What is the clinical evidence from this study?

Study design: RCT. Population: Heart failure and systolic dysfunction (n=490). Intervention: Microvolt T-wave alternans (TWA) positive vs. TWA negative. Primary outcome: first occurrence of sudden cardiac death, sustained ventricular tachycardia/fibrillation, or appropriate implantable cardioverter defibrillator discharge (HR 1.24, 95% CI 0.60 to 2.59, p=0.56).

October 28, 2008Open Access

Role of Microvolt T-Wave Alternans in Assessment of Arrhythmia Vulnerability Among Patients With Heart Failure and Systolic Dysfunction

Key Result

Microvolt T-wave alternans testing did not predict arrhythmic events or mortality among patients with heart failure and systolic dysfunction (HR 1.24; 95% CI 0.60-2.59; P=0.56).

Study Design

Type

RCT (n=490)

Blinding

blinded readers

Randomization

randomized

Multicenter

Yes

Structured PICO

Does microvolt T-wave alternans testing predict arrhythmic events or mortality in patients with heart failure and systolic dysfunction?

Population

490 patients with heart failure and left ventricular systolic dysfunction from 37 clinical sites (SCD-HeFT substudy)

Intervention

Microvolt T-wave alternans (TWA) testing (positive or nonnegative)

Comparator

TWA-negative patients

Outcome

Composite of first occurrence of sudden cardiac death, sustained ventricular tachycardia/fibrillation, or appropriate implantable cardioverter defibrillator dischargecomposite

Microvolt T-wave alternans testing does not predict arrhythmic events or mortality in patients with heart failure and left ventricular systolic dysfunction, suggesting it is not useful for guiding ICD therapy in this population.

Main Result

Effect estimate: HR 1.24 (95% CI 0.60 to 2.59)

p-value: p=0.56

Limitations

A small reduction in events (20% to 25%) among TWA-negative patients cannot be excluded given the sample size of this study.

Abstract

BACKGROUND: Sudden cardiac death remains a leading cause of mortality despite advances in medical treatment for the prevention of ischemic heart disease and heart failure. Recent studies showed a benefit of implantable cardioverter defibrillator implantation, but appropriate shocks for ventricular tachyarrhythmias were noted only in a minority of patients during 4 to 5 years of follow-up. Accordingly, better risk stratification is needed to optimize patient selection. In this regard, microvolt T-wave alternans (TWA) has emerged as a potentially useful measure of arrhythmia vulnerability, but it has not been evaluated previously in a prospective, randomized trial of implantable cardioverter defibrillator therapy. METHODS AND RESULTS: This investigation was a prospective substudy of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) that included 490 patients at 37 clinical sites. TWA tests were classified by blinded readers as positive (37%), negative (22%), or indeterminate (41%) by standard criteria. The composite primary end point was the first occurrence of any of the following events: sudden cardiac death, sustained ventricular tachycardia/fibrillation, or appropriate implantable cardioverter defibrillator discharge. During a median follow-up of 30 months, no significant differences in event rates were found between TWA-positive or -negative patients (hazard ratio 1.24, 95% confidence interval 0.60 to 2.59, P=0.56) or TWA-negative and nonnegative (positive and indeterminate) subjects (hazard ratio 1.28, 95% confidence interval 0.65 to 2.53, P=0.46). Similar results were obtained with the inclusion or exclusion of patients randomized to amiodarone in the analyses. CONCLUSIONS: TWA testing did not predict arrhythmic events or mortality in SCD-HeFT, although a small reduction in events (20% to 25%) among TWA-negative patients cannot be excluded given the sample size of this study. Accordingly, these results suggest that TWA is not useful as an aid in clinical decision making on implantable cardioverter defibrillator therapy among patients with heart failure and left ventricular systolic dysfunction.