Although clinical trials evaluating therapy with implantable cardioverter defibrillators (ICD) have had clear limitations, there are few interventions in which multiple trial settings over a long period have consistently produced a 20% to 30% reduction in total mortality in patients with left ventricular dysfunction. Substantial differences between the Guidelines on ICD implantation have resulted and the number of patients actually implanted following these recommendations remains relatively low. As well as this, different reasons have been proposed to explain why randomized trials of ICD versus control subjects implanted early after myocardial infarction do not show survival benefit. Moreover, many factors in addition to ejection fraction (EF) do influence the prognosis of patients with coronary disease. However, there are few tools to use this information to guide clinical decisions. Recent years have seen an ongoing debate on the further risk stratification of patients who will benefit most from ICD implantation and a combination of a few readily available clinical variables indicating advanced disease and comorbid conditions identifies ICD patients at high risk. In addition, the role of these devices in patients with nonischemic cardiomyopathies, in older patients and females, for prevention of sudden cardiac death (SCD), has long been debated. This review aims to summarize these criticisms and to refine the current indications of ICD implantation in patients with moderate-severe left ventricular dysfunction.
Keywords: Guidelines, implantable cardioverter defibrillator, left ventricular dysfunction, primary prevention, secondary prevention, risk score, sudden cardiac death.