Circadian Pattern of QT/RR Adaptation in Patients with and Without Sudden Cardiac Death after Myocardial Infarction

Background: Abnormalities in the adaptation of the QT interval to changes in the RR interval may facilitate the development of ventricular arrhythmias. Methods: This study sought to evaluate the dynamic relation between the QT and RR intervals in patients after acute myocardial infarction. The study population consisted of 14 patients after myocardial infarction (age 60 ± 7 years, 12 men) who died suddenly (SCD victims) within 1 year after the myocardial infarction and 14 pair-matched age, sex, left ventricular ejection fraction, infarct site, thrombolytic therapy) patients who remained event-free after myocardial infarction (Ml survivors) for at least 3 years. Fourteen normal subjects were studied as controls (age 55 ± 9 years, 11 men). QT and RR intervals were measured on a beat-to-beat basis automatically with a visual control from 24-hour ambulatory ECGs using Reynolds Pathfinder 700. Mean hourly values of the QT/RR slope (QT =α+βRR) and corrected QT interval at 1000 ms of RR interval (QT_1s) were derived for each subject using an inhouse program (QT_1s=α+1000β). The dynamics of the QT/RR slope and QT_1s were assessed on the basis of hourly mean values. The circadian rhythm of ventricular repolarization (QT_1s and QT/RR slope) was examined by harmonic regression analysis. Results: There was a trend towards a significant difference in 24-hour mean value of QT_1s between study groups (408 ± 26 ms vs 381 ± 43 ms and 386 ± 22 ms, P = 0.06), and a significant difference was found between SCD victims and normal subjects (408 ± 26 vs 386 ± 22 ms, P = 0.02). The QT_1s differed significantly between study groups (P = 0.038) only during the day time (09:00–19:00 hour), when QT_1s was significantly longer in SCD victims than in normal subjects (409 ± 33 vs 380 ± 27 ms, P = 0.02) and tended to be longer than in Ml survivors (409 ± 33 vs 379 ± 42 ms, P = 0.08). The 24-hour mean value of QT/RR slope was significantly different between study groups (P = 0.04), with a significantly steeper slope in SCD victims than in normal subjects (0.15 ± 0.07 vs 0.09 ± 0.02, P = 0.008). During day time, the QT/RR slope differed significantly between study groups (P = 0.04), while the difference was less marked at night (P = 0.08). The slope was significantly steeper in SCD victims than in normal subjects during both day and night (P < 0.05). A marked circadian variation of QT_1s was observed in normal subjects, which was blunted in Ml survivors and SCD victims. Conclusions: Abnormal repolarization behaviors, characterized by longer QT_1s and impaired adaptation of QT to variations in RR intervals, were found in SCD victims. Hence, lethal ventricular tachyarrhythmias might be provoked by the altered repolarization dynamics in patients after myocardial infarction. A.N.E. 1999;4(3):286–294     

Interobserver Reproducibility of QT Interval Measurement and QT Dispersion in Patients After Acute Myocardial Infarction

Background: The study evaluated interobserver differences in the classification of the T-U wave repolarization pattern, and their influence on the numerical values of manual measurements of QT interval duration and dispersion in standard predischarge 12-lead ECGs recorded in survivors after acute myocardial infarction. Methods: Thirty ECGs recorded at 25 mm/s were measured by six independent observers. The observers used an adopted scheme to classify the repolarization pattern into 1 of 7 categories, based on the appearance of the T wave, and/or the presence of the U wave, and the various extent of fusion between these. In each lead with measurable QRST(U) pattern, the RR, QJ, QT-end, QT-nadir (i.e., interval between Q onset and the nadir or transition between T and U wave) and QU interval were measured, when applicable. Based on these measurements, the mean RR interval, the maximum, minimum, and mean QJ interval, QT-end and/or QT-nadir interval, and QU interval, the difference between the maximum and minimum QT interval (QT dispersion [QTD]), and the coefficient of variation of QT intervals was derived for each recording. The agreement of an individual observer with other observers in the selection of a given repolarization pattern were investigated by an agreement index, and the general reproducibility of repolarization pattern classification was evaluated by the reproducibility index. The interobserver agreement of numerical measurements was assessed by relative errors. To assess the general interobserver reproducibility of a given numerical measurement, the coefficient of variance of the values provided by all observers was computed for each ECG. Statistical comparison of these coefficients was performed using a standard sign test. Results: The results demonstrated the existence of remarkable differences in the selection of classification patterns of repolarization among the observers. More importantly, these differences were mainly related to the presence of more complex patterns of repolarization and contributed to poor interobserver reproducibility of QTD parameters in all 12 leads and in the precordial leads (relative error of 31%–35% and 34%–43%, respectively) as compared with the interobserver reproducibility of both QT and QU interval duration measurements (relative error of 3%–6%, P < 0.01). This observation was not explained by differences in the numerical order between QT interval duration and QTD, as the reproducibility of the QJ interval (i.e., interval of the same numerical order as QTD was significantly better (relative error of 7.5%–13%, P < 0.01) than that of QTD. Conclusions: Poor interobserver reproducibility of QT dispersion related to the presence of complex repolarization patterns may explain, to some extent, a spectrum of QT dispersion values reported in different clinical studies and may limit the clinical utility in this parameter.     

QT Interval and Long‐Term Mortality Risk in the Framingham Heart Study

Background : The association between QT interval and mortality has been demonstrated in large, prospective population‐based studies, but the strength of the association varies considerably based on the method of heart rate correction. We examined the QT‐mortality relationship in the Framingham Heart Study (FHS). Methods : Participants in the first (original cohort, n = 2,365) and second generation (offspring cohort, n = 4,530) cohorts were included in this study with a mean follow up of 27.5 years. QT interval measurements were obtained manually using a reproducible digital caliper technique. Results : Using Cox proportional hazards regression adjusting for age and sex, a 20 millisecond increase in QTc (using Bazett's correction; QT/RR^1/2 interval) was associated with a modest increase in risk of all‐cause mortality (HR 1.14, 95% CI 1.10–1.18, P < 0.0001), coronary heart disease (CHD) mortality (HR 1.15, 95% CI 1.05–1.26, P = 0.003), and sudden cardiac death (SCD, HR 1.19, 95% CI 1.03–1.37, P = 0.02). However, adjustment for heart rate using RR interval in linear regression attenuated this association. The association of QT interval with all‐cause mortality persisted after adjustment for cardiovascular risk factors, but associations with CHD mortality and SCD were no longer significant. Conclusion : In FHS, there is evidence of a graded relation between QTc and all‐cause mortality, CHD death, and SCD; however, this association is attenuated by adjustment for RR interval. These data confirm that using Bazett's heart rate correction, QTc, overestimates the association with mortality. An association with all‐cause mortality persists despite a more complete adjustment for heart rate and known cardiovascular risk factors.     

A Study of the Association between the Prolongation of the QT Interval in the Resting ECG and Myocardial Infarction

ABSTRACT The relationship between the incidence of myocardial infarction in the 10 year follow-up period and the length of the QT interval and its two components (the time elapsing between the Q wave and the beginning of the T wave, and the duration of the T wave) was investigated in a study of the records of a group of men drawn from a random sample of all 55-year-old men living in Göteborg, Sweden. A significant association was found between the incidence of myocardial infarction and the first component but not with the second component or the QT interval itself. The two components were found to be independent and thus to have the potential to act as confounding factors if the QT interval is examined alone. Further, our results suggest that correcting the QT interval for heart rate needs careful reassessment.     

Continuous QT Interval Measurements from 24-Hour Electrocardiography and Risk after Myocardial Infarction

Objectives: The aim of this study was to examine the clinical value of QT analysis from Holter recordings in patients after myocardial infarction (Ml). Background: Prolongation and dispersion of QT intervals in the 12-lead standard ECG have been proposed as indicators of risk for arrhythmic events. However, the value of QT and T wave measurements from Holter recordings has yet to be established. Methods: Intervals from Q to the peak and to the end of T were determined every 30 seconds from 24-hour Holter recordings and corrected for cycle length (QTc). The duration of late repolarization was calculated as QT end minus QT peak. 24-hour QT variability was determined as the standard error of estimate from the linear regression analysis of QT and RR intervals. In a case control design, 51 post-MI patients suffering from subsequent cardiac death within 1 year were compared to 51 post-MI patients with an uncomplicated follow-up. Results: QTc intervals as well as 24-hour QT variability did not differ between post-MI patients with favorable and unfavorable clinical outcome. However, there was a prolonged interval from the peak to the end of the T wave in cardiac death victims (mean ± SE: 110 ± 4 ms) as compared to controls (95 ± 3ms, P < 0.001). Conclusions: Prolongation of the late repolarization phase seems to be associated with an increased risk of cardiac death after Ml. Standard QT measurements from ambulatory ECG recordings have no predictive value in post-MI patients.     

QT dynamicity and sudden death after myocardial infarction: results of a long-term follow-up study

INTRODUCTION: The aim of this study was to determine whether impaired adaptation of the QT interval to changes in heart rate predicts sudden death after an acute myocardial infarction. METHODS AND RESULTS: The Groupe d'Etude du Pronostic de l'Infarctus du Myocarde (GREPI) trial was a prospective multicenter study designed to evaluate the long-term outcome of myocardial infarction. QT dynamicity was evaluated in 265 patients by analyzing 24-hour Holter recordings obtained 9 to 14 days after myocardial infarction. The linear regression slope of QT intervals measured to the apex and to the end of the T wave (QTe) plotted against RR intervals was calculated using a dedicated Holter algorithm. The value of QT/RR in predicting sudden death and total mortality was compared with those of ejection fraction, heart rate variability, and late potentials. Mean follow-up was 81 +/- 27 months. There were 73 deaths, of which 23 were sudden. Of all the parameters, an increased diurnal QTe/RR slope (>0.18) was the strongest independent predictor of sudden death (relative risk 6.07, confidence interval 1.48-24.95, P = 0.01). CONCLUSION: Increased diurnal QTe dynamicity is independently predictive of sudden death among patients with myocardial infarction. This simple parameter may help to stratify risk and select patients who may benefit from antiarrhythmic prophylaxis.     

The Measurement of the QT Interval

The evaluation of every electrocardiogram should also include an effort to interpret the QT interval to assess the risk of malignant arrhythmias and sudden death associated with an aberrant QT interval. The QT interval is measured from the beginning of the QRS complex to the end of the T-wave, and should be corrected for heart rate to enable comparison with reference values. However, the correct determination of the QT interval, and its value, appears to be a daunting task. Although computerized analysis and interpretation of the QT interval are widely available, these might well over- or underestimate the QT interval and may thus either result in unnecessary treatment or preclude appropriate measures to be taken. This is particularly evident with difficult T-wave morphologies and technically suboptimal ECGs. Similarly, also accurate manual assessment of the QT interval appears to be difficult for many physicians worldwide. In this review we delineate the history of the measurement of the QT interval, its underlying pathophysiological mechanisms and the current standards of the measurement of the QT interval, we provide a glimpse into the future and we discuss several issues troubling accurate measurement of the QT interval. These issues include the lead choice, U-waves, determination of the end of the T-wave, different heart rate correction formulas, arrhythmias and the definition of normal and aberrant QT intervals. Furthermore, we provide recommendations that may serve as guidance to address these complexities and which support accurate assessment of the QT interval and its interpretation.     

QT Interval in Patients with Unstable Angina and Non‐Q Wave Myocardial Infarction

Background: Non‐Q wave mvocardial infarction (NQMI) and unstable angina (UAP) have similar clinical presentations and similar ST‐T changes on the electrocardiogram. The purpose of this study was to assess whether changes in QT interval might help differentiating between these entities. Methods: The QT intervals of 52 patients hospitalized with NQMI were compared to those of 52 patients hospitalized for UAP. All patients had repeated ECG for at least 4 days. Results: Maximal QTc in patients with NQMI was significantly longer than in patients with UAP (475 vs 439 ms, P < 0.0001). QTc on the admission ECG was 450 ms in patients with NQMI compared to 417 ms in UAP P < 0.005). QTc > 460 ms was present in 48% patients with NQMI and in 19% of UAP patients. Maximal QT prolongation was observed within 36 hours of admission with return to normal within 96 hours. QT dispersion was within normal range, being longer in patients with NQMI than patients with UAP (55 vs 43 ms, P < 0.003). QT prolongation was not associated with increased frequency of arrhythmia. The cause of QT prolongation in NQMI may be related to the damage of subendocardial layer exposing the M cells layer which markedly prolong action potential duration. Conclusion: Transient QT prolongation is observed in about half of patients with NQMI. These ECG changes may help differentiating between patients with NQMI and UAP already on admission. A.N.E. 2002;7(4):343–348     

QT间期与风湿结缔组织疾病

风湿病中QT相关指标的延长是相当常见的,多与疾病本身的免疫和炎症相关,常常预示着复杂的室性心律失常和心源性猝死。因此,对于这些病人,行12导联心电图、24小时心电监测及心脏彩超检查是很有必要的。     

Four-year Incidence of Myocardial Infarction and Sudden Coronary Death in Twelve Finnish Population Cohorts

ABSTRACT. Suhonen O, Reunanen A, Aromaa A, Knekt P, PyÖrÄlÄ K. (Research Institute for Social Security, Social Insurance Institution, Helsinki, Finland.) Four-year incidence of myocardial infarction and sudden coronary death in twelve Finnish population cohorts. The incidence of myocardial infarction (MI) and sudden coronary death in four years was studied in 6510 men and 5800 women, aged 30–59 years, derived from 12 Finnish population cohorts constituting the invited population to a prospective study. The incidence of all fatal coronary events in four years was 13.0/1000 in men and 1.8/1000 in women. The incidence of sudden coronary death was 7.8/1000 in men and 0.7/1000 in women. The incidence of non-fatal MI was 22.2/1000 in men and 7.3/1000 in women. Coronary mortality was significantly higher in non-participants in the initial survey than in participants. The incidence of MI was highest in men from eastern Finland (North Karelia), intermediate in men from central and western Finland and lowest in men from southwestern Finland. There were no significant regional differences in the incidence of MI in women. The incidence of MI in this study was in good agreement with that recorded in the myocardial community registers.     

静息心电图对心肌梗死后猝死的预警意义

猝死是全球关注的健康问题,其中心脏性猝死是心肌梗死后患者死亡的重要原因。大部分心肌梗死后心脏性猝死的高危患者都可以通过普通检查发现,从而有效的预防。现通过对标准12导联心电图相关指标的分析,预测心肌梗死后患者的猝死风险,以提高临床诊治水平。     

Circadian Variation and Waking Hour Dynamics of the QT Interval

Background: The incidence of sudden cardiac death is maximal in the morning hours. Although ventricular arrhythmias have been implicated as a potential mechanism, and several neurohumoral factors affecting myocardial excitability have been shown to be raised in the early morning hours, it is not known if there is any circadian variation in the dynamics of ventricular repolarization when studied on a beat-to-beat basis. The objective of this study was to examine the range, diurnal variations, and circadian distribution of the variability of the QT interval in healthy subjects. Method: We developed and validated a new method for continuous measurement of QT intervals from 24-hour Holter recordings. The QT intervals measured semi-automatically were corrected by a linear regression formula derived independently for each patient from his own QT and RR values in 32 healthy males (20 ± 0.4 years). QT variability was assessed by the mean standard deviation of the average of consecutive uncorrected QT intervals (SDA-QT Index) and corrected QT intervals (SDA-QTc index) over 5-minute segments. The rate-dependent changes of the QT interval were studied as a function of the slope of the regression line between the QT and RR values. Results: The average QTc range was mean (SD) 79 (± 28) ms; the average maximal QTc interval was 481 (± 24) ms. The 95% upper confidence limit for the mean 24-hour QTc interval was 443 ms. The RR, QT, and QTc intervals were longer, while the SDA-QT and SDA-QTc indices were shorter during sleep. Hourly averages of the SDA-QT and SDA- QTc index revealed a sudden increase in QT variability in the first hour of waking (P < 0.0001 and P = 0.006). Conclusion: The dynamic behavior of the QT interval shows significant diurnal variations. The maximal QTc interval over 24 hours is longer than previously assumed. The period shortly following awakening is characterized by a peak in the variability of the QT interval. These changes may be indicative of autonomic instability during the early waking hours and correspond with the peak incidence of sudden arrhythmic death.     

Beat-to-Beat Repolarization Lability Identifies Patients at Risk for Sudden Cardiac Death

QT Interval Variability and Sudden Death. Introduction : Recent studies have implicated repolarization lability in the genesis of malignant ventricular arrhythmias. However, few data exist on assessment of temporal QT interval variability and its relation to arrhythmogenesis. We tested the ability of the QT variability index (QTVI), a measure of beat-to-beat QT interval fluctuations measured on a single ECG lead, to identify patients presenting with malignant ventricular arrhythmias and predict their subsequent occurrences.
Methods and Results : We measured the QTVI in 95 patients presenting for electrophysiologic study (EPS). The ability of the QTVI to identify patients with sudden cardiac death (SCD) or sustained monomorphic ventricular tachycardia (MVT) on presentation and during follow-up of 23.7 ± 14.3 months was compared with spatial QT dispersion, T wave alternans ratio during atrial pacing, MVT inducibility at EPS, signal-averaged ECG, heart rate variability, and ejection fraction. The QTVI was higher in patients with heart disease than in controls (-0.7 ± 0.7 vs −1.1 ± 0.5, P < 0.05), and higher in patients presenting with SCD than in other patients with heart disease (0.0 ± 0.6 vs −0.8 ± 0.5, P < 0.05). The QTVI was the only clinical variable that identified patients who presented with SCD ( P = 0.004, odds ratio = 12.5) on stepwise, logistic multiple regression. Fourteen patients had arrhythmic events during follow-up. In a Kaplan-Meier analysis of arrhythmic events, QTVI ≥ 0.1 was a discriminator for higher risk of arrhythmic events ( P < 0.05).
Conclusions : (1) This noninvasive measure of temporal repolarization lability identified patients with SCD and predicted arrhythmia-free survival. (2) Further studies are needed to determine the mechanisms that mediate beat-to-beat QT interval variability.     

溶栓治疗对急性心肌梗塞患者QTc间期的影响

为探讨溶栓治疗对急性心肌梗塞（ＡＭＩ）患者ＱＴｃ间期的影响，将７０例ＡＭＩ患者随机分为溶栓组（３２例）和未溶栓组（３８例）。两组病人发病后ＱＴｃ间期平均值均延长，两者比较无显著性差异（４５８±５２ｍｓｖｓ４７１±６０ｍｓ，Ｐ＞０．０５）。溶栓后１和３日ＱＴｃ间期明显延长，与未溶栓组入院后１和３日ＱＴｃ间期比较存在显著性差异（分别为４８８±５１ｍｓｖｓ４５５±５２ｍｓ，４８０±５４ｍｓｖｓ４５５±４４ｍｓ，Ｐ均＜０．０５），这种变化可能与溶栓后的缺血再灌注损伤有关。入院后７日两组ＱＴｃ间期比较无统计学差异（４４６±５６ｍｓｖｓ４５２±４１ｍｓ，Ｐ＞０．０５）。溶栓组入院后第１，３，７日与入院时ＱＴｃ间期平均值之差值分别为－（２９±１０），－（６±９），１０±８ｍｓ，未溶栓组则为１６±８，９±１０，１９±９ｍｓ，两组比较有显著性差异（Ｐ＜０．０５或＜０．０１）。因此比较ＱＴｃ间期缩短的速度比单纯比较ＱＴｃ间期对于判定溶栓治疗的疗效可能更有意义     

QT Dispersion as a Noninvasive Arrhythmiogenic Marker in Acute Myocardial Infarction

Backround: Prolongation of QT dispersion (QTD), defined as the difference between maximum and minimum QT intervals on surface ECG, has been proposed as a noninvasive arrythmogenic marker. The aim of this study was to estimate the value of QTD in identifing patients susceptible to ventricular fibrillation or ventricular tachycardia (VF/VT) after an acute myocardial infarction (AMI) and to evaluate the behavior of QTD in relation to the thrombolytic therapy. Methods: We studied 108 consecutive patients with AMI. All patients had a 12-lead surface ECG recorded upon admission and a second ECG 24 hours later. QT interval was measured from the onset of Q to the end of T in each of 12 standard ECG leads. QTD was the difference between the longest and shortest values of QT. All QTD measurements were corrected for heart rate (QTcD) using QTc values according to Bazzet formula. Results: Fifteen patients (13.8%) developed VF/VT in the first week after AMI (group 1A) and 93 patients (86.2%) did not have VF/NT (group 1B). QTD and QTcD values were significantly greater in group 1A in comparison to group 1B on admission and 24 hours later. Sixty-five patients (60%) received intravenous thrombolysis in the acute phase of AMI (group 2A) and 43 patients (40%) did not (group 2B). No significant difference in QTD and QTcD was observed in the first ECG on admission between the two groups. Conversely, QTD and QTcD were lower in group 2A patients in the second ECG 24 hours after admission. Conclusions: These results provide evidence that increased values of QTD are correlated well with occurrence of malignant ventricular arrhythmias after acute myocardial infarction while lower values associated with the thrombolytic therapy. A.N.E. 1999;4(1):35–38     

The Mid-term Mortality and Mode of Death in Survivors with ST-elevation Myocardial Infarction

Objective The popularity of primary percutaneous coronary intervention (p-PCI) for ST-elevation myocardial infarction (STEMI) has increased over the past decades. Despite improvements in in-hospital mortality rates, it is clinically important to investigate the prognoses after discharge. However, data on the mode of death and prognostic factors are limited. We analyzed these factors in a Japanese cohort in the modern p-PCI era. Methods Between January 2004 and December 2017, a total of 1,222 patients who underwent p-PCI within 24 hours from the onset of STEMI and were alive at discharge (mean age, 67.7 years old; men, 75.5%), were evaluated. The two-year mortality was analyzed using a Cox regression model, and the mode of death was evaluated. Results The rate of mortality at 2 years was 5.7%. Non-cardiac death was more frequent than cardiac death (62.6% vs. 37.4%). A Cox multivariate analysis identified the following as independent predictors of the 2-year mortality: hemoglobin (log-transformed) [adjusted hazard ratio (HR), 0.048; 95% confidence interval (CI), 0.008-0.29; p<0.001], age above 80 years old (adjusted HR, 2.26; 95% CI, 1.30-3.91; p=0.004), Killip class ≥II (adjusted HR, 1.99; 95% CI, 1.17-3.39; p=0.011), brain natriuretic peptide level (log-transformed) (adjusted HR, 1.47; 95% CI, 1.09-2.01; p=0.013), and body mass index (log-transformed) (adjusted HR, 0.16; 95% CI, 0.030-0.84; p=0.030). Conclusion This study demonstrated that the 2-year mortality was 5.7% in STEMI survivors after p-PCI. Non-cardiac death was more frequent than cardiac death. Compared to well-known clinical variables, angiographic findings did not have a significant influence on the mid-term mortality.     

The Prognostic Accuracy of Different QT Interval Measures

Background: The QT intervals accuracy for predicting arrhvthmic death varies between studies, possibly due to differences in the selection of the lead used for measurement of the QT interval. The purpose of this study was to analyze the prognostic accuracy of all known ways to select the lead. Methods and Results: Three institutions that used different methods for measuring QT intervals provided their QT databases. They included more than 3500 twelve‐lead surface ECGs. The data represented low‐ and high‐risk patients of the normal population (survivors vs dead from cardiovascular causes), acute myocardial infarction (survivors versus death from all causes) and remote myocardial infarction (with vs without a history of ventricular arrhythmia). The prognostic accuracy was defined as the area under the Receiver Operator Curve (ROC‐area). The most accurate standard leads were I and aVL and the least accurate was AVR. The most accurate precordial lead was V₄. The prognostic accuracy of the longest QT interval was higher than for any standard lead. The prognostic accuracv of the mean of the three longest QT intervals was equal to or slightly lower than for the longest QT interval. Conclusions: The highest prognostic accuracy is obtained with the longest QT interval. The accuracies of the lead selection methods are so different that it can explain a substantial part of the differences between otherwise similar studies in the literature. We recommend the use of the mean value of the three longest QT intervals. A.N.E. 2002;7(1):10–16     

Correlation Between Beat‐to‐Beat QT Interval Variability and Impaired Left Ventricular Function in Patients with Previous Myocardial Infarction

Background: Beat‐to‐beat QT interval variability (QTV) is associated with sudden cardiac death and New York Heat Association functional class severity. We sought to evaluate the relationship between QTV and left ventricular (LV) function in patients with previous myocardial infarction (MI). Methods: Fifty‐nine patients with previous anterior MI were enrolled. LV ejection fraction (EF), LV end‐systolic volume index (LVESVI), and LV end‐diastolic volume index (LVEDVI) were measured by LV contrast angiography. QT interval was measured by automated analysis of 512‐beat records of 12‐lead electrocardiogram. The mean interval, standard deviation and variance in RR and QT intervals, and the QT variability index (QTVI) were calculated for each patient using two leads that corresponded with and without the infarction site. High‐frequency power, low‐frequency power, total‐frequency power, and the ratio of low‐frequency to high‐frequency power in RR and QT intervals were calculated. Results: While measured indices of RR intervals and indices of QT intervals, which did not correspond with the infarction site, did not correlate with differences in LV function, measured indices of QT intervals, which corresponded with the infarction site, did correlate with differences in LV function. However, there were no correlations between the ratio of low‐frequency to high‐frequency power in QT intervals and EF or LVEDVI. Correlations between QTVI and LV function were observed, particularly between QTVI and LVESVI (r = 0.712, P < 0.0001). Conclusion: In patients with previous anterior MI, there was variability in temporal dispersion of QT interval and a strong correlation between QTV corresponded with the infarcted site and LV function.