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. 2012 Aug;9(8):1256-64.e2.
doi: 10.1016/j.hrthm.2012.03.014. Epub 2012 Mar 8.

Clinical utility of microvolt T-wave alternans testing in identifying patients at high or low risk of sudden cardiac death

Faisal M Merchant  1 , Takanori Ikeda, Roberto F E Pedretti, Jorge A Salerno-Uriarte, Theodore Chow, Paul S Chan, Cheryl Bartone, Stefan H Hohnloser, Richard J Cohen, Antonis A Armoundas
Affiliations

Clinical utility of microvolt T-wave alternans testing in identifying patients at high or low risk of sudden cardiac death

Faisal M Merchant et al. Heart Rhythm. 2012 Aug.

Abstract

Background: Previous studies have demonstrated that microvolt T-wave alternans (MTWA) testing is a robust predictor of ventricular tachyarrhythmias and sudden cardiac death (SCD) in at-risk patients. However, recent studies have suggested that MTWA testing is not as good a predictor of "appropriate" implantable cardioverter-defibrillator (ICD) therapy as it is a predictor of SCD in patients without ICDs.

Objective: To evaluate the utility of MTWA testing for SCD risk stratification in patients without ICDs.

Methods: Patient-level data were obtained from 5 prospective studies of MTWA testing in patients with no history of ventricular arrhythmia or SCD. In these studies, ICDs were implanted in only a minority of patients and patients with ICDs were excluded from the analysis. We conducted a pooled analysis and examined the 2-year risk for SCD based on the MTWA test result.

Results: The pooled cohort included 2883 patients. MTWA testing was positive in 856 (30%), negative in 1627 (56%), and indeterminate in 400 (14%) patients. Among patients with a left ventricular ejection fraction (LVEF) of ≤35%, annual SCD event rates were 4.0%, 0.9%, and 4.6% among groups with MTWA positive, negative, and indeterminate test results. The SCD rate was significantly lower among patients with a negative MTWA test result than in patients with either positive or indeterminate MTWA test results (P <.001 for both comparisons). In patients with an LVEF of >35%, annual SCD event rates were 3.0%, 0.3%, and 0.3% among the groups with MTWA positive, negative, and indeterminate test results. The SCD rate associated with a positive MTWA test result was significantly higher than that associated with either negative (P <.001) or indeterminate MTWA test results (P = .003).

Conclusions: In patients without ICDs, MTWA testing is a powerful predictor of SCD. Among patients with an LVEF of ≤35%, a negative MTWA test result is associated with a low risk for SCD. Conversely, among patients with an LVEF of >35%, a positive MTWA test result identifies patients at significantly heightened SCD risk. These findings may have important implications for refining primary prevention ICD treatment algorithms.

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Conflict of interest statement

Conflicts of interest: Theodore Chow – Medtronic Inc., significant

Richard J. Cohen – Cambridge Heart Inc., significant

No other conflicts reported

Figures

Figure 1
Figure 1. MTWA test results across the entire pooled cohort including sub-classification based on cause of indeterminacy
Figure 2
Figure 2. Kaplan-Meier event-free survival curves for the primary endpoint of arrhythmic mortality/sudden cardiac death stratified by MTWA test result for the entire pooled cohort
Patients with positive or indeterminate MTWA test result demonstrate significantly lower event-free survival compared to patients with negative MTWA test results. There is no significant difference in event-free survival between patients with positive and indeterminate test results. All p values are generated by the log-rank test.
Figure 3
Figure 3. Kaplan-Meier event-free survival curves for the primary endpoint of arrhythmic mortality/sudden cardiac death stratified by MTWA test result among patients with LVEF ≤ 35%
Similar to the pattern observed in the whole cohort, event-free survival is significantly lower among patients with positive or indeterminate MTWA test results, whereas there is no significant difference in survival between the positive and indeterminate groups. All p values are generated by the log-rank test.
Figure 4
Figure 4. Kaplan-Meier event-free survival curves for the primary endpoint of arrhythmic mortality/sudden cardiac death stratified by MTWA test result among patients with LVEF > 35%
Event-free survival is significantly lower in the MTWA positive group than either the negative or indeterminate groups. In contrast, there is no significant difference in event-free survival between the negative and indeterminate groups. All p values are generated by the log-rank test.
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