Prognostic implication of redefining indeterminate microvolt T-wave alternans studies as abnormal or normal
Paul S Chan1, Cheryl Bartone, Terri Booth
1Division of Cardiology, University of Michigan, Ann Arbor, MI, USA. paulchan@umich.edu
Background:
Prior studies involving microvolt T-wave alternans (MTWA) have combined positive and indeterminate studies into a high-risk "nonnegative" category. However, studies examining the prognostic utility of specific reasons for an indeterminate study are limited. The objective of this study was to assess if patients have differences in survival prognosis based on the reasons for an indeterminate MTWA result.
Methods:
We enrolled 768 consecutive patients with ischemic cardiomyopathy (left ventricular ejection fraction < or = 35%) and no prior history of sustained ventricular arrhythmia. Microvolt T-wave alternans studies were classified as positive, negative, or indeterminate. Prespecified multivariable Cox regression analyses, stratified by implantable cardioverter/defibrillator status, were used to determine whether there was heterogeneity in survival prognosis among the individual reasons for an indeterminate study.
Results:
We identified 159 (21%) patients with an indeterminate MTWA test. Reasons for indeterminate studies included frequent ectopy (46%), inability to reach adequate heart rate (IHR) (32%), unsustained alternans (9%), and excessive noise (13%). After multivariable adjustment, indeterminate studies due to ectopy/IHR were associated with a significantly higher risk for all-cause (stratified hazard ratio [HR] 4.63, 95% CI 1.32-16.18, P = .02) and arrhythmic mortality (stratified HR 17.57, 95% CI 1.62-190.50, P = .02) but not for nonarrhythmic mortality (stratified HR 1.30, 95% CI 0.27-6.29, P = .75). The prognostic utility of MTWA testing was improved when indeterminate studies were reclassified as abnormal (positive + ectopy/IHR) or normal (negative + unsustained alternans), with only 3% of all studies thereafter remaining inconclusive (noise).
Conclusion:
Patients with indeterminate MTWA studies exhibit heterogeneity in survival prognosis. Reclassifying indeterminate studies as abnormal or normal improves the predictive power of MTWA.
Insights
Indeterminate microvolt T-wave alternans (MTWA) test results in patients with ischemic cardiomyopathy show varied survival risks. Reclassifying these results improves the prognostic accuracy of MTWA testing for mortality risk.
Area of Science:
- Cardiology
- Electrophysiology
- Clinical Risk Stratification
Background:
- Microvolt T-wave alternans (MTWA) testing is used to assess arrhythmia risk.
- Prior studies often grouped indeterminate MTWA results as high-risk.
- Limited data exists on the prognostic impact of specific reasons for indeterminate MTWA results.
Purpose of the Study:
- To evaluate survival prognosis differences among patients with specific reasons for an indeterminate MTWA result.
- To determine if reclassifying indeterminate MTWA results improves predictive accuracy.
Main Methods:
- 768 patients with ischemic cardiomyopathy and LVEF ≤ 35% were enrolled.
- MTWA tests were categorized as positive, negative, or indeterminate (due to ectopy, inadequate heart rate, unsustained alternans, or noise).
- Multivariable Cox regression analyses assessed mortality risk based on indeterminate reasons.
Main Results:
- 21% of patients had indeterminate MTWA results.
- Indeterminate results due to ectopy or inadequate heart rate were linked to significantly higher all-cause and arrhythmic mortality.
- Reclassifying indeterminate results as abnormal (positive + ectopy/IHR) or normal (negative + unsustained alternans) enhanced MTWA's predictive power.
Conclusions:
- Heterogeneity exists in survival prognosis among patients with indeterminate MTWA studies.
- Reclassifying indeterminate MTWA results improves the overall predictive utility of the test for risk stratification.
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