Microvolt T-wave alternans monitoring in a patient with levofloxacin-induced Torsade de Pointes

We present the case of a 62-year-old woman with levofloxacin-induced Torsade de Pointes, in whom microvolt T-wave alternans was measured during acute hospitalization and when QT interval was dynamically changing, illustrating a means for monitoring proarrhythmia.     

T-wave alternans associated with heart failure and hypomagnesemia in alcoholic cardiomyopathy.

Marked T wave abnormality developed in a patient with alcoholic cardiomyopathy. The T negativity was of giant size and occurred in an alternating sequence in the presence of sinus rhythm. This change was rapidly transient, disappearing in 3 days. The complete electrocardiographic recovery was temporally related to successful treatment of severe heart failure, normalization of initially low serum magnesium level, and abolition of recurrent ventricular fibrillation.     

Microvolt T-wave alternans for the risk stratification of ventricular tachyarrhythmic events: a meta-analysis

OBJECTIVES: The objective of this study was to perform a meta-analysis of the predictive value of microvolt T-wave alternans (MTWA) testing for arrhythmic events in a wide variety of populations. BACKGROUND: Previous studies describing the use of MTWA as a predictor of ventricular tachyarrhythmic events have been limited by small sample sizes and disparate populations. METHODS: Prospective studies of the predictive value of exercise-induced MTWA published between January 1990 and December 2004 were retrieved. Data from each article were abstracted independently by two authors using a standardized protocol. Summary estimates of the predictive value of MTWA were made using a random-effects model. RESULTS: Data were accumulated from 19 studies (2,608 subjects) across a wide range of populations. Overall, the positive predictive value of MTWA for arrhythmic events was 19.3% at an average of 21 months' follow-up (95% confidence interval [CI] 17.7% to 21.0%), the negative predictive value was 97.2% (95% CI 96.5% to 97.9%), and the univariate relative risk of an arrhythmic event was 3.77 (95% CI 2.39 to 5.95). There was no difference in predictive value between ischemic and nonischemic heart failure subgroups. The positive predictive value varied depending on the population of patients studied (p < 0.0001). CONCLUSIONS: Microvolt T-wave alternans testing has significant value for the prediction of ventricular tachyarrhythmic events; however, there are significant limitations to its use. The predictive value of MTWA varies significantly depending on the population studied. Careful standardization is needed for what constitutes abnormal MTWA. The incremental prognostic value of MTWA when used with other methods of risk stratification is unclear.     

Microvolt T-wave alternans in early repolarization syndrome associated with ventricular arrhythmias: A case report

Despite early repolarization (ER) syndrome being usually considered benign, its association with severe/malignant ventricular arrhythmias (VA) was also reported. Microvolt T-wave alternans (MTWA) is an electrocardiographic marker for the development of VA, but its role in ER syndrome remains unknown. A 90-second 6-lead electrocardiogram from an ER syndrome patient, acquired with the Kardia recorder, was analyzed by the enhanced adaptive matched filter for MTWA quantification. On average, MTWA was 50 μV, higher than what was previously observed on healthy subjects using the same method. In our ER syndrome patient, MTWA plays a potential role in VA development in ER syndrome.     

Biventricular pacing does not affect microvolt T-wave alternans in heart failure patients

BACKGROUND: Microvolt T-wave alternans (MTWA) is a valuable tool for stratification of patients at risk for sudden death and has recently been approved for this purpose by Medicare. Although right atrial (RA) pacing has been applied for MTWA testing, the effects of other pacing modalities on MTWA have not been systematically studied. Accordingly, it is unknown whether biventricular (BiV) pacing might influence MTWA test results. OBJECTIVE: This study sought to investigate effects of BiV pacing in comparison with other pacing modalities. METHODS: Congestive heart failure patients (n = 30) receiving cardiac resynchronization therapy were included, and a systematic step-up pacing protocol was performed via the implanted cardioverter-defibrillator. RESULTS: Of the overall 120 MTWA tests performed, 67 (56%) were nonnegative. Nonnegative MTWA test results were observed in 18 patients (60%) during RA stimulation, whereas 17 (57%), 15 (50%), and 17 test results (57%) were nonnegative during right ventricular (RV), left ventricular (LV), and BiV pacing, respectively. Seven (23%) patients were MTWA negative for all pacing sites. Results of MTWA assessment during RA pacing were concordant with results obtained with RV pacing in 25 (83%) patients (kappa = 0.66, P = .0003), to LV pacing in 21 (70%) patients (kappa = 0.4, P = .025), and to BiV pacing in 25 (83%) patients (kappa = 0.66, P = .0003). Positive and negative predictive values of nonnegative MTWA test results obtained during RA pacing for a similar result obtained with RV pacing were 88% and 76%. Respective values were similar for other pacing modalities (80% and 60% for LV; 88% and 76% for BiV pacing). CONCLUSION: There is a high level of concordance between MTWA test results obtained during RA pacing and other pacing modalities, and MTWA assessment seems not to be influenced by BiV stimulation in congestive heart failure patients. In general, BiV pacing does not seem to affect an arrhythmogenic substrate as detected by MTWA testing.     

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.     

Quantitative assessment of microvolt T-wave alternans in patients with congestive heart failure

INTRODUCTION: T-wave alternans has been shown to be linked to the genesis of ventricular tachyarrhythmias. Currently, only qualitative assessment of microvolt T-wave alternans (MTWA) is recommended in clinical practise. Whether quantitative assessment of MTWA yields complementary information is unknown. METHODS AND RESULTS: Noninvasive MTWA determination was performed in 204 consecutive patients with ischemic or nonischemic cardiomyopathy. Of those, 100 tested MTWA positive. In these recordings, MTWA magnitude was quantitatively assessed (alternans voltage, V(alt)). Patients were followed for a mean of 17 months. Ventricular tachyarrhythmic events constituted the study endpoint. Patients with nonischemic cardiomyopathy had a higher V(alt) than patients with ischemic cardiomyopathy (10.3 +/- 9.2 [median 7.2] vs 6.2 +/- 3.2 [median 4.6] microV; P = 0.007). The number of MTWA-positive ECG leads was also higher in patients nonischemic cardiomyopathy (7.3 +/- 2.4 [median 8] vs 6.0 +/- 2.5 [median 6]; P = 0.016). Patients who suffered an arrhythmic event during follow-up had higher MTWA voltages (10.8 +/- 10.0 [median 8.8] vs 7.4 +/- 5.7 [median 6.4] microV; P = 0.05) a higher number of MTWA-positive ECG leads (7.6 +/- 2.4 [median 8] vs 6.4 +/- 2.5 [median 6]; P = 0.05) compared to patients with an uncomplicated course. CONCLUSION: Patients with nonischemic cardiomyopathy and patients with tachyarrhythmic complications have more extensive MTWA possibly reflecting more extensive myocardial damage and a higher arrhythmia propensity.     

Predictive value of T-wave alternans for arrhythmic events in patients with congestive heart failure

Measurement of microvolt level T-wave alternans in the surface electrocardiogram is a novel way to assess the risk of ventricular arrhythmias. Seven tests of arrhythmic risk, including T-wave alternans, were undertaken in 107 consecutive patients with congestive heart failure and no history of sustained ventricular arrhythmias; the patients were followed up for arrhythmic events during the next 18 months. Of the patients with events, 11 had positive and two indeterminate T-wave alternans results; there were no arrhythmic events among patients with negative T-wave alternans results. Of the seven tests, only T-wave alternans was a significant (p=0.0036) and independent predictor of arrhythmic events.     

Microvolt T-wave alternans identifies patients with ischemic cardiomyopathy who benefit from implantable cardioverter-defibrillator therapy.

OBJECTIVES: This study sought to assess whether implantable cardioverter-defibrillators (ICDs) have different mortality benefits among patients with ischemic cardiomyopathy who screen negative and non-negative (positive and indeterminate) for microvolt T-wave alternans (MTWA). BACKGROUND: Microvolt T-wave alternans has been proposed as an effective tool for risk stratification. However, no studies have examined whether ICD benefits differ by MTWA group. METHODS: We developed a prospective cohort of 768 patients with ischemic cardiomyopathy (left ventricular ejection fraction < or =35%) and no prior sustained ventricular arrhythmia, of which 392 (51%) received ICDs. The mean follow-up time was 27 +/- 12 months. Propensity scores for ICD implantation based on the variables most likely to influence defibrillator implantation were developed for each MTWA cohort. Multivariable Cox analyses that controlled for propensity score, demographics, and clinical variables evaluated the degree to which ICDs decreased mortality risk for each MTWA group. RESULTS: We identified 514 (67%) patients with a non-negative MTWA test result. After multivariable adjustment, ICDs were associated with lower all-cause mortality in MTWA-non-negative patients (hazard ratio [HR] 0.45, 95% confidence interval [CI] 0.27 to 0.76, p = 0.003) but not in MTWA-negative patients (HR 0.85, 95% CI 0.33 to 2.20, p = 0.73) (for interaction, p = 0.04), with the mortality benefit in MTWA-non-negative patients largely mediated through arrhythmic mortality reduction (HR 0.30, 95% CI 0.13 to 0.68, p = 0.004). The number needed to treat with an ICD for 2 years to save 1 life was 9 among MTWA-non-negative patients and 76 among MTWA-negative patients. CONCLUSIONS: In patients with ischemic cardiomyopathy and no prior history of ventricular arrhythmia, mortality reduction with ICD implantation differs by MTWA status, with implications for risk stratification and health policy.