Electrocardiographic differentiation between right coronary and left circumflex coronary arterial occlusion in isolated inferior wall myocardial infarction

The presence of atrioventricular block and ST segment elevation in lead V4R accurately predicts right coronary artery occlusion in patients with inferior wall myocardial infarction. However, these electrocardiographic signs are absent in the majority of patients with inferior myocardial infarction. We studied ST segment elevation in leads II and III, ST segment in lead I and T wave polarity in lead V4R in order to differentiate between right coronary artery and left circumflex coronary artery occlusions in 104 patients with inferior myocardial infarction who subsequently underwent coronary angiography. The ST segment elevation was greater in lead III than in lead II when the right coronary artery was the culprit vessel and vice versa when the left circumflex was the culprit vessel (p < 0.001). An upright T wave in lead V4R and ST segment depression in lead I was common when the right coronary artery was the culprit vessel and not seen with left circumflex occlusion (p < 0.001). ST segment elevation in lead III was higher than in lead II with a sensitivity of 99 percent and a specificity of 100 percent for diagnosing right coronary artery as the culprit vessel. ST segment elevation in lead II was higher than in lead III with a sensitivity of 93 percent and a specificity of 100 percent in identifying the left circumflex as the culprit vessel. Thus, these signs are very useful in identifying the culprit vessel in inferior myocardial infarction.     

Usefulness of ST elevation II/III ratio and ST deviation in lead I for identifying the culprit artery in inferior wall acute myocardial infarction

In a study of 92 patients presenting with inferior wall acute myocardial infarction, the infarct-related artery was the right coronary artery in 72 patients (78%) and the left circumflex artery in 20 (22%). An ST II/III ratio of 1 or an isoelectric ST in lead I are sensitive and specific markers of left circumflex artery occlusion, whereas an ST II/III ratio <1 (ST elevation in lead III >II) or ST depression in lead I are sensitive and specific markers of right coronary artery occlusion.     

常规心电图对前壁下壁心肌梗死罪犯血管的预测价值

目的:分析常规心电图对急性前壁下壁心肌梗死罪犯血管的预测价值。方法:选择41例急性前壁合并下壁ST段抬高的心肌梗死者作为研究对象,按冠脉造影资料将梗死罪犯血管分为右冠病变(RCA)组24例和左前降支病变(LAD)组17例,分别测量常规心电图12导联ST段偏移程度及发生的导联数,以计算比较两组间的差异及对不同冠脉之间的预测价值。结果:(1)两组的基线临床资料无显著差异性;(2)RCA组Ⅱ、Ⅲ、aVF导联ST段抬高幅度总和高于LAD组[(2.46±1.24)vs(1.77±0.61)mm,P0.01],ST段抬高III/II1(66%vs 28%,P0.01)或V1/V31(75%vs 12%,P0.05)在RCA组高于LAD组;LAD组V3导联ST段抬高幅度总和高于RCA组[(1.60±0.36)vs(4.44±2.65)mm,P0.01)。结论:Ⅱ、Ⅲ、aVF、V3导联ST段抬高幅度总和及V1/V3比值在诊断急性下壁前壁心肌梗死中对梗死罪犯血管有重要预测价值。     

Value of electrocardiographic algorithm based on "ups and downs" of ST in assessment of a culprit artery in evolving inferior wall acute myocardial infarction

Acute myocardial infarction (AMI) of the inferoposterior wall is due to occlusion of the right coronary artery (RCA) or the left circumflex (LCx) coronary artery. The outcome of patients depends mainly on the culprit artery. Therefore, the presumptive prediction of a culprit artery based on the electrocardiogram recorded at admission is of clinical importance. The aim of this study was to develop a sequential algorithm based on the "ups and downs" of the ST segment in different leads to predict the culprit artery (RCA vs LCx) in cases of inferoposterior AMI. We analyzed electrocardiographic and angiographic findings of 63 consecutive patients with an evolving AMI with ST elevation in the inferior leads (II, III, and aVF) and a single-vessel occlusion. Specificity, sensitivity, and positive and negative predictive values of different electrocardiographic criteria (ups and downs of the ST segment) were studied individually and in combination to find an algorithm that would best predict the culprit artery. The following electrocardiographic criteria were included in the 3-step algorithm: (1) ST changes in lead I, (2) the ratio of ST elevation in lead III to that in lead II, and (3) the ratio of the sum of ST depression in precordial leads to the sum of ST elevation in inferior leads [( summation operator downward arrow ST in leads V(1) to V(3))/( summation operator upward arrow ST in leads II, III, and aVF)]. Application of this sensitive algorithm suggested the location of the culprit coronary artery (RCA vs LCx) in 60 of 63 patients (>95%). The few patients in whom this algorithm did not work were those with a very dominant LCx that presented ST depression of > or =0.5 mm in lead I. In conclusion, careful sequential analysis of an electrocardiogram of an inferoposterior AMI with ST elevation may lead to the identification of a culprit artery.     

Role of myocardial ischemia and left ventricular wall motion abnormalities as contributory factors in the genesis of exercise-induced ST-segment elevation in Q-wave myocardial infarction.

In patients with a previous myocardial infarction, controversy exists regarding the significance of postexercise ST-segment elevation in the infarct-related leads. Although usually admitted to be a sign of left ventricular dysfunction or myocardial aneurysm, other studies however have related this finding to transient myocardial ischemia and to the presence of jeopardized but viable myocardium in the infarct area. The aim of the present study was to assess the significance of postexercise ST-segment elevation in Q-wave leads as a marker of transmural ischemia or left ventricular dysfunction in 36 consecutive patients, 16 with exercise-induced ST-segment elevation in infarct-related leads. Patients were evaluated by treadmill exercise testing, coronary angiography and ventriculography, thallium-201 tomographic scintigraphy and radionuclide ventriculography within 3 months of the first myocardial infarction. Sixteen patients (group I) had exercise-induced ST segment elevation and 20 (group II) postexercise inversion, no change or pseudonormalization of the T wave in infarct-related leads. The study showed no difference in infarct-related artery, vessel disease or luminal diameter stenosis in groups I and II. The overall agreement between ST shifts and myocardial perfusion in the infarct area was 30.56% with a kappa coefficient of -0.33 (p = NS). The overall agreement between ST shifts and wall motion abnormalities was 69.44% with a kappa coefficient of 0.39 (p < 0.01), stress-induced ST-segment elevation being associated with severe wall contractile disorders in 85% of the patients. In conclusion stress-induced ST-segment elevation in Q wave leads, although not a marker of wall motion abnormalities, is associated with akinesia or dyskinesia of the left ventricular wall.     

Detection of myocardial ischemia by analysis of the shape of exercise-induced ST elevation in infarct-related leads

OBJECTIVES: Possible mechanisms of exercise-induced ST elevation in infarct-related leads include ventricular dyskinesis, and myocardial ischemia in the infarct region. Detection of ischemia in viable myocardium in the infarct region is important to determine the therapeutic strategy. This study evaluated whether the analysis of the shape of exercise-induced ST elevation(convex or concave type) is useful to detect myocardial ischemia in the infarct region. METHODS: Ninety-eight patients (78 males, 20 females, mean age 59 +/- 10 years) with prior Q wave myocardial infarction underwent the treadmill exercise test. Patients were divided into three groups according to the exercise-induced ST changes: No ST-E group, 27 patients without ST changes; Concave ST-E group, 52 patients with concave type ST elevation; Convex ST-E group, 19 patients with convex type ST elevation. Coronary arteriography was evaluated in all patients. Dobutamine stress echocardiography was performed in 38 patients, including 28 patients in the Concave ST-E group and 10 patients in the Convex ST-E group. Biphasic or worsening response on dobutamine stress echocardiography was defined as ischemic response. RESULTS: Coronary arteriography revealed significant stenosis of the infarct-related artery in 30% of the No ST-E group, 47% in the Convex ST-E and 86% in the Concave ST-E groups (p < 0.05). Dobutamine stress echocardiography revealed myocardial ischemia in the infarct region in 30% in the Convex ST-E group and 75% in the Concave ST-E group(p < 0.05). CONCLUSIONS: The Concave ST-E group had a higher incidence of stenosis of the infarct-related artery and myocardial ischemia in the infarct region. Analysis of the shape of exercise-induced ST elevation in infarct-related leads is useful for the detection of ischemia of viable myocardium.     

活动平板运动试验诱发ST段抬高的临床意义

为探讨活动平板运动试验诱发ST段抬高的临床意义 ,分析了 9例无心肌梗死 (简称心梗 )而运动诱发ST段抬高的静息心电图、运动试验及冠状动脉 (简称冠脉 )造影检查结果。结果 :5 0 5 5例行平板运动试验者中 ,有 11例未患心肌梗死而运动诱发心绞痛伴ST段抬高 ,发生率 0 .2 2 %。其中 ,8例患者作了进一步检查 ,冠脉造影显示均有程度不等的血管病变 ,缺血相关血管的狭窄达到 5 0 %～ 10 0 %。ST段抬高导联与缺血相关血管有良好对应关系。另有 1例患者于运动试验 1周后死于心脏性猝死。结论 :无心梗患者运动诱发心电图ST段抬高是冠脉痉挛或冠脉严重狭窄所致心肌局部缺血的标志。     

平板运动试验诱发ST段抬高对冠状动脉病变部位定位诊断的意义

目的探讨平板运动试验诱发ST段抬高对冠心病的诊断价值及对冠状动脉病变部位定位诊断的意义。方法分析8例无心肌梗死而运动诱发ST段抬高的运动心电图及冠状动脉造影检查结果。结果8例患者冠脉造影均显示有程度不等的血管狭窄(50%￣100%);ST段抬高导联与缺血相关血管有良好对应关系。结论无心梗患者运动诱发心电图ST段抬高是冠脉痉挛或冠脉严重狭窄所致心肌局部缺血的标志,且对预测冠状动脉病变部位有一定意义。     

心电图改变对急性下壁心肌梗死相关血管的预测价值

目的:对急性下壁心肌梗死患者的心电图资料进行回顾性研究,分析和比较心电图改变与冠状动脉造影及临床特点的对应性关系。探讨体表心电图改变对急性下壁心肌梗死患者的临床价值。方法:选取86例急性下壁心肌梗死患者,根据冠状动脉造影结果分为右冠状动脉(RCA)病变组和左冠状动脉(LCA)病变组。对比分析其心电图改变与冠状动脉造影结果及临床特点。结果:Ⅰ、Ⅱ、Ⅲ、aVR导联ST段及aVL导联波形改变对诊断梗死相关血管具有重要价值;V3与Ⅲ导联ST段改变比值预测梗死相关血管部位具有重要价值;伴aVR导联ST段压低患者病情重;伴胸前导联ST段压低者病情重、并发症发生率明显增高。结论:心电图对诊断下壁急性心肌梗死相关血管及其临床特点具有重要的预测价值。     

急性前壁ST段抬高心肌梗死伴下壁导联ST段不同改变与冠状动脉病变的关系

目的:探讨急性前壁ST段抬高心肌梗死伴下壁导联ST段不同改变,与冠状动脉病变的关系以及对患者近期预后的影响。方法:回顾性分析308例急性前壁心肌梗死患者心电图表现,根据下壁导联心电图ST段变化分为两组:A组为Ⅱ、Ⅲ、aVF中至少2导联抬高;B组为Ⅱ、Ⅲ、aVF中至少2导联压低。比较两组之间心肌梗死面积,左心室重构指标,梗死相关动脉相关性以及近期预后。结果:与B组相比,A组CK-MB最大值较低[(111.46±64.65)vs.(179.79±96.06)IU/L,P<0.0l];左心室射血分数较高,为[(52.28±12.62)vs.(46.81±5.79)%,P<0.01];室壁运动分数低[(20.38±5.65)vs.(38.48±5.28),P<0.01]。两组梗死相关血管(infarct related artery,IRA)A组患者中30例(35.29%)为包绕心尖部前降支(wrapped left anterior descending artery,WLAD),55例(64.71%)为非包绕心尖部前降支(non-wrapped left anterior descending artery,NWLAD),B组患者中7例(3.14%)为WLAD,216例(96.86%)为NWLAD,两组梗死相关血管比较,差异有统计学意义(P<0.01)。下壁导联ST段抬高幅度较大,并伴有ST段抬高幅度V1>V3导联。室壁运动分数与左心室功能呈负相关;与心电图抬高导联数呈负相关,与Ⅱ、Ⅲ、aVF导联抬高幅度呈负相关;与sumSTE呈负相关;并与血浆尿素氮、LDL、TG及体质量呈负相关。主要心血管事件(major cardiovascular events,MACE)两组间差异无统计学意义。结论:IRA为左前降支(left anterior descending artery,LAD)的急性前壁ST段抬高心肌梗死时,下壁导联ST段改变可能与LAD长度和病变部位有关;前壁导联合并下壁导联ST段同时抬高的患者若IRA为WLAD,其梗死面积较小,心功能较好。     

A new application of the ST-HR loop to evaluate the exercise-induced reversible ischemia in healed anterior wall myocardial infarction

Exercise-induced ST-segment elevation in infarct-related leads is often seen on the treadmill exercise electrocardiogram of patients with anterior wall myocardial infarction. However, the cause of this phenomenon is still a matter of controversy. The purpose of this study was to evaluate the relation between the direction of ST-segment-heart rate (ST-HR) loop rotation and reversible myocardial ischemia in the infarct-related area. A total of 58 patients were enrolled in this study. They had healed anterior wall myocardial infarctions with single-vessel coronary artery disease and exercise-induced ST-segment elevations in the infarct-related leads, as observed on treadmill exercise electrocardiograms. All patients underwent treadmill exercise electrocardiography and dobutamine stress echocardiography at discharge. The direction of rotation of the ST-HR loop constructed from the treadmill exercise electrocardiogram and the dobutamine stress echocardiographic findings in the infarct-related area were compared. Counterclockwise rotation was seen in 26 of 58 patients. Compared with clockwise rotation, patients with counterclockwise rotation had significantly more viable myocardium (92% vs 69%, p = 0.04) and presence of reversible myocardial ischemia (58% vs 6%, p < 0.01). On the basis of the counterclockwise rotation findings, the diagnostic value of the presence of reversible myocardial ischemia was calculated. The sensitivity, specificity, and accuracy was 88%, 73%, and 77%, respectively. Counterclockwise rotation of ST-HR loops was strongly related to reversible myocardial ischemia in the infarct-related area. In conclusion, our results have shown that analysis of ST-HR loops may be useful in evaluating the cause of exercise-induced ST-segment elevation in infarct-related leads.     

The stretch-compression type of coronary artery movement predicts the location of culprit lesions responsible for ST-segment elevation myocardial infarctions

BACKGROUND: Prediction of the location of culprit lesions responsible for ST-segment elevation myocardial infarctions may allow for prevention of these events by safe and easily deliverable local therapies. METHODS: A retrospective analysis of coronary movement was performed on coronary angiograms of patients who subsequently represented with ST-segment elevation myocardial infarction treated by primary or rescue angioplasty at a single institution. RESULTS: Twenty patients were identified. The stretch-compression type of coronary artery movement (CAM) was a statistically significant independent predictor of the segment containing the culprit lesion (odds ratio 6.10, p-value 0.005). CONCLUSIONS: The stretch-compression type of coronary artery movement is an independent predictor of the location of culprit lesions responsible for ST-segment elevation myocardial infarctions.     

ST segment depression in lateral limb leads in inferior wall acute myocardial infarction: Implications regarding the culprit artery and the site of obstruction

We examined whether the pattern of ST segment depression inlateral leads (I, aVL, V5, V6) in the initial electrocardiogramof patients (n=88) with inferior wall acute myocardial infarction(ST segment elevation of 1 mm in 2 inferior leads) correlateswith the site of obstruction, as determined angiographicallyduring acute hospitalization. Of the 62 patients in which the culprit artery could be determinedunequivocally, in 46 the culprit artery was the right coronaryartery (20 proximal to the first right ventricular branch and26 distal), and in 16 the left circumflex coronary artery (sevenproximal to the first marginal branch or involving a high firstmarginal branch, and nine with distal obstruction). SignificantST segment depression (ST1 mm) in leads I and aVL was more commonin right coronary artery obstruction (P<0.05 and P<0.0001,respectively). The absence of significant ST segment depressionin lead a VL was most common in proximal circumflex obstruction(P<0.0001), with a similar trend for lead I (P<0.11).ST segment depression patterns in leads V₅ and V₆ were not indicativeof the infarct-related artery or the site of obstruction. Thus,significant ST segment depression in leads I and aVL indicatesright coronary artery-associated inferior wall acute myocardialinfarction with a sensitivity of 70% and 100%, and a specificityof 63% and 38%, respectively, whereas the lack of ST segmentdepression in these leads indicates proximal circumflex obstructionwith a sensitivity of 71% and 86%, and a specificity of 65%and 100%, respectively.     

Significance of treadmill stress testing in transmural myocardial infarction: Correlation with coronary angiography

To assess the usefulness of stress testing in predicting multivesselcoronary disease and left ventricular dysfunction, 83 male patientswith a myocardial infarction one to 84 months previously werestudied. In inferior infarction (45 patients), the ST segment depressionhad a sensitivity of 91% and a specificity of 77% to detectmultivessel disease. Patients with multivessel disease had significantlylower exercise capacity and maximal heart rates. ST segmentelevation showed a poor correlation with the number of affectedvessels. In anterior infarction (38 patients), both ST segment depressionand elevation were of little value to detect multivessel disease.However, the predictive value of an exercise test without STsegment changes to exclude multivessel disease was 89%; on theother hand, patients without ST segment changes had significantlyhigher ejection fractions, exercise capacity, maximal heartrates and rate-pressure products than patients with ST segmentchanges. Patients with ST segment elevation had significantly lower ejectionfractions in both groups. The sensitivity of ST segment elevationto detect severe segmental left ventricular dysfunction was84% for anterior infarction and 54% for inferior infarction.Specificity was 84 and 85%, respectively. We conclude that: (1) exercise-induced ST segment depression is useful to predictthe extent of coronary artery disease in inferior infarction,but it is of limited value in anterior infarction, (2) exercise-induced ST segment elevation correlates well withthe presence of severe left ventricular dysfunction in bothanterior and inferior infarction, and (3) an exercise test of considerable intensity without ST segmentchanges makes the existence of multivessel coronary diseaseand/or severe left ventricular dysfunction very improbable.     

Implications of ST-segment elevation in leads V5 and V6 in patients with reperfused inferior wall acute myocardial infarction

During inferior acute myocardial infarction, ST-segment elevation (ST↑) often occurs in leads V(5) to V(6), but its clinical implications remain unclear. We examined the admission electrocardiograms from 357 patients with a first inferior acute myocardial infarction who had Thrombolysis In Myocardial Infarction 3 flow of the right coronary artery or left circumflex artery within 6 hours after symptom onset. The patients were divided according to the presence (n = 76) or absence (n = 281) of ST↑ >2 mm in leads V(5) and V(6). Patients with ST↑ in leads V(5) and V(6) were subdivided into 2 groups according to the degree of ST↑ in leads III and V(6): ST↑ in lead III greater than in V(6) (n = 53) and ST↑ in lead III equal to or less than in V(6) (n = 23). The perfusion territory of the culprit artery was assessed using the angiographic distribution score, and a mega-artery was defined as a score of ≥0.7. ST↑ in leads V(5) and V(6) with ST↑ in lead III greater than in V(6) and ST↑ in leads V(5) and V(6) with ST↑ in lead III equal to or less than in V(6) were associated with mega-artery occlusion and impaired myocardial reperfusion, as defined by myocardial blush grade 0 to 1. Right coronary artery occlusion was most common (96%) in the former, and left circumflex artery occlusion was most common (96%) in the latter, especially proximal left circumflex occlusion (74%). Multivariate analysis showed that ST↑ in leads V(5) and V(6) with ST↑ in lead III greater than that in V(6) (odds ratio 4.81, p <0.001) and ST↑ in leads V(5) and V(6) with ST↑ in lead III equal or less than that in V(6) (odds ratio 5.96, p <0.001) were independent predictors of impaired myocardial reperfusion. In conclusion, ST↑ in leads V(5) and V(6) suggests a greater risk area and impaired myocardial reperfusion in patients with inferior acute myocardial infarction. Furthermore, comparing the degree of ST↑ in lead V(6) with that in lead III is useful for predicting the culprit artery.     

Determinants of exercise-induced ST-segment displacement in the aVL lead in patients with known or suspected coronary artery disease

Although the aVL lead in exercise electrocardiography is reported to be helpful in identifying a significant narrowing of the left anterior descending coronary artery (LAD), its role in exercise testing has not been fully evaluated. Accordingly, 821 patients who underwent both standard exercise testing and coronary angiography were evaluated. In patients with aVL lead ST elevation, the incidence of a significant narrowing of the LAD (124/165 vs 348/656; p<0.001) was higher than in those without. Multiple logistic regression analysis revealed that the 2 most important variables that correlated with aVL lead ST elevation were a greater number of leads with ST depression in the inferior leads and a smaller amplitude of R wave in the aVL lead. In contrast, variables correlating with aVL lead ST depression in the majority of cases were a greater number of leads with ST depression in all leads and the presence of inferior lead ST elevation. The results of this study indicate that although aVL lead ST elevation could be a marker for LAD narrowing, more important factors such as inferior lead ST-segment depression and the R-wave amplitude of the aVL lead should be taken into consideration. In contrast, ST depression in the aVL lead mostly represents exercise-induced myocardial ischemia of greater extent and severity.     

ST段抬高急性心肌梗死患者心电图对应导联ST段改变不同类型的临床预后

目的探讨ST段抬高急性心肌梗死（STEMI）患者心电图（ECG）对应导联ST段改变（R-ST-D）不同类型与罪犯冠状动脉病变及临床预后的关系。方法选择住院初发STEMI资料完整967例,根据R-ST-D振幅分4种类型,即R-ST-D振幅无下移（I组）143例;R-ST-D下移振幅小于或等于梗死区ST段抬高振幅（1I组）664例;R-ST-D下移振幅大于梗死区ST段抬高振幅（Ⅲ组）93例;R-ST-D和梗死区ST段均抬高（IV组）67例;分析其ECGR-ST-D4种类型与罪犯冠状动脉病变和临床高危预后的关系。结果R-ST-D4种类型中I组、Ⅱ组、Ⅲ组发生率分别为14．8％,68．7％,9．6％,并以前降支为主单支病变多见。Ⅳ组发生率6．9％,主要累及复合前壁,前降支,回旋支及右冠状动脉。泵衰竭、低血压、严重心律失常、AMI扩展、室壁运动失调、左室射血分数≤50％及住院病死率分别为71．6％,41．8％,61．2％,34．3％,100．0％,40．3％和16．4％（P〈0．05或P〈0．01）。结论STEMI患者ECGR．ST-D不同类型对罪犯冠状动脉病变和临床近期预后具有预测作用。     

Electrocardiographic characteristics in angiographically documented occlusion of the dominant left circumflex artery with acute inferior myocardial infarction: limitations of ST elevation III/II ratio and ST deviation in lateral limb leads

Background

The prognosis of dominant left circumflex artery (LCx) occlusion-related inferior acute myocardial infarction (AMI) patients is poor, but the electrocardiographic (ECG) characteristics of this AMI entity have not been described.

Methods

One hundred thirty-five patients with first dominant right coronary artery (RCA) or dominant LCx-related inferior AMI were included. The characteristics of ECG obtained on admission for 55 patients with culprit lesions proximal to the first major right ventricular (RV) branch of dominant RCA (group proximal dominant RCA), 62 patients with culprit lesions distal to the first major RV branch of dominant RCA (group distal dominant RCA), and 18 patients with culprit lesions in dominant LCx (group dominant LCx) were compared.

Results

There were no significant differences among the 3 groups in the prevalence regarding an S/R ratio greater than 1:3 in aVL, ST elevation in aVR (ST↑_aVR), ST depression in aVR (ST↓_aVR) of 1 mm or more, and atrioventricular block. Greater ST elevation in lead III than in II and greater ST depression in aVL than I showed specificity of 17% and 44% to identify dominant RCA as culprit lesion, respectively. All 3 groups could be distinguished on the basis of ST↑_V4R, ST↓_V4R, ST↓_V3/ST↑_III of 1.2 or less, and ST↓_V3/ST↑_III of more than 1.2.

Conclusions

Greater ST elevation in lead III than in II, greater ST depression in aVL than I, and an S/R ratio of greater than 1:3 in aVL were not useful to discriminate between dominant RCA and dominant LCx occlusion-related inferior AMI. ST-segment deviation in lead V₄R and the ratio of ST↓_V3/ST↑_III were useful in predicting the dominant artery occlusion-related inferior AMI.     

Behavior of the terminal T wave during exercise in normal subjects, patients with symptomatic coronary artery disease and apparently healthy subjects with abnormal ST segment depression

The Q-T interval and apex of T wave to end of T wave (aT-eT) interval were measured by computer in four age-matched study groups at rest and during exercise to determine whether: the behavior of the aT-eT interval differs in patients with myocardial ischemia when compared with normal subjects, and the behavior of the aT-eT interval differs in subjects with true positive and false positive ST segment responses. Group I consisted of 57 normal subjects. Group II consisted of 41 symptomatic patients with documented coronary artery disease. A group of apparently healthy subjects with asymptomatic ST segment depression during exercise was divided into two additional groups: Group III, those without coronary artery disease; and Group IV, those with coronary artery disease. Subjects were excluded from the study if they had left ventricular hypertrophy or an intraventricular conduction defect or were taking digitalis or type I antiarrhythmic agents. There were no significant differences in the aT-eT interval and aT-eT/Q-T ratio among the four study groups when compared at rest; however, during exercise at similar heart rates, the aT-eT interval was significantly shorter and the aT-eT/Q-T ratio significantly smaller in Groups II and IV, the subjects with coronary artery disease, than in Group I, the normal subjects. The aT-eT interval and aT-eT/Q-T ratio measurements in Group III did not differ from those in Group I at rest or during exercise. In conclusion, the aT-eT interval and aT-eT/Q-T ratio may reflect changes in myocardial repolarization in exercise-induced ischemia and may have potential for future clinical application.     

Precordial ST segment depression in acute inferior myocardial infarction: the importance of posterolateral wall infarction

To determine whether precordial ST segment depression during acute inferior myocardial infarction indicates posterolateral wall ischemia, anatomical predominance of coronary circulation was examined by coronary angiography and evaluated in 43 patients who experienced first acute inferior myocardial infarction. Among patients who underwent intracoronary thrombolysis within six hours from the onset of symptoms, the infarct-related artery was the right coronary artery (RCA) in 35. In addition, their early 12-lead electrocardiographic features were compared with those in eight patients having the infarct-related left circumflex coronary artery (group Cx). Thirty-five patients with RCA obstruction were categorized in four groups: Four patients with left predominant type (group L), 10 with balanced type (group B), five with right super-predominant type (group SR), and 16 with right intermediate type (group RI). Seventeen of the 21 patients in groups SR and RI demonstrated precordial ST segment depression, whereas it was present in only six of the 14 patients in groups L and B (p less than 0.05). Of the 29 patients in groups SR, Cx and RI, total ST segment depression in leads V1 through V4 (sigma ST) was greater in the 14 patients in groups L and B (p less than 0.05) than in other groups. Furthermore, in these 29, all patients in groups SR and Cx had greater sigma ST than did the patients in group RI (p less than 0.05). There was no significant difference in sigma ST between groups SR and Cx. Precordial ST segment depression did not correlate with concomitant disease of the left anterior descending artery and was not a mirror image of ST segment elevation in inferior leads. On thallium-201 scintigraphy, additional perfusion defects of the posterolateral wall were present in all eight patients in group Cx and in ten of the 21 patients in groups SR and RI. Thus, precordial ST segment depression during acute inferior myocardial infarction seemed to be affected by the pattern of coronary circulation. It was concluded that this ST depression represents more extensive involvement of the posterolateral wall in patients with right predominant coronary circulation as well as in those with left circumflex artery obstruction.