Prediction of sudden cardiac death in patients after acute myocardial infarction using T-wave alternans: a prospective study

Background and PurposeWe assessed the value of T-wave alternans (TWA) in prediction of sudden cardiac death (SCD) in patients with acute myocardial infarction (AMI).MethodsConsecutive patients (N = 227) were enrolled and were monitored with 24-hour ambulatory electrocardiogram within 1 to 15 days after AMI. T-wave alternans was identified by a modified moving average (MMA) algorithm computer software. The primary end point was SCD or lethal ventricular arrhythmia. We analyzed the hazard ratios (HRs) using the previously determined 47 μV TWA cutpoint.ResultsDuring the 16 ± 7-month follow-up, 10 (4.4%) patients died suddenly. T-wave alternans (≥47 μV) predicted SCD (HR, 17.78 [95% confidence interval, 3.75-84.31]; P < .0001). Moreover, patients with 5 or more TWA episodes (≥47 μV) were at higher risk for SCD (HR, 20.75 [95% confidence interval, 5.77-74.57]; P < .0001).ConclusionsT-wave alternans (≥47 μV) monitored at 1 to 15 days after AMI-predicted heightened risk of SCD. Prediction is improved when the frequency of TWA episodes (≥47 μV) is analyzed.     

微伏级T波电交替及窦性心律震荡对心肌梗死后患者猝死的预测价值

目的评价窦性心律震荡(HRT)和微伏级T波电交替(mTWA)对心肌梗死(简称心梗)后患者猝死的预测价值。方法入选心梗后患者212例,根据24h动态心电图记录,计算HRT的两个参数震荡初始(TO)和震荡斜率(TS),同时检测mTWA;随访2年,主要终点为心源性猝死(SCD),次要终点为全因死亡率,心血管疾病相关死亡,比较死亡组与存活组,死亡各亚组(SCD组及非SCD组)之间HRT及mTWA。结果 1死亡组中慢性肾病、心功能IV及胺碘酮使用率增多;SCD亚组左室射血分数(LVEF)下降更明显。2死亡组mTWA及HRT2明显升高。其中SCD亚组mTWAmax和HRT2异常较非SCD组明显升高。3LVEF、HRT、mTWA(06∶00AM)为最有意义的独立致死因子;LVEF、HRT、mTWA(100次/分)和室性早搏数量为SCD的危险因素。4异常TO/TS联合mTWA(100次/分)大于58.5mcV则显著增加全因死亡率[RR,32.5(95%CI 4.2~188.5),P0.001]及SCD风险[RR,60.5(95%CI 6.2~508.5),P0.001]。结论当患者HRT和mTWA异常时总死亡率及SCD风险明显增加。     

Utility of microvolt T-wave alternans to predict sudden cardiac death in patients with cardiomyopathy

PURPOSE OF REVIEW: Sudden cardiac death remains a major cause of mortality among patients with cardiomyopathy and implantable cardioverter-defibrillator therapy has been shown to improve survival in these patients. Effective use of prophylactic implantable cardioverter-defibrillator therapy requires accurate risk stratification beyond assessment of ejection fraction, however. Repolarization alternans is a harbinger of ventricular arrhythmias and its measurement from body-surface recordings, also known as microvolt T-wave alternans, is emerging as an effective prognostic tool in these patients based on recent clinical trials. RECENT FINDINGS: We review the pathogenesis and determinants of repolarization alternans. The current techniques for measuring T-wave alternans from the body surface are compared, including the spectral and modified moving average methods. Recent clinical trials evaluating the prognostic utility of T-wave alternans in patients with ischemic and nonischemic cardiomyopathy and no prior arrhythmic events are summarized. The findings of these studies are discussed in the context of implantable cardioverter-defibrillator prophylaxis. Body-surface T-wave alternans is an evolving technique and its limitations are presented along with approaches to improve its predictive accuracy. SUMMARY: Risk stratification with T-wave alternans has the potential to guide prophylactic implantable cardioverter-defibrillator therapy in a growing population of patients with cardiomyopathy.     

微伏极T波电交替对心肌梗死急性期患者发生恶性心律失常的预测价值

目的评估微伏极T波电交替（MTWA）能否预测急性心肌梗死早期患者恶性心律失常的发生。方法起病7d内的急性ST段抬高型心肌梗死患者175例入选,根据起病12h内有无行直接经皮冠脉介入治疗（PCI）分为两亚组：Ia组（n=68行直接PCI）,Ib组（n=107未行直接PCI）。另选无心肌梗死来我院健康体检者82例作为对照组。所有入选者均做动态心电图用时域分析法检测MTWA最大值,用超声心动图检测左心室射血分数（LVEF）,用心室晚电位分析仪检测心室晚电位,观察住院期间有无恶性心律失常发生,并比较上述这些指标组间有无差异,用Logistic回归分析筛选恶性心律失常的预测因子。结果心肌梗死组合并糖尿病者高于对照组,Ib组合并糖尿病者高于Ia组。急性心肌梗死组恶性心律失常发生率、心室晚电位阳性率和MTWA最高值均高于对照组,而LVEF值低于对照组。急性心肌梗死两亚组间比较,Ib组恶性心律失常发生率、心室晚电位阳性率和MTWA最大值均高于Ia组,而LVEF值低于Ia组。Logistic回归分析结果显示MTWA最大值、LVEF、心室晚电位阳性率和有无糖尿病是患者是否发生恶性心律失常的独立预测因子,相关系数R分别为0．34、0．29、0．21、0．13,相对危险度（OR）分别为2．82、1．55、1．36、0．87,MTWA的相关性最强（R=0．34）,相对危险度最高（OR=2．82）。当LVEF和心室晚电位进入回归方程时,决定系数R^20．448,增加MTWA最大值进入回归方程后,决定系数R^2显著增加至0．628。结论MTWA最大值、LVEF和心室晚电位是早期急性心肌梗死患者恶性心律失常发生的预测因子,MTWA的预测价值优于LVEF和心室晚电位。如果三者联合运用能更好地预测早期急性心肌梗死患者恶性心律失常发生。     

微伏级T波电交替对心性猝死高危人群的预测价值

目的 探讨微伏级T波电交替(MTWA)对恶性室性心律失常(MVA)及心性猝死(SCD)的预测价值,探索时域法MTWA检测的正、异常值范围.方法 连续选取2002年1月至2007年10月到昆明医学院第一附属医院就诊或健康体检者545例(男285例,女260例,平均年龄52岁),其中105例健康受检者设为对照组,既往有室性心动过速、心室颤动发作史或确诊为器质性心脏病且左室射血分数(LVEF)≤45%的138例设为SCD高危组.两组均成功检测MTWA、LVEF、心率变异性、非持续性室速、QRS、QTc等指标并完成随访,动态随访比较组间死亡及死因、MVA、再次住院、晕厥等事件的发生情况及其与MTWA等观测指标的相关性.结果 时域法MTWA检测95%的正常参考值范围为MTWA<37μV.平均(12.0±1.3)个月的随访期内,对照组无心血管事件发生;高危组死亡11例中SCD 7例(MTWA阳性率分别为81.8%、85.7%),发生MVA的17例中MTWA阳性率88.2%,发生晕厥的9例中MTWA阳性率77.8%,随访期住院的21例中MTWA阳性率85.7%.多因素回归分析预测MVA的危险因素依次为MTWA阳性、LVEF≤35%、有心肺复苏史、有晕厥史.仅MTWA阳性与SCD显著相关.MTWA阳性、LVEF≤35%分别是预测MVA的独立指标(P<0.01).MTWA与LVEF≤35%联合预测MVA的敏感性91%、特异性66%、阳性预测价值27%、阴性预测价值98%,优于二者单独使用.41例埋藏式自动复律除颤器(ICD)患者,MTWA阳性率68.3%.随访中发生MVA并被ICD自动电除颤者的MTWA阳性率87.5%.结论 (1)国人时域法MTWA正常参考值为<37μV.(2)MTWA与LVEF一样对MVA有独立预测价值且其预测SCD的价值优于LVEF,二者联合可进一步提高预测价值.(3)MTWA阳性似可成为ICD置入的初筛指标之一.(4)时域法检测MTWA具有无创、简便、高效、易重复、经济等优点,有良好的推广应用前景.     

Predictive value of microvolt T-wave alternans in patients with left ventricular dysfunction.

OBJECTIVES: The purpose of this study was to prospectively evaluate the utility of microvolt T-wave alternans (TWA) in predicting arrhythmia-free survival and total mortality in patients with left ventricular (LV) dysfunction. BACKGROUND: Microvolt TWA has been proposed as a useful tool in identifying patients unlikely to benefit from prophylaxis with implantable cardioverter-defibrillator (ICD) prophylaxis. METHODS: We evaluated 286 patients with an LV ejection fraction 相似文献   

Predictive value of microvolt T-wave alternans for cardiac death or ventricular tachyarrhythmic events in ischemic and nonischemic cardiomyopathy patients: a meta-analysis

Background: Microvolt T‐wave alternans (MTWA) has been proposed as a predictor of the risk of ventricular tachyarrhythmias (VT) and sudden cardiac death (SCD). Aim of this study was to perform a systematic review of the literature and a meta‐analysis of MTWA in primary prevention patients with ischemic and nonischemic cardiomyopathy. Methods: The positive predictive value (PPV), negative predictive value (NPV), and relative risk (RR) of MTWA in predicting death, cardiac death, and SCD during follow‐up were reported. Results: Fifteen studies involving 5681 patients (mean age 62 years, mean ejection fraction 32%) were included. The summary PPV during the average 26‐month follow‐up was 14% (95% CI: 13–15); NPV was 95% (95% CI: 94–96), and the univariate RR was 2.35 (95% CI: 1.68–3.28). The predictive value of MTWA was similar in patients with ischemic and nonischemic cardiomyopathy. The average RR for SCD or VT events of an abnormal MTWA was 2.40, similar to that for cardiac death. When we grouped the studies together depending upon whether beta‐blockers were withheld prior to MTWA screening, the beta‐blockers group showed an RR of 5.88. By contrast, the group in which beta‐blocker therapy was withheld had an RR of 1.63. Conclusion: A positive MTWA determined an approximately 2.5‐fold higher risk of cardiac death and life‐threatening arrhythmia and showed a very high NPV both in ischemic and nonischemic patients. An abnormal MTWA test was associated with a 5‐fold increased risk for cardiac mortality in the low‐indeterminate group and about a 6‐fold increased risk in beta‐blockers group. Ann Noninvasive Electrocardiol 2011;16(4):388–402     

Prognostic value of diastolic dysfunction for sudden cardiac death of patients after myocardial infarction

We studied prognostic value of left ventricular (LV) diastolic dysfunction (DD) in relation to sudden cardiac death (SCD) after myocardial infarction (MI). We examined 603 patients in acute period of MI (including 551 with preserved LV systolic function and DD). Duration of follow-up was 1-7 years. According to data of Cox multifactorial regression analysis LVDD was not an independent prognostic factor. ut it increased SCD risk at the account of interrelationship with such predictors as ventricular rhythm disturbances, lowering of heart rate variability, and sensitivity of cardiochronotropic component of arterial baroreflex.     

T-wave alternans for risk stratification and prevention of sudden cardiac death

Despite considerable progress in the management of ischemic heart disease, a substantial proportion of patients continue to experience life-threatening arrhythmic events. The Multicenter Automatic Defibrillator Implantation Trial 2 has recently shown the superiority of implantable cardioverter defibrillators (ICDs) over conventional strategies to prevent sudden death in patients with reduced ejection fraction, but at the expense of potentially unnecessary ICD implantation in a large percentage of patients. T-wave alternans (TWA), which reflects alternation of cellular repolarization, results in a substantial increase in dispersion of repolarization, a prerequisite for reentrant arrhythmias. Recent trials, cumulating close to 3000 patients, have established TWA analysis as a powerful tool for arrhythmia prevention. Based on the most recent estimates, at least one third of post-myocardial infarction patients are expected to be tested negative. With a negative predictive value greater than 90%, TWA might allow for targeting of patients most likely to benefit from ICD therapy. Accurate identification of high-risk patients by noninvasive TWA may allow for improved widespread screening for sudden death prevention in the general population.     

T-wave alternans: marker,mechanism, and methodology for predicting sudden cardiac death

Sudden cardiac death (SCD) is a leading cause of cardiovascular mortality. Therefore, identifying patients at highest risk for SCD is crucial. Conventional noninvasive markers of SCD are inadequate because of low positive predictive value. The presence of visible T-wave alternans (TWA) on electrocardiogram often predicts the occurrence of lethal ventricular arrhythmias. Signal processing methods have made it possible to detect microvolt-level and visually inapparent TWA on electrocardiogram. TWA is caused by underlying regional inhomogeneities of ventricular repolarization, which predispose patients to have ventricular arrhythmias. Microvolt TWA provoked either by atrial pacing, pharmacological stress, or exercise is a promising marker of arrhythmia vulnerability. Several large trials have shown TWA to be comparable or superior to other noninvasive markers and electrophysiologic study in the prediction of SCD. The patient populations in these trials include post myocardial infarction, both ischemic and nonischemic heart failure, and suspected arrhythmias. Prospective trials regarding benefits of implantation of cardioverter-defibrillator therapy based on TWA results are ongoing.     

Prediction of sudden death in patients discharged after acute myocardial infarction.

A follow-up was made of 475 patients discharged after an acute myocardial infarction. Sudden death, i.e. death within 2 hours after the onset of the final attack, was more common in patients below 60 years on admission than in the older age groups. Patients succumbing suddenly often had a history of an earlier myocardial infarction. They also had a higher incidence of inferior infarcts and more frequently showed ventricular tachycardia during the early hospital period than those dying more than 24 hours after the onset of the final episode. When comparisons were made with all patients dying after more than 2 hours' duration of the terminal attack no significant differences were noted for these or other parameters. Prediction of sudden death in immediate survivors of acute myocardial infarction thus seems elusive. Further studies of the relations between the incidence of ventricular ectopic activity during the early and late hospital phase of acute myocardial infarction and sudden death after discharge from hospital are implicated.     

KCNJ11 polymorphisms and sudden cardiac death in patients with acute myocardial infarction

PURPOSE: Patients with an acute myocardial infarction (AMI) are of high risk to develop ischemia-induced ventricular arrhythmias, leading to sudden cardiac death (SCD) in about one third of all AMI patients. The individual susceptibility to ischemia-induced arrhythmias may be modified by polymorphisms in genes encoding ion channels. The cardiac ATP-dependent potassium channel (K(ATP)) current is generated by ion channels encoded by the KCNJ11 gene and the SUR2a gene. Opening of the K(ATP) channel during ischemia results in action potential shortening in various studies and may therefore influence the outcome of AMI patients. METHODS: Using a three-primer strategy, we sequenced the complete coding and adjacent 5' and 3' sequences of the intronless KCNJ11 gene (1.3 kb) prospectively in two groups. Patients of group 1 (n = 84) survived three or more transmyocardial infarctions without developing any ventricular arrhythmias. Patients of group 2 died suddenly from their first myocardial infarction (n = 86), most of them witnessed SCDs. RESULTS: We identified a total of six known polymorphisms (K23E, A190A, L267V, L270V, I337V, and K281K) and two new polymorphisms (L267L, 3'UTR +62 G/A). The allele, genotype, and haplotype frequencies did not differ between the two groups. All polymorphisms were found to be in Hardy-Weinberg equilibrium. In addition, we identified two novel missense mutations in a highly conserved region of the gene in two patients of group 2 (P266T and R371H) with yet unknown functional consequences. CONCLUSION: In this study of AMI patients, SCD was not related to polymorphisms in the KCNJ11 gene.     

Usefulness of microvolt T-wave alternans for prediction of ventricular tachyarrhythmic events in patients with dilated cardiomyopathy: results from a prospective observational study

OBJECTIVES: This study was designed to evaluate the ability of microvolt-level T-wave alternans (MTWA) to identify prospectively patients with idiopathic dilated cardiomyopathy (DCM) at risk of ventricular tachyarrhythmic events and to compare its predictive accuracy with that of conventional risk stratifiers. BACKGROUND: Patients with DCM are at increased risk of sudden death from ventricular tachyarrhythmias. At present, there are no established methods of assessing this risk. METHODS: A total of 137 patients with DCM underwent risk stratification through assessment of MTWA, left ventricular ejection fraction, baroreflex sensitivity (BRS), heart rate variability, presence of nonsustained ventricular tachycardia (VT), signal-averaged electrocardiogram, and presence of intraventricular conduction defect. The study end point was either sudden death, resuscitated ventricular fibrillation, or documented hemodynamically unstable VT. RESULTS: During an average follow-up of 14 +/- 6 months, MTWA and BRS were significant univariate predictors of ventricular tachyarrhythmic events (p < 0.035 and p < 0.015, respectively). Multivariate Cox regression analysis revealed that only MTWA was a significant predictor. CONCLUSIONS: Microvolt-level T-wave alternans is a powerful independent predictor of ventricular tachyarrhythmic events in patients with DCM.