Recording locations in multichannel magnetocardiography and body surface potential mapping sensitive for regional exercise-induced myocardial ischemia

Introduction This study aimed to identify the optimal locations in multichannel magnetocardiography (MCG) and body surface potential mapping (BSPM) to detect exercise-induced myocardial ischemia. Methods We studied 17 healthy controls and 24 coronary artery disease (CAD) patients with stenosis in one of the main coronary artery branches: left anterior descending (LAD) in 11 patients, right (RCA) in 7 patients, and left circumflex (LCX) in 6 patients. MCG and BSPM signals were recorded during a supine bicycle stress test. The capability of a recording location to separate the groups was quantified by subtracting the mean signal amplitude of the normal group from that of the patient group during the ST segment and at the T-wave apex, and dividing the resulting amplitude difference by the corresponding standard deviation within all subjects. Results In MCG the optimal location for ST depression was at the right inferior grid for the RCA, at the mid-inferior grid for the LCX, and in the middle of these locations for the LAD subgroup (mean ST amplitudes: CAD −80 ± 360fT, controls 610 ± 660fT; p < 0.001). In BSPM it was on the left upper anterior thorax for the LAD, left lower anterior thorax for the RCA, and on the lower back for the LCX subgroup (mean ST amplitudes: CAD −39 ± 61 μV and controls 38 ± 38 μV; p < 0.001). In MCG the optimal site for T-wave amplitude decrease was the same as the one for the ST depression. In BSPM it was on the middle front for the LAD, on the back for the LCX and on the left abdominal area for the RCA group. In accordance with electromagnetic theory, the largest ST segment and T-wave amplitude changes took place in MCG in locations orthogonal to those in BSPM. Conclusion This study identified magnetocardiographic and BSPM recording locations which are sensitive for detecting transient myocardial ischemia by evaluation of the ST segment as well as the T-wave. These locations strongly depend on ischemic regions and are outside the conventional 12-lead ECG recording sites. Received: 9 October 2000 / Returned for revision: 23 October 2000 / Revision received: 2 January 2001 / Accepted: 19 January 2001     

运动试验心电图QRS波振幅间期乘积诊断心肌缺血的价值

观察经(99m)~Tc-MIBI心肌灌注断层显像明确有心肌缺血(n=21)和无心肌缺血(n=17)病人的运动试验心电图QRS波振幅(△R_v5和∑_R)、间期及其乘积的变化.心肌缺血组运动后3项指标明显增加(4.1和7.9mm、10.6ms、45.2和88.7mmms);而无心肌缺血组运动后反而下降(-1.4和-2.8mm、-3.4ms、-5.1 和-10.1mmms).QRS波振幅间期乘积运动前后变化与心肌缺血范围关系优于QRS波单纯振幅或间期变化.     

A new screening method to diagnose coronary artery disease using multichannel magnetocardiogram and simple exercise

Background: Magnetocardiography (MCG) is a non-contact mapping technique to record cardiac action currents. The Master's two-step electrocardiogram (ECG) test is a simple exercise method for screening coronary artery disease (CAD), but it is inadequate concerning the sensitivity. Our aim was to develop a new screening method using multichannel MCG instead of ECG. Methods: Thirty subjects (aged 54 ± 16 years, 27 males), 17 of whom had CAD confirmed by coronary angiography, underwent the Master's exercise ECG test. After the exercise, MCG signals were acquired every minute during recovery with a 64-channel MCG system (MC-6400, Hitachi Ltd). We integrated tangential components of the MCG signals within QRS (during 20, 40, 80, and 120 ms centering on R-wave peak) immediately after exercise (Iex) and 5 minutes after exercise (Irec). The exercise-induced change of currents [(Iex-Irec)/Irec] was determined and normalized for each channel, and the maximal change among 64 channels, maximal QRS integral change, was used as a diagnostic index for myocardial ischemia. Results: The maximal QRS integral change during 40 ms was significantly higher in the CAD group than in the control group (0.81 ± 0.51 vs. 0.36 ± 0.19, p < 0.01). A sensitivity and specificity for predicting CAD by the change > 0.44 were 82 % and 85 %, respectively, yielding a diagnostic accuracy of 83 %. The conventional Master's ECG test identified the CAD patients with a diagnostic accuracy of 63 % (sensitivity 47 %, specificity 85 %). Conclusion: The Master's two-step exercise test with a 64-channel MCG system showed the high diagnostic accuracy, despite of non-contact recording and simple exercise. The magnetic field in the depolarization process has the potential to detect the subtle myocardial ischemia induced by exercise. Received: 20 June 2002, Returned for 1. revision: 11 July 2002, 1. Revision received: 3 September 2002, Returned for 2. revision: 25 September 2002, 2. Revision received: 10 October 2002, Accepted: 14 October 2002 Correspondence to: S. Nakatani, MD, PhD     

平板运动试验后心率恢复情况对冠心病的诊断价值

目的评价平板运动试验后心率恢复的意义及其对冠心病的诊断价值。方法76例拟诊冠心病患者行平板运动试验,根据冠状动脉造影结果分为冠心病组和非冠心病组。计算运动后1、2、3、4、5、7min心率恢复值并比较,利用运动后心率恢复异常作为诊断冠心病标准与传统的ST段压低法比较。结果冠心病组的患者运动后各时段心率恢复值均低于非冠心病组。以运动后1、2min心率恢复异常作为诊断冠心病的标准,与传统的ST段压低法相比,其敏感性无差别,特异性较高。结论冠心病组与非冠心病组比较表明,运动后心率恢复存在明显差异,且运动后心率恢复异常可以作为诊断冠心病的方法之一。     

心肺运动试验无创检测心肌缺血的价值

目的:观察心肺运动试验与心电图运动试验在检测肌心缺血方面的价值。方法:对68例胸痛患者行心电图运动试验、心肺运动试验和冠状动脉造影,根据心电图运动试验组与心肺运动试验的结果分别分为阳性组与阴性组,以冠状动脉造影结果为金标准,比较心肺运动试验与心电图运动试验对心肌缺血诊断的阳性率预测值、阴性率预测值、敏感度和特异度。结果:运动试验诊断心肌缺血的敏感性为51.28%,特异性为68.97%,阳性预测值为68.97%,阴性预测值为51.28%,以O2-pulsepeak比值作为诊断心肌缺血的一种预测指标,敏感性为51.28%,特异性为75.86%,阳性预测值为74.07%,阴性预测值为53.66%。结论:在检测缺血方面,心肺运动试验在特异度、阳性预测值和阴性预测值方面均要优于心电图运动试验。     

Electrophysiological characterization of murine myocardial ischemia and infarction

Background Genetically altered mice will provide important insights into a wide variety of processes in cardiovascular physiology underlying myocardial infarction (MI). Comprehensive and accurate analyses of cardiac function in murine models require implementation of the most appropriate techniques and experimental protocols. Objective In this study we present in vivo, whole-animal techniques and experimental protocols for detailed electrophysiological characterization in a mouse model of myocardial ischemia and infarction. Methods FVB mice underwent open-chest surgery for ligation of the left anterior descending coronary artery or sham-operation. By means of echocardiographic imaging, electrocardiography, intracardiac electrophysiology study, and conscious telemetric ECG recording for heart rate variability (HRV) analysis, we evaluated ischemic and post-infarct cardiovascular morphology and function in mice. Results Coronary artery ligation resulted in antero-apical infarction of the left ventricular wall. MI mice showed decreased cardiac function by echocardiography, infarct-typical pattern on ECG, and increased arrhythmia vulnerability during electrophysiological study. Electrophysiological properties were determined comprehensively, but were not altered significantly as a consequence of MI. Autonomic nervous system function, measured by indices of HRV, did not appear altered in mice during ischemia or infarction. Conclusions Cardiac conduction, refractoriness, and heart rate variability appear to remain preserved in a murine model of myocardial ischemia and infarction. Myocardial infarction may increase vulnerability to inducible ventricular tachycardia and atrial fibrillation, similarly to EPS findings in humans. These data may be of value as a reference for comparison with mutant murine models necessitating ischemia or scar to elicit an identifiable phenotype. The limitations of directly extrapolating murine cardiac electrophysiology data to conditions in humans need to be considered. Received: 5 October 2000, Returned for 1. revision: 2 November 2000, 1. Revision received: 24 November 2000, Returned for 2. revision: 28 November 2000, 2. Revision received: 13 December 2000, Accepted: 14 December 2000     

增龄及冠心病对运动的反应和心率变异性的影响

目的　研究 70岁以上冠心病及非冠心病老人心血管系统对运动负荷的反应 ,探讨其运动负荷特征与心率变异各能谱范围的关系。方法　经活动平板运动试验、动态心电图心率变异能谱分析、并行冠状动脉造影患者 2 16例。 70岁以上老人 96例为老年组 (Ⅰ组 ) ,70岁以下 12 0例为对照组 (Ⅱ组 ) ,两组各分两个亚组 ,冠心病患者分别为Ⅰa、Ⅱa组、非冠心病患者各为Ⅰb组、Ⅱb组。比较各组患者运动前后各生理指标的变化。结果　 (1)Ⅰ组运动峰值心率低于次极量心率 (极量心率 85 % )或 <12 0次 min者多于Ⅱ组 (Ⅰa组 35 .14 %vsⅡa组 15 .5 5 % ,P <0 .0 1,Ⅰb组 16 .95 %vsⅡb组 5 .33% ,P <0 .0 5 ) ;ⅠaⅠb组运动后 1min心率恢复值均 <12次 min ;心率变异高能谱范围呈现增龄性改变 (Ⅰa组vsⅡa组 ,P <0 .0 5 ;Ⅰb组vsⅡb组 ,P <0 .0 5 )。 (2 )Ⅰa组心肌缺血多发生于较低运动负荷时 [ST压低 1mm时的代谢当量 (METs)Ⅰa组 4 .4 8vsⅡa组 5 .4 8,P <0 .0 5 ];Ⅰa组心率变异各能谱范围多呈有意义降低 ,心率变时性损害Ⅰa组高于其他 3个组。结论　 (1)老年人尤其老年冠心病患者存在运动后心血管系统反应迟钝现象 ,心率变异高能谱范围呈现增龄性改变。 (2 )老年冠心病患者心率变异各能谱均有异常。 (3)老年冠心病患?     

Clinical Significance of Abnormal Heart Rate Recovery after Treadmill Exercise Test in Patients With Coronary Artery Disease

To evaluate the values of abnormal heart rate recovery （HRR） after treadmill exercise test in patients with coronary artery disease （CAD）. Methods One hundred and seventy-eight consecutive cases of suspected CAD who underwent symptom-limited treadmill exercise test （TET） and coronary angiography （CAG） were enrolled and divided into normal and abnormal HRR group based on the status of the values of HRR one or two minutes after TET. The clinical characteristics, TET parameters and CAG results of the two groups were compared attempted to assess the value of HRR on patients with CAD. Results （ 1 ） The cases of smoking, diabetes mellitus （DM） and ST segment deviation at rest in abnormal HRR group were more significantly than those in normal HRR group （ all P 〈 0. 05 ）. （2） The subjects of abnormal HRR usually had higher basal heart rate, more cases exhibited ST segment abnormality and or exercise-limited angina during or after TET（P 〈 0. 01 and P 〈 0. 05, respectively）, but lower level of peak heart rate attained （ P 〈 0. 05 ） than those in normal group. The values of metabolism equivalents and duration of TET between the two groups displayed phenomenal difference （ P 〈 0. 05 ）. There were more samples acquired moderate to high level of Duke test score and chronotropic incompetence in the group of abnormal HRR, compared to the normal HRR group （P 〈 0. 01 ）. （3） The cases of negative CAG results in the group of normal and abnormal HRR group were 73 （66. 97 % ） and 24 （34. 78 % ）. Cases of significant coronary lesions （ at least one major coronary vessel ≥ 50 % stenosis） amongst the subgroup of positive CAG were 36 （ 33.03 % ） and 45 （65.22 % ）, severe coronary lesions （ three-vessel, left main or the equivalents of left main） were 10 （9. 17 % ） and 17 （24. 64 % ） for normal and abnormal HRR respectively （P 〈 0. 01 ）. Accordingly, the Gensini scores in the subunit of abnormal HRR increased. （4）Linear correlation analysis indicate there was a negative correlation between the values of HRR in the first and second minutes and indices of severity of CAD （ all P 〈 0. 01 ）. The analysis of auxiliary diagnostic value of abnormal HRR indicated the annexed HRR standard had higher negative predictive value. Conclusions The status of HRR after TET are not only influenced by the clinical factors related to the cardiac autonomic function, but also associated with the extent of CAD. （ S Chin J Cardiol 2009 ; 10（1）：1-8）     

The role of apoptosis in myocardial ischemia: a critical appraisal

The role of apoptosis in cardiac ischemia is not clarified yet. Own data show that suicidal cell death is apparently not important in global ischemia where it only affects a small number of myocytes (8 %) while the majority of cells, i.e. 92 % die by oncosis. In acute regional ischemia it is most probably not a decisive factor. However, more solid data are needed to justify this statement. Human hibernating myocardium shows an activation of the apoptotic cascade, i.e., apoptosis might contribute to cell loss in this pathophysiological situation of multiple ischemic episodes. Manifold unresolved issues contribute to problems in determining the role of apoptosis in ischemia. These include 1) Uncertainty of the duration of the apoptotic cascade from activation of death receptors at the cellular membrane until DNA fragmentation occurs, 2) The role of the mitochondrial pathway, 3) The mode of removal of myocytes after cell death has occurred, 4) Technical problems such as specificity of the TUNEL method, detection of low abundance proteins such as activated caspases or cytochrome C, statistical considerations. These issues and many others should be clarified before any definite conclusion as to the role of apoptosis in ischemia may be drawn. Received: 22 January 2001, Returned for revision: 22 January 2001, Revision received: 23 January 2001, Accepted: 23 January 2001     

急性心肌梗死患者连续心率减速力的临床研究

目的探讨急性心肌梗死患者的连续心率减速力（heart rate deceleration runs,DRs）危险分层与心率减速力（deceleration capacity,DC）、心率变异性总标准差（SDNN）、左室射血分数（left ventricular ejection fraction,LVEF）以及冠状动脉狭窄程度之间的关系。方法38例急性心肌梗死患者和20例体检者接受24 h动态心电图和超声心动图检查,测定其DC值、DRs、HRV时域指标SDNN以及LVEF;对急性心肌梗死患者进行冠状动脉造影,记录冠脉狭窄程度。按照DRs结果分为低危组（17例）、中危组（15例）、高危组（6例）、对照组（20例）,比较4组间年龄、DC值、SDNN、LVEF及冠脉狭窄程度。结果①高危组的年龄比低危组明显增大,差异有统计学意义（P〈0.05）;②从对照组到高危组,DC值和SDNN值逐渐降低,高危组与其他3组相比明显降低,其差异有统计学意义（P〈0.05）;③DRs分层与冠脉狭窄程度无明显相关性。结论急性心肌梗死患者DRs分层和DC值、SDNN间有显著相关性,均能评估急性心肌梗死患者迷走神经张力,联合应用可提高心肌梗死后猝死的预警。     

Poor responsiveness of heart rate to treadmill exercise in vasospastic angina

Heart rate response to submaximal graded treadmill exercise was measured in 45 patients with vasospastic angina, 31 with effort angina, and 40 normal controls. There was no difference of resting heart rate among the three groups. Vasospastic angina showed significantly poor responsiveness of heart rate to exercise at every stage: stage 1, 2.5 km/h (10%), stage 3, 4.5 km/h (10%), stage 5, 5.5 km/h (14%), stage 7, 5.5 km/h (22%), when compared with those in normal controls. The effort angina group also showed lower heart rates at stages 3 and 5 than those in control subjects, although their heart rate at stage 1 was not different from that in normals. When abnormal response suggesting vasospastic angina was defined as heart rate at each stage lower than values of mean heart rate +/- 1 SD in normal controls, positive test results were obtained in 15 of 45 patients (33%). The use of heart rate criteria in addition to ischemic criteria raises sensitivity from 27 to 51% (p less than 0.02).     

Ischemia monitoring with on-line vectorcardiography compared with results from a predischarge exercise test in patients with acute ischemic heart disease

Information from 24-hour monitoring with on-line vectorcardiography, starting immediately after admission, was compared with results from a predischarge exercise test 3–13 days after admission. A total of 169 patients with acute myocardial infarction and 73 patients with unstable angina pectoris were investigated. Patients were followed for 487 ± 135 days. During the follow-up period, 19 patients (8%) died from cardiac causes and 34 (14%) were hospitalized for a myocardial infarction. The QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM), ST vector magnitude (ST-VM), and ST vector leads X, Y, Z were monitored. Patients with ST depression on the exercise test showed higher occurrence of transient, supposedly ischemic, episodes of QRS-VD, STC-VM, and ST-VM than patients without ST depression. The sensitivity and specificity of identifying patients with ST depression at the exercise test were respectively, 71 and 47% for QRS-VD episodes, 58 and 56% for ST-VM episodes, and 55 and 65% for STC-VM episodes. The maximum ST depression at the exercise test was related to the maximum ST depression in vector lead X (r = .44, P < .001) and the number of STC-VM (r = .40, P < .001), ST-VM (r = .37, P < .001), and QRS-VD (r = .33, P < .001) episodes on the VCG. In multivariate analysis, maximum ST depression in vector lead X and STC-VM episodes were the best determinants for ST depression at the exercise test. In a Cox regression model, the optimal combination of exercise test data in patients who died from cardiac causes exhibited a global chi-square value of 20.0. The combination of these data and the number of STC-VM episodes increased the global chi-square value to 30.6. This study indicates that in patients with acute ischemic heart disease, early continuous vectorcardiographic monitoring may predict the results from a predischarge exercise test and also contributes independent prognostic information beyond that of exercise test data.     

冠心病心电图心肌缺血与心率变异性的关系

为通过了解心肌缺血时心率变异性的改变，探讨冠心病自主神经失衡的状况，前瞻，顺序地观察静息心电图呈典型心肌缺血的冠心病患者２１例，心电图正常的冠心病患者１９例和健康人２２例ＨＲＶ时域，频域指标。     

Establishment of a long-surviving murine model of myocardial infarction: Qualitative and quantitative conventional microscopic findings during pathological evolution

Summary Ongoing basic molecular analyses are being performed in mice, and a simple long-surviving murine model of myocardial infarction (MI) would be very useful in this regard. Although a few studies have included MI in mice by coronary artery ligation, the induction involves a complex technique and has a relatively high mortality rate. In addition, the identification of the basic pathological sequence is essential to the interpretation of experimental results. We developed a simple technique for the induction of MI in mice and examined qualitative and quantitative conventional microscopic findings during the pathological evolution over a 28-day observation period. Male BALB/c mice weighing approximately 25 – 30 g were anesthetized and then ventilated with a positive pressure ventilator. The heart was exposed by thoracotomy. Left coronary artery occlusion was performed by thermocoagulation using a thermocoagulation knife at the level of the tip of the left atrium. After establishing this surgical method, we used it to induce MI in 71 mice. The operative and postoperative mortality rates of this model were 5.6 % (4/71) and 12.6 % (9/71), respectively. In 3 (5.2%) of the 58 surviving mice, the area of infarct was not sufficient. The infarct area in the remaining 55 mice was 40 ± 9 % of the entire perimeter of the left ventricle. Conventional microscopic examinations with hematoxylin-eosin and Masson-trichrome staining disclosed that all of the characteristic histopathological features of MI occurred 1 – 2 days earlier than those in rats. Our surgical technique provides a sufficient infarct area, with an acceptable mortality rate. The present study clarified the histopathological sequence in this long surviving murine MI model. Received: 2 July 1998, Returned for revision: 19 August 1998, Revision received: 7 October 1998, Accepted: 7 October 1998     

运动试验变时性与冠心病相关性的研究

目的以运动试验中实达心率与年龄预测心率的比值作为变时性的一项指标,探讨其对冠心病的诊断价值。方法104例临床疑诊冠心病患者行冠脉造影、平板运动试验,得出冠心病组、对照组运动试验中变时性功能指标参考值,根据数据绘制受试者工作特性(ROC)曲线,采用配对ROC曲线下面积Z检验研究运动试验中变时性指标对冠心病的诊断效能。结果①冠心病组、对照组变时性指标有显著性差异(p<0.001);②变时性指标诊断冠心病的敏感性为63.8%,特异性为71.9%;③与传统ST段对冠心病的诊断效能相比无显著性差异(p>0.05);④将两种指标进行序列试验可以提高诊断准确率,序列试验联合特异性为86.0%,平行试验联合敏感性为87.2%。结论变时性功能可作为判断冠心病的指标,与传统的ST段指标联合应用可提高冠心病的检出率。     

急性心肌梗死恢复期运动试验的价值

29例急性心肌梗死患者恢复期(31—81天)接受症状限制性平板运动试验。23例接受冠脉造影,22例接受左室造影。运动中ST段压低诊断多支病变的敏感性和特异性为60％与92％。低运动负荷结合运动中ST段压低诊断多支病变的敏感性和特异性为100％与67％;运动中收缩压反应异常结合ST段压低诊断多支病变的敏感性和特异性为80％与92％。广泛前壁梗死运动中ST段抬高者显著多于其他部位梗死。10例运动中ST段抬高者6例有室壁瘤形成。运动试验指标与超声心动图测得的左室射血分数无相关性。     

Alcohol and the risk of myocardial infarction

Epidemiological studies have repeatedly demonstrated a beneficial effect of moderate alcohol consumption on the incidence of coronary heart disease, myocardial infarction and overall mortality. The latter increases with excessive alcohol consumption. Although most epidemiological studies demonstrate a beneficial effect of alcohol consumption independent from the specific kind of alcoholic beverage, there is increasing evidence that wine and in particular red wine might contain pharmacological substances, which prevent atherosclerosis and myocardial infarction independent from the wine ethanol. Pathophysiological mechanisms mediating these beneficial effects include effects of wine phenols and tannins on LDL-cholesterol oxidation status, thrombocyte aggregation, endothelial function and smooth muscle cell proliferation. Identification and characterization of the pharmacologically active substances might provide the stage for the development of new substances to be used in the prevention of coronary artery disease and myocardial infarction. Received: 14 August 2000, Returned for 1. revision: 6 September 2000, 1. Revision received: 23 November 2000, Returned for 2. revision: 5 December 2000, 2. Revision received: 21 December 2000, Accepted: 8 January 2001     

影响平板运动试验心率恢复的相关因素分析

目的探讨影响平板运动试验(treadmill exercisetest,TET)后心率恢复的相关因素。方法回顾性分析2008年5月～2012年5月在我院做TET并经冠状动脉造影(coronary angiography,CAG)确诊或排除冠心病的150份病例。根据TET中是否发生心率恢复异常(运动后第1分钟心率恢复<18次/min)分为心率恢复异常组(A组)及心率恢复正常组(B组),并收集各项临床观察指标进行分析。结果男性、体质量超重、吸烟、基础心率偏快、伴随冠心病(尤其是多支病变者)、伴随糖尿病及焦虑症者均可影响运动后的心率恢复。结论控制体质量、戒烟、降低过快的基础心率、重视精神障碍的心理干预、重视糖尿病者的自主神经功能检测、加强冠心病者的双心治疗对心血管疾病的防控具有重要的临床意义。     

运动试验阳性的女性患者冠脉造影结果分析

目的探讨平板运动试验对女性冠心病的诊断价值。方法对77例平板运动试验阳性的女性患者行冠状动脉造影检查，对结果进行回顾性分析。结果冠状动脉造影阳性48例（62．33％），阴性29例（37．67％）。阳性患者中单支病变10例，双支病变25例，多支病变13例。有胸痛症状者45例，冠状动脉造影阳性40例；无明显症状者32例，冠状动脉造影阳性8例。结论女性平板运动试验结果中，无临床症状者假阳性较多，有危险因素和临床症状者，平板运动试验阳性与冠状动脉造影阳性结果的符合率较高。