT)及其变异性 (VMIT)的变化。结果 :PTMR术后TIB降低 (1 7.34± 6 .2 3vs 35 .2 6± 4 .58mm·s,P<0 .0 1 ) ,STI发作次数明显减少 (2 1 .53± 7.34vs 42 .31± 6 .82次 ,P <0 .0 1 ) ;最高和最低MIT增加 ,VMIT降低(31 .2 %± 8.1 %vs 36 .1 %± 1 4 .2 % ,P <0 .0 5)。结论 :PTMR术后近期有较好的抗心肌缺血作用     

实验性顿抑心肌的微循环障碍

为了探讨顿抑心肌微循环改变及机制，制备左前降支冠状动脉不同阻断时间(15min和60min)后再灌注犬心肌顿抑模型，在不同观察时间点静脉注射舍全氟丙烷声振白蛋白微泡造影剂，采用二次谐波成像和间歇发射技术行心肌声学造影，计算心肌声学造影图像上心肌视频密度峰值、心肌声学造影曲线上升斜率和曲线早期下降斜率，测定相应时间点冠状静脉窦血乳酸浓度，结果发现，心肌顿抑早期心肌视频密度峰值显著增高，1h后恢复至结扎前水平；再灌注期顿抑区与正常区视频密度峰值比值、心肌声学造影曲线上升斜率比值、心肌声学造影曲线早期下降斜率比值显著高于左前降支冠状动脉结扎前，随着再灌注时间的延长比值逐渐回降；再灌注期冠状静脉窦血乳酸浓度明显增高。以上结果提示，心肌顿抑早期心肌微循环处于“高动力”状态，血流灌注增加与排空加快并存；顿抑心肌缺氧代谢加强；心肌内微循环短路可能是心肌顿抑微循环障碍的机制。     

经静脉心肌声学造影评价心肌梗死后存活心肌的价值

目的　探讨经静脉心肌声学造影 (MCE)对心肌梗死后存活心肌的诊断价值。方法　 2 4例心肌梗死患者用二维超声评价室壁运动情况 ,同时经静脉进行MCE ,以 3个月后静态超声心动图左室心肌节段性运动改善为依据评价MCE对心肌梗死后存活心肌的诊断价值。结果　在 2 4例病人的 384个心肌节段中 ,运动异常节段 184个。在运动异常的 184个节段中 ,MCE1分 39段 ,0 5分 5 0段 ,0分 95段。 3个月复查 79个节段有运动改善 ,其中 39段来自MCE1分的心肌 ,4 0段来自MCE0 5分的心肌。MCE对预测心肌梗死后室壁运动改善的敏感性、特异性、阳性预测值、阴性预测值及准确率分别为 :10 0 %、89 7%、84 8%、10 0 %和 94 6 %。结论　MCE能比较准确地预测心肌梗死后心肌的存活性     

心肌生长因子对兔实验性心肌梗死范围的影响

目的 :研究心肌生长因子 ( MGF)对兔心肌梗死范围的影响。方法 :用心电图 ST段抬高总值、ST段抬高≥ 2 mm导联数和病理性 Q波导联数标测法结合硝基四氮唑蓝大体标本染色观测MGF对高位双重结扎兔冠状动脉前降支后造成的急性心肌梗死范围的影响。结果 :在结扎冠状动脉前降支 7d内 ,MGF大剂量组及小剂量组均能使结扎前降支所引起的 ST段抬高减轻 ,ST段异常抬高导联数减少 ,病理性 Q波数减少 ,ST段恢复至等电位线的时间提前 ,升高的肌酸激酶值降低 ,梗死心肌重量占左室重量的百分率减小 ,与生理盐水对照组比较有显著性差异 ( P <0 .0 5 )。结论 :MGF能缩小兔实验性心肌梗死范围。     

心肌梗塞溶栓治疗对某些神经内分泌递质的影响

目的 探讨急性心肌梗塞患者早期冠状动脉（冠脉）再灌注对循环中内皮素、心钠素及肾素－血管紧张素系统的影响。方法 接受静脉溶栓治疗的３１例急性心肌梗塞（ＡＭＩ）患者在发病后１２、２４、４８小时、第７及１４天分别取血测定血浆中内皮素、心钠素、肾素、血管紧张素Ⅱ、醛固酮及血管紧张素转换酶。依冠脉早期再灌注指标，将患者分为再灌注组（Ａ组）和非再灌注组（Ｂ组）。比较两组患者血中神经内分泌递质的动态变化。并设正     

PCI术前后 GLP-1受体激动剂治疗对ST段抬高心肌梗死心肌保护作用

心肌细胞凋亡的激活决定最终的心肌梗死（myocardial infarction,MI）大小、心室重构以及死亡率[1]。过去10年间,基础研究报道了葡萄糖一胰岛素一钾输液具有抗细胞凋亡作用。有些临床试验利用此输液来治疗sT段抬高心肌梗死。但因大部分试验中发现疗效欠佳或无效而在临床上停止使用此疗法[2]。     

激光心肌血运重建术后激光孔道及心肌血管新生的研究

目的　研究并比较传统激光心肌血运重建术 (T TMLR)与非透壁激光心肌血运重建术(N TMLR)对心肌缺血面积、心肌坏死面积及血管新生的影响。方法　在家兔急性心肌缺血模型中 ,采用伊文氏蓝 氯化三苯基四唑 (TTC)双重染色法测定心肌缺血和心肌坏死面积 ,并通过HE染色观察新生血管的密度。结果　T TMLR和N TMLR术后均可明显缩小心肌缺血面积 ,明显增加新生血管密度 ,二者之间无显著差异 ;T TMLR和N TMLR术后心肌坏死面积无改变。结论　N TMLR可获得与T TMLR相同的效果。通过激光孔道诱导血管新生并缩小心肌缺血面积可能是激光心肌血运重建术的主要作用机制之一 ,而激光孔道是否通畅与其作用机制无关。     

急性前壁心肌梗死患者相关血管再通后血液中成熟型肾上腺髓质素变化研究

目的探讨急性心肌梗死(AMI)再灌注后,有活性的成熟型肾上腺髓质素(AM)在冠状窦-主动脉差值是否有变化。方法对146例首次发生急性前壁心肌梗死患者和51例冠状动脉造影阴性作对照。入选的心肌梗死患者症状出现后24 h内完成冠状动脉腔内成形术(PICA)的再灌注治疗。再灌注后取主动脉和冠状窦血,测定血浆AM的两种分子形态(AM-m和AM-Gly)。结果AMI患者主动脉和冠状窦血浆AM-m,AM-Gly水平明显高于对照组[(1．7±1．4)pmol／L比(0．4±0．3)pmoL／L,P<0．01]。AMI患者血浆AM-m水平的冠状窦-主动脉差值明显高于对照组,而AM- Gly在两组之间差异无统计学意义(P=0．30)。AM-m的冠状窦-主动脉差值,在伴有左心室功能障碍的AMI患者(n=49)明显高于不伴有左心室功能障碍的AMI患者(n=97)。主动脉和冠状窦的血浆AM-m水平与左室射血分数呈负相关(r=-0．50,r=-0．48,P<0．01)。结论AMI再灌注后,尤其伴有严重左心室功能障碍的患者冠状动脉循环血液中AM的有活性的成熟型(AM-m)合成加速,提示AMI再通后AM经自分泌和(或)旁分泌可能对心血管起保护作用。     

Ischaemic heart disease in pregnancy

Ischaemic heart disease (IHD) in pregnancy, particularly myocardial infarction (MI), is a rare yet potentially fatal condition for the mother and the foetus. With delays in the age of conception, the changes in some social habits among females including cigarette and shisha smoking in addition to an increased prevalence of diabetes mellitus, IHD may represent a real hazard among pregnant women in the near future. The difficulty in the diagnosis emerges from the similarity of the signs and symptoms of ischaemia and infarct to some of the physiological adaptations that occur in a normal pregnancy. The physiological changes that are normal in pregnancy may aggravate pre-existing disease and may unmask some underlying unrecognized coronary vascular changes; therefore, the diagnosis requires a high index of suspicion and careful assessment of the underlying risk factors. The management of IHD always requires a multidisciplinary team approach. The management of each patient should be individualized according to the clinical condition, the risk factors, and the availability of the necessary support. Pregnancy after MI may be an acceptable and reasonably safe option provided the cited criteria are met. A systematic PubMed search was performed to identify all published data including cases reports, small series and systematic reviews in the existing literature. These publications were comprised of both retrospective and cross sectional population studies to maximize the number of cases considered in order to reach conclusions and make recommendations based on the best available evidence considering the rare occurrence of this event. The epidemiology, diagnosis, medical and surgical treatment, and prognosis of IHD in pregnancy are the subjects of the present review.     

Prognostic implications of evaluation of contractile reserve in akinetic and hypokinetic segments during low dose dobutamine echocardiography in patients with acute myocardial infarction

Background: Previous studies have reported the prognostic value of myocardial viability (MV) detected using low-dose dobutamine echocardiography (DbE). However, viability was frequently evaluated as improvement in regional wall motion score index, which includes increased function in hypokinetic segments, in which viable myocardium is necessarily present. It is not known whether an evaluation focusing on akinetic segments, in which the possible presence of viable myocardium is unknown, might have more prognostic value. The aim of this study was to compare the prognostic value of the improvement of myocardial function during dobutamine infusion in akinetic and hypokinetic regions in patients with acute myocardial infarction (AMI). Methods: 191 patients with uncomplicated AMI and at least one akinetic segment were retrospectively selected from those consecutively examined at our echo-laboratory to evaluate MV using DbE. Myocardial viability was evaluated both as an increment in RWMSI (ΔRWMSI), which takes into consideration improvement in both akinetic and hypokinetic regions, and as an improvement of function in akinetic (Δ akinetic) and hypokinetic (Δ hypokinetic), segments considered separately. Follow-up evaluation was performed at 30±13 months. Results: On the basis of the ΔRWMSI, 94/191 patients were judged to have myocardial viability, whereas considering myocardial viability in akinetic segments only, 72/191 patients showed viability. At follow-up 18 patients had died (six viable considering ΔRWMSI; three viable considering Δ akinetic). The presence of a previous AMI, the site of AMI, RWMSI and the number of akinetic segments, and ΔRWMSI and Δ akinetic were related to mortality at univariate Cox analysis. At multivariate stepwise Cox regression analysis Δ akinetic, but not Δ hypokinetic proved to be significantly related to mortality. The Kaplan–Meier survival curves were no different in patients with or without viable myocardium evaluated as ΔRWMSI, while they were significantly different considering patients with or without viability in akinetic segments (P=0.04). Conclusion: In conclusion our study confirms the prognostic importance of the evaluation of myocardial viability in infarcted patients. However, it points out that it is the presence of viability in akinetic segments that affects long-term survival in these patients. This supports the hypothesis that other mechanisms, above and beyond the effect on regional wall motion, are involved in the beneficial effects of myocardial viability.     

35例心肌桥心电图的临床分析

目的探讨心肌桥的冠状动脉造影特点和心电图的变化。方法回顾性分析冠状动脉造影中35例心肌桥的临床表现及冠状动脉造影和心电图的特点。结果冠状动脉造影心肌桥的检出率为1％，均位于左前降支，其中1级狭窄5例，2级狭窄12例，3级狭窄18例，16例病人伴有冠状动脉粥样硬化样改变。金部病例均有临床症状，23例有心电图ST-T改变，运动试验阳性8例，可疑阳性5例，3例病人出现与相关心肌桥无关的下壁心肌梗死。16例病人随访0．5～3年，无1例发生与相关血管有关的急性心肌梗死、心源性猝死和急性心衰。结论冠状动脉心肌桥可能导致心肌缺血，引起心绞痛，但预后良好。     

心电图ST段回落结合校正TIMI帧数对心肌微血管灌注的评价

目的 :探讨急性心肌梗死 (AMI)患者血管再通后心肌组织灌注的评价方法。方法 :AMI患者接受成功的冠状动脉内介入治疗后 ,检查术前及术后 1h心电图ST段回落情况 ,并在术后检测校正的TIMI帧数(CTFC) ,观察两者之间的关系。结果 :根据ST段回落程度将患者分为 3组 ,ST段完全回落组的CTFC较低 ,术后 1个月检查射血分数恢复较好 ;无ST段回落组CTFC较高 ,射血分数值较低 ;ST段部分回落组介于两者之间。结论 :CTFC是目前临床上较理想的评价心肌微血管灌注的指标之一 ,它联合心电图ST段回落可更好地预测AMI患者的危险度 ,为是否需要进一步治疗提供可靠的依据     

心肌声学造影定量心肌血流判断存活心肌的实验研究

目的　评价经静脉心肌声学造影 (MCE)判断存活心肌的可行性。方法　建立急性心肌梗死犬模型 ,经外周静脉持续滴注微泡造影剂 ,通过计算A·β值测定心肌相对血流量。以放射性微球法测定的心肌血流量 (MBF)为标准 ,了解A·β值测定MBF的准确性。通过A·β值估测心肌存活与否 ,病理检查验证其可靠性。结果　放射性微球法所测的正常区、缺血区、坏死区的MBF分别为 ( 1 5± 0 3)、( 0 7± 0 3)、( 0 3± 0 2 )ml·min-1·g-1;MCE测得的A·β值分别为 5 2 46± 15 0 9、2 4 36±3 89、3 74± 3 80 ;正常区、缺血区、坏死区的MBF和A·β值“标化”后分别为 1 0± 0 0、0 44± 0 17、0 17± 0 11和 1 0± 0 0、0 48± 0 0 9、0 0 7± 0 0 8,二者的相关性良好 (r=0 81,P =0 0 0 1)。MCE对坏死心肌的判定结果与病理结果吻合。结论　心肌声学造影可用于活体状态下评价存活心肌 ,“标化”后的A·β值 <0 2 3提示心肌坏死。     

前列地尔后处理对离体大鼠缺血再灌注损伤心肌的影响

目的:采用Langendorff离体心脏灌注模型,探讨前列地尔后处理对离体大鼠缺血再灌注损伤心肌的影响及其机制。方法:24只SD大鼠随机分为:缺血再灌注损伤组(IR组)、前列地尔预处理组(ALP-PreC组)、前列地尔后处理组(ALP-PostC组),每组8只。检测平衡液灌注末及再灌注后不同时间点心功能、冠脉流出液及再灌注末心肌组织中生化指标和心肌梗死面积百分比。结果:平衡末,冠脉流出液中乳酸脱氢酶(LDH)、肌酸激酶(CK)、肿瘤坏死因子(TNF)-α含量,各组间无显著性差异(P均>0.05),再灌注后各组LDH、CK、TNF-α均有显著增加,再灌注后ALP-PreC组和ALP-PostC组各时间点的CK、LDH、TNF-α释放量均明显低于IR组(P<0.05)。ALP-PreC组和ALP-PostC组超氧化物歧化酶(SOD)活性显著高于IR组(P<0.01),丙二醛(MDA)含量低于IR组(P<0.05)。ALP-PreC组和ALP-PostC组心肌梗死面积百分比明显低于IR组(34.48%、32.84%比39.29%,P<0.05),ALP-PreC组和ALP-PostC组之间差别无显著性(P>0.05)。结论:前列地尔后处理可以对缺血再灌注心肌发挥保护作用,其机制可能与抑制早期炎症反应,抑制再灌注后氧自由基的过量生成,增强心肌抗氧化能力,从而发挥保护作用。     

超声心肌造影同步检测犬顿抑心肌血流灌注的实验研究

目的　探讨心肌超声造影评判心肌顿抑的可能性和价值。方法　结扎犬左前降支冠状动脉不同时间 (1 5、6 0min)后再灌注 1 2 0min ,在不同观察时间点静脉注射含全氟丙烷声振白蛋白微泡造影剂 ,采用二次谐波成像和间歇发射技术行心肌超声造影 ,以心肌视频密度峰值表示心肌血流灌注 ,顿抑区与正常区视频密度峰值比值表示顿抑区相对血流灌注。每次心肌超声造影后 ,用超声诊断仪测得心肌节段室壁厚度 ,计算室壁节段收缩期增厚百分率。实验完毕后 ,心肌标本行氯化三苯四唑染色和普通病理切片HE染色光镜检查。结果　 (1 )动物心肌顿抑模型建立的成功率1 0 0 %。 (2 )两组再灌注前缺血心肌节段收缩期增厚百分率显著下降 ,再灌注后逐渐改善 ,但至再灌注1 2 0min尚未恢复至结扎前水平。 (3)两组再灌注早期顿抑心肌视频密度峰值增高 ,随后逐渐恢复至结扎前水平 ;两组再灌注期心肌视频密度峰值比值的变化与顿抑心肌变化相似 ,惟恢复较慢。结论　心肌超声造影结合超声心功能测定能可靠地评判心肌顿抑。