缺血预处理对糖尿病大鼠心肌梗死和细胞因子的影响

目的 观察大鼠心肌梗死面积和细胞相关因子的变化,探讨缺血预处理（IP）对缺血－再灌注（I／R）糖尿病大鼠心肌的保护作用。方法 向健康SD大鼠腹腔内注射链脲佐菌素（每只60mg/kg）制造糖尿病大鼠模型。2d后测定血糖,将血糖≥11．1mmol/L定为糖尿病鼠,共39只。2周后,麻醉大鼠。开胸结扎冠状动脉左前降支（LADCA）复制IP和I／R模型。将39只糖尿病大鼠分为IP组、非缺血预处理（NIP）组、对照组,每组13只。记录Ⅱ导联心电图,测定心腔血清肌酸激酶同工酶（CK－MB）、白细胞介素－8（IL－8）、肿瘤坏死因子α（TNFα）、心肌组织丙二醛（MDA）、超氧化物歧化酶（SOD）含量。取心脏切片染色,计算心肌缺血范围和心肌坏死范围。结果 IP组和NIP组间心肌缺血范围分别为46．6％和48．6％,无显著性差异,心肌坏死范围分别为64．8％和32．6％9P＜0．01）。IP组再灌注期室性心律失常减少,尤其是室颤较NIP组显著减少52．9％（P＜0．01）。IP组CK－MB和TNFα及MDA显著低于NIP组（P＜0．05）。结论 缺血预处理可通过减少TNFα和抗氧化作用,减少心肌坏死范围和降低糖尿病大鼠室颤的发生,从而减轻糖尿病大鼠心肌I／R的严重损害。     

High-frequency electrocardiogram as a supplement to standard 12-lead ischemia monitoring during reperfusion therapy of acute inferior myocardial infarction

Background

Resolution of ST-segment elevation in the electrocardiogram (ECG) is used as a reperfusion sign during thrombolytic therapy in acute myocardial infarction. Analysis of high-frequency QRS components (HF-QRS) might provide additional information. The study compares changes in HF-QRS (150-250 Hz) to ST-segment changes in the standard ECG during thrombolytic therapy.

Methods

Twelve patients receiving intravenous thrombolytic therapy were included. A continuous 12-lead ECG recording was acquired for 4 hours.

Results

After 1 hour of therapy, 3 patients showed ST-elevation resolution as well as an increase in HF-QRS. These changes in ST and HF-QRS occurred simultaneously. No other patient showed significant changes in ST or HF-QRS after 1 hour. After 2 and 4 hours, there was less concordance between the standard and high-frequency ECGs.

Conclusions

In patients with early ST-elevation resolution, the standard and high-frequency ECGs show similar results. Later changes are more disparate and may provide different clinical information.     

Value and limitations of exercise radionuclide angiography for detecting myocardial ischemia in healed myocardial infarction

Exercise radionuclide angiography was performed in 65 normal subjects (group I), in 31 patients with exercise-induced transient thallium defects after acute myocardial infarction (AMI) (group II), and in 16 patients without exercise-induced transient thallium defects, angina or electrocardiographic changes after AMI (group III). Absolute left ventricular (LV) volumes were measured using a correction for attenuation in each patient. Similar peak heart rate-blood pressure products were achieved in groups II and III. Although the mean LV ejection fraction (EF) response to exercise in group III (increase of 0.11 +/- 0.10 units) closely resembled that of normal persons (increase of 0.14 +/- 0.09 units) and was significantly different from that of group II (decrease of 0.04 +/- 0.12), there was considerable individual variation. An abnormal EF response to exercise, defined as failure of EF to increase by at least 0.05 units, was found in 6 subjects (9%) in group I, 26 patients (84%) in group II, and 2 patients (13%) in group III. End-systolic volume failed to decrease in 10 subjects (15%) in group I, 25 patients (81%) in group II and 7 patients (44%) in group III. New regional wall motion abnormalities were found in no subject in group I, in 16 patients (52%) in group II and in only 1 patient (6%) in group III. Thus, although group responses of EF or end-systolic volume appeared to correlate with the presence or absence of ischemia, some patients with exercise-induced transient thallium defects after AMI responded normally to exercise radionuclide angiography stress testing and some patients without other evidence of exercise-induced ischemia after AMI responded to exercise radionuclide angiography testing abnormally.(ABSTRACT TRUNCATED AT 250 WORDS)     

小鼠心肌缺血再灌注损伤模型制备及心肌梗死面积评价方法学比较

目的对小鼠心肌缺血再灌注损伤模型制备及心肌梗死面积评价方法进行比较。方法40只雄性BAB/c小鼠按完全随机设计方法分为传统方法组和改良方法组,传统方法组的心肌再灌注操作采用再次开胸、松开结扎线的方法,改良方法组的心肌再灌注操作为在体外松开结扎线,无需再次开胸。采用伊文思蓝-TTC双染色方法区分缺血再灌注损伤后心肌的梗死区(IA)、缺血危险区(AAR)和左心室总面积(LV)。同时采用传统算法和质量权重法计算心肌梗死面积,质量权重法即在传统算法的基础上,用切片中各区域面积乘以该片心肌质量的百分比,累加各切片的相应区域面积,再计算百分比。结果无论采用哪种算法,传统方法组与改良方法组心肌梗死面积(IA/AAR)差异无统计学意义(传统算法:传统方法组44.43%±2.28%,改良方法组44.24%±1.68%,P=0.96;质量权重法:传统方法组51.74%±2.26%,改良方法组54.51%±1.14%,P=0.23)。与传统方法组相比,改良方法组术后存活率高、麻醉剂使用剂量小、苏醒时间短(均为P<0.05)。此外,采用质量权重法计算AAR/LV、IA/AAR数据的标准差显著小于传统算法(AAR/LV:传统算法标准差2.90,质量权重法标准差1.24;IA/AAR:传统算法标准差2.22,质量权重法标准差:1.00)。结论与传统方法相比,改良方法能够更加稳定、有效地制备小鼠心肌缺血再灌注模型。此外,采用质量权重法计算的心肌梗死面积数据比传统方法准确性更高。     

铁坏死:缺血/再灌注后心肌细胞死亡的一种新方式

铁坏死是一种新的细胞死亡方式,受到细胞内多条信号通路严密调节,包括铁稳态调节途径、胱氨酸谷氨酸反向转运体途径和电压依赖性阴离子通道途径等。虽然有证据表明铁坏死参与了心肌缺血/再灌注损伤,但仍有许多问题尚待解决,如铁坏死主要发生在缺血/再灌注的哪个阶段?铁坏死的发生是否必须有铁离子参与?阐明铁坏死的发生过程和机制对于寻找防治心肌缺血/再灌注损伤新药具有重要意义。     

大鼠急性心肌缺血/再灌注模型改良方法与传统方法的比较

目的:建立大鼠急性心肌缺血/再灌注模型的改良方法与传统方法并进行比较。方法:将60只SD大鼠随机分为两组,每组30只;一组采用改良方法建立模型,即气体麻醉,以气体麻醉面罩通气,短时间开胸;另一组采用传统方法建立模型,即腹腔麻醉,气管插管,长时间开胸。比较两种方法的手术时间、手术成功率、术中血氧饱和度、术后存活率、心肌梗死面积,以及术后大鼠的生活状况。结果:与传统方法组相比,改良方法组大鼠术中存活率升高[(93.3±4.6)%vs.(72.4±8.4)%,P0.05]、开胸时间缩短为[(6.5±2.0)minvs.(44.9±2.7)min,P0.01],开胸前后平均血氧饱和度增加[(96.3±0.8)%vs.(90.9±2.1)%,P0.05],术后存活率提高(82.83%vs.58.3%,P0.01)。另外改良方法组大鼠术后恢复正常行为活动需要的时间较短,但两组大鼠心肌梗死的面积[(33.5±2.2)%vs.(35.0±3.0)%]无统计学意义。结论:改良方法具有简单、高效及可独立操作的优点,能有效提高建立大鼠急性心肌缺血/再灌注模型的成功率。     

The predictive value of the electrocardiographic pattern of acute q-wave myocardial infarction for recurrent ischemia

Atotal of 140 consecutive patients with acute Q-wave myocardial infarction was evaluated to assess the relationship between different electrocardiographic patterns of evolution and the incidence of recurrent ischemia within 10 days of infarction. Patients were allocated to three groups according to the electrocardiogram at 12 h after admission: Group A: ST elevation of < 2 mm and negative T waves (75 patients); Group B: ST elevation of > 2 mm and negative T waves (35 patients); Group C: ST elevation of > 2 mm and positive T waves (30 patients). Patients in Group C had more anterior wall infarctions (82%) than Group A (40%) or Group B (58%) (p = 0.0001). Peak creatine kinase levels were lower in Group A (782 ± 115 IU) than in Groups B (1415 ± 257 IU) and C (1501 ± 287 IU) (p<0.0001). The occurrence of post-infarction recurrent ischemia was more frequent in Group A (79.2%) than in Groups B (33.3%) and C (14.8%) (p<0.0001). Patients in Group A had relatively smaller infarctions and a higher incidence of recurrent ischemia, whereas patients in Group C had larger infarctions and a lower incidence of recurrent ischemia. The electrocardiographic pattern 12 h after admission for acute myocardial infarction is helpful in identifying a subgroup at high risk of recurrent ischemia.     

The prevalence and prognosis of unrecognized myocardial infarction and silent myocardial ischemia in patients undergoing major vascular surgery

OBJECTIVE: The aim of this study is to determine the prevalence and prognosis of unrecognized myocardial infarction (MI) and silent myocardial ischemia in vascular surgery patients. METHODS: In a cohort of 1092 patients undergoing preoperative dobutamine stress echocardiography and noncardiac vascular surgery, unrecognized MI was determined by rest wall motion abnormalities in the absence of a history of MI. Silent myocardial ischemia was determined by stress-induced wall motion abnormalities in the absence of angina pectoris. Beta blockers and statins were noted at baseline. During follow-up (mean: 6+/-4 years), all-cause mortality and major cardiac events (cardiac death or nonfatal MI) were noted. RESULTS: The prevalence of unrecognized MI and silent myocardial ischemia was 23 and 28%, respectively. Both diabetes and heart failure were important predictors of unrecognized MI and silent myocardial ischemia. During follow-up, all-cause mortality occurred in 45% and major cardiac events in 23% of patients. In multivariate analysis, unrecognized MI and silent myocardial ischemia were significantly associated with increased risk of mortality [hazard ratio (HR), 1.86; 95% confidence interval (CI), 1.53-2.25 and HR, 1.74; 95% CI, 1.46-2.06, respectively] and major cardiac events (HR, 2.15; 95% CI, 1.59-2.92 and HR, 1.86; 95% CI, 1.43-2.41, respectively). In patients with unrecognized MI, beta-blockers and statins were significantly associated with improved survival. Statins improved survival in patients with silent myocardial ischemia. CONCLUSIONS: In patients undergoing major vascular surgery, unrecognized MI and silent myocardial ischemia are highly prevalent (23 and 28%) and associated with increased long-term mortality and major cardiac events.     

Dobutamine stress echocardiography for assessment of myocardial viability and ischemia in acute myocardial infarction treated with thrombolysis

To evaluate the role of dobutamine echocardiography for early assessment of myocardial viability and ischemia in acute myocardial infarction (MI), 59 patients with thrombolyzed acute MI underwent low- (5–10 μg/kg/min, 8 patients) and high-dose (20–40 μg/kg/min, 51 patients) dobutamlne echocardiography at a mean of 8 ± 4 days after acute MI. Myocardlal viability in the infarct zone was documented in 43 of 59 (73%) patients (group 1), in whom mean asynergy score index decreased from 1.6 ± 0.3 at baseline to 1.3 ± 0.2 (p < 0.001), after low-dose dobutamine. No viability was present in 16 of 59 (27%) patients (group 2). At follow-up, recovery of regional contractile function was observed in group 1 (asynergy score index decreased from 1.6 ± 0.3 to 1.4 ± 0.3; p < 0.001), but not in group 2 patients. Sensitivity, specificity, and negative and positive predictive values of low-dose dobutamine echocardiography in predicting spontaneous recovery of function were 79%, 68%, 50%, and 89%, respectively. Of the 51 patients who underwent high-dose dobutamine, 26 of 36 (72%) group 1 patients showed a deterioration of contractility in the infarct zone indicative of myocardlal ischemia compared with only 1 of 15 (7%) group 2 patients. At follow-up, recovery of regional function was greater in patients with no evidence of myocardlal ischemia at high doses than in those with an ischemic response. Thus, in patients with thrombolyzed acute MI, dobutamine echocardiography is a useful clinical tool for detection of myocardlal viability and ischemia in the infarct zone and for identification of patients with jeopardized myocardium in the area at risk who can benefit from myocardlal revascularlzation.     

Comparative accuracy of computerized spatial vectorcardiography and standard electrocardiography for detection of myocardial infarction

New computerized spatial vectorcardiographic variables were analyzed by discriminant analyses for group classification of 94 patients with acute myocardial infarction and 79 normal subjects. Using the integral of the sequential magnitudes of the spatial vectors during the period of initial abnormal depolarization (IAD) of the QRS at a discriminating value of 3 mv X msec., 87% of the subjects were correctly classified with a sensitivity of 85%; specificity of 88%; and an overall predictive accuracy of 87%, p less than .00001. The period of initial abnormal depolarization in which the vectors were integrated was determined by the first derivative of the sequential magnitudes of the spatial vectors of the QRS waveform (dm/dt). The mean value of dm/dt during the period of abnormal depolarization was a poor discriminating variable. The predictive accuracy of this new electrocardiographic criterion for diagnosis of myocardial infarction compared favorably with other computerized methods such as vectorcardiography, polarcardiography, Aitoff spatial trajectory, the 12-lead ECG derived by the Frank XYZ leads as well as the standard 12-lead ECG.     

Ranolazine: new paradigm for management of myocardial ischemia, myocardial dysfunction, and arrhythmias

Ranolazine, which was approved by the US Food and Drug Administration in January 2006, provides a mechanism of action to treat ischemia that has not hitherto been available. Ranolazine is effective in reducing manifestations of ischemia and angina, and it also holds potential promise to be effective in the management of left ventricular dysfunction, particularly diastolic dysfunction, and arrhythmias. This article provides an update on the available studies concerning the value of ranolazine across the spectrum of cardiovascular disease.     

核素心肌灌注显像与三种心电方法诊断局灶性心肌梗死的对比研究

目的 :对比评价核素心肌灌注显像与心电图 （ECG）、高频心电图 （HFECG）及体表电位标测 （BSPM）三种心电方法对局灶性心肌梗死的诊断价值。方法 :采用结扎法 ,建立 10只局灶性心肌梗死犬动物模型。术后 2周 ,依次行核素心肌灌注显像、ECG,HFECG及 BSPM检查 ,术前行 HFECG和 BSPM检查 ,以作对比。结果 :ECG和HFECG检测局灶性心肌梗死的阳性率较低 ,仅为 5 0 % ,BSPM各单项参数检出的阳性率高于 ECG和 HFECG,多项指标平行试验诊断的敏感性与核素心肌显像相当 ,均为 90 %。结论 :BSPM和核素心肌显像对局灶性心肌显像均有较高的诊断价值 ,且核素心肌显像又能直观地反映梗死部位、范围和程度。     

New electrocardiographic criteria for posterior wall acute myocardial ischemia validated by a percutaneous transluminal coronary angioplasty model of acute myocardial infarction

The standard 12-lead electrocardiogram (ECG) fails to detect ST-segment elevation in patients with posterior wall acute myocardial ischemia. However, additional posterior leads V(7-9) provide limited additional diagnostic information to the standard 12-lead ECG when an ischemic criterion of 1-mm ST elevation is used. No study is available to delineate the ischemic criteria in the posterior electrocardiographic leads. Continuous 15-lead ECGs (standard 12 lead + V(7-9)) were recorded in 53 subjects undergoing elective left circumflex coronary angioplasty (posterior ischemia model). ST amplitudes (J + 60 ms) at preangioplasty baseline were subtracted from maximal ST amplitudes during balloon occlusion to create a positive or negative change score (DeltaST) for each of the 15 leads. During 53 left circumflex occlusions, 26 subjects (49%) had DeltaST elevation of > or = 1 mm and 24 subjects (45%) had DeltaST elevation ranging from 0.5 to 0.95 mm in > or = 1 posterior leads. Five subjects (9%) had DeltaST elevation of > or = 1 mm in the posterior leads without DeltaST elevation anywhere in any of the 12 leads. The sensitivity in detecting myocardial ischemia using 15-lead ECGs (58%) was not statistically different from the standard 12-lead ECG (49%) (p = 0.06). Adjusting the ischemic criterion from 1 to 0.5 mm in V(7-9) significantly improved the sensitivity from 49% in the 12-lead ECG to 94% in the 15-lead ECG (p = 0.000). In addition, 12 subjects (23%) had posterior ST-segment elevation without anterior ST-segment depression. Thus, posterior leads V(7-9) contribute significant additional diagnostic information above and beyond the standard 12-lead ECG only when a new ischemic criterion of 0.5 mm instead of 1 mm ST elevation is applied to the posterior leads.     

The accuracy of electrocardiographic Q waves for the detection of prior myocardial infarction as assessed by a novel standard of reference

BACKGROUND: The electrocardiogram (ECG) is valuable for the identification of prior myocardial infarction (MI) in individuals participating in epidemiologic studies or undergoing screening examinations. Although the Minnesota Code, a set of criteria for the interpretation of ECGs in such situations, is commonly used to identify MI in these settings, its accuracy is incompletely understood. HYPOTHESIS: We sought to test the accuracy of the Minnesota Code Q and QS criteria for MI against a new standard of reference, the presence of a perfusion defect on a resting myocardial scintigraphic image. METHODS: The resting myocardial scintigrams of all patients studied in our nuclear cardiology laboratory during 7 consecutive months were screened for the presence of perfusion defects. For each patient with such a defect, two individuals examined on the same day, who had no perfusion defect, were selected as controls. Electrocardiograms recorded within 30 days of the scintigraphy were read blindly by two of the authors using the Minnesota Code criteria for Q or QS waves indicative of MI. RESULTS: For 214 patients selected on the basis of their scintigraphic findings, a satisfactory ECG recorded within a month of the scintigraphy was also available. The overall sensitivity of the Q or QS criteria was 0.58 and the specificity was 0.75. As might be expected when only the most stringent criteria were applied, sensitivity was least and the specificity best. CONCLUSIONS: As in previous studies, in which necropsy material served as the standard of reference, sensitivity of the Q and QS criteria contained in the Minnesota Code is relatively modest and specificity is reasonable but not outstanding.