Electrical current paths in acute pericarditis

The electrocardiographic changes accompanying pericarditis consist of ST elevation in most of the leads of the 12-lead electrocardiogram. The source of this ST elevation is thought to be local inflammatory changes in the epicardium underlying the inflamed pericardium. The current from this area of ST elevation must return to some unaffected region of the heart and this should be associated with a region of ST depression. This current path from the external epicardial surface has been postulated to flow back into the endocardium through the great vessels and atria. To test this hypothesis, 18 patients with pericarditis were studied by body surface potential mapping and inverse epicardial potential distributions were computed. The resultant maps were compared to those of normal people and patients with acute anterior infraction. Epicardial maps from patients with pericarditis showed a region of current flow into the heart over the great vessels and atria in all 18 patients. This pattern was not seen in normal patients or infarction patients and was consistent with the mechanism resulting in ST elevation in pericarditis being one of current flowing from the epicardium out into the thorax and black into the heart through the great vessels and atria.     

Epicardial ST depression in acute myocardial infarction

The presence of electrocardiographic ST depression in acute infarction remains controversial and poorly explained. A combined animal and modeling study was performed to evaluate the source of ST changes in acute infarction. In anaesthetized sheep, small infarcts showed uniform ST elevation over the infarction whereas larger infarcts showed marked ST depression over the normal myocardium in addition to the ST elevation. These findings were replicated by bidomain models of the heart. A hollow sphere was used to model a gradually increasing infarct, and this showed that there was a decrease in the ratio of ST elevation to ST depression as the infarct was increased. The current flowing out of the heart must be identical to the current flowing back into the heart. This means that any infarction will produce ST depression as well as ST elevation, the ratio between the two being related to the size of the infarction. Small infarction is associated with a small region of ST elevation and minor ST depression of the remaining myocardium, and as the infarct region increases, the amplitude of the epicardial ST elevation falls and the amplitude of the ST depression increases. Infarction size is proportional to both the height of the ST depression on the epicardium and the strength of the epicardial ST segment dipole.     

Derived epicardial potentials differentiate ischemic ST depression from ST depression secondary to ST elevation in acute inferior myocardial infarction in humans

It was hypothesized that in acute inferior wall myocardial infarction, an additional ischemic area in the subendocardium of the noninfarcting territory would produce a selective current dipole between the infarcting and ischemic regions. A resistance network model to calculate epicardial potentials from body surface electrocardiographic potentials was developed and used to examine the hypothesis in 219 patients with acute inferior myocardial infarction. In the learning set of 110 patients, two characteristic dipole patterns were observed, each associated with a high mortality rate in the ensuing 15 months when compared with that in the remaining patients. In the test set of 109 patients, a double-blind analysis of the patterns showed that the 34 patients with a dipole pattern had a collective mortality rate of 35% at 15 months compared with a 15 month rate of 5% in the remaining patients. In the total group of 219 patients, the magnitude of ST segment elevation and both the magnitude and integral of the area voltage of ST depression on the epicardium were significantly correlated with the mortality rate (p less than 0.0002 for all variables against death at 15 months). This study strongly suggests that ST depression due to ischemia can be differentiated from ST depression secondary to the ST elevation in acute inferior infarction by the examination of epicardial potential distributions.     

A validation of derived epicardial potential distributions by prediction of the coronary artery involved in acute myocardial infarction in humans

We have developed computer algorithms that enable epicardial potential distributions to be calculated from electrocardiographic body surface data. To validate this inverse transformation we obtained body surface maps during the ST segment in 55 patients with acute infarction who subsequently underwent coronary arteriography and we constructed epicardial ST segment potential distributions for each patient. From the unlabeled epicardial maps one of us predicted the coronary artery that would be found to be involved in the infarction. These predictions were compared with the results of coronary arteriography and this showed that the analysis of the epicardial map correctly predicted the coronary artery involved in 40 of 55 patients (72.7%). In another eight patients the anatomy was partially predicted. In the 15 patients in whom the prediction was incorrect or partially correct (27.3%), 11 had critical disease or occlusions of the predicted coronary artery but the infarct-related artery was incorrectly identified. This verifies that sensible epicardial potential maps can be calculated from body surface electrocardiographic data, and that these data are sufficiently accurate to predict the vessel involved in acute infarction.     

Prognostic value of predischarge 12 lead electrocardiogram after myocardial infarction compared with other routine clinical variables

The prognostic value of QRS score (Selvester), ST depression, ST elevation, extrasystoles, P terminal force in V1, and QTc derived from the predischarge 12 lead electrocardiogram was assessed after myocardial infarction in 474 patients without intraventricular conduction defects, ventricular hypertrophy, or atrial fibrillation. The usefulness of these results in risk assessment was compared with that of other clinical data. During follow up 45 patients died. Logistic regression analysis showed that QRS score, ST depression, and QTc were independently predictive of cardiac mortality. When multivariate analysis was applied to clinical and electrocardiographic data together, however, the 12 lead electrocardiogram did not provide independent information additional to that provided by other routine clinical findings and laboratory tests such as a history of previous myocardial infarction, clinical signs of persistent heart failure, indication for digitalis or antiarrhythmic drugs at discharge, and enlarged heart on chest x ray. In conclusion, the electrocardiogram has important prognostic value; however, it is not powerful enough to further improve the risk assessment of post-infarction patients.     

Prognostic value of predischarge 12 lead electrocardiogram after myocardial infarction compared with other routine clinical variables.

The prognostic value of QRS score (Selvester), ST depression, ST elevation, extrasystoles, P terminal force in V1, and QTc derived from the predischarge 12 lead electrocardiogram was assessed after myocardial infarction in 474 patients without intraventricular conduction defects, ventricular hypertrophy, or atrial fibrillation. The usefulness of these results in risk assessment was compared with that of other clinical data. During follow up 45 patients died. Logistic regression analysis showed that QRS score, ST depression, and QTc were independently predictive of cardiac mortality. When multivariate analysis was applied to clinical and electrocardiographic data together, however, the 12 lead electrocardiogram did not provide independent information additional to that provided by other routine clinical findings and laboratory tests such as a history of previous myocardial infarction, clinical signs of persistent heart failure, indication for digitalis or antiarrhythmic drugs at discharge, and enlarged heart on chest x ray. In conclusion, the electrocardiogram has important prognostic value; however, it is not powerful enough to further improve the risk assessment of post-infarction patients.     

A clinical study of postinfarction angina (PIA): the significance of electrocardiographic ST segment changes during anginal attacks]

We studied the clinical significance of electrocardiographic ST segment changes during PIA attacks. Of 478 AMI patients admitted to the CCU of our hospital within 48 hours after onset, we evaluated 73 (15.3%) with PIA. According to electrocardiographic ST segment changes during PIA attacks, the patients were divided into three groups, namely ST elevation at the same infarction site (same site elevation group), ST depression at the same site (same site depression group), and ST depression at other sites (other site depression group), and their pathological condition was studied. There were 33 patients (45.2%) in the same site elevation group, 19 (26.0%) in the same site depression group, and 21 (28.8%) in the other site depression group. The predominant infarction areas were anteroseptal and inferior wall in the same site elevation group, NTMI in the same site depression group, and inferior wall in the other site depression group. PIA usually occurred within 4 days after the onset of infarction in the same site elevation group, and within 5-7 days in the other site depression group, but no uniform trend was observed in the same site depression group. With respect to the number of vessels showing disease, cases of single-vessel disease tended to predominate in the same site elevation group, while cases of three-vessel disease tended to predominate in the same site depression group and the other site depression group. Stenosis rates in the vessels responsible for infarction were high in the same site elevation group in the acute period. Prognoses were poorest in the same site depression group.(ABSTRACT TRUNCATED AT 250 WORDS)     

93例急性心肌梗死患者的心电图及冠脉造影分析

目的探讨急性心肌梗死患者心电图sT改变的导联与冠状动脉罪犯血管的关系。方法对93例急性心肌梗死患者心电图ST段改变与选择性冠状动脉造影结果进行对比分析。结果心电图V1-V4sT抬高伴Ⅱ、Ⅲ、aVFST段下移的罪犯血管主要为左前降支（LAD）,少数前壁心肌梗死伴下壁sT段抬高;Ⅱ、Ⅲ、aVFST抬高伴V1-V4 ST段下移的主要罪犯血管为右冠状动脉（RCA）,少部分为左回旋支（LCX）,极少部分为LAD;胸前导联T高尖与ST抬高导联不一致可排除LAD;高侧壁Ⅰ、AVLST段抬高多数罪犯血管为LCX。结论心电图ST改变的导联对急性心肌梗死罪犯血管能进行初步预测。     

The relationship of ST elevation to eventual QRS loss in acute inferior myocardial infarction

The electrocardiographic changes of ST-segment elevation in acute myocardial infarction are related to the region of infarction. The authors examined body surface map data in 70 patients with acute inferior infarction to determine the exact relationship of the initial ST elevation to the eventual loss of QRS. The patients had no evidence of previous myocardial infarction and no subsequent infarction and did not receive thrombolytic therapy or other acute interventions, such as surgery. Maps were recorded on admission to the hospital, during the hospital admission and again at follow-up examination 6-48 months after infarction. The region of ST elevation of the initial body surface map was compared to a QRS loss region derived by subtracting the follow-up map, integrated over the 80 msec after the onset of the QRS, from a "QRS loss region" derived from 381 normal patients using the same interval. In 76% of patients there was a direct relationship between the position of the ST elevation and the QRS loss region (mean correlation coefficient, 0.49). In a further 15% of patients there was a general relationship without specific features, and in the remaining 8% the difference maps were not related to the position of ST elevation. The region of ST elevation predicts the eventual QRS loss in the majority of patients and may be useful for monitoring interventions in acute myocardial infarction.     

Mechanisms of ST change in partial thickness ischemia

The origin of ST depression in ischemia remains poorly understood. The accepted source is of intracellular current flowing between the ischemic and non ischaemic muscle both in systole and diastole such that the AC recorded electrocardiogram shows ST elevation over the ischemic area. The difficulty comes with partial thickness ischemia where the body surface changes do not allow localisation of the ischemic region. In an animal model we have shown that the reason one cannot see the region on the body surface is that the epicardial distribution of ST segment is almost identical for partial thickness ischaemia in the left anterior descending coronary artery, (LAD) and circumflex coronary artery (Cx) territories. Dissection of the reasons for this finding has lead to 3 contributing factors. The first is the role of the right ventricular blood mass, the second the boundary between ischemia and normal and the third the presence of anisotropy and its contribution. In a block of myocardium with anisotropy included we have shown marked differences between the distributions depending on the anisotropy. We have also shown that the published values of conductivity for use in the bidomain model produce unacceptably disparate results.     

ST segment depression in aVL: a sensitive marker for acute inferior myocardial infarction

In a substantial percentage of patients with acute myocardialinfarction, especially in those with inferior wall involvement,no ST elevation is detected on the electrocardiogram. In manyof them, ST depression is found in leads oriented to remotesegments of the heart. The importance of those reciprocal changesfor early diagnosis of acute inferior myocardial infarctionin patients without ST elevation has not been stressed. In orderto find the prevalence of reciprocal ST depression, we evaluatedthe admission electrocardiograms of 107 consecutive patientswith evolving first acute inferior mvocardial infarction. Ninety-threepatients had ST elevation of at least 0.1 mV in at least oneof the inferior leads: II, III or a VF (group A) and in 14 patientsST displacement did not reach 0·1 mV in any of theseleads (group B). In both groups, reciprocal ST depression occurredmore frequently in a VL than in any other lead. Only three patientshad no ST depression in a VL. in eight patients (7·5%ST depression in a VL was the sole early electrocardiographicsign of the inferior infarction, a VL is the only lead thatis facing the superior part of the left ventricle and thus isthe only lead that is truly opponent to the inferior wall. Itseems that ST depression in a VL, by contrast to that in theprecordial leads, is found in the majority of patients withevolving inferior wall myocardial infarction and is not influencedby extension of the infarclion to the right ventricle or tothe posterior wall. We conclude that transient ST depressionin a VL is a sensitive early electrocardiographic sign of acuteinferior wall myocardial infarction.     

Value of the bipolar lead CM5 in electrocardiography

Only bipolar lead recording are available during ambulatory monitoring. Their sensitivity in detecting ST segment changes in relation to standard electrocardiographic leads is not known. The magnitude and direction of ST segment changes in the bipolar lead CM5 were compared with those in standard electrocardiographic leads in patients during exercise testing and percutaneous transluminal coronary angioplasty. Thirty patients with coronary artery disease were studied during exercise tests in which ST segment depression (greater than 0.5 mm) occurred in one or more standard electrocardiographic leads and 13 patients were studied during angioplasty that resulted in ST segment change in one or more leads (I, II, III, V2, V5, and CM5). Lead CM5 was the most sensitive lead (93%) during exercise testing and also showed the greatest magnitude of ST segment change below the isoelectric line in 93% of the patients. Only two patients, one with ST segment elevation in inferior leads and one with changes restricted to septal leads, had no ST segment depression in lead CM5. When ST segment shift from the baseline electrocardiogram was measured the magnitude of depression was greatest in lead CM5 in only 63% of the patients. During angioplasty of the left anterior descending coronary artery, lead CM5 showed ST segment depression in seven patients, ST segment elevation in two, and a biphasic response in one. Two of the three patients with balloon inflation in right coronary artery developed ST segment elevation in lead CM5. Thus lead CM5 is a reliable lead for detecting subendocardial ischaemia experienced during everyday activities in anginal patients. During total occlusion of coronary arteries (as in variant angina or myocardial infarction) lead CM5 commonly shows ST segment depression and changes due to right coronary artery occlusion may not be detected.     

Value of the bipolar lead CM5 in electrocardiography.

Only bipolar lead recording are available during ambulatory monitoring. Their sensitivity in detecting ST segment changes in relation to standard electrocardiographic leads is not known. The magnitude and direction of ST segment changes in the bipolar lead CM5 were compared with those in standard electrocardiographic leads in patients during exercise testing and percutaneous transluminal coronary angioplasty. Thirty patients with coronary artery disease were studied during exercise tests in which ST segment depression (greater than 0.5 mm) occurred in one or more standard electrocardiographic leads and 13 patients were studied during angioplasty that resulted in ST segment change in one or more leads (I, II, III, V2, V5, and CM5). Lead CM5 was the most sensitive lead (93%) during exercise testing and also showed the greatest magnitude of ST segment change below the isoelectric line in 93% of the patients. Only two patients, one with ST segment elevation in inferior leads and one with changes restricted to septal leads, had no ST segment depression in lead CM5. When ST segment shift from the baseline electrocardiogram was measured the magnitude of depression was greatest in lead CM5 in only 63% of the patients. During angioplasty of the left anterior descending coronary artery, lead CM5 showed ST segment depression in seven patients, ST segment elevation in two, and a biphasic response in one. Two of the three patients with balloon inflation in right coronary artery developed ST segment elevation in lead CM5. Thus lead CM5 is a reliable lead for detecting subendocardial ischaemia experienced during everyday activities in anginal patients. During total occlusion of coronary arteries (as in variant angina or myocardial infarction) lead CM5 commonly shows ST segment depression and changes due to right coronary artery occlusion may not be detected.     

ST Segment Elevation in One Lead: A Case Report

Background: We describe an unusual finding in an electrocardiogram showing ST‐segment elevation not related to coronary artery stenosis, pericarditis, bundle branch block, or other well known disorders. Case Presentation: A 60‐year‐old African American woman admitted for elective coronary artery bypass graft surgery. A temporary pacemaker with pacing wires was placed intraoperatively for prevention and treatment of postoperative bradyarrhythmia. One day following uneventful surgery, her electrocardiogram demonstrated marked ST segment elevation confined to lead V₆. These changes were comparable to tracings obtained from direct epicardial electrocardiogram, due to contact between the V₆ electrode and the temporary pacemaker ventricular lead wire. Conclusion: Current‐of‐injury patterns are represented on surface electrocardiogram by deviations of the ST segment from the isoelectric baseline. The pacing wire causes direct localized epicardial current‐of‐injury, affecting the action potential and the resting membrane potentials of cardiomyocytes. Our case report demonstrates epicardial current‐of‐injury pattern obtained via surface rather than epicardial electrocardiogram, with surface leads as surrogates of epicardial tracing. Measurement of ST‐segment shifts from the epicardial electrocardiogram has been shown to provide a more sensitive measurement of ischemia when compared to surface precordial ECG.     

Precordial and epicardial surface potentials during Myocardial ischemia in the pig. A theoretical and experimental analysis of the TQ and ST segments.

The solid angle theorem was used to analyze the relationships between TQ and ST segment deflections recorded from precordial and epicardial locations and the time course, size, shape, and transmural location of the ischemic process in the ventricular myocardium. Mathematical predictions were compared with experimental data from the intact heart. Precordial electrograms obtained in anesthetized close-chest pigs were compared with epicardial electrograms recorded directly from the heart's surface. Various areas of ischemia were produced by occluding large and small coronary artery branches, and the resultant changes in ischemic shape were delineated with Thioflavin S injections and postmortem ultraviolet photography. Formally derived equations and cumulative experimental data were in close agreement, suggesting that in the ischemic ventricle (1) TQ depression always accompanies ST elevation, (2) TQ and ST segment changes in magnitude and polarity are complex functions of ischemic size, shape, and transmural location; (3) precordial electrocardiogram (ECG) ST segment elevation is directly related to ischemic size; and (4) epicardial ECG ST segment elevation is inversely related to ischemic size. It is thus concluded that precordial and epicardial ECG TQ and ST segment deflections are complex functions of ischemic geometry and that their accurate interpretation with respect to ischemic size and shape and in the presence of pharmacological interventions is often difficult and may be misleading.     

急性下壁心肌梗死心电图胸前导联V1-3 ST段抬高的临床意义

目的 探讨急性下壁心肌梗死患者心电图胸前导联ST段抬高与冠状动脉造影所示冠状动脉病变的关系及其临床意义.方法 187例急性下壁心肌梗死患者,按入院时18导心电图胸前导联ST段改变分为2组,ST段抬高组（16例）和非ST段压低组（171例）.所有患者均行冠状动脉造影术,病变适合行经皮腔冠状动脉成型术并检测B型钠尿肽（BNP）.结果 急性下壁心肌梗死伴胸前导联ST段抬高时多为右冠状动脉近段闭塞,尤其是圆锥支闭塞（P＜0.01）,且伴有右心功能不全和血流动力学障碍,与下壁右室心梗相比BNP差异有统计学意义（P＜0.01）.结论 急性下壁心肌梗死合并胸前导联ST抬高表明为右冠状动脉近段或开口闭塞且多伴右室心肌梗死和心功能不全.     

Surface electrocardiogram in the detection of transmural myocardial ischemia during coronary artery occlusion

To examine whether coronary occlusion causing transmural ischemia was accurately reflected by ST-segment elevation on routine electrocardiograms, intracoronary and surface electrocardiograms were simultaneously recorded during percutaneous transluminal coronary angioplasty (PTCA). The study group consisted of 54 patients who had intracoronary ST-segment elevation during transient coronary occlusion (left anterior descending [LAD]: 25 patients, left circumflex [LC]: 19 patients, right coronary artery: 12 patients). Elevation of the ST segment on the surface electrocardiogram (greater than or equal to 0.1 mV) was recorded in 84% of patients during LAD dilatation, in 32% of patients during LC dilatation (p less than 0.01 vs LAD and right), and in 92% of patients during right coronary dilatation (not significant vs LAD). The magnitude of intracoronary ST elevation was 1.10 +/- 0.8, 1.68 +/- 1.2 and 0.8 +/- 0.6 mV for the LAD, LC and right occlusions, respectively (not significant). Thus, despite the comparable magnitude of intracoronary ST elevation, LC occlusion resulted in ST-segment elevation on the surface electrocardiogram in significantly fewer patients than did LAD or right occlusion. During LC occlusion, 9 patients had no electrocardiographic changes and 4 had only precordial ST depression. Thus, in patients with transmural ischemia during right or LAD occlusions, concordant ST elevation on the surface electrocardiogram is common. In contrast, ST-segment elevation is an insensitive marker of LC occlusion. In patients with ongoing ischemic symptoms and isolated precordial ST depression or no repolarization abnormalities, LC occlusion should be considered in the differential diagnosis.     

36例回旋支为梗死相关动脉的急性下壁心肌梗死的心电图特点

目的分析回旋支为梗死相关动脉的急性下壁心肌梗死(简称心梗)的心电图表现,总结其心电图特点。方法回顾性分析本院经冠状动脉造影证实回旋支为梗死相关动脉的急性下壁心梗患者36例,分为ST↑Ⅲ<Ⅱ组(n=8),ST↑Ⅲ=Ⅱ组(n=19)和ST↑Ⅲ>Ⅱ组(n=9)三组,分析发病12 h内的18导联心电图特点。比较三组冠状动脉优势型及病变部位。结果 ST↑Ⅲ<Ⅱ组STⅠ、aVL抬高、等电位线、压低的发生率分别为50%,12.5%,37.5%;ST↑Ⅲ=Ⅱ组相应的发生率分别为10.5%,31.6%,57.9%;ST↑Ⅲ>Ⅱ组相应的发生率分别为0,11.1%,88.9%。ST↑Ⅲ<Ⅱ组STV4-6抬高、等电位线、压低的发生率分别为87.5%,0,12.5%;ST↑Ⅲ=Ⅱ组相应的发生率分别为78.9%,21.1%,0;ST↑Ⅲ>Ⅱ组相应的发生率分别为66.7%,0,33.3%。三组患者冠状动脉优势型的比较有差异(P<0.05),三组STV7-9形态、STV3R-5R形态、冠状动脉病变部位无差异(P均>0.05),三组均无房室传导阻滞的发生。结论回旋支为梗死相关动脉的急性下壁心梗ST↑Ⅲ<Ⅱ时常合并STⅠ、aVL抬高,ST↑Ⅲ=Ⅱ、ST↑Ⅲ>Ⅱ时常合并STⅠ、aVL压低;回旋支为梗死相关动脉的急性下壁心梗累及右室时也可表现为ST↑V3R-5R;回旋支为梗死相关动脉的急性下壁心梗不易发生房室传导阻滞。     

Spatial distribution and prognostic significance of ST segment potential determined by body surface mapping in patients with acute inferior myocardial infarction

We investigated the mechanism and significance of ST segment changes in inferior infarction by studying 100 patients with acute inferior infarction in whom body surface maps were recorded on admission. The magnitude of the maximum ST segment elevation (denoted Vmax) and magnitude of the maximum ST segment depression (denoted Vmin), as well as the ST depression on the standard 12-lead electrocardiogram were analyzed against morbidity and mortality (at a median follow-up time of 14 months). A value obtained by subtracting Vmax from Vmin correlated (p less than .0002) with outcome. Correlations were also found between Vmin and complications, Vmin and mortality, and between increasing levels of ST depression on the 12-lead electrocardiogram and mortality. The maps were also studied by grouping the 100 ST segment map patterns into five groups by cluster analysis techniques. One group showed marked anterior negativity and had 37% mortality compared with an overall 5% mortality for the remaining groups. The limited arteriographic and autopsy data available indicated that the findings of a diseased artery or arteries corresponded with the results of mapping. The mean map patterns of the five groups showed that, in most patients with inferior infarction, the standard chest leads V1 to V6 are over a region of steep voltage gradient. Small changes in the position of the standard chest lead can cause large changes in the displayed potentials. This study indicates that patients at high risk after acute inferior infarction can be identified by surface mapping on admission to the coronary care unit.     

Correlation of predischarge electrocardiographic patterns with left ventricular function in patients with anterior wall myocardial infarction

The aim of this prospective study was to assess the correlation between different predischarge electrocardiographic patterns and left ventricular function, evaluated by physical examination and echocardiography, in patients with first Q wave anterior acute myocardial infarction. A positive correlation was found between the electrocardiographic pattern and wall motion score assessed by echocardiography, reflecting a gradual worsening in left ventricular function among the different patterns. Patients with an isoelectric ST segment and negative T waves had a 73% decrease in the risk of clinical heart failure compared to those who continued to have ST elevation. Thus, a predischarge electrocardiogram can be used as a simple, noninvasive method for the risk stratification of patients with acute myocardial infarction.