Lessons learned from neutral ICD trials

Multiple prospective randomized trials with implantable cardioverter defibrillators (ICDs) over the past decade have convincingly established the efficacy of ICD therapy in reducing all-cause mortality, by significantly reducing sudden cardiac death. Nevertheless, four trials have failed to show improved survival. Analysing these, in comparison with the positive trials, provides important information concerning the type of patients not likely to receive benefit from ICDs: (i) those with relatively low mortality (< or = 18% within 2 years of follow-up; (ii) those whose mechanism of death is predominantly non-arrhythmic; (iii) patients early (within 6 weeks) after infarction.