Trial: Microvolt T-Wave Alternans Identifies Patients With Ischemic Cardiomyopathy Who Benefit From Implantable Cardioverter-Defibrillator Therapy

Authors:  Theodore Chow, Dean J. Kereiakes, Cheryl Bartone, Terri Booth, Edward J. Schloss, Theodore Waller, Eugene Chung, Santosh Menon, Brahmajee K. Nallamothu, Paul S. Chan

Reference:  J Am Coll Cardiol 2007;49:58,   PMID:17207722

Purpose:  To assess whether implantable cardioverter-defibrillators (ICDs) have different mortality benefits in patients with ischemic cardiomyopathy who screen negative compared to those with non-negative (positive and indeterminate) microvolt T-wave alternans (MTWA) tests.

Number of Patients:  768

Number of Centers:  7 outpatient heart failure clinics

Design:  Prospective uncontrolled observational registry study of patients with ischemic cardiomyopathy who underwent MTWA analysis with or without EP testing who had an LVEF < 0.35 and no prior history of sustained ventricular arrhythmia.  Propensity analysis of ICD compared to no ICD groups was used to adjust proportional hazards analysis of mortality, arrhythmic and nonarrhythmic death, and appropriate ICD shocks or death. After multivariable adjustment, ICDs were associated with lower mortality in MTWA-non-negative patients (hazard ratio 0.45, 95% confidence interval 0.27 to 0.76) but not in MTWA-negative patients (HR 0.85, 95% CI 0.33 to 2.20).  Findings were similar for arrhythmic death.

Authors Conclusion:   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.

Comment:  The findings support the potential utility of MTWA to identify a low risk group of patients with coronary artery disease and depressed ventricular function  who are less likely to benefit from a prophylactic ICD.  No propensity multivariable analysis can adjust for all potential factors involved in the decision to implant or withhold an ICD in these patients.  Thus, randomized trials are required to address this clinical application.

Summary crafted by William Stevenson, MD, FHRS