Sample Size: Hazard rates have been estimated for the placebo and ICD groups using subjects from a variety of databases (including the Echos database and the publication of Definite). Assuming a 24-month enrollment period and a 36 month follow-up period (resulting in a 5-year study with a minimum treatment period of 3 years and approximately a median survival time of 60 months), a total of 812 subjects will provide a 80% power with a 2-sided significance level of 5% for detecting a reduction in hazard of 25%.