Myocardial viability in patients with thrombolyzed myocardial infarction: Is it assessable by predischarge exercise electrocardiography test?

BACKGROUND: Most studies concerning exercise electrocardiography (ECG) testing after acute myocardial infarction (AMI) were carried out in the prethrombolytic era. ST-segment elevation in the infarction area during exercise has usually been interpreted as indicating the presence of dyskinesia as a result of extensive left ventricle damage. HYPOTHESIS: This study was undertaken to evaluate the contributions of exercise-induced ST-segment elevation and T-wave pseudonormalization to the assessment of myocardial viability in patients with thrombolyzed myocardial infarction (MI), compared with low-dose dobutamine echocardiography. METHODS: The study comprised 52 consecutive patients with AMI treated with thrombolysis. All patients underwent low-dose dobutamine echocardiography and symptom-limited exercise testing before discharge. RESULTS: Nineteen patients showed ST-segment elevation (Group 1), 9 showed isolated T-wave pseudonormalization (Group 2), and 24 patients did not exhibit either of these ST-T segment changes (Group 3). Low-dose dobutamine echocardiography revealed evidence of viability in 16 patients (84%) in Group I (p = 0.01), 5 (56%) in Group 2 (p = NS), and 11 patients (46%) in Group 3 (p = NS). CONCLUSION: Exercise-induced ST-segment elevation may contribute to the evaluation of myocardial viability in patients with AMI treated with thrombolysis. However, in the absence of exercise-induced ST-segment elevation, further noninvasive studies might be indicated to assess myocardial viability.     

ST-segment elevation during dobutamine stress testing predicts functional recovery after acute myocardial infarction

OBJECTIVES: The aims of this study were (1) to assess the relation between ST-segment elevation and wall motion response occurring during dobutamine testing and (2) to evaluate the usefulness of stress-induced ST-segment elevation for predicting functional recovery after acute myocardial infarction. BACKGROUND: Clinical significance of stress-induced ST-segment elevation after acute myocardial infarction remains controversial. According to previous studies, it may reflect a larger infarcted area, depressed left ventricular function, left ventricular aneurysm, stress-induced dyskinesia, residual myocardial ischemia, or viability in the affected region. Whether transient ST-segment elevation occurring during dobutamine testing may predict functional recovery is unknown. METHODS AND RESULTS: We studied 38 patients who underwent dobutamine stress testing early (5 +/- 2 days) after a first acute myocardial infarction. Dobutamine was infused at increasing doses from 5 to a maximum of 40 microg/kg per minute, with the addition of up to 1 mg of atropine if the target rate could not be reached by dobutamine alone. Twelve-lead electrocardiography and cross-sectional echocardiography were continuously monitored throughout the test. Dobutamine-induced ST-segment elevation was defined as a new or worsening >/=1 mm elevation, 80 ms after J point, in >/=2 infarct-related leads. Quantitative angiography was available in all patients before hospital discharge. Follow-up resting echocardiography was recorded in all patients 12 to 18 months after the acute event. ST-segment elevation was observed in 20 of the 38 patients. There were no significant differences between patients with and those without dobutamine-induced ST-segment elevation in age, site of infarction, peak level of total creatine kinase enzyme, and use of thrombolytic therapy, angioplasty, or both. Persistent akinesis without change during dobutamine stress testing was more frequently observed in patients without ST elevation (P <. 05). A biphasic response during dobutamine testing was more frequently observed in patients with ST-segment elevation (P =.01). Multivariate analysis selected 2 independent variables associated with ST-segment elevation: a biphasic response during dobutamine stress (chi-square = 7.3; P =.007) and the minimal lumen diameter of the infarct-related vessel at quantitative angiography (chi-square = 5.5; P <.02). Functional recovery was demonstrated in 26 patients. Sensitivity of ST-segment elevation for the prediction of functional recovery was 69%, specificity 83%, positive predictive value 90%, and accuracy 74%. Two independent variables predicting functional recovery were selected: dobutamine-induced ST-segment elevation (chi-square = 9.1; P =.003) and a biphasic response during stress (chi-square = 6.15; P =.013). CONCLUSIONS: Dobutamine-induced ST-segment elevation in the infarct-related leads is an ancillary sign of viable myocardium in jeopardy. It has a high specificity and an acceptable sensitivity for the prediction of functional recovery after acute myocardial infarction.     

Prognostic usefulness of dobutamine-induced ST-segment elevation and T-wave normalization after uncomplicated acute myocardial infarction

We followed 229 consecutive patients exhibiting negative T waves on infarct-related electrocardiographic leads; these patients underwent dobutamine stress echocardiography within 10 days after a first uncomplicated acute myocardial infarction. T-wave normalization, but not ST-segment elevation, recognized patients at higher risk of cardiac events and optimized the prognostic accuracy of both myocardial viability and ischemia, to which it was correlated and became an independent predictor in cases of subdiagnostic stress echocardiography.     

ST segment elevation during dobutamine stress echocardiography after acute myocardial infarction: Clinical significance and correlation with contractile recovery

ObjectivesThe aim of this study was the evaluation of the value of dobutamine stress induced ST-segment elevation after acute myocardial infarction in predicting spontaneous contractile recovery.MethodsFifty eight consecutive patients were studied within 7 days after first acute myocardial infarction (AMI) with dobutamine stress echocardiography (DSE). A score model based on 16 segments and four grades was used to assess the left ventricular function and a twelve-lead electrocardiography was continuously monitored throughout the test. Follow up was performed by trans-thoracic echocardiography at 90 days. At follow up, contractile recovery was defined as improvement of wall motion score by more than one grade in at least two myocardial segments.ResultsST-segment elevation was observed in 24 (41%) out of the 58 patients studied. During DSE; persistent segmental wall motion abnormalities were more frequently observed in patients without ST-segment elevation while improvement without subsequent worsening was more frequently observed in patients with ST-segment elevation (P = 0.001). On follow up, contractile recovery was reported in 37 (64%) patients, it was more frequently observed in patients who already developed ST-segment elevation during DSE (P = 0.007). Dobutamine induced ST-Segment elevation has the sensitivity, specificity, positive and negative predictive values of 66%, 86%, 88% and 53%, respectively to predict spontaneous contractile recovery after AMI, while the combined sensitivity, specificity, positive and negative predictive values of dobutamine echocardiography and electrocardiography were 73%, 89%, 94% and 64%, respectively.ConclusionsDobutamine stress induced ST segment elevation occurring in electrocardiographic leads exploring an infarct area is a predictor of spontaneous contractile recovery after AMI particularly when combined with echocardiogarphic evidence of myocardial viability.     

Detection and clinical usefulness of a biphasic response during exercise echocardiography early after myocardial infarction

OBJECTIVE: The aim of this study was to determine the accuracy of exercise echocardiography (EE) for detecting infarct-related artery (IRA) stenosis and predicting functional recovery early after acute myocardial infarction (AMI). BACKGROUND: Dobutamine stress echocardiography is widely used for identifying jeopardized myocardium. The clinical usefulness of a biphasic response detected during EE has never been investigated. METHODS: A total of 114 consecutive patients with a first AMI and > or = 2 dyssynergic segments in the infarct-related territory underwent semi-supine continuous EE 6 +/- 2 days after AMI. Quantitative coronary angiography was performed in all patients after EE. A follow-up echocardiogram was obtained one month later. RESULTS: Ninety-seven patients had significant (> or = 50%) IRA stenosis, and 26 had multivessel disease. Residual ischemia was identified in 77 patients (biphasic response in 62 and worsening response in 15). The sensitivity and specificity of ischemia during EE for predicting IRA stenosis were 75% and 76%, respectively. The sensitivity of a biphasic response was higher than the sensitivity of a worsening response (61% vs. 14%, p < 0.0001). Wall motion abnormalities induced in other vascular territories were specific (97%) and moderately sensitive (62%) for the detection of multivessel disease. Functional recovery was observed in 75 patients. Two independent variables predicted contractile recovery: contractile reserve during EE (p < 0.0001) and elective angioplasty of the IRA (p = 0.002). A biphasic response, but not sustained improvement, predicted reversible dysfunction (73% vs. 9%, p < 0.0001). CONCLUSIONS: A biphasic response can be detected during exercise. Exercise echocardiography is an accurate tool for detecting IRA stenosis and predicting functional improvement early after AMI.     

Dobutamine-induced ST-segment elevation associated with a biphasic response of wall motion in patients with a recent myocardial infarction is caused by myocardial ischaemia and is abolished by revascularization of the infarct-related artery

OBJECTIVE: ST-segment elevation is frequently induced by dobutamine in patients with a recent myocardial infarction and may represent dyskinesia of the infarcted region or myocardial viability and ischaemia. Revascularization of the infarct-related artery may abolish myocardial ischaemia, and thus represents a useful tool to verify the significance of this finding. The aim of this study was to assess the relation between ST-segment elevation and wall motion response during dobutamine echo stress test and to evaluate the effect of coronary revascularization with percutaneous coronary angioplasty of the infarct-related artery on stress test results. METHODS AND RESULTS: Twenty-two patients (17 men; mean age 58+/-12 years) with a first acute myocardial infarction (5 anterior (23%) and 17 (77%) inferior) who showed ST-segment elevation during a dobutamine echo stress test performed early (7+/-5 days) after the acute event where included in the analysis. All patients underwent coronary arteriography followed by percutaneous revascularization with coronary angioplasty or atherectomy with or without stenting of the culprit lesion and a second dobutamine echo stress test at a mean of 40+/-20 days after revascularization. The minimal lumen diameter increased from 0.63+/-0.36 to 3+/-0.44 mm and % diameter stenosis decreased from 80+/-11 to 12+/-7 after revascularization. At baseline evaluation there were 62 normal moving segments (34%), 57 (32%) akinetic and 62 (34%) hypokinetic segments within the area at risk. Maximal ST-segment shift changed from a basal mean value of 0.41+/-0.6 to a peak value of 2.15+/-0.9 mm; angina developed in 6/22 patients (22%). A biphasic response to dobutamine indicative of myocardial ischaemia within the infarcted area was observed in 20/22 patients (91%) and in 54/74 (73%) segments showing wall motion abnormalities. After revascularization of the infarct-related artery 78 (43%) segments were considered to be normal, 46 (25%) akinetic and 57 (32%) hypokinetic. Dobutamine-induced ST-segment elevation in 6/22 cases (27%), but the amount of ST-segment shift at peak stress was significantly reduced (from 2.15+/-0.9 to 0.30+/-0.5 mm) and angina was present in 1 patient only (5%) despite a significant increase of double product compared to the pre-revascularization test (from 17,348+/-3536 to 21,005+/-4105, p < 0.003). At echocardiographic analysis, ischaemia involved only 4 segments (2%), 3 of them showing the persistence of a biphasic response to dobutamine. CONCLUSIONS: In patients with a recent myocardial infarction and no baseline dyskinesia dobutamine-induced ST-segment elevation in the infarct-related leads is usually associated with a biphasic response of wall motion within the infarcted region and may be considered an ancillary sign of myocardial ischaemia because it is abolished in the great majority of cases by successful revascularization of the infarct-related artery.     

Significance of dobutamine-induced changes in QT dispersion early after acute myocardial infarction.

This study sought to examine the effects of graded dobutamine infusion on QT dispersion early after acute myocardial infarction (AMI) and to investigate the relation of dobutamine-induced changes in QT dispersion to wall motion responses. Seventy-eight patients with a first AMI underwent dobutamine-atropine stress echocardiography 5 +/- 2 days after admission. Contractile reserve was identified in 45 patients and ischemic myocardium in 40. Sixteen patients had persistent akinesia. The best cut-off value of QT dispersion on the baseline electrocardiogram for predicting myocardial viability was 65 ms (sensitivity and specificity of 68%). Dobutamine infusion increased QT dispersion only in patients with viable myocardium (61 +/- 18 to 83 +/- 19 ms, p = 0.003) and/or ischemia (72 +/- 16 to 112 +/- 25 ms, p < 0.0001). No change was observed in patients with persistent akinesia (84 +/- 10 to 87 +/- 15 ms, p = NS). QT dispersion increased by 22 +/- 12 ms with administration of low-dose dobutamine in patients who had viable myocardium and by 47 +/- 21 ms with administration of low- to high-dose dobutamine in patients with ischemic myocardium. An increase in QT dispersion of > or = 20 ms from at rest to low-dose dobutamine infusion was associated with myocardial viability with a sensitivity of 78% and a specificity of 79%, whereas an increase in QT dispersion of > or = 10 ms from low- to high-dose dobutamine infusion predicted ischemic myocardium with a sensitivity of 85% and a specificity of 82%. In conclusion, (1) low QT dispersion on the baseline electrocardiogram is determined by the presence of viable myocardium, (2) a dobutamine-induced increase in QT dispersion is associated with viable and jeopardized myocardium, and (3) unchanged QT dispersion during dobutamine stress is a simple marker of extensive necrosis.     

Low-level exercise echocardiography detects contractile reserve and predicts reversible dysfunction after acute myocardial infarction: comparison with low-dose dobutamine echocardiography.

OBJECTIVES: The aim of this study was to evaluate low-level exercise echocardiography (LLEE) in detecting contractile reserve and predicting functional improvement of akinetic myocardium early after acute myocardial infarction (AMI). BACKGROUND: Experimental and clinical studies have shown that low-dose dobutamine enhances contractile function of dyssynergic but viable myocardium in patients with recent AMI. We hypothesized that endogenous catecholamines produced during a LLEE test could serve as a myocardial stressor to elicit contractile reserve. METHODS: Fifty-two consecutive patients with first AMI and > or =2 akinetic segments in the infarct-related territory underwent 5 +/- 2 days after AMI low-dose dobutamine echocardiography (LDDE) (5, 10 and 15 microg/kg/min) and LLEE (25 W during 3 min on a supine bicycle, with continuous echocardiographic recording). Both tests were performed on the same day, in random order. Follow-up echocardiography was obtained one month later. Regional wall thickening was semi-quantitatively assessed using a 16-segment, 5-grade scale model. Contractile reserve was defined as improvement in wall thickening of > or =1 grade. RESULTS: Mean increase in heart rate during stress tests was 15 +/- 7 beats/min with LLEE and 13 +/- 6 beats/min with LDDE (p = NS). Contractile reserve was detected in 119 (55%) of 217 akinetic segments at LLEE and in 137 (63%) segments at LDDE. At follow-up study, functional improvement was identified in 139 (64%) segments. Sensitivity, specificity and positive and negative predictive values for predicting functional recovery were 81%, 92%, 95% and 73%, respectively, for LLEE, and 91%, 86%, 92% and 84%, respectively, for LDDE. Moreover, there was a good correlation between systolic wall thickening measured in the center of the dyssynergic area during stress tests and at follow-up study: r = 0.77, p < 0.001 with exercise testing and r = 0.73, p < 0.001 with dobutamine testing. CONCLUSIONS: Low-level exercise echocardiography provides a promising alternative to LDDE for identifying myocardial viability and predicting reversible dysfunction early after AMI.     

Dispersion of ventricular repolarization is determined by the presence of myocardial viability in patients with old myocardial infarction. A dobutamine stress echocardiography study.

AIMS: The study sought to investigate the relationship of myocardial viability detected by dobutamine stress echocardiography to changes of QT dispersion and to the presence of arrhythmias during dobutamine infusion in patients with old myocardial infarction. We also examined whether patency of the infarct-related artery is associated with the presence of myocardial viability and QT dispersion. BACKGROUND: QT dispersion and myocardial variability have been associated with the presence of arrhythmias during late post infarction but not during dobutamine stress. Restoration of anterograde coronary flow has beneficial effects on ventricular systolic function and repolarization, suggesting that the extent of viable myocardium may determine ventricular repolarization. METHODS: Seventy five patients with previous myocardial infarction were studied in a low dose (up to 20 microg(-1) x kg(-1) x min(-1)) dobutamine stress echocardiography study. ECGs were obtained at rest and peak stress for measurement of QT intervals. The presence of ventricular arrhythmias (Lown grade >lb) during stress was noted. A reduction in the total wall motion score of the left ventricle at peak stress confirmed the presence of myocardial viability. RESULTS: Dobutamine infusion increased QT dispersion in all patients (P<0.01). Patients with myocardial viability had a lower resting QT dispersion (P<0.05) and a greater increase in QT dispersion% (P<0.01) than patients without. The combination of a resting QT dispersion <65 ms or an increase in QT dispersion >30% predicted viability with a sensitivity of 67%, a specificity of 96%, and an accuracy of 78%. A patent infarct-related artery, as well as ventricular arrhythmias, were more commonly observed in patients with evidence of viable myocardium (P<0.05). Patients with arrhythmias had a higher QT dispersion than patients without (P<0.05). CONCLUSION: The combination of a resting QT dispersion +/-65 ms or an increase in QT dispersion >30% predicts the presence of viable myocardium and thus, may represent a simple index for the assessment of viability in everyday clinical practice. Myocardial viability is related to a patent coronary artery and to a high incidence of arrhythmias accompanied by a greater increase in QT dispersion at peak dobutamine infusion.     

Value of t-wave direction with lead iii st-segment depression in acute anterior wall myocardial infarction: Electrocardiographic prediction of a “wrapped” left anterior descending artery

Background: Lead III ST-segment depression during acute anterior wall myocardial infarction (AMI) has been attributed to reciprocal changes. However, the value of the T-wave direction (positive or negative) in predicting the site of obstruction and type of the left anterior descending (LAD) artery is not clear and has not been studied before. Hypothesis: The aim of the study was to assess retrospectively the correlation between two patterns of lead III ST-segment depression, and type of LAD artery and its level of obstruction during first AMI. Methods: The study group consisted of 48 consecutive patients, admitted to the coronary care unit for first AMI, who showed ST-segment elevation in lead aVL and ST-segment depression in lead III on admission 12-lead electrocardiogram. The patients were divided by T-wave direction into Group 1 (n = 31), negative T wave, and Group 2 (n = 17), positive T wave. The coronary angiogram was evaluated for type of LAD (“wrapped”, i.e., surrounding the apex or not), site of obstruction (pre- or postdiagonal branch), and other significant coronary artery obstructions. Results: Mean lead III ST-segment depression was 1.99 ± 1.32 mm in Group 1 and 1.13 ± 0.74 mm in Group 2 (p = 0.004); mean ST-segment elevation in aVL was 1.35 ± 0.84 mm and 1.23 ± 0.5 mm, respectively (p = 0.5). A wrapped LAD was found in 12 patients (38.7%) in Group 1 and in 13 in Group 2 (76.4%) (p = 0.02). The sensitivity of lead III ST-segment depression with positive T wave to predict a wrapped LAD was 52%, and the specificity was 82% with a positive predictive value of 76%. On angiography, 25 patients (80%) in Group 1 and 13 (76%) in Group 2 had prediagonal occlusion of the LAD (p = 0.77 ). No significant difference between groups was found for right and circumflex coronary artery involvement or incidence of multivessel disease. Conclusions: The presence of lead III ST-segment depression with positive T wave associated with ST-segment elevation in aVL in the early course of AMI can serve as an early electrocardiographic marker of prediagonal occlusion of a “wrapped” LAD.     

心电图在急性心肌梗死超急性期诊断中的应用

目的：探讨心电图诊断急性心肌梗死（心梗）超急性期的临床价值。方法选择2013年1月至2015年1月经我院确诊的90例急性心梗超急性期患者,根据发病时间将其随机分为 A、B、C 三组,分别有患者55例、18例和17例,发病时间分别为≤2 h、2～6 h 及6～8 h。对三组患者行24 h 心电监测,详细记录各组心电图 Q 波、ST 段和 T 波的变化情况,并统计分析阳性改变率。结果经24 h 心电监测发现,所有患者的心电图阳性改变主要是 Q 波、ST 段及 T 波的改变。其中,ST 段及 T 波的改变诊断急性心梗超急性期的敏感性和特异性、阳性预测值与阴性预测值均高于 Q 波改变。三组的心电图阳性改变发生率依次为81．82％、38．89％和17．65％,A 组均显著高于 B、C 组（P ＜0．05）。A 组患者中,ST 段抬高型心梗者的心电图诊断阳性率显著高于非 ST 段抬高型心梗者（34．09％ vs．18．18％,P ＜0．05）。结论对急性心梗超急性期患者,尤其是发病2 h 内的患者进行24 h 心电监护,对准确判断病情和及时施治非常关键。T 波宽大、高耸及 ST 段抬高可作为急性心梗超急性期的特征性心电图表现,为临床诊断和治疗提供参考依据。     

Normalization of abnormal T-waves during stress testing does not identify patients with reversible perfusion defects

OBJECTIVE: To determine if T-wave normalization during exercise or dobutamine stress testing identified patients with myocardial ischemia as indicated by reversible perfusion defects. METHODS: Exercise or dobutamine stress tests with perfusion scintigraphy were performed in 1,173 patients with abnormal T-waves on their baseline electrocardiograms. The results of perfusion scintigraphy were compared in patients with and without stress-induced T-wave normalization. RESULTS: Only 33 of 270 patients with reversible perfusion defects (12.2%) had T-wave normalization during stress while 76.4% of 140 patients who had T-wave normalization during stress did not have a reversible perfusion defect. Results were similar for patients who did or did not reach 85% of their maximal predicted heart rate, for patients with and without Q-wave infarction on the baseline EKG and for patients who did or did not have ischemic ST-segment depression during stress. CONCLUSIONS: T-wave normalization during stress testing has low sensitivity and poor positive predictive value for stress-induced reversible myocardial ischemia.     

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.     

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.     

Rare Giant T-Wave Inversions Associated With Myocardial Stunning: Report of 2 Cases

Prominent T-wave inversions are well recognized electrocardiographic signs that can occur in acute myocardial infarction (AMI). However, the giant negative T waves may be associated with myocardial stunning without AMI.This case report describes 2 patients without AMI who developed rare giant T-wave inversions measuring up to 35 mm in depth and QT prolongation after admission to hospital. While 1 patient presented with acute pulmonary edema, the other patient presented with severe chest pain at rest and transient ST elevation.The giant T-wave inversion with QT prolongation may be caused by myocardial stunning due to the triple vessel diseases and elevated wall stress, high-end diastolic pressure and decreased coronary arterial flow during pulmonary edema in the first patient. The giant T-wave inversion with QT prolongation in the second patient may be caused by myocardial stunning due to the left anterior descending artery spasm (transient ST elevation) leading to transient total occlusion of left anterior descending artery. Percutaneous coronary intervention was successfully undergone for both patients. The patients remained well.The electrophysiologic mechanism responsible for giant T-wave inversion with QT prolongation is presently unknown. The two cases demonstrate that the rare giant negative T waves may be associated with myocardial stunning without AMI.     

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。     

Significance of T-wave changes during early dobutamine stress echocardiography in patients with Q-wave acute myocardial infarction.

The relation between T-wave changes and regional contraction during dobutamine stress echocardiography at low (5 to 10 microg/kg/min) and high (20 to 40 microg/kg/min) doses in 43 consecutive patients, early (7+/-2 days) after first recent Q-wave acute myocardial infarction has been evaluated. T-wave changes detected in > or =2 infarct-related electrocardiographic leads during dobutamine infusion were defined as follow: (1) negative T waves becoming positive, (2) positive T waves becoming upright > or =2 mm, and (3) negative T waves becoming upright > or =2 mm from baseline. Wall motion score index (WMSI) was defined as the sum of the echocardiographic scores of 16 segments divided by total segments considered at baseline, and at low and peak doses of dobutamine. Patients were classified according to the absence or presence of dobutamine T-wave changes. Those without T-wave changes had a significantly higher WMSI at rest (1.68+/-0.23 vs 1.50+/-0.21; p <0.05) and at peak (1.77+/-0.34 vs 1.51+/-.30 p <0.05) of dobutamine stress testing, without higher incidence of viability, homozonal, and heterozonal ischemia and chest pain. The angiographic patterns were similar between groups. Regression analysis showed a significant correlation between WMSI and T-wave amplitude at baseline (R = 0.38, p = 0.01) and at peak dobutamine stress testing (R = 0.50, p = 0.0006). The sensitivity sensitivity, specificity, and accuracy of T-wave changes to detect myocardial viability were 0.27, 0.84, and 0.70, respectively. The sensitivity, specificity, and accuracy of T-wave changes to detect homozonal ischemia were 0.76, 0.27, and 0.46, respectively. In conclusion, dobutamine-induced T-wave changes are associated with a greater extent of wall motion abnormalities both at rest and at peak stress echocardiography, but they are of little value in predicting myocardial viability when analyzed early after myocardial infarction.     

QT dispersion, T-wave projection, and heterogeneity of repolarization in patients with coronary artery disease

The clinically useful prognostic value of precordial QT dispersion in patients with heart disease is generally attributed to its measurement of regional heterogeneity of ventricular repolarization. However, when repolarization is abnormal, differences in measured QT intervals might result simply from variation in projection of the T-wave loop. To provide insight into the mechanism of QT dispersion, we used an analog device to transform conventional 12-lead electrocardiograms (ECGs) of 78 patients to derived 12-lead ECGs based on the heart vector. Because the electrical activity of the heart is represented by a single dipole, all QT dispersion in the transformed ECGs results from variation in projection of the T-wave loop and cannot be due to local heterogeneity of repolarization. Measured as the difference between the longest and shortest precordial QT intervals, QT dispersion in the derived ECGs, with no local heterogeneity of repolarization, was 53 +/- 49 ms (mean +/- SD). QT dispersion in these derived ECGs was similar in magnitude to that measured from the original standard 12-lead ECGs in these patients (49 +/- 23 ms, p = NS). Therefore, the precordial QT dispersion measured from standard ECGs of patients with coronary artery disease can be explained by interlead variation in precordial projection of the T-wave loop. Although regional heterogeneity might still contribute to precordial repolarization findings and to prognosis, this is not required to explain the QT dispersion observed in patients with coronary artery disease. Therefore, QT interval dispersion is not equivalent to heterogeneity of repolarization.     

Accuracy of low load exercise-induced T wave normalization in predicting the presence of contractile reserve after an anterior myocardial infarction

Background and Methods. Exercise-induced T wave normalization occurring at a low (≤ 50 watt) workload in infarct-related electrocardiographic leads was studied in 30 consecutive patients with a recent transmural anterior acute myocardial infarction. Patients underwent both ergometric stress testing (within 30 days after the infarction) and low dose dobutamine echocardiography. The T wave normalization was considered significant when it occurred in at least two infarct-related leads. A significant contractile reserve was considered present in an infarcted region when 50% or more of the dyskinetic segments functionally improved on exercise during dobutamine infusion.Results. Eighteen patients showed exercise-induced T wave normalization (group 1), and 12 patients did not (group 2). Myocardial contractile reserve in the infarct area was detected in 16 patients of group 1 (88%) and in 3 patients (25%) of group 2 (p=0.004). The overall sensitivity, specificity, and diagnostic accuracy of T wave normalization, as it reflects contractile reserve in the infarct area, were 84%, 82%, and 83%, respectively.Conclusion. Low load exercise-induced T wave normalization in infarct-related leads appears to be an accurate marker of residual contractile reserve in the infarct area in patients with recent transmural acute anterior myocardial infarction.     

Prognostic value of electrocardiographic exercise testing and noninvasive assessment of left ventricular ejection fraction soon after acute myocardial infarction

To determine the relative value of clinical findings, results of low-level treadmill electrocardiographic (ECG) exercise testing and left ventricular (LV) ejection fraction (EF) for predicting cardiac events in the year after an acute myocardial infarction (AMI), 72 patients who had had an uncomplicated AMI were studied with either radionuclide angiography or 2-dimensional echocardiography to assess LVEF and a low-level treadmill exercise test before hospital discharge. All patients were followed for 1 year. Nineteen patients (26%) had at least 1 cardiac event: coronary artery bypass grafting (11 patients), recurrent AMI (6 patients) or cardiac death (6 patients). Multiple logistic regression analysis revealed that total cardiac events were predicted by exercise ECG ST-segment depression or angina, prior AMI, ventricular ectopic activity during exercise and digoxin therapy (cumulative r = 0.58, p less than 0.001). Coronary artery bypass grafting was predicted by exercise ECG ST-segment depression or angina (r = 0.29, p = 0.01). Recurrent AMI was predicted by exercise ECG ST-segment depression or angina, prior AMI and ventricular ectopic activity during exercise (cumulative r = 0.49, p less than 0.001). Cardiac death was predicted by an LVEF of 40% or less (r = 0.38, p = 0.01). The presence of both an LVEF of 40% or less and ECG ST-segment depression on treadmill exercise testing defined a subgroup of patients with a high incidence of early cardiac death (33%).(ABSTRACT TRUNCATED AT 250 WORDS)