Prognostic value of exercise-induced QT dispersion in patients after acute myocardial infarction

BACKGROUND: Electrocardiographic exercise tests are widely recommended for patients before discharge after myocardial infarction, what justify the search for new variables which may improve their prognostic value. QT dispersion in 12 lead ECG reflects the heterogeneity of ventricular repolarisation. Increased QT dispersion is a noninvasive marker of ischaemia and electrical instability. AIM: Evaluation of the prognostic value of exercise-induced changes of QT dispersion in patients after an acute myocardial infarction. METHODS: Heart rate limited treadmill exercise test according to modified Bruce was performed 14+/-5 days after infarction in 77 patients (age 56+/-11,8 female). QT dispersion was measured at rest and on peak exercise. Patients were followed up for mean 88 months. RESULTS: QT dispersion was higher at peak exercise in those patients who died due to cardiovascular causes (n=8) or suffered from non-fatal myocardial infarction during follow-up (n=15), than in remaining group (71+/-20 vs 58+/-22 msec, p<0.01). At rest QT dispersion was similar in both groups (64+/-17 vs 66+/-20 msec, NS). CONCLUSIONS: The lack of an exercise-induced decrease in QT dispersion identifies a subgroup of patients after myocardial infarction with a poor long-term prognosis.     

陈旧性心肌梗死患者梗死部位存活心肌对QT离散度的影响

目的　探讨陈旧性心肌梗死 (OMI)患者梗死部位存活心肌对QT离散度 (QTd)的影响及意义。方法　对 81例Q波型OMI患者行18F 脱氧葡萄糖 (FDG)正电子发射型计算机断层 (PET)心肌葡萄糖代谢与99Tc 甲氧基异基异腈 (MIBI)心肌灌注显像 ,以检测梗死部位存活心肌程度。所有患者在PET检查前 1至 4天内记录静态 12导联同步心电图 ,计算QTd。结果　坏死心肌程度与QTd呈正相关 ,梗死部位存活心肌程度与QTd呈负相关 ,相关系数分别为 0 4 5 (P <0 0 0 1)和 0 4 3 (P <0 0 0 1) ,即坏死心肌越少 ,梗死部位存活心肌百分比越高 ,QTd越低。以PET检测梗死部位存活心肌结果为对照 ,用QTd≤ 70ms判断梗死部位存活心肌时 ,敏感性为 82 8% ,特异性为 91 3 % ,准确性为 85 2 %。结论　坏死心肌程度和梗死部位存活心肌百分比与QTd显著相关 ,提示QTd有可能作为初步估测Q波型心肌梗死部位存活心肌程度的一种简便方法。     

Dynamics of QT dispersion in acute myocardial infarction

BACKGROUND: We studied the dynamics of QT dispersion in patients with acute myocardial infarction, and compared them with those in controls. METHODS AND RESULTS: Serial electrocardiograms of patients admitted to our institute with acute myocardial infarction were analyzed for QT dispersion, and compared with those of healthy age- and sex-matched controls. QT dispersion from 12 leads was measured as maximum QT minus minimum QT interval in ms. The mean QT dispersion of 114 +/- 29.6 ms was significantly higher in patients with acute myocardial infarction on admission as compared to 51.45 +/- 5.56 ms in controls (p < 0.001). QT dispersion showed a dynamic change in patients with acute myocardial infarction who were thrombolyzed, being 109.11 +/- 5.77 ms, 87.59 +/- 5.88 ms, 75.89 +/- 18.33 ms, and 68.20 +/- 12.66 ms on admission, post-thrombolysis, and on days 3 and 7, respectively. During a similar time period, nonthrombolyzed patients showed a QT dispersion of 132.38 +/- 36.04 ms, 130.47 +/- 34.42 ms, 111.11 +/- 24.94 ms, and 106.25 +/- 27.64 ms, respectively: the difference between the 2 groups at all periods was significant (p < 0.01). Mean QT dispersion values in patients who developed ventricular tachycardia or ventricular fibrillation were significantly higher than in patients who did not develop ventricular tachycardia or ventricular fibrillation (p < 0.01). CONCLUSIONS: Mean QT dispersion is significantly increased after acute myocardial infarction, and shows a dynamic decrease with time, the difference being more marked in thrombolyzed patients. Mean QT dispersion levels are higher in patients with ventricular tachycardia and ventricular fibrillation compared to patients with acute myocardial infarction without these arrhythmias. The changes in QT dispersion are dynamic, and it may serve as a non-invasive marker of susceptibility to malignant ventricular arrhythmias.     

QT dispersion and prognosis after coronary stent placement in acute myocardial infarction

BACKGROUND: QT dispersion is increased in acute myocardial infarction (AMI), but the relation of QT dispersion to prognosis has not yet been fully elucidated. HYPOTHESIS: The purpose of this study is to evaluate prospectively whether QT dispersion is associated with the risk of major adverse cardiac events (MACEs) and mortality after successful coronary stenting in AMI. METHODS: One hundred and forty-two patients with AMI and undergoing successful percutaneous coronary intervention (PCI) were enrolled in this study. Corrected QT dispersion was measured before and 24 h after PCI. RESULTS: During a period of 4477 person-months, we confirmed 21 cases of MACE. Univariate analysis indicated that corrected QT dispersion before and 24 h after PCI, age, number of Q waves, and Killip class > or = 2 were related to MACE and mortality. By multivariate analysis, corrected QT dispersion before PCI was an independent predictor of MACE and mortality, but corrected QT dispersion at 24 h after PCI was not statistically associated with MACE and mortality. Multiple-adjusted hazard ratios for a 1 standard deviation (SD) magnitude increase in corrected QT dispersion before PCI were 2.24 (95% confidence interval, 1.36-3.68, p = 0.001) for MACE and 2.71 (95% confidence interval, 1.50-4.89, >) for mortality after adjustment for age, gender, ejection fraction, and Killip class > or = 2. CONCLUSIONS: Corrected QT dispersion before PCI is associated with an increased risk of MACE and mortality after successful PCI in patients with AMI.     

Proinflammatory cytokines and myocardial viability in patients after acute myocardial infarction

BACKGROUND: Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) can potentiate heart muscle damage during acute myocardial infarction (AMI). Whether changes in their plasma levels after AMI are dependent on the presence of myocardial viability is unclear. The aim of the study was to estimate the relation of time course of plasma TNF-alpha and IL-6 and the presence of reversible and irreversible myocardial dysfunction in patients early after AMI treated thrombolytically. MATERIAL AND METHODS: Patients (54; mean age 60.4 +/- 11.7 years) with AMI plasma TNF-alpha and IL-6 were evaluated on the 2nd, 10th and 30th day after thrombolysis. Based on the response of dysfunctional segments of myocardium during dobutamine stress echocardiography performed on the 10th day, patients were divided into four groups: A, sustained improvement in contractility; B, biphasic (improvement followed by worsening); C, only worsening; D, no change. Twenty-two healthy persons served as controls. RESULTS: On the 2nd day, all four groups of patients demonstrated increased levels of TNF-alpha and IL-6 and did not differ among one another regarding both cytokines. On the 10th day, plasma TNF-alpha and IL-6 decreased in each group and were the lowest in group A, intermediate in group B and the highest in groups C and D. On the 30th day, both cytokines were not different among all studied groups. CONCLUSION: Elevated plasma TNF-alpha and IL-6 early after AMI decreased more quickly in patients with dysfunctional myocardium comprising not only necrotic but also viable segments. This decline is attenuated by the presence of residual ischemia.     

倍他乐克治疗急性心肌梗死后QT离散度的变化

目的　研究倍他乐克对急性心肌梗死 QT离散度的影响。方法　 5 0例急性心肌梗死 (AMI)患者随机分成治疗组和对照组(n=2 5 ) ,治疗组给予倍他乐克 5 0～ 2 0 0 mg/d,共 3周 ,对照组给予常规治疗 3周。比较两组治疗 3周前后 QT参数。结果　对照组治疗 3周后 QTd、QTcd、QTmax、QTmin、HR均无明显变化 (P>0 .0 5 ) ,治疗组治疗 3周后 QTmax无改变 (P>0 .0 5 ) ,QTmin延长 (P<0 .0 1) ,HR减慢 (P<0 .0 1) ;QTd、QTcd缩短。结论　倍他乐克可延长 AMI患者的 QTmin,对 QTm ax无影响 ,使 QTd减小 ,有利于 AMI患者心肌电活动的一致和稳定 ,减少室性心律失常的发生     

急性心肌梗死患者QT离散度临床意义的探讨

目的：探讨急性心肌梗死患者QT间期离散度与恶性室性心律失常发生率的关系.方法：观察64例AMI患者发病24小时内的QT离散度,并观察其与两周内恶性心律失常发生率的关系.结果：急性心肌梗死组QT离散度较对照组增大;发生恶性心律失常的患者QT离散度与未发生者有显著统计学差异.结论：急性心肌梗死患者QT离散度增大对恶性心律失常的发生有预测性.     

QT dispersion and left ventricular function after stent placement in acute myocardial infarction

BACKGROUND: QT dispersion is increased in acute myocardial infarction (AMI), but the relation of QT dispersion to left ventricular (LV) function has not yet been fully elucidated. The purpose of this study was to evaluate the relationship between QT dispersion and LV function in patients with successful coronary stenting in AMI. METHODS: Seventy five patients with AMI who underwent percutaneous transluminal coronary angioplasty (PTCA) were enrolled in this study. Corrected QT dispersion was measured before, immediately after, 24 h after, 48 h after, and 6 months after PTCA. Left ventricular ejection fraction (LVEF) was evaluated by left ventriculography at 6 months after PTCA. RESULTS: Corrected QT dispersion at 24 h after and 48 h after PTCA were significantly related to LVEF by univariate analysis (r=-0.282, p<0.05 and r=-0.326, p<0.01, respectively). In multiple regression model, corrected QT dispersion at 24 h after and 48 h after PTCA revealed significant associations with LVEF (R(2)=0.441, coefficient=-0.283, p=0.006 and R(2)=0.411, coefficient=-0.225, p=0.039, respectively), but corrected QT dispersion before, immediately after, and 6 months after PTCA were not associated with LVEF. CONCLUSIONS: Corrected QT dispersion at 24 h after and 48 h after PTCA in AMI correlate with LVEF at 6 months after PTCA.     

老年人急性心肌梗死再灌注前后QT离散度的改变

目的 :观察 QT间期离散度 （QTd）在老年急性心肌梗死 （AMI）再通前后的变化。方法 :测量和计算 16 5例老年 AMI患者及 40例正常老年人 QT间期、QTd和校正后 QTd（QTdc）。结果 :老年 AMI患者 QTdc显著长于对照组 （P<0 .0 1） ;AMI患者发生室性心律失常及死亡者的 QTdc明显长于未发生者 （P<0 .0 5 ） ;溶栓或 PTCA术后QTdc显著降低 （P<0 .0 1）。结论 :QTdc与心肌梗死严重性间存在一定相关性 ,QTdc可以作为观察早期溶栓和PTCA术是否成功的间接指标     

体表心电标测测定急性心肌梗死患者QT离散度的探讨

目的 探讨有更大体表取样范围的体表心电标测(BSPM)中反映的QT间期离散度及分布.方法 (1)记录1998年3月至1999年12月间68例急性心肌梗死患者(平均年龄59岁)的96导联体表心电标测图及12导联心电图,分别测定QT间期及QT离散度,并与58名正常对照(平均年龄50岁)进行对比分析.结果 (1)正常人及急性心肌梗死患者BSPM法测得的QT离散度、QT最大值均大于12导心电图值,QT最小值小于12导心电图;(2)正常人BSPM法测得的QTd为(50.6±17.1)ms.最大值多位于左侧胸及偏后部、胸骨上部和右锁骨区,最小值位于胸部偏右下部.急性心肌梗死患者BSPM法测得的QTd为(83.3±28.7)ms,较正常对照组高.QT间期分布发生明显变化,QT间期最大值移至覆盖于心肌梗死部位的体表区域;(3)BSPM法测得QTd的变异系数低于12导心电图.BSPM法区分急性心肌梗死患者与正常人QTd的灵敏度高于12导心电图(分别为81%,58%);特异性分别为91%和90%.结论 12导心电图及BSPM方法均表明急性心肌梗死患者QT离散度增加,BSPM方法较12导心电图能更有效地发现体表QT间期最大、最小值及心室复极的离散,尤其可展示QT间期的空间分布.     

急性心肌梗死心功能与QTd离散度相关性的探讨

目的:探讨急性心肌梗死患者心功能与QT高散度(QTd)的相关性。方法:对于18例伴有不程度心功能不全的急性心肌梗死患者,采用同步12导心电图测量其入院时,入院后第1、2周的QTd,并分析其与心功能的关系。结果:研究对象入院时心功能(Killip)为Ⅱ~Ⅲ级,QTd为87±18.62ms,入院后第1周的QTd为60.76±12.23ms,入院后第2周心功能为Ⅰ级,QTd为42.26±12.31ms;与入院时QTd比较,入院后第1、2周的QTd显著改善(P分别<0.01、<0.001);心功能与QTd呈负相关关系。结论:急性心肌梗死患者心功能与QT离散度呈负相关关系,心功能越差,QTd值越大。     

QT dispersion and early arrhythmic risk in acute myocardial infarction

BACKGROUND: This study sought to find out QT dispersion in healthy individuals and patients of acute myocardial infarction and to find correlation, if any, between QT dispersion and the incidence of ventricular arrhythmias in acute myocardial infarction. METHODS AND RESULTS: QT dispersion was calculated from a 12-lead electrocardiogram in 100 patients of acute myocardial infarction admitted in intensive coronary care unit and 100 age- and sex-matched healthy individuals. In patients of acute myocardial infarction, QT dispersion was calculated on admission, 24 hours after admission and at the time of discharge from intensive coronary care unit. Average QT dispersion in acute myocardial infarction was found to be significantly higher on admission (76.4 +/- 18.3 ms), 24 hours after admission (62.88 +/- 17.52 ms) and at the time of discharge from intensive coronary care unit (51.79 +/- 16.79 ms) than in healthy individuals (29.76 +/- 6.06 ms; p<0.05). QT dispersion was found to be significantly increased in patients of acute myocardial infarction with ventricular arrhythmias (82.06 +/- 16.86 ms) than in those without (66.75 +/- 16.28 ms; p<0.01). Patients of acute myocardial infarction with ventricular tachycardia or ventricular fibrillation had significantly increased QT dispersion (96.25 +/- 15.97 ms) than those who had only ventricular premature beats (80 +/- 15.04 ms; p<0.01). QT dispersion was found to be significantly greater in patients with anterior wall acute myocardial infarction (79.80 +/- 18.19 ms) than in those with inferior wall acute myocardial infarction (71.9 +/- 17.48 ms; p<0.05). At the time of discharge from intensive coronary care unit no statistically significant difference was found in QT dispersion in those who received thrombolysis (51.58 +/- 16.05 ms) and those who did not (48.18 +/- 14.68 ms; p>0.05). QT dispersion was found to be significantly higher in those who died (88.66 +/- 15.97 ms) than in those who survived (74.23 +/- 17.91 ms; p<0.05). QT dispersion was significantly higher in ventricular arrhythmic deaths (97.14 +/- 17.04 ms) than those who had non-arrhythmiac deaths (81.25 +/- 11.25 ms; p<0.05). CONCLUSIONS: Interlead QT variation and its measure as QT dispersion challenges our current approach to the electrocardiographic assessment of arrhythmic risk. QT dispersion may provide a potentially simple, cheap, non-invasive method of measuring underlying dispersion of ventricular excitability.     

Ramipril reduces QT dispersion in patients with acute myocardial infarction and heart failure

In a cohort of 67 patients from the Acute Infarction Ramipril Efficacy study, we showed that ramipril therapy was associated with a significant reduction in QT dispersion over a 2-month period after acute myocardial infarction. This reduction of ventricular repolarization inhomogeneity indicates an antiarrhythmic effect and may be an important additional mechanism for the reduced all-cause mortality and sudden death incidence achieved with angiotensin-converting enzyme inhibition after acute myocardial infarction.     

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.     

QT dispersion and early arrhythmic risk during acute myocardial infarction

BACKGROUND: QT dispersion (maximal minus minimal QT interval calculated on a standard 12-lead electrocardiogram) has been suggested to reflect regional variations of ventricular repolarization and to provide a substrate for reentry ventricular arrhythmias. In this study we evaluate QT dispersion in patients with acute myocardial infarction and assess its relation with early severe ventricular arrhythmias. METHODS AND RESULTS: We studied 101 patients with acute myocardial infarction and a control group of 97 healthy subjects. We determined QT and QTc dispersion on the electrocardiograms performed 12 hours and 3 and 10 days after the onset of symptoms in myocardial infarction patients and on the control group. The average values of QT and QTc dispersion (measured hereafter in milliseconds, ms) were as follows: 70.5 +/- 42.5-87 +/- 46.6 (after 12 hours), 66.5 +/- 37.8-76.9 +/- 43.5 (on day 3), 68.9 +/- 42-76.3 +/- 43.8 (on day 10) and 44 +/- 13.4-54.2 +/- 16.3 (in control group). We observed statistically significant differences in QT and QTc dispersion between the electrocardiogram of normal subjects and each of the three electrocardiograms performed on patients with infarction (p < 0.0005, p < 0.005). We recorded a greater QT dispersion in patients with anterior infarction with respect to those with inferior/lateral infarction (79 +/- 38.6 vs 65.2 +/- 43.16, p < 0.05) and in patients with ejection fraction < 45% (93.1 +/- 28.4 vs 68.3 +/- 34.1 p < 0.005). During the first three days, QT dispersion did not differ in patients treated with thrombolytic agents with respect to those who were untreated, while on day 10 untreated patients showed higher values (74.9 +/- 45.3 vs 60.5 +/- 37.7, p < 0.05). Creatine kinase peak level, sex and age of the patients did not influence QT dispersion. Thirteen patients (12.8%) developed severe ventricular arrhythmias within 72 hours after infarction: 8 patients (7.9%) had ventricular fibrillation and 5 patients (4.9%) had sustained ventricular tachycardia. We found higher early QT and QTc dispersion values in patients who developed severe ventricular arrhythmias (108.8 +/- 63.2 and 125.8 +/- 68.5) with respect to patients who did not (63.3 +/- 32.9 and 80.8 +/- 38.9, p < 0.0005, p < 0.0005). CONCLUSIONS: Our data suggest that QT dispersion: 1) increases during acute myocardial infarction; 2) peaks in the early hours after symptom onset; 3) drops late after infarction in patients treated with thrombolytic agents; 4) is associated with early severe ventricular arrhythmias.     

QT dispersion and early arrhythmic risk during acute myocardial infarction

It has been suggested that QT dispersion (maximal minus minimal QT interval calculated on a standard 12-lead electrocardiogram) could reflect regional variations of ventricular repolarization and could provide a substrate for reentry ventricular arrhythmias. The present study evaluates QT dispersion in patients with acute myocardial infarction, assessing its relation with early severe ventricular arrhythmias and some clinical features. Three hundred three patients with acute myocardial infarction and a control group of 297 healthy subjects were studied. QT and QTc dispersion were determined on the electrocardiogram taken after 12 hours and on days 3 and 10 after symptoms onset and on the electrocardiogram taken in the control group. The average values of QT and QTc dispersions (ms) were as follows: 70.5 +/- 42.5-87 +/- 45.6 (12th hour), 66.7 +/- 37.6-76.8 +/- 43.6 (day 3), 68.8 +/- 42.7-76.8 +/- 42.8 (day 10), versus 43 +/- 13.2-53.9 +/- 16.2 (control group). There were statistically significant differences between QT and QTc dispersion recorded in normal subjects and in each of the three electrocardiograms taken in patients with infarction. A greater QT dispersion was recorded in patients with anterior infarction (78.9 +/- 38.5 vs 64.9 +/- 42.8 in inferior/lateral infarction). In the first 3 days QT dispersion was not different in patients treated and untreated with thrombolysis, whereas on day 10 it was greater in untreated patients (74.9 +/- 45.3 vs 60.5 +/- 37.2). Creatine kinase peak level did not influence QT dispersion. In the first 72 hours of infarction, 37 patients developed ventricular fibrillation or sustained ventricular tachycardia. Higher early values of QT and QTc dispersion were found in patients who developed severe ventricular arrhythmias (107.8 +/- 62 and 124.8 +/- 67.5 ms) than in patients without serious arrhythmias (62.9 +/- 32.2 and 80.1 +/- 37.9 ms). These data suggest that: (1) QT dispersion increased during acute myocardial infarction. (2) The values were higher in the early hours and fell late after infarction with thrombolysis. (3) Greater QT dispersion is associated with severe ventricular arrhythmias.     

急性心肌梗死患者溶栓治疗前后QT离散度变化及临床意义

目的探讨急性心肌梗死(AMI)患者尤其溶栓前后QT离散度(QTd)的变化及临床意义.方法电脑心电图采样,测定56例AMI患者与54例健康者体表心电图的QTd,心率校正QT离散度(QTcd)和改良心率校正QT离散度(QTLcd).结果(1)AMI组QTd各项指标显著延长(P<0.01),经溶栓治疗后显著缩短(P<0.01).(2)32例AMI患者经静脉溶栓再通后,QTd指标显著缩短(P<0.01).(3)AMI患者QTd>60ms者,心脏事件的发生率和病死率均显著升高(P<0.01).结论QTd是无创测量AMI后恢复程度的有效指标之一,可用于协助判断溶栓的疗效及患者的预后有所帮助.     

急性心肌梗塞患者静脉溶栓治疗前后QT离散度变化分析

目的探讨急性心肌梗塞（ＡＭＩ）患者静脉溶栓治疗前后ＱＴ间期离散度（ＱＴｄ）变化及对预后的影响。方法１５３例ＡＭＩ患者分为溶栓再通组,未通组及非溶栓组,测定其溶栓前后的ＱＴｄ,并与非溶栓组ＱＴｄ比较。结果溶栓治疗再通后ＱＴｄ明显减小,而未通组及非溶栓组ＱＴｄ增大,且后两组间ＱＴｄ比较差异无显著性（Ｐ＞０．０５）。ＱＴｄ增大者发生室性快速心律失常比率增大。结论ＡＭＩ患者ＱＴｄ明显增大,但静脉溶栓再通后,随心肌缺血改善,ＱＴｄ明显减小,同时室性快速心律失常发生率降低。