Determinant of microvolt-level T-wave alternans in patients with dilated cardiomyopathy.

OBJECTIVES: The aim of this study was to clarify the clinical significance and the determinant of microvolt-level T-wave alternans (TWA) in patients with dilated cardiomyopathy (DCM). BACKGROUND: The prevention of sudden death in patients with DCM remains the therapeutic target. T-wave alternans has been proposed as a powerful tool for identification of patients at high risk for ventricular arrhythmias and sudden death in coronary artery disease. METHODS: In 58 DCM patients, TWA was measured during bicycle exercise testing using a CH 2000 system (Cambridge Heart, Bedford, Massachusetts). The New York Heart Association class, signal-averaged electrocardiogram, QT dispersion, left ventricular end-diastolic diameter (LVDd) and percent fractional shortening detected by echocardiogram and the grade of the ventricular arrhythmia were obtained in all patients. RESULTS: T-wave alternans was positive in 23 patients (TWA+ group), negative in 25 (TWA- group) and indeterminate in 10. Univariate analysis showed that the percentage of patients with ventricular tachycardia (VT) and the LVDd in the TWA+ group was significantly higher than those in the TWA- group (61% vs. 8%, p < 0.001 and 65 +/- 11 mm vs. 58 +/- 8 mm, p < 0.05, respectively). The sensitivity, specificity and predictive accuracy of TWA for VT were 88%, 72% and 77%, respectively. Multivariate analysis showed that the presence of VT was a major independent determinant of TWA in patients with DCM (p = 0.003). CONCLUSIONS: T-wave alternans was closely related to VT in patients with DCM. T-wave alternans is a useful noninvasive test for identifying high risk patients with DCM who have VT.     

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.     

Risk stratification of sudden cardiac death in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common hereditary cardiac condition and the leading cause of sudden cardiac death (SCD) in young adults. Given that SCD can be the first and most devastating clinical expression of HCM, identifying individuals at high risk is paramount. Determining an individual's risk for HCM-related SCD requires a thorough understanding of the recognized risk factors, of which there are seven established or 'major' and five 'possible'. Major risk factors can be identified by thoroughly reviewing a patient's personal medical history and noninvasive cardiovascular testing. The presence of major risk factors identify patients who are at high enough risk of SCD to warrant consideration of an implantable cardioverter-defibrillator; whereas the absence of any major risk factors provides considerable reassurance to both patient and physician. The risk of HCM-related SCD in patients with no major risk factors is, however, not zero. Possible risk factors gain importance in the presence of an isolated major risk factor. Here, we provide a contemporary review of established and possible risk factors for HCM-related SCD. We also examine microvolt T-wave alternans and cardiovascular MRI as emerging risk stratification tools that could further hone our ability to accurately identify the high-risk patient.     

Relation between microvolt-level T-wave alternans and cardiac sympathetic nervous system abnormality using iodine-123 metaiodobenzylguanidine imaging in patients with idiopathic dilated cardiomyopathy

We examined the relation between microvolt-level T-wave alternans and cardiac sympathetic nervous system abnormality using iodine-123 metaiodobenzylguanidine imaging in patients with idiopathic dilated cardiomyopathy. Our results strongly indicate that cardiac sympathetic denervation and accelerated sympathetic nervous activity play important roles in the presence of microvolt-level T-wave alternans in patients with idiopathic-dilated cardiomyopathy.     

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.     

肥厚型心肌病猝死危险因素分层

The natural history of hypertrophic cardiomyopathy(HCM)is extremely heterogeneous.Many patients remain asymptomatic throughout life,some develop severe symptoms of heart failure,but others die suddenly.often in the absence of previous symptoms and at a young age.Therefore,identification of those patients at high risk of sudden death represents a major clinical problem and has become an even greater challenge since the implantable cardioverter-defibrillator(ICD)has proved to be highly effective in preventing sudden death in HCM.Patients who have survived a cardiac arrest,or one or more episodes of sustained ventricular tachycardia,are considered to be at high risk and are candidates for an ICD.However,this patient subset represents a small proportion of the HCM population.The greatest difficulty concerns the identification of high risk patients who are candidates for primary prevention of sudden death with a prophylactic ICD.Decisions are based on generally accepted clinical markers which are associated with increased risk,including:family history of sudden death,extreme left ventricular(LV)wall thickness(≥30 mm),nonsustained ventricular tachycardia on Holter monitoring,unexplained(non-neurocardiogenic)syncope particularly in young patients,and hypotensive blood pressure response to exercise.Patients with end-stage HCM or a LV apical aneurysm represent important arrhythmogenic subsets also associated with substantially increased risk.Multiple or single strong risk markers are associated with increased sudden death risk and iustify consideration for a prophylactic ICD.     

Onset heart rate of microvolt-level T-wave alternans provides clinical and prognostic value in nonischemic dilated cardiomyopathy.

OBJECTIVES: This study was designed to determine the prognostic value of onset heart rate (OHR) in T-wave alternans (TWA) in patients with nonischemic dilated cardiomyopathy (DCM). BACKGROUND: One of the current major issues in DCM is to prevent sudden cardiac death (SCD). However, the value of the OHR of TWA as a prognostic indicator in DCM remains to be elucidated. METHODS: We prospectively investigated 104 patients with DCM undergoing TWA testing. The end point of this study was defined as SCD, documented sustained ventricular tachycardia/ventricular fibrillation. Relations between clinical parameters and subsequent outcome were evaluated. RESULTS: Forty-six patients presenting with TWA were assigned to one of the following two subgroups according to OHR for TWA of < or = 100 beats/min: group A (n = 24) with OHR < or = 100 beats/min and group B (n = 22) with 100 < OHR < or = 110 beats/min. T-wave alternans was negative in 37 patients (group C) and indeterminate in 21 patients. The follow-up result comprised 83 patients with determined TWA. During a follow-up duration of 21 +/- 14 months, there was a total of 12 arrhythmic events, nine of which included three SCDs in group A, two in group B and one in group C. The forward stepwise multivariate Cox hazard analysis revealed that TWA with an OHR < or = 100 beats/min and left ventricular ejection fraction were independent predictors of these arrhythmic events (p = 0.0001 and p = 0.0152, respectively). CONCLUSIONS: The OHR of TWA is of additional prognostic value in DCM.     

Microvolt T-wave alternans for risk stratification of cardiac events in ischemic cardiomyopathy: A meta-analysis

Background

The ability of microvolt T-wave alternans (MTWA) for risk stratification of cardiac events in patients with ischemic cardiomyopathy (ICM) has not been well established.

Methods

The authors systematically reviewed current literature and carried out a meta-analysis to determine the ability of MTWA to predict the outcome severity after ICM. Major endpoints include composite endpoint of cardiac mortality and severe arrhythmic events in primary prevention of patients with ICM, as well as all-cause mortality (cardiac death, and/or non-cardiac death).

Results

Seven trials were included by using MTWA for risk stratification of cardiac events in 3385 patients with ICM. All patients were distributed into two groups according to the results of MTWA tests: non-negative group included positive and indeterminate, and negative group. Compared with the negative group, non-negative group showed increased rates of cardiac mortality or severe arrhythmic events (RR = 1.65, 95%CrI = 1.32, 2.071), sudden cardiac death (SCD) (RR = 2.04 95%CrI = 1.11, 3.75), and all-cause mortality (RR = 2.11, 95%CrI = 1.60, 2.79). The funnel plot revealed that there might be bias within current publications. The fail-safe number of composite endpoint and all-cause mortality was 14.42 and 18.93, respectively (when P = 0.01). The fail-safe number of SCD was 1.07 (when P = 0.05), which may be caused by the small case number of included studies and some patients with ICD included.

Conclusions

The non-negative group of MTWA had a nearly double risk of severe outcomes compared with the negative group. Therefore, MTWA represents a potential useful tool for judging the severity of ICM.     

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.     

Risk stratification and prevention of sudden death in hypertrophic cardiomyopathy

Opinion statement Sudden cardiac death is the most devastating manifestation of hypertrophic cardiomyopathy (HCM) and often occurs in young and previously asymptomatic patients. Therefore, risk stratification for sudden death has a major role in the management of HCM and has acquired even greater relevance since the implantable cardioverter-defibrillator (ICD) has proved to be highly effective in preventing sudden death in this disease. The ICD is definitely indicated for secondary prevention of sudden death in patients with HCM who have survived a cardiac arrest with documented ventricular fibrillation, or experienced one or more episodes of sustained ventricular tachycardia. However, uncertainties persist regarding the precise selection of patients for primary prophylactic ICD implantation. A number of risk markers are used to assess the magnitude of risk, including family history of premature sudden death; extreme left ventricular (LV) hypertrophy (> 30 mm) in young patients; nonsustained ventricular tachycardia on Holter electrocardiographic recording; unexplained (not neurally mediated) syncope, particularly in young patients; and blood pressure decrease or inadequate increase during upright exercise. Multiple risk factors convey a definite increase in risk. However, a single risk factor such as family history of multiple sudden deaths, massive LV hypertrophy in a young patient, or frequent and/or prolonged runs of nonsustained ventricular tachycardia on Holter, may also justify consideration of a prophylactic ICD.     

Risk stratification and prevention of sudden death in hypertrophic cardiomyopathy

Sudden unexpected death, often occurring in young, asymptomatic patients, is the most devastating facet of the natural history of hypertrophic cardiomyopathy, and appears to be the consequence of primary ventricular tachyarrhythmias arising in an electrically unstable myocardial substrate characterized by disorganized cellular architecture, ischemia, cell death, and replacement scarring. Although precise identification of all hypertrophic cardiomyopathy patients at high risk for a catastrophic event is a clinical challenge, effective treatment strategies for the prevention of sudden death with the implantable cardioverter-defibrillator are now available.     

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.     

扩张型心肌病患者微伏级T波电交替检测分析

目的研究扩张型心肌病患者微伏级T波电交替(MTWA)的发生情况及与心率的关系。方法对31例扩张型心肌病患者用频谱法检测MTWA,分析扩张型心肌病MTWA的阳性率及不确定结果的原因,静息和运动时MTWA的发生情况,心率与交替压(Valt)的关系。结果①扩张型心肌病患者MTWA的阳性率为35.48%;②扩张型心肌病者,运动时的心率大于静息时,运动时各导联的Valt值大于静息时(P均<0.01)。静息时MTWA阳性2例,运动时MTWA阳性11例,运动时MTWA的阳性率高于静息时(35.48%vs 6.45%,P<0.01);③心率与综合导联Valt呈正相关,随心率的增加,Valt增大(r=0.984,P<0.01)。结论①扩张型心肌病患者MTWA阳性率高于正常人;②MTWA的发生与心率相关,随心率增快,Valt增大,MTWA阳性检出率增加。