Primary Prevention of Sudden Cardiac Death in Real Life: Differences With the Pivotal Studies and Their Consequences

The clinical efficacy of implantable cardioverter defibrillator (ICD) as method of primary prevention of sudden cardiac death (SCD) is well demonstrated today. Unfortunately, selection criteria of patients deemed at risk lacks of specificity. For asymptomatic patients with a left ventricular dysfunction (LVEF), current guidelines support implantation of ICD if the LVEF is ≤35%. This target population corresponds to the one studied in the Sudden Cardiac Death in HEart Failure Trial (SCD-HeFT). This trial is 10 years old. The proportion of patients with LVEF > 30% was low (17%) and the analysis of this subgroup showed no decrease in mortality (hazard ratio = 1.08 [0.57-2.07]). That is why the usefulness of ICD in this segment of the population remains a subject of controversy. Moreover, SCD-HeFT did not offer resynchronization therapy despite the fact that more than 40% of patients included had a QRS signal duration ≥120ms.

Conditions for implantation have since changed considerably. The "routine" nature of the implantation procedure and the desire to maximize patient's protection leads us to address for an implantation more easily. As for the resynchronization, it must be attempted in patients with severe heart failure, LVEF ≤35% and QRS sufficiently prolonged.

This suggests that the implanted population is very different nowadays from those from the pivotal studies in terms of mean LVEF and implanted material. However, these two factors are significantly correlated with the risk of SCD... Therefore, the analysis was done on samples of patients who received ICD in primary prevention setting. This study focused on the effect of resynchronization and LVEF at implantation and the subsequent outcome. The results were broadly compared with those of SCD-HeFT.