SCD in patients with cardiomyopathy: use of microvolt T-wave alternans and other noninvasive tests for risk stratification and prevention of SCD.

Based on current guidelines, most electrophysiologists today are implanting cardioverter-defibrillators (ICDs) using a low left ventricular ejection fraction alone as the sole stratifier for the risk of sudden cardiac death. However, left ventricular ejection fraction is a better marker of total mortality than sudden death. As a result, this strategy is flawed because it exposes many patients to the risk and cost of ICD therapy without its benefits. Primary prevention trials based on this strategy show that the rate of appropriate ICD shocks is only 5% to 10% per year. We believe that the effectiveness of ICD therapy can be improved by the use, in addition to ejection fraction, of one or more of the noninvasive tests, which are reviewed in this article. Such tests are more adequate to evaluate the arrhythmogenic substrate of the patient than the left ventricular ejection fraction alone. Whether any of these tests can help us identify the patients at the lowest risk of sudden death, who could safely avoid ICD implant, remains to be determined.