Reevaluating the long-term efficacy of primary prophylactic implantable cardioverter-defibrillators for sudden cardiac death in the era of advanced heart failure treatment

Sudden cardiac death (SCD) due to fatal arrhythmias poses a significant risk to high-risk patients, and implantable cardioverter-defibrillators (ICDs) are widely used for both primary and secondary prevention of SCD. Current guidelines for the use of ICDs as primary prophylaxis, both in Japan and Western countries, are largely based on randomized controlled trials conducted around the year 2000. However, with advances in heart failure treatments and other medical interventions, there is increasing debate over the need to reassess the validity of these guidelines. Furthermore, the long-term efficacy of primary prophylactic ICDs, as well as the optimal stratification of high-risk patients, remain critical areas for further research.

The aim of this study was to evaluate the long-term efficacy of ICDs in primary prophylaxis and to identify the risk factors for SCD in patients with primary prophylactic ICD.

We retrospectively analyzed the database of our ICD clinic. All subjects had been implanted with an ICD from January 2001 to December 2015. We divided them into the primary prophylactic and secondary prophylactic groups. Clinical outcomes were defined as the first event which was a composite of all-cause death or appropriate ICD therapy, including anti-tachycardia pacing or shock therapy.

A total of consecutive 369 Japanese patients with an ICD were enrolled in this study (age 60±13 years, male 81%). The mean follow-up period was 69 ± 32 months. Kaplan-Meier analysis showed no significant difference in the composite endpoint between the primary prophylactic and secondary prophylactic groups (31% vs. 37%, p=0.26) (Figure A). Multivariate analysis revealed that reduced LVEF (≤30%) was independently associated with the composite endpoint in the primary prophylactic group (Table B).

The primary prophylactic effect of ICD implantation was comparable to that of secondary prophylaxis, and appropriate ICD therapies and mortality are not rare. Furthermore, in patients with an ICD receiving primary prophylaxis, reduced cardiac function was significantly correlated with these events.